A Wide-Input–Wide-Output (WIWO)

DC–DC Converter

Abstract:

This paper presents a new wide-input–wide-output dc–dc converter, which is

an integration of buck and boost converters via a tapped inductor. Coherent

transition between step-down and step-up modes is achieved by a proper control

scheme. This paper presents theoretical concepts and experimental results.

Block Diagram:

Circuit Diagram:

Existing System:

In applications where both step-up and step-down conversion ratios are required,

the buck–boost and Cuk converters can be used. Simplicity and robustness are

among the advantages of the buck–boost converter. However, the pulsating input

and output currents cause high conduction losses, and thus, impair the efficiency of

buck–boost. Furthermore, the buck–boost converter uses the inductor to store the

energy from the input source, and then, release the stored energy to the output. For

this reason, the magnetic components of buck– boost are subjected to a significant

stress. These disadvantages limit the applications of the buck–boost converter

mainly to low power level.

Proposed System:

This paper proposes a new wide-input–wide-output (WIWO) dc–dc converter. The

new converter is an integration of buck and boost converters via a tapped inductor.

By applying proper control to the two active switches, the converter exhibits both

buck and boost features. The basic switching converters with tapped inductors, and

offers motivation and guidelines to the synthesis of the new switching converter.

The operating principle is described in detail providing the steady-state (dc) and

dynamic (ac) models as well.

Literature Survey:

The basic buck and boost converters can be transformed into a number of new

topologies by bringing in the tapped inductor. The proposed tapped-inductor buck-

derived converters are shown. With their corresponding voltage conversion ratios.

The proposed tapped-inductor boost derived topologies and their corresponding

voltage conversion ratios. Here, D is the duty ratio of switch S, M is the voltage

conversion ratio, and n is the turn ratio of the tapped inductors, which is defined as

n = n2: n1. As the turn ratio n tends to infinity, the conversion ratio of the buck-

derived converters approach the characteristic of a basic buck topology. On the

other hand, as the turn ratio n goes to zero, the conversion ratio of the boost-

derived converters approach the characteristic of a basic boost topology. Inspection

of the conversion ratio plots reveals that the proposed buck-derived converter

achieves wider voltage step-down than a basic buck converter. Also, by examining

it becomes evident that the suggested boost-derived converter attains a wider

voltage step-up than a basic boost converter. The idea proposed here is that these

two topologies may be combined to form a new two-switch topology, with an

extended conversion range. Same conclusion can be reached comparing the

converters given. The proposed WIWO range converter topology is described in

the next section.

A Family of Buck-Type DC-DC Converters with Autotransformers

This paper introduces a family of buck-type DC-DC converters with

autotransformers, including forward, push-pull, half-bridge, and full-bridge

topologies. Compared with an isolated transformer, the autotransformer has a

simpler winding structure, and it only needs to transfer part of the input power,

resulting in a smaller secondary winding current. Analysis shows that the

autotransformer can also help to reduce the voltage stress and current ratings of

power devices in the DC-DC converters. For some applications, a simple lossless

passive clamp circuit can be implemented to solve the transformer leakage

problems, and the gate drive is significantly improved with a simple self-adaptive

dead-time-controlled bootstrap gate driver. Simulation and experimental results

show that the proposed topologies are very suitable for high-frequency

applications. Autotransformers are widely used in high-power AC systems when

there is no galvanic isolation requirement [1~4]. Compared with an isolated

transformer, which has separated primary and secondary windings, the

autotransformer uses part of the primary winding as the secondary winding in a

tapped version (for step-down conversion). Fig. 1 shows the difference between an

isolated transformer and an autotransformer. The isolated transformer has a

primary winding with np turns and a secondary winding with ns turns. The

autotransformer has only one winding with np turns. The output shares part of the

winding with an (np-ns): ns tapped connection. Both transformers can transfer the

same power as long as their turn’s ratios are the same:

n = np / ns. (1)

But in the autotransformer, the input current goes directly to the output, reducing

the secondary winding current. The secondary winding current is

Is= ip.n (2)

In the isolated transformer, and

Is = ip.n.(n −1) (3)

In the autotransformer. Here, Ip is the transformer primary winding current.

Design & simulation of buck-boost converter modulation technique for solar

application

This paper, a single-phase single stage transformer less photovoltaic (PV) inverter

for residential application is presented. The inverter is derived from a buck-boost

converter along with a line frequency unfolding circuit which will be used to

supply the generated photovoltaic energy to load (Grid/Stand Alone). Interfacing a

solar inverter module with the load involves three major tasks. One is efficiency,

the second is to inject a sinusoidal quantity into load and the third is the power

quality. Since the inverter is connected to the grid, the norms given by the utility

companies must be obeyed. Due to its novel operating modes, high quality

(without filter) and efficiency can be achieved, because there is only one switch in

buck-boost converter operating at high frequency and rest of the switches of

unfolding circuit is operated at fundamental frequency only. This paper contains

theoretical analysis and simulation result of this buck-boost converter based

inverter for off grid. This shows the comparison of the norms with the simulation

result of the product in terms of power quality and efficiency.

Buck-Boost Converter.

The average output voltage Va is less than or greater than the input voltage Vs of

converter, it will be decided by value of k and its voltage equation is written as

under. Output voltage of this converter is having opposite polarity than the input

voltage hence it also known as Inverting converter.

A. Boost Mode

When the PV panel’s voltage is lower than the instantaneous reference voltage, it

will operate in boost mode, in which S will be switched ON and OFF with the duty

cycle 0.5<K<1

B. Buck Mode

When the PV panel’s voltage is higher than the instantaneous reference voltage, it

will operate in buck mode, in which S will be switched ON and OFF with the duty

cycle 0<K<0.5

Operation mode

High efficiency high step-up DC/DC converters – a review

The renewable energy sources such as PV modules, fuel cells or energy storage

devices such as super capacitors or batteries deliver output voltage at the range of

around 12 to 70 VDC. In order to connect them to the grid the voltage level should

be adjusted according to the electrical network standards in the countries. First of

all the voltage should be stepped up to sufficient level at which the DC/AC

conversion can be performed to AC mains voltage requirements. Overall

performance of the renewable energy system is then affected by the efficiency of

step-up DC/DC converters, which are the key parts in the system power chain. This

review is focused on high efficiency step-up DC/DC converters with high voltage

gain. The differentiation is based on the presence or lack of galvanic isolation. A

comparison and discussion of different DC/DC step-up topologies will be

performed across number of parameters and presented in this paper.

Single cell boost converter

Interleaved boost converters. The simplicity is major advantage of that topology.

Since interleaved boost converter cells share the input current the input current

ripples are small which increases the life of PV modules. Moreover single cell

feeds only the fraction of total input current and the duty cycle of a single switch

does not exceed 0.25. Smaller inductors can be used along with the power rating of

switches and diodes decrease. When driving sequentially switches are switched on

and off one by one enabling low output voltage ripples. The diodes reverse

recovery current flow when the diodes are switched off cause’s electromagnetic

noise (EMI). To overcome that problem discontinuous inductor current driving

mode should be used. In the other hand continuous inductor current mode

demonstrates lower input current ripples as well as lower switching losses. The

main disadvantage of that topology is relatively low voltage gain, usually not

higher than 2. To improve voltage gain interleaved structures can be mixed with

transformers or the inductors can be coupled.

Soft switching boost converters. This high performance converter has slightly

improved voltage gain in comparison to single switch boost converter. It operates

in ZVS (Zero Voltage Switching) mode dramatically reducing switching losses

thus achieving better efficiency. The driving sequence is bit more complex, but

both switches operate at the same ground potential thus additional separation at

driver side is needless. The disadvantage of that topology is the complexity of the

circuit, because of 5 more components addition including a switch and an extra

inductor.

Soft switching boost converter

Coupled inductor structures. Coupled inductor can serve as a transformer to

enlarge the voltage gain in non isolated DC/DC converters in proportion to

winding turns ratio (Fig. 7). These converters can easily achieve high voltage gain

using low RDS−on switches working at relatively low level of voltage. The switch

driving scheme is simple as the converter usually utilizes single switch. Common

mode conducted EMI is reduced due to balanced switching. To reduce passive

component size coupled inductors can be integrated into single magnetic core

Coupled inductor step-up converter

Non isolation Soft-Switching Buck Converter with Tapped-Inductor for

Wide-Input Extreme Step-Down Applications

In this paper, a new zero-voltage switching (ZVS) buck converter with a tapped

inductor (TI) is proposed. This converter improves the conventional tapped

inductor critical conduction mode buck converters that have the ZVS operation

range determined by the TI turn ratios. It includes another soft switching range

extension method, the current injection method, which gives an additional design

freedom for the selection of the turn-ratios and enables the optimal design of the

winding ratio of the TI so that the efficiency may be maximized. This soft-

switching buck converter is suitable for wide input range step-down applications.

The principle of the proposed scheme, analysis of the operation, and design

guidelines are included. Experimental results of the 100-W prototype dc–dc

converter are given for hardware verification also. Finally, based on the proposed

soft-switching technique, a new soft-switching topology family is derived.

Conventional TI buck converter.

Introduction

The buck, boost, buck–boost, and Cuk converters are the four basic dc–dc non

isolating converters that have found wide applications in industry. The buck

converter can step down the dc voltage, whereas the boost converter is capable to

perform a step-up function. In applications where both step-up and step-down

conversion ratios are required, the buck–boost and Cuk converters can be used.

Simplicity and robustness are among the advantages of the buck–boost converter.

However, the pulsating input and output currents cause high conduction losses, and

thus, impair the efficiency of buck–boost. Furthermore, the buck–boost converter

uses the inductor to store the energy from the input source, and then, release the

stored energy to the output. For this reason, the magnetic components of buck–

boost are subjected to a significant stress. These disadvantages limit the

applications of the buck–boost converter mainly to low power level. The isolated

version of buck–boost, referred to as the flyback converter, can achieve greater

step-up or step-down conversion ratio utilizing a transformer, possibly, with

multiple outputs. As compared with the buck–boost converter, the Cuk converter

has higher efficiency and smaller ripples in input and output currents. A significant

improvement of the Cuk converter performance can be achieved by applying the

zero ripple concept.

The Cuk converter can be found in many high-performance power applications. In

theory buck and boost converters can generate almost any voltage, in practice; the

output voltage range is limited by component stresses that increase at the extreme

duty cycle. Consequently, buck converter losses mount at low duty cycle, whereas

boost converter efficiency deteriorates when the duty cycle tends to unity.

Accordingly, voltage conversion range of the buck converter below 0.1–0.15

becomes impractical whereas that of the boost converters’ is limited to below 8–

10. Additional problems associated with narrow duty cycle are caused by

MOSFET drivers rise and fall times as well as pulse width-modulated (PWM)

controllers that have maximum pulse width limitations. These problems become

even more severe at higher voltages and higher frequencies. Introducing a

transformer helps attaining large step-up or step-down voltage conversion ratio.

Transformers’ turn ratio should be chosen as to provide the desired voltage gain

while keeping the duty cycle within a reasonable range for higher efficiency. The

transformer, however, brings in a whole new set of problems associated with the

magnetizing and leakage inductances, which cause voltage spikes and ringing,

increased core and cooper losses as well as increased volume and cost.

In a quest for converters with wide conversion range, quite a few authors proposed

using converters with nonlinear characteristics. Single-transistor converter

topologies, with quadratic conversion ratios, were proposed in [1] and

demonstrated large step-down conversion ratio. This method has successfully

achieved wide conversion range in the step done direction. A different approach to

obtain wide conversion range utilizing coupled inductors was proposed in [2].

With only minor modification of the tapped-inductor buck, [2] shows low

component count and solves the gate-drive problem by exchanging the position of

the second winding and the top switch. The problem of a high turn-OFF voltage

spike on the top switch was solved by applying a lossless clamp circuit. Due to the

coupled inductor action, the converter demonstrated high step-down dc–dc

conversion ratio, whereas the converter’s efficiency was improved by the extended

duty cycle. A tapped-inductor buck with soft switching was introduced in [3].

Derivations of the tapped-inductor buck were also suggested in [4] and [5].

Another modification of the tapped-buck converter was realized in [6] for power

factor correction (PFC) application. With the addition of a line-frequency-

commutated switch and a diode, both flyback and buck characteristics were

achieved and large step-down was demonstrated. Some applications, especially

battery-operated equipment, require high voltage boosting. To attain very large

voltage step-up, cascaded boost converters that implement the output voltage

increasing in geometric progression were introduced in [7].

These converters effectively enhance the voltage transfer ratio; however, their

circuits are quite complex. In comparison, tapped-inductor boost converters

proposed in [8] and [9] attain a comparable voltage step-up preserving relative

circuit.

Buck-derived converters with tapped inductors. Simplicity. In [10], the boost

converter output terminal and flyback converter output terminal are connected in

series to increase the output voltage gain with the coupled inductor. The boost

converter also functions as an active clamp circuit to recycle the snubber energy.

Operating Principle of the WIWO Converter:

In the following, the steady-state operation of the proposed WIWO converter is

described. The analysis is performed assuming that the circuit is comprised of ideal

components. The coupling coefficient of the tapped inductor is assumed to be

unity. Under continuous inductor current (CCM) condition, the proposed WIWO

converter exhibits four topological states, as shown in Fig. 7. Here, the large output

filter capacitor is replaced by an ideal voltage source. The waveforms and timing

of WIWO for both buck and boost modes are illustrated in Fig. 8.

1) Buck Mode: State 1 (t0 ≤ t < t1) is the buck-mode charging state [see Figs. 7(a)

and 8(a)]. Here, the switch S2 is turned on and S1 is turned off. The diode D

conducts and the coupled inductors L1 and L2 are charged. The energy is also

transferred from dc source to load.

State 2 (t1 ≤ t ≤ t2) is the buck-mode discharging state [see Figs. 7(b) and 8(a)].

Here, the switch S2 is turned off also cutting off the current in the L1 winding,

whereas S1 is turned on and the diode D conducts L2 current to the load.

2) Boost Mode: State 3 (t_0 ≤ t < t_1) is the boost-mode charging state [see Figs.

7(c) and 8(b)]. Here, the switches S1 and S2 are turned on charging the L1

inductor. The diode D is cut off by the negative voltage induced in L2 winding.

The output voltage is supported by the capacitor C.

State 4 (t_1 ≤ t ≤ t_2) is the boost-mode discharging state [see Figs. 7(d) and

8(b)]. Here, the switch S2 is still ON whereas S1 is turned off. Both windings L1

and L2 conduct through the diode D and discharge the stored energy to the output.

Fig. 7. Four topological states of the WIWO converter. (a) Buck-mode

charging state. (b) Buck-mode discharging state. (c) Boost-mode charging

state. (d) Boost-mode discharging state.

BLOCK DIAGRAM DESCRIPTION:

MICROCONTROLLER PIC 16f877A

High performance RISC CPU

• Only 35 single word instructions to learn

• All single cycle instructions except for program branches which are two cycle

• Operating speed: DC - 20 MHz clock input DC - 200 ns instruction cycle

• Up to 8K x 14 words of FLASH Program Memory, Up to 368 x 8 bytes of Data

Memory (RAM) Up to 256 x 8 bytes of EEPROM Data Memory

• Pinout compatible to the PIC16C73B/74B/76/77

• Interrupt capability (up to 14 sources)

• Eight level deep hardware stack

• Direct, indirect and relative addressing modes

• Power-on Reset (POR)

• Power-up Timer (PWRT) and Oscillator Start-up Timer (OST)

• Watchdog Timer (WDT) with its own on-chip RC oscillator for reliable peration

• Programmable code protection

• Power saving SLEEP mode

• Selectable oscillator options

• Low power, high speed CMOS FLASH/EEPROM technology

• Fully static design

• In-Circuit Serial Programming (ICSP) via two pins

• Single 5V In-Circuit Serial Programming capability

• In-Circuit Debugging via two pins

• Processor read/write access to program memory

• Wide operating voltage range: 2.0V to 5.5V

• High Sink/Source Current: 25 mA

• Commercial, Industrial and Extended temperature ranges

• Low-power consumption:

ADVANTAGES OF MICROCONTROLLER

If a system is developed with a microprocessor the designer has to go for

external memory such as RAM ,ROM or EPROM and peripherals and hence

the size of the PCB will large enough to hold all the required peripheral.

But, the microcontroller has got all there peripheral facilities on a single chip

so developed of a similar system with a microcontroller reduces PCB size

and cost of the design.

One of the major difference between a microcontroller and a microprocessor

is that a controller. often deals with bits, not bytes as in the real world

application, for example switch contacts can only be open or

close ,indicators should be lit or dark and motors can be either turned on or

off and so forth.

The microcontroller has two 16 bits timer/counters built within it, which

makes it more suitable to this application since, we need to produce some

accurate time delays.

This microcontroller has a 8 bit internal Analog to digital converter with a

10 bit resolution, which will after the usage of external ADC and the circuit

and hardware complexity.

This controller also has a higher erase cycle of 10,000 and for the eeprom its

1 lak number of time. This controller other advantage is it’s a RISC

computing system.

This document contains device specific information. Additional information may

be found in the PIC micro Mid-Range Reference Manual (DS33023), which may

be obtained from your local Microchip Sales representative or downloaded from

the Microchip website. The Reference Manual should be considered a

complementary document to this data sheet, and is highly recommended reading

for a better understanding of the device architecture and operation of the peripheral

modules.

I/O PORTS

Some pins for these I/O ports are multiplexed with an alternate function for the

peripheral features on the device. In general, when a peripheral is enabled, that pin

may not be used as a general purpose I/O pin. Additional information on I/O ports

may be found in the PICmicro™ Mid-Range Reference Manual, (DS33023).

3.1 PORTA and the TRISA Register

PORTA is a 6-bit wide, bi-directional port. The corresponding data direction

register is TRISA. Setting a TRISA bit (= 1) will make the corresponding PORTA

pin an input (i.e., put the corresponding output driver in a Hi-Impedance mode).

Clearing a TRISA bit (= 0) will make the corresponding PORTA pin an output

(i.e., put the contents of the output latch on the selected pin). Reading the PORTA

register reads the status of the pins, whereas writing to it will write to the port

latch. All write operations are read-modify-write operations. Therefore, a write to a

port implies that the port pins are read; the value is modified and then written to

the port data latch. Pin RA4 is multiplexed with the Timer0 module clock input to

become the RA4/T0CKI pin. The RA4/T0CKI pin is a Schmitt Trigger input and

an open drain output. All other PORTA pins have TTL input levels and full CMOS

output drivers. Other PORTA pins are multiplexed with analog inputs and analog

VREF input. The operation of each pin is selected by clearing/setting the control

bits in the ADCON1 register (A/D Control Register1).

PORTB and the TRISB Register

PORTB is an 8-bit wide, bi-directional port. The corresponding data direction

register is TRISB. Setting a TRISB bit (= 1) will make the corresponding PORTB

pin an input (i.e., put the corresponding output driver in a Hi-Impedance mode).

Clearing a TRISB bit (= 0) will make the corresponding PORTB pin an output

(i.e., put the contents of the output latch on the selected pin). Three pins of PORTB

are multiplexed with the Low Voltage Programming function: RB3/PGM,

RB6/PGC and RB7/PGD. The alternate functions of these pins are described in the

Special Features Section. Each of the PORTB pins has a weak internal pull-up. A

Single control bit can turn on all the pull-ups. This is performed by clearing bit

RBPU (OPTION_REG<7>). The weak pull-up is automatically turned off when

the port pin is configured as an output. The pull-ups are disabled on a Power-on

Reset.

Four of the PORTB pins, RB7:RB4, have an interrupt on- change feature.

Only pins configured as inputs can cause this interrupt to occur (i.e., any RB7:RB4

pin configured as an output is excluded from the interrupt on- change comparison).

The input pins (of RB7:RB4) are compared with the old value latched on the last

read of PORTB. The “mismatch” outputs of RB7:RB4 are OR’ed together to

generate the RB Port Change Interrupt with flag bit RBIF (INTCON<0>).

PORT C

PORTC is an 8-bit wide, bi-directional port. The corresponding data direction

register is TRISC. Setting a TRISC bit (= 1) will make the corresponding PORTC

pin an input (i.e., put the corresponding output driver in a Hi-Impedance mode).

Clearing a TRISC bit (= 0) will make the corresponding PORTC pin an output

(i.e., put the contents of the output latch on the selected pin). PORTC is

multiplexed with several peripheral functions (Table 3-5).

PORTC pins have Schmitt Trigger input buffers. When the I2C module is enabled,

the PORTC<4:3> pins can be configured with normal I2C levels or with SMBus

levels by using the CKE bit (SSPSTAT<6>). When enabling peripheral functions,

care should be taken in defining TRIS bits for each PORTC pin. Some peripherals

override the TRIS bit to make a pin an output, while other peripherals override the

TRIS bit to make a pin an input. Since the TRIS bit override is in effect while the

peripheral is enabled, read-modify write instructions (BSF, BCF, XORWF) with

TRISC as destination, should be avoided. The user should refer to the

corresponding peripheral section for the correct TRIS bit settings.

PORTD and TRISD Registers

PORTD and TRISD are not implemented on the PIC16F873 or PIC16F876.

PORTD is an 8-bit port with Schmitt Trigger input buffers. Each pin is

individually configurable as an input or output. PORTD can be configured as an

8-bit wide microprocessor port (parallel slave port) by setting control bit

PSPMODE (TRISE<4>). In this mode, the input buffers are TTL.

DATA EEPROM AND FLASH PROGRAM MEMORY

The Data EEPROM and FLASH Program Memory are readable and writable

during normal operation over the entire VDD range. These operations take place

on a single byte for Data EEPROM memory and a single word for Program

memory. A write operation causes an erase-then-write operation to take place on

the specified byte or word. A bulk erase operation may not be issued from user

code (which includes removing code protection). Access to program memory

allows for checksum calculation. The values written to program memory do not

need to be valid instructions. Therefore, up to 14-bit numbers can be stored in

memory for use as calibration parameters, serial numbers, packed 7-bit ASCII, etc.

Executing a program memory location containing data that form an invalid

instruction, results in the execution of a NOP instruction. The EEPROM Data a

memory is rated for high erase/ write cycles (specification D120). The FLASH

program memory is rated much lower (specification D130), because EEPROM

data memory can be used to store frequently updated values. An on-chip timer

controls the write time and it will vary with voltage and temperature, as well as

from chip to chip. Please refer to the specifications for exact limits (specifications

D122 and D133). A byte or word write automatically erases the location and writes

the new value (erase before write). Writing to EEPROM data memory does not

impact the operation of the device. Writing to program memory will cease the

execution of instructions until the write is complete. The program memory cannot

be accessed during the write. During the write operation, the oscillator continues to

run, the peripherals continue to function and interrupt events will be detected and

essentially “queued” until the write is complete. When the write completes, the

next instruction in the pipeline is executed and the branch to the interrupt vector

will take place, if the interrupt is enabled and occurred during the write. Read and

write access to both memories take place indirectly through a set of Special

Function Registers (SFR). The six SFRs used are:

• EEDATA

• EEDATH

• EEADR

• EEADRH

• EECON1

• EECON2

TIMER0 MODULE

The Timer0 module timer/counter has the following features:

• 8-bit timer/counter

• Readable and writable

• 8-bit software programmable prescaler

• Internal or external clock select

• Interrupt on overflow from FFh to 00h

• Edge select for external clock

in the block diagram of the Timer0 module and the prescaler shared with the WDT.

Additional information on the Timer0 module is available in the PICmicro™ Mid-

Range MCU Family Reference Manual (DS33023).

Timer mode is selected by clearing bit T0CS (OPTION_REG<5>). In Timer mode,

the Timer0 module will increment every instruction cycle (without prescaler). If

the TMR0 register is written, the increment is inhibited for the following two

instruction cycles. The user can work around this by writing an adjusted value to

the TMR0 register

TIMER1 MODULE

The Timer1 module is a 16-bit timer/counter consisting of two 8-bit registers

(TMR1H and TMR1L), which are readable and writable. The TMR1 Register pair

(TMR1H:TMR1L) increments from 0000h to FFFFh and rolls over to 0000h. The

TMR1 Interrupt, if enabled, is generated on overflow, which is latched in interrupt

flag bit TMR1IF (PIR1<0>). This interrupt can be enabled/disabled by

setting/clearing TMR1 interrupt enable bit TMR1IE (PIE1<0>). Timer1 can

operate in one of two modes:

• As a timer

• As a counter

The operating mode is determined by the clock select bit, TMR1CS (T1CON<1>).

TIMER2 MODULE

Timer2 is an 8-bit timer with a prescaler and a postscaler. It can be used as the

PWM time-base for the PWM mode of the CCP module(s). The TMR2 register is

readable and writable, and is cleared on any device RESET. The input clock

(FOSC/4) has a prescale option of 1:1,1:4, or 1:16, selected by control bits

T2CKPS1:T2CKPS0 (T2CON<1:0>). The Timer2 module has an 8-bit period

register, PR2. A Timer2 increment from 00h until it matches PR2 and then resets

to 00h on the next increment cycle. PR2 is a readable and writable register. The

PR2 register is initialized to FFh upon RESET. The match output of TMR2 goes

through a 4-bit postscaler (which gives a 1:1 to 1:16 scaling inclusive) to generate

a TMR2 interrupt (latched in flag bit TMR2IF, (PIR1<1>)). Timer2 can be shut-off

by clearing control bit TMR2ON (T2CON<2>), to minimize power consumption.

POWER SUPPLY UNIT

4.1 POWER SUPPLY

All electronic circuits works only in low DC voltage, so we need a power

supply unit to provide the appropriate voltage supply for their proper functioning

.This unit consists of transformer, rectifier, filter & regulator. AC voltage of

typically 230v rms is connected to a transformer voltage down to the level to

the desired ac voltage. A diode rectifier that provides the full wave rectified

voltage that is initially filtered by a simple capacitor filter to produce a dc

voltage. This resulting dc voltage usually has some ripple or ac voltage

variation . A regulator circuit can use this dc input to provide dc voltage that not

only has much less ripple voltage but also remains the same dc value even the dc

voltage varies somewhat, or the load connected to the output dc voltages

changes.

Fig 6.General Block of Power Supply Unit

TRANSFORMER: A transformer is a static piece of which electric power in one

circuit is transformed into electric power of same frequency in another circuit. It can

raise or lower the voltage in the circuit, but with a corresponding decrease or increase

in current. It works with the principle of mutual induction. In our project we are using

a step down transformer to providing a necessary supply for the electronic circuits.

Here we step down a 230v ac into 12v ac.

RECTIFIER: A dc level obtained from a sinusoidal input can be improved 100%

using a process called full wave rectification. Here in our project for full wave

rectification we use bridge rectifier. From the basic bridge configuration we see that

two diodes (say D2 & D3) are conducting while the other two diodes

(D1 & D4) are in off state during the period t = 0 to T/2.Accordingly for the negative

cycle of the input the conducting diodes are D1 & D4 .Thus the polarity across the

load is the same.

In the bridge rectifier the diodes may be of variable types like 1N4001, 1N4003,

1N4004, 1N4005, IN4007 etc… can be used. But here we use 1N4007, because it can

withstand up to 1000v.

FILTERS: In order to obtain a dc voltage of 0 Hz, we have to use a low pass filter.

So that a capacitive filter circuit is used where a capacitor is connected at the rectifier

output& a dc is obtained across it. The filtered waveform is essentially a dc voltage

with negligible ripples & it is ultimately fed to the load.

REGULATORS: The output voltage from the capacitor is more filtered & finally

regulated. The voltage regulator is a device, which maintains the output voltage

constant irrespective of the change in supply variations, load variations & temperature

changes. Here we use fixed voltage regulator namely LM7805.The IC LM7805 is a

+5v regulator which is used for microcontroller.

Circuit Diagram:

- +

D12

1

3

4

J1

CON1

12

C1

470µC3

100µC40.01µ

R1

220 ohm

D2

LED

U2LM7805C/TO

1 3

2

IN OUT

GND

J1

CON1

12

4.2 Features & Description of Regulators

• Output Current up to 1A

• Output Voltages of 5, 6, 8, 9, 10, 12, 15, 18, 24V

• Thermal Overload Protection

• Short Circuit Protection

• Output Transistor Safe Operating Area Protection

The KA78XX/KA78XXA series of three-terminal positive regulator are

available in the TO-220/D-PAK package and with several fixed output voltages,

making them useful in a wide range of applications. Each type employs internal

current limiting, thermal shut down and safe operating area protection, making it

essentially indestructible. If adequate heat sinking is provided, they can deliver

over 1A output current. Although designed primarily as fixed voltage regulators,

these devices can be used with external components to obtain adjustable voltages

and currents.

4.3 Electrical Characteristics of KA7805A

Load and line regulation are specified at constant junction temperature.

Change in VO due to heating effects must be taken into account separately. Pulse

testing with low duty is used

4.5 Main Features:

1. Single contact and double contacts type offer switching capacity by 15A

in small size for exclusive automobile control relay switching box use.

2. Standard and European Specification are available to comply with

various electrical specification requirements.

3. Simple magnetic circuit to meet mass production for low cost offer.

Standard type is open type without dust cover. If dust cover is required, suitable

cased relay can be prepared.

4. Bubble Test conforming to JIS standard will be conducted on the SX

type of Relay for checking the Relay sealing.

5. Operating ambient temperature range covers from -30ºC to 80ºC at no

current on Relay’s contacts.

4.5.1 Application

Car Control Switching Box (Alarm System, Automatic Door Locking

System….), Car Flashers…. etc.

POWER CIRCUIT AND POWER SUPPLY MODEL

The power supply model consists of the 230V supply which is to be rectified

and fed to the inverter. To perform this operation we go for the diode bridge

rectifier with capacitors.

2.1 Diode Bridge Rectifier

Fig. 2.1 Diode Bridge Rectifier

A diode bridge or bridge rectifier is an arrangement of four diodes connected in a

bridge circuit as shown below, that provides the same polarity of output voltage for

any polarity of the input voltage. When used in its most common application, for

conversion of alternating current (AC) input into direct current (DC) output, it is

known as a bridge rectifier. The bridge rectifier provides full wave rectification

from a two wire AC input (saving the cost of a center tapped transformer) but has

two diode drops rather than one reducing efficiency over a center tap based design

for the same output voltage.

Fig 2.2 Schematic of a Diode Bridge Rectifier

The essential feature of this arrangement is that for both polarities of the voltage at

the bridge input, the polarity of the output is constant.

2.2 Basic Operation of Diode Bridge Rectifier

When the input connected at the left corner of the diamond is positive with respect

to the one connected at the right hand corner, current flows to the right along the

upper colored path to the output, and returns to the input supply via the lower one.

When the right hand corner is positive relative to the left hand corner, current

flows along the upper colored path and returns to the supply via the lower colored

path.

Fig 2.4 AC, half-wave and full wave rectified signals

In each case, the upper right output remains positive with respect to the

lower right one. Since this is true whether the input is AC or DC, this circuit not

only produces DC power when supplied with AC power: it also can provide what

is sometimes called "reverse polarity protection". That is, it permits normal

functioning when batteries are installed backwards or DC input-power supply

wiring "has its wires crossed" (and protects the circuitry it powers against damage

that might occur without this circuit in place).

Prior to availability of integrated electronics, such a bridge rectifier was

always constructed from discrete components. Since about 1950, a single four-

terminal component containing the four diodes connected in the bridge

configuration became a standard commercial component and is now available with

various voltage and current ratings.

Output smoothing

For many applications, especially with single phase AC where the full-wave

bridge serves to convert an AC input into a DC output, the addition of a capacitor

may be important because the bridge alone supplies an output voltage of fixed

polarity but pulsating magnitude (see photograph above).

Fig 2.5 Rectifier with smoothing capacitor

The function of this capacitor, known as a 'smoothing capacitor' (see also

filter capacitor) is to lessen the variation in (or 'smooth') the raw output voltage

waveform from the bridge. One explanation of 'smoothing' is that the capacitor

provides a low impedance path to the AC component of the output, reducing the

AC voltage across, and AC current through, the resistive load. In less technical

terms, any drop in the output voltage and current of the bridge tends to be

cancelled by loss of charge in the capacitor. This charge flows out as additional

current through the load. Thus the change of load current and voltage is reduced

relative to what would occur without the capacitor. Increases of voltage

correspondingly store excess charge in the capacitor, thus moderating the change

in output voltage / current.

The capacitor and the load resistance have a typical time constant τ = RC where C

and R are the capacitance and load resistance respectively. As long as the load

resistor is large enough so that this time constant is much longer than the time of

one ripple cycle, the above configuration will produce a well smoothed DC voltage

across the load resistance. In some designs, a series resistor at the load side of the

capacitor is added. The smoothing can then be improved by adding additional

stages of capacitor–resistor pairs, often done only for sub-supplies to critical high-

gain circuits that tend to be sensitive to supply voltage noise.

Output can also be smoothed using a choke, a coil of conductor enclosed by

an iron frame (similar to a transformer in construction). This tends to keep the

current (rather than the voltage) constant. Due to the relatively high cost of an

effective choke compared to a resistor and capacitor this is not employed in

modern equipment. Some early console radios created the speaker's constant field

with the current from the high voltage ("B +") power supply, which was then

routed to the consuming circuits, rather than using a permanent magnet to create

the speaker's constant magnetic field. The speaker field coil thus acted as a choke.

Device rating of full bridge rectifier:

Full bridge rectifier – rating 5A, filter capacitor – 1000 micro farad, 63V.

DRIVER CIRCUIT

Driver performs three operations.

1: Impedance matching

2: Isolation

3: Amplification

The buffer IC used here IC 4050 is used for pulse generation to generate triggering

pulse. There are pull up resistors to provide a resistance in series with the

microcontroller which acts as a current source here. This IC acts as an impedance

improvement buffer IC. Voltage follower concept is used and the signal is getting

inverted. Now it is given to the isolator.

Since the microcontroller is a sensitive device and MOSFET carries high

current, in order to provide isolation between the two, isolation is being provided

by the optocoupler.

General description:

The HEF4050B provides six non-inverting buffers with high current output

capability suitable for driving TTL or high capacitive loads. Since input voltages in

excess of the buffers supply voltage are permitted, the buffers may also be used to

convert logic levels of up to 15 V to standard TTL levels. It operates over a

recommended VDD power supply range of 3 V to 15 V referenced to VSS (usually

ground). Unused inputs must be connected to VDD, VSS, or another input.

Features and benefits:

Accepts input voltages in excess of the supply voltage

Fully static operation

5 V, 10 V, and 15 V parametric ratings

Standardized symmetrical output characteristics

Specified from 40 degree C to +85 degree C

Applications:

LOCMOS (Local Oxidation CMOS) to DTL/TTL converter

HIGH sink current for driving two TTL loads

HIGH-to-LOW level logic conversion

Functional diagram

Pinning information:

Pin description:

3.5.1 Optocoupler:

In electronics, an Opto-isolator (or optical isolator, optocoupler or photo

coupler) is a device that uses a short optical transmission path to transfer a signal

between elements of a circuit, typically a transmitter and a receiver, while keeping

them electrically isolated — since the signal goes from an electrical signal to an

optical signal back to an electrical signal, electrical contact along the path is

broken.

3.16 An Opto-isolator integrated circuit

Fig 3.17 Schematic diagram

A common implementation involves an LED and a light sensor, separated so that

light may travel across a barrier but electrical current may not. When an electrical

signal is applied to the input of the Opto-isolator, its LED lights, its light sensor

then activates, and a corresponding electrical signal is generated at the output.

Unlike a transformer, the Opto-isolator allows for DC coupling and generally

provides significant protection from serious overvoltage conditions in one circuit

affecting the other.

With a photodiode as the detector, the output current is proportional to the amount

of incident light supplied by the emitter. The diode can be used in a photovoltaic

mode or a photoconductive mode.

In photovoltaic mode, the diode acts like a current source in parallel with a

forward-biased diode. The output current and voltage are dependent on the load

impedance and light intensity. In photoconductive mode, the diode is connected to

a supply voltage, and the magnitude of the current conducted is directly

proportional to the intensity of light.

An Opto-isolator can also be constructed using a small incandescent lamp in

place of the LED; such a device, because the lamp has a much slower response

time than an LED, will filter out noise or half-wave power in the input signal. In so

doing, it will also filter out any audio- or higher-frequency signals in the input. It

has the further disadvantage, of course, (an overwhelming disadvantage in most

applications) that incandescent lamps have finite life spans. Thus, such an

unconventional device is of extremely limited usefulness, suitable only for

applications such as science projects.

The optical path may be air or a dielectric waveguide. The transmitting and

receiving elements of an optical isolator may be contained within a single compact

module, for mounting, for example, on a circuit board; in this case, the module is

often called an Opto isolator or Opto-isolator. The photo sensor may be a

photocell, phototransistor, or an optically triggered SCR or Triac. Occasionally,

this device will in turn operate a power relay or contactor.

Device rating:

OPTOCOUPLER MCT2E – 1 K, 100 Ω resistance

Here the LED glows and current flows through the base of the transistor, so

the signal will be got across a resistance and given to another transistor CK 100

which is a PNP transistor to provide inversion again.

In order to improve the voltage and the current gain we go for the Darlington

amplifier, which amplifies the voltage.

There are many situations where signals and data need to be transferred from one

subsystem to another within a piece of electronics equipment, or from one piece of

equipment to another, without making a direct ohmic electrical connection. Often

this is because the source and destination are (or may be at times) at very different

voltage levels, like a microprocessor which is operating from 5V DC but being

used to control a triac which is switching 240V AC. In such situations the link

between the two must be an isolated one, to protect the microprocessor from

overvoltage damage.

Optocoupler typically come in a small 6-pin or 8-pin IC package, but are

essentially a combination of two distinct devices: an optical transmitter, typically a

gallium arsenide LED (light-emitting diode) and an optical receiver such as a

phototransistor or light-triggered diac. The two are separated by a transparent

barrier which blocks any electrical current flow between the two, but does allow

the passage of light. The basic idea is shown in Fig.1, along with the usual circuit

symbol for an optocoupler.

3.5.2 Darlington amplifier

Fig 3.18 Circuit diagram of Darlington configuration

In electronics, the Darlington transistor is a semiconductor device which

combines two bipolar transistors in tandem (often called a "Darlington pair") in a

single device so that the current amplified by the first is amplified further by the

second transistor. This gives it high current gain (written β or hFE), and takes up

less space than using two discrete transistors in the same configuration. The use of

two separate transistors in an actual circuit is still very common, even though

integrated packaged devices are available. This configuration was invented by Bell

Laboratories engineer Sidney Darlington. The idea of putting two or three

transistors on a single chip was patented by him, but not the idea of putting an

arbitrary number of transistors, which would have covered all modern integrated

circuits.

A similar transistor configuration using two transistors of opposite type

(NPN and PNP) is the Sziklai pair, sometimes called the "complementary

Darlington". Finally the amplified signal is sent to the multilevel inverter and the

output is obtained.

Types of Transistors used:

Ck100 - PNP

2222N – NPN

Transistor:

A transistor is a semiconductor device used

to amplify and switch electronic signals and electrical power. It is composed

of semiconductor material with at least three terminals for connection to an

external circuit. A voltage or current applied to one pair of the transistor's terminals

changes the current through another pair of terminals. Because the controlled

(output) power can be higher than the controlling (input) power, a transistor

can amplify a signal. Today, some transistors are packaged individually, but many

more are found embedded in integrated circuits.

There are two types of transistors, which have slight differences in how they are

used in a circuit. A bipolar transistor has terminals labeled base, collector,

and emitter. A small current at the base terminal (that is, flowing between the base

and the emitter) can control or switch a much larger current between the collector

and emitter terminals. For a field-effect transistor, the terminals are labeled gate,

source, and drain, and a voltage at the gate can control a current between source

and drain.

The image to the right represents a typical bipolar transistor in a circuit. Charge

will flow between emitter and collector terminals depending on the current in the

base. Because internally the base and emitter connections behave like a

semiconductor diode, a voltage drop develops between base and emitter while the

base current exists. The amount of this voltage depends on the material the

transistor is made from, and is referred to as VBE.

Transistor as a switch

Transistors are commonly used as electronic switches, both for high-power

applications such as switched-mode power supplies and for low-power applications

such as logic gates.

In a grounded-emitter transistor circuit, such as the light-switch circuit shown, as

the base voltage rises, the emitter and collector currents rise exponentially. The

collector voltage drops because of reduced resistance from collector to emitter. If

the voltage difference between the collector and emitter were zero (or near zero),

the collector current would be limited only by the load resistance (light bulb) and

the supply voltage. This is called saturation because current is flowing from

collector to emitter freely. When saturated, the switch is said to beon.[29]

Providing sufficient base drive current is a key problem in the use of bipolar

transistors as switches. The transistor provides current gain, allowing a relatively

large current in the collector to be switched by a much smaller current into the base

terminal. The ratio of these currents varies depending on the type of transistor, and

even for a particular type, varies depending on the collector current. In the example

light-switch circuit shown, the resistor is chosen to provide enough base current to

ensure the transistor will be saturated.

In any switching circuit, values of input voltage would be chosen such that the

output is either completely off,[30] or completely on. The transistor is acting as a

switch, and this type of operation is common in digital circuits where only "on"

and "off" values are relevant.

BJT used as an electronic switch, in grounded-emitter configuration.

Transformer:

Electrical Power Transformer is a static device which transforms electrical energy

from one circuit to another without any direct electrical connection and with the

help of mutual induction between to windings. It transforms power from one

circuit to another without changing its frequency but may be in different voltage

level.

This is very short and simple definition of transformer, as we will go through this

portion of tutorial related to Electrical Power Transformer, we will understand

more clearly and deeply "what is Transformer ?" and basic theory of

transformer.

Working Principle of transformer

The working principle of transformer is very simple. It depends upon Faraday's law

of electromagnetic induction. Actually mutual induction between two or more

winding is responsible for transformation action in an electrical transformer.

Faraday's laws of Electromagnetic Induction

According to these Faraday'slaw,"Rate of change of flux linkage with respect to

time is directly proportional to the induced EMF in a conductor or coil".

Basic Theory of Transformer

Say you have one winding which is supplied by an alternating electrical source.

The alternating current through the winding produces a continually changing flux

or alternating flux surrounds the winding. If any other winding is brought nearer to

the previous one, obviously some portion of this flux will link with the second. As

this flux is continually changing in its amplitude and direction, there must be a

change in flux linkage in the second winding or coil. According to Faraday's law of

electromagnetic induction, there must be an EMF induced in the second. If the

circuit of the latter winding is closed, there must be electric current flows through

it. This is the simplest form of electrical power transformer and this is most basic

of working principle of transformer.

For better understanding we are trying to repeat the above explanation in more

brief here. Whenever we apply alternating current to an electric coil, there will be

an alternating flux surrounding that coil. Now if we bring another coil nearby this

first one, there will be an alternating flux linkage with that second coil. As the flux

is alternating, there will be obviously a rate of change of flux linkage with respect

to time in the second coil. Naturally emf will be induced in it as per Faraday's law

of electromagnetic induction. This is the most basic concept of theory of

transformer

The winding which takes electrical power from the source, is generally known as

Primary Winding of transformer. Here in our above example it is first winding.

The winding which gives the desired output voltage due to mutual induction in the

transformer, is commonly known as Secondary Winding of Transformer. Here in

our example it is second winding

The above mentioned form of transformer is theoretically possible but not

practically, because in open air very tiny portion of the flux of the first winding

will link with second so the electric current flows through the closed circuit of

latter, will be so small that it may be difficult to measure.

The rate of change of flux linkage depends upon the amount of linked flux, with

the second winding. So it desired to be linked almost all flux of primary winding,

to the secondary winding. This is effectively and efficiently done by placing one

low reluctance path common to both the winding. This low reluctance path is core

of transformer, through which maximum number of flux produced by the primary

is passed through and linked with the secondary winding. This is most

basic theory of transformer.

TYPES OF DC-DC CONVERTERS:

BOOST CONVERTER

A boost converter (step-up converter) is a power converter with an output

DC voltage greater than its input DC voltage. It is a class of switching-mode power

supply (SMPS) containing at least two semiconductor switches (a diode and a

transistor) and at least one energy storage element. Filters made of capacitors

(sometimes in combination with inductors) are normally added to the output of the

converter to reduce output voltage ripple.

Boost converter (step-up converter)

A boost converter (step-up converter) is a DC-to-DC power converter with an

output voltage greater than its input voltage. It is a class of switched-mode power

supply (SMPS) containing at least two semiconductor switches (a diode and

a transistor) and at least one energy storage element, a capacitor, inductor, or the

two in combination. Filters made of capacitors (sometimes in combination with

inductors) are normally added to the output of the converter to reduce output

voltage ripple.

The basic schematic of a boost converter. The switch is typically a MOSFET,

IGBT, or BJT.

Overview:

Power for the boost converter can come from any suitable DC sources, such as

batteries, solar panels, rectifiers and DC generators. A process that changes one

DC voltage to a different DC voltage is called DC to DC conversion. A boost

converter is a DC to DC converter with an output voltage greater than the source

voltage. A boost converter is sometimes called a step-up converter since it “steps

up” the source voltage. Since power ( ) must be conserved, the output

current is lower than the source current.

Buck Converter:

Buck converter is a voltage step down and current step up converter.

The simplest way to reduce the voltage of a DC supply is to use a linear

regulator (such as a 7805), but linear regulators waste energy as they operate by

dissipating excess power as heat. Buck converters, on the other hand, can be

remarkably efficient (95% or higher for integrated circuits), making them useful

for tasks such as converting the main voltage in a computer (12 V in a desktop, 12-

24 V in a laptop) down to the 0.8-1.8 volts needed by the processor.

Theory of operation

The basic operation of the buck converter has the current in an inductor controlled

by two switches (usually a transistor and a diode). In the idealized converter, all

the components are considered to be perfect. Specifically, the switch and the diode

have zero voltage drop when on and zero current flow when off and the inductor

has zero series resistance. Further, it is assumed that the input and output voltages

do not change over the course of a cycle (this would imply the output capacitance

as being infinite).

Concept

The conceptual model of the buck converter is best understood in terms of the

relation between current and voltage of the inductor. Beginning with the switch

open (in the "off" position), the current in the circuit is 0. When the switch is first

closed, the current will begin to increase, and the inductor will produce an

opposing voltage across its terminals in response to the changing current. This

voltage drop counteracts the voltage of the source and therefore reduces the net

voltage across the load. Over time, the rate of change of current decreases, and the

voltage across the inductor also then decreases, increasing the voltage at the load.

During this time, the inductor is storing energy in the form of a magnetic field. If

the switch is opened while the current is still changing, then there will always be a

voltage drop across the inductor, so the net voltage at by the load will always be

less than the input voltage source. When the switch is opened again, the voltage

source will be removed from the circuit, and the current will decrease. The

changing current will produce a change in voltage across the inductor, now aiding

the source voltage. The stored energy in the inductor's magnetic field supports

current flow through the load. During this time, the inductor is discharging its

stored energy into the rest of the circuit If the switch is closed again before the

inductor fully discharges, the voltage at the load will always be greater than zero.

Buck Boost Converter

A DC-DC converter is nothing more than a DC transformer or a device that

provides a loss less transfer of energy between different circuits at different voltage

levels. When dc-dc conversion is needed there is also a need for control and a

need for higher efficiencies. If the latter were not important we could just use a

voltage divider and get the change in voltage we are looking for. In modern dc

electronics we need more than just voltage reduction. What really are needed are

voltage transfers, polarity reversals, and increased and decreased voltages with

control. One method of building a dc transformer is to use switching converters

called choppers. The provided switching function requires a duty ratio, which will

give us the control that has been needed.

Probably the most important consideration of all the elements is the

inductor. The inductor value is important to not be below the critical value so that

the converter will not have a discontinuous mode. This happens when the inductor

is too small to maintain current flow at all times. When the converter is in

discontinuous mode its output becomes load dependent.

4.2 MOSFET

A MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is a

semiconductor device. A MOSFET is most commonly used in the field of power

electronics. A semiconductor is made of manufactured material that acts neither

like a insulator nor a conductor.

We are using n-channel power MOSFET. PWM pulses from the microcontroller

are given to the Gate terminal of Mosfet. By controlling ON time and OFF time,

the output DC Voltage will be regulated. The rectified output voltage is given to

the Source(S) and Drain (D) terminals of the power MOSFET.

An example of using the MOSFET as a switch:

In this circuit arrangement an Enhancement-mode N-channel MOSFET is being

used to switch a simple lamp "ON" and "OFF" (could also be an LED). The gate

input voltage VGS is taken to an appropriate positive voltage level to turn the

device and therefore the lamp either fully "ON", (VGS = +ve) or at a zero

voltage level that turns the device fully "OFF", (VGS = 0).

If the resistive load of the lamp was to be replaced by an inductive load such as a

coil, solenoid or relay a "flywheel diode" would be required in parallel with the

load to protect the MOSFET from any self generated back-emf.

Toroidal inductors and transformers

Toroidal inductors and transformers are passive electronic components, typically

consisting of a circular ring-shaped magnetic core of high magnetic

permeability material such as iron powder or ferrite, around which wire is coiled to

make an inductor. Toroidal coils are used in a broad range of applications in AC

electronic circuits, such as high-frequency coils and transformers.

An inductor with a closed-loop core can have a higher magnetic field and thus

higher inductance and Q factor than similarly constructed coils with a straight core

(solenoid coils). This is because the entire path of the magnetic field lines is within

the high permeability core, while in an inductor with a straight core the magnetic

field lines emerging from one end of the core have a long air path to enter the other

end. In recent years, the use of Toroidal (donut) shape cores has increased greatly.

The advantage of the Toroidal shape is that due to its symmetry the amount of

magnetic flux that escapes outside the core (leakage flux) is minimum, therefore it

radiates less electromagnetic interference(EMI) to nearby circuits or equipment.

EMI is of increasing importance in modern low power, high frequency electronics.

Inductor

An inductor, also called a coil or reactor, is a passive two-terminal electrical

component which resists changes in electric current passing through it. It consists

of a conductor such as a wire, usually wound into a coil. When a current flows

through it, energy is stored temporarily in a magnetic field in the coil. When the

current flowing through an inductor changes, the time-varying magnetic field

induces a voltage in the conductor, according to Faraday’s law of electromagnetic

induction, which opposes the change in current that created it.

An inductor is characterized by its inductance, the ratio of the voltage to the rate of

change of current, which has units of henries (H). Inductors have values that

typically range from 1 µH (10-6H) to 1 H. Many inductors have a magnetic

core made of iron or ferrite inside the coil, which serves to increase the magnetic

field and thus the inductance. Along with capacitors and resistors, inductors are

one of the three passive linear circuit elements that make up electric circuits.

Inductors are widely used in alternating current (AC) electronic equipment,

particularly in radio equipment. They are used to block the flow of AC current

while allowing DC to pass; inductors designed for this purpose are called chokes.

They are also used in electronic filters to separate signals of different frequencies,

and in combination with capacitors to make tuned circuits, used to tune radio and

TV receivers.

Inductive coupling:

In electrical engineering, two conductors are referred to as mutual-inductively

coupled or magnetically coupled when they are configured such that change in

current flow through one wire induces a voltage across the ends of the other wire

through electromagnetic induction. The amount of inductive coupling between two

conductors is measured by their mutual inductance.

The coupling between two wires can be increased by winding them into coils and

placing them close together on a common axis, so the magnetic field of one coil

passes through the other coil. The two coils may be physically contained in a single

unit, as in the primary and secondary sides of a transformer, or may be separated.

Coupling may be intentional or unintentional.

Unintentional coupling is called cross-talk, and is a form of electromagnetic

interference. Inductive coupling favors low frequency energy sources. High

frequency energy sources generally use capacitive coupling.

An inductively coupled transponder comprises an electronic data carrying device,

usually a single microchip, and a large coil that functions as an antenna.

Inductively coupled transponders are almost always operated passively.

Magnetic coupling transfers torque from one magnetic gear to another.

Some diver propulsion vehicles and remotely operated underwater

vehicles use magnetic coupling to transfer torque from the electric motor to the

prop. The magnetic coupling has several advantages over a traditional stuffing box

SOFTWARE IMPLEMENTATION

6.1 INTRODUCTION TO MATLAB:

MATLAB is a software package for computation in engineering,

science, and applied mathematics.

It offers a powerful programming language, excellent graphics, and a wide

range of expert knowledge. MATLAB is published by and a trademark of The

MathWorks, Inc.

The focus in MATLAB is on computation, not mathematics: Symbolic

expressions and manipulations are not possible (except through the optional

Symbolic Toolbox, a clever interface to maple). All results are not only numerical

but inexact, thanks to the rounding errors inherent in computer arithmetic. The

limitation to numerical computation can be seen as a drawback, but it’s a source of

strength too: MATLAB is much preferred to Maple, Mathematical, and the like

when it comes to numeric.

On the other hand, compared to other numerically oriented languages like

C++ and FORTRAN, MATLAB is much easier to use and comes with a huge

standard library.1the unfavorable comparison here is a gap in execution speed.

This gap is not always as dramatic as popular lore has it, and it can often be

narrowed or closed with good MATLAB programming. Moreover, one can link

other codes into MATLAB, or vice versa, and MATLAB now optionally supports

parallel computing. Still, MATLAB is usually not the tool of choice for maximum-

performance Computing.

6.2 SIMULINK:

Simulink (Simulation and Link) is an extension of MATLAB by Math

works Inc. It works with MATLAB to offer modeling, simulating, and analyzing of

dynamical systems under a graphical user interface (GUI) environment. The

construction of a model is simplified with click-and-drag mouse operations.

Simulink includes a comprehensive block library of toolboxes for both linear and

nonlinear analyses. Models are hierarchical, which allow using both top-down and

bottom-up approaches. As Simulink is an integral part of MATLAB, it is easy to

switch back and forth during the analysis process and thus, the user may take full

advantage of features offered in both environments. This tutorial presents the basic

features of Simulink and is focused on control systems as it has been written for

students in my control system

6.2.1 Sim Power Systems:

Sim Power Systems is a modern design tool that allows scientists and

engineers to rapidly and easily build models that simulate power systems. Sim

Power Systems uses the Simulink environment, allowing you to build a model

using simple click and drag procedures. Not only can you draw the circuit topology

rapidly, but your analysis of the circuit can include its interactions with

mechanical, thermal, control, and other disciplines. This is possible because all the

electrical parts of the simulation interact with the extensive Simulink modeling

library. Since Simulink uses MATLAB® as its computational engine, designers

can also use MATLAB toolboxes and Simulink block sets. Sim Power Systems

and Sim Mechanics share a special Physical Modeling block and connection line

interface.

6.2.2 Sim Power Systems Libraries:

You can rapidly put Sim Power Systems to work. The libraries contain

models of typical power equipment such as transformers, lines, machines, and

power electronics. These models are proven ones coming from textbooks, and their

validity is based on the experience of the Power Systems Testing and Simulation

Laboratory of Hydro-Québec, a large North American utility located in Canada,

and also on the experience of Ecolab de Technologies Superiors and University

Laval.

The capabilities of Sim Power Systems for modeling a typical electrical system are

illustrated in demonstration files. And for users who want to refresh their

knowledge of power system theory, there are also self-learning case studies.

The Sim Power Systems main library, power lib, organizes its blocks into

libraries according to their behavior. The power lib library window displays the

block library icons and names. Double-click a library icon to open the library and

access the blocks. The main Sim Power Systems power lib library window also

contains the Powerful block that opens a graphical user interface for the steady-

state analysis of electrical circuits.

Simulation Circuit Diagram:

Boost mode:

Output voltage:

Buck Mode:

Output Voltage:

Hardware Circuit Diagram:

R 1

1 k

R 2

R 3R 4

R 5

R 61 k

R 81 k

U 1

O P -0 7 C / 3 0 1 / TIQ 1

B D X3 7

Q 2

Q 3

D 1

D 1 N 1 1 9 0

C 11 n

0

FROM MICRO CONTROLLER

1K

100100

100

S

G500mA

230/12VMCT2E

R 1

1 k

R 2

R 3R 4

R 5

R 61 k

R 81 k

U 1

O P -0 7 C / 3 0 1 / TIQ 1

B D X3 7

Q 2

Q 3

D 1

D 1 N 1 1 9 0

C 11 n

0

FROM MICRO CONTROLLER

1K

100100

100

S

G500mA

230/12VMCT2E

Gate to source terminals from driver circuit is given to mosfet gate to source Terminals

Hardware Results:

Take Snaps from CRO