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Assignment # 1 (Power Converter Design) Session: MSSE 2013-15

Muhammad Shafique (Ms-13-25864)

Assignment No. 1

EE-529 Power Converter Design

Session: MSSE 2013-15

Assigned on: 31-Jan-2014

To be submitted on: 03-Feb-2014

Instructor: Mr. Tanveer Abass

Student Name: Muhammad Shafique

Registration No. : MS-13-25864

Pakistan Institute of Engineering and

Applied Sciences (PIEAS)



Question No. 1 Study of switching characteristics of power diode [10A10 and PURG5060] in

simulation

Note: [Changed Components are used in Simulation]:

Due to unavailability of both above mentioned diode models in LTSPICE simulator and also on Internet, the device model is therefore changed to another one to perform this simulation. PROTEUS ISIS8 Simulator was used for simulation and the justification for the diode models used is as under

1- 10A07 was used instead of 10A10. It is selected because it was matched mostly to the properties of 10A10. 10A07 (Diodes Inc.) is a 1000V/10A/Silicon/3us diode.

2- 15ETH06 (International rectifier Inc.) was used instead of RURG5060. It is a trr=22ns/600V/10A diode. It was selected mainly because of its reverse recovery time.

Depending upon the unavailability of simulation models of required diodes, the above choices were made to fulfill the requirement.

Part-1:

Simulate the above listed diodes with an RL load by applying a square wave source of ±500V @ 1kHz and rise/fall time=1µsec. Load impedance should be 50Ω. Simulate the circuit for load time constant of 1µsec, 0.5µsec and 0.1µsec :

For a RL load impedance of 𝒁 = 50 ohms and time constant (𝑻), we can find the values of R and L by using following equations:

𝑅 (𝑂ℎ𝑚𝑠) = 𝑍

1 + (2𝜋𝑓𝑠𝑇) 2

And 𝐿 (𝐻𝑒𝑛𝑟𝑦) = 𝑅 ∗ 𝑇

The Circuit which was simulated is shown in Figure-1. In the circuits I have used the Free Wheeling Diodes because without them the response of Vd (Voltage drop across diode) and Id (Series current through diode) appeared to be oscillatory during the off cycle of switching signal (A sample waveform is shown ahead).

Now the values of 𝑅 (Resistance) and 𝐿 (Inductance) will be changed according to the required time constant (T) and the particular values will be calculated using the above given two equations. Rest of the circuit was made according to the required configuration.



Figure-1: Circuit schematic used for simulation.

PART-2:

You are expected to measure voltage and current waveforms for the diodes as function of

time (on the same graph for comparison):

A- Time Constant (𝑇) = 1usec

The result of simulation for this is shown below (R = 50 ohms and L = 50uH were used):

a. Response of 10A07 diode at rising edge:



b. Response of 10A07 diode at falling edge:

c. Response of 10A07 diode at falling edge [Without Free Wheeling Diode]:

d. Response of 15ETH06 diode at rising edge:



e. Response of 15ETH06 diode at falling edge:

B- Time Constant (𝑇) = 0.5 usec

The result of simulation for this is shown below (R = 49.99 ohms and L = 24.99uH were

used):





c. Response of 15ETH06 diode at rising edge:

d. Response of 15ETH06 diode at falling edge:

C- Time Constant (𝑇) = 0.1 usec

The result of simulation for this is shown below (R = 49.99 ohms and L = 4.99uH were

used):





c. Response of 15ETH06 diode at rising edge:

d. Response of 15ETH06 diode at falling edge:



Observation:

From the response curves it can be seen that the Reverse Recovery Time of 15ETH06 is too less/sharp than that of 10A07 and this is obvious because 10A07 is a simple rectifier diode while 15ETH06 is the Fast diode (trr = 22 ns)

As the time constant is varied the transient response becomes sharp while some amplitude increase of reverse recovery current (Idrr) overshoots is also observed for the case of 10A07 but decrease in reverse recovery current (Idrr) overshoots is observed for the case of fast diode (15ETH06).

PART-3:

Measure reverse recovery current and time and try to correlate it the values given in the

datasheet for PURG5060/15ETH06 Fast diode (trr = 22ns) :

Since I have used 15ETH06 instead of RURG5060 in our simulation so I am using the data, given

in the datasheet of 15Eth06, for the comparison:

According to datasheet:

According to datasheet for the following test conditions @ IF = 15 A, VR = 390V (Reverse

voltage),d IF /dt = 800 A/us then the trr = 51 ns and Irrm(Peak reverse recovery current ) =

20A.



Findings from the simulation response:

The corresponding condition of our simulating circuits are: @ IF = 10 A, VR =500V,d IF /dt = ??

A/us.

The corresponding trr = 1-2 ns (approx.) for our circuit and the Irrm = -4A (approx.)

Apparently there is very bad correlation b/w datasheet value and simulated values.

================Question # 1 Ends Here================



Question No. 2 Study of switching characteristics of power MOSFET[IRF540] in simulation

Note about Simulation:

PROTEUS ISIS8 Simulator is used using the N-Channel MOSFET IRF540 as a Power Switch.

PART-1:

Simulate the above listed MOSFET with a resistive load of 10Ω by applying a DC source of 50V

and a gate signal of appropriate amplitude @ 1kHz-10kHz.

Vgs or gate drive signal was determined by the maximum load current and the MOSFET

characteristic curves. I used the VgsON= 15 volts @ Idsmax = 5 A (approx).

Figure-2 Shows the circuit used for the simulation of this question:

Figure-2: The circuit schematic used for simulation of question # 2.



PART-2:

You are expected to measure voltage and current waveforms for the Switch as function of time (on

the same graph for comparison) for a single frequency @5kHz:

It is shown below:



Part-3:

Measure power dissipation at different frequencies and present your finding as a graph between

power dissipation and frequency of switching. Compare the results with your calculation you have

done previously for power dissipation :

A- Power Dissipation curve at Fs = 1 K Hz [Falling Edge i.e ON to OFF]:



B- Power Dissipation curve at Fs = 5 K Hz [Falling Edge i.e ON to OFF]::



C- Power Dissipation curve at Fs = 10 K Hz [Falling Edge i.e ON to OFF]::

According to the study done in the class/lectures, the power dissipation in switch is approximately

directly proportional to the frequency of switching but PROTEUS ISIS8 only shows the slight variations in

power dissipation at the transitions only (ON to OFF and ViceVersa) while the ON-State Power

Dissipation remained almost constant over the variation of switching frequency.

Unfortunately, to the best of my knowledge, in PROTEUS ISIS8 there is no any working tool to measure

the average power dissipation /average voltage/average current of the switch/component. So I drew

the power curve (w.r.t time) for each frequency but the comparison of curves didn’t show the power

dissipation variations if frequency is changed. I tried to trouble shoot it but It could not give the

quantitative measure of variations in power dissipation.

But Ideally and Practically the average power dissipation (Pd) of switch will vary w.r.t switching

frequency and the variations will be governed by the positive slope of approximately constant value.

====================Question # 2 Ends here====================

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Documents

response of 10a07 diode

response of 15eth06

1000v10asilicon3us diode

22ns600v10a diode

power converter design

muhammad shafique ms

mentioned diode models

load time constant