It is an electronic device, which rectifies the mains voltage, for feeding a

modulated wave switch circuit, a frequency of 65KHz, and obtaining

through a continuous transformer rectified current value of 12V. This out-

put voltage is regulated current and voltage in the oscillator circuit and

control circuits and overload protection on output.

Printed circuit board

Power Supply Device

Description of the circuit

The characteristics of the source, are up to 130 W with a voltage control PWM ( pulse width mo-dulation ) , two levels of protection, overvoltage and other overload protection thermal hystere-sis , with a burst smooth and safe on auto restart after removal of the overload. Feature low po-wer consumption when the source is in standby mode, to meet the energy saving regulations . A brown-out function , which protects the SMPS , when the level of rectified input voltage is below the normal minimum level specified for the system.

The IC 30 has an internal switching frequency of 65KHz . The regulations of the loop current and voltage are performed with a network of external components, which facilitates control and an internal reference of 3V ± 2% to ensure the protection and precision of the output control .

Control is continuous mode ( CCM ) under average current and discontinuous (DCM ) when the load is a few milliamps.

The continuous monitoring mode ( CCM) , is performed by integrating a reference signal at the output of the rectifier input network .

Also a voltage divider from the rectified voltage is introduced as a reference for controlling a vol-tage drop in the input network .

The signal generated by the IC 30 is inserted into the base of transistor Q31 , which in turn con-trols the power transistor Q1 , which amplified signal is rectified by diode D1 .

The modulated signal converter circuit is generated in the IC 331, with two levels of protection when there is an overload and an automatic start after disposal .

Proportional to the voltage of the rectified input signal is input to the IC34 and a signal proportio-nal to the load current at the IC31 , the latter generates a pulse whose width is changed , based on the parameters detected by the voltages and input currents.

The source output is 12V DC , which are obtained from the rectification of the signal at the trans-former secondary T1E by rectifiers CR101 and CR102 power that once we get the filtered DC voltage .

It has a thermal hysteresis control rectifier through a detector circuit with a thermistor, which is controlled by the comparator circuit IC471 and IC333 photo coupler .

The output of 12V , is controlled voltage and current in the circuit of IC432 . Safety devices plug ( PTC ) and a detection voltage 8V under overload , are located in each of the outputs

RECTIFIER

The source feeds the network with an AC voltage between 110 and 220 V. This first section is

comprised of a fuse and a NTC thermistor , which protects all excessive voltage source from the

network and its function is cut to protect this primary stage .

The NTC1 thermistor is an electronic component that lowers your resistance to temperature rise.

Its function at this stage of the source is lower resistance allowing the entry of more amount of

current in the event of overheating of the primary stage , which is the result of over- supply requi-

rement . This decrease in resistance is obviously a limit, which depends on the value of the ther-

mistor and the limit imposed by the fuse. Faced with a sudden increase in the supply voltage ,

the fuse is cut away.

In the primary stage of the source, this section consists of a coil - capacitor network whose fun-

ction is to eliminate stray radiation that can enter the stage of switching power in the grid.

Without this section , radiation would enter the network , creating interference that would affect

the line of AC power and electrical and electronic devices plugged in to it .

The next stage of the source , is formed of a bridge rectifier ( B1 ) . Which is a set of four diodes

grouped in a package . The function of this stage is to convert the alternating current waveform

coming from the network in positive and negative phase in a purely positive pulsing signal.

In making the conversion , the output voltage of the diodes is 1.41 that of the input. If from a 220

volts AC , a bridge rectifier output approximately 310 volts is obtained received .

POWER CIRCUIT

The current wave has a positive and negative phase (alternating current). This stage converts the

wave into a continuous signal will always be positive for one of the poles, "wave rectified."

This rectified, but is continuous and positive for a pole wave is irregular, very sharp maximum

and minimum peaks.

At this stage of the source to the output of the rectifier bridge is an electrolytic capacitor C4 which

together with the inductor L1E are responsible for filtering or eliminate the ripple signal.

SOURCE CONTROL

The IC30, controls the source for CCM (Continuous Mode Control) mode, while operating at an

average load current and in DCM (Discontinuous Mode Control) when the load is low or no load.

The control signal is supplied to the base of Q31, which in turn feeds the gate (g) of the power

transistor Q1-MOS FET.

This signal is controlled by a resistive network connected to the rectification stage and the source

that provides the data to modify the parameters of the output signal from pin 8.

The IC30 is fed by 14V in the pin 7, the IC has a startup control, when it exceeds 11.8 V, with the

proviso that the pin 6 (VSENSE) above about 0.6 V and the pin 4 (VINS), exceeds 1.5 V. With

these two conditions, the IC begins to operate. With lower power of 11 V, the IC stops working.

The IC30 , offers protection from voltage drops in the network (Brown -out ) , which occurs when

voltage does not exceed 85 Vac , this protection is made by a divider network that introduces the

reference signal on pin 4 ( VINS ) .

The IC has a protection against over voltage to a low voltage supply ( SOC ) and a current limiting

protection peak , cycle to cycle ( PCL).

Fault and overvoltage protection.

When the voltage of pin 6 ( VSENSE ) falls below 0.6 V , or the equivalent of the voltage after the

rectifiers fall by 20 % , which indicates that the voltage is insufficient, most are blocked the fun-

ctions of the IC supply voltage protection (OLP ) .

When the rectified output voltage , exceeds the nominal value by 5% , the over-voltage protection

(OVP ) is activated . This is implemented by a voltage detection pin 6 ( VSENSE ) with respect to

a reference voltage of 3.15 V. A pin 6 voltage exceeds 3.15 V immediately reduce the duty cycle

output , from a normal control loop voltage . This results in a lower input power to reduce the out-

put voltage . If the voltage on pin 6 is greater than 3.25 V signal output pin 8 is turned off immedia-

tely .

Over Current Protection

When the control signal is input on pin 3 (ISENSE) of IC30, is less than 0.75 V, over current con-

trol (SOC), which works by reducing the gain of the active duty cycle. When the voltage reaches

1.04 V, the protection of over current limitation (PCL) is activated.

Average current control

The signal input to pin 3 (ISENSE), results in average current flowing through the resistor R5, and

is compared to a signal generated internally by the IC at pin 5 (VCOMP) has an RC network ,

which provides the average reference voltage. The pulse width modulation takes place at the in-

tersection of the ramp signal with the average reference signal present on pin 5 (VCOMP)

The control signal pulse width modulated cycle begins at the Toff MIN phase and during 400ns

the signal VRAMP is discharged, and the cycle begins again when the ramp reaches the refer-

ence voltage Vc REF, the PWM pulse passes high level. This provides a relation ship between the

average current and pulse width modulated.

Control of output voltage

To deliver the source voltage and constant current, the IC 432 through internal operational and

control signals delivered by the source output (12V), establish a reference voltage that feeds the

IC32 photo coupler, which turn controls the reference signal in the control IC 31.

Con-

trol

Control oscillator power amplifier

The IC 31 is designed to generate a control signal that feeds the transistors Q52 and Q51, and is

entered on the primary transformer T2E modulator. It has a control signal current limit, which is

inserted into the pin 3 and pin 1 a comparison signal processed by the IC 34, the Q54 and Q53.

The photo coupler IC332, with a reference signal generated by the IC431 controls the operation

in steps starting from the source.

Signal generator oscillator power amplifier

The IC 331 generates the high voltage signal of the power amplifier formed by Q1 and MOS-FET

Q3 and Q4, this signal, one of its features is a slow starter, determined by the value of the capac-

itor C332, also has the auto regeneration device, then remove the cause of the failure.

The internal oscillator is set to 60 kHz and has a control over voltage on pin 5, depending on the

voltage that feeds a transformer winding T301E, when the voltage rectified by D331 exceeds 3V

for four consecutive times, control over voltage acts by disconnecting the internal oscillator, to

disable the MOS-FET power transistor Q1.

Output 12V / 10.7 Amp

The signal of the modulated wave, in the secondary of T1E, depending on the control parameters

of the previous stages, is rectified by the double diodes CR101 and CR102 and filter network

comprises L101E and C103 electrolyte, C104, C105, to obtain the 12V DC. An overvoltage tran-

sient protection is provided by the ZD1 component. Besides having another overload protection

provided by the PTC component and a sensor network made up, ZD208 ZD201 ... which turns off

the LED that indicates that the corresponding output is overloaded, when the voltage is below 8V.

The output has 8 connectors, each with a capacitive network filter for interference generated by

rectification of previous stages.

The output voltage is 12V DC voltage, with a total maximum current of 10.7 Amps.

Pcb viewed from the upper side components

Pcb copper side of the tracks, marked with colors tensions

Power and control

circuit

In this stage an almost

continuous signal at the

terminals of the filter ca-

pacitor C4, which sup-

plies the power switch-

ing section below, com-

prises a set of transis-

tors Q1, Q3 and Q4 as

well as power diodes

D1, D6 and D8 is ob-

tained .

POWER CIRCUIT

AC rectifier

Power control circuit and protections

PWM circuit

Output 12Vdc

and protection circuit

Primary Frecuency

and protection control

PWM control