0-45V 8A DC switching power supply circuit

Today I recommended the 0-45V 8A DC switching power supply circuit is a circuit that is capable of higher common linear circuit but it has a lot of detail.

Special feature:
– Output voltage……….0-45V
– Output current continuous 8 hour at a lower voltage than 35V and 6A at 40V
– ripple and noise :5mVp-p at 6Ampere 13volts
:10mVp-p at 8Ampere 18volts
:40mVp-p at 8Ampere 35volts
-Minimum output current:….800mA
-Maximum output current:….8.2A
– Display while use over voltage that setting and while voltage no regulated
– Can cut off the output load without the wires
– Adjustable constant voltage such as 13.8V.

Basic working
Figure 1 is shown the simple circuit of this switching power supply. The transistor Q1 will serves as the on/off switch circuit, we control them by lighting connection. This controller circuit will control the Q1 to on/off circuit by the frequency 20KHz.

the basic of DC switching power supply
Figure 1 the basic of DC switching power supply

Both Q1 and D2 will be passed to a high current, this will work alternately. During the Q1 performance, the current is passed through C8, C9, L1 and Q1, When Q1 stop or open circuit Energy stored in L1 will evolve through D2 and C8, C9 in the same direction, makes the output voltage is constant on all times.

And, if the pulse that send to control Q1, have the low duty cycle range. The current flow through Q1 and L1 are too low,so the output is also low. Which the duty cycle of this pulse switching will have high or low value depending on adjusting the output voltage that.

How it works
Figure 2 is complete circuit of this switching power supply. IC5/4 is reference voltage booster circuit, which the output of IC5/4 will depending on adjusting VR3. This reference voltage from output of IC5 / 4 will send to pin 7 of IC3/2, to compare with the signal at pin 6 of IC3/2 that connected from IC3/1, which is 20KHz frequency ramp generator circuit.

the full circuit diagram of 0-45V 8A switching power supply
Figure 2 the full circuit diagram of 0-45V 8A switching power supply

IC3/2 will compare the voltage at both pins, if reference voltage has too much the output of IC3/2 will be a switching pulse (the square wave pulse) that has many duty cycle range. But if the reference voltage has less switching pulse value so low duty cycle as Figure 3

A comparison of the signals VP and VE

The pulse signal from the compare circuit will be sent to Q3 and Q4, Which is the buffer circuit to drive the LED in IC, that is the opto-isolator. It will detect the light as switching pulse signal then send to Q2 to Raise the signal. Next IC2/1 will set the signal waveform, then send to IC2/2-IC2/6. It drive the gate of Q1 that use as inverter in parallel to 5 pcs. To the current sufficient to drive the gate of Q1 up.

The switching of Q1 in sometimes will cause the voltage brief moment at leg drain may be higher than the source. As a result of the inductor coil L1. Thus, so the D1 and ZD3 to prevent this voltage, which may cause the FET crash. The limited voltage circuit while only 75 volts. This means that, If the voltage does not exceed 75V. This voltage would drop all ZD3, No effect to the circuit. If momentary voltage exceeds 75V, it can trigger the effect of making it through Q1 D1 conduct another stroke should not be working.

IC4 /1 and IC5/1 per share, to serve conditional no regulated. That IC4 / 1 will compare voltage between pin 6. Which is switching pulse and steady voltage at pin 7. When the negative pulse come in, output of IC4/1 will high, can through to charge C23 at pin 2 of IC5/1. And when output of IC4/1 lower the capacitor C23 at pin 2 of IC5/1 will higher up. The LED1 will no display, if Q1 get trigger gate at all times or Irregularities. The output voltage of circuit will lower in unregulated form. Capacitors C23 at pin 2 of IC5 / 1 are discharged, Until the output of IC5 / 1 high up, LED1 is lighted indicator non regulated.

Normally, the switching power supply output is not constant. If the Supply Current is very low. Or while no load. Thus, you must have the load of the circuit. To apply current lowest at all times.

While the output voltage up to 10volts, R24 and R43 connected in parallel 2 pcs, Will act as a load to the circuit. When voltage ranges from 5V to 10V, the output of IC4/2 will be the compare circuit will has high current cause Q6 works. R40 are connected to the load to the circuit and when output voltage lower than 5volts The output of IC4/3 will high instead makes Q5 works and R41 will be to provide a load of circuit.

IC3 / 3 acts to reduce the output current. When detected load use current over than 9 Amperes, will cause voltage across R1 and R2 are more valuable (more than 0.45 volts)As a result, output of IC3 / 3 low, and to pull the reference voltage at pin 7 of IC3 / 2 to IC3 / 2 to produce the switching pulse with a lower duty cycle as a consequence, the output dropped to a value less than 2A.

During the current over than the value set by the VR1, output of IC5 / 3 would be lower, according to the IC3 / 2 through D8, Make output IC4 / 4 higher. LED2 will show whether the current exceeds a preset.

The PCB layout

components-layout-of-45V-8A- Switching power supply
The components layout of this projects

We sorry not clear how to build it.

Parts you will need
0.25W 5% Resistors
R1, R2, R42, R43_______1K 5W
R3___________________390 ohms 0.5W
R4___________________270 ohms
R5, R11, R21, R32, R45__1K
R6, R50_______________100 ohms
R7, R34, R35___________470 ohms
R8, R17_______________6.8K
R9, R18, R57___________47K
R10, R30______________18K
R12, R14, R15, R16_____100K
R19, R27, R28, R29, R54_100K
R13, R23, R24, R26______10K
R22___________________270 ohms
R25, R30, R37, R38, R39__2.2K
R33, R46_______________22K
R40___________________39 ohms 5W
R41___________________10 ohms 5W
R48___________________820 ohms
R51, R52_______________0.1 ohms 5W
R53___________________47 ohms
R55___________________220 ohms
VR1, VR3______________10K (B) Volume
VR2___________________500 ohms___trimpots
VR4, RV5_______________50K___trimpots

C1 – C5__________4,700uF 50V Electrolytic
C6, C7, C15, C23__0.1uF 50V Polyester
C26, C28, C29_____0.1uF 50V Polyester
C8, C9, C12, C14___100uF 50V Electrolytic
C10, C21, C22, C24_1uF 16V Electrolytic
C11______________0.001uF 50V Polyester
C16, C17_________0.1uF 25V Polycarbonate
C18______________1,000uF 25V Electrolytic
C19, C25, C27______10uF 16V Electrolytic
C20_______________820pF 50V Ceramic

BD1______________35Am 100V
D1, D3-D6_________1N4004
IC2________________74C14 or CD40106
IC3, IC4____________LM339
LED1, LED2_________Red LED
Q5, Q6_______________BC639
ZD1_________________15V 3W
ZD2_________________4.7V 1W
ZD3_________________75V 1W
F1______ Fuse 7.5A
L1, L2___ See circuit

L1____Toroidal core, Outside diameter of 46.7 mm, Rounds in 24.1 mm, 18 mm thickness; L1 is 10 turns of 17 AWG (1.2mm)
L2____Toroidal core, Outside diameter of 33 mm, rounds in 19.8 mm, 11.1 mm thickness; L1 is 5 turns of 17 AWG(1.2mm)

M1, M2__ 1mA Meter
S1___ON/ OFF 10A Switches
S2___ 3 leg, normally open pushbutton switch
S3___ 10A On/off switches
S4___2 way switch
T1___transformer toroidal core
220V, 35-0/35-0 V, 300 VA
T2___Transformer 220V 12.6V 150mA
Box,PCB, Wires, and more.

Note: we sorry this circuit not have full building guide.

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