220v AC is filtered by T0 bidirectional filter to suppress interference, D1 is rectified into pulsating DC, and then filtered by C11 to form a stable DC of about 300V. U1 is a TL3842 pulse width modulation integrated circuit. Its 5 pins are the negative pole of the power supply, 7 pins are the positive pole of the power supply, and 6 pins are pulse output to directly drive FET Q1(K1358). The 3 pins are limited by a large current. Adjusting the resistance value of R25(2.5 ohms) can adjust the large current of the charger. The 2 pins are voltage feedback, which can adjust the output voltage of the charger. 4 feet external oscillation resistor R1, and oscillation capacitor C1. T1 for high frequency pulse transformer, its role has three.

It is to reduce the pressure of high voltage pulse to low voltage pulse.

The second is to isolate the high voltage to prevent electric shock.

The third is to provide working power for uc3842. D4 is a high-frequency rectifier tube (16A60V), C10 is a low-voltage filter capacitor, D5 is a 12V zener diode, U3(TL431) is a precision reference voltage source, and U2 (optocoupler 4N35) is used to automatically adjust the charger voltage. Adjusting w2 (trimming resistor) can fine-tune the voltage of the charger. D10 is the power indicator. D6 is the charging indicator.

Electric car charger schematic diagram

R27 is the current sampling resistor (0.1 ohms, 5w). Changing the resistance value of W1 can adjust the inflection point current (200-300 mA) of the charger to float. When power is applied, C11 has a voltage of about 300v. This voltage is loaded all the way to Q1 via T1.

The second way passes through R5,C8 and C3 to reach the 7th foot of U1. Force U1 to start. The 6 pins of U1 output square wave pulses, Q1 works, and the current goes to the ground through R25. At the same time, the T1 secondary coil generates an induced voltage, which provides reliable power to U1 through D3 and R12. The voltage of T1 output coil is rectified and filtered by D4 and C10 to obtain a stable voltage. This voltage is all the way through D7(D7 plays the role of preventing the battery's current from flowing back into the charger) to charge the battery.

Electric car charger schematic diagram

The second route passes through R14,D5 and C9 to provide 12V working power for LM358 (dual operational amplifier, 1 pin is power supply ground, 8 pins is power supply positive) and its peripheral circuits. D9 provides a reference voltage for LM358, which is divided by R26 and R4 to reach the second leg and the fifth leg of LM358. During normal charging, there is a voltage of about 0.15-0.18V at the upper end of R27. This voltage is applied to the third leg of LM358 through R17, and a high voltage is sent out from the first leg. This voltage passes through R18 all the way, forcing Q2 to turn on, D6 (red light) to light up, 6 pins of LM358 are injected into the second way, and 7 pins output low voltage, forcing Q3 to turn off, D10 (green light) goes out, and the charger enters the constant current charging stage. When the battery voltage rises to about 44.2V, the charger enters the constant voltage charging stage, the output voltage is maintained at about 44.2V, the charger enters the constant voltage charging stage, and the current gradually decreases. When the charging current is reduced to 200mA-300mA, the voltage at the upper end of R27 drops, the 3-pin voltage of LM358 is lower than the 2-pin, the 1-pin output low voltage, Q2 is turned off, and D6 is turned off. At the same time, 7 pins output high voltage, which makes Q3 conductive and D10 light up. The other way through D8,W1 to the feedback circuit, so that the voltage is reduced. The charger enters a trickle charge phase. 1-2 hours after the end of charging.