Switching battery charger circuit diagram

The charger uses the pulse width modulation dedicated IC UC3842 with excellent performance as the control core. The constant current control uses a single power supply dual op amp LM358. The power adjustment uses 4 high-power tubes in parallel. It can charge 12V~48V batteries and has a rated charging current of 10A. Because the circuit works in a switching state, the overall efficiency of the machine is high.
The mains power is reduced to 70V by T1 and then rectified and filtered by Q1 and C1. It forms the main charging circuit through the drain source of the battery, field tube and R12; 15V is rectified and filtered by Q2 and C2 to provide working power for the whole machine. IC1 is a pulse forming and pulse width modulation circuit, IC2 is a constant current control sampling process, and a voltage stabilizing circuit composed of R5, D2, and C7 provides power for IC2. The power supply of IC1 is input from pin ⑦, pins ② and ① are the positive and negative input terminals of the internal operational amplifier, the constant current control level is input from pin ②, pin ③ is the overload protection input terminal, pin ④ is the clock oscillation terminal, and the oscillation frequency f=1.8/C4?R2, the local oscillation frequency is about 12kHz, pin 6 is the pulse width modulation output, and the modulated pulses are injected into the grids of the four field tubes through the anti-vibration resistors (R14, R16, R18, R20). pole, the modulated pulse width is used to control the conduction time of the field tube, that is, the voltage at the output terminal is changed to control the output current. The pulse width of pin ⑥ is controlled by the voltage of pin ②. The higher the voltage of this pin, the narrower the pulse, and vice versa. The wider. ⑧Pin is the 5V reference power supply. IC2 is a dual op amp LM358. The voltage on R12 is sent to the non-inverting input terminal ⑤ pin through R8. After amplification, it is output from ⑦ pin to ② pin of IC1. IC2 ⑥ pin is the current regulation control terminal. D3 is a freewheeling diode. Its function is to provide a discharge circuit for L1 when the power tube is turned off to prevent the peak of L1 from breaking down the field tube. L1 is connected in series in the charging circuit to buffer the charging current. W1 is the current limiting adjustment potentiometer. The charging current is larger when the center tap is turned to the right, and smaller when turned to the left.
The capacity of transformer T1 should be greater than 600VA, and an iron core of 40mm×100mm can be used. The primary is wound with 310 turns of ∮1.00mm enameled wire, and the secondary is wound with 100 turns of ∮2mm enameled wire. Q1 uses a 200V, 25A full bridge, and four 400V 15A power control field tubes are used in parallel. Pay attention to the heat dissipation area to be sufficient, and the gate connection to be as short as possible. The source resistor R12 is a 5W non-inductive resistor, or three 5cm long 2kW can be used. electric stove wire instead. D3 uses three fast recovery diodes greater than 200V 8A connected in parallel, and the heat dissipation area is not less than 50mm×100mm (material thickness 4mm). L1 uses an EE42 magnetic core, with 8 strands of ∮0.57mm enameled wire wound in parallel and 10 turns. An insulating plate is used to fill a gap of 0.5mm between the cores, and it is sealed with epoxy resin. Other components are selected according to the figure.
The adjustment of this machine is simple. Adjust W1 to the far left as shown in the figure, connect the 48V battery, turn on the power, finely adjust W1 to make the ammeter A to 10A, use a digital multimeter to measure the voltage at both ends of R12, adjust R11 so that the voltage at both ends of W1 is equal to R12 Just the voltage at both ends. If there is no current output, first use a multimeter to measure the DC voltage on pin ⑥ to see if there is voltage (usually a few volts). If there is no voltage, disconnect R3 and then check whether the 5V voltage at pin ⑧ is normal. Otherwise, IC1 should be replaced. Then measure the voltage of IC1② pin, which is usually around 2V. Once the voltage is normal, the machine can be used. As long as the transformer capacity of this machine is sufficient, the charging current can be expanded to 15A by adjusting R11. Other components do not need to be modified, but the heat dissipation area of ​​the adjustment tube needs to be increased.