Circuit Analysis Of Two - Stage Constant Current Charger

- Jun 02, 2017 -

1. Power supply circuit and charging circuit

23V by V1 ~ V4 bridge rectifier after BG1, BG2 composed of constant current circuit and trigger circuit power supply, when the trigger trigger trigger SCR turn on, 40V in the positive half cycle range of the battery pulse constant current charge.

2. Trigger circuit and charge constant current control circuit

Trigger pulse generated by the BG2 relaxation oscillator, BG1 charge constant current control circuit. Constant current principle is as follows: With the battery charge, the voltage increases, the charging current decreases, R7 on the voltage is reduced, so that BG1 base potential drop. BG1 emitter potential is fixed, so BG1 collector current increases, so that the circuit through the BG1 on the C4 charge to speed up. Trigger pulse ahead of time. SCR conduction angle increases, so the battery charge current increases, that is, to maintain the original charge current constant.

3. Two-stage charging conversion circuit and automatic shutdown circuit

The machine does not work when there is no battery. After the battery is connected, the BG3, BG4, BG6, BG7 are turned off, BG5 and BG8 are turned on, and K1 and K2 are connected because of the low initial voltage (14.5V or less) K1-2, K2-2 disconnect, to prevent the battery voltage after the BG8 cut off; ③ K1-1 closed, RP2 is short-circuit, then the charge is The first stage of charging. When the battery voltage of 14.5V, the BG3 saturation conduction, BG5 cut off, K1 release, K1-1 off, RP2 string into the BG1 base circuit, C4 charging slow, trigger pulse lag, the SCR conduction angle decreases The So the battery charge current decreases, into the second stage of charge, when charging to 16V, BG6 saturation conduction, BG8 cut-off. K2, KCJ have been released, the circuit is turned off.


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