Electric bicycle battery charger circuit

1. Generation of main charging voltage and auxiliary power supply voltage: IC1 and peripheral components form a flyback power supply to provide the main power supply for the circuit. IC2 only uses three sets of comparators to output the main charging voltage of 48V and the auxiliary power supply is also 16V.

2. Waiting state: The red power indicator LED1 is always on; when waiting to charge, the voltage of the detection resistor R27 drops to 0V. Therefore, the D group comparator (14) pin outputs a high level. The green light of the two-color LED2 is turned on; the high level of the (14) pin makes the A comparator pin 1 output a low level, and the red light of LED2 is turned off. At the same time, Q2 is turned off, and the fan does not rotate; the C group comparator pin 8 outputs a high level. The diode D9 is turned off and plays an isolation role. Then, the signal fed back to the high-voltage circuit by the optocoupler IC3 is high impedance, causing the high-voltage circuit to oscillate weakly in the waiting state.

3. During charging: The detection resistor R27 generates a voltage drop due to the voltage at the battery terminal. The voltage is sampled by R24, amplified and compared by the D comparator, and then flipped. Then the (14) pin outputs a low level, making the green light of LED2 off; at the same time, the low level of the (14) pin flips the A comparator, and its ① pin outputs a high level. LED2 lights up red, and Q2 is turned on, and the fan is powered to rotate: the C comparator keeps outputting a low level, so that charging can operate normally.

4. Charging saturation: When the battery is charged to saturation, the voltage drop of R27 rises to the set value, and the C group comparator flips, then the ⑧ pin outputs a low level, D9 is turned on, and the potential of IC4 (3) pin is pulled down. The negative electrode potential of the optocoupler IC3 light-emitting tube is pulled down. The photosensitive tube in the optocoupler is deeply turned on, and the charging saturation signal is fed back to the high-voltage circuit, controlling the oscillation of the high-voltage circuit to enter a weak state, so that the battery stops charging or floats; at this time, the D comparator flips, and the (14) pin outputs a high level. The green light of LED2 is turned on, and the A comparator ① pin outputs a low level, the red light of LED2 is turned off, and the fan stops rotating, indicating that the charging is completed (automatic control is realized, and it has the function of not requiring personnel supervision).