Four-channel single-cell battery independent charging fully automatic charger circuit diagram

It adopts 10 hours of constant current charging, which is more convenient to use. The circuit is as shown in the figure.

After the mains power is stepped down by the secondary of transformer T, one channel is rectified by VD1, filtered by R1 and C1, and stabilized by VD4, and then filtered twice by R2 and C2 to output a stable voltage of 4.6V for four-channel control circuits; the other channel is routed by VD2 After rectification, four half-wave pulse currents are provided for charging. Only one of the control circuits is shown in the figure, the other three are the same. The control integrated block uses four comparators LM339, its non-inverting input terminal is a stable voltage of 1.46V, which is provided by the 1.9V stable voltage obtained from R3 and the power indicator light-emitting diode LED1 through R4 and R5 through R12; the comparator The inverting input terminal reflects the changing voltage of the charged battery . Since the input terminal of the comparator does not consume current, there is no voltage drop on R9 and R12, and the comparator can truly reflect the magnitude of the voltage being compared. When the voltage of the battery being charged is low, the potential of the non-inverting input terminal is high, controlling the V1 tube to conduct, forming a charging loop. At the same time, the charging indicator LED2 lights up; when the voltage of the charged battery reaches 1.46V, the comparator outputs a low level, V1 is cut off, and the charging circuit is cut off. At this time, the battery voltage begins to fall back. Due to the influence of the VD3 and R11 branches, the comparison The comparator has a certain hysteresis, which can prevent the comparator from oscillating. Only when the battery voltage drops significantly, the comparator outputs a high potential again to turn on V1 and resume charging. In this way, the battery is in the intermittent charging state, and LED2 flashes. As the battery power increases, the intermittent time becomes longer and longer, and the frequency of LED2 flashing becomes lower and lower. Finally, when it remains off for a long time, it means that the power is sufficient.

R10 is the comparator output load resistor. R8 can prevent out-of-control conditions when the battery contact is poor. R4 can adjust the comparison voltage threshold of the four-way comparator, and can also fine-tune itself according to the age of the battery being charged. The charging current decreases as the charging voltage increases, and the measured maximum is 110mA. The current size can be fine-tuned by changing R6.