Posted on Feb 7, 2014

The constant current charging circuit which is composed of the three-port voltage stabilizer is as shown in figure 2-21. Because the electric potential difference of the LM317`s pin-1 and pin-2 is 1. 25V, if we ignore the shunting effects of R3, R1, LED, the potentiometer R2 can adjust the charging current value, the constant current value I=1. 25/R

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2. In actual use, the R2 always uses the 1W resistance. When the R2 is 25 ©/1W, the charging current of the battery is about 50mA. The charging indicator circuit is composed of the resistor R1 and LED, if we choose the appropriate value of R3, when the battery has the required charging voltage, the VT1 will cut off, the LED will turn off. This circuit can charge more than four No. 5 nickel-cadmium batteries. (View) The adjustable power charger circuit which is introduced in this article has the highest charge voltage of 12V, the maximum charging current is 200mA. The adjustable voltage range is 0-12V, the adjustable current range is 0-200mA, and it has the constant voltage, trickle charging mode. The circuit is as shown in figure 3-2. When the battery voltage rises to the set value, the circuit will stop operating. You can change the charging voltage by adjust the duty ratio of R2. When the voltage of the battery is full, the voltage-regulator diode VD6 punctures the conduction to trigger the conduction of the transistor VT, the green indicator light LED2 turns on, and the pin-4 of time-base circuit has the low level to stop the oscillation of the circuit, the pin-3 has no output voltage. (View) The voltage stabilization sampling and error amplification system is composed of the pin-1 and pin-2, the positive phase input port pin-1 inputs the 15V DC voltage which is rectified and output by the inverter sub-sampling winding,...

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