Friday, October 31, 2014
Universal Battery Charger Battery charger for general purpose usage Universal Battery Charger circuit diagram The chargers output voltage is adjust
Universal Battery Charger
Power transistors Q1 and Q2 are connected as series regulators to control the battery chargers output voltage and charge-current rate. An LM-317 adjustable voltage regulator supplies the drive signal to the bases of power transistor Q1 and Q2. Potensiometer R9 sets the output-voltage level. A current sampling resistor, R8 (a 0.1 ohm/5W unit), is connected between the negative output lead and circuit ground. For each amp of charging current that flows through R8, a 100mV output is developed across it. The voltage developed across R8 is fed to one input of comparator U3. The other input of the comparator is connected to variable resistor R10.
As the charging voltage across the battery begins to drop, the current through R8 decrease. Then the voltage feeding pin 5 of U3 decreases, and the comparator output follows, turning Q3 back off, which completes the signals circular path to regulate the batterys charging current.
The charging current can be set by adjusting R10 for the desired current. The circuits output voltage is set by R9
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