CONSTANT-CURRENT CHARGING CIRCUIT

PURPOSE:To control two transistors so that the voltage between the emitter and the collector of one transistor may be equal to that of the other one even if there is a small difference in performance characteristic between the two transistors by connecting a constant-current control circuit between the stages of the two transistors and by connecting a circuit to hold a voltage between the emitter and the collector of each stage transistor constant between the emitter and the collector of each stage transistor. CONSTITUTION:Current from a source of d.c. power supply 5, which is kept in the constant-current condition by a constant-current control circuit 6, passes through transistors 3-1, 3-2 to charge a battery 1. The transistors are so controlled by constant-voltage control circuits 7-1, 7-2 that a voltage value between an emitter and a collector of one stage transistor may be equal to that of the other one. Consequently, the transistors are precisely controlled so that the voltage between an emitter and a collector of those transistors may be the same even if there is a small difference in performance characteristic between the two transistors.