ES361058A1 - A device suitable for charging a storage battery from an alternating power source - Google Patents

Abstract

Battery-charging circuit comprises an A.C. source, an impedance which limits the charging current, and a controlled rectifier, the firing angle of which is regulated in accordance with the battery voltage. In the circuit shown in Fig. 1, the battery B is charged from a mains transformer Tr by way of a limiting inductance L1, a rectifier bridge Rd, and a thyristor Th. The firing of the thyristor is controlled by a synchronized power supply system comprising transistors T10 and T11, and a pulse generator including transistors T2 and T3 and a capacitor C1 The emitter of transistor T10 is held at a fixed voltage derived from a secondary winding S1 of the transformer Tr, and when the output of the bridge Rd reaches a preset value each half-cycle, the transistor T10 is biased on and in turn switches on the transistor T11. This applies a steady voltage to the transistor T2 which charges up capacitor C1 until a unijunction transistor T1 breaks down, whereupon the capacitor discharges and applies a firing pulse to the gate of thyristor Th. A train of such pulses will be supplied during the period that transistors T10, T11 are conducting. The firing angle of the thyristor, i.e. the delay before the arrival of the first pulse, is determined by the rate of charging of capacitor C1, controlled in turn by the biasing of transistors T2 and T3. A voltage representative of the battery voltage is derived from a potential divider R8-R12, and this is compared with a reference voltage from a Zener diode Dz3 by transistor T3 in such a way that the firing delay varies inversely with the battery voltage. Temperature dependent resistors CTN, CTP, having respectively negative and positive temperature coefficients, regulate the charging current according to the battery temperature. Auxiliary devices, Figs. 3 and 4 (not shown), may be connected to the circuit of Fig. 1, and comprise means for automatically charging the battery more rapidly after mains failure. During any period of such failure, a secondary accumulator is charged by the battery B, and its subsequent discharge raises the main charging rate. A further device for increasing the charging rate when the battery voltage has dropped substantially due to heavy loading may also be connected.