GB1098358A - Improvements relating to battery charger circuits - Google Patents

Abstract

1,098,358. Battery charging systems. WESTINGHOUSE BRAKE & SIGNAL CO. Ltd. Sept. 7, 1966 [Sept. 8, 1965], No. 38354/65. Heading H2H. [Also in Division G3] A battery charging circuit includes A.C. input terminals 5, 6; a controlled rectifier bridge including diodes 1, 2 and thyristors 3, 4; output terminals 11, 12 for connection to the battery (not shown) under charge; resistors 8, 9, 10 for sensing the charging current; a sensing circuit including a voltage divider 14, 15, a resistor 16 and a transistor 18 associated with a diode 13 and a capacitor 20 for detecting the battery charging voltage; and a controller 17 to which are applied signals from the current and voltage sensing circuits and which provides triggering pulses for the thyristors 3, 4, in a suitable manner to maintain a desired charging characteristic for the circuit. The arrangement is such that in general the battery is charged first at constant current in dependence upon the current control signal and then at a constant floating voltage of VI (see Fig. 2) when the voltage control signal supersedes the current control signal; however, when the battery voltage first attains the value VI, at the point B of the curve shown in Fig. 2, the voltage signal to the controller 17 is modified by the action of transistor 18, the base of which is connected to the resistor 10 carrying the charging current, in such a manner that the thyristors 3, 4 are controlled to allow the battery voltage to rise first to a predetermined value V2 before falling again to the voltage VI so that the charging characteristic of the circuit assumes the form BAC, Fig. 2, there being a controlled decrease in charging current over this range.