DE2402182

1421083 Battery charging systems using DCDC converters MATSUSHITA ELECTRIC INDUSTRIAL CO Ltd 17 Jan 1974 [19 Jan 1973 20 April 1973 16 May 1973 (2) 5 Dec 1973] 02163/74 Headings H2H and H2F [Also in Division H3] A system for charging a battery from an A.C. power supply by way of a transistor D.C. to D.C. converter comprises means for rendering the converter inoperative and thus to terminate charging when the battery reaches a predetermined state of charge. A battery B is charged from an A.C. source a, b by way of a rectifying diode D 1 , a converter comprising a transistor Tr 1 and a transformer T having a primary winding nc in the collector circuit of the transistor Tr 1 , a feedback winding nb connected to the base of the transistor and a secondary winding ns the output of which is rectified by a diode D 2 to charge the battery. When the battery B is sufficiently charged the potential at the mid-point of a divider R 2 , R 3 becomes such that transistor Tr 2 turns on so turning on transistors Tr 3 , Tr 4 , the turn-on of transistor Tr 4 connecting the base of transistor Tr 1 to its emitter whereby the transistor Tr 1 ceases oscillation so terminating the battery charging process. The turn-off of transistor Tr 1 may be enhanced by connecting a diode in its base or emitter circuit and the connection of a diode between the emitters of transistors Tr 1 , Tr 4 prevents interaction between the A.C. source and the secondary side of the transformer T. If desired the converter may comprise a pair of transistors operating in a push-pull blocking oscillator mode. In order to provide full electrical isolation between the secondary and primary sides of the transformer T the connection between the transistors Tr 4 and Tr 1 may include a photo-electric element, an electromagnetic relay or a thermo-electric element. An indicatoring lamp may be provided to indicate that charging is taking place.