GB1446689A - Integrated dc converter circuit - Google Patents

Abstract

1446689 Transistor pulse oscillator circuits ITT INDUSTRIES Inc 15 Oct 1974 [20 Oct 1973] 44569/74 Heading H3T [Also in Division H2] In a D.C.-D.C. converter in which current in an inductor L R is periodically interrupted by means of a complementary pair of transistors T1, T2, the base of the controlling transistor T2 being biased by means of a potential divider comprising a resistor R1 connected between the collector of the switching transistor Tl and the base of T2 and a switching device, such as transistor T3 connected between the base of T2 and the emitter of T1. The switching device T3 is arranged to be turned off by the emitter current of T1 before it reaches its maximum, so that a lower value resistor R1 may be employed, thus allowing the circuit to be integrated. As described T1, T2 are initially conductive, so that a current is allowed to build up in the inductor L R . When the current reaches a value determined by the combined current gains of T1, T2, the current in T2 tends to become reduced, giving a cumulative turn off of both transistors. The resulting overswing in the inductor is rectified at D and charges capacitor C. When the overswing reaches 0À6 v., T5 is turned on, turning on T6 and turning off T3. A further transistor T7 may be included to facilitate dissipation of stored charge. In Fig. 2 (not shown) T5 ... T7 are omitted and T3 is turned off by the rise in voltage across R4. In Fig. 4 (not shown) a further transistor is connected as shown in broken lines but has the base connected to a potential divider across the base/emitter path of T1. This arrangement tends to make the output voltage independent of the input.