GB799154A - Improvements in or relating to inverter circuits employing transistors - Google Patents

Abstract

799,154. Converting. MULLARD RADIO VALVE CO., Ltd., July 16, 1956, No. 22005/56. Class 38 (2). [Also in Group XL (c)] A D.C. voltage is obtained by rectifying the output of a push-pull inverter oscillator comprising two transistors of the type having a current gain less than 1, each having its emitter collector path connected in series with the primary winding of a transformer across a D.C. supply and a regenerative feedback path coupling its collector-emitter circuit to its collectorbase circuit, means being provided for supplying a steady forward bias to at least one of the emitter base circuits sufficient to ensure starting of oscillation and for deriving a steady voltage by full-wave rectification of the output of the oscillator for counteracting the forward bias when the oscillator is in operation. The Figure shows a push-pull arrangement of alternately conducting junction transistors having primary windings P1, P2 in their collector circuits secondary windings connected to a full-wave rectifier DO and regenerative feedback windings F1, F2 coupled to the respective primary windings. The two pairs of windings are coupled together either by winding them on a common core (as shown) or by connecting in parallel secondary windings of the transformers. In operation, one transistor conducts permitting current to build up in the corresponding primary winding, the transistor being maintained conducting by the feedback winding. The increase of current continues until the core of the transformer saturates when the feedback rapidly decreases and the transistor cuts off. The second transistor then becomes conductive causing the current in it to build up in a similar way and eventually to trigger the first transistor. A negative starting bias is applied to the transistor base electrodes through a potentiometer chain R1-R4: and this is counteracted when the circuit is in operation by rectifying the output oscillation by means of rectifiers D1. and D2 and applying the rectified voltage to the point j in the potentiometer. The bias applied to transistor T1 is greater than that applied to T2, but the biases could alternatively be equal or be applied to one transistor only. In addition, the counteracting bias could alternatively be connected in series with the starting bias.