GB814464A - Frequency converter - Google Patents

Abstract

814,464. Rectifying, changing frequency. WESTINGHOUSE BRAKE & SIGNAL CO. Ltd., and MARTIN, R. G. March 26, 1957 [Jan. 30, 1956], No. 2881/56. Class 38 (2). An arrangement whereby A.C. may be converted to D.C. or to A.C. of a different frequency comprises two reversible transistors V1, V3 each having one emitter/collector electrode connected to an outer terminal of a supply transformer winding and the other emitter/collector electrode connected to a centre tap through a common load. The base electrode of each transistor is positively biased through a resistor R1 or R4 and is connected with an auxiliary transistor V2, V4 whose baseemitter circuits each include a secondary winding of a transformer T2. When the transformer T2 is supplied from a signal source S negative base current flows in the transistors V2, V4 alternately each half-cycle, and when this occurs their emitter-collector circuits are rendered conductive so that a battery B2 supplies negative current to the base of transistor V1 or V3 which overcomes the positive bias and renders the emitter-collector circuit of these transistors conductive. Hence current flows in the load circuit through the transistors V1, V3 alternately. With the signal S having the same frequency and phase as the supply the arrangement operates as a full-wave rectifier producing D.C. of one polarity. By reversing the phase of the signal the opposite polarity is obtained. Thus by periodically reversing the signal phase at a frequency f A.C. of frequency f is obtained. Arrangements are described whereby (a) the reversal of phase of the signal is effected (Fig. 4, not shown), (b) the D.C. bias battery B1 is replaced by a transformer (Fig. 5, not shown), (c) the battery B2 is replaced by a full-wave rectifier circuit including a current transformer (Fig. 6, not shown).