GB1431262A - Power supply apparatus - Google Patents

Abstract

1431262 Automatic voltage control ADVANCE ELECTRONICS Ltd 16 March 1973 [16 Dec 1971] 58448/71 Heading G3R [Also in Divisions H2 and H3] In a D.C.-A.C. converter of the type in which a pair of switching devices, such as transistors 14, 15 alternately switch current into the two halves 12, 13 of the centre-tapped primary of a transformer 11, voltage adjustment is achieved by control of the duration of the period in which both switching devices 14, 15 are simultaneously conductive. As described, the D.C. supply 10 may be derived from the A.C. mains by means of a capacitor Fig. 4 (not shown) in series with a diode bridge, the output of which is in series with an inductor. The output of transformer 11 may be rectified at 19, 20 so as to feed a D.C. load 22. In Fig. 3 (not shown) the secondaries and rectifiers are duplicated to supply two loads. Controlling inverters. In Fig. 5, a multi-vibrator 33, 34 provides a sawtooth cycle alternately to the bases of transistors 35 and 36 at 400-1,000 kHz. The output voltage across the load 22 is monitored by transistor 40 and compared with the reference voltage across a Zener diode 41. When each sweep of sawtooth from 33, 34 reaches a voltage dependent on the error between output and reference voltages, the appropriate one of transistors 35, 36 becomes conductive, initiating a pulse which is amplified by transistors 42 or 43 and coupled by transformer 46 to inverting transistors 49 or 50 and then fed to the main inverting transistor 14, 15.