GB1172543A - Improvements in or relating to Switched Voltage Regulators - Google Patents

Abstract

1,172,543. Automatic voltage control. MARCONI CO. Ltd. Jan.25, 1967 [Jan. 27, 1966], No.3841/67. Heading G3R. In a voltage regulator of the type including a switching transistor which is connected to load terminals by way of a filter constituted by a series inductor and a shunt capacitor, means are provided to limit the transient current flow, due to the charging of the said capacitor, which occurs when the regulator is initially switched on. As shown, a load 8 is supplied from a source 1 by way of a switching transistor 3 and an inductance/ capacitance filter 5, 6, the transistor 3 being controlled in known manner by circuitry 9, 10, 11 so that the voltage across the load is maintained constant; associated with the transistor 3 are a further transistor 19, resistors 4, 14, 15, 16 and 17, and a capacitor 18 inter-connected as illustrated. In operation, when the regulator is first switchedon capacitor 6 acts momentarily as a short-circuit, but as transistor 19 is initially in a high-resistance state the transistor 3 is rendered practically non- conducting, so that current does not flow to the capacitor; however the potential divider 14, 15 allows a voltage to be applied from the integrating circuit 17, 18 to the base of transistor 19 sufficient to bring the latter gradually into conduction, allowing base current to flow to transistor 3 and in turn allowing current to flow into capacitor 6 at a controlled rate. This effect is cumulative and continues until capacitor 6 is fully charged; the transistor 19 then is fully conductive and transistor 3 operates in normal manner. Thus, the power required to be dissipated in the transistor 3 during the initial transient period is materially reduced. Additionally provided in the circuit shown is a further integrating circuit 12, 13 the effect of which is to make the reference voltage, present in the control circuitry 9, 10, 11, rise at a controlled rate from zero at initial switch-on to the final predetermined value, so that switching of transistor 3 will also occur during the initial transient period, thereby reducing still further the power required to be dissipated in the transistor.