Power supply circuit having two mutually independent outputs

Claim 1

A power supply circuit for converting an input d.c. voltage into a first output d.c. voltage which is applied to a first load and into a second output d.c. voltage which is applied to a second load, said power supply circuit comprising the series arrangement of an inductor and a controllable switch, which series arrangement is connected to a terminal for the input voltage, said switch being, in operation, alternatively in the conductive and in the non-conductive states, the first output voltage being derived from a square-wave voltage present across the inductor, the conduction periods of the switch being controlled by means of a control circuit connected to a control electrode of the switch for obtaining for the first output voltage, a value which is substantially independent of variations of the input voltage and of the first load, the power supply circuit further comprising a tuned rectifier coupled to the inductor for producing the second output voltage across a smoothing capacitor, said rectifier being such that a half cycle of sinusoidal circuit flowing therethrough during a period commencing when the switch commences to be conductive, does not exceed the conduction time of the switch, characterized in that the tuned rectifier comprises a series resonant network and a peak-peak rectifier connected thereto, a half cycle of the sinusoidal current flowing through the series resonant network not exceeding the time interval between two consecutive edges of the square-wave voltage present across the inductor whereby variations in the value of one of said loads has substantially no effect on the voltage across the other of said loads.