Push-pull converter with reduced EMI and voltage spikes

A power supply circuit comprising:

• a push-pull portion comprising a transformer having a primary winding and a plurality of secondary windings that share the primary winding, wherein a first terminal of the primary winding is connected to ground via a first switch, and wherein a second terminal of the primary winding is connected to ground via a second switch;
• an inductor having a first terminal thereof connected to an input voltage via a third switch, wherein a second terminal of the inductor is connected to a centre tap on the primary winding of the transformer;
• an energy storage portion connected between the primary winding of the transformer and ground, said energy storage portion being further connected to the first terminal of the inductor via a fourth switch such that the fourth switch can control the flow of current from the energy storage portion to the first terminal of the inductor, wherein the first, second, third and fourth switches have respective control terminals;
• and
• a plurality of output portions, each comprising first and second output terminals and arranged to provide a respective output voltage across said first and second output terminals, wherein a first terminal of each secondary winding is connected to the first output terminal of a corresponding output portion via a respective first forward bias output diode, a respective second terminal of each secondary winding is connected to the respective first output terminal via a respective second forward bias output diode, and wherein the respective second output terminal is connected to a centre tap of the respective secondary winding,
• a forward bias diode connected between the third switch and the first terminal of the inductor and arranged to prevent a back flow of current from the fourth switch to the input voltage.