Voltage discharge circuit

A power supply that can switch between two or more output voltage levels, comprising:

• a transformer having primary and secondary windings;
• an output voltage capacitor coupled in parallel with the secondary windings and coupled to an output node for supplying an output voltage of the power supply;
• a switch coupled between the secondary windings and the output voltage capacitor;
• and
• control circuitry coupled to the switch having an input signal node for receiving an input signal indicating that the output voltage of the power supply is switching voltage levels and for controlling the switch so that the output voltage capacitor discharges through the secondary windings of the transformer.

A method of discharging an output capacitor in a power supply, comprising:

• powering an output voltage at a first voltage level using a power supply having primary and secondary windings, wherein current flows through the secondary windings in a first direction;
• receiving a control signal to change the output voltage from the first voltage level to a second, lower voltage level;
• detecting a change in voltage level of the secondary windings sufficient to initiate a current flow in a second direction, opposite the first direction, through the secondary windings;
• and
• activating a switch using a discharge signal to allow the current to continue to flow in the second direction through the secondary windings to discharge the output voltage through the secondary windings.