Method and apparatus for high-side input winding regulation

A power supply, comprising:

• an energy transfer element having an energy transfer element input and an energy transfer element output;
• a power switch coupled between a positive input supply rail of the power supply and the energy transfer element input;
• a sampling circuit coupled to sample a signal across the energy transfer element input during an off time of the power switch to provide a sampled output of the power supply, wherein the sampled output of the power supply is disabled from being resampled by the sampling circuit during an on time of the power switch;
• and
• a control circuit coupled to the sampling circuit and the power switch, the control circuit coupled to switch the power switch in response to the sampled output of the power supply.

A method of controlling a power supply, comprising:

• switching a power switch coupled between a positive input supply rail and an energy transfer element input of an energy transfer element;
• transferring energy from the energy transfer element input to an energy transfer element output in response to the switching of the switch;
• reflecting a signal from across the energy transfer element output to across the energy transfer element input during an off time of the power switch;
• sampling the signal from across the energy transfer element input during the off time of the power switch to provide a sampled output of the power supply;
• disabling the sampled output of the power supply from being resampled during an on time of the power switch;
• and
• controlling the switching of the power switch in response to the sampled output of the power supply.