Power converter controller with bias drive circuit for bias supply

A controller for use in a power converter having an energy transfer element, the controller comprising:

• a primary drive circuit configured to control operation of a primary switch coupled to a primary winding associated with the energy transfer element, the primary drive circuit causing the primary switch to transition between a conducting state during a first portion of a switching cycle and a nonconducting state during a second portion of the switching cycle;
• a bias switch coupled to a bypass capacitor;
• and
• a bias drive circuit configured to control operation of the bias switch to drive a bias current to a bypass capacitor coupled to the bias switch for providing a bias supply to the controller.

A power converter for providing power to a load, the power converter comprising:

• an energy transfer element comprising a primary winding and a secondary winding, the primary winding being coupled to an input voltage during a first portion of a switching cycle and configured to generate a secondary current through the secondary winding during a second portion of the switching cycle;
• an output capacitor coupled to the secondary winding;
• and
• a controller configured to control transfer of energy between the primary winding and the secondary winding, the controller comprising a bias drive circuit configured to control conduction of a bias current through a bias switch instead of through the output capacitor during at least part of the second portion of the switching cycle for providing a bias supply to the controller for the power converter.