Circuits and Methods for Auxiliary Secondary Supply Generation with Self-Starting Primary Side Driver in Isolated Power Converters

A primary side driver circuit in a switched-mode power converter using an isolated topology, the primary side driver circuit configured to generate switch control signals provided to control terminals of one or more primary side switch devices in order to energize a primary side winding of a transformer, the primary side driver circuit comprising:

• input terminals configured for inputting external control signals from a secondary side of the switched-mode power converter;
• a startup circuit configured to generate startup control signals that control switching of the one or more primary side switch devices during a startup operating phase;
• and
• a selection circuit configured to provide the switch control signals based upon the generated startup control signals during the startup operating phase, and based upon the external control signals during a steady-state operating phase.

A method, in a primary side driver circuit of a switched-mode power converter using an isolated topology, for generating switch control signals that are provided to control terminals of one or more primary side switch devices in order to energize a primary winding of a transformer of the switched-mode power converter, the method comprising:

• monitoring external control signals from a secondary side of the switched-mode power converter;
• generating startup control signals that control switching of the one or more primary side switch devices, the startup control signals being based upon default parameters;
• detecting whether the switched-mode power converter is operating in a startup operating phase;
• and
• responsive to detecting that the switched-mode power converter is operating in the startup operating phase, providing the switch control signals to the one or more primary side switch devices based upon the generated startup control signals.