Flyback converter controller with single pin detection of over-voltage and auxiliary winding faults

A flyback converter, comprising:

• an input voltage rail for providing an input voltage to a primary winding of a transformer;
• a controller having an auxiliary winding and over-voltage fault terminal;
• a first voltage divider configured to couple a divided version of the input voltage to the auxiliary winding and over-voltage fault terminal and configured to couple a divided version of an auxiliary winding voltage to the auxiliary winding and over-voltage fault terminal;
• and
• a second voltage divider configured to divide the voltage for the auxiliary winding into a divided voltage, wherein the controller includes a feedback terminal for receiving the divided voltage, and wherein the controller is configured to compare a voltage for the auxiliary winding and over-voltage fault terminal to at least one over-voltage threshold to detect an over-voltage fault for the input voltage and is configured to control a cycling of a power switch transistor during a normal mode of operation responsive to the divided voltage, and is further configured to test for an open circuit fault for the auxiliary winding prior to the normal mode of operation responsive to a comparison of the divided voltage to an open circuit threshold voltage.