Output conduction detection in a buck converter

A buck converter comprising:

• an input switch;
• an output filter circuit coupled to the input switch, the output filter circuit configured to produce a feedback signal indicative of an output voltage of the buck converter;
• a bias capacitor coupled to the output filter circuit;
• an output conductor circuit coupled to the output filter circuit;
• and
• a controller coupled to the output filter circuit, the controller comprising,
• an output drive circuit coupled to the output filter circuit, the output drive circuit configured to receive the feedback signal;
• an input drive circuit coupled to the output drive circuit, the input drive circuit responsive to the feedback signal to produce an input drive signal;
• a bias drive circuit coupled to the bias capacitor and to the input drive circuit, the bias drive circuit responsive to the input drive signal to produce a bias drive signal;
• a bias supply circuit comprising,
• a bias transistor having a gate coupled to receive the bias drive signal, and
• a bias diode, an anode of the bias diode coupled to a drain of the bias transistor and a cathode of the bias diode coupled to the bias drive circuit,
• wherein the bias transistor enters a conducting state responsive to the bias drive signal being asserted;
• and
• an output conduction detector circuit coupled to the source and to a drain of the bias transistor, and responsive to detection of a voltage drop across the bias transistor to produce an output conduction signal.