Adaptive synchronous switching in a resonant converter

A resonant converter comprising:

• resonant circuitry having inductive and capacitive elements configured to create electrical resonance when an input voltage is applied;
• a synchronous rectifier coupled between at least a portion of the resonant circuitry and an output of the resonant converter, the synchronous rectifier comprising:
• a first diode coupled to the output of the resonant converter, and
• a first electrical switch coupled in parallel to the first diode;
• first control circuitry configured to operate the first electrical switch such that the first electrical switch is turned on when there is substantially no voltage across the first diode and current flow in the first diode is positive in a direction from anode to cathode;
• a single electrical switch coupled between the input voltage and at least the portion of the resonant circuitry, the single electrical switch comprising a second electrical switch;
• second control circuitry configured to operate the second electrical switch such that the second electrical switch is turned on when there is substantially no voltage across the second electrical switch;
• and
• clamping circuitry to control a voltage across the single electrical switch, the clamping circuitry comprising:
• a clamp capacitor;
• an electrical clamp switch coupled in series with the clamp capacitor and the single electrical switch;
• a comparator circuit coupled to the clamp capacitor and configured to determine a voltage spike at the single electrical switch;
• and
• a driver coupled to an output of the comparator circuit and configured to turn on the electrical clamp switch in response to the voltage spike.