Controller for resonant converter

An apparatus comprising:

• a resonant converter comprising:
• a first switch;
• a resonant tank coupled to the first switch at a switching node;
• and
• a first capacitor;
• and
• a controller configured to:
• operate in a first mode by:
• providing a plurality of first periodic control pulses to drive the switching of the first switch at a first switching frequency;
• operate in a second mode by:
• providing the plurality of first periodic control pulses to drive the switching of the first switch at a second switching frequency, the second switching frequency being less than the first switching frequency, or stopping providing the first periodic control pulses;
• and
• providing one or more first charging pulses, each of the one or more first charging pulses driving the switching of the first switch to charge the first capacitor.

A method of controlling a resonant converter, the resonant converter comprising:

• a first switch;
• a resonant tank coupled to the first switch at a switching node;
• and
• a first capacitor;
• wherein the method comprises:
• operating a controller in a first mode in which the controller:
• provides a plurality of first periodic control pulses to drive the switching of the first switch at a first switching frequency;
• operating in the controller in a second mode in which the controller:
• provides the plurality of first periodic control pulses to drive the switching of the first switch at a second switching frequency, the second switching frequency being less than the first switching frequency, or stops providing the first periodic control pulses;
• and
• provides one or more first charging pulses, each of the one or more first charging pulses driving the switching of the first switch to charge the first capacitor.