Method and apparatus for producing power for an induction heating source

An induction heating power supply comprising:

• a power circuit having at least one switch and a power output, wherein the power across the switch crosses zero, at a switch zero crossing;
• an output circuit including an induction head, wherein the output circuit is coupled to the power output;
• and
• a controller, having at least one feedback input connected to the output circuit, a control output connected to the switch, wherein the controller begins to cause the switch to be switched on prior to the switch zero crossing, a zero crossing detector coupled to the output circuit, a frequency detector coupled to the zero crossing detector, wherein the frequency detector includes a ramp and a reset coupled to a zero crossing detector, an output voltage detector coupled to the output circuit, a peak voltage detector coupled to the output circuit, and a comparator receiving as an input the output of the peak voltage detector, the frequency detector and the output voltage detector.

An induction heating power supply comprising:

• a power circuit means for providing power, including a plurality of switches and a power output, wherein the power across each switch crosses zero;
• an output means for providing output power, the output means including an induction head and coupled to the power output;
• and
• a controller means for switching the plurality of switches, wherein the switching process begins before the switch zero crossing, and having at least one feedback input connected to the output means, wherein the controller means includes a zero crossing detector means for detecting zero crossing, coupled to the output circuit, and a frequency detector, including a ramp and a reset means for resetting the ramp, coupled to a zero crossing detector, for providing a signal indicative of frequency, coupled to the zero crossing detector.

An induction heating power supply comprising:

• a power circuit means for providing power, including a plurality of switches and a power output, wherein the power across each switch crosses zero;
• an output means for providing output power, the output means including an induction head and coupled to the power output;
• and
• a controller means for switching the plurality of switches, wherein the switching process begins before the switch zero crossing, and having at least one feedback input connected to the output means, a zero crossing detector means for detecting zero crossing and coupled to the output circuit, a frequency detector means for providing a signal indicative of frequency and coupled to the zero crossing detector, wherein the frequency detector means includes a ramp and a reset for resetting the ramp and coupled to a zero crossing detector, an output voltage detector for detecting peak voltage and coupled to the output means, a peak voltage detector means for detecting output voltage and coupled to the output circuit means, and a comparator means for predicting the zero crossing, wherein the comparator means receives as inputs the output of the peak voltage detector, the frequency detector means, and the output voltage detector means.

A method of induction heating comprising:

• providing power, by switching a power supply, wherein the power across a switch crosses zero at a switch zero crossing;
• sensing at least one output parameter;
• predicting the switch zero crossing in response to the at least one output parameter;
• and
• beginning the switching process before the switch zero crossing, by detecting zero crossings using a voltage ramp resetting the ramp at zero crossing, and providing a signal indicative of frequency.