Method and system to control a QR-inverter in a induction cooking appliance

An electronic control system for controlling an induction heating coil of an induction cooking appliance, the electronic control system comprising:

• a quasi-resonant inverter provided with:
• a switching device electrically connected to said induction heating coil by a node having a first voltage which is an oscillating voltage and is indicative of the voltage across said switching device, and a driver unit configured to provide to said switching device an enabling signal comprising a plurality of pulses, in order to switch-on and switch-off said switching device for a switch-on period and a switch-off period,
• wherein said electronic control system comprises control means configured to control said driver unit in order to regulate said enabling signal, and
• wherein said control means are further configured to:
• determine a second voltage indicative of the minimum value of said first voltage during said switch-off period,
• regulate said switch-off period based on said second voltage,
• regulate said enabling signal based on said regulated switch-off period, determine a third voltage indicative of the value of said first voltage about at the end of said switch-off period, and
• increase said switch-off period, if said third voltage is greater than said second voltage and said first voltage is decreasing.

An induction cooking appliance comprising:

• at least an induction heating coil,
• a quasi-resonant inverter provided with:
• a switching device which is electrically connected to said induction heating coil by a node having a first voltage which is an oscillating voltage and is indicative of the voltage across said switching device, and a driver unit configured to provide to said switching device an enabling signal comprising a plurality of pulses, in order to switch-on and switch-off said switching device for a switch-on period and a switch-off period, and
• an electronic control system comprising control means configured to control said driver unit in order to regulate enabling signal,
• wherein said control means are further configured to:
• determine a second voltage indicative of the minimum value of said first voltage during said switch-off period,
• regulate said switch-off period based on said second voltage,
• regulate said enabling signal based on said regulated switch-off period,
• determine a third voltage indicative of the value of said first voltage about at the end of said switch-off period, and
• increase said switch-off period, if said third voltage is greater than said second voltage and said first voltage is decreasing.

An induction cooking appliance comprising:

• an induction heating coil;
• a quasi-resonant inverter comprising a solid state switch electrically connected to said induction heating coil at a node having a first voltage indicative of a voltage across said switch, the switch being configured to be in an ON state for a switch-on period and in an OFF state for a switch-off period in accordance with an enabling signal comprising a plurality of pulses;
• at least one detection circuit configured to:
• determine a second voltage indicative of a minimum value of said first voltage during said switch-off period;
• determine a third voltage indicative of a value of said first voltage at an end of said switch-off period;
• and
• determine a fourth voltage indicative of a maximum value of said first voltage during said switch-off period;
• and
• at least one controller configured to:
• regulate said switch-off period by increasing said switch-off period when said third voltage is greater than said second voltage and said first voltage is decreasing, and by decreasing said switch-off period when said third voltage is greater than said second voltage and said first voltage is increasing;
• regulate said switch-on period by increasing said switch-on period when said second voltage is greater than a first voltage threshold;
• regulate said enabling signal based on said regulated switch-off period and said regulated switch-on period;
• provide said regulated enabling signal to the switch;
• and
• stop operation of said quasi-resonant inverter when said fourth voltage is greater than a second voltage threshold.