Method for sensing container using resonant current

A method for sensing a container by an induction heating device that includes a switch driving unit, an induction heating circuit configured to drive a working coil by an inverter unit, a sensor configured to sense current applied to the induction heating circuit, a resonant current conversion unit configured to convert current values to voltage values, a shutdown comparison unit, a shutdown circuit unit configured to control the switch driving unit, a count comparison unit, and a control unit configured to determine presence of the container on the working coil, the method comprising:

• charging, by controlling the inverter unit through the switch driving unit, the induction heating circuit;
• sensing, by the sensor, a current applied to the induction heating circuit;
• converting, by the resonant current conversion unit, a current value of the current into a first voltage value;
• comparing, by the shutdown comparison unit, the first voltage value with a predetermined resonance reference value;
• based on the first voltage value being greater than the predetermined resonance reference value, generating a resonance of the current by controlling the switch diving unit through the shutdown circuit unit;
• based on generation of the resonance, sensing, by the sensor, a resonant current applied to the induction heating circuit;
• converting, by the resonant current conversion unit, a current value of the resonant current measured by the sensor into a second voltage value;
• comparing, by the count comparison unit, the second voltage value with a predetermined count reference value;
• generating, by the count comparison unit, one or more output pulses based on a result of the comparison of the second voltage value with the predetermined count reference value;
• comparing, by the control unit, a count of the one or more output pulses with a predetermined reference count, or comparing, by the control unit, an on-duty time of the one or more output pulses with a predetermined reference time;
• and
• based on (i) a result of the comparison of the count of the one or more output pulses with the predetermined reference count or (ii) a result of the comparison of the on-duty time of the one or more output pulses with the predetermined reference time, determining, by the control unit, whether or not an object is present on the working coil,
• wherein charging the inducting heating circuit comprises:
• receiving, at the control unit, a voltage applied to the inverter unit,
• outputting, from the control unit, a first single pulse having a first on-state duration based on a variation amount of the voltage being less than a predetermined variation reference value, and
• outputting, from the control unit, a second single pulse having a second on-state duration greater than the first on-state duration based on the variation amount of the voltage being greater than the predetermined variation reference value.