JPS6460991A - Induction heating cooker - Google Patents

Abstract

PURPOSE:To prevent a destruction in case of using a SUS 304 pot whose loss of switching element is larger, and to prevent an extraordinary drop of the heating power in case of using an iron pot, by dropping the charging current of a timer capacitor of an OFF time detecting circuit when a drop of the DC power supply voltage is detected. CONSTITUTION:When the voltage of a DC power supply 1 is low, a diode 38 is turned off, and the voltage applied to a charge circuit 23 of a capacitor 37 is almost proportional to the voltage of the DC power supply 1. As a result, when a SUS 304 pot whose OFF time is short is used, the charging voltage of a capacitor 21 is lowered, the reduction of Vr by a diode 27 is made larger, and the VCEmax and ICmax are reduced to suppress the loss of a switching element 3. And when an iron pot is placed, since the OFF time of the switching element 3 is larger, the charging voltage of the timer capacitor 21 is higher, and the diode 27 keeps the OFF condition. As a result, although the VCEmax is equal to the ordinary condition and the voltage of the DC power supply in the ICmax is increased compared with the time of the rating, the loss of the switching element 3 is small and there is no fear of destruction.