| 摘要 |
PROBLEM TO BE SOLVED: To provide a keep-warm cooker with improved reliability which can stably control current supplied to a plurality of induction heating coils and improve controlling stability. SOLUTION: Resonant capacitors are connected in series to two induction heating coils for heating a cooker to form a resonant circuit having different resonant frequencies is formed and connected in parallel. To this resonant circuit, current is supplied from an inverter main circuit ad a driving frequency f.Δf set at around 1/100 of the frequency between the resonant frequencies of the resonant circuit, when the drive frequency f set at the start of heating is changed to (f+Δf), a current level of each resonant circuit is detected, drive frequency f is adjusted so that minimal change of the detected voltageΔE1 be a positive value andΔE2 a negative value, and, at same time, sum of the detected value E1(f)+E2(f) will not exceed the upper limit level Emax, and, therefore, input power ratio is controlled to be at a given condition by making the difference between the both be a given value. |
