| 摘要 |
PURPOSE:To enable satisfactory rice boiling irrespective of the fluctuation of voltage by detecting the line voltage of the external power supply so as to adjust the frequency of AC voltage applied to an induction heating coil and to maintain the heating output constant. CONSTITUTION:When a drive circuit 8 outputs a switching signal, a switching transistor 5 is switched to supply AC current to an induction heating coil 3 for heating a rice boiling pot. When voltage of a power supply 1 is divided through resistances R1, R2 and inputted to a microcomputer MC, the corresponding signal is outputted from the microcomputer MC through a drive signal generating circuit 7 to a drive circuit 6. When heating of 1000W output is carried out with 100V line voltage and 28kHz switching frequency (f) and the line voltage may be reduced to 90V, the microcomputer MC reduces the switching frequency of the transistor 5 to 18kHz. When the line voltage of the power supply is raised to 110V, said computer MC increases the switching frequency (f) to 38kHz for maintaining the heating output at 1000W. |
