| 摘要 |
PURPOSE:To disuse the electric consumption for switching operation by using a transistor for a switching element of an inverter. CONSTITUTION:A load current detecting unit 6 is provided between a commercial electric source 7 and a full-wave rectifying circuit 8, and its output signal is added to a comparing circuit 9 for comparing with the output siganl of a reference signal generating circuit 10. It is then added to a timing control circuit 11 for controlling the length of on-time of a transistor 1. Besides, in a collector zero voltage detecting circuit connected with a collector of the transistor 1, a time point when the transistor 1 is changed over to be on is detected, and the output signal is fed to the timing control circuit 11 as a reset signal. Here, an automatic oscillation loop is constructed by the transistor 1, a heating coil 2, a condenser 4, the timing control circuit 11, the collector zero voltage detecting circuit 12, and a base voltage control circuit 13, for controlling the oscillation frequency automatically according to the impedance variation in a heating coil. |
