| 摘要 |
PROBLEM TO BE SOLVED: To alleviate an electric stress exerted on a switching transistor at the time of operation of a thermal protector. SOLUTION: A starting circuit (5, 6 and 7) includes voltage dividing resistors 6, 7 and a starting trigger capacitor 5 for connecting the voltage dividing points of the voltage dividing resistors 6, 7 to a base terminal of a switching transistor 4 so as to form a trigger current. A trigger current allows the transistor 4 to be initially conducted. Part of the resultant inverter output is fed back to the base terminal of the transistor 4. A charge resetting diode 14 having a connection polarity for suppressing an increase in potential of the potential dividing point is interposed between a collector terminal of the transistor 4 and the potential dividing point. A thermal protector 17 for detecting heat generation of the transistor 4 so as to protect the transistor 4 is connected between a connecting point between one end of each of LC resonant circuits 2, 3 constituting an inverter and a cathode terminal of another charge resetting diode 13 and the collector terminal of the transistor 4. |
