| 摘要 |
PURPOSE: To avoid overvoltage by controlling ON-OFF of a pair of switching circuits and by increasing the switching frequency of a pair of switching circuits in response to a rise in a first voltage at both ends. CONSTITUTION: When the output of oscillating means 13 is inverted, the switching circuit 5 is turned off and the switching circuit 6 begins to turn off. In this time period, a resonance circuit is formed from an inductor 7-capacitor 11-diode of switching circuit 6-inductor 7, and a resonance current flows to this circuit. Also, a voltage stepped-up by the resonance is generated. When a voltage across capacitors 8 and 11 rises, an output frequency of oscillating means 13 increases by the control means 15. Therefore, energy stored in the inductor 7 decreases. Because of this, step-up action is degraded or lost and an excessive voltage across the capacitor 8 can be prevented. By doing this, application of a high voltage to the switching circuit 5 and 6 can be prevented. |
