| 摘要 |
PURPOSE:To improve efficiency of power source, by monitoring current flowing through switching elements in an inverter and turning a switching element OFF when the current level is zero. CONSTITUTION:An inverter 1 having switching elements S1-S4 juxtaposed with surge absorbing elements Z are turned ON/OFF by driving signals fed from an inverter drive circuit 4, and the output thereof is fed through a resonance inductance L and primary of a booster transformer T to a booster circuit (Shenkel circuit) 6 utilizing a charger pump and arranged at the secondary of the transformer T so as to charge a smoothing capacitor CL. Voltage across the capacitor is led through voltage dividing resistors R1, R2 to a control circuit 5, while furthermore a current detection circuit 2 and a zero-cross detection circuit 3 are provided in order to determine ON/OFF timing of the switching elements S1-S4. When current flowing through the switching elements S1-S2 (S3-S4) is zero, the switching elements S1-S2 are turned OFF while other switching elements S3-S4 (S1-S2) are turned ON, so as to enable automatic following to resonant frequency.
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