| 摘要 |
PURPOSE: To prevent the heat generations and damages of the switching elements of an inverter, by eliminating their abnormal operations caused by their lead-phase operations through bringing them into lag-operations, when the resonance frequency of a resonance circuit for feeding a high-frequency output to a discharge lamp is higher than the switching operation frequency of the inverter. CONSTITUTION: An AC voltage from an AC power supply 11 is rectified in a full-wave way by a DC circuit 12, and a smoothed DC voltage is applied to FETs Q1, Q2 of an inverter 14. The FETs Q1, Q2 perform switching operations by their control signals. The high-frequency output generated from the resonance circuit comprising an output coil L12 and capacitor C14 by these switching operations is fed to a discharge lamp 17 to light it. In this operation, when the resonance frequency of the resonance circuit comprising the output coil L12 and capacitor C14 is higher than the switching operation frequency of the inverter 14, the FETs Q1, Q2 are so brought into lag-operations by a lag-phase coil L11 that the overcurrents in case of lead-phase operations are made not to flow through the FETs Q1, Q2. |
