| 摘要 |
PROBLEM TO BE SOLVED: To avoid the reduction in the efficiency of a resonance-type power supply circuit and eliminate unnecessary pulses. SOLUTION: A drive power supply 3 is connected to one end of a primary coil 2 of a flyback transformer 1, and a MOSFET 4 which is a main switching device is connected to the other end. A damper diode 5 and a series circuit, consisting of a resonance capacitor 6 and a MOSFET 7 which is an auxiliary switching device are connected in parallel to the MOSFET 4. After the MOSFET 4 is turned off, a current flows back and forth between the primary coil 2 and the resonance capacitor 6. As a current which tends to flow from the primary coil 2 to the resonance capacitor 6, after the damper diode 5 has been turned on/off, is blocked by the MOSFET 7, unnecessary pulses are not generated. Further, as the zero volt of the resonance coil is applied to the MOSFET 4 when it is turned off, a switching loss can be eliminated, so that the efficiency of a circuit can be improved. |
