| 摘要 |
PURPOSE:To make a flyback transformer 11 small in size, to reduce the cost and heat dissipation by improving the circuit efficiency and reducing a boosting ratio of the flyback transformer 11. CONSTITUTION:A reverse current block diode 8 is interposed between a drive power supply 18 and a primary coil 12, and a parallel circuit comprising a transistor(TR) 13, a diode 14 and a resonance capacitor 15 is connected in series with the primary coil 12. A series circuit comprising a capacitor 7 and a circuit block 10 is connected between the cathode of the reverse current block diode 8 and ground. The circuit block 10 is made up of a parallel circuit comprising a MOS FET17, a diode 20 and a capacitor 21. The MOS FET17 is operated by the drive pulse whose ON-pulse width is made narrow by quickening the OFF-time as a high output voltage drop increases. |
