| 摘要 |
PURPOSE:To obtain a power supply circuit comprising one transistor instead of a plurality of transistors previously arranged separately by connecting an overcurrent detecting resistor to the base of an ON-OFF control transistor of a switching element through a resistor. CONSTITUTION:When a switching element 20 is turned off, a flyback voltage occurs at the primary winding 5 and secondary winding 23, energy stored in a transistor 4 is discharged as the secondary current through the secondary winding 23, and it is supplied as a power supply voltage 26. At this time, a flyback voltage occurs also in a bias winding 6 at the high side, a switching element 7 is turned on, and the primary current flows and is stored in a capacitor 3. When energy stored in a transformer 4 is all discharged, a current flows in the opposite direction from the capacitor 3 and energy is stored in the transformer 4; in this time period, a transistor 18 is turned on and a charge current flows to a capacitor 14, the base voltage of a transistor 15 drops to a particular value, and then the switching element is turned off. |
