| 摘要 |
PURPOSE:To obtain specified performance without damaging a switching element by causing the switching element to operate always at normal timing even if an input alternating current has noise. CONSTITUTION:When an FET 3 is off, a current generated in a choke coil L flows into an electrolytic capacitor C through a flywheel diode D, and charges this capacitor C. On this occasion, a current flowing into the load 4 side becomes smaller, and a voltage drop by a resistor R4 becomes smaller. A control circuit 5 detects the magnitude of the current supplied to the load 4 side from the flywheel diode D by the voltage drop of the resistor R4. And the control circuit 5 turns the FET 3 on through the medium of R1 when the above- mentioned current becomes less than a specified level, and turns the FET 3 off when the above-mentioned current becomes more than a specified level. Consequently, the control circuit 5 performs the switching control of the FET 3 always at normal timing, even if an alternating current supplied from a commercial power source 1 has noise, etc. |
