| 摘要 |
PURPOSE:To reduce the copper loss of a primary winding of a power supply transformer, by avoiding an excessive charging current and a rush current through the elimination of timing concentration of a charge current to a smoothing capacitor. CONSTITUTION:A voltage induced in a secondary winding 3b is rectified at a rectifying circuit 4, smoothed at a smoothing capacitor C2 and supplied to a load 5. In a constant current circuit 2, a diode bridge consisting of diodes D1-D4 operates the constant current circuit 2 at both polarities of an AC power supply voltage. A capacitor C1 produces a voltage Vr driving the circuit 2. A voltage Vr of a photo transistor TR10 is controlled by controlling charge/discharge of a capacitor C1 to control a primary current i1 to a value matched to the load 5. An output voltage VD is made constant to a specified value with a negative feedback operation. The output voltage VD can be kept to the specified value with the similar operation even with the fluctuated load 5. |
