| 摘要 |
PURPOSE:To stabilize the output voltage of a self-excited converter by maintaining the ON period of a switching transistor constant and controlling the OFF period irrespective of a flyback voltage generating period. CONSTITUTION:A self-excited converter is composed of a main transformer 4 having a primary exciting winding 1 and the like, a self-excited oscillator having a switching transistor 5, a rectifying and smoothing circuit 7 having a diode and the like, and an overvoltage detector having a detecting resistor VR and the like. In this case, a base winding 10 is grounded through a capacitor C, and connected through a control transistor 9 to an input rectifying and smoothing circuit. Further, a resistor R and a diode are connected to the base of the transistor 5. Thus, the rise of a voltage across the capacitor C during an OFF period controls the transistor 9 to control the OFF period (since the ON period is constant), thereby substantially controlling an ON duty ratio.
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