| 摘要 |
PURPOSE:To facilitate manufacture of an apparatus and miniaturize it by providing a monostable multivibrator to be started simultaneously with a rise starting point of time of triangular wave voltage and an AND circuit and by forming an OFF-period forcibly. CONSTITUTION:A step-up type switching power device is composed of a switching transistor 3, an energy storage coil 2, rectifying and smoothing circuits 4-5, an error amplifier 10 for driving and controlling said transistor 3, a voltage comparator 11, a triangular wave generator circuit 12 and others to supply DC output voltage. In this case, there are provided a monostable multivibrator 15 to be started simultaneously with a rise starting point of time of triangular wave output voltage of the triangular wave generator circuit 12 and an AND circuit 16 connected with a base of the transistor 3. Thus, an output and logical product from the voltage comparator 11 are taken and applied to the base of said transistor 3 so that an OFF-period setting pulse is outputted only for a period while a triangular wave voltage lowers as compared with a feedback voltage.
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