| 摘要 |
PURPOSE:To prevent a power transistor from breaking at a trigger signal applying time by clamping the control voltage of a voltage controlled oscillator by a voltage corresponding to the control voltage at the lower or supply limit of the output voltage controlling range. CONSTITUTION:When an output voltage or current increases, the control voltage from an error amplifier 13 decreases, and the oscillating frequency from the voltage controlled oscillator 1 rises. Thus, the ON and OFF frequency of a power transistor 5 increases, and the output voltage or current is maintained constant. When a trigger signal is applied in the state that an input power is applied, the minimum value of the control voltage is clamped substantially at the initial voltage determined by a Zener diode 20. In this manner, the oscillating frequency of the oscillator 1 is prevented from abnormally rising after the trigger signal is applied. |
