| 摘要 |
PURPOSE: To always obtain a constant boosted voltage from a booster circuit regardless of the fluctuation of the input voltage of the circuit by controlling the output voltage of the circuit to a constant value by turning on a transistor by means of a voltage regulating element when the voltage generated from a secondary-side coil becomes higher than a prescribed value and turning on the transistor when the voltage does not reach the prescribed value. CONSTITUTION: Both capacitors C1 and C3 are gradually charged by repeatedly turning on and off a transistor Q1. When the second capacitor C3 is charged to the sum of the voltage of a Zener diode ZD1 and the base-emitter voltage of the transistor Q1, the diode ZD1 starts to cut the base current of the transistor Q1 even when the diode ZD1 is not completely turned on when the transistor Q1 is turned on. Thus the diode ZD1 changes the turning-on and tuning-off periods of the transistor Q1 so that the voltage of the capacitor C3 can become the sum of the voltage of the diode ZD1 and the base-emitter voltage of the transistor Q1. The voltage of the diode ZD1 is always fixed at the gate-source voltage of the FET regardless of the fluctuation of the input voltage. |
