| 摘要 |
PURPOSE:To stabilize the output voltage irrespective of the voltage variation of a power source. CONSTITUTION:An unstable oscillation circuit 5 to output the ON and OFF signal of a switching element SW, a Zener diode ZD1 to detect the oscillation voltage time applied to both ends of the switching element SW, and the like are provided. The oscillation voltage is applied to both ends of the switching element SW, the applied voltage is detected by the Zener doide ZD1, and a transistor Q is turned on by the signal phase at the part where the voltage is made at the Zener voltage or higher. As a result, even though there is an H level of output signal of the unstable oscillation circuit 5, the switching element SW is turned off by the turning ON of the transistor Q. Consequently, the signal width of the on duty signal of the switching element SW is made shorter when the input power source voltage is large, and made longer when the input power source voltage is small, contrarily, so as to control the output voltage constant. |
