| 摘要 |
PROBLEM TO BE SOLVED: To prevent an overshoot that may be caused by the oscillation of an output voltage, repeated large change of frequency or voltage fluctuation even if large change of frequency or the voltage fluctuation occurs to the input voltage of a battery power source. SOLUTION: When a VDD power source voltage deviates out of the range between the operating upper and lower limit voltages of a PWM circuit 11, a detecting circuit 20 stops the duty control of the PWM circuit. Then, by letting the detecting circuit start the duty control of the PWM circuit in a given delay time t20 when the VDD power source voltage returns to the range of the operating upper and lower limit voltages of the PWM circuit, the oscillation of a VCC output voltage can be prevented without causing an error amplifier 16 of the PWM circuit 11 to be operated by phase shift even if the large change of frequency, voltage fluctuation, or these combined changes occur to the battery voltage and the DC input power source one.
|
