| 摘要 |
PROBLEM TO BE SOLVED: To provide a switching power supply circuit, capable of realizing fast response at load fluctuation, without degrading efficiency at normal operation.SOLUTION: An output circuit 1 includes MOSFET2 and 3 connected between a power supply terminal VD and a ground terminal for charging a capacitor 5 through an inductor 4. An output voltage Vout is detected as a monitor voltage Vfb, and generates an error signal Verr by an error amplifier 7. A comparator 11 of a driver circuit 10, to which the error signal Verr and a triangular wave signal from an oscillator circuit 12 are given, generates a PWM signal and drives the MOSFET2 and 3. The oscillator circuit 12 outputs a triangular wave signal at a first frequency f1 in normal operation, and the frequency is switched to a second frequency f2, higher than the first frequency, by being given a detection signal S from a detection circuit 15 if load fluctuation exceeds a predetermined range. Thus, voltage fluctuation is suppressed with the higher frequency, and back to normal operation if the fluctuation subsides.SELECTED DRAWING: Figure 1 |
