Patent ID: 7132818
Filing Date: 2006-11-07
Classification: H02M

Abstract:
1. A control device for controlling a switching power supply having an output voltage, the switching power supply including a switching device which switches at a predetermined switching period and a predetermined switching frequency to produce an output, and a smoothing circuit for smoothing the output of the switching device, the smoothing circuit including an inductor connected to the switching device, the control device comprising: a voltage detector for detecting the output voltage of the switching power supply to generate a voltage detection signal corresponding to the output voltage; a current detector for detecting a current flowing through the inductor for each switching period to generate a current detection signal corresponding to the detected current; a rectangular wave generator for generating a rectangular wave signal having a frequency of half the switching frequency; a multiplier for multiplying the current detection signal by a current control gain to generate a gain-multiplied current detection signal; a calculator for adding the rectangular wave signal and subtracting the gain-multiplied current detection signal to/from the voltage detection signal to generate a control signal having a magnitude; a driving signal generator for generating a driving pulse signal having a duty ratio corresponding to the magnitude of the control signal and supplying the driving pulse signal to the switching device to drive the switching device; the driving pulse signal being generated so that ΔD/ΔCS equals α, where ΔD represents an amount of change in the duty ratio for each switching period, and ΔCS an amount of change in the control signal for each switching period, and α is a constant, and a gain adjustor for adjusting the current control gain according to the gain-multiplied current detection signal and the duty ratio, the current control gain being adjusted so that ΔPIS/ΔD=−½α is satisfied, where ΔPIS represents an amount of change in the gain-multiplied current detection signal for each switching period.