Patent ID: 7990122
Filing Date: 2011-08-02
Classification: H02M

Abstract:
1. A digital control switching power-supply device having a plural number of power supply units, wherein each power supply unit comprises: a digital signal processing section having digital voltage control means that performs control so that the difference signal between a digital output voltage signal obtained by digitizing a fed-back output voltage of the switching power-supply device and a digital reference voltage signal obtained by digitizing a reference voltage of a command signal is zero and a digital pulse width modulation (DPWM) generator that generates a pulse width modulation (PWM) pulse signal; a pair of power semiconductor switching components driven by the PWM pulse signal; an LC smoothing filter that converts a square wave voltage resulting from switching of said pair of power semiconductor switching components into a direct current; transient variation detection means that detects a transient variation at the time of a sudden load change; and selection means that selects any of a PWM pulse signal having a desired duty generated by said DPWM generator and a PWM pulse signal having a preset fixed duty according to the result of detection by said transient variation detection means, said pair of power semiconductor switching components is driven by the PWM pulse signal selected by said selection means, and a common output capacitor is shared by said LC smoothing filters of said plural number of power supply units, wherein said transient variation detection means has a CR filter for transient variation detection provided across an inductor L of said LC smoothing filter and a transient variation detection circuit composed of a window comparator provided at an output terminal of the CR filter, said transient variation detection circuit compares an output voltage of said CR filter with upper and lower limit values preset around a reference voltage set to provide a desired output voltage of the switching power-supply device in order to obtain detection information at the time of a sudden load change and supplies the comparison result to said selection means, said selection means receives said comparison result as a selection signal and selects from among said PWM pulse signals based on said comparison result, and the digital control switching power-supply device further comprises: a maximum value memory circuit that determines the difference signal between a digital signal obtained by A/D-converting the output voltage of said CR filter and a digital output voltage signal obtained by A/D-converting the output voltage of the digital control switching power-supply unit and selects and memorizes the maximum value of plural number of difference signals generated by the power supply units; and means for generating a compensation digital reference voltage signal by adding, to said digital reference voltage value, the difference value between the maximum difference signal value memorized in said maximum value memory circuit and the difference signal between the digital signal obtained by A/D-converting the output voltage of said CR filter of each power supply unit and the digital output voltage signal obtained by A/D-converting the output voltage of the digital control switching power-supply device.