| 主权项 |
1. A semiconductor device for a switching power supply device configured to convert a predetermined input voltage to an output voltage by controlling a switching element to be turned on and off, and supply a load with an output power corresponding to the output voltage, the semiconductor device comprises:
a control circuit configured to control an operation of the switching element by using an intermittent oscillation control signal representing a start timing and an end timing of an oscillation interval, so that the oscillation interval when the switching element is turned on and off and a stop interval when turning on and off of the switching element is stopped are alternately repeated with a predetermined intermittent oscillation frequency, wherein the control circuit varies the intermittent oscillation frequency by using a changing signal generated by using a period signal having a predetermined period signal frequency, wherein, when the changing signal is the period signal and the period signal is generated so that a frequency, a local maximum value of an amplitude, and a local minimum value of the amplitude for each of cycle intervals of the period signal are constant respectively, the period signal frequency is set to a frequency lower than the intermittent oscillation frequency, or the period signal frequency is set to a frequency higher than the intermittent oscillation frequency and other than integer multiples of the intermittent oscillation frequency, and a phase difference of the changing signal with respect to the intermittent oscillation control signal is set so that a distribution of the intermittent oscillation frequency is dispersed, and wherein, when the changing signal is the period signal and the period signal is generated so that (a) the local maximum value of the amplitude and the local minimum value of the amplitude for each of the cycle intervals of the period signal are constant respectively, and (b) a plurality of signals having respective different frequencies that are one-half or the integer multiples of the intermittent oscillation frequency for each of the cycle intervals of the period signal are sequentially generated, the phase difference between the plurality of signals for each of the cycle intervals is set so that the distribution of the intermittent oscillation frequency is dispersed. |
