Patent ID: 8502417

Claim:
A power source device having a main power source circuit whose output voltage is changeable and one or more sub power source circuits whose output voltage is changed in the same changing direction as a changing direction of the output voltage of the main power source circuit when the output voltage of the main power source circuit is changed, comprising: a voltage difference detecting circuit which detects whether a voltage difference between the output voltage of the main power source circuit and the output voltage of the sub power source circuit is within a predetermined voltage difference; and a voltage control circuit which controls the output voltage of the main power source circuit and the output voltage of the sub power source circuit based on a voltage changing signal and an output from the voltage difference detecting circuit; wherein the voltage control circuit changes the output voltage of the main power source circuit and the output voltage of the sub power source circuit based on the voltage changing signal; and when the voltage difference detecting circuit detects that the voltage difference between the output voltage of the main power source circuit and the output voltage of the sub power source circuit is more than the predetermined voltage difference, the voltage control circuit controls output voltage changing speeds of the output voltage of the main power source circuit and the output voltage of the sub power source circuit so that the voltage difference between the output voltage of the main power source circuit and the output voltage of the sub power source circuit is within the predetermined voltage difference.