Patent ID: 7816806

Claim:
A power supply device, comprising: a direct-current (DC) voltage source; an auxiliary voltage source that has one end coupled to a positive terminal of the DC voltage source; a load that consumes power; an inductance element that has one end coupled to the load; a first switching element that is coupled to an other end of the inductance element and to an other end of the auxiliary voltage source, and applies a total voltage of the DC voltage source and the auxiliary voltage source to the inductance element by repeating intermittent switching on/off; a second switching element that is coupled to the other end of the inductance element, and applies a voltage of the DC voltage source to the inductance element by repeating intermittent switching on/off alternately with the first switching element so that one of the first switching element and the second switching element is switched on; a control circuit that controls power to be supplied to the load by changing the switching on/off ratio between the first switching element and the second switching element; and a selector switch that switches coupling of the second switching element to the DC voltage source so that the second switching element is coupled to either of the positive terminal or a negative terminal of the DC voltage source, wherein, when the DC voltage source is in a normal voltage state, the DC voltage source supplies power directly to the load and the control circuit switches the selector switch to the negative terminal at the same time, and thereby the power of the DC voltage source is charged to the auxiliary voltage source through the inductance element by switching on/off the first switching element and the second switching element, when the DC voltage source is in a voltage drop state, the control circuit switches the selector switch to the positive terminal, and thereby power is supplied to the load through the inductance element by switching on/off the first switching element and the second switching element.