Patent ID: 8407490

Claim:
A power supply device comprising: a main power switch switching between an on position and an off position when a user turns on and off the main power switch, and the main power switch being connected to an external power supply; an auxiliary power switch switching between the on position and the off position by the user turning on and off the auxiliary power switch; a power supplying switch connected in series between the main power switch and a power supply destination, the power supplying switch switching between supplying an electric power and stopping an electric power, the electric power originating from the external power supply; a relay having a relay contact connected in parallel to the main power switch, and an excitation coil that, in an excited state, closes the relay contact, and, when the excitation coil is in a non-excited state, opens the relay contact; a control section controlling the power supplying switch such that, in a first case that the main power switch is turned to the on position by the user and the auxiliary power switch is then turned to the on position by the user, the control section outputs a control signal to turn on the power supplying switch, in a second case that the auxiliary power switch is turned to the off position by the user and then the main power switch is turned to the off position by the user, the control section outputs the control signal to turn off the power supplying switch, in a third case that the main power switch is turned to the off position by the user and then the auxiliary power switch is turned to the off position by the user, the control section maintains the power supplying switch in the on position from a timing at which the main power switch is turned to the off position until a timing at which the auxiliary power switch is then turned to the off position; and a driving section that drives the relay such that, in the first case that the main power switch is turned to the on position by the user and the auxiliary power switch is then turned to the on position by the user, the driving section drives the excitation coil to an excited state and maintains the excited state, when the auxiliary power switch is turned to the off position by the user, the driving section drives the excitation coil to be in the non-excited state, and in the third case that the main power switch is turned to the off position by the user and then the auxiliary power switch is turned to the off position by the user, the driving section drives the excitation coil to maintain the excited state, wherein the auxiliary power switch remains in the on position while the electric power is being supplied to the power supplying switch, and wherein, in response to the main power switch being in the off position, the electric power from the external power through the main power switch is cut off.