Patent ID: 7006362

Claim:
A DC/DC converter comprising: two main switches connected in series; and a smoothing reactor one end of which is connected to the junction of the main switches; wherein the two main switches are alternately turned on/off and at the same time, when a first main switch, which is one of the two main switches, is turned on, the electrical energy from a direct current power supply connected to the terminal on the input side is stored in the smoothing reactor, and when a second main switch, which is the other of the two main switches, is turned on, the electrical energy stored in the smoothing reactor is discharged to a load connected to the terminal on the output side; an auxiliary resonance circuit, in which a resonance reactor and an auxiliary switch are connected in series, is comprised and at the same time a capacitive component is comprised in parallel to at least one of the two main switches, when the auxiliary switch is on, the electrical energy is supplied from the terminal on the output side to the resonance reactor and the electrical energy stored therein is used for a resonance operation of the capacitive component and the resonance reactor; a dead time during which both the first main switch and the second main switch are maintained off at the same time is provided, at the same time, at least during the period from turning-off of the second main switch to turning-on of the first main switch, the auxiliary switch is maintained on; in the period during which the second main switch is on, the auxiliary switch is turned on and at the same time, in the period during which the first main switch is on, the auxiliary switch is turned off, if the direction, in which a current flows through the second main switch when only the second main switch is on, is assumed to be the positive direction, the second main switch is turned off when the current flowing through the second main switch falls to zero or becomes negative in the period during which both the second main switch and the auxiliary switch are maintained on at the same time; a smoothing reactor current measuring means for measuring a current iL which flows through the smoothing reactor is comprised, and the second main switch is turned off is a period of time T 1 , during which both the second main switch and the auxiliary switch are maintained on at the same time, meets the condition of the following Expression 1 T 1 >Lr/V 2 [ iL +{( C 1 + C 2 )/ Lr ( V 1 2 −V 2 2 )} 1/2 ] Expression 1 where V 1 is a voltage to be applied to the smoothing reactor when the first main switch is turned on, V 2 is a voltage to be applied to the smoothing reactor when the second main switch is turned on, Lr is the inductance of the resonance reactor, C 1 is the electrostatic capacitance of the capacitive component in parallel to the first main switch, and C 2 is the electrostatic capacitance of the capacitive component in parallel to the second main switch.