Patent ID: 8456879

Claim:
A switching power supply apparatus for converting a first output having a DC waveform supplied from a DC power supply to a second output having an AC waveform and supplying the second output to a load, the switching power supply apparatus comprising: a first series connection unit in which a first electronic switch, a first inductor and a second electronic switch are connected in this order, an end on a first electronic switch side is connected to a positive side of the DC power supply and an end on a second electronic switch side is connected to a negative side of the DC power supply; a first diode having a cathode connected to the positive side of the DC power supply and an anode connected to a connection point between the first inductor and the second electronic switch; a second diode having an anode connected to the negative side of the DC power supply and a cathode connected to a connection point between the first electronic switch and the first inductor; a second inductor having one end connected to the connection point between the first inductor and the second electronic switch; a second series connection unit in which a third electronic switch, a third inductor and a fourth electronic switch are connected in this order, an end on a third electronic switch side is connected to the positive side of the DC power supply and an end on a fourth electronic switch side is connected to the negative side of the DC power supply; a third diode having a cathode connected to the positive side of the DC power supply and an anode connected to a connection point between the third indictor and the fourth electronic switch; a fourth diode having an anode connected to the negative side of the DC power supply and a cathode connected to a connection point between the third electronic switch and the third inductor; a fourth inductor having one end connected to the connection point between the third inductor and the fourth electronic switch; a capacitor connected between an other end of the second inductor and an other end of the fourth inductor; and an electronic switch control circuit for causing only the first electronic switch to perform a switching operation during a period in which the second electronic switch is held in an off state and the fourth electronic switch is held in an on state and causing only the third electronic switch to perform a switching operation during a period in which the second electronic switch is held in an on state and the fourth electronic switch is held in an off state, wherein the load is connected between the other end of the second inductor and the other end of the fourth inductor, and the electronic switch control circuit causes the first and third electronic switches to repeatedly switch between on and off at a frequency higher than a frequency of the second output supplied to the load and causes the second and fourth electronic switches to alternately switch between an on state and an off state at the frequency of the second output.