The PCU (700) includes a smoothing capacitor (C2) and a filter capacitor (C1) arranged electrically nearer to the battery (900) than the smoothing capacitor (C2).

Here, the smoothing capacitor (C2) is cooled by the cooling water (1350) while the filter capacitor (C1) is cooled by the oil (1050).

Specifically, a voltage smoothing circuit (14) is provided with a first smoothing capacitor (C1), a second smoothing capacitor (C2), a balance resistance (R3) and a zener diode (RZ4).

  The input smoothing capacitor (C1) smoothes an input voltage.

A smoothing circuit (15) has a smoothing capacitor (C) connected between a pair of power supply lines (L1,L2).

The first smoothing capacitor (C1) and the second smoothing capacitor (C2) are connected in series to each other and connected in parallel to a power supply unit (13).

This invention is to reduce a voltage across a smoothing capacitor in a single-phase capacitorless inverter.

A smoothing capacitor (140) is arranged outside the semiconductor module.

At the downstream stage of the inverter circuit (100), there are provided a smoothing capacitor (11) that is connected by way of a rectifying diode (10), and a short-circuiting switch (9) that bypasses the smoothing capacitor (11).

Even if the internal resistance of a smoothing capacitor varies, voltage higher than or equal to the rated voltage of the smoothing capacitor is prevented from being applied to the capacitor by a simple configuration.

A smoothing capacitor (C1) is connected to an output of the rectifying circuit (10).

The damping resistor (6) is connected only to the surge absorption capacitor (7) and is not connected to the smoothing capacitor (8).

A first synchronous rectification element (Q4), a second synchronous rectification element (Q3), a first smoothing capacitor (C3), and a second smoothing capacitor (C2) are connected to the a secondary coil (Ns11) of the transformer (MT).

For the purpose of smoothing the output signal, a smoothing capacitor (C2) can be connected to an output terminal (OUT) of the optocoupler (U1).

The balance resistance (R3) is connected in parallel to the first smoothing capacitor (C1).