Patent ID: 8143836

Claim:
A motor controller comprising: a converter that converts input AC power into DC power; an inverter that inverts the converted DC power into AC power; a DC link that connects said converter and said inverter; and a capacitor and a charging/discharging control circuit that are connected in parallel with said DC link so that electrical energy is supplied from said DC link to said capacitor and vice versa through said charging/discharging control circuit, wherein said charging/discharging control circuit includes a discharge circuit that is adapted to perform a step-up operation of raising a voltage of said capacitor and a step-down operation of lowering a voltage of said capacitor while the electrical energy charged in said capacitor is discharged; and said motor controller further comprises first switching means that switches operations of the discharge circuit based on comparison between a voltage of said capacitor and a voltage of said DC link so that the discharge circuit performs the step-down operation when the voltage of said capacitor is higher than the voltage of said DC link, and performs the step-up operation when the voltage of said capacitor becomes lower than the voltage of said DC link.