Power conversion apparatus and control method for power conversion apparatus

A power conversion apparatus which converts a direct current into an N-phase alternate current (N is an integer equal to 3 or greater), and supplies the converted N-phase alternate current to an inductor working as a load and provided for each phase, said power conversion apparatus comprising:

• 2N arms each including a switching unit having a field-effect transistor representing a switching element and a diode connected in parallel, said switching element becoming conductive according to a control signal to be supplied, so that a flow path of a regenerative current of the inductor is formed, said diode having the regenerative current of the inductor flow in a forward direction, and said field-effect transistor being placed so that the regenerative current of the inductor flows from a source toward a drain on said field-effect transistor;
• N legs each provided in a corresponding one of N-phases, formed with said 2N arms serially connected in a pair, having ends connected to a direct-current power source, and having a mid point connected to an inductor of the corresponding one of the N-phases;
• a load current determining unit configured to determine an amount of a current flowing into an inductor provided in each of the N-phases;
• a threshold designating unit configured to designate a threshold which is predetermined based on a comparison between (i) on-resistance of said switching element in the case where a current in a same amount flows through said switching element in the forward direction with respect to said diode and (ii) on-resistance of said diode in the case where a current in a same amount flows through said diode;
• and
• a prohibition control unit configured to prohibit supplying the control signal to said switching element included in said leg of the corresponding N-phase, in the case where the amount of the current, for each of the N-phases, determined by said load current determining unit is greater than the threshold designated by said threshold designating unit.

A method of controlling a power conversion apparatus which obtains a regulated voltage or a regulated current by intermittently supplying power from a power source to an inductor,

• wherein the power conversion apparatus includes a switching unit which has a field-effect transistor representing a switching element and a diode connected in parallel, the switching element becoming conductive according to a control signal to be supplied, so that a flow path of a regenerative current of the inductor is formed, the diode having the regenerative current of the inductor flow in a forward direction, and the field-effect transistor being placed so that the regenerative current of the inductor flows from a source toward a drain on the field-effect transistor, and
• said method comprises:
• measuring either an amount of a current flowing into the switching unit, or a voltage generated across said switching unit;
• designating a threshold which is predetermined based on a comparison between (i) on-resistance of the switching element in the case where a current in a same amount flows through the switching element in the forward direction with respect to the diode and (ii) on-resistance of the diode in the case where a current in a same amount flows through the diode;
• and
• prohibiting supplying the control signal to the switching element in the case where either the amount of the current, the amounts of the voltages measured in said measuring are greater than the threshold designated in said designating.

A method of controlling a power conversion apparatus which converts a direct current into an N-phase alternate current (N is an integer equal to 3 or greater), and supplies the converted N-phase alternate current to an inductor working as a load and provided for each phase,

• wherein the power conversion apparatus includes:
• 2N arms each including a switching unit having a field-effect transistor representing a switching element and a diode connected in parallel, said switching element becoming conductive according to a control signal which is supplied, so that a flow path of a regenerative current of the inductor is formed, the diode having the regenerative current of the inductor flow in a forward direction, and the field-effect transistor being placed so that the regenerative current of the inductor flows from a source toward a drain on the field-effect transistor;
• and
• N legs each provided in a corresponding one of N-phases, formed with said 2N arms serially connected in a pair, having ends connected to a direct current power source, and having a mid point connected to an inductor of a phase, included in the N-phases, corresponding to the mid point, and
• said method comprises:
• determining an amount of a current flowing into an inductor provided in each of the N-phases;
• designating a threshold which is predetermined based on a comparison between (i) on-resistance of the switching element in the case where a current in a same amount flows through the switching element in the forward direction with respect to the diode and (ii) on-resistance of the diode in the case where a current in a same amount flows through the diode;
• and
• prohibiting supplying the control signal to the switching element included in the leg of the corresponding N-phase, in the case where the amount of the current, for each of the N-phases, determined in said determining is greater than the threshold designated in said designating.