Power converter, motor driving unit, and electric power steering device
A power converter to convert power from a power supply into power supplied to a motor including n-phase windings, where n is an integer of 3 or more, in which first ends thereof are Y-connected and includes an inverter connected to second ends of the n-phase windings, a phase separation relay circuit to switch connection and disconnection between the power supply and the n-phase windings for each phase, a neutral point leg connected to a neutral point node of the motor, in which the first ends of the n-phase windings are Y-connected, and a neutral point separation relay circuit to switch connection and disconnection between the power supply and the neutral point node.
1. A power converter to convert power from a power supply into power supplied to a motor including n-phase windings, where n is an integer of 3 or more, in which first ends thereof are Y-connected, the power converter comprising:
an inverter connected to second ends of the n-phase windings and including n legs each including a low-side switching element and a high-side switching element;
a phase separation relay circuit to switch connection and disconnection between the power supply and the n-phase windings for each phase;
a neutral point leg including a low-side switching element and a high-side switching element and connected to a neutral point node of the motor, in which the first ends of the n-phase windings are Y-connected; and
a neutral point separation relay circuit to switch connection and disconnection between the power supply and the neutral point node; wherein
the phase separation relay circuit is connected between the inverter and the second ends of the n-phase windings and switches connection and disconnection between the n legs of the inverter and the second ends of the n-phase windings for each phase;
the neutral point separation relay circuit switches connection and disconnection between the power supply and the neutral point leg; and
the phase separation relay circuit incudes n phase separation relays connected between the n legs of the inverter and the second ends of the n-phase windings, and the neutral point separation relay circuit includes a first neutral point separation relay connected between a high-side node to which the n legs of the inverter are connected and the high-side switching element of the neutral point leg and a second neutral point separation relay connected between a low-side node to which the n legs of the inverter are connected and the low-side switching element of the neutral point leg.
2. The power converter of claim 1 , wherein the neutral point leg is connected between low-side and high-side nodes to which the n legs of the inverter are connected.
3. The power converter of claim 1 , wherein the phase separation relay circuit switches connection and disconnection between the power supply and the inverter for each phase.
4. The power converter of claim 3 , wherein the neutral point separation relay circuit is connected between the neutral point leg and the neutral point node and switches connection and disconnection between the neutral point leg and the neutral point node.
5. The power converter of claim 3 , wherein the neutral point separation relay circuit switches connection and disconnection between the power supply and the neutral point leg.
6. The power converter of claim 4 , wherein the phase separation relay circuit includes n first phase separation relays in the inverter connected between the high-side node to which the n legs of the inverter are connected and the n high-side switching elements and n second phase separation relays in the inverter connected between the low-side node to which the n legs of the inverter are connected and the n low-side switching elements, and the neutral point separation relay circuit includes first and second neutral point separation relays connected in series.
7. The power converter of claim 6 , wherein each of the first and second neutral point separation relays includes a diode, the first neutral point separation relay connected to the neutral point leg is disposed such that a forward current flows in the diode toward the neutral point node, and the second neutral point separation relay connected to the neutral point node is disposed such that a forward current flows in the diode toward the neutral point leg.
8. The power converter of claim 5 , wherein the phase separation relay circuit includes n first phase separation relays in the inverter connected between the high-side node to which the n legs of the inverter are connected and the n high-side switching elements, and n second phase separation relays in the inverter connected between the low-side node to which the n legs of the inverter are connected and the n low-side switching elements, and the neutral point separation relay circuit includes a first neutral point separation relay connected between the high-side node and the high-side switching element of the neutral point leg and a second neutral point separation relay connected between the low-side node and the low-side switching element of the neutral point leg.
9. The power converter of claim 1 , wherein the neutral point separation relay circuit is connected between the neutral point leg and the neutral point node and switches connection and disconnection between the neutral point leg and the neutral point node.
10. The power converter of claim 9 , wherein the phase separation relay circuit includes n phase separation relays connected between the n legs of the inverter and the second ends of the n-phase windings, and the neutral point separation relay circuit includes first and second neutral point separation relays connected in series.
11. The power converter of claim 1 , wherein a control mode in a normal state and a control mode in an abnormal state are included as control modes of power conversion, and the phase separation relay circuit is turned on and the neutral point separation relay circuit is turned off in the control mode in a normal state.
12. The power converter of claim 11 , wherein the neutral point separation relay circuit is turned on in the control mode in an abnormal state.
13. The power converter of claim 6 , wherein a control mode in a normal state and a control mode in an abnormal state are included as control modes of power conversion, and when n-2 legs of the n legs have failed, in the control in an abnormal state, n-2 first phase separation relays and n-2 second phase separation relays of the n-2 failed legs among the n first phase separation relays and the n second phase separation relays are turned off, two first phase separation relays and two second phase separation relays of two non-failed legs are turned on, and the neutral point separation relay circuit is turned on.
14. A motor driving unit comprising:
the power converter according to claim 1 ;
a motor; and
a control circuit to control the power converter.
15. An electric power steering device, comprising:
the motor driving unit of claim 14 ;
a steering system; and
an auxiliary torque mechanism generating an auxiliary torque.