Granted Patent B2

US 8,064,227 · App. 12/553,891 · Granted Nov 22, 2011

Abstract

Claims (46)

1. A rectifying apparatus for a multiphase electric machine, comprising:

an active rectifier bridge including a controllable semi-conductor switch and a free-wheeling diode having a cathode and an anode; and

a switch control circuit configured to control switching of the controllable semi-conductor switch based upon a cathode-anode voltage across the free-wheeling diode when the free-wheeling diode is forward biased;

wherein the switch control circuit is configured to control switching of the controllable semi-conductor switch conductive when the cathode-anode voltage across the free-wheeling diode is less than a first threshold voltage and to control switching of the controllable semi-conductor switch non-conductive when the cathode-anode voltage across the free-wheeling diode is greater than a second threshold voltage, wherein the first threshold voltage is less than the second threshold voltage.

2. The rectifying apparatus of claim 1 wherein the switch control circuit comprises a comparator circuit including negative and positive feedback and having an output coupled to the controllable semi-conductor switch.

3. The rectifying apparatus of claim 2 wherein the switch control circuit further comprises a buffer circuit disposed between the comparator circuit output and the controllable semi-conductor switch.

4. The rectifying apparatus of claim 1 wherein the first threshold voltage is about −10 mV and said second threshold is about −100 mV.

5. The rectifying apparatus of claim 1 wherein the second threshold voltage is about one order of magnitude greater than the first threshold voltage.

6. The rectifying apparatus of claim 1 wherein the controllable semi-conductor switch is in an upper-half of the active rectifier bridge.

7. The rectifying apparatus of claim 1 wherein the controllable semi-conductor switch is in a lower-half of the active rectifier bridge.

8. A rectifying apparatus for a multiphase electric machine, comprising:

an active rectifier bridge including a controllable semi-conductor switch and a free-wheeling diode having a cathode and an anode; and

a switch control circuit configured to control switching of the controllable semi-conductor switch based upon a cathode-anode voltage across the free-wheeling diode when the free-wheeling diode is forward biased;

wherein the switch control circuit comprises a comparator having an output coupled to a control terminal of the controllable semi-conductor switch, the comparator configured to monitor the cathode-anode voltage across the free-wheeling diode, compare the cathode-anode voltage to a first threshold voltage when the output coupled to the control terminal of the controllable semi-conductor switch is controlling the controllable semi-conductor non-conductive, and compare the cathode-anode voltage to a second threshold voltage when the output coupled to the control terminal of the controllable semi-conductor switch is controlling the controllable semi-conductor conductive, wherein the first threshold voltage is less than the second threshold voltage, and wherein the comparator output controls the controllable semi-conductor conductive from non-conductive when the cathode-anode voltage across the free-wheeling diode crosses the first threshold voltage and the comparator output controls the controllable semi-conductor non-conductive from conductive when the cathode-anode voltage across the free-wheeling diode crosses the second threshold voltage.

9. The rectifying apparatus of claim 1 further comprising a load dump protection circuit.

10. The rectifying apparatus of claim 1 wherein the controllable semi-conductor switch comprises a MOSFET device and the free-wheeling diode comprises an intrinsic body diode.

11. The rectifying apparatus of claim 1 wherein the controllable semi-conductor switch comprises one of a MOSFET device, a JFET device, an IGBT device and a BJT device.

12. The rectifying apparatus of claim 1 wherein the switch control circuit is configured to control switching of the controllable semi-conductor switch conductive at about 10 microseconds to about 1 millisecond subsequent to a zero current crossing event.

13. A method for controlling a rectifying apparatus for a multiphase electric machine, comprising:

monitoring a voltage across a free-wheeling diode corresponding to a controllable semi-conductor switch; and

controlling the switching of the controllable semi-conductor switch based upon the voltage across the free-wheeling diode when the free-wheeling diode is forward biased;

wherein controlling the switching of the controllable semi-conductor switch based upon the voltage across the free-wheeling diode when the free-wheeling diode is forward biased comprises:

measuring a cathode-anode voltage of the free-wheeling diode;

switching the controllable semi-conductor switch conductive when the cathode-anode voltage across the free-wheeling diode is less than a first threshold voltage; and

switching the controllable semi-conductor switch non-conductive when the cathode-anode voltage across the free-wheeling diode is greater than a second threshold voltage;

wherein the first threshold voltage is less than the second threshold voltage.

14. The method for controlling a rectifying apparatus of claim 13 wherein the first threshold voltage is about −10 mV and said second threshold is about −100 mV.

15. The method for controlling a rectifying apparatus of claim 13 wherein the second threshold voltage is about one order of magnitude greater than the first threshold voltage.

16. A method for controlling a rectifying apparatus for a multiphase electric machine, comprising:

monitoring a voltage across a free-wheeling diode corresponding to a controllable semi-conductor switch; and

controlling the switching of the controllable semi-conductor switch based upon the voltage across the free-wheeling diode when the free-wheeling diode is forward biased.

wherein controlling the switching of the controllable semi-conductor switch based upon the voltage across the free-wheeling diode when the free-wheeling diode is forward biased comprises:

monitoring a cathode-anode voltage across the free-wheeling diode;

comparing the cathode-anode voltage to a first threshold voltage when the controllable semi-conductor switch is non-conductive;

comparing the cathode-anode voltage to a second threshold voltage when the controllable semi-conductor switch is conductive;

controlling the controllable semi-conductor conductive from non-conductive when the cathode-anode voltage across the free-wheeling diode crosses the first threshold voltage; and

controlling the controllable semi-conductor non-conductive from conductive when the cathode-anode voltage across the free-wheeling diode crosses the second threshold voltage;

wherein the first threshold voltage is less than the second threshold voltage.

17. The method for controlling a rectifying apparatus of claim 13 further comprising monitoring a rotational speed of the multiphase electric machine and controlling the controllable semi-conductor switch nonconductive when the rotational speed is below a predetermined threshold speed.

18. The method for controlling a rectifying apparatus of claim 13 further comprising switching the controllable semi-conductor switch conductive at about 10 microseconds to about 1 millisecond subsequent to a zero current crossing event.

19. A rectifying apparatus for a multiphase electric machine comprising:

a rectifying bridge circuit comprising a plurality of paired controllable semi-conductor switches, each semi-conductor switch having an associated free-wheeling diode having a cathode and an anode;

a local bias power supply circuit;

a plurality of switch control circuits, each switch control circuit associated with one of the semi-conductor switches of the rectifying bridge circuit; and

each switch control circuit including a comparator circuit including negative and positive feedback and having an output coupled to a control terminal of the controllable semi-conductor switch, the comparator circuit configured to monitor a cathode-anode voltage across the free-wheeling diode, compare the cathode-anode voltage to a first threshold voltage when the output coupled to the control terminal of the controllable semi-conductor switch is controlling the controllable semi-conductor non-conductive, and compare the cathode-anode voltage to a second threshold voltage when the output coupled to the control terminal of the controllable semi-conductor switch is controlling the controllable semi-conductor conductive, wherein the first threshold voltage is less than the second threshold voltage, and wherein the comparator output controls the controllable semi-conductor conductive from non-conductive based upon the cathode-anode voltage across the free-wheeling diode crossing the first threshold voltage and the comparator output controls the controllable semi-conductor non-conductive from conductive based upon the cathode-anode voltage across the free-wheeling diode crossing the second threshold voltage.

20. The rectifying apparatus of claim 19 wherein the comparator output controls the controllable semi-conductor conductive from non-conductive at about 10 microseconds to about 1 millisecond subsequent to a zero current crossing event.

Assignments (8)