Rectifying circuit for a multiphase electric machine
AssigneeGM Global Technology Operations LLC
InventorsChandra S. Namuduri, Kenneth J. Shoemaker
Life of this patent
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Abstract
Cathode-anode voltage across free-wheeling diodes in an active rectifier is used in the determination of switching points when the free-wheeling diode is forward biased. Hysteretic switching is accomplished through the selection of conductive and non-conductive switching threshold. The switching thresholds are further selected to prevent voltage oscillations at zero current crossings and reduce delays during deactivation to prevent cross-conduction.
Claims22
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.
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.
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.
Dependencies are inferred from the claim text.