PROTECTION CIRCUIT FOR PERMANENT MAGNET SYNCHRONOUS MOTOR IN FILED WEAKENING OPERATION

• US 20070063661A1
• Filed: 09/20/2006
• Published: 03/22/2007
• Est. Priority Date: 09/21/2005
• Status: Active Grant

• Current Assignee: Infineon Technologies Americas Corp. (Infineon Technologies AG)
• Original Assignee: International Rectifier Corporation (Infineon Technologies AG)
• Inventors: Bocchiola, Cesare, Galli, Giovanni, Grasso, Massimo
• Granted Patent: US 7,554,276 B2
• Time in Patent Office: Days
• US Class Current: 318/109
• CPC Class Codes: H02M 1/0006 Arrangements for supplying an adequate voltage to the control circuit of converters
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 7/5387 in a bridge configuration
• CPC Class Codes: H02P 3/06 for stopping or slowing an individual dynamo-electric motor or dynamo-electric converter
• CPC Class Codes: H02P 3/22 by short-circuit or resistive braking
• CPC Class Codes: H02P 6/24 Arrangements for stopping
• CPC Class Codes: H03K 17/6877 the control circuit comprising active elements different from those used in the output circuit
• CPC Class Codes: H03K 2017/6875 using self-conductive, depletion FETs

Abstract

A safety circuit for providing protection against failures that impact safety of an inverter circuit driving a Permanent Magnet Synchronous Motor (PMSM) including high and low side switches connected in a bridge and driven by a gate driver circuit during operation of the PMSM in a field weakening mode, the gate driver circuit including stages for driving the high and low side switches, the safety circuit comprising a main power supply and a back-up power supply for supplying voltage to the gate driver circuit driving the switches of the bridge of the inverter circuit, wherein if the main power supply fails to deliver adequate power to the gate driver circuit, the back-up power supply provides power to the gate driver circuit to allow the gate driver circuit to turn ON the low side switches and turn OFF the high side switches.

Claims

1. A safety circuit for providing protection against failures that impact safety of an inverter circuit driving a Permanent Magnet Synchronous Motor (PMSM) including high and low side switches connected in a bridge and driven by a gate driver circuit during operation of the PMSM in a field weakening mode, the gate driver circuit including stages for driving the high and low side switches, the high and low side switches being connected to the motor terminals, the safety circuit comprising:

a main power supply for supplying a main power supply voltage and a back-up power supply for supplying a back-up power supply voltage to the gate driver circuit driving the switches of the bridge of the inverter circuit,

wherein if the main power supply fails to deliver adequate electrical power to the gate driver circuit, the back-up power supply provides power to the gate driver circuit to allow the gate driver circuit to turn ON the low side switches and turn OFF the high side switches.

2. The safety circuit of claim 1, wherein the safety circuit is utilized in an automatic clothes washer.

3. The safety circuit of claim 1, wherein turning ON the low side switches of the bridge short circuits the terminals of the motor and causes a reduction in motor speed and controls voltages generated in the motor to a safe level.

4. The safety circuit of claim 1, further comprising a driver stage in the gate driver circuit for each low side switch providing a gate drive signal to the low side switch, the driver stage receiving power from the back-up power supply when power from the main power supply fails and biasing the driver stage, whereby when a pre-driver signal to the driver stage fails when the main power supply voltage fails, the driver stage produces a gate drive signal to turn the low side switches ON to short circuit the motor.

5. The safety circuit of claim 4, further comprising a pre-driver stage in the gate driver circuit driving a latch stage having an output provided to an input of a driver driving a high side switch, and wherein the back-up power supply voltage is provided to bias the pre-driver stage when the main power supply fails, whereby when a pre-driver signal to the pre-driver stage fails when the main power supply fails, the pre-driver stage provides an output to cause the high side switch to be turned OFF.

6. The safety circuit of claim 1, wherein the inverter circuit includes a rectifier providing a DC bus voltage from an AC source to a DC bus and an inverter having its input coupled to the DC bus, a DC bus storage capacitor being coupled across the DC bus, the back-up power supply receiving power from energy stored in the DC bus capacitor when the main power supply fails.

7. The safety circuit of claim 1, further comprising a selection circuit for providing the back-up power supply voltage to the gate driver circuit when the main power supply fails.

8. The safety circuit of claim 7, wherein the selection circuit comprises first, second and third switches, wherein the first switch is connected to the main power supply voltage, the second switch is connected to the back-up power supply voltage, and the first and second switches are connected in series, the third switch having a control electrode coupled to the main power supply voltage and being connected to control whether the second switch is on or off in dependence on the presence or absence of said main power supply voltage.

9. The safety circuit of claim 6, further comprising a resistor connected in series with the third switch.

10. The safety circuit of claim 1, wherein when the main power supply voltage is present, the back-up power supply voltage is removed from the gate driver circuit.

11. The safety circuit of claim 1, wherein the back-up power supply includes a high voltage transistor coupled to the DC bus providing a reduced voltage as the back-up power supply voltage.