Motor drive circuitry

Patent metadata

Field	Value
Publication number	US-12525909-B2
Application number	US-202418406503-A
Country	US
Kind code	B2
Filing date	Jan 8, 2024
Priority date	Jan 10, 2023
Publication date	Jan 13, 2026
Grant date	Jan 13, 2026

Abstract

A motor drive circuit comprising: a motor bridge, comprising a bridge arm comprising upper and lower switches for each motor phase, which may be selectively closed to modulate voltage applied to the respective phases to drive signals from a motor control circuit, at least one solid-state-phase-isolation-relay (SSPIR) provided in series in an electrical path connecting a respective phase of the motor to a respective bridge arm, the SSPIR being closed in normal operation so that current can flow in the phase and held open in a fault mode of operation to prevent current flow, a monitoring arrangement for monitoring a current waveform in the phase to identify when it is safe to open the SSPIR without causing damage to the SSPIR due to an avalanche mode, and a control circuit that applies a voltage to each SSPIR that is sufficient to hold the SSPIR closed in normal operation is only opened when the current is in a safe operational area.

First claim

The invention claimed is:

1 . A motor drive circuit for use in driving a motor having two or more phases, the motor drive circuit comprising:
a motor bridge having, for each phase of the motor, a bridge arm comprising an upper switch and a lower switch that in normal operation may be opened and closed to modulate voltage applied to the respective phases in response to drive signals from a motor control circuit, at least one solid state phase isolation relay (SSPIR) that is provided in series in an electrical path connecting a respective phase of the motor to a respective bridge arm, the SSPIR being closed in normal operation so that current can flow in the phase and is held open in a fault mode of operation to prevent the flow of current in the phase, a monitoring arrangement for monitoring a current waveform in the phase to identify when the current is within a safe operational area in which it is safe to open the SSPIR without causing damage to the SSPIR due to an avalanche mode, the safe operational area comprising a period of time in which both the current flowing in the motor phase is in the opposite direction to a body diode of the SSPIR and the magnitude of the current is below a safe threshold level, and a control circuit that during normal operation applies a voltage to each SSPIR that is sufficient to hold the SSPIR closed, in which the motor drive circuit is arranged such that the SPPIR is only opened at a time when the current is in the safe operational area and not when the current flowing in the phase is both flowing in the motor phase in the opposite direction as the body diode of the SSPIR and the magnitude of the current is above a safe threshold level.

2 . A motor drive circuit according to claim 1 in which the monitoring arrangement further comprises a bridge monitor circuit that monitors the condition of the motor bridge to determine that a fault condition is present where a switch of the bridge is not operating correctly and in response outputs a fault signal that is fed to the current control circuit to initiate an opening of the at least one SSPIR at an appropriate time when the conditions of the safe operational area are satisfied.

3 . A motor drive circuit according to claim 2 in which in an event that the bridge monitor circuit detects a fault it immediately outputs the fault signal and the monitor arrangement delays a time at which the fault signal is fed to the control circuit until the current in the phase of the at least one SSPIR is in the safe operational area.

4 . A motor drive circuit according to claim 3 , wherein the control circuit normally applies a positive voltage to the SSPIR to hold the SSPIR closed and upon receipt of the fault signal applies a lower or zero voltage to the SSPIR to initiate the opening of the SSPIR.

5 . A motor drive circuit according to claim 3 , wherein the control circuit includes a voltage clamp which is configured to clamp the voltage at a drain of the SSPIR to a safe level insufficient to cause failure of the SSPIR following an initiation of the opening of the SSPIR thereby extending a width of the safe operational area by increasing a maximum phase current at which the SSPIR can be safely opened.

6 . A motor drive circuit according to claim 5 in which the voltage at the drain is clamped to a level below that which will cause damage to the SSPIR but above a maximum phase voltage that is expected due to back emf from rotation of the motor.

7 . A motor drive circuit according to claim 1 , wherein the control circuit normally applies a positive voltage to the SSPIR to hold the SSPIR closed and upon receipt of the fault signal applies a lower or zero voltage to the SSPIR to initiate the opening of the SSPIR.

8 . A motor drive circuit according to in claim 1 , wherein the control circuit includes a voltage clamp which is configured to clamp the voltage at a drain of the SSPIR to a safe level insufficient to cause failure of the SSPIR following an initiation of the opening of the SSPIR thereby extending a width of the safe operational area by increasing a maximum phase current at which the SSPIR can be safely opened.

9 . A motor drive circuit according to claim 8 in which the voltage at the drain is clamped to a level below that which will cause damage to the SSPIR but above a maximum phase voltage that is expected due to back emf from rotation of the motor.

10 . A motor circuit according to claim 9 in which the voltage clamp circuit comprises at least one Zener diode which is connected in series between the drain and the gate of the SSPIR.

11 . A motor drive circuit according to claim 10 in which the control circuit includes a resistor that connects the gate of the SSPIR to a source of the SSPIR to fix a source voltage to a gate voltage.

12 . A motor circuit according to claim 8 in which the voltage clamp circuit comprises at least one Zener diode which is connected in series between the drain and the gate of the SSPIR.

13 . A motor drive circuit according to claim 12 in which the control circuit includes a resistor that connects the gate of the SSPIR to a source of the SSPIR to fix a source voltage to a gate voltage.

14 . A method of driving a motor that has multiple phases, each phase of the motor being connected to a bridge driver through a respective solid state phase isolation relay (SSPIR), the method comprising, in an event of a fault event in a switch of the bridge driver performing the following steps in order:
monitoring a current waveform in a phase of the motor to identify when the current is within a safe operational area in which it is safe to open the SSPIR of that phase without causing damage to the SSPIR due to an avalanche mode, the safe operational area comprising a period of time in which both the current flowing in the motor phase is in the opposite direction to a body diode of the SSPIR and a magnitude of the current is below a safe threshold level, and initiating opening of the SSPIR only at an identified time when the current is in the safe operational area and not when the current flowing in the phase is both flowing in the motor phase in the opposite direction as the body diode of the SSPIR and the magnitude of the current is above a safe threshold level.

Assignees

• Zf Automotive Uk Ltd

Inventors

• Terdy Tamas
• Cockerham Kevin

Classifications

• H02P23/14 Primary

  Estimation or adaptation of motor parameters, e.g. rotor time constant, flux, speed, current or voltage · CPC title

• H02P25/22

  Multiple windings; Windings for more than three phases · CPC title

• H02P29/40

  Regulating or controlling the amount of current drawn or delivered by the motor for controlling the mechanical load · CPC title

• B62D5/0481

  monitoring the steering system, e.g. failures · CPC title

• H02P25/18 Primary

  with arrangements for switching the windings, e.g. with mechanical switches or relays · CPC title