POLYPHASE ELECTRIC MOTOR CONTROL DEVICE

• US 20180302008A1
• Filed: 04/12/2018
• Published: 10/18/2018
• Est. Priority Date: 04/12/2017
• Status: Active Grant

• Current Assignee: Omron Automotive Electronics Company Limited (Nidec Corporation)
• Original Assignee: Omron Automotive Electronics Company Limited (Nidec Corporation)
• Inventors: Mori, Yoji, Ogasawara, Taku, Doba, Satoshi
• Granted Patent: US 10,454,396 B2
• Time in Patent Office: Days
• CPC Class Codes: H02P 27/08 with pulse width modulation
• CPC Class Codes: H02P 27/085 wherein the PWM mode is adapted on the running conditions of the motor, e.g. the switching frequency
• CPC Class Codes: H02P 6/15 Controlling commutation time

Abstract

A polyphase electric motor control device stores a first threshold as a duty cycle at which noise caused by a high potential-side switching element starts to overlap a first measurement period, and a second threshold as a duty cycle at which time when a low potential-side switching element is switched from on to off is after an end of a second measurement period, makes a first judgment for comparing a maximum target duty cycle with the first threshold, and a second judgment for comparing a second greatest target duty cycle with the second threshold, measures a current in the first measurement period when the maximum target duty cycle is smaller than the first threshold, and measures a current in the second measurement period when the maximum target duty cycle is greater than the first threshold and the second greatest target duty cycle is smaller than the second threshold.

Claims

1. A polyphase electric motor control device controlling a polyphase electric motor, the polyphase electric motor control device comprising:

a bridge circuit configured by connecting in parallel phase circuits corresponding to each phase of the polyphase electric motor, each of the phase circuits including in series a high potential-side switching element, a low potential-side switching element, and a current detector provided on a low-potential side with respect to the low potential-side switching element and configured to detect a phase current value;

a controller configured to measure a current flowing through the current detector in one of a first measurement period and a second measurement period in which measurement is started later than the first measurement period and configured to calculate a control signal for controlling a current fed to each of the phase circuits; and

a PWM controller configured to periodically calculate a target duty cycle of a PWM signal for driving each of the low potential-side switching element and the high potential-side switching element, the target duty cycle being calculated according to the control signal,

wherein the controller is

configured to store a first threshold which is a duty cycle at which switching noise caused by the high potential-side switching element of each of the phase circuits starts to overlap the first measurement period, and a second threshold which is a duty cycle at which time when the low potential-side switching element of each of the phase circuits is switched from on to off is after an end of the second measurement period,

configured to make a first judgment for comparing a maximum target duty cycle among the target duty cycles with the first threshold, and a second judgment for comparing a second greatest target duty cycle among the target duty cycles with the second threshold,

configured to measure the current in the first measurement period when a result of the first judgment indicates that the maximum target duty cycle is smaller than the first threshold, and

configured to measure the current in the second measurement period when a result of the first judgment indicates that the maximum target duty cycle is greater than the first threshold and a result of the second judgment indicates that the second greatest target duty cycle is smaller than the second threshold.

2. The polyphase electric motor control device according to claim 1, wherein a start time of the second measurement period is a time point at which noise converges, the noise being generated upon switching from off to on of the high potential-side switching element of the phase circuit when the phase circuit is driven at a duty cycle of the first threshold.

3. The polyphase electric motor control device according to claim 1, wherein a start time of the first measurement period is delayed by a predetermined delay time from a center of the PWM signal.

5. The polyphase electric motor control device according to claim 2, wherein a start time of the first measurement period is delayed by a predetermined delay time from a center of the PWM signal.

4. A polyphase electric motor control device controlling a polyphase electric motor, the polyphase electric motor control device comprising:

a bridge circuit configured by connecting in parallel phase circuits corresponding to each phase of the polyphase electric motor, each of the phase circuits including in series a high potential-side switching element, a low potential-side switching element, and a current detector provided on a low-potential side with respect to the low potential-side switching element and configured to detect a phase current value;

a controller configured to measure a current flowing through the current detector in one of a first measurement period and a second measurement period in which measurement is started later than the first measurement period and configured to calculate a control signal for controlling a current fed to each of the phase circuits; and

a PWM controller configured to periodically calculate a target duty cycle of a PWM signal for driving each of the low potential-side switching element and the high potential-side switching element, the target duty cycle being calculated according to the control signal,

wherein the controller is

configured to store a first threshold which is an off time of the high potential-side switching element of the phase circuit having a maximum target duty cycle among the target duty cycles in a case where switching noise caused by the high potential-side switching element of the phase circuit having the maximum target duty cycle starts to overlap the first measurement period, and a second threshold which is an on time of the low potential-side switching element of the phase circuit having a second greatest target duty cycle among the target duty cycles in a case where the low potential-side switching element of the phase circuit having the second greatest target duty cycle is switched from on to off is after an end of the second measurement period,

configured to make a first judgment for comparing the off time of the high potential-side switching element of the phase circuit having the maximum target duty cycle with the first threshold, and a second judgment for comparing the on time of the low potential-side switching element of the phase circuit having the second greatest target duty cycle with the second threshold,

configured to measure the current in the first measurement period when a result of the first judgment indicates that the off time of the high potential-side switching element of the phase circuit having the maximum target duty cycle is not smaller than the first threshold, and

configured to measure the current in the second measurement period when a result of the first judgment indicates that the off time of the high potential-side switching element of the phase circuit having the maximum target duty cycle is smaller than the first threshold and a result of the second judgment indicates that the on time of the low potential-side switching element of the phase circuit having the second greatest target duty cycle is greater than the second threshold.