Brushless motor drive device

• US 10,199,966 B2
• Filed: 03/05/2015
• Issued: 02/05/2019
• Est. Priority Date: 05/28/2014
• Status: Expired due to Fees

• Current Assignee: Panasonic Intellectual Property Management Co., Ltd. (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Intellectual Property Management Co., Ltd. (Panasonic Holdings Corporation)
• Inventors: Sato, Daisuke
• Primary Examiner(s): Santana, Eduardo Colon
• Assistant Examiner(s): Cook, Cortez M
• Application Number:
  US15/310,721
• Publication Number:
  US 20170077852A1
• Time in Patent Office: 1,433 Days
• Field of Search: 318490
• CPC Class Codes: G05B 19/409 characterised by using manual data input [MDI] or by using control panel, e.g. controlling functions with the panel; characterised by control panel details or by setting parameters G05B19/408, G05B19/4093 take precedence
• CPC Class Codes: G06F 1/04 Generating or distributing clock signals or signals derived directly therefrom
• CPC Class Codes: G06F 11/1604 where the fault affects the clock signals of a processing unit and the redundancy is at or within the level of clock signal generation hardware
• CPC Class Codes: H02P 21/22 Current control, e.g. using a current control loop
• CPC Class Codes: H02P 23/00 Arrangements or methods for the control of AC motors characterised by a control method other than vector control
• CPC Class Codes: H02P 29/04 by means of a separate brake
• CPC Class Codes: H02P 6/18 without separate position detecting elements
• CPC Class Codes: H02P 6/28 Arrangements for controlling current H02P6/10 takes precedence

Abstract

A brushless motor drive device includes the following: an inverter circuit configured to energize and drive the winding of a brushless motor; a current detection circuit configured to detect the current value of the winding; a control unit configured to control the rotation of the motor; and an RC filter including a resistor and a capacitor. The control unit includes the following: a drive control unit configured to generate a signal to drive the inverter; a clock generation circuit configured to generate a clock pulse to be used as a reference for an operation period; a pulse output circuit configured to generate a pulse signal with a changing frequency based on the clock pulse and to apply the pulse signal to the RC filter; an AD converter circuit connected to the capacitor of the RC filter and the current detection circuit; and an AD-conversion-error calculation unit configured to calculate the conversion error of the AD converter circuit. The AD-conversion-error calculation unit calculates the conversion error based on the difference between the output value of the AD converter circuit produced in response to an input of the voltage of the capacitor and an AD-converted value calculated from the charging time of the capacitor.

Claims

1. A brushless motor drive device for driving a brushless motor, the brushless motor drive device comprising:

an inverter circuit configured to energize and drive a winding of the brushless motor;

a current detection circuit configured to detect a current value of the winding;

a control unit configured to control rotation of the brushless motor; and

a resistor-capacitor (RC) filter including a resistor and a capacitor and configured such that the capacitor performs charge and discharge operations in accordance with an applied signal,

wherein the control unit includes;

a drive control unit configured to generate a signal to drive the inverter;

a clock generation circuit configured to generate a clock pulse to be used as a reference for an operation period;

a pulse output circuit configured to generate a pulse signal with a changing frequency based on the clock pulse generated by the clock generation circuit and to apply the pulse signal to the RC filter;

an analog-digital (AD) converter circuit connected to the capacitor of the RC filter and the current detection circuit, the AD convertor circuit being configured to receive analog voltages from the capacitor and the current detection circuit and convert the received analog voltages into output values indicated by digital values; and

an AD-conversion-error calculation unit configured to calculate a conversion error of the AD converter circuit, wherein;

the AD converter circuit receives a capacitor voltage of the capacitor, converts the received capacitor voltage into an actual measured value indicated by a digital value in response to the received capacitor voltage and outputs the actual measured value, the capacitor voltage being the voltage of the capacitor when the capacitor is charged for a predetermined time as a charging time corresponding to the pulse signal applied to the RC filter, and

the AD-conversion-error calculation unit estimates the capacitor voltage based on the charging time and a formula of the capacitor voltage of the RC filter, calculates a theoretical value of the AD converter circuit for the estimated capacitor voltage based on a conversion specification of the AD converter circuit, and calculates the conversion error based on a difference between the actual measured value in response to the received capacitor voltage and the theoretical value for the estimated capacitor voltage.

2. The brushless motor drive device according to claim 1, wherein

the pulse output circuit sends to the RC filter the pulse signal the frequency of which changes per pulse;

and

the AD-conversion-error calculation unit calculates the conversion error based on the difference obtained when a predetermined cycle number of the clock pulse passes.

3. The brushless motor drive device according to claim 2, wherein

the pulse signal to be sent from the pulse output circuit to the RC filter has a high-level period equal to a pulse width in which the clock pulse is counted up to a count number whose value changes per pulse, and

the AD-conversion-error calculation unit calculates, from the high-level period of the pulse signal, the charging time during which the capacitor is charged.

4. The brushless motor drive device according to claim 3, wherein the AD-conversion-error calculation unit calculates a clock error rate from a cyclic period of a communication pulse signal received as a command from outside and a cyclic period of the clock pulse, and then calculates the charging time by correcting the charging time using the clock error rate.

5. The brushless motor drive device according to claim 1, further comprising:

a correction table configured to correct the output value of the AD converter circuit; and

a correction-table generation unit configured to generate the correction table, the correction-table generation unit generating the correction table using, as a correction value, the conversion error calculated by the AD-conversion-error calculation unit.

6. The brushless motor drive device according to claim 1, further comprising an AD-converter-circuit diagnosis unit configured to diagnose faults in the AD converter circuit, the AD-converter-circuit diagnosis unit diagnosing the AD converter circuit as faulty when the pulse signal to be applied to the RC filter is low and the output value of the AD converter circuit produced in response to an input of a capacitor voltage of the RC filter falls outside a predetermined range.

7. The brushless motor drive device according to claim 1, wherein the AD-conversion-error calculation unit determines that the AD converter circuit is faulty when the pulse signal to be applied to the RC filter is high and the conversion error calculated falls outside a predetermined range.

8. The brushless motor drive device according to claim 1, further comprising a current-detection-circuit diagnosis unit configured to diagnose faults in the current detection circuit, the current-detection-circuit diagnosis unit diagnosing the current detection circuit as faulty when the brushless motor is in a stopped state and the output value of the AD converter circuit produced in response to an input of an output value of the current detection circuit falls outside a predetermined range.

9. The brushless motor drive device according to claim 1, wherein:

the current detection circuit includes a first current detector configured to detect a first current value of a U-phase wire of the winding, a second current detector configured to detect a second current value of a V-phase wire of the winding and a third current detector configured to detect a third current value of a W-phase wire of the winding, and

the AD convertor circuit includes a first AD convertor that receives the capacitor voltage and the first current value, a second AD convertor that receives the capacitor voltage and the second current value and a third AD convertor that receives the capacitor voltage and the third current value.

10. The brushless motor drive device according to claim 1, wherein the theoretical value of the AD converter circuit Vca is calculated by using the following formula: