Driving circuit and driving method of stepping motor and electronic machine using the same

Patent metadata

Field	Value
Publication number	US-11245347-B2
Application number	US-202016798641-A
Country	US
Kind code	B2
Filing date	Feb 24, 2020
Priority date	Feb 26, 2019
Publication date	Feb 8, 2022
Grant date	Feb 8, 2022

Abstract

The present invention relates to a driving circuit and a driving method for a stepping motor, and an electronic machine using the same. A current value setting circuit generates a current setting value. A constant current chopper circuit generates a pulse modulation signal, which pulse-width modulates by having a detection value of a coil current flowing through a coil approach close to the current setting value. A logic circuit controls a bridge circuit connected to the coil of the stepping motor according to the pulse modulation signal. The current value setting circuit sets the current setting value to a predetermined full-torque setting value in a first period after rotation starts, reduces the current setting value to a predetermined second setting value less than the first setting value in the following second period, and switches to a high-efficiency mode and adjusts the current setting value by means of feedback control.

First claim

What is claimed is:

1. A driving circuit that is the driving circuit of a stepping motor, comprising:
a current value setting circuit, adapted to generate a current setting value;
a constant current chopper circuit, adapted to generate a pulse modulation signal, wherein the pulse modulation signal pulse modulates a detection value of a coil current flowing in a coil to be close to a target value, wherein the target value is based on the current setting value; and
a logic circuit, adapted to control a bridge circuit connected to a coil of the stepping motor according to the pulse modulation signal,
wherein the bridge circuit is adapted to,
in a first period after a rotation of the stepping motor starts, set the current setting value to be a predetermined first setting value,
in a second period after the first period, lower the current setting value to a predetermined second setting value that is smaller than the predetermined first setting value according to a predetermined pattern, and
in a third period after the second period, modify the current setting value by a feedback control such that the stepping motor is operated in a high efficiency mode,

wherein the current value setting circuit is adapted to generate the current setting value in the first period and the second period by a feedforward control, and generate the current setting value having a convergence value in the high efficiency mode.

2. The driving circuit according to claim 1 , wherein, the current value setting circuit changes the current setting value in N steps from the first setting value to the second setting value in the second period, where N is more than or equal to 2.

3. The driving circuit according to claim 2 , wherein the current value setting circuit comprises:
a calculation portion, generating at least one intermediate value acquired by internally dividing the first setting value and the second setting value;
a multiplexer, receiving the first setting value, the second setting value and at least one of the setting value, and selecting one of the setting value corresponding to a control data; and
a waveform controller, changing the control data along with the time in the second period.

4. The driving circuit according to claim 2 , wherein the widths of the steps are equal.

5. The driving circuit according to claim 1 , wherein the current value setting circuit comprises:
a calculation portion, generating at least one intermediate value acquired by internally dividing the first setting value and the second setting value;
a multiplexer, receiving the first setting value, the second setting value and at least one of the setting value, and selecting one of the setting value corresponding to a control data; and
a waveform controller, changing the control data along with the time in the second period.

6. The driving circuit according to claim 1 , wherein the logic circuit generates a mask signal according to period of an input clock, wherein the mask signal regulates triggering of the transition from the first period to the second period.

7. The driving circuit according to claim 1 , further comprising a counter-electromotive force (EMF) detection circuit, detecting a counter-EMF generated by the coil, wherein the current value setting circuit performs feedback control on the current setting value according to the counter-EMF in the high-efficiency mode.

8. The driving circuit according to claim 7 , wherein the current value setting circuit further comprises:
a load angle estimating portion, estimating a load angle according to the counter-EMF; and
a feedback controller, generating the current setting value by having the estimated load angle approach to a predetermined target angle.

9. The driving circuit according to claim 1 , wherein the driving circuit is integrated on a semiconductor substrate.

10. An electronic machine, comprising a stepping motor; and driving the stepping motor by the driving circuit of claim 1 .

11. A driving method that is the driving method for a stepping motor, comprising:
in a first period after a rotation of the stepping motor starts, setting a current setting value to a predetermined first setting value by a feedforward control;
in a second period after the first period, lowering, by the feedforward control, the current setting value to a predetermined second setting value that is smaller than the predetermined first setting value according to a predetermined pattern;
in a third period after the second period, modifying the current setting value by a feedback control to have a convergence value such that the stepping motor is operated in a high efficiency mode;
generating a pulse modulation signal, wherein the pulse modulation signal pulse modulates a detection value of a coil current flowing in a coil to be close to a target value, wherein the target value is based on the current setting value; and
controlling a bridge circuit connected to a coil of the stepping motor according to the pulse modulation signal.

Assignees

• Rohm Co Ltd

Inventors

• Tsuchihashi Masanori
• Okada Mitsuo
• Kobayashi Ryota

Classifications

• H02P8/22 Primary

  Control of step size; Intermediate stepping, e.g. microstepping · CPC title

• H02P8/12 Primary

  Control or stabilisation of current · CPC title

• H02P8/18

  Shaping of pulses, e.g. to reduce torque ripple {(Reducing overshoot H02P8/32 takes precedence)} · CPC title

• H02P8/10

  Shaping pulses for starting; Boosting current during starting · CPC title

• H02P6/182

  using back-emf in windings · CPC title