Drive circuit of stepping motor, integrated circuit thereof, and electronic equipment including same, and method for controlling drive circuit of stepping motor

Patent metadata

Field	Value
Publication number	US-9654040-B2
Application number	US-201213981391-A
Country	US
Kind code	B2
Filing date	Jan 23, 2012
Priority date	Jan 25, 2011
Publication date	May 16, 2017
Grant date	May 16, 2017

Abstract

A drive circuit of a stepping motor includes a D/A converter, a current controller having a comparing unit, and an abnormality detecting unit. The DAC generates a target voltage indicating a target value for an excitation current determined based on a reference voltage indicating an upper limit value of the excitation current flowing into the stepping motor. The current controller controls the excitation current based on this target voltage. The comparing unit compares a voltage corresponding to the excitation current and the target voltage. The abnormality detecting unit detects an abnormality of the wire between the drive circuit and the stepping motor based on an output signal from the comparing unit and a control signal indicating a polarity of the excitation current.

First claim

The invention claimed is:

1. A drive circuit of a stepping motor comprising:
a drive unit configured to switch a level of an excitation current to the stepping motor based on an phase signal;
a target voltage generating unit configured to generate a target voltage for determining a target value of the excitation current, when the excitation current flowing into the stepping motor is maintained at the same level;
a current controller configured to control the excitation current so as to maintain a value of the excitation current at the target value based on the target voltage;
an oscillation circuit configured to generate an oscillation signal which has an oscillation cycle shorter than a switching cycle of the level of the excitation current;
a logic controller configured to turn the drive unit on and off based on the oscillation signal and an output reversal of a comparing unit within a first period in which the excitation current flowing into the stepping motor is to be maintained at the same level, the comparing unit being configured to reverse its output based on a comparison between a signal varying in accordance with turning the drive unit on and off by the logic controller and the target voltage; and
an abnormality detecting unit configured to detect a state, where the output reversal of the comparing unit does not occur within a predetermined period that is shorter than the first period, as an abnormal state.

2. The drive circuit of a stepping motor according to claim 1 , wherein the abnormality detecting unit is configured to detect the abnormality state when the output reversal does not occur more than a prescribed times.

3. The drive circuit of a stepping motor according to claim 2 , wherein the abnormality detecting unit is configured to detect that the abnormality occurs when the number of times of the output reversal is less than a predetermined reference number.

4. The drive circuit of a stepping motor according to claim 1 , wherein the abnormality detecting unit determines the abnormality state in response to successive detections of the abnormality state for a predetermined times.

5. The drive circuit of a stepping motor according to claim 1 , wherein the target voltage generating unit generates the target voltage by dividing an upper limit value of the target value in accordance with a ratio changing in a stepwise manner from 0 to 1, the upper limit value being 1.

6. The drive circuit of a stepping motor according to claim 5 , further comprising an instruction generating unit configured to generate a signal indicating the ratio based on information from outside of the drive circuit.

7. A method for controlling a drive circuit of a stepping motor, the method comprising:
switching a level of an excitation current to the stepping motor based on an phase signal by a drive unit;
generating a target voltage for determining a target value of the excitation current, when the excitation current flowing into the stepping motor is maintained at the same level;
controlling the excitation current so as to maintain a value of the excitation current at the target value based on the target voltage;
generating an oscillation signal which has an oscillation cycle shorter than a switching cycle of the level of the excitation current;
turning the drive unit on and off based on the oscillation signal and an output reversal of a comparing unit within a first period during which the excitation current flowing into the stepping motor is to be maintained at the same level;
reversing an output of the comparing unit based on a comparison between a signal varying in accordance with turning the drive unit on and off and the target voltage; and
detecting a state, where the output reversal does not occur within a predetermined period shorter than the first period, as an abnormal state.

Assignees

• Tsuchihashi Masanori
• Hashimoto Hiroki
• Rohm Co Ltd

Inventors

• Tsuchihashi Masanori
• Hashimoto Hiroki

Classifications

• H02P8/34 Primary

  Monitoring operation (H02P8/36 takes precedence) · CPC title

• H02P8/36

  Protection against faults, e.g. against overheating or step-out; Indicating faults · CPC title

• B41J19/202

  Drive control means for carriage movement · CPC title

• H02P8/38 Primary

  the fault being step-out · CPC title