Patent US5041773A successfully refreshed from Google Patents.
US5041773A
Expired / Lapsed
US
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Drive circuit for stepping motor
Assignee: Citizen Holdings Co Ltd
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Filing: 1990-04-18
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Granted: 1991-08-20
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Expires: 2010-04-18
Abstract
Abstract A drive circuit for a stepping motor which seeks the read/write head of an FDD or the like to a predetermined track. The drive circuit includes a plurality of exciting coils for providing exciting fields to a rotor and supplies exciting currents in the forward or reverse direction by a predetermined combination to each of the exciting coils. A constant-current circuit is provided so as to cause the exciting current flowing on each exciting coil to have a constant value. The constant-current circuit includes a current mirror circuit with the slave branch connected to the exciting coils and the master branch contained in the constant-current circuit. The constant-current circuit further includes a constant-current source for supplying a constant current to the master branch of the current mirror circuit and a constant-current setting circuit for setting the constant current as desired. By making the currents flowing on the exciting coils uniform, the seeking positional accuracy of the read/write head is improved.
Inventors
- 👤 Shoji Takahashi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 08:39
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/02; G11B5/022; H; H02; H02P; H02P8/00; H02P8/12; G11B5/48; G11B5/54; G11B5/55; G11B5/5521; G11B5/5526
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
249 words
A drive circuit for a stepping motor comprising: a plurality of coils for providing exciting magnetic fields to said stepping motor; a drive control circuit for so controlling the rotation of a rotor as to have a predetermined stepping angle by supplying exciting currents to said exciting coils; and a constant-current circuit for so controlling said exciting currents supplied to the respective exciting coils as to have the same value, said constant-current circuit comprising: a first current mirror circuit comprising: a first transistor a base of which is connected to a base of a second transistor for exciting a forward current; and a first constant-current source for supplying a predetermined constant current to the first transistor; and a second current mirror circuit comprising: a third transistor a base of which is connected to a base of a fourth transistor for exciting a reverse current; a second constant-current source for supplying a predetermined constant current to the third transistor; and a constant-current setting circuit for setting the output currents of said first and second constant current sources; and an externally attached resistance connected to said constant-current setting circuit, a value of said output currents of said first and second constant current sources being adjusted in accordance with the value of said externally attached resistance; and a means for varying the resistance of said externally attached resistance; whereby said exciting current flowing in said respective exciting coils are set at the same value, thereby improving the accuracy of said stepping angle.
Claim 2
Dependent Claim
249 words
A drive circuit for a stepping motor comprising: a plurality of coils for providing exciting magnetic fields to said stepping motor; a drive control circuit for so controlling the rotation of a rotor as to have a predetermined stepping angle by supplying exciting currents to said exciting coils; and a constant-current circuit for so controlling said exciting currents supplied to the respective exciting coils as to have the same value, said constant-current circuit comprising: a first current mirror circuit comprising: a first transistor a base of which is connected to a base of a second transistor for exciting a forward current; and a first constant-current source for supplying a predetermined constant current to the first transistor; and a second current mirror circuit comprising: a third transistor a base of which is connected to a base of a fourth transistor for exciting a reverse current; a second constant-current source for supplying a predetermined constant current to the third transistor; and a constant-current setting circuit for setting the output currents of said first and second constant current sources; and an externally attached resistance connected to said constant-current setting circuit, a value of said output currents of said first and second constant current sources being adjusted in accordance with the value of said externally attached resistance; and a means for varying the resistance of said externally attached resistance; whereby said exciting current flowing in said respective exciting coils are set at the same value, thereby improving the accuracy of said stepping angle.
Claim 3
Dependent Claim
35 words
A drive circuit for a stepping motor according to claim 1, wherein the value of said externally attached resistance is varied to a different value in accordance with the lapse, of time of motor seeking.
Claim 4
Dependent Claim
41 words
A drive circuit for a stepping motor according to claim 2, wherein said externally attached resistance is divided into a resistance at the time of starting, a resistance at the time of settling and a resistance at the time of holding.
Claim 5
Dependent Claim
35 words
A drive circuit for a stepping motor according to claim 3, wherein said resistance at the time of starting is selected for a predetermined time in succession from the application of a first step pulse.
Claim 6
Dependent Claim
32 words
A drive circuit for a stepping motor according to claim 3, wherein said resistance selected at the time of seeking is set at a different value in accordance with the stepping, rate.
Claim 7
Dependent Claim
54 words
A drive circuit for a stepping motor according to claim 1, wherein a plurality of kinds of resistances are adopted as said externally attached resistance which is connected to said constant-current setting circuit; and said constant-current circuit is provided with a control circuit for switching said resistances by the application of a step pulse.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-08-19 | 1995-02-18 | 1995-08-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-08-19 | 1999-02-18 | 1999-08-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-08-19 | 2003-02-18 | 2003-08-20 | $7700.00 | Window Closed / Lapsed |