Patent US3909675A successfully refreshed from Google Patents.
US3909675A
Expired / Lapsed
US
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Protection circuit
Assignee: Texas Instruments Inc
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Filing: 1972-12-13
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Granted: 1975-09-30
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Expires: 1992-12-13
Abstract
Abstract The disclosure relates to a motor protection circuit utilizing PTC sensors and all solid state circuitry to provide protection to a motor circuit and the like. The protection circuit is capable of providing protection for a plurality of devices simultaneously. The sensor circuits can be connected either serially or in parallel and provide equivalent results.
Inventors
- 👤 Hans G Hirsbrunner
- 👤 Leo A Plouffe
- 👤 Jr Lyle E Mcbride
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 12:17
CPC Classifications
H; H02; H02H; H02H5/00; H02H5/04; H02H5/042
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
134 words
A protection circuit for a device to be protected, which comprises: a. a switch and a source of power, b. a bridge circuit means controlling operation of said switch said bridge circuit including a resistor bridge, c. said bridge circuit means including a PTC temperature sensor means responsive to a predetermined alarm condition, d. means responsive to said predetermined alarm condition for providing a reset condition different from both said alarm condition and the normal operating condition, said means responsive to said predetermined alarm condition includes resistance means coupled in parallel with another of the legs of said bridge whereby said sensor and the parallel combination of said another of the legs with said resistance means forms a voltage divider, e. and trigger means responsive to unbalance of said bridge to operate said switch.
Claim 2
Dependent Claim
134 words
A protection circuit for a device to be protected, which comprises: a. a switch and a source of power, b. a bridge circuit means controlling operation of said switch said bridge circuit including a resistor bridge, c. said bridge circuit means including a PTC temperature sensor means responsive to a predetermined alarm condition, d. means responsive to said predetermined alarm condition for providing a reset condition different from both said alarm condition and the normal operating condition, said means responsive to said predetermined alarm condition includes resistance means coupled in parallel with another of the legs of said bridge whereby said sensor and the parallel combination of said another of the legs with said resistance means forms a voltage divider, e. and trigger means responsive to unbalance of said bridge to operate said switch.
Claim 3
Dependent Claim
28 words
A protection circuit as set forth in claim 1 wherein said trigger means is controlled by the voltage at the junction of said sensor and said parallel combination.
Claim 4
Dependent Claim
21 words
A protection circuit as set forth in claim 2 wherein said sensor includes a plurality of PTC devices connected in series.
Claim 5
Dependent Claim
30 words
A protection circuit as set forth in claim 2 wherein said sensor includes a plurality of PTC devices connected in parallel and an OR gate coupled to said PTC devices.
Claim 6
Dependent Claim
21 words
A protection circuit as set forth in claim 1 wherein said sensor includes a plurality of PTC devices connected in series.
Claim 7
Dependent Claim
30 words
A protection circuit as set forth in claim 1 wherein said sensor includes a plurality of PTC devices connected in parallel and an OR gate coupled to said PTC devices.
Claim 8
Dependent Claim
46 words
A protection circuit for a device to be prOtected as set forth in claim 1 wherein said means responsive to said predetermined alarm condition for providing a reset condition different from both said alarm condition and the normal operating condition includes a normally reverse biased diode.
Claim 9
Dependent Claim
73 words
A protection circuit for a device to be protected as set forth in claim 1 wherein said switch is a triac having two anodes in series with said source of power and a gate serially connected to said means responsive to said predetermined alarm condition, said means responsive to said predetermined alarm condition comprises a modified Schmitt trigger having a PNP transistor, said gate being serially connected to the emitter of said transistor.
References Cited (Backward Citations)
US3320407A
Cited
US3329869A
Cited
US3366843A
Cited
US3417305A
Cited
US3404313A
Cited
US3500074A
Cited
US3457460A
Cited
US3614392A
Cited
US3597590A
Cited
US3555356A
Cited
US3546435A
Cited
US3593062A
Cited
US3751635A
Cited
US3740613A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-09-29 | 1979-03-31 | 1979-09-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-09-29 | 1983-03-31 | 1983-09-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-09-29 | 1987-03-31 | 1987-09-30 | $7700.00 | Window Closed / Lapsed |