US3846674A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Overcurrent protection circuit including a heat sensitive element and a thyristor
Assignee: RCA Corp
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Filing: 1972-08-23
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Granted: 1974-11-05
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Expires: 1992-08-23
Abstract
Abstract A heat dissipating element is connected in circuit with a load, the current passing through the element being representative of the current supplied to the load. A thermistor is placed in physical proximity with the heat dissipating element and electrically connected in circuit with the control electrode of a thyristor, the conduction state of the thyristor determining the presence or absence of current to the load; the resistance of the thermistor determining the conduction state of the thyristor.
Inventors
- 👤 T Mcnulty
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 03:40
CPC Classifications
H; H02; H02H; H02H3/00; H02H3/08; H02H3/085
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
141 words
An overload protection circuit adapted to sense overload conditions of a load and discontinue the supply of power thereto as a result thereof, comprising: heat dissipating means adapted for connection to said load, the amount of heat dissipated by said means being proportionate to the current through said load; a thyristor having first and second main terminal electrodes and a control electrode, said main terminal electrodes adapted for connection in series circuit with said load; a time constant circuit comprising the serial combination of a resistor and a capacitor, said serial combination being connected across said first and second main terminal electrodes; means for connecting the point between said resistor and said capacitor to said control electrode; and a negative temperature coefficient thermistor connected in parallel circuit with said capacitor, said thermistor disposed in physical proximity with said heat dissipating means.
Claim 2
Dependent Claim
141 words
An overload protection circuit adapted to sense overload conditions of a load and discontinue the supply of power thereto as a result thereof, comprising: heat dissipating means adapted for connection to said load, the amount of heat dissipated by said means being proportionate to the current through said load; a thyristor having first and second main terminal electrodes and a control electrode, said main terminal electrodes adapted for connection in series circuit with said load; a time constant circuit comprising the serial combination of a resistor and a capacitor, said serial combination being connected across said first and second main terminal electrodes; means for connecting the point between said resistor and said capacitor to said control electrode; and a negative temperature coefficient thermistor connected in parallel circuit with said capacitor, said thermistor disposed in physical proximity with said heat dissipating means.
Claim 3
Dependent Claim
26 words
The circuit according to claim 1 wherein said means for connecting the point between said resistor and said capacitor to said control electrode comprises a diac.
Claim 4
Dependent Claim
147 words
An overload protection circuit adapted to sense overload conditions in a load and discontinue the supply of power thereto as a result thereof, comprising: heat dissipating means connectable in series with said load, the amount of heat dissipated by said means being proportionate to the current through said load; a thyristor having first and second main terminal electrodes and a control electrode; a current limiting impedance adapted for connection in series circuit with main terminal electrodes, said impedance and said thyristor being connectable in parallel circuit across said heat dissipating means and said load; and a heat sensitive resistor connected between the control electrode and one main electrode, said resistor being in physical proximity to said heat dissipating means, the resistance of said heat sensitive resistor decreasing to a value sufficient to render said thyristor conductive when the current through said load increases to a predetermined value.
Claim 5
Dependent Claim
147 words
An overload protection circuit adapted to sense overload conditions in a load and discontinue the supply of power thereto as a result thereof, comprising: heat dissipating means connectable in series with said load, the amount of heat dissipated by said means being proportionate to the current through said load; a thyristor having first and second main terminal electrodes and a control electrode; a current limiting impedance adapted for connection in series circuit with main terminal electrodes, said impedance and said thyristor being connectable in parallel circuit across said heat dissipating means and said load; and a heat sensitive resistor connected between the control electrode and one main electrode, said resistor being in physical proximity to said heat dissipating means, the resistance of said heat sensitive resistor decreasing to a value sufficient to render said thyristor conductive when the current through said load increases to a predetermined value.
Claim 6
Dependent Claim
19 words
The circuit according to claim 1 wherein said heat dissipating means is connected in series circuit with said load.
References Cited (Backward Citations)
US3211955A
Cited
US3562587A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-11-04 | 1978-05-06 | 1978-11-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-11-04 | 1982-05-06 | 1982-11-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-11-04 | 1986-05-06 | 1986-11-05 | $7700.00 | Window Closed / Lapsed |