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US5666254A
Expired / Lapsed
US
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Voltage sensing overcurrent protection circuit
Assignee: Tyco International Ltd Bermuda
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Filing: 1995-11-29
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Granted: 1997-09-09
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Expires: 2015-11-29
Abstract
Abstract An overcurrent protection system which will give a rapid response to overcurrents which cause a reduction in the voltage across the load, e.g. a partial or complete short across the load, and is particularly suitable for protecting circuits against relatively small overcurrents, comprising: a circuit interruption element which, in the operating circuit, is connected in series between the electrical power supply and the electrical load, and which has (1) a closed state which permits the flow of a normal current, I NORMAL , through the circuit interruption element, and (2) an open state which permits the flow of at most a reduced current, substantially less than I NORMAL , through the circuit interruption element; a control element which, in the operating circuit, is connected in parallel with the load, and which has (1)(i) an on state, when the voltage across the control element is a normal voltage, V NORMAL , and (ii) is converted to an off state, when the voltage across the control element falls to a value V FAULT , or less, and (2) is functionally linked to the circuit interruption element so that when the control element is in the on state, the circuit interruption element is in the closed state, and when the control element is in the off state, the circuit interruption element is in the open state; and a bypass element which (1) is connected in parallel with the circuit interruption element, and (2) has (i) a start-up state such that, if the circuit interruption element is in the fault state and a current I NORMAL is passed through the bypass element, the voltage across the control element is greater than V FAULT , and (ii) a stopped state such that if the circuit interruption element is in the fault state as a result of the voltage across the control element having fallen to a value V FAULT or less, the current through the bypass element is such that the voltage across the control element remains at a value of V FAULT or less.
Inventors
- 👤 Brian Thomas
- 👤 Hugh Duffy
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 15:45
CPC Classifications
H; H02; H02H; H02H9/00; H02H9/001; H02H9/02; H02H9/026; H01; H01H; H01H33/00; H01H33/02; H01H33/04; H01H33/16; H01H33/161; H01H2033/163; H03; H03K; H03K17/00; H03K17/04; H03K17/041; H03K17/04106
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
335 words
An electrical system which can be connected between an electrical power supply and an electrical load to form an operating circuit, and which when so connected protects the circuit from overcurrents, which system comprises: a. a circuit interruption element which, in the operating circuit, is connected in series between the electrical power supply and the electrical load, and which has (1) a closed state which permits the flow of a normal current, I NORMAL , through the circuit interruption element, and (2) an open state which permits the flow of at most a reduced current, substantially less than I NORMAL , through the circuit interruption element; b. a control element which, in the operating circuit, is connected in parallel with the load, and which has (1) (i) an on state, when the voltage across the control element is a normal voltage, V NORMAL , and (ii) is converted to an off state, when the voltage across the control element falls to a value V VAULT , or less, and (2) is functionally linked to the circuit interruption element so that when the control element is in the on state, the circuit interruption element is in the closed state, and when the control element is in the off state, the circuit interruption element is in the open state; and c. a bypass element which (1) is connected in parallel with the circuit interruption element, and (2) has (i) a start-up state such that, if the circuit interruption element is in the open state and a current I NORMAL is passed through the bypass element, the voltage across the control element is greater than V FAULT , and (ii) a stopped state such that if the circuit interruption element is in the open state as a result of the voltage across the control element having fallen to a value V FAULT or less, the current through the bypass element is such that the voltage across the control element remains at a value of V FAULT or less.
Claim 2
Dependent Claim
335 words
An electrical system which can be connected between an electrical power supply and an electrical load to form an operating circuit, and which when so connected protects the circuit from overcurrents, which system comprises: a. a circuit interruption element which, in the operating circuit, is connected in series between the electrical power supply and the electrical load, and which has (1) a closed state which permits the flow of a normal current, I NORMAL , through the circuit interruption element, and (2) an open state which permits the flow of at most a reduced current, substantially less than I NORMAL , through the circuit interruption element; b. a control element which, in the operating circuit, is connected in parallel with the load, and which has (1) (i) an on state, when the voltage across the control element is a normal voltage, V NORMAL , and (ii) is converted to an off state, when the voltage across the control element falls to a value V VAULT , or less, and (2) is functionally linked to the circuit interruption element so that when the control element is in the on state, the circuit interruption element is in the closed state, and when the control element is in the off state, the circuit interruption element is in the open state; and c. a bypass element which (1) is connected in parallel with the circuit interruption element, and (2) has (i) a start-up state such that, if the circuit interruption element is in the open state and a current I NORMAL is passed through the bypass element, the voltage across the control element is greater than V FAULT , and (ii) a stopped state such that if the circuit interruption element is in the open state as a result of the voltage across the control element having fallen to a value V FAULT or less, the current through the bypass element is such that the voltage across the control element remains at a value of V FAULT or less.
Claim 3
Dependent Claim
89 words
A system according to claim 1, wherein a. the control element comprises a relay coil, which (1) is energized when the voltage across the relay coil is V NORMAL , and (2) is deenergized, when the voltage across the relay coil falls to a value V FAULT or less; and b. the circuit interruption element comprises a set of relay contacts which are coupled with the relay coil, and which (1) are closed when the relay coil is energized, and (2) are open when the relay coil is deenergized.
Claim 4
Dependent Claim
107 words
A system according to claim 1, wherein a. the circuit interruption element comprises a field effect transistor (FET), comprising a gate, a source, and a drain, which (1) will allow the normal circuit current, I NORMAL , to pass when the gate voltage of the FET is a normal gate voltage, and (2) will switch to permit the flow of at most a reduced current, substantially less than I NORMAL , when the gate voltage of the FET falls below the normal gate voltage by a predetermined gate voltage amount; and b. the control element comprises a voltage divider which determines the gate voltage of the FET.
Claim 5
Dependent Claim
14 words
A system according to claim 1 wherein the bypass element is a PTC device.
Claim 6
Dependent Claim
15 words
A system according to claim 4 wherein the bypass element is a polymeric PTC device.
Claim 7
Dependent Claim
109 words
A system according to claim 1 which comprises a second circuit interruption element which, in the operating circuit, is connected in series with the load, between the load and the control element, and which a. has (1) a closed state which permits the flow of a normal current, I NORMAL , through the load, and (2) an open state which permits the flow of at most a reduced current, substantially less than I NORMAL , through the load; and b. is in said closed state when the control element is in the on state, and is in said open state when the control element is in the off state.
Claim 8
Dependent Claim
318 words
An electrical circuit, comprising an electrical power supply, an electrical load, and an electrical protection system which protects the electrical circuit from overcurrents, which system comprises: a. circuit interruption element which is connected in series between the electrical power supply and the electrical load, and which has (1) a closed state which permits the flow of a normal current, I NORMAL , through the circuit interruption element, and (2) an open state which permits the flow of at most a reduced current, substantially less than I NORMAL , through the circuit interruption element; b. a control element which is connected in parallel with the load, and which has (1) (i) an on state, when the voltage across the control element is a normal voltage, V NORMAL , and (ii) is converted to an off state, when the voltage across the control element falls to a value V FAULT , or less, and (2) is functionally linked to the circuit interruption element so that when the control element is in the on state, the circuit interruption element is in the closed state, and when the control element is in the off state, the circuit interruption element is in the open state; and c. a bypass element which (1) is connected in parallel with the circuit interruption element, and (2) has (i) a start-up state such that, if the circuit interruption element is in the open state and a current I NORMAL is passed through the bypass element, the voltage across the control element is greater than V FAULT , and (ii) a stopped state such that if the circuit interruption element is in the open state as a result of the voltage across the control element having fallen to a value V FAULT or less, the current through the bypass element is such that the voltage across the control element remains at a value of V FAULT or less.
Claim 9
Dependent Claim
318 words
An electrical circuit, comprising an electrical power supply, an electrical load, and an electrical protection system which protects the electrical circuit from overcurrents, which system comprises: a. circuit interruption element which is connected in series between the electrical power supply and the electrical load, and which has (1) a closed state which permits the flow of a normal current, I NORMAL , through the circuit interruption element, and (2) an open state which permits the flow of at most a reduced current, substantially less than I NORMAL , through the circuit interruption element; b. a control element which is connected in parallel with the load, and which has (1) (i) an on state, when the voltage across the control element is a normal voltage, V NORMAL , and (ii) is converted to an off state, when the voltage across the control element falls to a value V FAULT , or less, and (2) is functionally linked to the circuit interruption element so that when the control element is in the on state, the circuit interruption element is in the closed state, and when the control element is in the off state, the circuit interruption element is in the open state; and c. a bypass element which (1) is connected in parallel with the circuit interruption element, and (2) has (i) a start-up state such that, if the circuit interruption element is in the open state and a current I NORMAL is passed through the bypass element, the voltage across the control element is greater than V FAULT , and (ii) a stopped state such that if the circuit interruption element is in the open state as a result of the voltage across the control element having fallen to a value V FAULT or less, the current through the bypass element is such that the voltage across the control element remains at a value of V FAULT or less.
Claim 10
Dependent Claim
89 words
A circuit according to claim 7, wherein a. the control element comprises a relay coil, which (1) is energized when the voltage across the relay coil is V NORMAL , and (2) is deenergized, when the voltage across the relay coil falls to a value V FAULT or less; and b. the circuit interruption element comprises a set of relay contacts which are coupled with the relay coil, and which (1) are closed when the relay coil is energized, and (2) are open when the relay coil is deenergized.
Claim 11
Dependent Claim
107 words
A circuit according to claim 7, wherein a. the circuit interruption element comprises a field effect transistor (FET), comprising a gate, a source, and a drain, which (1) will allow the normal circuit current, I NORMAL , to pass when the gate voltage of the FET is a normal gate voltage, and (2) will switch to permit the flow of at most a reduced current, substantially less than I NORMAL , when the gate voltage of the FET falls below the normal gate voltage by a predetermined gate voltage mount; and b. the control element comprises a voltage divider which determines the gate voltage of the FET.
Claim 12
Dependent Claim
14 words
A circuit according to claim 7 wherein the bypass element is a PTC device.
Claim 13
Dependent Claim
15 words
A circuit according to claim 10 wherein the bypass element is a polymeric PTC device.
Claim 14
Dependent Claim
105 words
A circuit according to claim 7 which comprises a second circuit interruption element which is connected in series with the load, between the load and the control element, and which a. has (1) a closed state which permits the flow of a normal current, I NORMAL , through the load, and (2) an open state which permits the flow of at most a reduced current, substantially less than I NORMAL , through the load; and b. is in said closed state when the control element is in the on state, and is in said open state when the control element is in the off state.
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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) | 2000-09-08 | 2001-03-10 | 2001-09-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2004-09-08 | 2005-03-10 | 2005-09-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2008-09-08 | 2009-03-10 | 2009-09-09 | $7700.00 | Window Closed / Lapsed |