US3781608A
Expired / Lapsed
US
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Fast acting circuitry for dc overload protection
Assignee: Loewe Opta GmbH
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Filing: 1972-09-07
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Granted: 1973-12-25
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Expires: 1992-09-07
Abstract
Abstract An improved overload protection circuit is associated with a DC load having a first output whose voltage level exhibits a significant decrease in the presence of a short circuit in the load. A thyristor connected in series with a rectifier and a relatively large filter capacitor in the load power supply is normally maintained conductive by coupling its control electrode to the normally high voltage at the first output of the load, such high voltage being stored across a relatively small capacitor in the coupling circuit. When the load is shorted, the small capacitor discharges rapidly to decrease the voltage at the control electrode of the thyristor below its conductive threshhold, whereby the thyristor shuts off at the conclusion of the then-current input AC half cycle. A high-resistance bypass for the thyristor defines an auxiliary current path during thyristor shut-down so that upon correction of the short circuit, the filter capacitor (and therefore the small capacitor in the coupling circuit) recharges to turn on the thyristor and thereby restore operating load current.
Inventors
- 👤 E Geiger
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 20:45
CPC Classifications
H; H02; H02H; H02H3/00; H02H3/08; H02H3/087; H02H3/02; H02H3/06; H02H3/066; H02H3/24; H03; H03K; H03K17/00; H03K17/08; H03K17/082; H03K17/0824
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
203 words
In combination with (i) a power supply including a low-pass filter serially connectable across an AC source and (ii) a load coupled to the filter for extracting DC current from the power supply, the load having a first output whose voltage level is higher when the load exhibits a first normal condition than when the load exhibits a second abnormal condition, an arrangement for reducing the load current when the load exhibits the second condition and for restoring the load current when the load again exhibits the first condition, which comprises: a normally nonconductive gate having a transconductive path and a control electrode, the gate being conditioned for conduction upon the application to the control electrode of a voltage level above a predetermined threshhold; a first path serially connected with the filter and including the transconductive path of the gate; a second path connected across the first path and having a significantly higher DC resistance than the first path when the gate is conductive; and means responsive to the voltage level at the first output of the load for applying, to the control electrode of the gate, a voltage amplitude thAt exceeds the predetermined threshhold only when the load exhibits the first condition.
Claim 2
Dependent Claim
203 words
In combination with (i) a power supply including a low-pass filter serially connectable across an AC source and (ii) a load coupled to the filter for extracting DC current from the power supply, the load having a first output whose voltage level is higher when the load exhibits a first normal condition than when the load exhibits a second abnormal condition, an arrangement for reducing the load current when the load exhibits the second condition and for restoring the load current when the load again exhibits the first condition, which comprises: a normally nonconductive gate having a transconductive path and a control electrode, the gate being conditioned for conduction upon the application to the control electrode of a voltage level above a predetermined threshhold; a first path serially connected with the filter and including the transconductive path of the gate; a second path connected across the first path and having a significantly higher DC resistance than the first path when the gate is conductive; and means responsive to the voltage level at the first output of the load for applying, to the control electrode of the gate, a voltage amplitude thAt exceeds the predetermined threshhold only when the load exhibits the first condition.
Claim 3
Dependent Claim
257 words
In combination with (i) a power supply including a low-pass filter serially connectable across an AC source and (ii) a load coupled to the filter for extracting current from the power supply, the load having a first output whose voltage level is higher when the load exhibits a first normal condition than when the load exhibits a second abnormal condition, an arrangement for reducing the load current when the load exhibits the second condition and for restoring the load current when the load again exhibits the first condition, which comprises: a normally nonconductive gate having a transconductive path and a control electrode, the gate being conditioned for conduction upon the application of the control electrode of a voltage level above a predetermined threshold; a first path serially connected with the filter and including the transconductive path of the gate; a second path connected across the first path and having a significantly higher ressistance than the first path when the gate is conductive, the second path including a normally disabled controllable switch; first means responsive to the voltage level at the first output of the load for applying, to the control electrode of the gate, a voltage amplitude that exceeds the predetermined threshold when the load exhibits the first condition; second means responsive to the voltage at the first output of the load for enabling the switch when the load exhibits the second condition; and means for coupling the switch to the control electrode of the gate to effectively shunt said control electrode when the switch is enabled.
Claim 4
Dependent Claim
257 words
In combination with (i) a power supply including a low-pass filter serially connectable across an AC source and (ii) a load coupled to the filter for extracting current from the power supply, the load having a first output whose voltage level is higher when the load exhibits a first normal condition than when the load exhibits a second abnormal condition, an arrangement for reducing the load current when the load exhibits the second condition and for restoring the load current when the load again exhibits the first condition, which comprises: a normally nonconductive gate having a transconductive path and a control electrode, the gate being conditioned for conduction upon the application of the control electrode of a voltage level above a predetermined threshold; a first path serially connected with the filter and including the transconductive path of the gate; a second path connected across the first path and having a significantly higher ressistance than the first path when the gate is conductive, the second path including a normally disabled controllable switch; first means responsive to the voltage level at the first output of the load for applying, to the control electrode of the gate, a voltage amplitude that exceeds the predetermined threshold when the load exhibits the first condition; second means responsive to the voltage at the first output of the load for enabling the switch when the load exhibits the second condition; and means for coupling the switch to the control electrode of the gate to effectively shunt said control electrode when the switch is enabled.
Claim 5
Dependent Claim
258 words
In combination with (i) a power supply including a low-pass filter serially connectable across an AC source and (ii) a load coupled to the filter for extracting current from the power supply, the load having a first output whose voltage level is higher when the load exhibits a first normal condition than when the load exhibits a second abnormal condition, an arrangement for reducing the load current when the load exhibits the second condition and for restoring the load current when the load again exhibits the first condition, which comprises: a normally nonconductive thyristor having a transconductive path and a control electrode, the thyristor being conditioned for conduction upon the application to the control electrode of a voltage level above a predetermined threshhold; a first path serially connected with the filter and including the transconductive path of the thyristor; a second path connected across the first path and including a normally disabled switch, the second path having a significantly higher resistance than the first path when the thyristor is conductive; means responsive to the voltage level at the first output of the load for applying, to the control electrode of the thyristor, a voltage amplitude that exceeds the predetermined threshhold of the thyristor when the load exhibits the first condition; means for coupling the switch to the control electrode of the thyristor to effectively shunt said control electrode when the switch is enabled; and means responsive to the voltage level at the first output of the load for enabling the switch when the load exhibits its second condition.
Claim 6
Dependent Claim
258 words
In combination with (i) a power supply including a low-pass filter serially connectable across an AC source and (ii) a load coupled to the filter for extracting current from the power supply, the load having a first output whose voltage level is higher when the load exhibits a first normal condition than when the load exhibits a second abnormal condition, an arrangement for reducing the load current when the load exhibits the second condition and for restoring the load current when the load again exhibits the first condition, which comprises: a normally nonconductive thyristor having a transconductive path and a control electrode, the thyristor being conditioned for conduction upon the application to the control electrode of a voltage level above a predetermined threshhold; a first path serially connected with the filter and including the transconductive path of the thyristor; a second path connected across the first path and including a normally disabled switch, the second path having a significantly higher resistance than the first path when the thyristor is conductive; means responsive to the voltage level at the first output of the load for applying, to the control electrode of the thyristor, a voltage amplitude that exceeds the predetermined threshhold of the thyristor when the load exhibits the first condition; means for coupling the switch to the control electrode of the thyristor to effectively shunt said control electrode when the switch is enabled; and means responsive to the voltage level at the first output of the load for enabling the switch when the load exhibits its second condition.
Claim 7
Dependent Claim
27 words
An arrangement as defined in claim 3, in which the filter comprises a relatively large capacitor, and in which the applying means comprises a relatively small capacitor.
Claim 8
Dependent Claim
285 words
In combination with (i) a power supply including a low-pass filter serially connectable across an AC source and (ii) a load coupled to the filter for extracting current from the power supply, the load having a first output whose voltage level is higher when the load exhibits a first normal condition than when the load exhibits a second abnormal condition, an arrangement for reducing the load current when the load exhibits the second condition and for restoring the load cuRrent when the load again exhibits the first condition, which comprises: a normally nonconductive gate having a transconductive path and a control electrode, the gate being conditioned for conduction upon the application to the control electrode of a voltage level above a predetermined threshhold; a first path serially connected with the filter and including the transconductive path of the gate; first and second transistors; means for conductively connecting the emitters of the first and second transistors; a second path connected acrossthe first path and including the collector-emitter path of the first transistor, the second path having a significantly higher resistance than the first path when the gate is conductive; a third path connected across the second path and including the collector-emitter path of the second transistor; a voltage divider; first means for coupling the input of the voltage divider to the first output of the load; second means for coupling the input of the voltage divider to the collector of the first transistor and to the control electrode of the gate; third means for coupling the output of the voltage divider to the base of the second transistor; and fourth means for coupling the collector of the second transistor to the base of the first transistor.
Claim 9
Dependent Claim
285 words
In combination with (i) a power supply including a low-pass filter serially connectable across an AC source and (ii) a load coupled to the filter for extracting current from the power supply, the load having a first output whose voltage level is higher when the load exhibits a first normal condition than when the load exhibits a second abnormal condition, an arrangement for reducing the load current when the load exhibits the second condition and for restoring the load cuRrent when the load again exhibits the first condition, which comprises: a normally nonconductive gate having a transconductive path and a control electrode, the gate being conditioned for conduction upon the application to the control electrode of a voltage level above a predetermined threshhold; a first path serially connected with the filter and including the transconductive path of the gate; first and second transistors; means for conductively connecting the emitters of the first and second transistors; a second path connected acrossthe first path and including the collector-emitter path of the first transistor, the second path having a significantly higher resistance than the first path when the gate is conductive; a third path connected across the second path and including the collector-emitter path of the second transistor; a voltage divider; first means for coupling the input of the voltage divider to the first output of the load; second means for coupling the input of the voltage divider to the collector of the first transistor and to the control electrode of the gate; third means for coupling the output of the voltage divider to the base of the second transistor; and fourth means for coupling the collector of the second transistor to the base of the first transistor.
Claim 10
Dependent Claim
14 words
An arrangement as defined in claim 5, in which the gate is a thyristor.
Claim 11
Dependent Claim
28 words
An arrangement as defined in claim 5, in which the filter comprises a relatively large capacitor, and in which the first coupling means comprises a relatively small capacitor.
Claim 12
Dependent Claim
30 words
An arrangement as defined in claim 5, in which the second coupling means comprises means for isolating the base of the second transistor from the collector of the first transistor.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-12-24 | 1977-06-25 | 1977-12-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-12-24 | 1981-06-25 | 1981-12-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-12-24 | 1985-06-25 | 1985-12-25 | $7700.00 | Window Closed / Lapsed |