Patent US3835367A successfully refreshed from Google Patents.
US3835367A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Overload protection circuits
Assignee: Lucas Electrical Co Ltd
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Filing: 1973-02-13
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Granted: 1974-09-10
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Expires: 1993-02-13
Abstract
Abstract An overload protection circuit has a thyristor the anode and cathode of which are connected across a pair of supply lines requiring protection. Connected across the anode-cathode is a series circuit including a voltage dependent resistance and a resistor, the junction of which is connected to the gate of the thyristor. At the nominal voltage of the system, the voltage dependent resistance has a high value, but it has a substantially reduced value at voltages substantially above the nominal voltage of the system. The voltage dependent resistance protects the system against low current volts, and the thyristor is turned on for high current volts.
Inventors
- 👤 D Wiley
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 06:07
CPC Classifications
H; H02; H02H; H02H9/00; H02H9/04; H02H9/041; H02H7/00; H02H7/06; H02H7/067; Y; Y10; Y10S; Y10S320/00; Y10S320/13
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
200 words
A battery charging system for a road vehicle, comprising in combination a generator having a field winding, a battery which in use is charged by the generator, a semi-conductor voltage regulator for regulating the output of the generator by varying the current flow through the field winding, and a protection circuit for preventing destruction of the regulator by transients in the system, said protection circuit comprising in combination a thyristor having its anode-cathode path connected across the regulator, and a series circuit connected across the regulator and including a voltage-dependent resistance and a resistor, the voltage-dependent resistance having a high value at the nominal system voltage but a substantially reduced value when the voltage across the regulator rises above a predetermined value, the junction of the voltage dependent resistance and the resistor being connected to the gate of the thyristor, and wherein the voltage developed across said resistor in series with said voltage-dependent resistance, when the voltage across the regulator rises above said predetermined value, is insufficient to turn on said thyristor during the occurrence of a low current transient across the regulator, the voltage developed during a high current transient effecting conduction of said thyristor to protect the regulator.
Claim 2
Dependent Claim
200 words
A battery charging system for a road vehicle, comprising in combination a generator having a field winding, a battery which in use is charged by the generator, a semi-conductor voltage regulator for regulating the output of the generator by varying the current flow through the field winding, and a protection circuit for preventing destruction of the regulator by transients in the system, said protection circuit comprising in combination a thyristor having its anode-cathode path connected across the regulator, and a series circuit connected across the regulator and including a voltage-dependent resistance and a resistor, the voltage-dependent resistance having a high value at the nominal system voltage but a substantially reduced value when the voltage across the regulator rises above a predetermined value, the junction of the voltage dependent resistance and the resistor being connected to the gate of the thyristor, and wherein the voltage developed across said resistor in series with said voltage-dependent resistance, when the voltage across the regulator rises above said predetermined value, is insufficient to turn on said thyristor during the occurrence of a low current transient across the regulator, the voltage developed during a high current transient effecting conduction of said thyristor to protect the regulator.
Claim 3
Dependent Claim
40 words
A system as claimed in claim 1 in which the resistor is bridged by a Zener diode and a further resistor in series, the junction of the Zener diode and further resistor being connected to the gate of the thyristor.
Claim 4
Dependent Claim
43 words
A system as claimed in claim 1 in which the voltage-dependent resistor is a Zener diode, the voltage developed across said resistor in series with the Zener diode at the instant when the Zener diode conducts being insufficient to turn on said thyristor.
Claim 5
Dependent Claim
22 words
A system as claimed in claim 3 in which the resistor in series with the voltage-dependent resistor has a very low inductance.
Claim 6
Dependent Claim
22 words
A system as claimed in claim 4 in which the resistor in series with the voltage-dependent resistor is a printed circuit resistor.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-09-09 | 1978-03-11 | 1978-09-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-09-09 | 1982-03-11 | 1982-09-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-09-09 | 1986-03-11 | 1986-09-10 | $7700.00 | Window Closed / Lapsed |