US4585905A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Overvoltage protection circuit for SLIC
Assignee: Motorola Solutions Inc
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Filing: 1983-08-15
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Granted: 1986-04-29
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Expires: 2003-08-15
Abstract
Abstract A high impedance open circuit type of overvoltage protection circuit useful in conjunction with a SLIC is provided. Diodes are used to prevent current flow back into the SLIC. In addition, voltage-sensitive clamps are provided to clamp the SLIC current source and SLIC current sink into nonconductive states in the presence of an overvoltage condition.
Inventors
- 👤 Leland T. Brown
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 20:20
CPC Classifications
H; H02; H02H; H02H9/00; H02H9/04; H04; H04M; H04M19/00; H04M19/001; H04M19/005; H04M3/00; H04M3/18
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
128 words
An overvoltage protection circuit for a subscriber loop interface circuit (SLIC) having a Tip and a Ring terminal, the overvoltage protection circuit comprising: a current source; a first unidirectional current means coupled between the current source and the Tip terminal; a first voltage sensor coupled to the Tip terminal; first clamp means coupled to the first voltage sensor and to the current source for disabling the current source upon the first voltage sensor sensing a predetermined voltage; a current sink coupled to the Ring terminal; a second unidirectional current means coupled between the current sink and the Ring terminal; a second voltage sensor coupled to the Ring terminal; and second clamp means coupled to the second voltage sensor and the current sink to controllably inhibit the current sink.
Claim 2
Dependent Claim
128 words
An overvoltage protection circuit for a subscriber loop interface circuit (SLIC) having a Tip and a Ring terminal, the overvoltage protection circuit comprising: a current source; a first unidirectional current means coupled between the current source and the Tip terminal; a first voltage sensor coupled to the Tip terminal; first clamp means coupled to the first voltage sensor and to the current source for disabling the current source upon the first voltage sensor sensing a predetermined voltage; a current sink coupled to the Ring terminal; a second unidirectional current means coupled between the current sink and the Ring terminal; a second voltage sensor coupled to the Ring terminal; and second clamp means coupled to the second voltage sensor and the current sink to controllably inhibit the current sink.
Claim 3
Dependent Claim
24 words
The overvoltage protection circuit of claim 1 further including a clamp driver means coupled between the second voltage sensor and the second clamp means.
Claim 4
Dependent Claim
28 words
The overvoltage protection circuit of claim 1 wherein the current source and the current sink are each a pair of high voltage transistors connected in a Darlington configuration.
Claim 5
Dependent Claim
57 words
The overvoltage protection circuit of claim 3 wherein the first and second unidirectional current means are each a diode wherein the first unidirectional current means has its cathode connected to the Tip terminal and the second unidirectional current means has its anode connected to the Ring terminal; and wherein the first and second voltage sensors are resistors.
Claim 6
Dependent Claim
18 words
The voltage protection circuit of claim 3 wherein the first and second clamp means each include a transistor.
Claim 7
Independent Claim
93 words
A method for protecting a two-wire port of a SLIC from an overvoltage surge, comprising: blocking the overvoltage surge of a first polarity from entering a current source port of the SLIC; sensing voltage at the current source port of the SLIC and inhibiting the current source upon sensing a predetermined overvoltage of a second polarity at the current source port; blocking current flow caused by an overvoltage of the second polarity from a current sink port; and inhibiting the current sink port upon sensing a predetermined overvoltage surge of the first polarity.
Claim 8
Independent Claim
93 words
A method for protecting a two-wire port of a SLIC from an overvoltage surge, comprising: blocking the overvoltage surge of a first polarity from entering a current source port of the SLIC; sensing voltage at the current source port of the SLIC and inhibiting the current source upon sensing a predetermined overvoltage of a second polarity at the current source port; blocking current flow caused by an overvoltage of the second polarity from a current sink port; and inhibiting the current sink port upon sensing a predetermined overvoltage surge of the first polarity.
References Cited (Backward Citations)
US4377832A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-04-28 | 1989-10-28 | 1990-04-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-04-28 | 1993-10-28 | 1994-04-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-04-28 | 1997-10-28 | 1998-04-29 | $7700.00 | Window Closed / Lapsed |