US4564879A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electronic power overload protection circuit
Assignee: Alcatel Lucent NV
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Filing: 1983-09-08
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Granted: 1986-01-14
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Expires: 2003-09-08
Abstract
Abstract A protection circuit for a push-pull amplifier includes two sensing transistors arranged in respective feedback circuits. The output signals of such sensing transistors, which are indicative of the output voltage, are used to limit the output current of the amplifier in such a manner that the output current is limited to a first threshold decreasing with a steeper slope as a function of the output voltage of the amplifier between predetermined two output voltage values, and a second threshold decreasing with increasing output voltage at a lesser slope above the higher one of the two predetermined output voltage values. This characteristic response can be overridden by appropriate circuitry so long as the temperature of the amplifier is below a predetermined maximum value, so as to make the output current threshold independent of the output voltage.
Inventors
- 👤 Luc A. Bienstman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 15:56
CPC Classifications
H; H03; H03F; H03F1/00; H03F1/52
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
118 words
Electronic power overload protection circuit for limiting the output power of a signal amplifier, comprising means for sensing the output voltage of the amplifier; and means for limiting the output current of the amplifier in dependence on the output of said sensing means, when said output voltage is between a lower one and a higher one of two predetermined output voltage values, to a first threshold which gradually decreases substantially linearly with increasing output voltage at a first rate and, when said output voltage exceeds said higher one of said predetermined output voltage values, to a second threshold which gradually decreases substantially linearly with increasing output voltage at a second rate that is lower than said first rate.
Claim 2
Dependent Claim
118 words
Electronic power overload protection circuit for limiting the output power of a signal amplifier, comprising means for sensing the output voltage of the amplifier; and means for limiting the output current of the amplifier in dependence on the output of said sensing means, when said output voltage is between a lower one and a higher one of two predetermined output voltage values, to a first threshold which gradually decreases substantially linearly with increasing output voltage at a first rate and, when said output voltage exceeds said higher one of said predetermined output voltage values, to a second threshold which gradually decreases substantially linearly with increasing output voltage at a second rate that is lower than said first rate.
Claim 3
Dependent Claim
114 words
The electronic power overload protection circuit as defined in claim 1, wherein said sensing means includes a sensing element having a control input that controls the current flow through said sensing element; and further comprising a first voltage divider having a first and a second part arranged in series with one another between points whose voltage difference and current are proportional to the output voltage and current of the amplifier, said control input being connected to a tap point between said first and second parts of said first voltage divider to control the current flow through said sensing means in dependence on a voltage which is proportional to the output voltage of the amplifier.
Claim 4
Dependent Claim
75 words
The electronic power overload protection circuit as defined in claim 2, wherein said sensing element has a current flow input and an output; and further comprising a second voltage divider having a first and a second part, the latter including at least one two-terminal element with a Zener diode characteristic, said current flow input of said sensing element being connected to a tap point between said first and second parts of said second voltage divider.
Claim 5
Dependent Claim
37 words
The electronic power overload protection circuit as defined in claim 3, wherein said sensing element is a sensing transistor, and wherein said contol and current flow inputs are the base and emitter terminals of said sensing transistor.
Claim 6
Dependent Claim
63 words
The electronic power overload protection circuit as defined in claim 2; further comprising a switching transistor arranged in series with said first voltage divider and having a control input for controlling the flow of current through said switching transistor; and means for supplying to said control input of said switching transistor a current that is related to the output current of the amplifier.
Claim 7
Dependent Claim
84 words
The electronic power overload protection circuit as defined in claim 5, further comprising temperature sensing means, and an additional transistor having an output which normally short-circuits the input of said switching transistor, and a control input which controls the flow of electric current through said additional transistor and is connected to the output of said temperature sensing means such that said additional transistor is prevented from becoming conductive until the temperature as sensed by said temperature sensing means has exceeded a predetermined maximum value.
Claim 8
Dependent Claim
46 words
The electronic power overload protection circuit as defined in claim 6, further comprising a diode-connected current source transistor having a base connected to said additional transistor, the output of said temperature sensing means being connected in shunt across the input circuit of said current source transistor.
Claim 9
Dependent Claim
149 words
The electronic power overload protection circuit as defined in claim 7, and further comprising a voltage divider branched across a temperature-independent direct current voltage source and having a first and a second tapping point, and a further transistor having a collector connected to said tapping point; and wherein said temperature sensing means includes a temperature sensing transistor having a collector connected to the bases of said current source transistor and of said further transistor and a base connected to said second tapping point of said voltage divider, the temperature sensing, further and current source transistors having respective emitters which are connected to one pole of said direct current source, said temperature sensing transistor becoming conductive when the temperature sensed thereby exceeds said maximum value but exhibiting hysteresis so as not to become blocked until the temperature being sensed decreases below a predetermined minimum value lower than said maximum value.
Claim 10
Dependent Claim
67 words
The electronic power overload protection circuit as defined in claim 3, wherein the ratio of the resistance value of said second part of said first voltage divider to that of said second part of said second voltage divider is smaller than the ratio of the resistance of said first part of said first voltage divider to that of said said first part of said second voltage divider.
Claim 11
Dependent Claim
46 words
The electronic power overload protection circuit as defined in claim 3, wherein the resistance values of said second parts of said first and second voltage divider are of a higher order of magnitude than those of said first parts of said first and second voltage divider.
Claim 12
Dependent Claim
48 words
The electronic power overload protection circuit as defined in claim 1, and further comprising means for limiting the output power to a different threshold with the output current being substantially constant with increasing output voltage; and threshold selection means for selecting between said decreasing and said constant thresholds.
Claim 13
Dependent Claim
44 words
The electronic power overload protection circuit as defined in claim 11, wherein said threshold selection means includes means for sensing the temperature of the amplifier, and means for preventing selection of said constant threshold when the amplifier temperature exceeds a predetermined maximum permissible value.
Claim 14
Dependent Claim
33 words
The electronic power overload protection circuit as defined in claim 12, wherein said threshold selection means includes means for selecting said decreasing slope thresholds once the amplifier temperature exceeds said predetermined maximum value.
Claim 15
Dependent Claim
97 words
The electronic power overload protection circuit as defined in claim 11 for use in a push-pull amplifier which includes a differential input stage having an output connected to an input of a buffer amplifier having an output that feeds a push-pull output stage of the amplifier, and further comprising coupling means from said sensing means to the input of said buffer amplifier for coupling two opposite potentials to said input of said buffer amplifier in dependence on the state of said sensing means for selectively supplying and drawing off current from said input of said buffer amplifier.
Claim 16
Dependent Claim
87 words
The electronic power overload protection circuit as defined in claim 14, wherein said output stage includes first and second push-pull input transistors having interconnected bases, means for supplying the output of a constant current source to said interconnected bases, and means for feeding the output of said buffer amplifier to said interconnected bases; and wherein said coupling means includes an output transistor associated with said sensing means and operative for coupling said opposite potentials to said input of said buffer amplifier directly or through a current mirror.
Claim 17
Dependent Claim
28 words
The electronic power overload protection circuit as defined in claim 14, and further comprising a compensating capacitance arranged between the input and the output of the buffer amplifier.
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) | 1989-01-13 | 1989-07-15 | 1990-01-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-01-13 | 1993-07-15 | 1994-01-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-01-13 | 1997-07-15 | 1998-01-14 | $7700.00 | Window Closed / Lapsed |