US4841219A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Lossless overcurrent sensing circuit for voltage regulator
Assignee: Hewlett Packard Development Co LP
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Filing: 1988-05-10
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Granted: 1989-06-20
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Expires: 2008-05-10
Abstract
Abstract An overcurrent sensing circuit for use with a voltage regulator, such as a linear post regulator for a power supply, utilizes a field effect transistor (FET) both as the pass element for the voltage regulator, and as a current sense resistor. The output voltage from the FET is fed back to an input of a differential amplifier, which generates a control voltage for the gate of the FET, so that the output voltage will remain constant. If an overcurrent condition occurs through the FET, the control voltage will exceed a set point, thus driving the FET into saturation, and sensing circuitry will generate an overcurrent output that can be utilized to shut off the regulator. A single sensing circuit can be used for multiple regulators if desired.
Inventors
- 👤 Kevin J. Lonergan
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 17:59
CPC Classifications
G; G05; G05F; G05F1/00; G05F1/10; G05F1/46; G05F1/56; G05F1/565; G05F1/569; G05F1/573
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
149 words
An overcurrent sensing circuit for voltage regulators comprising: at least a first voltage regulator circuit including: (a) an input; (b) an output; (c) a field effect transistor having a source, a drain, and a gate, and being disposed between said input and said output so that current can flow from said input through the drain and the source to said output; and, (d) voltage feedback means connected between said output and a first input of an amplifier circuit, said amplifier circuit generating as an output, a control voltage that is fed to the gate of the field effect transistor, said control voltage being responsive to the circuit output voltage; and, means to sense when the magnitude of said control voltage exceeds a set point at which said field effect transistor is driven into saturation thereby, said point being indicative of an overcurrent condition between said input and said output.
Claim 2
Dependent Claim
149 words
An overcurrent sensing circuit for voltage regulators comprising: at least a first voltage regulator circuit including: (a) an input; (b) an output; (c) a field effect transistor having a source, a drain, and a gate, and being disposed between said input and said output so that current can flow from said input through the drain and the source to said output; and, (d) voltage feedback means connected between said output and a first input of an amplifier circuit, said amplifier circuit generating as an output, a control voltage that is fed to the gate of the field effect transistor, said control voltage being responsive to the circuit output voltage; and, means to sense when the magnitude of said control voltage exceeds a set point at which said field effect transistor is driven into saturation thereby, said point being indicative of an overcurrent condition between said input and said output.
Claim 3
Dependent Claim
68 words
The overcurrent sensing circuit of claim 1, wherein said means to sense when the magnitude of said control voltage exceeds a set point comprises: a Zener diode having a cathode connected to the control voltage output of said amplifier circuit, and chosen so that it begins to conduct current when the diode voltage exceeds said set point; and, means to sense when current flows through said Zener diode.
Claim 4
Dependent Claim
64 words
The overcurrent sensing circuit of claim 2, wherein said means to sense when current flows through said Zener diode comprises a comparator amplifier having a first input connected to an anode of said Zener diode; a second input connected to a reference voltage; and, an output which generates a voltage when the voltage at the first input exceeds the voltage of the second input.
Claim 5
Dependent Claim
71 words
The overcurrent sensing circuit of claim 3, further comprising: at least a second voltage regulator circuit including: at least a second Zener diode having a cathode connected to a control voltage output of a second amplifier circuit; and an anode also connected to said first input of said comparator amplifier; whereby, a voltage output will be generated by said comparator amplifier is current flows through any one of said Zener diodes.
Claim 6
Dependent Claim
46 words
The overcurrent sensing circuit of claim 3 further including a timing circuit having an input connected to the output of said comparator amplifier which generates a voltage output for a set period of time when a voltage is generated at the output of said comparator amplifier.
References Cited (Backward Citations)
US4176309A
Cited
US4254372A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-06-19 | 1992-12-19 | 1993-06-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-06-19 | 1996-12-19 | 1997-06-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-06-19 | 2000-12-19 | 2001-06-20 | $7700.00 | Window Closed / Lapsed |