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US5285366A
Expired / Lapsed
US
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Current limit circuit in current mode power supplies
Assignee: Astec International Ltd
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Filing: 1992-09-24
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Granted: 1994-02-08
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Expires: 2012-09-24
Abstract
Abstract A current mode power supply having a switching topology with a pulse width modulated duty cycle with a current sensing resistor is short circuit protected by a current limit circuit. The current limit circuit has inputs coupled to the current sensing resistor and the dc source input. The current limit circuit provide an output signal connected to the pulse width modulator, for shortening the duty cycle in dependence upon the sum of voltage signals from the current sensing resistor and the dc source input.
Inventors
- 👤 Boris Zaretsky
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 12:09
CPC Classifications
H; H02; H02H; H02H7/00; H02H7/10; H02H7/12; H02H7/1213
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
128 words
A current mode power supply, comprising: a switching topology including a transformer having primary and secondary windings, a controllable switch connected between one side of the primary winding and a first reference potential input via current sensing means, a dc source input connected to the other side of the primary winding and a pulse width modulator having a current sensing input and a shut down input for operating the controllable switches to control the duty cycle of the power supply; and current limit means, having inputs coupled to the current sensing means and the dc source input and an output connected to the control means, for shortening the duty cycle in dependence upon the sum of voltage signals from the current sensing means and the dc source input.
Claim 2
Dependent Claim
128 words
A current mode power supply, comprising: a switching topology including a transformer having primary and secondary windings, a controllable switch connected between one side of the primary winding and a first reference potential input via current sensing means, a dc source input connected to the other side of the primary winding and a pulse width modulator having a current sensing input and a shut down input for operating the controllable switches to control the duty cycle of the power supply; and current limit means, having inputs coupled to the current sensing means and the dc source input and an output connected to the control means, for shortening the duty cycle in dependence upon the sum of voltage signals from the current sensing means and the dc source input.
Claim 3
Dependent Claim
25 words
A current mode power supply as claimed in claim 2 wherein the current limit means comprises series connected common emitter transistor, first and second comparators.
Claim 4
Dependent Claim
34 words
A current mode power supply as claimed in claim 2 wherein the base of the transistor is connected to the current sensing means and the dc source input via first and second resistors, respectively.
Claim 5
Dependent Claim
27 words
A current mode power supply as claimed in claim 3 wherein the first and second comparators have inverting input connected to second and third reference potentials, respectively.
Claim 6
Dependent Claim
31 words
A current mode power supply as claimed in claim 4 wherein the outputs of first and second comparators are connected to the first reference potential via first and second capacitors, respectively.
Claim 7
Dependent Claim
50 words
A current mode power supply as claimed in claim 5 wherein the first capacitor is connected to a supply potential via a resistor, the resistor and the first capacitor for providing a time constant to the second comparator which together with the third reference potential produce a suitable time delay.
Claim 8
Dependent Claim
18 words
A current mode power supply as claimed in claim 6 wherein the current sensing means comprises a resistor.
Claim 9
Dependent Claim
19 words
A current mode power supply as claimed in claim 7 wherein the controllable switch comprises a field effect transistor.
References Cited (Backward Citations)
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1997-02-07 | 1997-08-09 | 1998-02-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-02-07 | 2001-08-09 | 2002-02-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2005-02-07 | 2005-08-09 | 2006-02-08 | $7700.00 | Window Closed / Lapsed |