Patent US4890185A successfully refreshed from Google Patents.
US4890185A
Expired / Lapsed
US
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Circuit for protecting a switching transistor
Assignee: Lenze GmbH and Co Kg
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Filing: 1988-12-13
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Granted: 1989-12-26
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Expires: 2008-12-13
Abstract
Abstract A circuit for protecting a switching transistor connected between a direct-current voltage source and an inductive load has a voltage-limiting element connected between the source and the transistor for switching the transistor when the voltage of the source exceeds a predetermined limit, elements for deriving from the voltage-limiting element a control signal when the source voltage exceeds the predetermined limit, and a variable pulse-width modulator connected to a control input of the transistor and receiving the signal from the means. The modulator decreases pulse width when the source voltage exceeds the limit.
Inventors
- 👤 Heinz-Dietmar Karl
- 👤 Manfred Tinebor
- 👤 Josef Lackhove
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 03:43
CPC Classifications
H; H02; H02H; H02H9/00; H02H9/04; H02P; H02P7/00; H02P7/06; H02P7/18; H02P7/24; H02P7/28; H02P7/285; H02P7/288; H03; H03K; H03K17/00; H03K17/08; H03K17/082; H03K17/0822
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
94 words
A circuit for protecting a switching transistor connected between a direct-current voltage source and an inductive load, the circuit comprising: a voltage-limiting element connected between the source and the transistor for switching the transistor when the voltage of the source exceeds a predetermined limit; means for deriving from the voltage-limiting element a control signal when the source voltage exceeds the predetermined limit; and a variable pulse-width modulator connected to a control input of the transistor and receiving the signal from the means, the modulator decreasing pulse width when the source voltage exceeds the limit.
Claim 2
Dependent Claim
94 words
A circuit for protecting a switching transistor connected between a direct-current voltage source and an inductive load, the circuit comprising: a voltage-limiting element connected between the source and the transistor for switching the transistor when the voltage of the source exceeds a predetermined limit; means for deriving from the voltage-limiting element a control signal when the source voltage exceeds the predetermined limit; and a variable pulse-width modulator connected to a control input of the transistor and receiving the signal from the means, the modulator decreasing pulse width when the source voltage exceeds the limit.
Claim 3
Dependent Claim
22 words
The circuit defined in claim 1 wherein the control signal is formed by voltages exceeding the avalanche voltage of the voltage-limiting element.
Claim 4
Dependent Claim
21 words
The circuit defined in claim 1 wherein the switching transistor is switched when the control signal exceeds a predetermined voltage level.
Claim 5
Dependent Claim
54 words
The circuit defined in claim 1 wherein the voltage-limiting element is a zener diode having a cathode connected to an input element of the switching transistor and an anode, the means including a condenser connected to the anode and a discharge resistor connected between the condenser-anode junction and an input of the pulse modulator.
Claim 6
Dependent Claim
35 words
The circuit defined in claim 4, further comprising: a current regulator connected at a summing point the condenser and to the input of the modulator; and a desired-value signal generator connected to the summing point.
Claim 7
Dependent Claim
28 words
The circuit defined in claim 4, further comprising a second zener diode connected between the anode of the first-mentioned zener diode and the input of the switching transistor.
Claim 8
Dependent Claim
33 words
The circuit defined in claim 6 wherein the avalanche voltage of the second zener diode is such that the condenser can charge sufficiently to set the ratio of the modulator equal to 0.
References Cited (Backward Citations)
US4672527A
Cited
US4589049A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-12-25 | 1993-06-26 | 1993-12-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-12-25 | 1997-06-26 | 1997-12-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-12-25 | 2001-06-26 | 2001-12-26 | $7700.00 | Window Closed / Lapsed |