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US4885522A
Expired / Lapsed
US
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Constant current source and battery charger
Assignee: Zenith Electronics LLC
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Filing: 1988-11-16
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Granted: 1989-12-05
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Expires: 2008-11-16
Abstract
Abstract A constant current battery charger includes a bucking regulator comprising a power switch transistor, a diode, an inductor and a voltage sensitive switch with adjustable delay for controlling the power switch transistor. The hysteresis or delay is obtained with a Schmitt trigger and the effect is a stable pulse width modulator in which the duty cycle of the power switch transistor is varied. A current foldback circuit includes a zener diode coupled to the battery for changing the sensitivity of the switch to substantially reduce charging current when a battery voltage corresponding to a fully charged state is reached.
Inventors
- 👤 John G. Konopka
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 22:07
CPC Classifications
H; H02; H02J; H02J7/00; H02J7/90; H02J7/971; H02J7/975; H02J7/977
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
134 words
A battery charger operated from a single-ended power supply comprising: pulse width modulation means including a transistor power switch, a diode and an inductor for supplying current to a battery; means for monitoring current flow to said battery; trigger means for controlling the frequency and duty cycle of said pulse width modulation means responsive to said monitoring means; a speed up circuit for said switch transistor comprising a shorting transistor coupled across the base-emitter circuit of said switch transistor and means responsive to said trigger means for driving said shorting transistor conductive; current foldback means including zener diode sensing means for monitoring the voltage of said battery; and means for changing said monitoring means to substantially reduce current flow to said battery when a battery voltage corresponding to a fully charged state is reached.
Claim 2
Dependent Claim
134 words
A battery charger operated from a single-ended power supply comprising: pulse width modulation means including a transistor power switch, a diode and an inductor for supplying current to a battery; means for monitoring current flow to said battery; trigger means for controlling the frequency and duty cycle of said pulse width modulation means responsive to said monitoring means; a speed up circuit for said switch transistor comprising a shorting transistor coupled across the base-emitter circuit of said switch transistor and means responsive to said trigger means for driving said shorting transistor conductive; current foldback means including zener diode sensing means for monitoring the voltage of said battery; and means for changing said monitoring means to substantially reduce current flow to said battery when a battery voltage corresponding to a fully charged state is reached.
Claim 3
Dependent Claim
35 words
A charger in accordance with claim 1 wherein said trigger means includes a Schmitt trigger arrangement coupled between said monitoring means and said power switch transistor for introducing a delay in controlling said duty cycle.
Claim 4
Dependent Claim
28 words
The battery charger of claim 2 wherein said zener diode sensing means comprises a zener diode in a series resistive path between said battery and said Schmitt trigger.
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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) | 1992-12-04 | 1993-06-05 | 1993-12-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-12-04 | 1997-06-05 | 1997-12-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-12-04 | 2001-06-05 | 2001-12-05 | $7700.00 | Window Closed / Lapsed |