US3793540A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Constant current source for time delay device
Assignee: American Design Inc
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Filing: 1972-12-04
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Granted: 1974-02-19
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Expires: 1992-12-04
Abstract
Abstract Disclosed is an electronic delay-producing device using an electrolytic condenser and a constant current source, for charging the condenser. With a constant current source, the voltage vs time curve is linear rather than logarithmic and hence switching may be done at a lower voltage level without sacrificing the length of the time delay. Also, leakage currents and their effects on time delays are reduced. The constant current source is derived from a Darlington pair using a transistor as a non-linear resistor to feed the condenser voltage back to the base of the Darlington pair. The output of the pair remains constant over the desired range of condenser voltage values.
Inventors
- 👤 D Devale
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 18:43
CPC Classifications
H; H03; H03K; H03K4/00; H03K4/06; H03K4/08; H03K4/48; H03K4/50
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
70 words
A constant current source for charging a condenser, said source comprising a current source, a condenser to be charged from said source, a Darlington pair having their collectors connected to said source, and means connecting the base of the Darlington pair to the condenser, said means compensating for the non-linear nature of the charging current to produce a substantially linear voltage vs. time curve for the charge in the condenser.
Claim 2
Dependent Claim
70 words
A constant current source for charging a condenser, said source comprising a current source, a condenser to be charged from said source, a Darlington pair having their collectors connected to said source, and means connecting the base of the Darlington pair to the condenser, said means compensating for the non-linear nature of the charging current to produce a substantially linear voltage vs. time curve for the charge in the condenser.
Claim 3
Dependent Claim
15 words
A constant current source as described in claim 1, said means comprising a non-linear resistor.
Claim 4
Dependent Claim
28 words
A constant current source as described in claim 2, said non-linear resistor comprising a transistor in series between the condenser and Darlington pair and having its collector unconnected.
Claim 5
Dependent Claim
37 words
A constant current source as described in claim 3, said transistor In series between the Darlington pair and condenser having its base connected to the condenser and its emitter connected to the base of the Darlington pair.
Claim 6
Dependent Claim
21 words
A constant current source as described in claim 1, and a resistor limiting the base current to the Darlington emitter follower.
Claim 7
Dependent Claim
26 words
A constant current source as described in claim 1, and means for limiting the current to the condenser when the voltage across the condenser is zero.
Claim 8
Dependent Claim
65 words
A constant current source as described in claim 4, and means for limiting the current to the condenser when the voltage across the condenser is zero, said means comprising a first resistor connected across the base of the Darlington emitter follower and the collectors of the Darlington pair, and a second resistor connected in series between the emitter of the Darlington pair and the condenser.
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) | 1977-02-18 | 1977-08-20 | 1978-02-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-02-18 | 1981-08-20 | 1982-02-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-02-18 | 1985-08-20 | 1986-02-19 | $7700.00 | Window Closed / Lapsed |