US4047049A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Drive circuit with constant current output
Assignee: Northrop Grumman Guidance and Electronics Co Inc
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Filing: 1975-10-28
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Granted: 1977-09-06
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Expires: 1995-10-28
Abstract
Abstract A constant current drive circuit that can be driven directly from the output of a shift register which can find use, for example, as a constant current source for a light emitting diode (LED) to ensure uniform birghtness throughout a display surface that includes a plurality of LEDs.
Inventors
- 👤 Fred William Erickson
- 👤 Roy Hiroshi Nakahara
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 06:37
CPC Classifications
G; G04; G04G; G04G9/00; G04G9/08; G04G9/10; G05; G05F; G05F3/00; G05F3/02; G05F3/08; G05F3/10; G05F3/16; G05F3/20; G05F3/22
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
139 words
A constant current drive circuit comprising: (a) first electrical energy source means supplying a first electrical energy level output, (b) second electrical energy source means responsive to said first electrical energy level output and supplying a selectively variable second energy level output, (c) a resistor connected in electrical series with said first electrical energy source means and responsive to said first electrical energy level output, (d) bistable control means including triode means responsive to said first electrical energy level output through said resistor and to said second electrical energy level output, said bistable triode means providing a third electrical energy level output having a constant current determinable by said selectively variable second energy level output, and (e) signal generating means selectively enabling and disabling said triode means so that the constant current drive circuit is selectively enabled and disabled.
Claim 2
Dependent Claim
139 words
A constant current drive circuit comprising: (a) first electrical energy source means supplying a first electrical energy level output, (b) second electrical energy source means responsive to said first electrical energy level output and supplying a selectively variable second energy level output, (c) a resistor connected in electrical series with said first electrical energy source means and responsive to said first electrical energy level output, (d) bistable control means including triode means responsive to said first electrical energy level output through said resistor and to said second electrical energy level output, said bistable triode means providing a third electrical energy level output having a constant current determinable by said selectively variable second energy level output, and (e) signal generating means selectively enabling and disabling said triode means so that the constant current drive circuit is selectively enabled and disabled.
Claim 3
Dependent Claim
90 words
The constant current drive circuit of claim 1 in which said bistable triode means includes a current source transistor and a current regulating transistor, said current source transistor having an emitter connected through said resistor to said first electrical energy source means and a collector as said third output, said current regulating transistor having an emitter-collector junction connected between the base of said current source transistor and said second electrical energy source means with the base of said current regulating transistor connected to the emitter of said current source transistor.
Claim 4
Dependent Claim
18 words
The constant current drive circuit of claim 1 in which said signal generating means is a shift register.
Claim 5
Dependent Claim
30 words
The constant current drive circuit of claim 1 in which said signal generating means includes a signal resistor connected in electrical series with the base of said current source transistor.
Claim 6
Dependent Claim
31 words
The constant current drive circuit of claim 1 in which said signal generating means includes a signal generating electrical energy source means supplying a selectively variable fourth electrical energy level output.
Claim 7
Dependent Claim
59 words
The constant current drive circuit of claim 5 in which said signal generating means selectively disables said triode means when said fourth electrical energy level output and said first electrical energy level output are substantially equal, and selectively enables said triode means when said fourth electrical energy level output is substantially less than said first electrical energy level output.
Claim 8
Dependent Claim
108 words
The constant current drive circuit of claim 2 in which said third electrical energy level output is determined by (V.sub.EB + V.sub.PROG)/R1 Where V EB is the enabling voltage for the emitter-base junction of said current regulating transistor, V PROG is the voltage output of said selectively variable second energy level output, and R1 is the ohmic resistance of said resistor so that a voltage drop across said resistor equalling V PROG + V EB enables said current regulating transistor thereby stabilizing the voltage drop across said resistor and concomitantly developing a constant current through said resistor as the desired component of said third electrical energy level output.
Claim 9
Dependent Claim
26 words
The constant current drive circuit of claim 1 which further comprises a driven device responsive to said third electrical energy level output supplying said constant current.
Claim 10
Dependent Claim
18 words
The constant current drive circuit of claim 8 in which said driven device is a light emitting diode.
Claim 11
Dependent Claim
24 words
The constant current drive circuit of claim 8 in which said driven device includes a plurality of light emitting diodes electrically connected in parallel.
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) | 1980-09-05 | 1981-03-07 | 1981-09-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-09-05 | 1985-03-07 | 1985-09-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-09-05 | 1989-03-07 | 1989-09-06 | $7700.00 | Window Closed / Lapsed |