US3597540A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Automatic brightness control responsive to black level of video signal
Assignee: Motorola Solutions Inc
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Filing: 1969-04-01
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Granted: 1971-08-03
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Expires: 1989-04-01
Abstract
Abstract An automatic brightness control circuit in a color television receiver using direct demodulation of the color and brightness signals derives a brightness control voltage by comparing a reference signal, which is indicative of the cutoff or blacklevel condition of the cathode-ray tube, with the video signals supplied to the base of an NPN transistor output amplifier for the green output channel of the receiver. In one embodiment this is accomplished by the use of a differential clipper which is used to compare a reference voltage indicative of the desired black level with a voltage derived from the emitter of the green final amplifier stage during the scanning interval to provide pulses to an integrating circuit, the output of which is used to vary the DC operating level of the green, blue and red driver amplifiers in a closed-loop control system.
Inventors
- 👤 Ernest C Macintyre Jr
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 12:55
CPC Classifications
H; H04; H04N; H04N5/00; H04N5/44; H04N5/57
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
166 words
In a television receiver comprising a cathode-ray tube, a source of video signals including a range of brightness components extending from black to white during the trace intervals of operation of the cathode-ray tube, an improvement therein comprising an automatic brightness control circuit including in combination: means for establishing a predetermined voltage reference level corresponding to the desired black level for said cathode-ray tube; means responsive to the video signals during the trace intervals to provide a voltage representative of the level of the brightness components supplied by the receiver to the cathoderay tube; means for comparing the voltages of the reference voltage establishing means and the signal-responsive means to produce an output voltage indicative of the degree of correspondence of the voltage reference level and the brightness representative voltage; and integrating circuit means responsive to said output voltage for providing an output corresponding to the black level attained by the video signals to control the brightness level of the signals applied to the cathode-ray tube.
Claim 2
Dependent Claim
166 words
In a television receiver comprising a cathode-ray tube, a source of video signals including a range of brightness components extending from black to white during the trace intervals of operation of the cathode-ray tube, an improvement therein comprising an automatic brightness control circuit including in combination: means for establishing a predetermined voltage reference level corresponding to the desired black level for said cathode-ray tube; means responsive to the video signals during the trace intervals to provide a voltage representative of the level of the brightness components supplied by the receiver to the cathoderay tube; means for comparing the voltages of the reference voltage establishing means and the signal-responsive means to produce an output voltage indicative of the degree of correspondence of the voltage reference level and the brightness representative voltage; and integrating circuit means responsive to said output voltage for providing an output corresponding to the black level attained by the video signals to control the brightness level of the signals applied to the cathode-ray tube.
Claim 3
Dependent Claim
73 words
The combination according to claim 1 wherein the television receiver includes an output amplifier and a driver amplifier supplying signals to the output amplifier, with the means responsive to the video signal during the trace interval being responsive to signals obtained from the output amplifier and with the output of the integrating circuit means being connected with the input circuit of the driver amplifier for adjusting the operating level of the driver amplifier.
Claim 4
Dependent Claim
69 words
The combination according to claim 1 wherein the comparing means is a differential amplifier having two inputs, with one input of the differential amplifier being supplied with the voltage reference level obtained from the means for establishing a black voltage reference level and with the output voltage of the means responsive to the video signals during the trace interval being connected to the other input of the differential amplifier.
Claim 5
Dependent Claim
59 words
The combination according to claim 1 wherein the integrated circuit means operates to cause the level of the signals applied to the cathode-ray tube to drift black, and black-level signals sensed by the comparing means result in said output voltage causing the integrating circuit means to drive the level of the signals applied to the cathode-ray tube toward white.
Claim 6
Dependent Claim
136 words
The combination according to claim 1 wherein the comparing means is a differential amplifier having two inputs, one of which is supplied with said reference level voltage and the other input of which is supplied with the output of the means responsive to the video signal during the trace intervals, the output of the differential amplifier being supplied to the integrating circuit means. The combination according to claim 5 wherein said television receiver includes an output amplifier and a driver amplifier supplying signals to the input of the output amplifier, with the output amplifier supplying signals to the cathode-ray tube and the means responsive to signals during the trace interval, and wherein the output of the integrating circuit means is supplied to the input circuit of the driver amplifier to vary the DC operating level thereof.
Claim 7
Dependent Claim
15 words
The combination according to claim 6 wherein the driver and output amplifiers are transistor amplifiers.
References Cited (Backward Citations)
US3315033A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-08-02 | 1975-02-01 | 1975-08-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-08-02 | 1979-02-01 | 1979-08-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-08-02 | 1983-02-01 | 1983-08-03 | $7700.00 | Window Closed / Lapsed |