US4365265A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Color temperature control circuit
Assignee: Sanyo Electric Co Ltd
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Filing: 1981-06-19
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Granted: 1982-12-21
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Expires: 2001-06-19
Abstract
Abstract A color temperature control circuit for use in a color television receiver includes a first differential amplifier which compares a luminance signal with a reference voltage and when the luminance signal drops below the reference voltage, it is so actuated as to derive a current from a green chrominance signal to reduce the green chrominance signal level, and the second differential amplifier which compares the luminance signal with the reference voltage and when the luminance signal drops below the reference voltage, it is so actuated as to derive a current from a red chrominance signal to reduce the red chrominance signal level. When the first and the second differential amplifiers are actuated, signal level of a blue chrominance signal is apparently increased to turn a white image to a bluish white image.
Inventors
- 👤 Kaoru Tsujita
- 👤 Sigeki Tobioka
- 👤 Ikuo Monden
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 16:41
CPC Classifications
H; H04; H04N; H04N9/00; H04N9/64; H04N9/73
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
249 words
A color temperature control circuit for use in a color television receiver for changing the ratio of blue, red and green chrominance signals obtained from a chrominance signal demodulator in relation to a luminance signal obtained from a video amplifier, said color temperature control circuit comprising: a reference voltage generator for generating a predetermined reference voltage; a first differential amplifier connected to said chrominance signal demodulator for defining a first current path for said green chrominance signal to ground, said first differential amplifier also connected to said reference voltage generator and said video amplifier for comparing said luminance signal with said reference voltage such that when said luminance signal drops below said reference voltage, said first current path actuates to conduct said green chrominance signal to ground with a conductivity determined by the degree of said voltage drop of luminance signal below said reference voltage to reduce the green chrominance signal level; and a second differential amplifier connected to said chrominance signal demodulator for defining a second current path for said red chrominance signal to ground, said second differential amplifier also connected to said reference voltage generator and said video amplifier for comparing said luminance signal with said reference voltage such that when said luminance signal drops below said reference voltage, said second current path actuates to conduct said red chrominance signal to ground with a conductivity determined by the degree of said voltage drop of luminance signal below said reference voltage to reduce the red chrominance signal level.
Claim 2
Dependent Claim
249 words
A color temperature control circuit for use in a color television receiver for changing the ratio of blue, red and green chrominance signals obtained from a chrominance signal demodulator in relation to a luminance signal obtained from a video amplifier, said color temperature control circuit comprising: a reference voltage generator for generating a predetermined reference voltage; a first differential amplifier connected to said chrominance signal demodulator for defining a first current path for said green chrominance signal to ground, said first differential amplifier also connected to said reference voltage generator and said video amplifier for comparing said luminance signal with said reference voltage such that when said luminance signal drops below said reference voltage, said first current path actuates to conduct said green chrominance signal to ground with a conductivity determined by the degree of said voltage drop of luminance signal below said reference voltage to reduce the green chrominance signal level; and a second differential amplifier connected to said chrominance signal demodulator for defining a second current path for said red chrominance signal to ground, said second differential amplifier also connected to said reference voltage generator and said video amplifier for comparing said luminance signal with said reference voltage such that when said luminance signal drops below said reference voltage, said second current path actuates to conduct said red chrominance signal to ground with a conductivity determined by the degree of said voltage drop of luminance signal below said reference voltage to reduce the red chrominance signal level.
Claim 3
Dependent Claim
90 words
A color temperature control circuit as claimed in claim 1, wherein said first differential amplifier comprises: a first transistor having its base connected to said video amplifier for receiving said luminance signal; a second transistor having its base connected to said reference voltage generator for receiving said reference voltage and its collector connected to said chrominance signal demodulator for receiving said green chrominance signal, said second transistor serving as said first current path; and a first constant current source connected to emitter of each of said first and second transistors.
Claim 4
Dependent Claim
90 words
A color temperature control circuit as claimed in claim 2, wherein said second differential amplifier comprises: a third transistor having its base connected to said video amplifier for receiving said luminance signal; a fourth transistor having its base connected to said reference voltage generator for receiving said reference voltage and its collector connected to said chrominance signal demodulator for receiving said red chrominance signal, said fourth transistor serving as said second current path; and a second constant current source connected to emitter of each of said first and second transistors.
Claim 5
Dependent Claim
64 words
A color temperature control circuit as claimed in claim 2, wherein said second differential amplifier comprises: said first transistor; a third transistor having its base connected to said reference voltage generator for receiving said reference voltage and its collector connected to said chrominance signal demodulator for receiving said red chrominance signal; and said first constant current source connected to emitter of said third transistor.
Claim 6
Dependent Claim
67 words
A color temperature control circuit as claimed in claim 1, wherein said first and second differential amplifiers comprise first and second resistors, respectively, inserted into said first and second current paths for regulating the current flowing through the respective current paths such that the ratio of resistance of said first and second resistors is equal to the ratio of level of said green and red chrominance signals.
Claim 7
Dependent Claim
19 words
A color temperature control circuit as claimed in claim 1, wherein said reference voltage generator comprises a variable resistor.
Claim 8
Dependent Claim
25 words
A color temperature control circuit as claimed in claim 1, wherein said first and second differential amplifiers are assembled on a chip of integrated circuit.
References Cited (Backward Citations)
US3562410A
Cited
US4064529A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1985-12-20 | 1986-06-21 | 1986-12-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1989-12-20 | 1990-06-21 | 1990-12-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1993-12-20 | 1994-06-21 | 1994-12-21 | $7700.00 | Window Closed / Lapsed |