US3600630A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Horizontal output tube protection circuit
Assignee: Thomas International Corp
•
Filing: 1969-05-02
•
Granted: 1971-08-17
•
Expires: 1989-05-02
Abstract
Abstract The horizontal scan circuit for the cathode-ray tube of a television receiver having a horizontal power amplifier with a screen grid circuit including a transistor which is biased on by a signal from the horizontal scan circuit. If the input to the power amplifier fails, the bias signal is not present and the transistor turns off, limiting conduction by the power amplifier.
Inventors
- 👤 Grigory Strachanow
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 10:59
CPC Classifications
H; H04; H04N; H04N3/00; H04N3/10; H04N3/16; H04N3/20; H03; H03K; H03K4/00; H03K4/06; H03K4/08; H03K4/085
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
171 words
In a cathode-rAy tube scanning system having a source of scan drive signal, an amplifier having an input coupled to said source of scan drive signal and an output, and an output circuit coupled to the output of said amplifier for applying a scanning signal to said cathode-ray tube, the improvement comprising a protective circuit for said amplifier comprising a source of operating potential; variable impedance means connected in series between said source of operating potential and said amplifier, means for deriving a bias potential from the scanning signal in said output circuit; and means for applying said bias potential to said variable impedance device to cause said variable impedance device to have a low impedance in the presence of a scanning signal in said output circuit to thereby couple substantially full operating potential to said amplifier and the have a high impedance in the absence of the scanning signal in said output circuit to thereby couple a reduced portion of said operating potential to said amplifier to reduce conduction therein.
Claim 2
Dependent Claim
171 words
In a cathode-rAy tube scanning system having a source of scan drive signal, an amplifier having an input coupled to said source of scan drive signal and an output, and an output circuit coupled to the output of said amplifier for applying a scanning signal to said cathode-ray tube, the improvement comprising a protective circuit for said amplifier comprising a source of operating potential; variable impedance means connected in series between said source of operating potential and said amplifier, means for deriving a bias potential from the scanning signal in said output circuit; and means for applying said bias potential to said variable impedance device to cause said variable impedance device to have a low impedance in the presence of a scanning signal in said output circuit to thereby couple substantially full operating potential to said amplifier and the have a high impedance in the absence of the scanning signal in said output circuit to thereby couple a reduced portion of said operating potential to said amplifier to reduce conduction therein.
Claim 3
Dependent Claim
23 words
The protective circuit of claim 1 wherein said amplifier includes a control element to which the operating potential is applied by said circuit.
Claim 4
Dependent Claim
44 words
The protective circuit of claim 2 wherein said amplifier is a tube with multiple control grids, said source of scan drive signal being connected to one of said grids and said operating potential being applied by said variable impedance to another of said grids.
Claim 5
Dependent Claim
24 words
The protective circuit of claim 1 wherein the variable impedance device includes switch means controllable by the bias potential derived from said output circuit.
Claim 6
Dependent Claim
41 words
The protective circuit of claim 1 wherein said variable impedance device includes a switch means in shunt with a resistor, said switch means being conductive in the presence of said bias potential and nonconductive in the absence of said bias potential.
Claim 7
Dependent Claim
47 words
The protective circuit of claim 1 wherein said variable impedance device is a transistor connected in series between said source of operating potential and said amplifier, said transistor having a low impedance in the presence of a scanning signal and a high impedance in the absence thereof.
Claim 8
Dependent Claim
36 words
The protective circuit of claim 6 in which the transistor has an emitter-collector circuit connected in series between the source of operating potential and the amplifier and a base element connected with said bias deriving means.
Claim 9
Dependent Claim
43 words
The protective circuit of claim 7 wherein said amplifier is a tube with multiple control grids, said source of scan drive signal being connected to one of said grids and said operating potential being applied by said circuit to another of said grids.
Claim 10
Dependent Claim
44 words
The protective circuit of claim 8 wherein a resistor is connected in parallel with the emitter-collector circuit of said transistor, said resistor having a resistance which is several times greater than the low impedance of the transistor, but less than the high impedance thereof.
Claim 11
Dependent Claim
28 words
The protective circuit of claim 9 in which a second resistor is connected in series with said transistor between said source of operating potential and said control grid.
Claim 12
Dependent Claim
33 words
The protective circuit of claim 1 wherein said output circuit includes means for developing a supplementary operating potential from said scanning signal, and said bias potential is derived from said supplementary operating potential.
Claim 13
Dependent Claim
52 words
The protective circuit of claim 11 in which said output circuit includes scanning coils for said cathode ray tube, a damper for dissipating the energy in the scanning coil at the end of the scan, and a capacitor charged by said damper, and wherein said bias potential is derived from said capacitor.
Claim 14
Dependent Claim
40 words
The protective circuit of claim 1 in which said amplifier has a current control element and including means for developing from the scanning signal a bias for said element which limits the current of said amplifier to a desired level.
Claim 15
Dependent Claim
30 words
The protective circuit of claim 13 in which said amplifier is a tube and said current control element is a control grid with a grid current bias network connected thereto.
Claim 16
Dependent Claim
46 words
The protective circuit of claim 13 in which said amplifier is a tube and said control element is a control grid, and including means for deriving a scanning signal from the amplifier output and for rectifying said signal to establish a bias for said control grid.
References Cited (Backward Citations)
US3427496A
Cited
US3419751A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-08-16 | 1975-02-15 | 1975-08-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-08-16 | 1979-02-15 | 1979-08-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-08-16 | 1983-02-15 | 1983-08-17 | $7700.00 | Window Closed / Lapsed |