US3649901A
Expired / Lapsed
US
⏱️ 0.0 years remaining
High voltage hold-down circuit
Assignee: RCA Licensing Corp
•
Filing: 1971-03-05
•
Granted: 1972-03-14
•
Expires: 1991-03-05
Abstract
Abstract Loss of the flyback pulse which regulates the bias applied to the control grid of the horizontal output tube of a television receiver can cause the high voltage developed for its picture tube to increase to a value at which X-radiations can be produced. Use of a dropping resistor to reduce the screen grid bias on the horizontal output tube in response to the increase in screen current which results when this negative voltage control is lost offsets this increase-and, with the further use of a clamping diode for the screen grid, maintains normal high voltage operation during non-fault conditions.
Inventors
- 👤 Ronald Keith Waltner
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 07:59
CPC Classifications
H; H04; H04N; H04N3/00; H04N3/10; H04N3/16; H04N3/20; H02; H02H; H02H7/00; H02H7/10; H02H7/12; H02H7/1209
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
187 words
In a high voltage generation circuit including an output transformer and responsive to periodically recurring voltage pulses for developing a unidirectional potential to energize an image reproducing device capable of emitting X-radiation at applied energizing potentials beyond an acceptable limit, the combination comprising: a high voltage output tube having first and second control electrodes; first means biasing said first control electrode to a first predetermined voltage value; second means biasing said second control electrode to a second predetermined voltage value at which said high voltage tube operates to develop said unidirectional potential for said image reproducing device, said second predetermined voltage value being dependent at least in part upon the presence of a flyback pulse supplied from said output transformer and in the absence of which causes said high voltage tube to develop a unidirectional potential for said image reproducing device beyond said acceptable limit; and third means responsive to the absence of said flyback pulse for biasing said first control electrode to a different voltage value to reestablish the operating mode of said high voltage tube and stabilize said developed unidirectional potential below said radiation limit.
Claim 2
Dependent Claim
187 words
In a high voltage generation circuit including an output transformer and responsive to periodically recurring voltage pulses for developing a unidirectional potential to energize an image reproducing device capable of emitting X-radiation at applied energizing potentials beyond an acceptable limit, the combination comprising: a high voltage output tube having first and second control electrodes; first means biasing said first control electrode to a first predetermined voltage value; second means biasing said second control electrode to a second predetermined voltage value at which said high voltage tube operates to develop said unidirectional potential for said image reproducing device, said second predetermined voltage value being dependent at least in part upon the presence of a flyback pulse supplied from said output transformer and in the absence of which causes said high voltage tube to develop a unidirectional potential for said image reproducing device beyond said acceptable limit; and third means responsive to the absence of said flyback pulse for biasing said first control electrode to a different voltage value to reestablish the operating mode of said high voltage tube and stabilize said developed unidirectional potential below said radiation limit.
Claim 3
Dependent Claim
29 words
The combination of claim 1 wherein said first means biases the screen grid of said high voltage tube and said second means biases the control grid of said tube.
Claim 4
Dependent Claim
86 words
The combination of claim 2 wherein said first means biases the screen grid to a positive voltage, wherein said second means biases the control grid to a negative voltage in the presence of said flyback pulse and to a less negative voltage in the absence of said flyback pulse, and wherein said third means responds to the absence of said pulse to bias the screen grid to a positive voltage of magnitude less than that to which said screen grid is biased by said first means.
Claim 5
Dependent Claim
115 words
The combination of claim 3 wherein said first means includes a diode coupling a first source of bias potential to said screen grid, wherein said third means includes a resistor coupling a second source of bias potential to said screen grid, and wherein said third means responds to the current flow produced in the screen grid circuit of said high voltage tube to forward bias said diode in the presence of said flyback pulse and to reverse bias said diode in the absence of said pulse and lower the bias voltage at said screen grid in the absence of said pulse as compared to the bias voltage thereat in the presence of said flyback pulse.
Claim 6
Dependent Claim
53 words
The combination of claim 3 wherein said output transformer supplies positive-going flyback pulses during the normal operation thereof and wherein said second means rectifies said pulses to a negative value for combination with a positive source of potential and with a negative portion of said recurring voltage pulses to bias said control grid.
Claim 7
Dependent Claim
44 words
The combination of claim 4 wherein there is also included means for bypassing said screen grid to ground in the presence of internal sparking within said high voltage tube for the protection of said diode and said first source of bias potential coupled thereto.
Claim 8
Dependent Claim
68 words
The combination of claim 4 wherein said first means includes a diode having a cathode electrode coupled to a first source of positive bias potential and an anode electrode coupled to said screen grid by a first resistor, and wherein said third means includes a second resistor of substantially greater resistance value than said first resistor coupling said first resistor to a second source of positive bias potential.
Claim 9
Dependent Claim
43 words
The combination of claim 5 wherein said second means includes a time constant circuit including a first capacitor and a voltage dependent resistor which exhibits a non-linear resistance characteristic cooperative with said capacitor to rectify said flyback pulses to a negative voltage value.
Claim 10
Dependent Claim
23 words
The combination of claim 7 wherein there is further included a capacitor coupling the junction of said first and second resistors to ground.
References Cited (Backward Citations)
US2697798A
Cited
US2589299A
Cited
US3030444A
Cited
US3340423A
Cited
US3417282A
Cited
US3419751A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-03-14 | 1975-09-13 | 1976-03-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-03-14 | 1979-09-13 | 1980-03-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-03-14 | 1983-09-13 | 1984-03-14 | $7700.00 | Window Closed / Lapsed |