US3674932A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Automatic beam current limiter
Assignee: RCA Licensing Corp
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Filing: 1971-02-16
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Granted: 1972-07-04
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Expires: 1991-02-16
Abstract
Abstract A normally saturated transistor having its collector electrode serially coupled with the brightness control for a television kinescope, its emitter electrode grounded, and its base electrode coupled to sense the amount of current flowing through such device is effective to dynamically adjust the direct current bias of the video signal chain when that current exceeds a predetermined value, with the change in bias being in an offsetting direction to reduce the kinescope drive. Such an arrangement proves advantageous in eliminating the need for a brightness limiter control potentiometer- of the type utilized in U.S. Pat. No. 3,541,240, for example-which, though normally preset prior to delivery of the receiver to a purchasing customer, could become misadjusted and result in damage to the television picture tube.
Inventors
- 👤 Dal Frank Griepentrog
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 22:56
CPC Classifications
H; H04; H04N; H04N5/00; H04N5/14; H04N5/141
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
260 words
In a television receiver employing a kinescope in which beam current flows as a function of the setting of a brightness control coupled to vary a bias voltage on an electrode thereof and having a plurality of electrodes operated from a high voltage supply which generates suitable operating potentials by the rectification of pulses obtained from appropriate deflection circuits within said receiver, apparatus for limiting the beam current flowing in said kinescope to a desired, predetermined level comprising: a transistor having emitter, base and collector electrodes; a source of operating potential; means including said brightness control coupling the collector electrode of said transistor to said operating potential source; means coupling the emitter electrode of said transistor to a point of reference potential; a source of substantially constant current; and means coupling said substantially constant current source to said high voltage supply and to the base electrode of said transistor dividing its supplied constant current into a first portion providing the beam current for said kinescope and into a second portion providing a bias current for said transistor of a magnitude to cause said transistor to saturate, said lastmentioned means providing said bias current portion until the beam current flowing in said kinescope is increased to said predetermined value, beyond which increases in said beam current decrease said bias current portion bringing said tranSistor out of saturation and changing its collector electrode potential to vary the bias voltage coupled by said brightness control to said kinescope in an offsetting manner, whereby said kinescope beam current is stabilized at said desired value.
Claim 2
Dependent Claim
260 words
In a television receiver employing a kinescope in which beam current flows as a function of the setting of a brightness control coupled to vary a bias voltage on an electrode thereof and having a plurality of electrodes operated from a high voltage supply which generates suitable operating potentials by the rectification of pulses obtained from appropriate deflection circuits within said receiver, apparatus for limiting the beam current flowing in said kinescope to a desired, predetermined level comprising: a transistor having emitter, base and collector electrodes; a source of operating potential; means including said brightness control coupling the collector electrode of said transistor to said operating potential source; means coupling the emitter electrode of said transistor to a point of reference potential; a source of substantially constant current; and means coupling said substantially constant current source to said high voltage supply and to the base electrode of said transistor dividing its supplied constant current into a first portion providing the beam current for said kinescope and into a second portion providing a bias current for said transistor of a magnitude to cause said transistor to saturate, said lastmentioned means providing said bias current portion until the beam current flowing in said kinescope is increased to said predetermined value, beyond which increases in said beam current decrease said bias current portion bringing said tranSistor out of saturation and changing its collector electrode potential to vary the bias voltage coupled by said brightness control to said kinescope in an offsetting manner, whereby said kinescope beam current is stabilized at said desired value.
Claim 3
Dependent Claim
37 words
The apparatus of claim 1 wherein said source of substantially constant current includes a source of substantially constant voltage coupled by a first resistance to said high voltage supply and to the base electrode of said transistor.
Claim 4
Dependent Claim
21 words
The apparatus of claim 2 wherein said source of operating potential for said transistor comprises said source of substantially constant voltage.
Claim 5
Dependent Claim
67 words
The apparatus of claim 3 wherein said means coupling the collector electrode of said transistor to said operating potential source includes second and third resistances respectively coupling opposite ends of said brightness control to said transistor and to said potential source, with said second and third resistances serving to limit the range of available bias voltage developed by said brightness control as a function of transistor conductivity.
Claim 6
Dependent Claim
48 words
The apparatus of claim 4 wherein said supplied current dividing means connects said source of substantially constant current directly to the base electrode of said transistor and wherein there is also included fourth and fifth resistances serially connected to couple said current source to said high voltage supply.
Claim 7
Dependent Claim
87 words
The apparatus of claim 5 wherein a first capacitance is included to couple the junction of said fourth and fifth resistances to said point of reference potential and wherein a second capacitance is also included to couple the junction of said fifth resistance with said high voltage supply to said reference potential point, said first and second capacitances cooperating with said fourth and fifth resistances to provide a pair of filter networks operative to reduce undesired horizontal and vertical scanning rate modulation of said kinescope beam current.
Claim 8
Dependent Claim
55 words
The apparatus of claim 6 wherein a third capacitance and sixth resistance are further coupled in series between the base and collector electrodes of said transistor to reduce the alternating current gain provided by said transistor and compensatingly reduce signal phase shifts introduced by said filter networks which tend to limit said beam current flow.
Claim 9
Dependent Claim
70 words
The apparatus of claim 7 wherein said fourth and fifth resistances comprise a pair of resistors of dissimilar power handling capabilities such that surges of voltage from said high voltage supply have a greater tendency to open-circuit the one of said pair of resistors closer to said high voltage supply prior to any open-circuiting of the other of said pair of resistors closer to said source of substantially constant current.
Claim 10
Dependent Claim
71 words
The apparatus of claim 1 for use in a television receiver of the type employing a high voltage supply including a voltage multiplying circuit responsive to pulses supplied from a winding on the horizontal output transformer of said receiver, and wherein said last-mentioned means is coupled to a point in said multiplier circuit at which a direct current is available as being representative of the beam current flow in said kinescope.
Claim 11
Dependent Claim
79 words
The apparatus of claim 1 for use in a television receiver of the type employing a high voltage supply including a voltage quadrupler circuit responsive to flyback pulses supplied from a secondary winding on the horizontal output transformer of said receiver, and wherein said last-mentioned means is coupled to a point in said voltage quadrupler at which a direct current is available for conducting current in response to, and directly proportional to, the beam current flowing in said kinescope.
Claim 12
Dependent Claim
81 words
The apparatus of claim 1 wherein said last-mentioned means provide said bias current portion until the beam current flowing in said kinescope is increased to said predetermined value by advancement of said brightness control, beyond which advances in said brightness control setting to increase said beam curreNt decrease said bias current portion bringing said transistor out of saturation and changing its collector electrode potential to vary the bias voltage coupled by said brightness control to said kinescope in an offsetting manner.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-07-04 | 1976-01-03 | 1976-07-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-07-04 | 1980-01-03 | 1980-07-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-07-04 | 1984-01-03 | 1984-07-04 | $7700.00 | Window Closed / Lapsed |