CN100479493C - Automatic dynamic limiting method and circuit for CRT beam current - Google Patents
Automatic dynamic limiting method and circuit for CRT beam current Download PDFInfo
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- CN100479493C CN100479493C CNB2005100330290A CN200510033029A CN100479493C CN 100479493 C CN100479493 C CN 100479493C CN B2005100330290 A CNB2005100330290 A CN B2005100330290A CN 200510033029 A CN200510033029 A CN 200510033029A CN 100479493 C CN100479493 C CN 100479493C
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Abstract
A method for dynamically and automatically limiting CRT beam current includes sampling step, eliminating compensation step and over current limitation step .The circuit for realizing the method consists of CRT, video processing circuit final video amplifying circuit, current sampling circuit of picture tube cathode and switching circuit for switching signal path.
Description
Technical field
The present invention relates to guard method, particularly to the method for carrying out dynamic constraints and the circuit thereof of beam current of kinescope to the CRT picture tube.
Background technology
As Fig. 1, traditional automatic beam electronic current restriction (ABL) circuit is that electric current with extra-high voltage (EHT) generator is as the reference signal.The tube cathode electrons emitted is just in the driving current downflow of extra-high voltage (EHT), so the electric current of EHT generator reflected the size of beam electronic current, and its sample resistance R that flows through has formed reference voltage signal.And filter capacitor C is set, it is the influence that is not subjected to sample resistance R for the stability that guarantees EHT voltage that filter capacitor C is set.
So, owing to exist RC to constitute in the circuit, certainly exist the time lag link, its delayed action makes reference voltage can only reflect the variation of lower frequency, and can't reflect fast-changing part in the image.
In addition, also because self there is parasitic capacitance in the EHT generator, and the filter capacitor that adds because of the stability requirement of EHT, cause the obtained reference signal of traditional ABL circuit in fact by the energy-storage travelling wave tube filtering in the circuit, thereby can only reflect more at a slow speed the bright dark variation of image, that is to say, when traditional ABL circuit just occurs than all brighter scene of large tracts of land in entire image, just provide constraints when just average beam current is bigger.
For another situation; when having only topography brighter; this moment, the moment overload may appear in beam current of kinescope; but because this moment, average beam current was also little; traditional ABL circuit is not limited it, that is to say, traditional in this case ABL circuit can not provide effective protection to picture tube; so, its protective effect obviously is incomplete.Though and the brighter situation of topography can not occupy the picture of TV for a long time, the frequency of its appearance is very high, and the probability of moment overload to occur also be very high to beam electronic current in other words, therefore, must improve for this situation.
Summary of the invention
At above-mentioned problem, the invention provides the method and the circuit of the dynamic auto restriction of a kind of CRT beam electronic current, this method and circuit can in time be limited the moment overload of beam electronic current, for picture tube provides perfect protection scheme.
Another object of the present invention is to take out the reference signal of the cathode current of the reflection image beams electric current that can not have sluggishness as ABL;
Another object of the present invention is that the black-out intervals of removing in the reference signal is that part of to the fast reaction injurious effects;
Another object of the present invention is that target electric current moment overload can be limited timely; the cathode current that adopts real-time beam electronic current is as the ABL reference signal; and can accelerate the reaction speed of ABL, accomplish that moment starts to control, thereby in time picture tube is carried out general protection fast.
Based on this, the present invention is achieved in that
The method of the dynamic auto restriction of a kind of CRT beam electronic current, this method may further comprise the steps:
Step 1 is taken out the tube cathode electric current as the reference signal from final video amplifier;
The present invention is connected on sample circuit in the tube cathode loop, also is the driven object of final video amplifier, takes out the tube cathode electric current as the reference signal from final video amplifier, does the authenticity that has just guaranteed sample from the sampling link like this.Usually, cathode current can not have the variation of sluggish reflection beam current of kinescope, compares with the reference signal of taking out in extra-high voltage (EHT) generator loop, and response speed is faster, can reflect the situation of change of beam current of kinescope thus real-time and accurately, be beneficial to effective control.
In the described step 2, removing in the reference signal that part of corresponding to row, field scan black-out intervals, is realized by the video switch circuit of composite blanking signal control with one.Because the black-out intervals negative electrode is emitting electrons not; cathode current is cut off; this will make the mean value of whole cathode current of scan period obviously reduce, thus when cathode current be that moment when overload restriction cathode current executive circuit may not made any reaction, just be unfavorable for the protection of CRT certainly.
In the described step 2, the part of removing embeds with the mean value of reference signal long-time (row, field scan forward stroke interval) tube cathode electric current, and this also is to realize with the same video switch circuit that controlled by composite blanking signal.
Obtaining of reference signal long-time (row, field scan forward stroke interval) mean value is to use filter that the reference signal of row, field scan forward stroke interval is smoothly realized.The filter that is used for the reference signal during the level and smooth line traversal, its time constant should be greater than the line-scanning period, be used for the filter of the reference signal of level and smooth field scan forward stroke interval, its time constant should be greater than field-scanning period, and this is to realize circuit rapid-action key.Can not be luminous in level and vertical blanking period TV, tube cathode electric current during this occupies bigger ratio in reference signal, be that black-out intervals is reduced to zero tube cathode electric current the mean value of whole scan period will obviously be reduced, like this, because local brightness changes and may cause tube cathode electric current moment overload in the picture material, but its value shared deal in mean value is compared much smaller with blanking interval, if so do not get rid of the influence of blanking interval, then reference signal just can accurately the response diagram picture in the quick variation of local luminance, also just be difficult to the moment overload of tube cathode electric current is realized dynamically restriction fast.For this reason, the present invention digs up the reference signal of black-out intervals, replace greater than the field scan mean flow rate of forward stroke interval, the BCL end (beam electronic current control end) of delivering to video processing circuits with the reference signal after such processing goes to control the brightness and contrast of complete machine, thereby has realized dynamic ABL control.
Executive circuit in the described step 3 is a prior function circuit in the video signal processing ic, and the mode of its restriction tube cathode electric current is suitably to raise the tube cathode current potential or reduce the picture tube grid potential, thereby the tube cathode electric current is lowered.
The present invention is the dynamic auto restricting circuits of a kind of CRT beam electronic current; realize effective protection by two approach to picture tube in the CRT television set: the one, correctly select reference signal; the 2nd, reference signal is suitably handled; be included in the adjustable filter of setting-up time constant on its path; thereby can be, or reach several field-scanning periods freely with the reaction time of circuit or the magnitude of the line-scanning period of shortening to.
The dynamic auto restricting circuits of a kind of CRT beam electronic current comprises CRT, video processing circuits and final stage video amplifier circuit, it is characterized in that this circuit also comprises:
A tube cathode current sampling circuit is bound up in the tube cathode loop;
A commutation circuit that is used for the switching signal path, one input end connects sampled signal, and another input connects the output of a filter, and the input of another filter of output coupled is added with composite blanking signal on the control end.
Above-mentioned two filter time constants all can be adjusted, and one of them time constant is corresponding to the magnitude of line-scanning period, and another time constant is corresponding to the magnitude of field-scanning period.
The dynamic auto restricting circuits of described CRT beam electronic current, its tube cathode current sampling circuit is to be made of resistance, three negative electrode connect in parallel of one end and triniscope, other end ground connection.
The dynamic auto restricting circuits of described CRT beam electronic current is connected to a buffer on the output of its tube cathode current sampling circuit, the input of each filter all is connected to a buffer.
Described buffer is an emitter follower that is made of transistor and resistance.
The dynamic auto restricting circuits of described CRT beam electronic current, its commutation circuit can be controlled double-throw contactless electronic beam switch circuit.
The dynamic auto restricting circuits of described CRT beam electronic current, its filter is made of Resistor-Capacitor Unit.
Described filter time constant can be adjusted by the parameter that changes Resistor-Capacitor Unit.
As previously mentioned, the present invention can accelerate the reaction speed of ABL, accomplishes that moment starts to control, and can not have the reference signal of the cathode current of sluggish reflection image beams electric current as ABL; The black-out intervals that can remove in the reference signal is that part of to the fast reaction injurious effects; Thereby can the caused tube cathode electric current of excessive brightness moment overload local in the television image be limited, thereby can give sufficient protection to picture tube in time, how picture brightness changes all is unlikely to damage picture tube.
Description of drawings
The ABL schematic block circuit diagram that Fig. 1 is traditional.
Fig. 2 ABL schematic block circuit diagram of the present invention.
The enforcement circuit diagram of the dynamic ABL of Fig. 3.
Embodiment
Fig. 2 is a schematic block circuit diagram of the present invention, also promptly constitutes structural representation, and the present invention shown in the figure is by the dynamic auto restricting circuits of a kind of CRT beam electronic current, comprises existing C RT, video processing circuits and final stage video amplifier circuit, and this circuit also comprises:
A tube cathode current sampling circuit is bound up in the tube cathode loop;
A commutation circuit that is used for the switching signal path, one input end connects sampled signal, and another input connects the output of a filter, and the input of another filter of output coupled is added with composite blanking signal on the control end.
Above-mentioned two filter time constants all can be adjusted, and one of them time constant is corresponding to the line-scanning period, and another time constant is corresponding to field-scanning period;
Its tube cathode current sampling circuit is to be made of resistance, three negative electrode connect in parallel of one end and triniscope, other end ground connection; And being connected to a buffer on the output of its tube cathode current sampling circuit, the input of each filter all is connected to a buffer;
Commutation circuit can be a controlled double-throw contactless electronic beam switch circuit.
Above-mentioned buffer is an emitter follower that is made of transistor and resistance.
The dynamic auto restricting circuits of described CRT beam electronic current, its filter is made of Resistor-Capacitor Unit.
Fig. 3 is a practical circuit diagram of the present invention.In Fig. 3, sample resistance R1 is connected in the cathode return circuit of triniscope, three road cathode current Ikr/Ikg/Ikb are superimposed upon sample resistance R1 and go up formation original reference voltage signal, send into the input of commutation circuit U1 after isolating through the buffer of being made up of transistor Q4, resistance R 2, resistance R 3.Commutation circuit U1 in this example is an integrated electronically controlled switch circuit, and change action is subjected to the signal controlling on the Enable Pin.
Be added with composite blanking signal on the Enable Pin of commutation circuit U1, under its control,
During the scan(ing) stroke, just display image the time, commutation circuit U1 delivers to output with reference voltage signal, divide two-way to transmit again: the buffer that one tunnel process is made up of transistor Q3, resistance R 5, resistance R 4 is isolated, and the BCL that is sent to video processing circuits again after the low pass filter through resistance R 13, capacitor C 4 formation holds (beam electronic current control end); Another road isolates through another buffer of being made up of transistor Q2, resistance R 6, resistance R 7, deliver to the low pass filter that the time constant that is made of resistance R 10, capacitor C 1, resistance R 8, capacitor C 2 is slightly larger than 20ms, the reference voltage signal during the scan(ing) stroke is carried out smoothly;
The scanning black-out intervals, commutation circuit U1 is the switching signal path under the control of composite blanking signal, make aforesaid original reference voltage signal and output disconnect and be not output, the reference signal that the elapsed time constant is slightly larger than the level and smooth mistake of low pass filter of 20ms is delivered to output simultaneously, and the low pass filter that this signal forms through resistance R 13, capacitor C 4 again is sent to afterwards the BCL end of video processing circuits.
Filter above-mentioned, its time constant can be adjusted according to the needs that reality is used.In the present embodiment, elect about 400us as by the filter time constant that resistance R 13, capacitor C 4 constitute; By resistance R 10, capacitor C 1, resistance R 8, capacitor C 2 constitute the time constant of low pass filter be slightly larger than 20ms.
Obtain the authentic specimen of reference signal by correct selection sampling point, utilize composite blanking signal,, satisfactory finished task of the present invention again by the cooperating of commutation circuit and filter circuit as control signal.
Claims (10)
1, the method for the dynamic auto restriction of a kind of CRT beam electronic current, this method may further comprise the steps:
Step 1 is taken out the tube cathode electric current as the reference signal from final video amplifier;
Step 2 will be got rid of corresponding to the part of row, field scan black-out intervals in the reference signal, and the part of removing compensates with appropriate signals, and the part of promptly removing embeds with the mean value of the long-time tube cathode electric current of reference signal;
Obtaining of the mean value of the long-time tube cathode electric current of reference signal is to use filter that the reference signal of row, field scan forward stroke interval is smoothly realized; The filter that is used for the reference signal during the level and smooth line traversal, its time constant should be greater than the line-scanning periods, are used for the filter of the reference signal of level and smooth field scan forward stroke interval, and its time constant should be greater than field-scanning period,
Step 3 will be given executive circuit through the reference signal transmission of above-mentioned processing, at any time the tube cathode electric current be carried out flow restriction by executive circuit.
2, the method for the dynamic auto restriction of CRT beam electronic current as claimed in claim 1, it is characterized in that in the step 2, removing in the reference signal that part of corresponding to row, field scan black-out intervals, is realized by the video switch circuit of composite blanking signal control with one.
3, the method for the dynamic auto restriction of CRT beam electronic current as claimed in claim 1, it is characterized in that in the step 2, the part of removing is to adopt the mean value of the long-time tube cathode electric current of reference signal to embed with the appropriate signals compensation, and the embedding of this mean value is realized by the video switch circuit of composite blanking signal control with one.
4, the dynamic auto restricting circuits of a kind of CRT beam electronic current comprises CRT, video processing circuits and final stage video video amplifier circuit, it is characterized in that this circuit also comprises:
A tube cathode current sampling circuit is connected in the tube cathode loop;
A commutation circuit that is used for the switching signal path, one input end connects sampled signal, and another input connects the output of a filter, and the input of another filter of output coupled is added with composite blanking signal on the control end;
Final video amplifier takes out the tube cathode electric current as the reference signal, to get rid of corresponding to the part of row, field scan black-out intervals in the reference signal, the part of removing compensates with appropriate signals, the part of promptly removing embeds with the mean value of the long-time tube cathode electric current of reference signal, obtaining of the mean value of the long-time tube cathode electric current of reference signal is to use filter that the reference signal of row, field scan forward stroke interval is smoothly realized; The filter that is used for the reference signal during the level and smooth line traversal, its time constant should be greater than the line-scanning period, the filter that is used for the reference signal of level and smooth field scan forward stroke interval, its time constant should be greater than field-scanning period, to give executive circuit through the reference signal transmission of above-mentioned processing, at any time the tube cathode electric current be carried out flow restriction by executive circuit.
5, the dynamic auto restricting circuits of CRT beam electronic current as claimed in claim 4, it is characterized in that above-mentioned two filter time constants all can adjust, one of them time constant is corresponding to the magnitude of line-scanning period, and another time constant is corresponding to the magnitude of field-scanning period.
6, the dynamic auto restricting circuits of CRT beam electronic current as claimed in claim 4, it is characterized in that its tube cathode current sampling circuit is to be made of resistance, three cathode return circuit connect in parallel of one end and triniscope, other end ground connection allows three cathode currents all flow through sample resistance.
7, the dynamic auto restricting circuits of CRT beam electronic current as claimed in claim 4 is characterized in that being connected to a buffer on the output of its tube cathode current sampling circuit, and the input of each filter all is connected to a buffer.
8, the dynamic auto restricting circuits of CRT beam electronic current as claimed in claim 7 is characterized in that all buffers are emitter followers that is made of transistor and resistance.
9, the dynamic auto restricting circuits of CRT beam electronic current as claimed in claim 4 is characterized in that its commutation circuit is a controlled double-throw contactless electronic beam switch circuit.
10, the dynamic auto restricting circuits of CRT beam electronic current as claimed in claim 4 is characterized in that its filter is made of Resistor-Capacitor Unit, and filter time constant is to adjust by the parameter that changes Resistor-Capacitor Unit.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2005100330290A CN100479493C (en) | 2005-01-26 | 2005-01-26 | Automatic dynamic limiting method and circuit for CRT beam current |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2005100330290A CN100479493C (en) | 2005-01-26 | 2005-01-26 | Automatic dynamic limiting method and circuit for CRT beam current |
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| Publication Number | Publication Date |
|---|---|
| CN1812487A CN1812487A (en) | 2006-08-02 |
| CN100479493C true CN100479493C (en) | 2009-04-15 |
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| Application Number | Title | Priority Date | Filing Date |
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| CNB2005100330290A Expired - Fee Related CN100479493C (en) | 2005-01-26 | 2005-01-26 | Automatic dynamic limiting method and circuit for CRT beam current |
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4198661A (en) * | 1979-02-01 | 1980-04-15 | American Optical Corporation | Cathode ray tube burn-in prevention apparatus |
| GB2181028A (en) * | 1985-09-20 | 1987-04-08 | Secr Defence | Hybrid display system |
| CN1340842A (en) * | 2000-08-25 | 2002-03-20 | 三菱电机株式会社 | Cathode ray tube display device |
-
2005
- 2005-01-26 CN CNB2005100330290A patent/CN100479493C/en not_active Expired - Fee Related
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4198661A (en) * | 1979-02-01 | 1980-04-15 | American Optical Corporation | Cathode ray tube burn-in prevention apparatus |
| GB2181028A (en) * | 1985-09-20 | 1987-04-08 | Secr Defence | Hybrid display system |
| CN1340842A (en) * | 2000-08-25 | 2002-03-20 | 三菱电机株式会社 | Cathode ray tube display device |
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| Publication number | Publication date |
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| CN1812487A (en) | 2006-08-02 |
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Granted publication date: 20090415 Termination date: 20120126 |