DE2844112A1 - VIDEO SWITCHING WITH BURN-IN PROTECTION - Google Patents

Description

29-9-78 A- PHF 77572c

"Video circuit with burn-in protection."

The invention relates to a video circuit for generating video signals for playback of
.Images on a screen which video switching with
an image signal source, at least one luminance circuit coupled therewith for generating a luminance signal and with a protective circuit for protecting the screen from being burned in as a result of a static image of longer duration.

Vi de ο circuits of this axis are - when generating at least one Y-luminance signal and / or R-,

G and B luminance signals for displaying information in an information-processing arrangement in image form, which also includes teletext and view data systems, as well as the television games, which so-
called "video games".

The luminance signals can be appropriate
Inputs of a display device or modulated onto a carrier and fed to an antenna input of a television receiving device.

It often happens that a certain image remains static on the screen for a long time, so that lighter parts of the image can lead to an accelerated, local burn-in of the screen. Namely
it often happens that users forget to turn off a television game after using it, so that, for example,

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wise a line pattern of a playing field sometimes remains on the screen for a whole night. The video switching is provided with a protective circuit which tries to reduce this adverse effect.

A video circuit of the type mentioned in the opening paragraph is known from Canadian patent application No. 267th century. In this video circuit, the protection circuit contains a temperature-dependent element which has the effect that the image to be displayed is slowly moved over a small distance across the screen as a result of changes in the ambient temperature. However, it has been found that in rooms with thermostat-controlled heating, a temperature is set at the beginning of the night, which remains very constant afterwards, also because, for example, doors and windows remain closed for a long time, so that the picture during the the rest of the night can still remain in the same place on the screen for hours.

The invention now aims to provide a video circuit of the type mentioned in the opening paragraph, which allows burn-in of the screen at all costs. ■

A video circuit according to the Ex discovery has the indicator that the protective circuit with an electrical circuit breaker to completely or partially suppress the in the switched off state Video circuit generated luminance signal, with a Detection circuit for detecting. Changes in an electrical signal of the image signal source and with a timing circuit is provided, a detection output of the detection circuit having a start input the timing circuit is coupled, of which a time signal output with a control input of the circuit breaker in such a way is coupled that this is brought into the switched-off state after the detection circuit has not detected any signal change during a time determined by the timer.

In this way, surprisingly simple and inexpensive

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cheap ¥ ice achieved that when the rendering classification neither is new information supplied nor switched off after the leaching by the timer certain running time, the image density for all image points of the screen to zero or to one of these low mean value is reduced so that burn-in is completely or almost completely avoided.

Several embodiments are possible for the circuit breaker as well as the detection circuit and the timing circuit, as is described in claims 2 to 13 inclusive, which can also be used in many combinations. These embodiments are explained with reference to the figures and the description of the figures Jiahei ^1. Show it:

Pig · 1 is a simplified block diagram of a Video circuit with a circuit breaker to suppress a luminance signal,

Fig. 2 is a timing diagram of the main electrical Signals of the protection circuit, Fig. 3 is a simplified block diagram of a Video circuit with a circuit breaker to switch off a supply voltage,

H shows a block diagram for suppressing the luminance signal for a Schwai-z-Weiss display arrangement,

Figure 5 is a timing diagram for a Pig video circuit. H,

6 shows a detailed partial circuit of a further embodiment with suppression of the luminance signal for a black and white display,

7 shows a schematic example of the use of a touch contact in a video circuit according to FIG. K or FIG. 6,

Figure 8 shows another embodiment of a video circuit according to the invention.

9 is a wiring diagram for a detection circuit with integration elements,

Fig. 10 to 13 four embodiments of video

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circuits with a protective circuit for use in color display devices,

FIG. ] H shows a time diagram belonging to the embodiment according to FIG. 13,

15 is a circuit diagram of a simple detection circuit,

16 shows a simplified block diagram of a timing circuit formed with a digital counter circuit.

In Fig..1 an operating arrangement 1 is coupled to an image signal source 2. The operating arrangement 1 usually contains one or more operating elements known per se, such as pushbuttons, touch keys, switches or rotary potentiometers, which the latter are sometimes operated by a so-called "joy stick". The image signal source 2 is used to build up the complete image information for the selected destination. The image information controls at least one luminance circuit 3 coupled to the image signal source 2 for supplying a luminance signal to the display device k.

There are generally three for color reproduction Luminance circuits 3 used for the so-called R, G and B luminance signals.

The coupling between the operating arrangement and the image signal source 2 can, if desired, be via a remote control channel with signal transmission, for example by means of IR radiation.

At least one signal from the image signal source 2 is fed to the detection circuit 5 with a detection output b for an electrical detection signal. This detection signal is impiilsförmig and occurs after a change of ± n which the image signal source 2 taken signal on which signal one of Bildslgiialquelle may be taken 2 supplied operation signal or a therefrom resulting from processing in the image signal source 2 new signal. It is of course possible to supply two or more signals to the detection circuit and to generate a detection signal as soon as

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at least one of these has a change. Jn Examples are given in FIGS. 4 and so on. The output 6 of the detection circuit 5 has an input 7 of a timing circuit 8 coupled to a time signal output 9. The timing circuit 8 is known per se Component such as a monovibrator circuit or a digital one Counter circuit. The timing circuit 8 is set to an initial position by a detection signal at the input 7, the "0" position brought. As long as there is no new detection signal is given, the timing circuit works by, for example, a capacitor voltage monotonically in the time runs up and after a period of time determined by the components causes the monovibrator to tip over or in that, controlled by a clock signal, the counter setting up to a selected maximum counter setting increases. At the end of the selected time, the timer sends an OTC output signal to .Axis output 9. If any a new detection signal appears before the selected time has expired, the timer is switched to again the "0" position must be observed. The time constant of the timer is chosen to be significantly longer than the time that, with normal use of the system, between information changes, occurs, for example, on the order of a minute or more. As soon as the situation that arises during a longer time than the chosen one Time there is no change in the image information, the signal OTG will be generated.

The output 9 of the timing circuit 8 is coupled to an input 10 of a protection circuit 11, in this Example directly with the luminance circuit 3 · The Protection circuit 11 is set up such that this completely or partially suppress the luminance signal ^ as soon as the timer reaches the maximum position has and remains in this position until a restart is given. Aiif this way will avoid that one The screen in the display device 4 burns in by the fact that a still picture from a computer system, a teletext system, a television game or the like

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Non-use, for example, bark boundary lines still on a fixed part of the screen with high Intensity. Precisely because other parts of the screen cannot be burned in, they are actually quite wrong Differences in intensity later have a visually disturbing effect.

The course of events is shown in the timing diagram of FIG. Line 20 therein shows the pulses of the detection signal and line 21 shows a characteristic variable of the timing circuit, for example increasing linearly from "0" to a maximum value "max". If a detection signal occurs at time t, the switch is brought into the "0" position and this takes place again at time t ₁ , etc. without the “max” position being reached. Only when nothing has happened for a long time does this timer reach the “max” position at time t and remains in this position until, for example, time t. a new detection signal appears. The line 22 shows the output signal OTC of the timer circuit, here arbitrarily represented as "ON" or "1" in the normal state and "OFF" - starting in the "max" position. The output signal OTC brings the contactor circuit into the "OFF" position, as curve 23 shows, which ultimately ^{results in the luminance signal Y for black Tv r} eiss'- ¥ ¥ iedergabe, denoted by curve 2h, between t and t. is completely or largely suppressed.

Fig. 3 shows a further embodiment. In In this and in the following figures, the same reference symbols are always used for corresponding elements.

The elements 1, 2, 3> ^> 5 and 8 have the same Task as in Fig. 1.,

In the figure, a supply arrangement 12, for example a battery, is now included, which the remaining parts of the video circuit with a supply voltage provides and through a normally conductive transistor I3, the base of which the input 10 of the Achutz circuit forms. As long as the OTC signal at the output

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. 9 of the timer circuit 8 is "ON", the transistor I3 is conductive and the video circuit is supplied with voltage Mistake. If the signal OTC is, for example, at time t. "OFF", the transistor I3 blocks the supply voltage, so that of course OTC will now remain "OFF". The timer 8 now does not need any holding • function. Although it is sufficient to only block the supply voltage of the Zeitschaltxjng 8, it can be desirable to cut off all tension. This is useful for battery power supply to extend the service life of the battery to extend. Another advantage arises when using a television reception arrangement as the type of arrangement 4 when the luminance signal is modulated onto a carrier and fed to an antenna input 14 of the receiver will. When the supply voltage drops out, so does the carrier, which means that most receivers fall too start rushing and at this catfish the user aurally to warn. Another possibility is for receivers with a so-called "standby" switch, this switch to bring ter into readiness position as soon as the There is no supply voltage.

The circuit arrangement of the transistor 13 is in Fig. 3 indicated only in a schematic manner. Designing a suitable circuit is beyond the scope of the Invention and belongs to the competence of the normal expert.

If, in addition to the timing circuit 8, other parts, such as the image signal source 2 or the detection circuit 5 are switched off, a new operating signal is given do not cause an automatic restart. With the help of a switch 15? less than included in the operating instructions 1 thought, the transistor can briefly be brought into the conductive state. The switch I5 can, for example be designed as a push button or as a second contact on an existing one for other reasons Control element.

Fig. K shows in a schematic manner a video circuit 20 with an image signal source and a light

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density circuit as block 21, a synchronization signal circuit 22 and a mixer circuit 23 with an output 2h for a video signal modulated on a carrier. Except for the video circuit. 20, two operating arrangements 30 »31 are coupled to the operating inputs of the image signal source 21 and at the same time to two detection circuits "} 2 , 33 ^for detecting an operating action. Outputs of the same are coupled to corresponding inputs 34, 35 of an OR gate 36 from which

ΊΟ an output 37 with an input 38 of a timer 8 is coupled to a time signal output 9. The luminance signal at the output 40 of the luminance circuit in 21 is fed to the mixing circuit 23 via an AND gate 42, as long as the OTC signal at output 9 of the timer Is "ON". In the event that a. Detection signal after a restart not immediately to a Luminance signal leads due to the flyback time a monovibrator with a long time constant, the detection signal is if desired via an OR gate 43 supplied to AND gate 42. The OR gate 43 is, however not essential; it is also possible to connect the output 9 of the timing circuit 8 directly to an input of the AND gate 42 to connect. It should be evident that the AND gate 42 blocks the luminance signal as soon as the OTC time signal becomes "OFF".

5 ^a to 5 b inclusive show a simplified timing diagram for the synchronizing signal (5 a), the image information signal (5 b), which together as a video signal (5 g) can be modulated onto a carrier by the modulation circuit 23.

Fig. 5c shows the end of a detection signal at a point in time t and FIG. 5d shows the course of the Signala.ls OTC, which becomes "OFF" after a long time. This is urgent shown, in reality there are many sync pulses between t and tp. Until the point in time t “will the information signal supplied to the modulator 23, from the AND gate 42 blocks the information signal at the time t "an so that the modulator 23 only the synchronous

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signal gets fed and the picture on the display screen now getting dark.

It may be desirable that the image is not completely subdivided, but onto an image with a harmless luminance level is limited «It turned out that a luminance level from about 50? o of the maximum luminance level none noticeable burn-in appears.

An embodiment with a luminance limitation is shown in FIG. 6. An example of a mixer circuit 23 with resistors 50, 51, 52 is to symbolic Way indicated, while the carrier modulation is not entered for the sake of clarity. The modulator 23 works in a manner known per se.

The AND gate 42 is in this embodiment has been replaced by a protection circuit 53, which consists of a series circuit of a resistor 54, a adjustable resistor 55 or a diode 56 is formed .is, .whose anode with the adjustable resistor 55 and the · cathode with the output of the OR gate 43 or directly is connected to the output 9 of the timing circuit 8. '■ Based on the use of a positive supply voltage in the video circuit, the cathode is the Diode normally at a positive voltage when OTC is "ON", thereby blocking diode 56 «The luminance signal ■ is connected to the modulator via the resistor 54 23 supplied. ·

As soon as OTC is "OFF", the diode 56 can conduct and the luminance signal is attenuated by the additional load that is created by the series connection 55> 56. It is also possible ^{to combine the resistors 54, 55 for} an adjustable resistance potentiometer,

An output 6O of the video switch is shown in fig.

4 and 6 are connected to the output of the OR gate 43. In the case where the video circuit as a whole is in is built into a television receiving arrangement, can

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Output signal of the OR gate 43. Can be used to to switch the receiving arrangement to television reception. If the OR gate 43 is not used, the output 60 can be coupled to the output 9 of the timing circuit 8 will.

7 shows in a schematic manner that a detection circuit 71 for an operating arrangement 30 can consist of a touch contact whose voltage change generated when the operating arrangement is touched is fed to the timer.

Fig. 8 shows a somewhat different arrangement of the elements. Two detection circuits 74 and 75 are now included in the video circuit, with the inputs 76 or 77 with the outputs of the corresponding operating instructions 30 and 31 are coupled, while the Outputs 78, 79 with inputs 35 and 34 of the OR gate 37 are connected.

Pig. 9 shows a possible embodiment of the detection circuit 74, 75 * each of these detection circuits is on the input side (76 or 77) with an impedance matching 121a, b with two pairs below Comparison circuits 122a, 123a and 122b, 123b provided, the four outputs of which are connected to four corresponding inputs of the OR gate 36.

The entrances of each pair are opposite Polarity of the two comparison circuits connected to one another, one of these connections 128a, b is coupled to the output of the matching circuit 121a, b via an RC element 124a, b and 125a, b, and the other 129a, b via an additional RC element 126a, b and 127a, b, with the total time delay between 121 and 129 is therefore larger than that between 121 and 128.

As soon as the input signal changes, for example at input 76 of detection circuit 74, either comparison circuit 122a or 123a Cause "ON" going output signal and thereby the Output 37 of OR gate 36 temporarily "ON".

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If there is no operation, all inputs are of the comparison circuits assume the same voltage level and the output voltage of the OR gate becomes equal to "0".

"If the time constant of the RC elements 126, 127 chosen large enough j i.e. in the order of magnitude accordingly one minute or longer, they also fulfill the task of the timer circuit 8, so that the output 37 of the OR gate 36 directly to the OR gate 43 or the AND gate 42 can be connected.

FIGS. 10, 11 and 12 show embodiments for color reproduction, which incidentally the circuit arrangements completely correspond to Fig. 4, Fig. 8 and Fig. 6,

Now there are always three circuit breakers 42a, b, c * or circuit ^{arrangements 53 a} >> ^c between the image signal source and the luminance circuit 200 with three outputs for R, G and B and a modulation circuit 400, for example PAL system or the SECAM system added, which is further coupled to a synchronization signal circuit 300. An output 100 of the modulation circuit 400 can be coupled to an antenna input of a television receiving arrangement. Of course, the modulation circuit 400 can be omitted if the television reception arrangement has individual video inputs R, G and B and SYNC, as is often the case at the moment, for connecting a video recorder, among other things.

A very simple solution for color reproduction is shown in Fig. 13. The circuit breaker is here by three EXELUSIVE-OR gates 110, 111 and 112 with exits 113, 114 and 115, which provide the R, G and B signals, and a NOR gate 116 is formed. For simple video switching becomes the color information with three one-bit signals SR, SG and SB given so that eight colors are determined with the respective "0" and "1" combinations, including white and black. These one-bit signals are first inputs 120, 121, 122 of the EXCLUSIVE-OR

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Gates 110, 111 and 112, the second inputs 130, 131, 132 of which are connected together with the output 133 of the NOR gate 116. As long as this output is "0", R, G and B correspond to the values SR, Sg and SB, respectively. The OTC signal and a clock signal are fed to the inputs of the NOR gate 116. As long as OTC is "ON", with normal use, output 133 of NOR gate II6 is "OFF". However, when OTC becomes "OFF", 116 follows the clock signal CLK and thereby becomes "ON" and "OFF" alternately at the clock of CLK. Whenever the output 133 is "ON", the combination R, G and B is now the inverse of the combination SR, SG or SB, 000 is replaced by 111, 011 by 100, etc., so that the alternating with SR, SG and SB specified hue or an identical complementary hue is passed on via R, G and B. If one or more of the color signals is "1", the result becomes "0" and "1" alternately, so that each of the color signals has an average luminance corresponding to 50 ° /> the maximum luminance.

This is shown, for example, for R in the time diagram from FIG. Ik on the same time axis as that from FIG. 2.

Until the instant t, R remains identical to a multi-bit signal SR for the sake of clarity, with now all bits of the three color luminance signals can be switched in due to OTC = "0". After t, or already earlier, SR no longer changes and remains on one in this example when OTC = "0" appears high amplitude a maintained. In the cycle of CLK, all bits are periodically and simultaneously inverted, so that periodically R now assumes ¥ ert ("max" - a), on average - "max" f, which follows from the following :

a + ("m ax" - a)
2

The same happens with other shades. That the pattern ultimately obtained remains visible on the screen but with a greatly reduced average

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luminance.

The clock frequency can be freely selected within wide limits. Examples are the use of a Selecund signal of a clock in the device, a 50 Hz pulse voltage derived from the mains frequency and like

For use in a television game, Fig. 15 shows a very simple and inexpensive but nevertheless effective detection circuit. To detect the change the position of an adjustable resistance potentiometer, whose wiper I5I with an input 152 is coupled to the image signal source, the grinder at the same time with an RC differentiating network 153> 15 ^ connected. The differentiated signal becomes one Pulse shaper 155 supplied, for example an OR gate, an AND gate with connected AND inputs or an inverter. This delivers when the Grinder a "1" pulse in the first two Pulse shaper examples when the voltage taken from the resistance potentiometer increases and in the example of the itiverting pulse shaper if this voltage drops. Werni the video circuit for a television game for two Player is determined, this detection pulse can be combined with the one from one for the Opponent specific resistance potentiometer is derived by combining the two signals with an OR gate 156 until the detection signal DET, via the output I57 of this gate of the timer 8 is fed.

Since in some games only one player plays, such as the card game, everyone has to play If the potentiometer then used can be connected. Since even with two players, one player has several Times per minute the own potentiometer in alternating Directions is actuated, the second does not generally need necessarily with a detection circuit to be provided.

The OR gate I56 can be omitted in this case

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or, for example, another actuating element ztim to switch can be used like a touch contact to an additional input I58.

Finally, Fig. 16 shows a simple timing circuit, those with a digital counter circuit I60 with a counter input I6I, an enable input 162 (count enable), a reset input 163 and a Counter output 164 is formed.

The counter input Ιοί can be matched with a Clock signal, as it was called in Fig. I3 of, for example, 1 Hz, are connected.

The Ruckste11eingang 163 is with the detection output 6 connected to the detection circuit 5, so that the counter circuit in the "0" position is brought to then counting in time. If there are no new detection signals, this is achieved the counter circuit at the end the maximum position which is given by decoding the counter bits. This can, for example, be the highest position indicated by the "OFF" carry signal (transmission signal) is given to the counter output 164. With a clock frequency of 1 Hz and a 6-bit counter, this position becomes reached after about 1 minute if no subsequent detection signals DET appear.

To avoid that the counter continues to count to "000000" after "111111" at the CLK, the output i6k is connected to the "count-enable" input 162 so that the counter stops; as soon as CA and thus CE "OFF" will. However, as soon as a DET signal appears again, the counter will probably be reset. Several known digital counter circuits can be used as the counter circuit, for example a Signetics type 54161, or two or more examples connected in cascade if more than k bits are desired. The output signal CA at the counter output 164 is at the same time the time signal OTC.

If the transistor I3 from FIG. 3 is emitter-side is coupled to the feed unit 12, the

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Base of this transistor controlled with an inverter circuit that consist of a switching transistor I65 with a collector resistor I66, one end of which 167 is connected to the base of the transistor 13. As soon OTC is "OFF", transistor I3 no longer receives base current and blocks. Usually, however, OTC is "ON", • the transistor I65 conducts and the transistor I3 receives a base current, which is essentially determined by the size of resistance is determined.

In this example, a restart is possible because transistor I65 has a restart contact 168 is bridged.

It should be evident that the examples given are only given to explain the concept of the invention and are not bound to the chosen form; many modifications are within the scope of the invention possible. There are also many combinations of the respective detection circuits, timers and circuit breakers possible.

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Claims (1)

29.9-78 -f PHF 77572c PATEKTAHSl'RÜCHB: Video circuit for generating video signals, for displaying images on a screen, which Video circuit with an image signal source, at least a luminance oscbaltxing coupled with it for the purpose of δ testify to a luminance signal and with. a protection circuit for skiing. of the screen before burn-in due to a static image of longer duration is, characterized in that the protective circuit is switched off with an electrical circuit breaker State of total or partial suppression of the luminance signal generated in the video circuit, with a detection circuit to detect aeration in an electrical signal of the image signal source, and is provided with a tent circuit, wherein a detection output of the detection circuit with is coupled to a start input of the timing circuit, of which a time signal control input to the control input of the Circuit breaker is coupled in such a way that it is brought into the switched-off state after 2D the detection circuit during one through the timing circuit no signal change for a certain time, · detected Has. 2. Video circuit according to claim 1, characterized in that that the circuit breaker is in a feeder between an electrical feed and a 909816 / 088S 29.9-78 £ PHF 77572C Food input of the leuclite density circuit added is * 3. Video circuit according to claim 2, characterized in that a feed input of the timing circuit is connected to the feed input of the luminance circuit and that the video circuit is provided with a restart circuit for switching on the protection switch again.
k. Vide ο circuit according to claim 1, characterized in that the circuit breaker ^{1 is} connected in series with the luminance circuit for partial or complete suppression of the luminance signal when it is switched off, 5, video circuit according to claim 1, for reproducing color images with R, G and B luminance signals of corresponding luminance circuits , characterized in that the circuit breaker contains R, G and B sub-switches that generate the corresponding luminance signals when the circuit breaker is switched on 2C "essential original changed forward and in a switched off State of the circuit breaker the corresponding luminance signals between through the luminance circuits given amplitudes and the same complementary amplitudes switch periodically, with a complementary amplitude of the difference between, the maximum and corresponds to the given amplitude. 6. video circuit according to claim 5? with digital R, G and B light emitting circuits for generating Luminance signals with at least one one-bit output per color tone, characterized in that the Schut2: - switch the bit outputs when switched off periodically inverted. 7 · video circuit according to claim 1 with a Carrier oscillator and a modulation circuit for supplying a video signal that is inodulated onto a carrier to a response to a television reception arrangement, characterized in that the circuit breaker is connected to the carrier oscillator for suppressing the carrier iin. 909816 / 088S 29.9-78 3 PIIF 77372C 28AA112 switch. State is connected in series. 8. Video circuit according to one of the preceding claims with a carrier oscillator, a modulation circuit, an auxiliary antenna input and an antenna S Changeover switch for feeding a modulated onto a carrier Video signal to an antenna input of a television reception arrangement, which anti-gluing switch in a first Switching status of the shares input with an output of the Modulation circuit couples and in a second stop state with the auxiliary antenna input, characterized that the antenna switch is coupled to the circuit breaker, which is in a switched-on state Brings the anti-pollution switch to the first switching state and the antenna switch in a switched-off state brings into the second switching state. 9. Video circuit according to one of the preceding claims dadui "ch marked that the image signal source is provided with at least one control input for an electrical control signal, which control input with a Signal input of the detection circuit for detection is coupled to changes in the control signal " 10. Video circuit according to claim 9j with at least a touch contact for generating an electrical control signal, characterized in that a control signal output of the touch contact with the signal input is coupled to the detection circuit. 11. Video switching according to one of the preceding Claims to have at least one adjustable resistance potentiometer Generating an adjustable analog control signal at a potentiometer output; characterized, that the potentiometer is capacitively coupled to a signal input of the detection circuit is. 12. Vide ο circuit after one of the pre-dividing Claims, characterized in that the time switch is formed with a restartable monovibrator circuit.
13 · Video circuit according to one of Claims 1 to 909816/08 29 x 9 x 78 4 ApHF 77572C 11, thereby gekeniizeiclinet · that the time circuit with a digital counter circuit is formed with is provided with a reverse input, which allows the start input output of the timing circuit and with a final position output, which forms the time signal output of the timer. 14. TV game with a video circuit after one of the preceding claims. 909816/0888