KR820002266B1 - Combined kinescope grid and cathode video drive system - Google Patents

Abstract

Reproducing kinescope with plural cathode electrodes and a common grid electrode, a kinescope driver amplifier arrangement is disclosed for supplying frequency selective video signal drive to the kinescope. The receiver also includes networks for providing wide bandwidth luminance (Y) and plural color (r, g,b) image representative signals containing low and high frequency components, as derived from a composite color television signal. High frequency components composite color television signal. High frequency componets (e.g., drived from the luminance signal) above a prescribed frequency are selectively processed in a grid signal path.

Description

Video tube drive amplifier

1 is a partial block diagram of a color television receiver including an image tube driving device according to the present invention.

2 to 6 are signal waveform diagrams used for explaining the operation of the apparatus of FIG.

7 is a detailed view of another circuit constructed by the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an economical low power type image tube drive amplifier suitable for supplying an amplified image signal to an image reproduction image tube such as a color television receiver.

In the case of a typical color television receiver, three image tube driving stages are generally used to supply a wide band high level red, green, and blue image display signals including low frequency and high frequency components to respective control electrodes of the color image tube. The same drive stage consumes a considerable amount of power (e.g. 6 watts for each amplification stage) when each class A amplifier is used to amplify a wideband video signal.

Therefore, the use of complementary or quasi-complementary drive amplifiers requiring two high voltage transistors results in relatively low power consumption. However, although the complementary amplifier has the advantage of lower power consumption and a wider signal processing band than the Class A amplifier, the complementary driving amplification method requires six high-voltage transistors as a whole and easily responds to a short circuit caused by discharge of the image tube. Not only that, but it also leads to undesirable differential signal rise time error. This error appears as a difference in the high frequency amplitude response between the drive stages and is associated with rapid signal amplitude transitions (e.g. color shifts) and high frequency bursts, especially when the drive stages are configured to exhibit different operating points.

According to the principles of the present invention, the imaging tube drive amplifier described below requires only the smallest number of high power consumption transistors, has low sensitivity to short circuits due to discharge of the imaging tube, has a very high frequency differential rise time error, and has a broadband performance. And low power consumption performance.

The video tube drive amplification apparatus according to the present invention is included in a method of processing color image display video signals including low frequency and high frequency components, the method comprising an image signal applied to a control electrode with first and second intensity control electrodes. It has a video tube including an electron gun structure for reproducing an image in response. The high frequency component over a predetermined frequency of the video signal is sent to the first amplifier and amplified therein so that the selected high frequency component is supplied to the first electrode of the video tube.

The color display video signal including the selected high frequency component, low frequency and high frequency component is synthesized in a synthesis network, so that the high frequency component of the video signal is greatly attenuated at its output. The second amplifier supplies the output signal from the synthesis network to the second image tube electrode.

According to a feature of the invention, a gain adjustment circuit is provided for adjusting the amplitude of the color signal synthesized by the synthesis circuit, which is adjusted to the position where the amplitude-adjusted color signal is generated at the input of the circuit. The high frequency components selected at the output of the network can be canceled out.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

In FIG. 1, the video signal source 10 including the luminance signal and the chrominance signal processing network supplies the wideband luminance signal y and the color difference signals r-y, g-y, and b-y including high frequency image signal information. The luminance signal from signal source 10 is filtered by high pass filter 12 to remove low frequency signal components below a predetermined cutoff frequency fo as will be described later.

The high frequency component selectively passed through the filter 12 is amplified by the grid preamplifier stage 14 and the grid amplifier stage 16 so that the grid drive output signal from the amplifier stage 16 is a color image tube 20. Is applied to the control grid electrode 18. In this example, the image tube 20 corresponds to a self-concentrating in-line image tube with grid electrodes 18 common to all of the image tube electron guns having cathodes 22, 23, and 24, respectively. do.

The luminance signal and the chrominance signal from the signal source 10 are synthesized in a demodulation matrix and include r, g, b containing high frequency luminance signal information and low frequency luminance signal information related to the luminance output signal from the signal source 10. Generates a color image display signal of. This color signal is converted into amplified color signals r _c , g _c , and b _c by the red, green, and blue color signal processing devices 34, 36, and 38, respectively, and the cathodes of the image tube 20 respectively. Supplied to (22), (23), and (24). The signal processing devices 34, 26, 38 also receive input high frequency signals drawn from the grid drive signal e _g of the output of the amplifier stage 16. Since the signal processing apparatuses 34, 36 and 38 have the same structure in this example, the following description of the operation of the red signal processing apparatus 34 will be described with the green and blue signal processing apparatuses 36 and 38. Also applies.

In the red signal processing device 34, the peak to peak amplitude of the red signal from the demodulation matrix 30 is adjusted by the gain control device 40. This adjusting device 40 corresponds to a " back balance " adjusting device which makes an adjustment for compensating for the difference in efficiency of the image tube phosphor during adjustment of the image tube in the repair state of the receiver. The output signal r ₁ from the regulating device 40 is supplied to the first input of the signal synthesizing network 41. In addition, the second input of the synthesis network 41 is supplied with the high frequency compensation signal e _c extracted from the high frequency signal e _g through the compensation network 44.

The compensating circuit 44 has a suitable signal conversion and inversion circuit such that the output signal e _c corresponds to the complementary phase type of the high frequency grid signal e _g . The high frequency signal component r ₁ common to the grid signal e _g and the color signal r is canceled in whole or a substantial part by the signal subtraction process when the complementary signals r ₁ and e _c are combined in the apparatus 41, as will be described later. Likewise, the signal may be completely canceled out when the gain control device 40 is adjusted such that the synthesized signals r ₁ and e _c are equal. The output signal r ₂ of the network 41 is again amplified by the signal inversion amplifier 48 to generate the red signal r _c which drives the red cathode 22 of the image tube 20.

By setting the gain of the adjusting device 40, all or a substantial portion of the high frequency component of the signal r is canceled by the compensation signal e _c . In the former case, the low frequency video signal component of the signal r ₂ is substantially below the frequency f _c. In the latter case, a low frequency component and a small amount of residual high frequency components are used. Thus, the cathode signal amplifier 48 does not need to be operated in response to a high amplitude signal of large amplitude. As such, the amplifier 48 may be, for example, a low current class A amplifier capable of exhibiting relatively limited output rotation while maintaining a bandwidth of 5 MHz for a small signal. This bandwidth is obtained for a suitable RC frequency compensation network as described for the circuit of FIG.

The result of the above-described signal cancellation process is shown by the amplitude normalization signal waveforms of FIGS. The description of these waveforms is given for the red cathode signal, which is also applicable to the green and blue cathode signals.

In FIG. 2 the signal r ₁ is shown for various set gains of the gain control device 40, which includes a low frequency pulse and a high frequency (5 MHz) signal burst, the latter of which extends one cycle in time. Subtracted signal cancellation processing of high frequency signal components is specified.

The signal e _c in FIG. 3 contains only a high frequency component by the filter action of the filter 12. The amplitude of the signal e ₂ is not affected by the adjustment of the gain regulator 40 and in this case is symmetrical with respect to the (0) volts of the DC reference level.

5 shows the signal r ₂ when the gain adjusting device 40 is set to intermediate gain. This setting obtains the normalized signal amplitude of 0.833 when the normalized signal amplitude is set to (100) with the setting as the maximum gain.

In this state, the high frequency components of the signals e _c and r ₁ are equal to each other (normalized amplitude 0.833) and cancel each other when synthesized by the combining device 41.

The synthesized signals e _c and r ₁ differ in the high frequency component amplitude when the synthesizer 40 is set to the gain maximum (normalized amplitude 1,00) and when the gain minimum (normalized amplitude 0.66) is set. For this reason, 0.16 (0.66-0.833) normalized amplitude and some unerased residual high frequency components of one phase appear in the signal r ₂ at the maximum gain setting as shown in FIG. In addition, when some of the micro-going residual high-frequency component of 0.16 (0.66 to 0.833) a normalized amplitude even at the minimum gain setting during the signal r ₂ as shown in Figure 6. The phase of this residual component is opposite to the phase of the residual component produced when the regulator 40 is set to maximum gain. This type of signal is suitable for low current dynamic biased A pole amplifiers.

In the normalized amplitude gain adjustment range of 0.66 to 1.00, which is sometimes necessary in the case of an inline type image tube, the residual high frequency component does not exceed 60% of the maximum amplitude of the low frequency component.

The separation of the low frequency component and the high frequency component of the video tube drive signal by the above-described signal cancellation method has several advantages over other signal separation methods using, for example, a high frequency filter or a low frequency filter.

Even if the signal processing gains of red, blue, and green are adjusted only in the cathode signal processing path, close tracking is obtained between the high frequency signal gain and the low frequency signal gain. For example, considering the signal processing path including the device 34 (1), the image tube drive signal (r _c- e _g ), which determines the beam current of the enemy electron gun, is proportional to the direct input red signal level r, as shown in the following equation. do.

r _c -e _g = rA ₄₀ A ₄₈

The gain A ₄₀ given by the gain adjuster 48 and the gain A ₄₈ associated with the amplifier ₄₈ alone determine the signal gain to present for the red signal processing path. The above equation can mathematically indicate that the gain of the compensator 44 is satisfied when 1 / A48. This condition holds, and as described above, the high frequency signal is canceled in whole or in substantial part in the r signal processing passage, and the appropriate high frequency video signal driving signal is passed through the filter 12 and the amplifier 16 to the grid 18 of the image tube. Is applied.

The image tube drive signal r _c -e _g is an amplified copy of the input signal r for all gain settings of the gain control device 40 when the gain of the compensation signal path including the device 44 is set as described above. For example, the gain adjusting device 40 is set to the minimum gain position to attenuate the red cathode signal (FIG. 6). Since the residual high frequency component of the r cathode signal has a direction opposite to the high frequency grid signal by an amount corresponding to its magnitude, the gain of the grid signal is effectively attenuated. In particular, the magnitude and polarity of the residual high frequency component (after it is drawn out of the output of the assembly device 41 and inverted by the inverting amplifier 48) opposes the added tube current in response to the applied high frequency grid and cathode signals. The grid of the image tube and the cathode receive in this case high frequency signals of the same polarity. The magnitude and polarity of the residual high frequency components generated in the maximum gain setting of the controller 40 thus induces the image tube current conduction to be added in response to the applied grid signal and the cathode signal. The grid and cathode of this image tube receive high frequency signals of opposite polarity in this case. When the gain control device 40 is adjusted in the cathode signal path as described above, a high frequency signal to the video tube is received. When the gain control device 40 is adjusted in the negative signal path as described above, the high frequency signal driving to the image tube is tracked along with the low frequency signal driving.

As described above, the image tube drive signal that determines the beam current of the enemy gun is its amplified copy directly proportional to the red signal r. Therefore, there is no net modulation by the high frequency signal from the grid amplifier stage 16 of the electron gun, including the lead 18 and the cathode 22.

This effect can be understood assuming that the red signal r once disappears as follows. The high frequency signal applied to the grid 18 in a normal phase is inverted in phase by the compensating network 44 and appears at the output of the synthesizing device 41 and again inverted by the amplifier 48.

The high frequency signal from the amplifier 48 is then applied to the cathode 22 and is in phase with the signal applied to the grid 18. This grid signal and the cathode signal have the same amplitude as determined by the gain relationship between the device 44 and the amplifier 48 described above. Therefore, these high frequency grids and cathode signals with the same amplitude and polarity do not cause net high frequency modulation in the electron gun of the image tube.

The signal having a frequency falling on the gradient phase of the signal transmission characteristic of the filter 12 (that is, near the cutoff frequency fc) is partially attenuated by the filter 12, but in the r signal processing furnace, the partial cancellation of the signal of the frequency is thus performed. Since only the grid 16 and the adaptive pole 22 of the image tube 20 is driven at this signal frequency. The video signal frequency, which is much lower than the toothing frequency fc, is attenuated by the filter 12 so that the grid 18 of the picture tube does not actually receive any video signal in the signal frequency range below the frequency fc.

It can be seen that the frequency separation of the video signal obtained by the above-described signal subtraction process also automatically provides the proper separation of the video signal between the cathode and the grid of the video tube regardless of the operating characteristics or the cutoff frequency of the high pass filter 12. Can be.

The cutoff frequency of the high frequency filter 12 can be selected, for example, within the range of 200 to 1 MHz. When the cutoff frequency is made substantially equal to or less than 1 MHz, a signal frequency of 1 MHz or more common to the three primary signals r, g, and b is finally amplified by the amplifier 48 of the processing device 34. It is certainly substantially erased. When the cutoff frequency is substantially equal to or higher than 200 Hz, the direct current component of the video signal does not appear in the grid signal amplifier stage and the grid 18 of the video tube. Also, as in this example, when the signal from the signal source 10 corresponds to the luminance component Y of the video signal, the signal cancellation processing contributes to the generation of the color difference signals rY, gY, bY in the cathode signal processing passage. I never do that. The color difference signal of the negative signal amplifier (for example, the input of the amplifier 48) is not suitable because the amplitude is generally larger than the primary color signals r, g, and b.

In the description a first degree, a signal e _g and the relative phase of r _i is during when the signal e _c, and r synthesized in the unit 41 a signal having a high frequency component of the complementary phase relationship such that the high-frequency component is offset by e _c and r _It is assumed that a phase inversion of the signal e _g by the inverter in the network 44 is required so that ₁ is generated, but the grid signal from the output of the preamplifier 14 is in phase with respect to the signal r ₁ . In this case, instead of using the inverter in the network 44 to cancel the high frequency signal required in the network 41, the network (from the output of the preamplifier 14 instead of the output of the amplifier stage 16). Through 44), the compensation signal e _c can be extracted. In this case, when the signal gain indicated by the compensation signal path including the network 44 is A ₁₆ / A ₄₈ , the high frequency signal is erased in the network 41. Where A ₁₆ and A ₄₈ are the signal gains of the amplifiers 16 and 48 respectively. Due to this gain relationship, the image tube drive signal r _c -e _g may be an amplified copy of the input signal (e.g., signal r) as described with reference to FIG.

FIG. 7 shows another embodiment of the circuit main part of FIG. 1, in which corresponding elements are denoted by the same reference numerals. Since the red, green, and blue cathode signal processing networks 34, 36, and 38 have the same configuration, only the red signal processing network is shown in FIG. 7 as a circuit diagram.

In FIG. 7, the inverted amplifier stage including the transistor 55 corresponds to the preamplifier 14 of FIG. Along with the input impedance of this amplifier stage 14, the capacitor 58 corresponds to the high filter 12 of FIG. The high pass filter including the condenser 58 corresponds to the first-order high pass filter having a cutoff frequency of fc = 285K, but other types of high pass filters having different cutoff frequencies may be used.

The non-rescue ackinner follower transistor 60 whose base input is connected to the collector output of the transistor 55 drives the grid signal amplifier stage 16 including the high voltage signal inversion amplifier transistor 62. The signal e _g ′ from which the compensation signal e _c is drawn is supplied from the emitter of the follower transistor 60 to the inputs of the red, green, and blue cathode signal processing networks 34, 36, 38. In this circuit, it can be seen that the compensation signal e _c is drawn from the output of the preamplification stage 14 rather than from the output of the amplifier stage 16 as in FIG.

The network 34 includes a high voltage cathode amplifier transistor 48 biased for low current Class A operation. The network including the transistor 48 performs signal inversion and presents a gain A ₄₈ represented by the following equation.

Here, R ₆₅ and R ₆₆ are the resistance values of the resistors 65 and 66, and R ₄₀ is the variable "back balance" negative gain control resistor 40 used in repair adjustment of the image tube. When the gain adjusting resistor 40 is set in the middle region, the gain A ₄₈ is almost equal to the gain of the grid amplifier stage 16, and the gain A ₁₆ is determined by the following expression.

Where R ₇₂ and R ₇₅ are the resistance values of the resistors 72 and 75, respectively.

In this example, the compensation network 44 is required to set the adjustment 40 in the middle region and to cancel the high frequency component when combining the compensation signal e _c and the signal r ₁ at the base input of the transistor 48. If) determines the gain, the gain ratio of a ₁₆ and a ₄₈ a ₁₆ / a ₄₈ is about 1. Therefore, in FIG. 7, the signal path of the signal gain 1 which generates the compensation signal e _c is established as only the DC blocking capacitor 78 for applying the signal e _c to the base of the transistor 48.

R ₁ signal is synthesized with the resistance (66, 40) and the compensation signal of the complementary signal in the upper base of the transistor 48 via a resistor 81 of e _c e _c. Each of the resistance values 0 is selected so that the amplitudes of the complementary signals r ₁ and e _c are equal when the gain control resistor 40 is set in the intermediate region, whereby the high frequency of the signal r ₁ at the base of the transistor 48 is obtained. Allow components to cancel out the high frequency components of signal e _c .

As in the circuit of FIG. 1, for the same reason as described with respect to FIG. 1, the image tube drive signal for determining the beam current of the electron gun is amplified and replicated in direct proportion to the red signal r, and is then fed to the amplifier stage 16. There is no net modulation of the enemy gun by the high frequency signal from

The amplifier stage 16 exhibits a normal video signal bandwidth (-3 db at about 5 MHz) and a zero input power loss of about 2.7 watts. In this example, the maximum power loss of transistor 48 is about 0.675 watts. The variable resistor 85 of the base input circuit of the transistor 48 is used to adjust the direct current operating point of the red signal amplifying transistor 48 during repair adjustment of the image tube. In this example, the current output level of the transistor 48 is approximately 120. To 170V. Capacitors 87 and 88 provide appropriate frequency compensation for stages 16 and 34, respectively. The grid signal processing passage including the amplifier stages 14 and 16 is alternatingly coupled to bias the stages 14 and 16 and the grid 18 with minimal operation, but to provide a suitable bias for a given system. DC coupling can also be used.

Emitter electrodes of transistors 62 and 48 receive the same bias voltage of + 6.2V from bias network 90. In order to prevent variations in the black level of the output signal rc due to the change in the setting of the gain control resistor 40, the base emitter junction of the transistor 48 is connected to a voltage of about 6.9 V (6.2 V) of the input signal r. The offset voltage of 0.7 V is selected as the maximum value so that the signal current does not substantially flow through the gain control resistor 40 in response to the black level signal state.

The circuit of FIG. 7 requires only four high-voltage transistors, and three of them (corresponding amplification transistors in the transistor 48 and the networks 36 and 38) are in an economical plastic form that does not require external heat dissipation means. It can be done. The heat dissipation means is only necessary for the grid amplifying transistor 62. A wideband (5 MHz) operation is obtained by the high frequency amplification transistor 62 provided for the image tube electron gun, and the high frequency component is processed only by the grid circuit (for example, the amplifier 16), and the red, green, and blue cathode driving amplifiers are Because only low frequency components are processed, high frequency differential rise time errors are essentially eliminated. The circuit also exhibits low sensitivity to short circuits due to discharge of the image tube with low output impedance associated with a class A amplifier using voltage feedback. Furthermore, the video signal amplitude peaking control only needs to be provided in the grid amplifying stage 16 as necessary, and does not need to be separately installed in three cathode signal processing networks as in other r, g, and b video driving circuits. .

Although the signal supplied from the signal source 10 is referred to as the luminance signal in the above embodiment, the signal from the signal source 10 can be any signal including a high frequency component as described above. For example, this signal may be derived alone or synthesized from signals r, g, and b.

In the above-described circuit structure, an image tube having a plurality of grid electrodes respectively associated with each cathode may be used. In this case, each grid electrode may be driven in common by the grid signal e _g from the grid amplifier stage 16.

Claims (1)

An image tube having an electron gun sphere including first and second intensity control electrodes for reproducing an image in response to an image signal applied to the electrode, and for processing a color image display image signal including a low frequency component and a high frequency component; A device 12 for passing a selected high frequency component over a predetermined frequency of the video signal, and amplifying the selected high frequency component in response to the selected high frequency component, supplies the first image tube electrode 18 to the first image tube electrode 18. A device for synthesizing the color image display video signal including the amplification device 16 and the selected high frequency component and the low frequency and high frequency components in such a direction that the high frequency component of the video signal is greatly attenuated. 34, 36, 38) and the second video image amplified video signal in response to the output signal from the synthesizing means. Theater driving amplifier, characterized by consisting of a amplifier 48 of the second feeding (22, 23, 24).

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