KR830002172B1 - Auto kinescope bias device - Google Patents

Abstract

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Description

Auto kinescope bias device

1 is a schematic diagram of a color television receiver according to the present invention.

2 is a detailed view of a portion of the circuit shown in FIG.

3-8 illustrate typical signal waveforms to aid in understanding the FIG. 1 apparatus.

9 and 10 show yet another circuit shown in FIG.

11 to 16 show typical signal waveforms to aid in understanding the circuit operation of FIG.

17 and 18 show yet another embodiment of the circuit portion shown in FIG.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic control bias device for image reproduction kinescopes in a video signal processing device such as a color television receiver, in order to determine the correct retrace current level of each electron beam in a kinescope.

Color image reproduction kinescopes are installed in color television receivers composed of a plurality of electronic layers individually operated by red, green and blue display signals from a composite color television signal. Since the reproduction color image is made by any one of these signals or their combined signal, the optimal reproduction of the color image requires the accuracy of all kinescope driving levels in which the ratio of the color signals is from white to gray to black. In that sense, the three electron guns must have either a very low conduction conductivity or a cutoff state.

Optimal reproduction of color images and grayscale tracking of kinescopes can cause unwanted blockage errors in kinescope reproduction, which may adversely affect the electron gun's bias from a predetermined level. Can be. This error appears as a light color on short-colored tonal images and also reduces the color fidelity of color images. Shutdown errors are due to changes in operating characteristics of the Kinekov and coupled circuits (eg due to their lifetime), temperature effects, and instantaneous kinescope "flashover".

Kinescope blanking adjustments are time consuming and fragmentary or require aberration adjustments over the life of the kinescope. In addition, kinescope blanking and gain adjustments frequently interact with each other and thus require constant adjustments. Therefore, it is good to eliminate the need for this adjustment as this organization is performed automatically by a matching circuit inside the receiver.

Automatic kinescope bias controls are known. Known devices, however, have one or more of the above disadvantages, but the device according to the invention does not see such a loss.

In particular, the automatic kinescope bias device of the present invention does not require a high voltage transistor to be supplied to the sense kinescope cathode retrace current. The device also does not rely on the absolute magnitude of the very low cathode current of the kinescope cut-off current value and is generally insensitive to cathode leakage currents that otherwise lead to kinescope bias correction errors. In a published device, a voltage is sensed instead of low current and the absolute value of the sensed voltage does not need to be known.

The apparatus according to the present invention includes an apparatus for processing an image display video signal having a periodic repetitive image and a blanking period. The apparatus includes an image reproducing kinescope with an electron gun having a cathode and grid intensity control electrode, a network for connecting video signals to the kinescope electron gun, and a device for automatically controlling the kinescope's retrace level bias. do. The control device includes a reference bias voltage source, an auxiliary grid signal and a voltage response sensing network. The reference bias voltage coincides with the ghost erase period.

According to the invention the voltage sensing network consists of a voltage divider connected between the kinescope cathode and the operating potential point.

According to the present invention, the kinescope is composed of a plurality of cathodes to which a video signal is applied, and is composed of a pairing electrode that is commonly activated with respect to the plurality of cathode electrodes, and an auxiliary signal consisting of pulses applied to the common grid electrode.

In FIG. 1, the television signal processing circuit 10 (including a video detector, an amplifier, and a filter stage) is connected to a demodulator-matrix 12, which is a color television signal component. Supply separately from luminance (Y) and chroma (C). The matrix 12 supplies the output low level color shape display signals r, g, and b. This signal is propagated and amplified by the internal circuits of the cathode signal processing circuits 14a, 14b and 14c and amplified with a high level of color at each of the cathode intensity control electrodes 16a, 16b and 16c of the color kinescope 15, respectively. Feed the images R, G and B. For example, the kinescope 15 is provided with an in-line magnetic connection electron gun in the common potential grid 18 formed in each of the electron guns including the cathodes 16a, 16b ', and 16c.

Cathode signal processing circuits 14a and 14b to 14c are similar to this embodiment. Therefore, the following technique of operation and configuration of the cathode signal processing signal 14a is also applied to the cathode signal processing circuits 14b and 14c. The video signal input of the kinescope driver 21 in response to the key gate, 20 (e.g., electronic switch) and key signal V _K in the cathode signal processing circuit 14a. It is connected to the r signal output from the matrix 12. The driving stage 21 includes a single amplification circuit for supplying the amplified high bell output signal R to the kinescope cathode 16a. The input of the voltage circuit comprising the detector 22 is keyed so that the signals V _B and V _S are connected to the cathode 16a. The output signal of the detector 22 is supplied to the bias control stage 24 and generates an output control signal in response to the input signal received from the sensing network. The control signal from the bias control stage 24 is used as a driver for correcting the bias of the amplifier circuit in the driver 21 to control the black level current or the blanking conducted by the cathode 16a as shown below. Supplied as another input.

Logic control device 28 is shown in FIG. The logic device 28 is vertical (H) and horizontal (V) to be drawn within the receiver to generate key signals V _K for operating the gate 20 and key signals V _B and V _S for operating the detector 22. Responds to a blanking signal. The logic device 28 also generates an output voltage pulse V _G during the period in which the negative retrace current of the kinescope 15 is to be measured. The output signal V _G of the device 28 supplies a suitable bias voltage (actually 0 volts in this example) to the grid 18 even at times other than the grid pulse period.

, 제어입력 셋(set, s)와 리셋(reset R)를 포함한다. 플립-플롭(40-42)은 적분회로형 CD4013으로 할 수 있고 인The circuit arrangement of the logic controller 28 is shown in FIG. This circuit is composed of boroughs 30-36 and flip-flops 40-42, which are refined multiple logics as shown in the figure. Flip-flops 40 and 41 are arranged in a counter circuit and flip-flops 42 are arranged in a monostable ("one-shot" one-shot) vibrator. Each flip-flop has input C and D auxiliary outputs Q and

, Control input set (set, s) and reset (reset R). Flip-flop 40-42 can be integrated circuit CD4013

The horizontal blanking signal H is supplied to the inverter 30 and the vertical blanking signal V is supplied to the inverter 32. Output key signals V _S , V _B , V _G and V _K appear at the outputs of the inverters 33, 34, 35, 36. 3 to 8 show the waveforms of the IKI signal along with the horizontal and vertical blanking signals H and V and the mutual time relationship between these signals.

Considering FIG. 1 with reference to FIGS. 3-8, the kinescope's negative retrace current sensor is characterized by a vertical field scan (image tracking) after the end of the vertical starts at time t ₀ . It is performed during each vertical blanking period before starting. This period includes several horizontal periods while there is no image information. The cathodic current sensed at this time does not have a definite effect on the display image because the kinescope is overscanned at this time (i.e. the kinescope electron beam may strike the kinescope surface beyond the image display area).

According to the disclosed device, the gate 20 is opened in response to the key signal V _K to restrain the conduction of the signal r from the matrix 12 to the de-drive end 21. This is obtained during the measurement period between times t ₁ and t ₀ (see Figure 8) during the first two horizontal lines after vertical blanking. At this time, the output level of the driving circuit 21 and the negative electrode bias are maintained at a fixed reference level predetermined by the bias circuit inside the driving stage 21. At this time, the low voltage definition pulse V _G is supplied to the kinescope control grid 18. Referring to FIG. 7, the grid pulse V _G is obtained for the interval time t ₂ -t ₃ within the measurement period t ₁ -t ₆ . The positive grid pulse is in this example at a logic low level corresponding to a normal grid bias level of zero volts. The differential voltage proportional to the difference in the conducted cathode current after the measurement period t _1- t ₆ may indicate that the kinescope electron gun has the correct blanking (ie zero conduction current or a predetermined very small blanking current) or excessive blanking current. It is used to determine if you have conducted the fall. The mode in the measurement, the grid pulse V _G cathode follower (cathode follower) the phase is similar to the grid pulse V _G in the kinescope, such as time to respond to t ₂ -t when the negative electrode during the _third. The amplitude of the generated negative pulse is proportional to the level of negative current conduction but is somewhat attenuated with respect to grid pulse V _G due to the relatively low forward transconductance of the kinescope electron gun grid drive characteristic. The amplitude of the cathode pulse is very small when the cathode return current is at the desired return level.

Under the condition of excessive negative return current, the differential voltage is supplied to the bias control stage 24 after a suitable procedure by the detector 22. The output power signal coming from the bias control stage 24 is a DC (bias) of the driver 21 in a direction for generating a sufficient generation of a desired negative retrace current level by the loop short action to the bias level of the output of the driver 21. Supply to the bias control input of the driver 21 for defining the operating point. Gate 20 returns to the closed position at the end of the measurement period (after time t ₆ in FIG. 8) allowing the color signal from the output of matrix 12 to be connected to drive 21.

9 and 10 show a detailed circuit of the cathode signal propagation network 14a. The cathode signal processing circuits 14b and 14c are similar to the circuit of 14a.

In FIG. 9, the gate 20 is formed of a transistor electronic switch together with the driver amplifier circuit 21. As shown in FIG. The signal r generated from the matrix 12 is supplied to the gate 20 via the input terminal T ₁ , and the key signal V _K is in the open position with respect to the control input of the gate 20 (measurement condition). It was supplied via terminal T ₃ .

The driving stage 21 is an active load circuit including an amplifier composed of an amplifying transistor 54 and a transistor 55. The input circuit connected to the base input of the transistor 55 is composed of a frequency compensating network 50 including a gain variable adjusting resistor 51. An output signal of the transistor 55 is represented in the emitter of the transistor 54 and the output of the impedance circuit 60 is output. It was connected to the kinescope cathode 16a via terminal T ₂ . A voltage divider comprising resistors 65 and 66 was connected between the reference potential point (ground) and the kinescope cathode 16a. Emmy of transistor 55

Since the gate 20 is opened during the measurement period as described above, the output level of the driving stage 21 and the voltage appearing at the output terminal T ₂ together with the bias circuit including the resistors 52, 53 and 57 are obtained. It is set to a fixed reference level determined by the zener diode 58. The output voltage generated by the junction of the voltage divider resistors (65 and 66) has been connected to an input of a detector 22 via a terminal T _5. Voltage boosting by the voltage divider resistors 65 and 66 is compensated by the gain of the circuit inside the potato stage 22. The bias control voltage generated at the output of the bias control circuit 24 was connected to the resistor 57 via the terminal T ₄ . This control voltage induces a crystal current at the base of transistor 55 through resistor 57, and the unchanged level appearing at the output of terminal T ₂ and amplifier 21 is inaccurate negative return current towards the desired return level. It is controlled in the direction of deforming the level.

The negative signal appearing at terminal T ₂ was referred to as S ₁ as shown in FIG. In the FIG. 13 waveform, the positive cathode pulse induced by the grid pulse during the measurement period t ₂ -t ₃ in the presence of excessive cathode retrace current is designed as ΔV (for example, about 100 millivolts). 11 and 12 show the time relationship between the horizontal blanking signal H and the key pulse V _{K for} each of the negative signal S ₁ in FIG. 13.

Cathode blanking current correction in this device does not directly measure cathode leakage currents (e.g. cathode-heater leakage) because published devices do not directly measure very low levels of cathode current in the vicinity of the kinescope cut-off. Current), and the currents become leakage currents.

In this regard, it can be seen from FIG. 9 that the current flowing in the voltage divider resistors 65 and 66 for the entire measurement period is the sum of the negative electrode retrace currents, which is almost 1.7 milliamps. This current is defined by the voltage across the resistors 65 and 66 at the kinescope cathode (almost +180 volts) and divided by the value of this resistor. Thus, a few micro amps cathode retrace current represents a small fraction of the current flowing in the voltage divider resistors 65, 66. When grid pulse V _G appears t ₂ -t ₃

During the measurement period, in the absence of grid pulse V _G , a very small cathode beam current i _bL is conducted by the kinescope. The high cathode beam current i _bH is conducted in response to the grid pulse. The total current is conducted via voltage divider resistors 65 and 66 in the presence and absence of grid pulse currents i _TL and i _TH , respectively. This current contains the leakage component (i _l , almost 5 micro amps), contains less i _bL and i _bH below, and is operated by the video driver amplifier.

i _TL = i _bL + i _l + i ₀

i _TH = i _bH + i _l + i ₀

Over the measurement period, the voltage amplification across the voltage divider resistor (66) V ₆₆ )) is proportional to the value of current and resistance (66 (R ₆₆ )) given in the following equation.

V ₆₆ = R ₆₆ (i _TH -i _TL ) = R ₆₆ (i _bH -i _bL ) The differential voltage generated across the resistor 66 and coupled to the detector 22 during the measurement period is current i ₀ and leakage current i. _It is not affected by _l and only depends on the cathode beam current difference (i _bH -i _bC ). This current difference and the level of the corresponding difference voltage V ₆₆ across the resistor 66 become smaller as the cathode beam current causes the kinescope to cut off and blanks out.

In this embodiment, the amplitude range for grid pulse V _G is +5 to +15 volts and the amplitude tolerance is ± 10%. When the signal V _G is applied to a control grid, such as a single control grid installed in an inline self-focusing kinescope, the video drive signal can be applied to the kinescope cathode or control grid. The negative pole of the kinescope is AC-coupled rather than DC-coupled by a number of capacitors (not shown) installed between the resistor 65 and the impedance circuit 60 and the circuit connection point of the kinescope negative electrode (FIG. 9). Should be considered. In this case the direct current i ₀ (as defined above) flowing through the voltage divider resistors 65 and 66 is zero. In this case, too, the urgent explanation and the mathematical vertical are used. Even in this case, the currents i _TL , i _TH , i _bL , i _bH and i _l conducted by the resistor 66 are both DC values and AC values.

Especially in the case of AC connections, the total current conducted by the impedance 60 in the absence and presence of grid pulses consisted of currents i _TL and i _TH , respectively. This current includes cathode beam currents i _bL and i _bH and leakage components i _l that flow from the kinescope cathode to the output of video amplifier 21 by the following equation.

The magnitude of the voltage across the impedance 60 (V ₆₀ ) over the measurement period is proportional to the current and impedance 760 (Z ₆₀ ) given above by the following equation.

V ₆₀ = Z ₆₀ (i _bL -i _bH )

This voltage is not affected by the leakage current i _l . The voltage V ₆₀ is related to ground due to the low AC signal output impedance of the amplifier 21 and is derived from the negative side of the impedance 60 via the additional capacitor. Voltage V ₆₀ is connected to detector 22 via voltage divider resistors 65 and 66.

10 is a detailed circuit diagram of the detector 22 and the bias controller 24. Detector 22 is a circuit that includes low voltage transistors 70-79, and bias controller 24 is a circuit that includes low voltage transistors 80-82.

The negative signal S ₁ generated across the resistor 66 in FIG. 9 is connected to the input of the base of the transistor 70 in the circuit 22 in the case of the terminal T ₅ . The current source transistor 70 in the emitter circuit of the transistor 70 is provided inside the feedback clamping circuit to convert the DC level across the emitter resistor 90. The key signal V _B (see FIG. 6) is applied to the base electrode of the transistor 71 via the terminal T ₇ and provided to control the conduction state of the transistor 71. The potential of the input signal S ₁ as shown in the emitter circuit of the transistor 70 is restrained or blanked out at all times except for the times t ₂ -t ₃ and t ₄ -t ₅ . In FIG. 14 S ₄ , the resulting signal is applied to an amplifier comprising transistors 76 and 77. The amplification and reverse potential of this signal appear across resistor 91. This amplified and inverted signal points to S ₃ shown in FIG.

Signal S ₃ comprises the first pulse component P ₁ between times t ₂ and t ₃ and the J pulse component P ₂ between times t ₄ and t ₅ . The difference ΔV 'amplified between the pulses P ₁ and P ₂ is the presence of the negative pulse ΔV' and the pulse ΔV generated in response to the grid pulse V _G corresponding to the condition of the excessive negative retrace current. The difference between the amplification component ΔV (see Fig. 13) of the negative pulse and the resultant pulse P ₁ each P ₂ is determined by

The negative-going peak amplitude excursion of signal S ₃ includes feedback clamping circuit including comparison transistors 74 and 75 and a peak detector and transistors 72 and 73 capacitor ( 92) proceeded by a holding circuit comprising resistors 93,94,70. This circuit is a Zener reference diode 95 which prevents the negative-going amplitude excursion of pulse P ₁ within signal S _{3 at} a level corresponding to the +5.6 volt reference voltage level generated at the base input of comparison transistor 74. do. The final signal from the selector of transistor 75 is applied to the base input of controlled current transistor 71 to change the DC level of the input signal across the resistor 90. The magnitude of the level shift is proportional to that charged in the capacitor 92 and provides level fixation of the signal S ₃ . In particular, the feedback clamp circuit by the level shifting is performed at the correct operating level in the detector 22, under current conditions that otherwise change the DC level of the signal S ₃ (ie due to variations in the operating supply voltage or kinescope electrode voltage). Hold signal S ₃ .

Signal S ₃ is applied to a comparator comprising transistors 78 and 79 and generates a signal S ₄ (see FIG. 16) in the collector axial force of transistor 79. The initial switching level of the comparators 78,79 in this example is +6.2 volts, which is determined by the bias voltage applied to the base electrode of the comparator transistor 79 via the resistor 96 from the bias network 100. . The initial switching level of +6.2 volts of the comparators 78,79 is slightly higher than the +5.6 volt clamping level of the applied signal S ₃ .

The bias network 100 is common to each cathode signal propagation network (ie, networks 14a, 14b, 14c) in this example. The network 100 has a reference potential point (ground) and a positive DC potential (+12). Volts) in series with resistor 102 diode 105 and zener diode 95. The +6.2 volt initial switching level across comparators 78,79 is equal to diode 105 (+0.6 volt) and zener. This is equal to the sum of the voltage across diode 95 (+5.6 volts) The +5.6 volt reference voltage used by the corresponding circuitry inside the cathode signal propagation network 14b and 14C (see Figure 1) only

Comparators 78 and 79 do not respond to signal V _S during time t ₂ -t ₃ when pulse P ₁ appears (see FIG. 15). At this time the comparator continues to generate a positive DC output level corresponding to the FIG. 16 signal S _4a . This output level is also maintained for the time t ₄ -t ₅ at which pulse P ₂ emerges, for conditions of excessive blanking current.

Under conditions of excessive negative retrace current, the continuous positive output level from the comparators 78,79 (signal S _4a ) is charged by the terminal capacitor ₄ after the bias correction voltage is filtered by the capacitor 88. And an inverted peak sensing circuit comprising 85 and transistors 80, 81, 82. This correction voltage is applied to the drive amplifier 21 via terminal T ₄ to detect an increase in the output level of the sphere 21, thereby increasing the cathode bias in the positive direction to reduce the cathode retrace current by a desired level.

The paused output level of the drive amplifier 21 continues to increase and the negative retrace current level continues to decrease until the initial switching level of the amplifier comparator of pulse P ₂ on signal S ₃ is reached. At this time the comparator operates to generate a negative-highing output signal corresponding to the FIG. 16 signal S _4b . The reverse peak sensing circuit senses and stores the representative voltage of the signal S _4b peak level emitted from the capacitor 88. Due to the adverse action of the peak detector transistors 81 and 82, this voltage is positive with respect to the signal from the comparators 78 and 79 and provides an increase in charge to the capacitor 88. The via correction voltage derived from the signal S _4b thus moves in a direction to prevent an increase in the paused output level of the driver driver 21 when the desired negative retrace current level is reached and the driver 21 via terminal T ₄ . Supplied to.

In this embodiment, the crystal blanking current level is not a zero level but a very small level. Therefore, the non-corrective cathode blanking current corresponds to an overcurrent conduction condition or a zero cathode returning current condition above a very small desired level. In the latter case, the non-modification condition of the zero-cathode retrace current is supplied from the circuit 24 to the driver 21 having the polarity direction to adjust the pause output level of the driver 21 to a correction level, that is, a relatively low level. The negative return current of the

In this example, the kinescope buyer correction takes place beyond several scanning fields, because several pulses (signal S _4b ) are needed to charge the capacity 85 at the peak level of signal S _4b . Several fields are also required to discharge the capacitor 85. The charge and discharge time constants for capacitor 85 were chosen to supply a bias correction voltage over filter capacitor 88 without field rate ripple that modulates brightness from the top to the bottom of the image screen.

Impedance network 60 as shown in FIG. 9 provides excessive attenuation avoidance of the induced cathode output signal (eg, FIG. 13 pulse ΔV) by increasing the external cathode impedance. This attenuation can occur if not otherwise because only the internal kinescope cathode impedance is high while the output impedance of the driver amplifier 21 is very low. 17 shows an embodiment of the selection circuit of the impedance 60.

Impedance 60 consists of a single resistor R shown in circuit 60a or a combination of parallel resistor R and capacitor C, as shown by circuit 60b. The latter allows the circuit to increase in resistance R without loss of video signal bandwidth. For this purpose, the capacitance value of capacitor C is low enough to exhibit high impedance at the frequency synthesized with the cathode drive signal. Appropriate values for resistor R and capacitor C are shown in the table.

The network 60 consists of a pair of diodes connected in reverse parallel connection, as seen from circuit 60C. This diode circuit exhibits low impedance for a large negative signal and exhibits a large impedance for a small negative output signal that occurs during the measurement period. High diode impedance is the result when the diode is around the diode cut-off or when the diode DC current is small or absent. The condition is consequently an AC connection between the negative electrode and the detector 22 when the same voltage actually appears at the input and output terminals of the diode circuit during the measurement period in which the negative retrace current level approaches the desired retrace level. Despite the D and C connections between the kinescope cathode and the detector 22 via the resistors 65 and 66 shown in FIGS. 9 and 10, the current io (as defined above) is maintained in the circuit 60C. It will flow through one of the diodes, thereby continuing to maintain a low impedance.

A better choice is exerted by the switch impedance circuits 60d and 60e. Each of these circuits includes a pair of impedances Z ₁ and Z ₂ and an electronically configured switch S ₁ . In this case, the switch S is operated during the image scanning time, the circuit exhibits low impedance from the input to the output, and the switch S is driven during the cathode current measurement period, and the circuit exhibits high impedance from the input to the output.

8 shows a variation of the cathode circuit connected between the driver amplifier transistor 54 (FIG. 9) and the kinescope cathode. Circuits (a) and (b) of FIG. 18 reveal an optional connection of arc suppression (current limiting) of the protective resistor between the amplifier transistor 54 and the kinescope cathode.

Although the present invention has first been described within the limits of the embodiments, it should be recognized that various modifications may be made without departing from the scope of the invention.

As an illustration, it is noted that the reference level, which does not move during the measurement period in the FIG. 9 connection, is performed by the cooperation of the resistors 52, 53, 57 and the diode 58. However, this reference level can be performed by such a method that responds to the appropriate level available from the video signal supplied to the kinescope driver during the measurement period. In addition, it can be interpreted as another angle of the grid signal V _G.

Claims (1)

The image reproduction kinescope has a reference bias to the cathode electrode via a cathode current conduction path during the measurement period corresponding to the electron gun having a cathode and a grid intensity control electrode, a device for supplying a video signal to the kinescope electron gun, and the blanking period. An apparatus for processing an image display video signal having a periodic repetitive image period and a blanking period, wherein the grid electrode is biased forward by supplying an arbitrary signal to the grid electrode during the measurement period. The control logic circuit 28 is connected to the kinescope, the input of the voltage response sensor 22 is connected to the cathode current conduction path, and its output is negative in response to any signal during the measurement period. The current flowing in the current passage and the cathode current passage in a period different from the measurement period. Supply a differential voltage proportional to the difference between the flowing currents, and the bias control circuit 24 responsive to the differential voltage supplies a control signal to the video signal combiner to a minimum level consistent with a predetermined kinescope bias condition. And an automatic kanescope bias control device configured to vary the bias of the kinescope in a direction to reduce the adhesion.

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