JPS6022551B2 - White balance adjustment device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In order to improve the color reproduction of a color television, the present invention uses a standard white color having a relatively low color temperature at a luminance level below a certain threshold value, and a reference white color having a relatively low color temperature at a luminance level below a certain threshold value. The present invention relates to a white balance adjustment device in a color television receiver configured to switch the reference white color so that the color temperature of the reference white color gradually increases as the brightness level increases.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below, but first, in order to facilitate understanding of the present invention, the basic principle of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram of the main parts of an embodiment of a color television receiver configured to switch the reference white color.

In the figure, a brightness signal is applied to terminal 1, and transistor 2 and resistors 5, 9, which constitute an emitter follower,
A luminance signal is applied to the emitter terminals of transistors 4, 8, and 12 via 13. (R-Y), (G-Y), and (B-Y) color difference signals are applied to terminals 3, 7, and 11, respectively, and transistors 4, 8, and 12 receive color difference signals applied to their base terminals and emitters, respectively. A difference signal between the luminance signals applied to the evening terminal is generated, and this is amplified to generate primary color signals R, G, and B at the respective collector terminals. resistance 6,
10 and 14 are load resistances. The configuration up to this point is the same as that of a normal color television receiver, and is generally referred to as the output circuit. The primary color signal B generated at the collector terminal of the transistor 12 is applied to the cathode electrode 24 of the blue electron gun of the color picture tube 26 through a circuit network consisting of resistors 19 and 21 and a Zener diode 20, and is then applied to the cathode electrode 24 of the blue electron gun of the color picture tube 26 to generate blue electrons. Modulate the beam. Similarly, the primary color signal G generated at the collector terminal of transistor 8 is transmitted through resistors 16 and 18.
The green electron beam is applied to the cathode electrode 23 of the green electron gun via a circuit network consisting of a Zenner diode 17 and modulates the green electron beam. Further, the primary color signal R generated at the collector terminal of the transistor 4 is applied to the cathode electrode 22 of the red electron gun via the resistor 15 to modulate the red electron beam. The amount of beam current flowing through the electron gun is determined by the difference between the voltage applied to the cathode electrode and the voltage applied to the first grid electrode (not shown). Now, if we focus on the red electron gun assuming that the first grids of the red, green, and blue electron guns are maintained at fog potential, when the voltage at the collector terminal of transistor 4 decreases, the voltage at cathode electrode 22 also decreases. However, since the beam current flows through the resistor 15, a voltage proportional to the beam current is generated across the resistor 15. Since this voltage is generated in a direction that cancels out the voltage change occurring at the collector terminal, the beam current becomes difficult to flow. In other words, it produces negative feedback to the resistor 15, which has the effect of reducing the nonlinear characteristics of the electron gun and allowing it to operate more nearly linearly. The nonlinear characteristic of an electron gun is generally referred to as gamma. That is, the resistor 15 has the effect of controlling gamma, and as the resistor 15 becomes larger, the amount of negative feedback increases, the gamma becomes smaller, and the gamma becomes closer to linearity. Blue diode 7, 20 has a certain threshold voltage (
If the box pressure between the terminals is below that zener voltage, it will turn off, and if it exceeds that zener voltage, it will turn on.

If the beam flow flowing through the green electron gun and blue electron gun is small,
The voltage generated across the resistor wires 6, 19 is smaller than the Zener voltage, and the Zener diode 17, 2, is off. At this time, resistance 60 resistance 15 = resistance IQ + resistance 1
If 6 = resistance 14 + resistance 19, the red, green, and blue electron guns will operate with equal gamma, and white balance will be achieved. Next, when the beam current flowing through the green and blue electron guns increases and the voltage between the terminals of the resistors 16 and 19 exceeds the Zener voltage, the Zener diodes 17 and 20 turn on, and the cathode circuit of the green electron gun The resistor inserted in is resistor 16
and 18 in parallel, and ``The resistance inserted in the cathode circuit of the blue electron gun will be the parallel combination of resistors 19 and 21.

At this time, if the values of resistors 18 and 21 are set so that the following condition is satisfied: [Resistor 14 + Resistor 19 Resistor 21] < [Resistor 10 + Resistor 16 Resistor 18] < [Resistor 6 + Resistor 16] , the gamma of the blue electron gun is the largest, the gamma of the red gun is the smallest, and the gamma of the green electron gun is approximately halfway between red and blue.

In this way, as shown in FIG. 2, at a luminance signal level of point 30 or higher indicating a certain threshold value, the blue beam current 33 is the largest, followed by the green beam current 32 and the red beam current 3.
1 can be made smaller in order, and on a color picture tube screen, an image whose color temperature gradually increases above a certain luminance signal level is reproduced. The above is the operating principle of a color television receiver configured to switch the reference white color. However, there are the following problems in adjusting the white balance of such a color television receiver.

The conventional white balance adjustment method uses red, green, and blue receivers to receive the light emitted from a color picture tube, amplifies the light, and causes the meter pointer to swing until the meter pointer reaches the specified value. Adjust the cutoff characteristics of the color picture tube and the drive amount of the video signal.

The cutoff characteristic is adjusted at a portion where the light emitting output of the color picture tube is small, and the drive amount of the video signal is adjusted at a portion where the color picture tube's light emitting output is large. Zener diodes 17 and 20 have no effect on cutoff characteristic adjustment, but when adjusting the drive amount, it is necessary to increase the light emission output, so Zener diodes 17 and 20 are turned on, and the beam Since an imbalance occurs in the current, the standard value of the conventional meter pointer will no longer be adopted. Also, if the size of the color picture tube changes or the high voltage applied to the anode electrode of the color picture tube changes, the value of the beam fin flow to obtain the same light emitting output from the color picture tube will differ. Since the influence of the energizer diode is different, and it is necessary to change the specified value of the pointer of the meter accordingly, extremely complicated process control is required. It may be possible to make adjustments by lowering the light emitting output of the color picture tube to a region where the Zener diode is off, but this would result in a corresponding reduction in adjustment accuracy.

The present invention aims to provide a highly accurate white balance adjustment device that reduces the complexity of the adjustment described above.

FIG. 3 shows a main circuit of an embodiment of the present invention. Components having the same functions as those shown in FIG. 1 are designated by the same reference numerals. In the same figure, resistors 16 and 19
If the resistors 41 and 42 are connected in parallel to the beam current, the voltage applied to the Jenner diodes 17 and 20 will decrease, so if the values of the resistors 41 and 42 are appropriately selected, Even if a beam current is applied to the extent that the light emitting output of the color picture tube necessary for accurately adjusting the white balance is supplied, the Jenner diodes 17 and 20 will not turn on. At this time, the resistance of the cathode circuit of the blue electron gun is the parallel composite value of the resistor 42 and the resistor 19, and the resistance of the cathode circuit of the green electron gun is the parallel composite value of the resistor 41 and the resistor 16. The load resistors 6, 10, and 14 (see Figure 1) in the output circuit also act as cathode resistors for the color picture tube, so in order to align the gamma of the red, green, and blue electron guns, resistor 15 is required.
A resistor 40 is also connected in parallel with the resistor 40 so that the following relationship is satisfied. [Resistor 60 Resistor 15 Resistor 40] = [Resistor 10 + Resistor 16 Resistor 41] = [Resistor 14 + Resistor 19 Resistor 42] Resistors 40, 41, and 42 can be changed to resistance I with one touch.
In terms of efficiency, it is preferable to group the resistor blocks 43 together so that they can be connected to the resistor blocks 5, 16, and 19.

Connect resistor block 43 to resistors 15, 16, and 19 to adjust the white balance, and once the adjustment is completed, connect resistor block 4
When 3 is removed, the white color has been adjusted to the specified standard white color. The results of experiments by changing the values of resistors 40, 41, and 42 show that when the load resistance is 1 female ○, resistance 40 = resistance 41 = resistance 42: 0 to 5. Good results were obtained in the pulse ○ range.
(At this time, resistance 15=resistance 16=resistance 19=1 arc ○, and voltage=5V.) FIG. 4 shows an example of a jig for actually implementing the present invention.

In recent color television receivers, the output circuit portion is included in a neck printed board 51 attached to the neck portion 50' of the color picture tube 25. This printed board 51
Assume that the resistor 15 is soldered to the copper foil parts 52 and 53 as shown in the figure. (The same applies to the resistors 16 and 19, which are not shown in the figure.) This neck printed board 5
A stopper 56 is attached to the end of the stopper 56 to be detachably connected to the end of the
, 57, 58, 59 is prepared. Conductive pins 50 and 61 and a resistor 40 are attached to the jig 55, and both ends of the resistor 40 are connected to the pins 60 and 61 by wires 63 and 64. Jig 55 with stopper 5
When the pins 60 and 61 are inserted so that they match the ends of the neck printed board 51, the pins 60 and 61 come into contact with the steel sheet parts 52 and 63. (In the diagram, pin 60 is shown for clarity.
, 61 are written as long, but they should actually be shorter than the stopper. ) This jig 55 is attached to the neck printed board 51 to adjust the white balance, and is removed after adjustment. It is also possible to support the pins 60 and 61 on the board 67 with springs 66 as shown in FIG. .

As described above, according to the present invention, the white balance can be adjusted using the same method as before without changing the white balance meter or complicated process control, and the effect is extremely large. There is.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of the main parts of an example of a color television receiver configured to switch the reference white color, Figure 2 is a characteristic diagram showing changes in beam current obtained by the circuit of Figure 1, and Figure 3 is FIG. 4 is a perspective view of a main part showing a specific example of the present invention, and FIG. 5 is a configuration diagram of a main part of another embodiment of the present invention. 2, 4, 8, 12... Transistor, 17, 20... Zener diode, 6, 10, 14... Negative auxiliary resistor, 16
,16,19.40,41,42...Resistance,22,
23, 24... Cathode electrode, 25... Color picture tube, 51... Neck printed board, 52
, 53... steel foil part, 55... jig, 56, 57, 58,
59... Stopper, 60, 61... Pin, 63,
64...Wiring, 66...Spring, 67...
…·substrate. Figure 1 Figure 2 Figure 3 Figure S Figure 4

Claims (1)

[Claims] 1. Between the cathode electrodes of the red, green, and blue electron guns constituting the color picture tube and the output terminals of output circuits that generate red, green, and blue primary color signals, respectively. 1, 2nd,
A third impedance element is connected, and Zener diodes are connected in parallel with each of the second and third impedance elements, so that the reference white color is changed when the luminance signal level exceeds a certain threshold. 1. A white balance adjustment device for adjusting the white balance of a color television receiver configured as described above, characterized in that the device includes means for turning off the Zener diode when necessary. 2. In claim 1, the means for turning off the Zener diode is configured with means for shorting the first, second, and third impedance elements. White balance adjustment device. 3. In the description of claim 1, the means for turning off the Zener diode includes fourth and fifth impedance elements, respectively, in parallel with the first, second and third impedance elements.
, a white balance adjustment device comprising means for connecting a sixth impedance element. 4. In the description of claim 3, each of the first, second, third, fourth, fifth, and sixth impedance means uses a resistor, and the Zener diode is turned off. The means includes the first, second,
a printed circuit board having a copper foil on which a third impedance element is attached with electrical continuity;
It has conductive pins that can be connected to and separated from the copper foil portions to which the second and third impedance elements are attached, and
A white balance adjustment device comprising a member to which the fourth, fifth, and sixth impedance elements are electrically connected to the conductive pins. 5. The white balance adjustment device according to claim 4, wherein the conductive pin is attached to the member via a spring.