JP2002042685A - Deflection yoke and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate defect in display image caused by the variation in temperature without deteriorating the efficiency of a deflection yoke. SOLUTION: This deflection yoke comprises a pair of vertical deflection coils Lv1 and Lv2 connected in series to each other, a variable resistor VR forming the pair of vertical deflection coils Lv1 and Lv2 and a bridge circuit 2 and regulating the ratio of a current I1 to a current I2 flowing through the vertical deflection coils Lv1 and Lv2, and a thermistor Tm having such characteristics that the resistance lowers according to the in temperature and connected to the variable resistor Vr parallel with each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cathode ray tube (CRT).
More particularly, the present invention relates to a deflection yoke used for a display device such as a television receiver or a computer display using the same.

[0002]

2. Description of the Related Art Generally, in a display device using a cathode ray tube, an image is displayed on a screen by deflecting three electron beams emitted from an electron gun up, down, left, and right.
For deflection of the electron beam, a deflection yoke (DY) having a horizontal deflection coil and a vertical deflection coil is used. The horizontal deflection coil generates a horizontal deflection magnetic field that deflects the electron beam in the horizontal axis direction (horizontal direction), and the vertical deflection coil generates a vertical deflection magnetic field that deflects the electron beam in the vertical axis direction (vertical direction). Is what you do.

In such a display device, the three electron beams emitted from the electron gun are deflected up, down, left, and right by a deflection yoke, so that the spot of the electron beam is horizontally and vertically shifted on the fluorescent screen of the cathode ray tube. To form a raster, and by converging (converging) three electron beams at each scanning position, a good image without color shift can be displayed.

In a display device using an in-line cathode ray tube, a horizontal deflection magnetic field generated by the horizontal deflection coil is applied to three electron beams emitted from an electron gun in an in-line (one horizontal line) array. The color misregistration at the peripheral portion of the screen is corrected by using a cushion type (pin winding type) and a vertical deflection magnetic field generated by the vertical deflection coil in a barrel shape (barrel shape). In this case, the saddle type (saddle type) is adopted as the winding structure of the horizontal deflection coil and the vertical deflection coil.

[0005] As shown in Fig. 5, the vertical deflection coils wound in a saddle shape are arranged in pairs in the X-axis direction (left and right) as the horizontal axis of the deflection yoke. FIG. 5 shows the arrangement of the vertical deflection coils Lv1 and Lv2 viewed from the fluorescent screen side (panel side) of the cathode ray tube. The directions of the vertical deflection magnetic fields φV1 and φV2 are shown by three electron beams (B , G, R) are deflected to the lower side of the screen. Hereinafter, for convenience of description, one vertical deflection coil Lv1 is also referred to as a first vertical deflection coil Lv1, and the other vertical deflection coil Lv2 is also referred to as a second vertical deflection coil Lv2.

A pair of vertical deflection coils Lv1, Lv1, shown in FIG.
Lv2 is supplied with a sawtooth current (vertical deflection current) having a vertical deflection period by a vertical deflection circuit (not shown).
At this time, even if the current flowing through each of the vertical deflection coils Lv1 and Lv2 is the same, the vertical deflection coils Lv1 and Lv2
2 and the vertical deflection coil Lv1,
The balance between the magnetic fields φV1 and φV2 due to the pair of vertical deflection coils Lv1 and Lv2 may not be equal due to variations in the characteristics of Lv2 itself, mounting errors when the vertical deflection coils Lv1 and Lv2 are incorporated in the deflection yoke, and the like. . When the balance between the vertical deflection magnetic fields φV1 and φV2 is lost in this way, a difference occurs in the amount of vertical deflection of the electron beams (B, G, and R in FIG. 5) on the left and right sides of the screen. Is distorted into a horizontal trapezoidal shape (hereinafter referred to as “horizontal trapezoidal distortion”).

Therefore, conventionally, as shown in FIG. 6, a pair of vertical deflection coils Lv connected in series with each other is used.
1 and Lv2, a variable resistor VR and a pair of fixed resistors R
1 and R2 are connected in parallel. The pair of fixed resistors R1 and R2 are respectively connected in series on both sides of the variable resistor VR. The slider S of the variable resistor VR is connected to a connection point T1 between the pair of vertical deflection coils Lv1 and Lv2, whereby the pair of vertical deflection coils Lv1 and Lv2 and the variable resistor VR form a bridge circuit 21. It has a configuration.

In the above circuit configuration, the pair of fixed resistors R1 and R2 have the same resistance value. Therefore, when the slider S of the variable resistor VR is at the center position,
Current flows through the pair of vertical deflection coils Lv1 and Lv2 at the same rate. Further, when the slider S of the variable resistor VR is moved from the center position to the fixed resistor R2 side, a change in resistance distribution accompanying the slider S causes the first vertical deflection coil Lv to move.
1, the proportion of the current flowing through the second vertical deflection coil Lv2 decreases accordingly. Conversely, when the slider S of the variable resistor VR is moved to the fixed resistor R1 side from the center position, the second vertical deflection coil L
The ratio of the current flowing to v2 increases, and the ratio of the current flowing to the first vertical deflection coil Lv1 decreases accordingly.

As described above, in the above circuit configuration, the ratio (balance) of the current flowing through the pair of vertical deflection coils Lv1 and Lv2 can be arbitrarily adjusted by changing the position of the slider S of the variable resistor VR. it can. Therefore,
As described above, when the balance between the magnetic fields φV1 and φV2 by the pair of vertical deflection coils Lv1 and Lv2 is not equal in the left and right directions, the vertical deflection coil (Lv1) having the weaker magnetic field strength is used.
Or Lv2) so that the current flows at a higher rate,
By changing the position of the slider S of the variable resistor VR, it becomes possible to correct imbalance between the vertical deflection magnetic fields φV1 and φV2 and correct horizontal trapezoidal distortion.

[0010]

However, in adopting the circuit configuration for correcting the horizontal trapezoidal distortion,
There were the following difficulties. That is, when the surrounding temperature rises due to heat generated by the operation of the deflection yoke or heat radiated from a heating element (a circuit board or the like) in the display device, the DC resistance value of each of the vertical deflection coils Lv1 and Lv2 increases accordingly. To increase. In such a case, if the slider S of the variable resistor VR is displaced from the center position (a state in which horizontal trapezoidal distortion has been corrected), the resistance ratio changes due to the increase in the DC resistance value. Even though the position is not changed, the ratio of the current flowing through each of the vertical deflection coils Lv1 and Lv2 changes, and as a result, the vertical deflection magnetic field φV
The balance of 1, φV2 is also lost.

As a result, in the initial state when the display device is started, even if the raster 1 is formed without distortion as shown in FIG.
7 (B) and 7 (C) due to the imbalance of V1 and V2.
The raster 1 is distorted in a horizontal trapezoidal shape as shown in FIG.
That is, when the magnitude relationship of the magnetic field strengths is φV2> φV1 (in the case of FIG. 7B), the electron beam is more vertically deflected on the φV2 side where the magnetic field strength is large. Horizontal trapezoidal distortion occurs in a wider form. Also, the magnitude relationship of the magnetic field strength is φV2 <φ
In the case of V1 (in the case of FIG. 7C), since the electron beam is further deflected on the φV1 side where the magnetic field strength is large, the horizontal trapezoidal distortion is generated in such a manner that the left side of the raster 1 is wider than the right side. appear.

Further, the magnitude relation of the magnetic field strength is φV2> φ
When V1 is reached, the vertical direction of the raster 1 is
As shown in FIG. 7B, when the convergence changes in such a manner that the red electron beam R shifts to the outside and the blue electron beam B shifts to the inside, and the magnitude relationship of the magnetic field strengths becomes φV2 <φV1, FIG. As shown in (C), the convergence changes in such a manner that the red electron beam R shifts inside and the blue electron beam B shifts outside.

To deal with such a problem of the displayed image, for example, Japanese Patent Publication No. 11-2967683 discloses a technique for canceling an increase in the DC resistance value of a vertical deflection coil due to a temperature rise by a temperature compensation circuit using a thermistor. It has been disclosed.

However, according to the technique described in the above publication, a temperature compensation circuit is formed by connecting two resistors in series and connecting a thermistor in parallel at both ends thereof.
Since this temperature compensating circuit is connected in series between the pair of vertical deflection coils, the DC resistance of the series circuit formed by the pair of vertical deflection coils is greatly increased. As a result, the deflection efficiency of the deflection yoke is significantly deteriorated due to an increase in the resistance component that does not contribute to the vertical deflection of the electron beam.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to solve the problem of a displayed image due to a temperature change without deteriorating the deflection efficiency of a deflection yoke. .

[0016]

In the deflection yoke according to the present invention, a pair of vertical deflection coils connected in series with each other, and a pair of these vertical deflection coils and a bridge circuit are formed to each of the vertical deflection coils. A variable resistor for adjusting the ratio of the flowing current and a temperature compensating element having a characteristic that the resistance value decreases with a rise in temperature and connected in parallel to the variable resistor are provided. Further, the display device according to the present invention uses the deflection yoke having the above configuration.

In the deflection yoke having the above-described structure and the display device using the same, each of the vertical deflection coils is caused by a temperature rise in a state where the slider of the variable resistor is displaced from the center position (a state in which horizontal trapezoidal distortion is corrected). Even if the DC resistance increases, the current flowing through each vertical deflection coil before and after the temperature rise can be changed by the same ratio by decreasing the resistance of the temperature compensation element as the temperature rises Becomes Further, since the temperature compensating element is connected in parallel to the variable resistor for adjusting the current balance, the DC resistance value of the series circuit including the pair of vertical deflection coils does not increase.

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings. In the present embodiment, the same parts as those in the above-described related art will be denoted by the same reference numerals and described.

FIG. 1 is a schematic perspective view showing an overall image of a cathode ray tube to which the present invention is applied. In FIG. 1, a cathode ray tube bulb (cathode ray tube main body) 10 includes a panel section 11, a funnel section 12, and a neck section 13. On the inner surface of the panel section 11, a phosphor screen (not shown) in which red, blue, and green phosphors are arranged in a pattern is formed. On the other hand, an electron gun 14 serving as an emission source of an electron beam is provided in the neck portion 13. A deflection yoke 15 for deflecting the electron beam is mounted on a cone portion extending from the neck portion 13 to the funnel portion 12. This deflection yoke 1
Reference numeral 5 is attached and adjusted such that the center axis of the yoke coincides with the center axis of the cathode ray tube bulb 10.

The cathode ray tube having the above-described structure is incorporated in a casing (not shown) together with various accessories necessary for reproducing a color image (or a black and white image) on the phosphor screen on the inner surface of the panel section 11, thereby providing a television. A display device such as a receiver or a display for a computer is configured.

FIG. 2 is a side view including a partially broken cross section of the deflection yoke according to the present invention. In FIG. 2, the deflection yoke 15
Are equipped with components such as a horizontal deflection coil 16, a vertical deflection coil 17, a separator 18, a DY core 19, and a ring magnet 20. The horizontal deflection coil 16 is wound in a saddle shape on the inner peripheral side of the separator 18, and the vertical deflection coil 17 is wound in a saddle shape on the outer peripheral side of the separator 18. The separator 18 is formed in a substantially trumpet shape using an insulating material such as a resin.

The horizontal deflection coil 16 is connected to the deflection yoke 1.
The vertical deflection coils 17 are disposed in pairs on the left and right sides (horizontal axis direction) of the deflection yoke 15. Then, on the trajectory of the electron beam emitted from the electron gun 14, the horizontal deflection coil 16 generates a magnetic field (horizontal deflection magnetic field) for deflecting the electron beam in the horizontal direction of the screen (horizontal axis direction). Generates a magnetic field (vertical deflection magnetic field) that deflects the electron beam in the vertical direction (vertical axis direction) of the screen.

The DY core 19 is made of a magnetic material such as ferrite, and is formed in a conical cylindrical shape having one opening in the direction of the center axis of the yoke larger than the other. The DY core 19 includes a horizontal deflection coil 16 and a vertical deflection coil 17.
Are mounted so as to cover the deflection coils 16 and 17 in order to enhance the effectiveness of the magnetic field generated by the magnetic field generator. The ring magnet 20 is used to correct the deflection of the deflection yoke 15 in order to correct the trajectory deviation of the electron beam due to an assembly error of the electron gun 14 or the like.
Attached to the rear end.

FIG. 3 is a circuit diagram showing a connection state of the vertical deflection coil according to the embodiment of the present invention. In FIG.
The vertical deflection coil 17 includes a first vertical deflection coil Lv1 and a second vertical deflection coil Lv each wound in a saddle shape.
2. The first and second vertical deflection coils Lv1 and Lv2 are arranged in pairs on the left and right sides (horizontal axis direction) of the above-described deflection yoke 15, and are connected in series with a common connection point T1. I have.

The first and second vertical deflection coils Lv
1 and Lv2, a series resistor circuit having a variable resistor VR1 and a pair of fixed resistors R1 and R2 is connected. This series resistance circuit is connected in parallel with connection points T2 and T3 to both ends of the first and second vertical deflection coils Lv1 and Lv2. In the series resistance circuit,
A fixed resistor R1 is connected in series to one side (left side in the figure) of the variable resistor VR, and a fixed resistor R2 is connected in series to the other side (right side in the figure). The resistance value of the fixed resistor R1 and the resistance value of the fixed resistor R2 are the same. The resistance value of the variable resistor VR is larger than the resistance values of the fixed resistors R1 and R2.

The slider S of the variable resistor VR is connected to a connection point (serial connection point) T1 between the pair of vertical deflection coils Lv1 and Lv2, whereby the pair of vertical deflection coils Lv1 and Lv1 are connected.
Lv2 and the variable resistor VR form a bridge circuit 2. A thermistor Tm serving as a temperature compensation element is connected in parallel to the variable resistor VR. That is, one end of the thermistor Tm is connected to a connection point T4 between the variable resistor VR and the fixed resistor R1, and the other end is connected to a connection point T5 between the variable resistor VR and the fixed resistor R2. The thermistor Tm has a temperature coefficient of resistance of a negative value, that is, a characteristic that the resistance value decreases as the temperature rises.

In the case where such a circuit configuration is adopted, each of the sliders S of the variable resistor VR is displaced from the center position (a state in which horizontal trapezoidal distortion is corrected), and each of the vertical members is raised due to a temperature rise (temperature change). Even when the DC resistances of the deflection coils Lv1 and Lv2 increase, the resistance of the thermistor Tm decreases as the temperature rises, so that the ratio of the current flowing through each of the vertical deflection coils Lv1 and Lv2 is kept constant. be able to.

A variable resistor VR for current balance adjustment
Since the thermistor Tm is connected in parallel, the DC resistance of the series circuit formed by the pair of vertical deflection coils Lv1 and Lv2 does not increase. Therefore, the deflection yoke 15
Of the deflection efficiency can be avoided.

The principle of temperature compensation by the thermistor Tm will be described below. First, as shown in FIG. 4, a vertical deflection current supplied from a vertical deflection circuit (not shown) to a pair of vertical deflection coils Lv1 and Lv2 is represented by Iv. At this time, a current flowing through the first vertical deflection coil Lv1 Is I1, and the current flowing through the second vertical deflection coil Lv2 is I2.
Further, the DC resistance of the first vertical deflection coil Lv1 is RL1
And the DC resistance of the second vertical deflection coil Lv2 is RL2
And Further, as shown in FIG.
Is moved most toward the fixed resistor R1, the combined resistance of the variable resistor VR and the thermistor Tm is R3.

In such a case, the currents I1 and I2 flowing through the first and second vertical deflection coils Lv1 and Lv2 are obtained by the following equations (1) and (2), respectively. I1 = R1 / (R1 + RL1) (1) I2 = (R2 + R3) / (R2 + R3 + RL2) (2) Although the actual current value is obtained by multiplying the vertical deflection current Iv, the present embodiment In, for convenience of explanation,
The description is omitted assuming that Iv = 1.

On the other hand, when the DC resistance of each of the vertical deflection coils Lv1 and Lv2 increases by ΔR due to the temperature rise,
The currents I1 and I2 flowing through the first and second vertical deflection coils Lv1 and Lv2 are obtained by the following equations (3) and (4), respectively. I1 = R1 / (R1 + RL1 + ΔR) (3) I2 = (R2 + R3) / (R2 + R3 + RL2 + ΔR) (4)

As can be seen from the above equations (1) to (4),
Comparing the equations (1) and (3) corresponding to the current I1 in obtaining the currents I1 and I2, the denominator of the fraction increases by ΔR due to the temperature rise, and similarly, the denominators (2) and ( Comparing the expressions 4), the denominator of the fraction increases by ΔR due to the temperature rise. From this, the currents I1 and I2 flowing through the vertical deflection coils Lv1 and Lv2 both decrease due to the increase (ΔR) of the coil DC resistances RL1 and RL2 due to the temperature rise.

Here, the current I1 is obtained (1), (3)
The denominator of the fraction in the equation and the current I2 are obtained (2),
Comparing the denominator of the fraction in equation (4), the denominator on the current I2 side has a much larger value than the denominator on the current I1 side. The reason is that the slider S of the variable resistor VR is fixed to the fixed resistor R
This is because the combined resistance R3 is added to the denominator of the equations (2) and (4) by moving the element to the first side.

Due to such a large difference in resistance distribution, if it is assumed that there is no thermistor Tm (assuming that the combined resistance R3 does not change before and after the temperature rise), the coil DC resistance (RL1 + ΔR, RL2 +
ΔR) differs between the current I1 and the current I2. That is, in the above equations (1) to (4), (2),
Since the denominator of the equation (4) takes a larger value than the denominators of the equations (1) and (3), the current decrease rate (change rate) due to the temperature rise is larger for the current I1 than for the current I2. . Therefore, compared to before the temperature rise, the second
The ratio of the current I2 flowing through the vertical deflection coil Lv2 increases.

On the other hand, when the thermistor Tm is provided, the resistance value of the thermistor Tm decreases due to the temperature rise, and accordingly, the combined resistance R3 of the thermistor Tm and the variable resistor VR also decreases. In such a case, the current I2 flowing through the second vertical deflection coil Lv2 decreases as the combined resistance R3 decreases.
2 increases. Therefore, the resistance-temperature characteristics of the thermistor Tm should be set under the condition that the change rate (decrease rate) of the current I1 before and after the temperature rise is substantially equal to the change rate (decrease rate) of the current I2 before and after the temperature rise. Thereby, the ratio of the currents I1 and I2 can be kept constant before and after the temperature rise.

The principle of temperature compensation by the thermistor Tm described above is the same regardless of which side the slider S of the variable resistor VR has moved from the center position and how much the slider S has shifted from the center position. The principle applies. However, the resistance-temperature characteristics of the thermistor Tm actually used include a temperature change that can occur in a normal use environment, a change in coil resistance accompanying the change, a resistance R1, R2, VR in a series resistance circuit, and a horizontal change. It is necessary to appropriately set the position according to the position of the slider S when correcting the trapezoidal distortion.

Here, the temperature compensation effect of the thermistor Tm will be proved by giving specific numerical examples. First, as a numerical example, the DC resistance of the vertical deflection coils Lv1 and Lv2 is set to RL1.
= RL2 = 4Ω, fixed resistance R1 = R2 = 56Ω, combined resistance of variable resistance VR and thermistor Tm R3 = 200Ω
And Further, when the temperature rises from 20 ° C. to 60 ° C., the combined resistance R
3 is reduced to （(100Ω), at which time the DC resistance of the coil is increased by ΔR = 1Ω.

In such a case, when the temperature is 20 ° C., I1 = 56 / (56 + 4) = 0.9333 I2 = (56 + 200) / (56 + 200 + 4) = by substituting numerical values into the above equations (1) and (2). 0.
9846.

When the temperature is 60 ° C., it is assumed that there is no thermistor Tm (assuming that the combined resistance R3 = 200Ω does not change before and after the temperature rise).
By substituting the numerical value into the equation (4), I1 = 56 / (56 + 4 + 1) = 0.9180 I2 = (56 + 200) / (56 + 200 + 4 + 1) =
0.9808. Then, when the temperature is 20 ° C., the current ratio becomes I1 / I2 = 0.9479, and when the temperature is 60 ° C., the current ratio becomes I1 / I2 = 0.9360. As a result, there is a difference of 0.0119 in the current ratio before and after the temperature rise.

On the other hand, when there is the thermistor Tm and the temperature is 60 ° C., I1 = 56 / (56 + 4 + 1) = 0.9180 I2 = (56 + 100) by substituting numerical values into the above equations (3) and (4). / (56 + 100 + 4 + 1) =
0.9689 is obtained. The current ratio in this case is I1 / I2 =
0.9474, which is almost the same as the current ratio (0.9479) when the temperature is 20 ° C.

By maintaining a constant ratio between the currents I1 and I2 flowing through the pair of vertical deflection coils Lv1 and Lv2 before and after the temperature rise, it is possible to avoid the imbalance of the vertical deflection magnetic field. As a result, it is possible to effectively prevent the occurrence of horizontal trapezoidal distortion and a change in convergence due to a temperature change.

[0042]

As described above, according to the present invention, a temperature compensating element is connected in parallel to a variable resistor for adjusting the ratio (current balance) of the current flowing through each vertical deflection coil. Without increasing the DC resistance value of the series circuit by the vertical deflection coils, the ratio of the current flowing through each vertical deflection coil before and after the temperature rise can be kept constant. As a result, it is possible to solve the problem of the display image due to the temperature change (the occurrence of the horizontal trapezoidal distortion, the change of the convergence, etc.) without deteriorating the deflection efficiency of the deflection yoke.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing an overall image of a cathode ray tube to which the present invention is applied.

FIG. 2 is a side view including a partially broken surface of the deflection yoke according to the present invention.

FIG. 3 is a circuit diagram showing a connection state of a vertical deflection coil according to the embodiment of the present invention.

FIG. 4 is a diagram for explaining the operation principle of the temperature compensation element.

FIG. 5 is a diagram illustrating an arrangement state of a vertical deflection coil and a generated magnetic field thereof.

FIG. 6 is a circuit diagram showing a connection state of a conventional vertical deflection coil.

FIG. 7 is a diagram illustrating a problem caused by imbalance in the vertical deflection magnetic field.

[Explanation of symbols]

2 bridge circuit, 10 cathode ray tube bulb, 15 deflection yoke, 17, Lv1, Lv2 vertical deflection coil, S
Slider, Tm: Thermistor, VR: Variable resistance

Claims (2)

[Claims] 1. A pair of vertical deflection coils connected in series with each other, a variable resistor forming a bridge circuit with the pair of vertical deflection coils to adjust a ratio of a current flowing through each of the vertical deflection coils, and a temperature rise. And a temperature compensating element connected in parallel to the variable resistor. 2. A pair of vertical deflection coils connected in series to each other, a variable resistor forming a bridge circuit with the pair of vertical deflection coils to adjust a ratio of a current flowing through each of the vertical deflection coils, and a temperature rise. A display device characterized by using a deflection yoke having a characteristic that a resistance value is reduced by the temperature compensation element and having a temperature compensation element connected in parallel to the variable resistor.