JPH05103221A - Quadrupole coil driving voltage generating circuit - Google Patents

Abstract

(57) [Summary] [Purpose] Even if there are variations in the parts used or the ambient temperature changes, a constant amplitude correction amount is maintained. A parabolic wave output from a vertical parabolic wave generating circuit 31 is converted into a PWM pulse by a PWM pulse generating circuit 32. The NPN transistor 33 is this PWM
It is driven by a pulse and drives the PNP transistor 34 for switching. A voltage is applied to the coil 38 from the voltage source 37 in response to the switching of the PNP transistor 34, and the coil 38 is integrated. A voltage that changes according to the vertical deflection period and the horizontal deflection period is output from the coil 38, and this voltage is supplied from the quadrupole voltage output circuit 39 to the quadrupole coil drive circuit. Further, a part of the switching voltage is fed back to the PWM pulse generating circuit 32 via the integrating circuit 40.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quadrupole coil drive voltage generation circuit for generating a voltage supplied to a quadrupole coil drive circuit for correcting a beam spot shape of a cathode ray tube.

[0002]

2. Description of the Related Art Conventionally, in a display device using a cathode ray tube, by providing a quadrupole coil around a beam gun, an electron beam at the end portion of the screen within the display screen 2 is displayed, for example, as shown in FIG. The defocusing that occurs when the beam spot 3 has an elliptical shape by obliquely hitting the fluorescent surface is prevented.

[0003]

However, in the conventional device, the quadrupole current is merely corrected in a parabolic shape or a parabola bathtub shape in accordance with the horizontal deflection period, and therefore, the upper end of the screen is corrected. In addition to not being able to obtain stable focus performance at the lower and lower parts, there are variations in the parts used, and
When the ambient temperature changes, the amplitude correction amount changes, and there is a problem that accurate focus correction cannot be performed.

The present invention has been made in view of such a situation, and when realizing stable focus performance even in the upper and lower portions (vertical direction) of the screen, even if there are variations in the parts used, Even if the ambient temperature changes, a constant amplitude correction amount can always be maintained.

[0005]

A quadrupole coil drive voltage generating circuit of the present invention includes a vertical parabolic wave generating circuit 31 as parabolic wave generating means for generating a parabolic wave that changes parabolically in a vertical deflection cycle. A PWM pulse generating circuit 32 as a pulse converting means for converting a parabolic wave into a PWM pulse, a PNP transistor 34 as a switching means for switching corresponding to the output of the pulse converting means, and a voltage switched by the switching means are applied. The coil 38 as the coil means, the integrating circuit 40 as the feedback means for feeding back the voltage obtained by the switching of the switching means to the pulse converting means, and the four as the output means for supplying the output of the coil means to the quadrupole coil. Double pole voltage output circuit 39
And is provided.

[0006]

In the quadrupole coil drive voltage generating circuit having the above structure, the parabolic wave generated by the vertical parabolic wave generating circuit 31 is converted into the PWM pulse by the PWM pulse generating circuit 32. The PNP transistor 34 switches in response to this PWM pulse, and the voltage corresponding to this switching is applied to the coil 38. This coil 38
The voltage integrated by is supplied from the quadrupole voltage output circuit 39 to the quadrupole coil drive circuit. In addition, a part of the output of the PNP transistor 34 is PWMed via the integrating circuit 40.
It is fed back to the pulse generation circuit 32.

Therefore, stable focus performance in the vertical direction can be realized with low power consumption, and at the same time, the amplitude correction amount is always constant even if the parts used vary or the ambient temperature changes. Can be held.

[0008]

1 is a block diagram showing the configuration of an embodiment of a quadrupole coil drive voltage generating circuit according to the present invention. The vertical parabolic wave generation circuit 31 generates a vertical parabolic wave that changes in a parabolic shape in accordance with the vertical deflection period. The PWM pulse generation circuit 32 converts the parabolic wave supplied from the vertical parabolic wave generation circuit 31 into a PWM pulse by comparing it with a sawtooth wave signal generated in synchronization with a horizontal synchronization signal supplied from a circuit (not shown). Then, it is supplied to the base of the NPN transistor 33. NP whose emitter is grounded
The collector of the N-transistor 33 is P via a resistor 36.
It is connected to the base of the NP transistor 34. The emitter and the base of this PNP transistor 34 are resistors 35.
Connected through. In addition, the PNP transistor 34
The voltage E is applied from the voltage source 37 to the emitter of the. The voltage output from the PNP transistor 34 is applied to the coil 38, and the output thereof is further supplied to the quadrupole voltage output circuit 39. Quadrupole voltage output circuit 39
Is configured to supply the voltage supplied from the coil 38 to the quadrupole coil drive circuit. Further, a part of the output of the PNP transistor 34 includes the resistor 41 and the capacitor 4
It is fed back to the PWM pulse generation circuit 32 via the integration circuit 40 composed of two.

The PWM pulse generation circuit 32 is shown in FIG.
It is configured as shown in. In this embodiment, a sawtooth wave generation circuit 52 that generates a sawtooth wave that changes in a horizontal deflection period in synchronization with a horizontal synchronization signal, and a parabola wave that is output from the sawtooth wave and the vertical parabola wave generation circuit 31 are generated. It is composed of a comparison circuit 51 for comparison. Integrating circuit 40
Is added to the parabolic wave and is supplied to the inverting input terminal of the comparison circuit 51.

Next, the operation will be described. The vertical parabolic wave generation circuit 31 generates a parabolic wave that changes in a parabolic shape in a vertical deflection cycle in response to a vertical synchronizing signal supplied from a circuit (not shown). The parabolic wave output from the vertical parabolic wave generation circuit 31 is compared with the sawtooth wave output from the sawtooth wave generation circuit 52 in the comparison circuit 51.
As shown in FIG. 3A, the parabolic wave changes in the vertical deflection cycle, and the sawtooth wave changes in the horizontal deflection cycle. Therefore,
As shown in FIG. 3B, the comparison circuit 51 generates a PWM pulse that becomes high level when the sawtooth wave is higher than the parabolic wave and low level when the sawtooth wave is smaller than the parabolic wave. The level of the parabolic wave increases near the top or bottom of the screen and decreases in the center of the screen, so the pulse width eventually narrows at the top and bottom of the screen and widens at the center. It will be.

The NPN transistor 33 is turned on when a PWM pulse of logic H is supplied from the PWM pulse generating circuit 32 to its base. At this time, the base has a resistance of 36
Since it is grounded via the PNP transistor 34, the PNP transistor 34 is turned on. As a result, the voltage E is applied from the voltage source 37 to the coil 38 via the PNP transistor 34. Also,
Since the NPN transistor 33 is turned off when a logic L is input to its base, the PNP transistor 34 is also turned off at this time. The coil 38 integrates the pulse voltage thus applied and outputs it to the quadrupole voltage output circuit 39. The width of the pulse is wide at the center of the screen and short at the upper and lower ends. Therefore, the voltage output by the quadrupole voltage output circuit 39 increases at the center of the screen and decreases at the upper and lower ends.

In addition, a part of the voltage output from the PNP transistor 34 and supplied to the coil 38 is a resistor 4.
It is integrated by the integrating circuit 40 including 1 and the capacitor 42, and is added to the parabolic wave output from the vertical parabolic wave generating circuit 31. As a result, it is possible to always maintain a constant amplitude correction amount even if there are variations in the parts used and the ambient temperature changes.

FIG. 4 shows the construction of an embodiment of a quadrupole coil drive circuit to which a voltage varying in the vertical deflection cycle is supplied as Vcc from the quadrupole voltage output circuit 39.

The base of the transistor Q1 is connected to the output terminal of the drive circuit 12, and the damper diode D1 is connected to the collector of the transistor Q1. Also, the transistor Q1 and the damper diode D
1, a resonance capacitor C1 is connected in parallel, and a quadrupole coil LOP is connected to the resonance capacitor C1.
And the coil L1 are respectively connected in parallel, and the power supply output is supplied from the voltage Vcc through the resistor R1,
Energy is accumulated in the resonance circuit formed by the quadrupole coil LOP, the coil L1 and the resonance capacitor C1 while the drive circuit 12 is on-operation, and when the transistor Q1 is off-operation in this state, the quadrupole coil is turned on. Resonance is generated between the LOP, the coil L1, and the resonance capacitor C1. One end of the quadrupole coil LOP is connected to one end of the capacitor C1 via a parallel circuit of the diode D2 and the capacitor C3.

In the quadrupole coil drive circuit 20, the resonance capacitor C1 is provided in the quadrupole coil LOP and the coil L1.
Are connected in parallel to form a first resonance circuit, and a resonance capacitor C22 is connected in series to the quadrupole coil LOP and the coil L1 to form a second resonance circuit. The resonance capacitor C22 is a capacitor having a relatively small capacity, and when the transistor Q1 is turned on, the resonance capacitor C22, the quadrupole coil LOP, and the coil L.
The resonance of low frequency is generated between 1 and 1.

Further, a resistor R1 is provided at the output end of the power supply VCC.
The coil L2 is connected in series to the resonance capacitor C2.
It is designed to be larger than the impedance of 2. Therefore, when the transistor Q1 is turned on, the output of the voltage Vcc is prevented from being reduced to the ground side of the voltage Vcc via the ground GND.
The coil L2 constitutes a constant current source.

In the above structure, the quadrupole coil drive circuit 20 is supplied with the voltage output Vcc from the power supply Vcc through the resistor R1 and the coil L2, and the transistor Q1 is turned on by the drive circuit 12 at a predetermined timing. While the transistor Q1 is on, energy is stored in the resonance circuit composed of the quadrupole coil LOP, the coil L1 and the resonance capacitor C1, and then the electron beam is emitted from the screen edge area of the display screen (that is, on the display screen). When the transistor Q1 is turned off by the drive circuit 12 at the timing of scanning the peripheral region), the quadrupole coil LOP, the coil L1, and the resonance capacitor C
During 1, the high frequency resonance occurs.

Therefore, as shown in FIG. 5A, the transistor Q1 is turned off to cause the first resonance circuits LOP, L1 and C1 to be in a resonance state between time points t11 to t13 and time points t14 to t16. Between both ends of the voltage across the resonant capacitor C1 VC (Fig. 5 (B))
Shows the resonance voltage waveform VC1.

Therefore, the quadrupole current IOP2 (FIG. 5 (D)) flowing through the quadrupole coil LOP at times t11 and t14 at which resonance at a high frequency starts is rapidly increased, and the voltage value across the resonance capacitor C1 is increased. Quadrupole coil LO at the times t12 and t15 when
With respect to P, together with the ringing removal capacitor C3,
When the connected clamp diode D2 is turned off (FIG. 5 (C)), the quadrupole current IOP2 (FIG. 5 (D)) flowing through the quadrupole coil LOP sharply decreases. Therefore, the peak-shaped waveform IMA having the maximum value at the times t12 and t15 is formed.

Further, the transistor Q1 is turned on by the drive circuit 12 at the timing when the electron beam scans the central area of the display screen.
At times t13 and t16 at which the resonance state between the coil L1 and the resonance capacitor C1 ends, the quadrupole coil LOP and the coil L1, and the quadrupole coil L
Due to low-frequency resonance occurring between OP and the resonance capacitor C22 having a small capacitance connected in series to the coil L1, the quadrupole current IOP2 has a predetermined curve until the time point t14 at which the subsequent resonance state starts. To form a so-called parabolic waveform that gradually changes.

Therefore, the waveform of the quadrupole current IOP2 drastically decreases while drawing a predetermined curve between the times t12 and t13, then forms a gentle parabolic waveform IPA at the times t13 and t14, and further between the times t14 and t15. At a time t12 to t13 and a time t14 to t15, a part of the mountain-shaped waveform IMA in the bathtub waveform (IPO1) is formed and a gentle increase is made at the time t13 to t14. The changing parabolic waveform IPA is formed, whereby the quadrupole current IOP2 can form a so-called parabolic bathtub waveform in which the mountain-shaped waveform IMA of the bathtub waveform and the parabolic waveform IPA are combined.

Therefore, in the effective display screen DIS2 (FIG. 5D) from the left end L to the right end R of the display screen of the cathode ray tube, the distance from the center of the screen increases in the vicinity of the left end L and the right end R. The shape of the beam spot is greatly corrected according to the abrupt change amount by flowing a quadrupole current having a sharply increasing mountain-shaped waveform IMA to the quadrupole coil LOP, and the effective display screen DIS is displayed.
In the screen center region CENT2 of No. 2, a quadrupole current having a parabolic waveform IPA that gradually increases as the distance from the screen center portion increases is passed through the quadrupole coil LOP, so that the beam spot shape changes gently. It can be corrected little by little according to the amount.

Thus, in a cathode ray tube having a horizontally long and large display screen, the spot shape can be appropriately corrected in response to the change in the beam spot shape depending on the irradiation position of the beam spot.

According to the above structure, the quadrupole coil LOP
And a second resonance circuit that forms a high-frequency resonance with the coil L1 and the resonance capacitor C1 and that produces a low-frequency resonance with the quadrupole coil LOP and the coil L1 and the resonance capacitor C22. In the case of correcting the beam spot shape that largely changes near the edge of the display screen, the first resonance circuit has a four-cornered waveform IMA that greatly changes with respect to the change amount of the distance from the center of the display screen. When correcting the beam spot shape which is generated in the screen central region CENT2 of the display screen while generating the quadrupole current, the second resonance circuit changes the beam spot shape slightly with respect to the change amount of the distance from the display screen center. Parabolic waveform IPA
The quadrupole current can be generated, and the beam spot shape can be appropriately corrected by the quadrupole coil LOP according to the irradiation position of the beam spot.

By doing so, it is possible to correct the gradually changing beam spot shape in the intermediate region between the central portion and the peripheral portion of the display screen, and thus it is possible to further improve the focus characteristic.

Further, since the voltage Vcc supplied from the resistor R1 shown in FIG. 4 changes in the vertical deflection cycle by the configuration shown in FIG. 1, stable focus performance is obtained even in the vertical direction of the screen. be able to. Also,
Since the adjustment corresponding to the vertical deflection cycle is performed by switching, power consumption can be reduced.

[0027]

As described above, according to the quadrupole coil drive voltage generating circuit of the present invention, since a part of the voltage obtained by switching is fed back, even if there are variations in the parts used, Further, even if the ambient temperature changes, a constant amplitude correction amount can always be held, and accurate focus correction can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of a quadrupole coil drive voltage generation circuit of the present invention.

FIG. 2 is a PWM pulse generation circuit 3 in the embodiment of FIG.
2 is a block diagram showing the configuration of an embodiment of No. 2; FIG.

FIG. 3 is a timing chart explaining the operation of the embodiment of FIG.

FIG. 4 is a circuit diagram showing a configuration of an example of a quadrupole coil drive circuit to which a voltage obtained in the example of FIG. 1 is supplied.

5 is a timing chart explaining the operation of the embodiment of FIG.

FIG. 6 is a diagram illustrating distortion of a beam spot on a conventional display screen.

[Explanation of symbols]

 31 Vertical Parabolic Wave Generation Circuit 32 PWM Pulse Generation Circuit 34 PNP Transistor 38 Coil 39 Quadrupole Voltage Output Circuit 40 Integration Circuit

Claims (1)

[Claims] 1. A parabolic wave generating means for generating a parabolic wave that changes in a parabolic shape at a vertical deflection cycle, a pulse converting means for converting the parabolic wave into a PWM pulse, and switching corresponding to an output of the pulse converting means. Switching means, a coil means to which the voltage switched by the switching means is applied, a feedback means for feeding back the voltage obtained by the switching of the switching means to the pulse converting means, and a quadruple output of the coil means. A quadrupole coil drive voltage generating circuit, comprising: an output unit that supplies the pole coil.