JPH064033A - Deflection coil driving system - Google Patents

Abstract

PURPOSE:To obtain the deflection coil driving system which has excellent linearity and requires no high voltage in a flyback period. CONSTITUTION:A switch 13 is turned ON in a scanning period and a saw-tooth wave signal VIN which is inputted to an amplifier 12 is amplified by the amplifier 12 in the scanning period and supplied to a deflecting coil 10 through a switch 13. Consequently, the deflecting coil is driven by a current amplification system. In the flyback period, the switch 13 is turned OFF. Consequently, the deflecting coil 10 is disconnected from the amplifier 12 and resonates with a capacitor C1 connected in parallel to generate flyback pulses VL, so that a deflecting current IL is deflected back.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deflection coil driving system.

[0002]

2. Description of the Related Art A deflection coil is widely used for deflecting a charged particle beam in a CRT display device, a scanning electron microscope (SEM), etc., and its drive system is classified into a pulse drive system and a current amplification system. One is mainly used.

FIG. 7 is a diagram showing an example of the configuration of a deflection coil drive circuit based on the pulse drive system, which is configured to supply a drive current to the deflection coil 1 by switching the transistor Q ₁ by a synchronization signal 2. . Further, FIG. 8 is a diagram showing a configuration example of a drive circuit of a current amplification system, in which an input current of a sawtooth wave is amplified by an amplifier 3 to drive a deflection coil 1.

[0004]

The pulse driving method is widely adopted in the deflection circuit of the CRT display device because of its simple circuit structure and good efficiency, but it has a problem in linearity, and therefore S There is a problem that not only a circuit for performing distortion correction such as character distortion correction and pincushion distortion correction becomes complicated, but also fine distortion correction is very difficult.

On the other hand, the current amplification method is used for driving the scanning coil of the SEM because it has good linearity and can perform distortion correction with high accuracy, but it is large during the blanking period. There is the problem of requiring a voltage. That is, in FIG. 8, the inductance of the deflection coil 1 is L _y , the resistance of the deflection coil 1 is R _y , and the deflection current is I _L.
Then, the required power supply voltage E is expressed by E = L _y × (dI _L / dt) + R _y × I _L , but the change over time of the drive current becomes extremely large during the blanking period. Therefore, the power supply voltage E required for is large.

An object of the present invention is to solve the above-mentioned problems and to provide a deflection coil driving system which has good linearity and does not require a high voltage during the blanking period.

[0007]

In order to achieve the above object, in the deflection coil driving system of the present invention, the deflection coil is driven by the current amplification system during the scanning period and is driven by the pulse driving system during the blanking period. It is characterized by

[0008]

According to the present invention, since the driving is performed by the current amplification method during the scanning period, not only the linearity is good, but also various distortions can be easily and accurately corrected. it can. Then, during the blanking period, since the operation of the pulse drive method is performed, a high power supply voltage is not required,
Therefore, the loss can be reduced as compared with the conventional case.

[0009]

Embodiments will be described below with reference to the drawings.
FIG. 1 is a diagram showing a configuration of an embodiment of a deflection coil driving system according to the present invention, FIG. 2 is a waveform diagram for explaining the operation, 10 is a deflection coil, 11 is a sawtooth wave generator, and 12 is a sawtooth wave generator.
Is an amplifier and 13 is a switch.

The saw-tooth wave generator 11 generates a saw-tooth wave signal V _IN shown in FIG. 2A and a control signal V _CONT that is at a low level during the blanking period shown in FIG. 2B. Then, the sawtooth wave signal V _IN is input to the amplifier 12, and the control signal V _CONT is supplied to the switch 13. The control signal V _CONT is at the high level during the scanning period and is at the low level during the retrace line period. When the control signal V _CONT is at the high level, the switch 13 is closed, and when it is at the low level, the switch 13 is open.

Therefore, during the scanning period, the sawtooth wave signal V _IN input to the amplifier 12 is amplified by the amplifier 12 and supplied to the deflection coil 10 via the switch 13. That is, during the scanning period, the same drive as the conventional current amplification method is performed. However, since the switch 13 is opened during the blanking period, the deflection coil 10 is disconnected from the amplifier 12,
Resonance with the capacitor C ₁ connected in parallel produces the retrace pulse _VL shown in FIG. 2C, which causes the deflection current I _L to be swung back as shown in FIG. 2D.

[0012] Incidentally, in the conventional current amplification method is the supply voltage of the amplifier 12 V _- is the minimum value V of the retrace pulse V _L
Although it has to be smaller than _Lmin , in the present invention, the pulse driving method is used during the blanking period.
As shown in FIG. 5, it operates even if V ₋ > V _Lmin .

In FIG. 1, the switch 13 may have any structure as long as it can be controlled to be turned on / off from the outside. In practice, the load constant, the length of the blanking period, It may be configured using a transistor, a field effect transistor, a relay, an analog switch, or the like in consideration of the return pulse voltage and the like.

FIG. 3 is a diagram showing an example in which the switch 13 is constituted by a parallel circuit of a transistor Q ₂ and a diode D ₂ , and FIG. 4 is a waveform diagram for explaining the operation thereof. The transistor Q ₂ is turned on during the scanning period and turned off during the blanking period, whereby the above-described operation is performed. Here, ON / OFF control of the transistor Q ₂ is, although of course can be done by applying a control signal V _CONT shown in FIG. 2B to the base, the predetermined threshold value V _TH in FIG. 3 It is set so that it is turned off during the flyback period by setting it. That is, since the output voltage V _O of the amplifier 12 becomes less than the threshold value V _TH during the blanking period, the transistor Q ₂ is turned off, whereby the deflection coil 10 is disconnected from the amplifier 12, and the capacitor C ₁ connected in parallel. retrace pulse V _L is generated as shown in FIG. 4C by resonating with, thereby deflecting current I _L Figure 4D
It is turned back as shown in.

FIG. 5 is a diagram showing an example in which the switch 13 is composed of a parallel circuit of transistors Q ₃ and Q ₄ , and FIG. 6 is a waveform diagram for explaining the operation. The control signal V _CONT is applied to the bases of the transistors Q ₃ and Q ₄ . The control signal V _CONT is also supplied to the switches S ₁ and S ₂ . The switch S ₁ is on during the scanning period and off during the blanking period, and the switch S ₂ is off during the scanning period and on during the blanking period.

Therefore, during the scanning period, the input sawtooth wave signal V
_IN is input to the amplifier 12 via the switch S ₁ , is amplified, and is supplied to the deflection coil 10 via the switch 13. However, during the blanking period, the deflection coil 10 is operated by the amplifier 12
Capacitor C ₁ disconnected from and connected in parallel
By resonating with, a retrace pulse V _L shown in FIG. 6C is generated, which causes the deflection current I _L to be swung back as shown in FIG. 6D. It should be noted that the switches S ₁ and S ₂ are provided to prevent the amplifier 12 from being saturated during the blanking period, so that it may be prevented.

Although the embodiments of the present invention have been described above, it is obvious to those skilled in the art that the present invention is not limited to the above embodiments and various modifications can be made.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an exemplary embodiment of the present invention.

FIG. 2 is a waveform diagram for explaining the operation of the configuration of FIG.

FIG. 3 is a diagram showing another configuration example of the present invention.

FIG. 4 is a waveform diagram for explaining the operation of the configuration of FIG.

FIG. 5 is a diagram showing still another configuration example of the present invention.

6 is a waveform diagram for explaining the operation of the configuration of FIG.

FIG. 7 is a diagram for explaining a pulse driving method.

FIG. 8 is a diagram for explaining a current driving method.

[Explanation of symbols]

10 ... Deflection coil, 11 ... Sawtooth wave generator, 12 ... Amplifier, 13 ... Switch.

Claims (1)

[Claims] 1. A deflection coil driving method, wherein a deflection coil is driven by a current amplification method during a scanning period, and a pulse driving method is driven during a blanking period.