JP2000101865A - Dynamic focus circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain stable horizontal scanning at a low cost by using a parabolic voltage across an S-shape correction capacitor in the dynamic focus circuit for a CPT display device having provision for a multi-scan monitor frequency and selecting a boosting ratio of a boosting transformer so as to attain application of a dynamic focus voltage with a small change in a plurality of horizontal scanning frequencies (e.g. about 15 kHz, about 24 kHz and 31 kHz modes). SOLUTION: The dynamic focus circuit for a multi-scan monitor horizontal scanning frequency CPT display device is provided with a boosting transformer T1 having terminals providing different boosting ratios that are selected corresponding to a change in the horizontal scanning frequency and with a plurality of S-shape correction capacitors C2, C2A, C2B that are selected corresponding to a change in the horizontal scanning frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a multi-scan monitor having a plurality of horizontal scanning frequencies (for example, about 15 KH).
Z, about 24KHz and 31KHz mode) compatible CPT (C
The present invention relates to a dynamic focus circuit capable of performing stable horizontal scanning even when the horizontal scanning frequency is switched in a color picture tube (display) display.

[0002]

2. Description of the Related Art For example, a CP corresponding to a single horizontal scanning frequency is used.
In the case of the T display, the dynamic focus circuit shown in FIG. 3, that is, the parabolic waveform generated in the S-shaped correction capacitor C2 is boosted by the boosting transformer T1 via the coupling capacitor C3 to obtain a high-voltage parabolic waveform, and the coupling is performed. Stable horizontal scanning can be performed by supplying a focus electrode (not shown) via the capacitor C4. However, such a dynamic focus circuit can be provided at a plurality of horizontal scanning frequencies (for example, about 15 KH).
Z, about 24KHz and 31KHz mode) compatible CPT (C
color Picture Tube) When used as a dynamic focus circuit of a display, S
Since the peak value of the parabola waveform generated in the character correction capacitor C2 changes according to each frequency, the dynamic focus voltage fluctuates, so that only an unstable horizontal scan can be performed.

[0003] Therefore, a C signal corresponding to a plurality of horizontal scanning frequencies (for example, about 15 KHz, about 24 KHz, and 31 KHz mode) is used.
As a dynamic focus circuit of a PT (Color Picture Tube) display, a dynamic focus circuit disclosed in FIG. 4 has been conventionally developed. In the dynamic focus circuit of FIG. 4, a parabolic waveform that does not change with each horizontal scanning frequency is formed by a parabolic waveform circuit, the waveform is amplified by an amplifier circuit, and a dynamic focus voltage is obtained by using a step-up transformer. .

Accordingly, in the dynamic focus circuit as shown in FIG. 4, the scanning fluctuation for each horizontal scanning frequency is smaller than that in the dynamic focus circuit of FIG.
A parabolic wave generation circuit and an amplifier circuit are required, and the configuration of the dynamic focus circuit becomes very complicated, resulting in an increase in cost.

[0005]

In the dynamic focus circuit of FIG. 3, the parabolic wave generation circuit and the amplifier circuit can be eliminated from the dynamic focus circuit of FIG. 4 by using the parabolic wave of the voltage across the S-shaped correction capacitor. Since the peak value of the parabolic wave varies depending on the horizontal scanning frequency, the voltage across the S-shaped correction capacitor is difficult to use for dynamic focus in a multi-scan monitor horizontal scanning frequency compatible CPT display. On the other hand, the dynamic focus circuit of FIG. Although the problem shown in FIG. 3 can be solved by adoption, a parabolic wave generation circuit and an amplifier circuit are required, and the configuration of the dynamic focus circuit becomes very complicated, which increases the cost.

In order to solve the above-mentioned problem, the present invention uses a parabolic wave of the voltage across the S-shaped correction capacitor in a dynamic focus circuit of a CPT display compatible with a multi-scan monitor frequency, and switches the step-up ratio of a step-up transformer. , Multiple horizontal scanning frequencies (eg about 15 KHz, about 24 KHz and 31 KHz modes)
Accordingly, it is possible to provide an inexpensive dynamic focus circuit which can supply a dynamic focus voltage with little change and can perform stable horizontal scanning.

[0007]

First, in a dynamic focus circuit of a multi-scan monitor horizontal scanning frequency CPT display, a step-up transformer having terminals with different step-up ratios which can be switched in response to a change in the horizontal scanning frequency. And a plurality of S-shaped correction capacitors that can be switched according to changes in the horizontal scanning frequency.

Second, the switching of the terminals provided in the step-up transformer is performed by a switch that operates according to the horizontal scanning frequency. Third, the plurality of S-shaped correction capacitors are switched so as to be switched according to a horizontal scanning frequency. Fourthly, the switching of the terminals provided in the step-up transformer and the switching of the plurality of S-shaped correction capacitors are switched according to the horizontal scanning frequency and are configured to be linked.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a dynamic focus circuit according to the present invention will be described in detail with reference to FIGS. In the dynamic focus circuit according to the present invention,
As shown in FIG. 1, the T1 step-up transformer is provided with several terminals having different step-up ratios so that the horizontal scanning frequency (for example, about 15K
HZ, about 24 KHz and 31 KHz modes), by switching the terminal of the switch SW1 so as to change the step-up ratio of the step-up transformer T1, and to apply the horizontal scanning frequency to the S-shaped correction capacitor C2. (For example, about 15 KHz, about 24 KHz, and 31 KHz mode), S-shaped correction capacitors C2A and C2B that are switched in response to the operation of the switch SW1 that is switched in parallel are configured in parallel.

The operation of the above dynamic focus circuit will be described below. The parabolic waveform generated in the S-shaped correction capacitor C2 is input to the step-up transformer T1 via the coupling capacitor C3 and the switch SW1.
The step-up transformer T1 is provided with several terminals having different step-up ratios and is switched to a specific terminal by the switch SW1 according to the horizontal scanning frequency. Therefore, the step-up ratio of the step-up transformer T1 changes according to each horizontal scanning frequency. .

As shown in FIG. 2, when the step-up ratio of the step-up transformer T1 is switched, a slight change occurs in the peak value of the parabolic waveform near the frequency. The S-shaped correction capacitors C2A and C2B provided in parallel with the S-shaped correction capacitor C2 are also operated in accordance with the switching, so that the S-shaped correction capacitors C2C, 2A and C2B can be accurately adjusted even if the horizontal scanning frequency changes. Since the change is corrected, the change in the parabola waveform is small, the dynamic focus voltage is stabilized, and the change can be supplied to a focus electrode (not shown) via the coupling capacitor C4.

[0012]

In the dynamic focus circuit according to the present invention, the boosting transformer of T1 is provided with several terminals having different boosting ratios, and the terminal of the switch SW1 is switched in accordance with the horizontal scanning frequency, whereby the boosting of the boosting transformer T1 is performed. The ratio can be changed, and S-shaped correction capacitors C2A and C2B that switch according to the operation of the switch SW1 are connected in parallel to the S-shaped correction capacitor C2. Even if the parabolic waveform generated in the S-shaped correction capacitor C2 changes, the variation of the dynamic focus voltage can be reduced, and the parabolic wave generation circuit and the amplifier circuit can be reduced. Reduced circuit can reduce power consumption, components, cost, and mounting density. That.

[Brief description of the drawings]

FIG. 1 is a dynamic focus circuit of a multi-scan monitor horizontal scanning frequency compatible CPT display according to the present invention.

FIG. 2 is a diagram for explaining a change in a peak value of a parabolic waveform when the boost ratio of the boost transformer is switched.

FIG. 3 is a dynamic focus circuit of a single horizontal scanning frequency CPT display.

FIG. 4 is a dynamic focus circuit of a conventional multi-scan monitor horizontal scanning frequency compatible CPT display.

[Explanation of symbols]

 T1 Step-up transformer SW1 Switch C2, C2A, C2B S-shaped correction capacitor C3 Coupling capacitor C4 Coupling capacitor

Claims (4)

[Claims] 1. A multi-scan monitor horizontal scanning frequency C
In a dynamic focus circuit of a PT display, a step-up transformer having terminals with different step-up ratios that can be switched in response to a change in horizontal scanning frequency, and a plurality of S-shaped switches that can be switched in response to a change in horizontal scan frequency A dynamic focus circuit comprising a correction capacitor. 2. The dynamic focus circuit according to claim 1, wherein switching of terminals provided in said step-up transformer is performed by a switch that operates according to a horizontal scanning frequency. 3. The dynamic focus circuit according to claim 1, wherein the plurality of S-shaped correction capacitors are switched in accordance with a horizontal scanning frequency. 4. The apparatus according to claim 1, wherein the switching of the terminal provided on the step-up transformer and the switching of the plurality of S-shaped correction capacitors are switched in accordance with a horizontal scanning frequency and are interlocked. The dynamic focus circuit according to claim 1, 2, or 3.