JPH04114589A - Dynamic focus circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is compatible with multi-scanning of CRT displays, and achieves good focusing performance over the entire image display area even if the scanning frequency changes. Regarding a dynamic focus circuit for.

[Conventional technology]

The conventional dynamic focus circuit is disclosed in Japanese Patent Application Laid-open No. 63-2.
Horizontal synchronization signal as described in Publication No. 60365.

Generates a parabolic wave by double integrating from the vertical synchronization signal,
These are added and amplified, and in a free lag transformer,
It was superimposed on the DC voltage and applied to the focus electrode of the CRT.

[Problem to be solved by the invention]

Conventional dynamic focus circuits are compatible with only a single scanning frequency, and there is a problem in that when the scanning frequency changes, the parabolic wave amplitude also changes.

SUMMARY OF THE INVENTION An object of the present invention is to provide a dynamic focus circuit in which the frequencies and phases are consistent and the parabolic wave amplitude is always constant even when the scanning frequency changes.

[Means to solve the problem]

The dynamic focus circuit of the present invention triggers one of the pulses as a reference for the horizontal period and the vertical period (for example, a blanking pulse for the horizontal period, a pump-up signal pulse for the vertical period, etc.). As a one-shot multi-noise ibrator, the pulse width can be adjusted, and by adjusting the pulse width, the edge where the phase changes is used as a trigger, J, -K
Divide the frequency into two using a flip-flop, etc. to create a square wave. On the other hand, it has a PLL circuit consisting of a voltage-controlled oscillator (VCO) that simultaneously oscillates a triangular wave and a square wave, a phase comparator, and a loop filter. , and the square wave generated from the reference pulse of the deflection circuit, and control the oscillation sub-leg voltage of ■C○ so that the two frequencies and phases match. the result,
■The triangular wave output from CO is compared to the ground level.
Shift the DC level so that the top and bottom are symmetrical and multiply! iW
By squaring this, we obtain a parabolic wave. The circuit configuration is such that horizontal and vertical periodic parabolic waves generated by these means are added, amplified, and then applied to the focus electrode.

[Effect]

In the present invention, by adopting the method shown in the means for solving the problem, the frequency 1 phase of the parabolic wave matches the scanning frequency, and the amplitude of the parabolic wave is also constant, so that the display can be multi-scanned. However, always
This is a dynamic focus circuit that achieves good focus performance.

〔Example〕

Embodiments of the dynamic focus circuit of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the configuration of one embodiment.

A pulse width adjustment circuit 1 adjusts the pulse width of the horizontal blanking pulse, and outputs this output to a frequency divider circuit 2 such as a flip-flop. The frequency divider circuit 2 divides the frequency of the input pulse into two and converts it into a square wave with twice the period. The phase comparator 3 compares the frequency and phase of this square wave and the square wave output from vC05, and outputs information on the difference to the loop filter 4. The loop filter 4 converts the output of the phase comparator 3 into D
Convert it to C voltage and add it as the frequency control voltage of ■C05. The VCO 5 outputs a triangular wave and a square wave with a frequency corresponding to this frequency control voltage, the triangular wave is input to the DC level shift circuit 6, and the square wave is input to the phase comparator 3. Phase comparator 3. Loop filter 4. The three VC○5 form a phase-locked loop (hereinafter referred to as PLL), and when the loop converges, the triangular wave and square wave outputs of VCO5 become square waves output from the frequency divider 2 to the phase comparator 3. It has the same frequency and phase as . The triangular wave output of the VCO 5 is input to a DC level shift circuit 6 and converted into a triangular wave that is vertically symmetrical with respect to the GND level. This output is input to both the X and Y inputs of the multiplier 7, and the output X and Y, that is, the triangular wave, are squared to obtain a parabolic wave.

The pulse width adjustment circuit 8 adjusts the pulse width of the vertical pump-up voltage, and outputs this output to a frequency divider circuit 9 such as a flip-flop. The frequency divider circuit 9 divides the frequency of the input pulse by two, converting it into a square wave with twice the period. The phase comparator 10 is
This square wave and the square wave output from the VCO 12 are compared in frequency and phase, and information on the difference is output to the loop filter 11. The loop filter 11 converts the output of the phase comparator 10 into a DC voltage and applies it as a frequency control voltage to the VCO 12 . (2) C○ 12 outputs a triangular wave and a square wave with a frequency corresponding to this frequency control voltage, the triangular wave is input to the DC level shift circuit 13, and the square wave is input to the phase comparator 10. This phase comparator 10. Loop filter 11.
The three VCOs 12 form a PLL, and when the loop converges, the triangular wave and square wave outputs of the VCO 12 have the same frequency and the same phase as the square waves output from the divide-by-half circuit 9 to the phase comparator 10. The triangular wave output of the VCO 12 is input to a DC level shift circuit 13 and converted into a triangular wave symmetrical above and below with respect to the GND level. This output is multiplier】4's X,
Input to both Y inputs and square the X and Y outputs, that is, triangular waves, to obtain a parabolic wave.

The output of the multiplier 7, a horizontal parabolic wave, and the output of the multiplier 14, a vertical parabolic wave, are input to an adding circuit 15, and the added output is input to an output circuit 16. The output circuit 16 amplifies the parabolic wave voltage to a predetermined level, and this output is sent to the flyback transformer 18 via the coupling capacitor 17.
Generate with . Superimposed on DC focus voltage, CRT19
is applied to the focus electrode 20 of.

Next, the operation of the dynamic focus circuit of the present invention will be explained. The horizontal blanking signal shown in FIG. 2(a) is input to the pulse width adjustment circuit 1, and the vertical pump-up voltage shown in FIG. 2(b) is input to the pulse width adjustment circuit 8, and the output is as follows. In both cases, a rectangular wave as shown in FIG. 2(c) is obtained. This falling edge can be shifted by changing the time constant of the one-shot multivibrator used in the pulse width adjustment circuit 1.8. This falling edge is divided into two by the frequency divider circuit 2.9, converting it into a square wave as shown in FIG. 2(d), and the phase comparator 3. 0 phase comparator 3, 101 loop filter 4. input to lO. LL VC○5. When the loop converges, the triangular wave output from VCO 5°12 has the same frequency and period as the square wave output from the divide-by-half circuit 2.9, as shown in Figure 2 (e). becomes. This triangular wave is input to the DC level shift circuit 6゜13, as shown in Fig. 2(f).
As shown in the figure, the triangular wave is symmetrical above and below with respect to the GND level. This triangular wave is input to a multiplier 7.14 and squared to obtain a parabolic wave as shown in FIG. 2(g). After this, add the horizontal and vertical parabolic waves obtained in this way.

It is amplified, superimposed on the DC focus voltage generated by the flyback transformer, and applied to the focus electrode 20 of the CRT 19.

In addition, in the embodiment, as a reference pulse, in the horizontal period,
Although the blanking pulse has been explained, it can also be realized by using a flyback pulse. Similarly, vertical synchronization can also be achieved by using blanking pulses and synchronization signals in addition to the pump-up voltage.

Also, changing the pulse width with the pulse width adjustment circuits 1 and 8 means linearly changing the phase of the parabolic wave.
By adjusting this, it is possible to match the phase of the parabolic wave with the display period.

〔Effect of the invention〕

According to the present invention, even if the scanning frequency changes, the frequency matches the scanning frequency and the phase matches the display period. In addition, it can always generate a parabolic wave with a constant amplitude in both horizontal and vertical periods, and generates a dynamic focus voltage (parabolic wave voltage) that always achieves good focus performance for multi-scan displays. can do.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the dynamic focus circuit of the present invention, and FIG. 2 is a voltage waveform diagram of each part in the dynamic focus circuit of the present invention. 1.8...Pulse width adjustment circuit 2.9...Half frequency divider circuit 3. lO...Phase comparator 4.11...Loop filter 5, 12...■C○6
．． 13... DC level shift circuit 7.14... Multiplier 15... Addition circuit 16
・-・Output circuit 17...Coupling capacitor 1
8...Flyback transformer

Claims (1)

[Claims] 1. The width of the pulse can be adjusted using a one-shot multivibrator using the earlier edge of the pulse that serves as the reference of the deflection circuit as a trigger, and by adjusting the width of the pulse, The edge of the phase change is used as a trigger, and the frequency is divided into two by flip-flip to create a square wave.On the other hand, a phase-locked loop circuit is created using a voltage-controlled oscillator, phase comparator, and loop filter that oscillates a triangular wave and a square wave. The phase comparator compares the square wave oscillated by the voltage controlled oscillator with the square wave generated from the reference pulse of the deflection circuit, and adjusts the oscillation of the voltage controlled oscillator so that the frequencies and phases match. Control the control voltage, as a result, shift the DC level of the triangular wave output from the voltage controlled oscillator so that it is vertically symmetrical with respect to the ground level, and square this using a multiplier to obtain a parabolic wave, By adding and amplifying the horizontal and vertical periodic parabolic waves generated by these means and applying them to the focus electrode, even if the scanning frequency changes,
Since the parabolic wave always has a frequency and phase that match the scanning frequency, and its amplitude is constant, it is configured so that good focusing performance can always be achieved for multi-scan displays. A dynamic focus circuit featuring