JPH07154633A - Dynamic focus circuit - Google Patents

Abstract

PURPOSE:To obtain dynamic focusing voltage having an optimum phase and amplitude at all times corresponding to plural optional horizontal frequencies. CONSTITUTION:The circuit is provided with a frequency-voltage conversion circuit 1, and amplitude control circuits 2, 3 to control amplitude of a horizontal sawtooth wave and a horizontal parabolic wave corresponding to plural optional horizontal frequencies and provided with a superimposition circuit 4 and an amplifier output circuit 5 to apply a dynamic focusing voltage having an optimum phase and amplitude characteristic at all times to a focus electrode 7 of a CRT 6 corresponding to plural optional horizontal frequencies through capacitance coupling.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic focus for improving the focus characteristic of a CRT, and more particularly to a multi-synchronous CRT display and a multi-synchronous projection type video projector device which can cope with arbitrary plural horizontal frequencies. It is suitable.

[0002]

2. Description of the Related Art In recent years, dynamic focus circuits have been
Although a horizontal parabola wave is amplified as the dynamic focus voltage, a phase delay occurs due to the amplifier circuit. Therefore, in order to correct the phase delay, a horizontal sawtooth wave having a constant amplitude is added.

A conventional dynamic focus circuit will be described below. FIG. 4 is a configuration block diagram of a conventional dynamic focus circuit. In FIG. 4, reference numeral 4 is a superposition circuit, and 5 is an amplification output circuit. Reference numeral 6 is a CRT, and 7 is a focus electrode.

The operation of the dynamic focus circuit configured as described above will be described below.
First, the superposition circuit 4 superimposes a horizontal sawtooth wave having a constant amplitude on the horizontal parabolic wave. Then, the superposition circuit 4
The superimposed output waveform is amplified and output by the amplification output circuit 5 to obtain a dynamic focus voltage. CR of the above dynamic focus voltage by capacitor coupling
It is supplied to the focus electrode 7 of T6.

At this time, the phase delay due to the amplifier circuit is corrected by the superimposed horizontal sawtooth wave of constant amplitude.

[0006]

However, the phase delay of the dynamic focus voltage differs depending on the horizontal frequency. Therefore, the circuit described above can only uniquely correct the phase delay, and thus has a drawback that the phase delay of the dynamic focus voltage cannot be optimally corrected in a device that receives arbitrary plural horizontal frequencies. Was there.

In view of the above problems, the present invention provides a circuit for performing optimum phase delay correction corresponding to arbitrary plural horizontal frequencies and always obtaining a dynamic focus voltage having optimum phase and amplitude characteristics. is there.

[0008]

In order to solve the above problems, the dynamic focus circuit of the present invention uses an FV voltage to
Amplitude control of horizontal parabola wave and horizontal sawtooth wave
The two waveforms are superposed by a superposition circuit and obtained as a dynamic focus voltage by an amplification output circuit.

[0009]

According to the present invention, the dynamic focus voltage having the optimum phase and amplitude characteristics can be always obtained in correspondence with a plurality of arbitrary horizontal frequencies by the above structure.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is a frequency-voltage conversion circuit, 2 and 3 are amplitude control circuits, 4 is a superposition circuit, 5 is an amplification output circuit, 6 is a CRT, and 7 is a focus electrode.

The operation of the dynamic focus circuit configured as described above will be described below.
Now, the FV voltage obtained by the frequency-voltage conversion circuit 1 is input to the amplitude control circuits 2 and 3. Amplitude control circuit 2, 3
A horizontal parabola wave and a horizontal sawtooth wave are input to the respective input terminals, and a horizontal parabola wave whose amplitude is controlled by the FV voltage from the amplitude control circuit 2 and a horizontal sawtooth wave whose amplitude is controlled by the FV voltage by the amplitude control circuit 3. 2 above
The two waveforms are superposed by the superposition circuit 4, and the dynamic focus voltage obtained through the amplification output circuit 5 is supplied to the focus electrode 7 of the CRT 6 by capacitor coupling.

The amplitude control circuit 3 is a circuit for determining the amplitude of the horizontal sawtooth wave necessary for correcting the phase delay of the dynamic focus voltage. By multiplying the FV voltage by the horizontal sawtooth wave of constant amplitude, the horizontal frequency It outputs a horizontal sawtooth wave whose amplitude is controlled according to. The amplitude control circuit 2 is a circuit that adjusts the amplitude change of the superimposed waveform due to the change of the amplitude of the horizontal sawtooth wave by variably controlling the amplitude of the horizontal parabolic wave.
By multiplying the voltage and the horizontal parabolic wave having a constant amplitude, and further subtracting the horizontal parabolic wave having a constant amplitude, a horizontal parabolic wave whose amplitude is controlled according to the horizontal frequency is output.

The phase delay of the dynamic focus voltage changes depending on the horizontal frequency. Here, if the amplitude of the horizontal sawtooth wave is controlled according to the horizontal frequency, the phase delay of the dynamic focus voltage can be optimally corrected. Therefore, if the amplitude of the horizontal sawtooth wave is controlled by the amplitude control circuit 2 in accordance with a plurality of arbitrary horizontal frequencies, the phase delay is corrected in accordance with a plurality of arbitrary horizontal frequencies, and dynamics having optimum phase characteristics are always obtained. The focus voltage can be obtained.

The relationship diagrams of the output voltage waveforms of the dynamic focus circuit are shown in FIGS. 2 shows the case where the horizontal frequency is high (for example, the horizontal frequency is 65 kHz), and FIG. 3 shows the case where the horizontal frequency is low (for example, the horizontal frequency is 15.75 kHz).

However, since the phase delay of the dynamic focus voltage is corrected by superimposing the horizontal sawtooth wave on the horizontal parabolic wave, if the horizontal parabolic wave has a constant amplitude,
The amplitude of the superimposed waveform changes as the amplitude of the horizontal sawtooth wave changes. Therefore, the amplitude of the dynamic focus voltage changes according to the horizontal frequency. Therefore, the amplitude control circuit 2 also controls the amplitude of the horizontal parabolic wave in accordance with a plurality of arbitrary horizontal frequencies to control the amplitude of the superimposed waveform.

As described above, according to this embodiment, the frequency-
By providing the voltage conversion circuit 1 and the amplitude control circuits 2 and 3, it becomes possible to always obtain a dynamic focus voltage having optimum phase and amplitude characteristics with respect to arbitrary plural horizontal frequencies.

[0018]

As described above, according to the present invention, by providing the circuit for generating the FV voltage and the circuit for controlling the amplitude by the FV voltage, the optimum phase and amplitude characteristics are always obtained with respect to arbitrary plural horizontal frequencies. It is intended to realize an excellent dynamic focus circuit capable of obtaining a dynamic focus voltage having

[Brief description of drawings]

FIG. 1 is a configuration block diagram of a dynamic focus circuit according to an embodiment of the present invention.

FIG. 2 is a waveform diagram of each part when the horizontal frequency in FIG. 1 is high.

FIG. 3 is a waveform diagram of each part when the horizontal frequency in FIG. 1 is low.

FIG. 4 is a configuration block diagram of a conventional dynamic focus circuit.

[Explanation of symbols]

 1 Frequency-voltage conversion circuit 2 Amplitude control circuit (horizontal parabolic wave) 3 Amplitude control circuit (horizontal sawtooth wave) 4 Superposition circuit 5 Amplification output circuit 6 CRT 7 Focus electrode

Claims (1)

[Claims] 1. A circuit for generating a voltage (hereinafter referred to as an FV voltage) that increases in an increasing function with respect to a change in horizontal frequency, a circuit for amplitude controlling a horizontal parabolic wave by the FV voltage, and a horizontal sawtooth wave. The dynamic focus voltage output by the circuit that controls the amplitude by the FV voltage, the circuit that superimposes the waveforms output from the two amplitude control circuits, and the circuit that amplifies and outputs the superimposed waveforms is connected to the CRT by capacitor coupling. A dynamic focus circuit designed to be supplied to the focus electrode.