JPH06113163A - Picture amplitude controller - Google Patents

Abstract

PURPOSE:To provide a picture amplitude controller in which the amplitude and the variable range of a picture become constant with the same amplitude control voltage even if the frequency of an inputted synchronizing signal changes. CONSTITUTION:A frequency/duty ratio conversion pulse generation circuit 25 generating a pulse having a duty ratio proportional to the frequency of the inputted synchronizing signal, a transistor 13 and a resistor 14, which invert the output pulse of the frequency/duty ratio conversion pulse generation circuit 25, change a wave height value by control voltage 12 and output it, and a smoothing circuit 15 smoothing output from the transistor 13 and the resistor 14 are provided in the picture amplitude controller.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image amplitude control device for controlling an image amplitude and an amplitude variable range.

[0002]

2. Description of the Related Art Conventionally, an image amplitude control device has been used for a multi-scan type display or the like. The vertical amplitude control device, which is one of the vertical amplitude control device and the horizontal amplitude control device, which constitutes the conventional image amplitude control device, will be described below. Conventionally, a vertical amplitude control device corresponding to a wide range of vertical synchronizing signal frequencies has a circuit configuration as shown in FIG. In FIG. 4, 8 is a vertical frequency discriminating circuit for discriminating the frequency of the input vertical synchronizing signal,
It is composed of a gate array, a microcomputer, a frequency-voltage converter, a comparator, and the like. 1n are amplitude control voltage generators that generate amplitude control voltages corresponding to different vertical sync signal frequencies f _V (f1, f2, ... fn), 2 are transistors, 3 are emitter resistors, and 4 are capacitors. , 9
A sawtooth wave generation circuit, 10 is a vertical output circuit, 5 is a vertical deflection coil, 6 is a capacitor, and 7 is a resistor. Reference numeral 11 denotes an amplitude control voltmeter 1a according to the signal from the vertical frequency discrimination circuit 8 corresponding to the frequency f _V of the input vertical synchronizing signal.
Electronic switches for switching 1b ... 1n.

The operation of the conventional vertical amplitude control device will be described below. First, the sawtooth wave generation circuit 9 and the vertical output circuit 1
Regarding 0, the operation will be described. The sawtooth wave generation circuit 9 charges the capacitor 4 with a constant current at the cycle of the vertical synchronizing signal, and the sawtooth wave voltage E _{lamp is} applied to both ends of the capacitor 4.
Occurs. That is, if the capacity of the capacitor 4 is C, the constant current for charging the capacitor 4 is I _charge , the period of the vertical synchronizing signal is T _V , and the frequency of the vertical synchronizing signal at that time is f _V , the sawtooth voltage E _lamp is (equation 1). ).

[0004]

[Equation 1]

At this time, since the sawtooth wave generating circuit 9 is composed of a current mirror circuit, the constant current I _charge is equal to the emitter current I _E of the transistor 2,
The sawtooth voltage E _lamp is ( _Equation 2).

[0006]

[Equation 2]

The vertical output circuit 10 has a sawtooth voltage E
_{The lamp} is amplified with a certain gain G _V to generate the deflection current I _DEF . Therefore, by controlling the amplitude of the sawtooth wave voltage E _lamp, the amplitude of the image can be controlled.

Next, the vertical frequency discrimination circuit 8 and the amplitude control
The control voltage will be described. Multi-scan type cathode ray tube
Frequency of vertical sync signal input on display
Number f _V Are widespread, so different vertical sync signals
Frequency f_V Vertical amplitude and variable amplitude identical in
To obtain the range, the constant current I of the sawtooth wave generation circuit 9
_chargeIs the frequency f of the vertical sync signal_V Change in proportion to
Need to This constant current I_chargeOf the transistor 2
Base voltage (amplitude control voltage) is E_CONT, Emitter resistance 3
The resistance value of R_E Then, it becomes (Equation 3).

[0009]

[Equation 3]

That is, in order to change the constant current I _charge , it is necessary to change the amplitude control voltage E _CONT . When the amplitude control voltage E _CONT is changed, the sawtooth wave voltage E _lamp becomes ( _Equation 4).

[0011]

[Equation 4]

That is, as shown in (Equation 3), in order to obtain the same vertical amplitude and variable amplitude range for the frequency f _V of a wide range of vertical synchronizing signals, the amplitude control voltage E _{CONT is set} to It must be controlled so as to be proportional to the frequency f _V. In order to perform this control, the vertical frequency discriminating circuit 8 discriminates the frequency f _V of the input vertical synchronizing signal and switches the electronic switch 11 to obtain the same vertical amplitude and amplitude variable range. 1a, 1b, ... 1n are selected in proportion to the frequency f _V of the input vertical synchronizing signal.

[0013]

However, in the above-mentioned conventional structure, separate amplitude control voltage generators 1a, 1b ... 1n must be prepared and supplied corresponding to the frequency f _V of the input vertical synchronizing signal. It had the drawback of not becoming.

Further, in a digital type control system using a microcomputer, a gate array, a memory, etc. for various control of an image including vertical amplitude control, in order to obtain the same vertical amplitude and variable amplitude range, a vertical synchronizing signal Frequency f
It is necessary to hold the control data for generating an amplitude control voltage E _{CO NT} according to _V, the data size of the entire system becomes large. For example, f _V = 50H
When the value of the control data is 32 to 64 when z, the value of the control data is 64 to 64 at f _V = 100 Hz.
128, which is 32 as data for the entire system
It was necessary to hold up to ~ 128. Furthermore, when the frequency f _V of the vertical synchronizing signal is different, the vertical amplitude change width per step of the control data is also different.

[0015]

In order to solve the above problems, the present invention provides a frequency-duty ratio conversion pulse generating circuit for generating a pulse having a duty ratio proportional to the frequency of an input vertical synchronizing signal, A transistor for inverting the pulse output from the frequency-duty ratio conversion pulse generation circuit and a smoothing circuit for smoothing the output from the transistor are provided.

[0016]

With this configuration, even if the frequency of the input synchronizing signal changes, the image can have the same amplitude.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an entire display using an image amplitude control device according to an embodiment of the present invention. In FIG. 1, 16 is a signal processing circuit that changes the brightness and color of the screen by changing the amplitude of R, G, B video signals sent from a computer, and 17 is a horizontal synchronization signal and a vertical synchronization signal. A synchronization signal processing circuit for determining and processing the input state and sending it to each block, 18 a horizontal deflection circuit for deflecting the electron beam in the horizontal direction, 19 a vertical deflection circuit for deflecting the electron beam in the vertical direction, 21 Is a user control device composed of a semi-fixed resistor or the like, which allows the user to adjust the vertical amplitude, and 20 is a user control device 21.
A control pulse generation circuit for synthesizing a voltage from the control pulse and a control pulse generated from a vertical synchronizing signal, 22 an electron gun for emitting an electron beam, 23 a deflection coil for deflecting the electron beam in horizontal and vertical directions, 24 Is a cathode ray tube that changes an electric signal into a change in light and projects it on a fluorescent screen.

FIG. 2 is a block diagram of a vertical amplitude control device which constitutes an image amplitude control device in one embodiment of the present invention. In FIG. 2, reference numeral 25 is a frequency-duty ratio conversion pulse generation circuit for outputting a pulse having a duty ratio proportional to the frequency f _V of the vertical synchronizing signal input from the outside, 1
2 is a control voltage which is D / A converted from an analog amount or digital data and is variable for the user to adjust the amplitude of the image. 14 is a resistor. 13 is a transistor which inverts the pulse from the frequency-duty ratio conversion pulse generation circuit 25. Then, a circuit that changes the peak value by the control voltage 12 is configured. Reference numeral 15 is a smoothing circuit for smoothing the output of the circuit composed of the transistor 13 and the resistor 14. Since the sawtooth wave generation circuit 9 and its peripheral circuits are the same as those in the prior art, the same reference numerals are given and their description is omitted. The operation of the vertical amplitude control device that constitutes the image amplitude control device configured as described above will be described.

The frequency-to-duty ratio conversion pulse generating circuit 25, as shown in FIG. 3A, has a vertical synchronizing signal (V _sync ).
In synchronism with the frequency f _V , a pulse whose Low level has a constant width (k) and whose period is the same as that of the vertical synchronizing signal is generated. This pulse is inverted by the circuit composed of the transistor 13 and the resistor 14 as shown in FIG. 3B, and the peak value is converted into the same pulse as the control voltage 12. Therefore, the output voltage E _cont2 of the smoothing circuit 15 becomes ( _Equation 5).

[0020]

[Equation 5]

Therefore, the sawtooth wave voltage E _lamp for controlling the image amplitude becomes ( _Equation 6) _instead of ( _Equation 4).

[0022]

[Equation 6]

Therefore, the sawtooth wave voltage E _lamp has the same control voltage 12 regardless of the frequency f _V of the vertical synchronizing signal,
The same vertical amplitude and vertical amplitude variable range can be obtained.

Although the vertical amplitude control has been described in the present embodiment, the same horizontal amplitude and horizontal amplitude variable range can be similarly obtained in the horizontal amplitude control regardless of the frequency of the horizontal synchronizing signal.

[0025]

According to the present invention, since the same vertical amplitude and the same vertical amplitude variable range can be obtained regardless of the frequency of the sync signal, different amplitude control voltages are used for different sync signal frequencies. There is no need to increase the data size of the control data even in a digital type control system that adjusts the amplitude of the image by changing the amplitude control voltage by using a microcomputer, gate array, memory, etc. It is possible to make the amplitude variable width per step constant, so that the performance and operability can be improved and the function can be realized at a low price.

[Brief description of drawings]

FIG. 1 is a block diagram showing an entire display using an image amplitude control device according to an embodiment of the present invention.

FIG. 2 is a block diagram of a vertical amplitude control device that constitutes an image amplitude control device according to an embodiment of the present invention.

FIG. 3 is an operation explanatory diagram of a vertical amplitude control device which constitutes an image amplitude control device according to an embodiment of the present invention.

FIG. 4 is a block diagram of a vertical amplitude controller that constitutes a conventional image amplitude controller.

[Explanation of symbols]

 9 sawtooth wave generation circuit 12 control voltage 13 transistor 14 resistance 15 smoothing circuit 25 frequency-duty ratio conversion pulse generation circuit

Claims (1)

[Claims] 1. Pulse generation means for generating a pulse having a duty ratio proportional to the frequency of an input synchronizing signal,
Inverting means for inverting the pulse output from the pulse generating means, smoothing means for smoothing the output from the inverting means, and generating a sawtooth wave by accumulating the output from the smoothing means and supplying it to the deflection coil. An image amplitude control device comprising a sawtooth wave generating means.