JPH067628Y2 - Horizontal screen position control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a horizontal screen position control circuit of a cathode ray tube display monitor capable of supporting a plurality of different scanning modes.

[Prior Art] A conventional example of a horizontal screen position control circuit of this type is shown in FIG.

In the horizontal screen position control circuit 100, 1 is a pseudo horizontal synchronizing signal output circuit having a monostable multivibrator therein.

When the horizontal synchronizing signal HD as shown in FIG. 6 is input to the pseudo horizontal synchronizing signal output circuit 1, the delay determined by the time constant of the charging / discharging circuit 7 formed by the variable resistor VR ₁ and the capacitor C _1. Pseudo horizontal synchronizing signal H delayed by time T ₃
D'is output.

The horizontal screen position is controlled by the pseudo horizontal synchronizing signal HD '.

On the other hand, in Japanese Patent Laid-Open No. 63-136773, as shown in FIG. 7, the frequency-voltage converter 201 converts the frequency of the horizontal synchronizing signal HD into a voltage V, and the voltage V is encoded by an encoder 202. , A technique is disclosed in which the variable resistors VR ₁ and VR ₂ are switched by the multiplexer 203 according to the code.

[Problems to be Solved by the Invention] In the conventional horizontal screen position control circuit 100 shown in FIG.
The delay time T ₃ can be adjusted by the variable resistor VR ₁ .

However, each time the frequency of the horizontal synchronizing signal HD changes, there is a problem that the variable resistor VR ₁ must be operated to adjust the horizontal screen position to an optimum position.

On the other hand, the conventional horizontal screen position control circuit 200 shown in FIG.
Then, if the variable resistors (for example, VR ₁ and VR ₂ ) of only the kinds of frequencies that can be used are prepared and adjusted in advance, the above problems will be eliminated.

However, since a high-frequency oscillation waveform is applied to these variable resistors (for example, VR ₁ and VR ₂ ), external noise is apt to be weighted through the lead wires and the conductive pattern of the circuit board, and these variable resistors ( For example, when VR ₁ and VR ₂ are extended from the circuit board, the screen may be disturbed and various malfunctions may occur, so these variable resistors (for example, VR ₁ and VR ₂ ) should be placed near the circuit board. However, there is a problem that it cannot be installed at a position convenient for adjusting the horizontal screen position.

This problem also applies to the horizontal screen position control circuit 100 shown in FIG.

Therefore, the object of the present invention is to solve the above-mentioned problems and to adjust the horizontal screen position automatically according to the frequency of the horizontal synchronizing signal HD so as to be the optimum position of the screen and to adjust the variable resistor. It is to provide a horizontal screen position control circuit that can be installed at a convenient position.

[Means for Solving the Problems] The horizontal screen position control circuit of the present invention generates a pseudo horizontal sync signal by delaying the horizontal sync signal by a delay time determined by the time constant of the charging / discharging circuit formed by a resistor and a capacitor. A horizontal-screen position control circuit that controls a horizontal screen position by outputting a frequency-voltage conversion circuit that receives a horizontal synchronizing signal and outputs a first DC voltage corresponding to the frequency of the horizontal synchronizing signal; DC voltage of 1 is input,
A voltage-current conversion circuit for supplying a current according to the voltage value of the first DC voltage to the charge / discharge circuit as a charging current, wherein the voltage-current conversion circuit divides a DC constant voltage. A variable resistor and a current output circuit for inputting the divided voltage and the first DC voltage and outputting a current corresponding to the voltage of both to the charge / discharge circuit It is what

In the above configuration, it is preferable to prepare a plurality of variable resistors corresponding to a plurality of different scanning modes, and to automatically select one corresponding to the scanning mode from among them.

Further, it is preferable that the variable resistor is installed at a position convenient for adjustment operation, even if the variable resistor is located away from the circuit board having the current output circuit.

[Operation] In the horizontal screen position control circuit of the present invention, the frequency-voltage conversion circuit converts the voltage into the first DC voltage according to the frequency of the horizontal synchronizing signal, and the voltage-current conversion circuit converts the voltage of the first DC voltage. The current is converted into a current according to the value, and the current is supplied as a charging current to a charging / discharging circuit that determines the delay time of the pseudo horizontal synchronizing signal. This is nothing but changing the time constant of the charging / discharging circuit. That is, the delay time changes according to the frequency of the horizontal synchronizing signal. Therefore, it is not necessary to manually adjust the delay time each time the frequency of the horizontal synchronizing signal changes.

It is possible to adjust the position to the optimum position in advance by operating the variable resistor that divides the DC constant voltage and adjusts the current supplied from the voltage-current conversion circuit by the voltage division.

Further, since a high frequency oscillation waveform is not applied to this variable resistor, it can be installed at a position away from the circuit board and convenient for adjustment operation without being affected by external noise.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. However, the present invention is not limited to this.

FIG. 1 is a circuit diagram showing a first embodiment of the present invention. In the figure, HD is a horizontal synchronizing signal, HD 'is a pseudo horizontal synchronizing signal obtained by delaying the horizontal synchronizing signal HD by a predetermined time, 1 is a pseudo horizontal synchronizing signal output circuit, and 7 is a charging / discharging circuit. It is similar to the corresponding components of circuits 100, 200.

Reference numeral 2 is a frequency-voltage conversion circuit, 3 is a voltage-current conversion circuit, and these are constituent elements that have not existed in the past.

Now, when the horizontal synchronizing signal HD having the period T ₁ as shown in FIG. 2 is inputted to the frequency-voltage conversion circuit 2, the monostable multivibrator 4 is triggered and the pulse width T as shown in FIG. _Two pulses P are output. The pulse width T ₂ is
Maximum horizontal deflection frequency supported by display monitor
It is set to be substantially equal to the period T ₁ of the horizontal synchronizing signal HD at the time of _MAX . The pulse P is smoothed by the resistor R ₉ and the capacitor C ₄ and output as a DC voltage V ₁ .

As shown in FIG. 3, this DC voltage V ₁ has a value that is inversely proportional to the frequency of the horizontal synchronizing signal HD up to the maximum horizontal deflection frequency _MAX that the display monitor can support, and has a constant value V _BE above that. .

The DC voltage V ₁ is input to the base of the transistor TR ₃ via the resistor R ₇ of the voltage-current conversion circuit 3. When the DC voltage V ₁ increases or decreases, the collector current Ic of the transistor TR ₂ also increases or decreases. That is, the change in the DC voltage V ₁ is converted into the change in the collector current Ic.

When the collector current Ic of the transistor TR ₂ increases or decreases, the charging current to the capacitor C ₁ of the charging / discharging circuit 7 composed of the resistor R ₁ and the capacitor C ₁ increases or decreases, and the pseudo horizontal synchronizing signal HD ' The delay time T ₃ increases or decreases.

Therefore, after all, when the horizontal deflection frequency increases or decreases (which is, of course, in the region below the maximum horizontal deflection frequency _MAX ), the pseudo horizontal synchronization signal HD '
Delay time T _{3 of} will decrease or increase.

Thus, the horizontal screen position control circuit 10 automatically controls the horizontal screen position according to the horizontal deflection frequency.

Further, the collector current Ic can be adjusted by the variable resistor VR ₂ and the delay time T ₃ can be adjusted to an optimum value. However, since direct current is only applied to the variable resistor VR ₂ , external noise is generated. It will not be affected by, and can be installed at a position away from the circuit board that is convenient for adjustment operations.

Next, FIG. 4 is a circuit diagram showing a second embodiment of the present invention. Incidentally, for convenience of explanation, the same components as those shown in the first embodiment are designated by the same reference numerals, and the explanation thereof will be omitted.

In the horizontal screen position control circuit 20, instead of the variable resistor VR ₂ of the horizontal screen position control circuit 10 of FIG.
A variable resistor VR ₃ and a variable resistor VR ₄ are provided.

Further, a mode signal generation circuit 5 for determining the scanning mode based on the horizontal synchronizing signal HD and the vertical synchronizing signal VD and generating the mode signal I or the mode signal II is provided.

The mode signals I and II are positive DC voltages and make either of the transistors TR ₅ or TR ₆ conductive.

Therefore, either one of the variable resistors VR ₃ and VR ₄ is selected by this, and if the horizontal screen position is optimally adjusted in advance by the variable resistor corresponding to each scanning mode, the scanning mode to be input can be obtained. Therefore, the horizontal screen position is automatically controlled to be optimum.

[Advantage of Invention] According to the present invention, the screen position is automatically controlled according to the frequency of the horizontal synchronizing signal.

In addition, the variable resistor for adjusting the screen position can be installed at a position convenient for operation away from the circuit board.

[Brief description of drawings]

FIG. 1 is a circuit diagram of the first embodiment of the present invention, FIG. 2 is a time chart of horizontal synchronizing signal and pulse, FIG. 3 is a characteristic diagram of horizontal deflection frequency and DC voltage, and FIG. 4 is of the present invention. FIG. 5 is a circuit diagram of a second embodiment, FIG. 5 is a circuit diagram of an example of a conventional circuit, and FIG.
FIG. 7 is a time chart of the horizontal synchronizing signal and the pseudo horizontal synchronizing signal, and FIG. 7 is a circuit diagram of another example of the conventional circuit. (Description of symbols) 10, 20 ... Horizontal screen position control circuit 1 ... Pseudo horizontal synchronization signal output circuit 2 ... Frequency-voltage conversion circuit 3, 3 '... Voltage-current conversion circuit 5 ... Mode signal generation circuit 7 ...... discharge circuit HD ...... horizontal synchronizing signal HD '...... pseudo horizontal synchronous signals _{R 1, R 7, R 9} , R 10, R 11 ...... resistor C _1, C ₄ ...... capacitor VR ₁ to VR ₄ …… Variable resistors TR _{1 to} TR ₆ …… Transistors.

Claims (2)

[Scope of utility model registration request] 1. A horizontal screen position control for controlling a horizontal screen position by outputting a pseudo horizontal sync signal obtained by delaying the horizontal sync signal by a delay time determined by a time constant of a charging / discharging circuit formed of a resistor and a capacitor. In the circuit, a frequency-voltage conversion circuit that receives a horizontal synchronizing signal and outputs a first DC voltage corresponding to the frequency of the horizontal synchronizing signal, and the first DC voltage that is input, and the first DC voltage A voltage-current conversion circuit that supplies a current according to the voltage value of the charge / discharge circuit as a charging current to the charge / discharge circuit, wherein the voltage-current conversion circuit is a variable resistor that divides a DC constant voltage, and A horizontal screen position control circuit comprising: a voltage output and a current output circuit which receives the first DC voltage and outputs a current corresponding to both voltages to the charge / discharge circuit. 2. The horizontal screen position control circuit according to claim 1, wherein a plurality of the variable resistors are provided, and each of them is enabled or disabled according to a mode signal corresponding to a scanning mode. Horizontal screen position control circuit.