JP2000293128A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely prevent destruction of a horizontal output circuit, to shorten a time till a time when a picture posterior to the changeover of resolution is to be stabilized and also to make the designing of a display device to become relatively easy by changing an instruction voltage to a horizontal oscillation circuit linearly or step-by-step. SOLUTION: This display device is provided with a major gate array 9 outputting a changeover signal d1 by detecting that the frequency of a horizontal synchronizing signal a1 is changed over, a horizontal oscillation circuit 3 outputting the horizontal drive signal b1 synchronized with a horizontal synchronizing signal whose frequency is changed over by varying the frequency of the signal according to an F/V value c1 in accordance with the frequency of the inputted horizontal synchronizing signal a1 and a microcomputer 11 and a DAC 13 which change the F/V value c1 toward a target F/V value in accordance with a frequency posterior to the changeover of the horizontal synchronizing signal a1 linearly or step-by-step with a prescribed slope when the changeover signal d1 is outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device for displaying a video signal output from a computer or the like, and more particularly, to a multi-display capable of switching a screen resolution and receiving a horizontal synchronizing signal of various frequencies. The present invention relates to a scan type display device.

[0002]

2. Description of the Related Art A display device used for displaying an image on a computer or the like is a versatile multi-scan capable of supporting various screen resolutions selected by a user such as 640 × 480 dots, 800 × 600 dots, and 1024 × 768 dots. Generally, it is a type.

For example, in such a multi-scan type display device, when the computer switches the screen resolution, the frequency of the horizontal synchronizing signal is switched accordingly, and the horizontal oscillation circuit synchronizes with the frequency of the switched horizontal synchronizing signal. A new horizontal drive signal is generated and supplied to a horizontal output circuit that scans the CRT horizontally. In the horizontal output circuit, a horizontal drive signal from a horizontal oscillation circuit is applied to a base terminal of a horizontal output transistor corresponding to the input stage, and drives a deflection coil for driving a CRT together with a variable + B circuit connected to its collector. It is configured as follows.

The above-described horizontal oscillation circuit is configured to receive an instruction voltage corresponding to the frequency of the switched horizontal synchronizing signal and generate a horizontal drive signal in synchronization with the instruction voltage. When the resolution is changed from (high frequency) to low resolution (low frequency), the frequency of the horizontal drive signal is rapidly changed, so that the following of the variable + B circuit is delayed, and as a result, the collector voltage of the horizontal output transistor rises rapidly. The horizontal output circuit may be destroyed. Therefore, the instruction voltage output to the horizontal oscillation circuit is
For example, the delay is made by a time constant circuit by RC. As a result, the command voltage does not suddenly switch from the original frequency to a voltage corresponding to the frequency after switching.

[0005]

However, the prior art having such a structure has the following problems. That is, by delaying the instruction voltage to the horizontal oscillation circuit, the frequency change of the horizontal drive signal can be changed.
Since the B circuit can sufficiently follow up, the breakdown of the horizontal output transistor can be prevented. On the other hand, the indication voltage rises exponentially due to the delay caused by the time constant circuit. Therefore, if the tracking of the variable + B circuit is taken into consideration, a delay time is unnecessarily long, and there is a problem that the time required for the screen to stabilize when the screen resolution is switched is lengthened.

In addition, there is a problem that it is very difficult to set the time constant because it is necessary to take into consideration variations in RC constituting the time constant circuit and changes with time.

[0007] Even if the same instruction voltage is applied to each horizontal oscillation circuit, the oscillation frequency varies.
This is due to the characteristics of the oscillator inside the horizontal oscillation circuit and the variation of the externally mounted element (RC). For this reason, when the indicated voltage is changed at a uniform rate of change, the time required for the screen to stabilize among the apparatuses varies.

The present invention has been made in view of the above circumstances, and it is possible to reliably prevent the horizontal output circuit from being destroyed by changing the instruction voltage to the horizontal oscillation circuit linearly or stepwise. It is another object of the present invention to provide a display device capable of shortening the time required for the screen to be stabilized after the resolution is switched and making the design relatively easy.

[0009]

The present invention has the following configuration in order to achieve the above object. That is, according to the first aspect of the present invention, in a multi-scan type display device provided with a CRT which is horizontally scanned by a horizontal output circuit, a switching signal is output by detecting that the frequency of the horizontal synchronizing signal has been switched. A horizontal oscillation circuit that outputs to the horizontal output circuit a detection means and a horizontal drive signal that varies in accordance with an instruction voltage corresponding to the frequency of the input horizontal synchronization signal and is synchronized with the horizontal synchronization signal whose frequency has been switched; A control circuit for changing the indicated voltage linearly or stepwise at a predetermined gradient toward a target value corresponding to the frequency after the switching of the horizontal synchronizing signal when a switching signal is output from the detection means; And means.

[0010] The invention described in claim 2 is the same as the claim 1.
In the display device according to the above, the control means,
After changing the command voltage to a tentative target value corresponding to the highest frequency, the command voltage is linearly or stepwise with a predetermined gradient toward a target value corresponding to the frequency after switching of the horizontal synchronization signal. It is characterized by being changed.

[0011] The invention according to claim 3 is based on claim 1.
Or the display device according to 2, wherein the control means sets the gradient of the command voltage according to the difference between the original frequency of the horizontal synchronization signal and the frequency after switching.

The invention described in claim 4 is the first invention.
Or the display device according to 2, wherein a first instruction voltage for causing the horizontal oscillation circuit to oscillate at a first frequency, and a second instruction voltage for causing the horizontal oscillation circuit to oscillate at a second frequency. Command voltage measuring means for measuring a difference between the first command voltage and the second command voltage, and a difference between a first reference command voltage and a second reference command voltage which are preset and serve as references. And a calculating unit for calculating a gradient value of the command voltage based on the ratio of the control voltage, wherein the control unit sets the gradient based on the gradient value.

[0013]

The operation of the first aspect of the invention is as follows. When the frequency of the horizontal synchronization signal is switched and the switching signal is output from the detection means, the control means linearly or instructs the command voltage to be applied to the horizontal oscillation circuit to a target value corresponding to the frequency after the switching at a predetermined slope. Change step by step.
By setting this inclination within a variation value of the frequency that the horizontal output circuit can endure, the horizontal output circuit can be prevented from being broken.

According to the second aspect of the invention, the horizontal linearity is improved by changing the frequency of the horizontal drive signal once to the highest frequency and then to the frequency of the switched horizontal synchronization signal. In this case, it is possible to prevent the capacity of the CS capacitor provided in the horizontal output circuit (generally, a smaller capacity is required when the frequency is higher) from being insufficient during the frequency switching process.

According to the third aspect of the invention, when the difference between the original frequency and the switched frequency is large,
By setting the gradient of the change of the indicated voltage to be larger than when the frequency difference is small within a range where the horizontal output circuit is not destroyed, the horizontal output circuit is driven at the switched frequency regardless of the frequency difference. Can be about the same time.

According to the fourth aspect of the present invention, a horizontal oscillation circuit having a relatively low oscillation frequency with respect to an instruction voltage is provided.
In other words, in the case of a "low sensitivity" horizontal oscillation circuit, the control means sets "increase the slope" based on the gradient value of the command voltage obtained by the calculation unit, and the horizontal oscillation circuit having a relatively high oscillation frequency with respect to the command voltage, In the case of the "high sensitivity" horizontal oscillation circuit, the control means sets "small inclination" based on the inclination value of the command voltage obtained by the calculation unit. As a result, it is possible to make the time required for the horizontal oscillation circuit having any oscillation characteristics to be driven at the changed frequency substantially the same.

[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 a main part of a display device according to the present invention.

The terminal 1 receives a horizontal synchronizing signal a1 of a video signal input from a video card of a computer (not shown) to a display device. This display device is a multi-scan type in which when the computer switches the screen resolution, the frequency of the horizontal synchronizing signal a1 switches according to the screen resolution.

A horizontal oscillation circuit 3 having a phase comparator 3a and a VCO 3b generates a horizontal drive signal b1 so as to synchronize with the input horizontal synchronizing signal a1, and horizontally scans a CRT (not shown). It is given to the output circuit 5. V
The CO3b is a voltage-controlled oscillator, and has a function of changing the frequency according to an externally supplied F / V value (voltage value). Note that the F / V value corresponds to the command voltage in the present invention.

The horizontal output circuit 5 is a circuit for deflecting the electron beam in the horizontal direction by directly driving the horizontal deflection coil 5b by the horizontal output transistor 5a. The horizontal output transistor 5a is driven by a horizontal drive signal b1 from the horizontal oscillation circuit 3. A variable + B circuit 7 for varying the + B voltage in accordance with a DC voltage obtained by rectifying the collector pulse is connected to the collector via a transformer 5c. Further, a Cs capacitor 5d is connected in series to the horizontal deflection coil 5b. This Cs capacitor 5d is provided to improve the linearity of horizontal deflection. Although not shown, a plurality of the Cs capacitors 5d are formed by connecting a plurality of capacitors in parallel, and the connection between the capacitors is switched to change the capacitance, thereby appropriately improving the frequency according to the frequency of the horizontal synchronization signal a1. Has become possible.

The horizontal synchronizing signal a1 input from the terminal 1
Is also supplied to the measure gate array 9. The measure gate array 9 has a built-in counter and can measure the frequency of the horizontal synchronization signal a1. Also,
The frequency of the horizontal synchronizing signal a1 is constantly monitored, and when the frequency changes, a switching signal d1 is output. Note that the measure gate array 9 corresponds to the detecting means in the present invention.

When the switching signal d1 is input from the measure gate array 9, the microcomputer 11 including the CPU and the memory temporarily increases the frequency of the horizontal drive signal b1 to a predetermined maximum frequency and then changes to the frequency after switching. The DAC 13 is controlled in two stages so as to cause the above. Specifically, first, a provisional F / V value c1 (provisional target value) corresponding to the highest frequency is set in the DAC 13, and the F / V value c1 is changed linearly or stepwise with a predetermined slope toward the F / V value c1. The horizontal drive signal b1 is output to the horizontal output circuit 5, and then a target F / V value c1 (target value) according to the frequency after switching is set in the DAC 13, and a predetermined value is set toward the target F / V value c1. The horizontal drive signal B1 is output to the horizontal output circuit 3 while being changed linearly or stepwise with the inclination (described later).

The microcomputer 11 and the DAC 13
Correspond to the control means in the present invention.

Next, the operation of the display device configured as described above will be described with reference to FIGS. FIG. 2 is a graph showing an example of transition of the F / V value output from the DAC. FIG. 3 is a flowchart showing a process of shifting to the switched frequency, and FIG. 4 is a flowchart showing a step process.

In the following description, a case where the horizontal synchronizing signal a1 input to the terminal 1 is switched in the following order will be described as an example. Also, these frequencies are f ₁ <f
Is a relationship of ₂ <f ₃ <f _4, is intended to set the highest frequency f ₄ to the free-running frequency. f ₁ (for example, 30 kHz) f ₂ (for example, 90 kHz) f ₃ (for example, 100 kHz) f ₄ (for example, 137 kHz) f ₁

<From frequency f ₁ to f ₂ >

[0027] Step S1 the microcomputer 11 receives the switching signal d1 from major gate array 9, in order to oscillate the horizontal oscillation circuit 3 temporarily free-running frequency f _4, temporary F / V corresponding to the free-running frequency f ₄ Find the value c1. Note that the provisional F /
The V value c1 is defined as Fv (Free). The frequency before the horizontal synchronizing signal a1 is switched is referred to as “original frequency”, the F / V value c1 corresponding to this is indicated by Fv (Old), and the frequency when the horizontal synchronizing signal a1 is switched. Is referred to as “frequency after switching”, and a target F / V value c1 corresponding to this is indicated by Fv (New).

Step S2: The obtained Fv (Free) and the F / V corresponding to the original frequency
The value c1 is compared with Fv (Old), and the process branches according to the result. Here If they match, the show that the original frequency and the free-running frequency match, not execute the next step process because once it is not necessary to increase the free-running frequency f _4. Therefore, the following processing is executed only when there is a mismatch at this step.

Referring to the flowchart of the step processing shown in FIG. In this flowchart, for convenience of explanation, F / V corresponding to the original frequency or the free-run frequency is used.
The value is Fv (old), and the F / V value according to the free-run frequency or the frequency after switching is Fv (new).
That is, when changing the F / V value linearly or stepwise, the starting point is Fv (old) and the arriving point is Fv (new).

Step S10 The process branches depending on whether or not the difference between Fv (Free) and Fv (Old) is less than a predetermined change amount ΔData. The change amount ΔData is, for example, 6 count values converted into an F / V value.

Step S11 If the difference between the F / V values of the departure point and the arrival point at step S10 is equal to or greater than the change amount ΔData, that is, if step processing is still required, Fv (Free) and Fv (O
The process further branches according to the magnitude relation of ld).

That is, Fv which is the F / V value of the starting point
Fv (Free) where (Old) is the F / V value of the arrival point
If it is smaller than Fv, it is necessary to increase the F / V value toward the arrival point.
(Old) (step S12).

On the other hand, Fv which is the F / V value of the starting point
Fv (Old) where (Free) is the F / V value of the arrival point
If it is larger than Fv, it is necessary to lower the F / V value toward the arrival point.
It is subtracted from (old) (step S13).

Note that F in steps S12 and S13
v (current) is a temporary variable for temporarily storing the operation value, and gives the operation value to the variable and causes the DAC 13 to output the value to the VCO 3b.

Step S14: The value of the temporary variable Fv (current) is set to Fv (old) and set as a new starting point.

Step S15 Here, the step time ΔTime (for example, 5 ms
After waiting only for c), the slope of the linear or stepwise change of the F / V value is set. As described above, since the increase / decrease of the F / V value is ΔData and the step time is ΔTime, the absolute value of the gradient is ΔData / ΔTime. It is preferable that the inclination is set so as to be within a value that the horizontal output transistor 5a can endure and to be as large as possible.

As a result of repeating steps S10 to S15, Fv (Free) is determined in step S10.
If the difference between Fv (Old) and Fv (Old) is less than the change amount ΔData, the process branches to step S16. And F
v (current) is set to Fv (new) (= Fv (Free)), and the DAC 13 outputs the value to the VCO 3 b. Accordingly, at the time of executing this step S16, the frequency of the horizontal drive signal b1, once, the highest frequency f _4.

The above processing corresponds to the processing in the first half of the time Ta in FIG.

Step S4 The microcomputer 11 determines whether or not the frequency is stable, and branches the processing according to the result of the determination. That is, it is determined whether or not the horizontal synchronization signal a1 has changed. If the horizontal synchronization signal a1 is stable, the following processing is executed. If the horizontal synchronization signal a1 is unstable, step S4 is repeatedly executed until the horizontal synchronization signal a1 becomes stable.

Step S5: F corresponding to the frequency f ₂ after switching of the horizontal synchronizing signal a1
/ V value c1, that is, Fv (N
ew). In the present example, Fv (New) becomes Fv (f ₂ ).

Step S6 If the target F / V value (= Fv (New)) does not match the provisional F / V value, the above-described step processing (FIG. 4)
Is executed, and if they match, the process ends.

Steps S10 to S16 As already described in detail, the free-run frequency f _{4 is set} to Fv
(Formerly), and the frequency f ₂ after the switching and Fv (new), Fv predetermined inclination F / V value toward the (new) (? Da
ta / ΔTime).

The above processing corresponds to the processing in the latter half of the time Ta in FIG.

The processing time Tb in the FIG. 2 is executed by the processing described above <to f ₃ from the frequency f _2>. That is, the F / V value corresponding to the original frequency f ₂ = Fv (f ₂ )
Once corresponds to the highest frequency f ₄ from the temporary F / V value = Fv
After being raised to (f ₄ ), the target F / V value corresponding to the switched frequency f ₃ is reduced to Fv (f ₃ ). Note that the slope at the time of increase / decrease at this time is the same as that at the time of the above processing.

<From frequency f ₃ to f ₄ > The processing at time Tc in FIG. 2 is executed. That is, the original frequency f ₃
Is temporarily increased from the F / V value of Fv = Fv (f ₃ ) to the provisional F / V value of the highest frequency f ₄ = Fv (f ₄ ), and then step S6
Are determined to match, and the process ends without executing the step processing in step S7. In this case, the temporary F / V value (temporary target value) is changed to the target F / V value (target value).
Is equivalent to

[0046] <to f ₁ from the frequency f _4> processing time Td in the FIG. 2 is executed. That is, it is determined in step S2 that they match, and the F / V value of the original frequency f ₄ = F
After being immediately lowered from v (f ₄ ) to the target F / V value = Fv (f ₁ ), it is determined that they match in step S6, and the step processing in step S7 ends without being executed.

As described above, when the frequency of the horizontal synchronizing signal a1 changes, the target F according to the frequency after switching is changed.
The F / V value applied to the horizontal oscillation circuit 3 toward the / V value is changed linearly or stepwise with a slope ΔData / ΔTime set within a fluctuation value of the frequency that the horizontal output circuit 5 can endure. Therefore, the time required to reach the frequency after the switching can be significantly reduced as compared with the exponential function change by the conventional RC, and the time required for the screen to be stabilized when the resolution is switched can be reduced. be able to.

Further, since the RC to the target F / V value is not required for the inclination to the target F / V value, the inclination is hardly affected by the variation of parts and the change with time. Therefore, the destruction of the horizontal output circuit 5 can be reliably prevented while designing relatively easily.

The above-mentioned gradient ΔData / ΔTim
e may be set as follows.

That is, in the adjustment stage of the factory, first, an F for causing the horizontal oscillation circuit 3 to oscillate at two or more predetermined frequencies (corresponding to the first frequency and the second frequency, for example, 130 kHz and 30 kHz). / V value is measured. While measuring the frequency of the horizontal drive signal b1 by the measure gate array 9 or the microcomputer 11, the F / V value c1
Is changed, and the respective F / V values (the first command voltage and the second command voltage) when the frequency reaches a predetermined frequency set in advance are measured. The microcomputer 11 obtains a step time ΔTime of the slope based on the measured value at that time and a preset reference F / V value (first reference instruction voltage and second reference instruction voltage).

The above ΔTime is, for example, the following (1)
It is obtained by the formula.

[0052]

(Equation 1)

By setting ΔTime in accordance with the oscillation characteristics of the horizontal oscillation circuit 3 in this manner, the gradient of the change in the F / V value is varied, and as a result, the time required for driving at the switched frequency is substantially reduced. It can be the same between devices.

Of course, the inclination of the change in the F / V value may be varied by setting not only ΔTime but also ΔData or both. Further, the measure gate array 9 and the microcomputer 11 correspond to an indicated voltage measuring means of the present invention, and the microcomputer 11 corresponds to an arithmetic unit of the present invention.

In the above embodiment, the horizontal drive signal b1
So that changing the frequency of the horizontal synchronizing signal a1 after switching the frequency of once after changing to the highest frequency f ₄ of the. This is to prevent the horizontal output circuit 5 from being destroyed due to the shortage of the capacitance of the CS capacitor 5d of the horizontal output circuit 5 in the frequency switching process. That is, the CS capacitor 5d is generally large when the frequency of the horizontal drive signal b1 is low, and can secure the horizontal linearity even when it is small when the frequency of the horizontal drive signal b1 is high, but when the capacitance is insufficient. Again, the horizontal output transistor 5a may be destroyed. Therefore, once the frequency of the horizontal drive signal b1 is increased, shortage of capacity can be prevented when the CS capacitor 5d is switched, and destruction of the horizontal output circuit 5 due to shortage of capacity of the CS capacitor 5d can be prevented. Can be.

The present invention is not limited to the above embodiment, but can be modified as follows.

(1) In the case where the destruction caused by the CS capacitor 5d does not occur, the frequency of the horizontal drive signal is immediately changed to the frequency after switching without temporarily increasing to the highest frequency. You may do so.

(2) Instead of temporarily raising the frequency of the horizontal drive signal to the highest frequency, the horizontal drive signal may be changed to a frequency intermediate between the highest frequency and the lowest frequency. This makes it possible to reduce the average transition time regardless of which frequency is switched to the frequency after switching.

(3) In the above embodiment, the inclination is the same in each case, but within the fluctuation value that can prevent the destruction,
The slope may be changed according to the “difference” between the original frequency and the frequency after switching. For example, when the difference is large, the slope may be increased, and when the difference is small, the transition time may be shortened.

(4) In the circuit configuration of the above-described embodiment, the measure gate array 9 is used as the detecting means.
The microcomputer 11 may have the function.

[0061]

As is apparent from the above description, according to the first aspect of the present invention, when the frequency of the horizontal synchronizing signal changes, the horizontal oscillation is performed toward the target value corresponding to the frequency after switching. Since the command voltage applied to the circuit is changed linearly or stepwise with a slope set within the fluctuation value of the frequency that the horizontal output circuit can withstand, it takes longer to reach the frequency after switching than when changing exponentially. Can be shortened, and the time until the screen is stabilized can be shortened.

Further, since the inclination to the target value can be set without using RC, there is almost no influence from the variation of these components and the change with time. Therefore, the destruction of the horizontal output circuit can be reliably prevented while designing relatively easily.

According to the second aspect of the present invention, the frequency of the horizontal drive signal is once changed to the highest frequency and then changed to the frequency of the switched horizontal synchronizing signal. Shortage in the frequency switching process can be prevented. Therefore, it is possible to prevent the horizontal output circuit from being broken due to the shortage of the capacitance of the CS capacitor.

According to the third aspect of the present invention, when the difference between the original frequency and the frequency after switching is large,
By setting the slope of the change in the indicated voltage to be larger than when the difference in frequency is small within a range where the horizontal output circuit is not destroyed, it is possible to reduce the time required for driving at the switched frequency regardless of the difference in frequency. You can do the same. Therefore, regardless of the difference between the original frequency and the frequency after the switching, the time until the screen is stabilized can be made substantially constant.

According to the fourth aspect of the present invention, the inclination of the command voltage is set according to the oscillation sensitivity of the horizontal oscillation circuit. Therefore, the frequency after switching can be set even in a horizontal oscillation circuit having any oscillation characteristics. Can be made substantially the same, and variations between devices can be suppressed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a main part of a display device according to the present invention.

FIG. 2 is a graph showing an example of transition of an F / V value output from a DAC.

FIG. 3 is a flowchart illustrating a process of shifting to a switched frequency.

FIG. 4 is a flowchart showing step processing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Terminal 3 ... Horizontal oscillation circuit 3a ... Phase comparator 3b ... VCO5 ... Horizontal output circuit 5a ... Horizontal output transistor 5b ... Horizontal deflection coil 5c ... Transformer 5d ... Cs capacitor 7 ... Variable + B circuit 9 ... Major gate array 11 ... Microcomputer 13 ... DAC a1 ... horizontal synchronization signal b1 ... horizontal drive signal c1 ... F / V value d1 ... switching signal

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] March 30, 2000 (2003.3.3)
0)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0005

[Correction method] Change

[Correction contents]

[0005]

However, the prior art having such a structure has the following problems. That is, by delaying the instruction voltage to the horizontal oscillation circuit, the frequency change of the horizontal drive signal can be changed.
Since B circuit can sufficiently follow, while it is possible to prevent destruction of the horizontal output transistor, the instruction voltage from the fact that delayed by the time constant circuit is on rise exponentially. Therefore the variable + B circuit will be bought delay time than necessary considering the following is one of the screen when switching the resolution of the screen there is a problem that prolonged the time to stabilize.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0022

[Correction method] Change

[Correction contents]

When the switching signal d1 is input from the measure gate array 9, the microcomputer 11 including the CPU and the memory temporarily increases the frequency of the horizontal drive signal b1 to a predetermined maximum frequency and then changes to the frequency after switching. The DAC 13 is controlled in two stages so as to cause the above. Specifically, first, a provisional F / V value c1 (provisional target value) corresponding to the highest frequency is set in the DAC 13, and the F / V value c1 is changed linearly or stepwise with a predetermined slope toward the F / V value c1. The horizontal drive signal b1 is output to the horizontal output circuit 5, and then a target F / V value c1 (target value) according to the frequency after switching is set in the DAC 13, and a predetermined value is set toward the target F / V value c1. The horizontal drive signal b1 is output to the horizontal output circuit 3 while being changed linearly or stepwise with the inclination (described later).

Claims (4)

[Claims] 1. A C which is horizontally scanned by a horizontal output circuit
In a multi-scan type display device equipped with an RT, detecting means for detecting that the frequency of the horizontal synchronizing signal has been switched and outputting a switching signal, and responding to an instruction voltage corresponding to the frequency of the input horizontal synchronizing signal A horizontal oscillation circuit that outputs a horizontal drive signal synchronized with the horizontal synchronization signal whose frequency has been switched to the horizontal output circuit; and a horizontal synchronization circuit when a switching signal is output from the detection unit. Control means for changing the command voltage linearly or stepwise with a predetermined slope toward a target value corresponding to the frequency after switching of the signal. 2. The display device according to claim 1, wherein the control unit changes the command voltage to a tentative target value corresponding to a highest frequency, and then changes the command voltage according to the frequency after the switching of the horizontal synchronization signal. A display device that changes the command voltage linearly or stepwise with a predetermined slope toward a target value. 3. The display device according to claim 1, wherein the control unit sets a slope of the command voltage according to a difference between an original frequency of the horizontal synchronization signal and a frequency after the switching. Display device. 4. The display device according to claim 1, wherein a first instruction voltage for causing the horizontal oscillation circuit to oscillate at a first frequency, and the horizontal oscillation circuit is oscillated at a second frequency. Command voltage measuring means for measuring a second command voltage, a difference between the first command voltage and the second command voltage, and a first reference command voltage which is set in advance and is a reference. 2
A display unit for calculating a slope value of the command voltage based on a ratio of the reference command voltage to the difference between the reference command voltages, and wherein the control unit sets the slope based on the slope value.