JPH0361996A - Pseudo synchronizing signal generating device - Google Patents

Abstract

PURPOSE:To adjust a screen display position by generating a saw-tooth wave which leads by a constant phase and has a constant tilt angle, comparing its amplitude with a threshold value which can be set optionally from outside and generating a pseudo synchronizing signal which has a phase difference from a synchronizing signal corresponding to the threshold value. CONSTITUTION:This device is equipped with saw-tooth wave generating means 12 - 14 which generate the saw-tooth wave which has the constant tilt angle to obtain the pseudo synchronizing signal determining the screen display position and has a synchronizing signal period while the wave is advanced by the constant phase and voltage amplitude comparing means 20 and 21 which compare the output saw-tooth wave with the externally settable threshold value and generates the pseudo synchronizing signal having the phase difference from the synchronizing signal corresponding to the threshold value. Consequently, the screen display position can be adjusted with desired resolution irrelevantly to a deflection frequency.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a pseudo synchronization signal generator suitable for adjusting the screen display position of a display device that receives various synchronization signals, such as a multi-scan display device. .

[Prior Art] Most CRT display devices used as external output devices for information processing devices such as personal computers have an effective display area set with a non-display area left inside the screen frame of the device itself. A commonly used method is to specify the start end of an effective display area using a pseudo synchronization signal generated by delaying a horizontal synchronization signal.

The pseudo synchronization signal generating device l shown in FIG. 4 is applied to a multi-scan display device 2 that supports a plurality of horizontal deflection frequencies. Between the interface circuit 4, which is a reception window for the synchronization signal, and the variable duty ratio circuit 6, which supplies a synchronization pulse having a predetermined duty ratio according to the horizontal deflection frequency to the horizontal oscillation circuit in the horizontal deflection circuit 5, Consisting of a first signal delay device 7 that determines the leading edge of the pseudo synchronization signal, that is, the screen display position, and a second signal delay device 8 that determines the trailing edge of the pseudo synchronization signal, that is, the synchronization pulse width, connected in series. It is.

In this example, the first signal delay device 7 is composed of a monostable multivibrator 7a having a time constant τ1 determined by an external variable resistor R1 and a capacitor C1, and the second signal delay device 8 is also composed of a monostable multivibrator 7a. , a monostable multivibrator 8a having a time constant τ2 determined by an external variable resistor R2 and a capacitor C2. Here, as shown in FIG. 5, the first signal delay device 7 is connected to the interface circuit 4.
The second signal delayer 8 is triggered at the trailing edge of the output delay pulse of the first signal delayer 8 and delays the signal according to the time constant τl. τ
A pseudo synchronization signal is generated by a signal delay corresponding to 2. Therefore, by adjusting the resistance value of the variable resistor R1 attached to the first signal delay device 7, the effective The display area can be adjusted horizontally. Note that by controlling the duty ratio within the variable duty ratio circuit 6, the horizontal deflection circuit system is always maintained in an optimal driving state even for different horizontal deflection frequencies.

[Problems to be Solved by the Invention] The above-mentioned conventional pseudo synchronization signal generating device 1 is configured by adding or replacing a function expansion board or the like on the personal computer 3 side which is the video output source, and changing the horizontal deflection frequency to the standard frequency of 15.
When switching from kHz to, for example, 100 kHz for high resolution, the delay time width τl in the first signal delay device 3 that occupies one horizontal scanning period increases relatively, and as a result, the effective display area is shifted to the left side of the screen. In this case, it is necessary to return the effective display area to the center of the screen in response to changes in the horizontal deflection frequency on the video signal sending side. A method is adopted in which the delay time τl is adjusted by varying the resistance value of the variable resistor R1.

However, the range in which the delay time τl can be varied by the variable resistor R1 is extremely limited. That is, the variable range of the horizontal deflection frequency is, for example, 15 kHz to
Assuming 100 kHz, the maximum delay time is 60
ILs, and when scanning a display with a horizontal width of 500 mm at a horizontal deflection frequency of 100 kHz, the screen display position is set to 1. If you try to move it in mm units, the resolution required to adjust the delay time τ1 is 20n.
It is s.

Therefore, a signal delay of up to 60 μs in 20 ns increments is required for the monostable multivibrator 7a whose variable means is the single variable resistor R1. However, even if a high-precision timer IC is used, in reality, there is no timer IC that can meet these demands, and as a result, there is a natural limit to the deflection frequency that can be accommodated, and the resistance is variable. Since there is a non-linear relationship between operations and operation results, there have been problems such as difficulty in making adjustments.

In addition, the resistor R1 and capacitor C1 externally attached to the monostable multivibrator 7a in the first signal delay device 7 are configured with a parallel connection circuit of a plurality of resistors and capacitors with relay contacts. It is also possible to change the time constant by switching the relay, but in that case, the number of deflection frequencies that can be supported is limited to the number determined by the combination of resistors and capacitors, and it is necessary to support a wider range of deflection frequencies. The more circuit elements are used, the higher the manufacturing cost becomes.Also, even if multiple relay switching type signal delay devices are connected in series to increase the delay accuracy of each one,
There are problems such as not only the cost but also the extremely troublesome management of the delay time shared by each signal delay device.

[Means for Solving the Problems] The present invention solves the above problems, and includes a pseudo synchronization signal generation device that advances or delays a synchronization signal and generates a pseudo synchronization signal that determines a screen display position. A sawtooth wave generating means generates a sawtooth wave having a synchronization signal period having a constant inclination angle by advancing the synchronization signal by a certain phase, and an output sawtooth wave of the sawtooth wave generation means is connected to an external The present invention is characterized by comprising a voltage amplitude comparing means for comparing the voltage amplitude with a threshold value that can be arbitrarily set from , and generating a pseudo synchronization signal having a phase difference corresponding to the threshold value with respect to the synchronization signal.

[Function] The present invention provides a synchronization signal that is subject to phase advancement or delay in order to obtain a pseudo synchronization signal that determines the screen display position.
Generates a sawtooth wave with a constant inclination angle that is advanced by a certain phase, compares the voltage amplitude of this sawtooth wave with a threshold value that can be set arbitrarily from the outside, and sets a phase difference according to the threshold value to the synchronization signal. By generating a pseudo synchronization signal having the following characteristics, it is possible to adjust the screen display position with a desired resolution regardless of the deflection frequency.

[Embodiments] Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 3. FIG. 1 is a circuit configuration diagram showing one embodiment of the pseudo synchronization signal generating device of the present invention, and FIGS. 2 and 3 are signal waveform diagrams of various parts of the circuit shown in FIG. 1 at different deflection frequencies.

The pseudo synchronization signal generator 11 shown in FIG. 1 is configured to advance or delay the synchronization signal by comparing the voltage amplitude of a sawtooth wave having the same period as the advance synchronization signal with an arbitrarily set threshold value. A pseudo synchronization signal is obtained by pulse width modulation using a phase-advanced sawtooth wave as a carrier.

The sawtooth wave necessary for pulse width modulation is generated by sawtooth wave generation means including an intermediate purpose sawtooth wave generation circuit 12, a synchronous phase advance circuit 13, a final purpose sawtooth wave generation circuit 14, and the like. Both the intermediate purpose sawtooth wave generation circuit 12 and the final purpose sawtooth wave generation circuit 14 include a constant current circuit 16 configured by connecting a differential amplifier 15 with a gain of l between the base and emitter of a charging transistor Qc, and an integrating capacitor. A discharging transistor Q is connected to the charging path of C and conducts to the discharging path of the integrating capacitor C by an input synchronizing signal or a phase-advance synchronizing signal.
It is constructed by connecting d. The collector voltage of the charging transistor is maintained at the same voltage as the non-inverting input voltage Vc by the action of the differential amplifier 15. Therefore, a constant voltage is always applied across the collector resistor Rc of the charging transistor Qc, and the current I flowing through the charging transistor Qc is made constant. That is, the sawtooth wave obtained here rises linearly with an inclination angle I/C, and its beeb value Vp takes a value TI/C obtained by multiplying the inclination angle I/C by the synchronization period T.

The synchronous phase advance circuit 13 is a peak hold circuit 17 that holds the voltage amplitude peak value of the intermediate sawtooth wave.
and a subtracter 1 that subtracts a - constant value Δ■ corresponding to the phase ΔT to be advanced from the output Vp of the peak hold circuit 17.
8 and a comparator 19 that compares the voltage amplitude of the intermediate sawtooth wave using the output Vp-ΔV of the subtracter 18 as a threshold. Therefore, the sawtooth wave of the synchronization signal period generated by the intermediate purpose sawtooth wave generation circuit 12 outputs a high level output as a phase-advanced synchronization signal during a period in which the amplitude exceeds VpΔ■. That is, Fig. 2 (C) or Fig. 3 (C
), the phase-advanced synchronized signal is ahead of the synchronized signal by exactly T time, and this synchronized phase-advanced processing eliminates the preprocessing necessary to change the phase of the synchronized signal back and forth. will be completed.

On the other hand, the end-use sawtooth wave generation circuit 14 is triggered by the phase advance synchronization signal, generates a sawtooth wave having a predetermined rising slope angle, and supplies this to the non-inverting input terminal of the comparator 20 in the next stage. do. The inverting input terminal of the comparator 20 is supplied with a DC voltage as a threshold value Vr from the personal computer 3 via a DA converter 21 that converts digital data into an analog signal. . In this case, the threshold value Vr set in the comparator 20 is digitally set as a value that is an integral multiple of the unit delay time τ using the keyboard device attached to the personal computer 3 or the up/down switch on the front of the display device. As shown in FIG. 2(E) or FIG. 3(E), a pseudo synchronization signal having a delay time φ proportional to the threshold value Vr is obtained.

Note that when the inclination angle (slew rate) of the sawtooth wave used is O, IV/μS, the peak value of the sawtooth wave at 15 kHz is about 6.6V. Also, for a deflection frequency of 100 kHz, that is, a synchronization period of 10 μs, the IV
Assuming that a sawtooth wave with a peak value of is generated, the signal delay of unit delay time τ (=20ns) is IV
A minimum of 20 ns/10 1 Ls or 2 mV is required. Therefore, the final sawtooth wave generation circuit 14 has a phase accuracy of 20 ns and an amplitude accuracy of 2 mV.
/6.6v, and as the comparator 20, it is necessary to use a comparator IC with an operation phase delay of 20 ns or less and a resolution (in this case, a manual offset voltage) of 2 mV or less.

In this way, the pseudo synchronization signal generator 11 does not aim at synchronization delay by pulse width modulating the sawtooth wave (intermediate purpose sawtooth wave) having the same phase as the synchronization signal, but by delaying the synchronization by a predetermined phase relative to the synchronization signal. Since the phase-advanced sawtooth wave (end-use sawtooth wave) is pulse width modulated with an externally set threshold value Vr, the synchronization signal can be accurately advanced or delayed within a certain period before and after it. , and the input offset voltage of the comparator used for voltage amplitude comparison is determined by the slope angle of the sawtooth wave (
Minimum delay time τ
Signal delay is possible. Therefore, by using sawtooth wave generation means with a high slew rate, a desired pseudo-synchronization signal can be obtained without using complicated methods such as connecting multiple signal delay devices in series, and it is possible to obtain a desired pseudo-synchronization signal over a wide range of deflection frequencies. This is particularly suitable for multi-scan display devices that require support.

It also generates an intermediate sawtooth wave that is in phase with the synchronization signal,
By comparing the voltage amplitude of this with a threshold value Vp-Δ■ set at a level lower than the peak value Vp by a certain value, an advanced synchronization signal that is advanced by a predetermined phase ΔT with respect to the synchronization signal is obtained. Since the configuration is configured to generate a final use sawtooth wave having the same phase as the phase advance synchronization signal, two types of sawtooth wave generation circuits 12 and 14 for intermediate use and final use are connected via the synchronization phase advance circuit 13. By cascading, the desired sawtooth wave can be generated, and the intermediate sawtooth wave is pulse width modulated by amplitude comparison with a fixed level, so that the synchronization signal is always accurate regardless of the deflection frequency. The phase can be advanced by a predetermined period of time, and the accuracy of pulse width modulation using the end-use sawtooth wave as a carrier can be improved from the side.

In addition, both the intermediate purpose sawtooth wave generation circuit 12 and the final purpose sawtooth wave generation circuit 14 are charged with a constant current 1 supplied from the constant current circuit 16, and are discharged during the synchronization signal period or the advanced synchronization signal period. Since the structure is configured to generate a sawtooth wave voltage with an inclination angle determined by the charging current value ■ and the capacitor capacity C, a highly accurate sawtooth wave can be obtained as the terminal voltage of the capacitor C charged with a constant current. be able to.

Also, a DA converter 21 that converts digital data given from the outside into an analog signal, and this DA converter 21
Since the voltage amplitude comparison means is configured with a comparison 9920 that compares the voltage amplitude of the output of the sawtooth wave generation means with the output Vr of the output Vr as a threshold value, it is possible to accurately and easily set the phase difference of the pseudo synchronization signal with respect to the synchronization signal. As a result, the screen display position can be automatically adjusted to the center of the display regardless of the horizontal deflection frequency, or the screen display position can be adjusted in steps with minimum increments based on commands from the personal computer 3 connected to the multi-scan display device. can be moved.

In the above embodiment, the pseudo synchronization signal generator 11 is
Although the case where the present invention is applied to a multi-scan display device that supports multiple horizontal deflection frequencies is taken as an example, it can also be applied to a multi-scan display device that supports multiple vertical deflection frequencies, and in that case, By advancing or delaying the vertical synchronization signal, the screen display position can be moved up and down using the obtained pseudo vertical synchronization signal.

E. Effects of the Invention As explained above, the present invention provides a fixed tilt angle that is advanced by a certain phase with respect to a synchronization signal that is subject to phase advance or delay in order to obtain a pseudo synchronization signal that determines the screen display position. A configuration in which a sawtooth wave is generated, the amplitude of this sawtooth wave is compared with a threshold value that can be arbitrarily set from the outside, and a pseudo synchronization signal having a phase difference according to the threshold value with respect to the synchronization signal is generated. Therefore, instead of achieving synchronization delay by pulse width modulating a sawtooth wave that has the same phase as the synchronization signal, we use a phase-advanced sawtooth wave that is advanced by a predetermined phase than the synchronization signal to an externally set threshold. Since the pulse width is modulated by the pulse width modulation, the synchronizing signal can be accurately advanced or delayed within a certain period before and after the synchronization signal, and the input offset voltage of the comparator used for amplitude comparison can be adjusted by changing the slope angle (slew rate) of the sawtooth wave. It is possible to delay the signal so that the time obtained by dividing by is the minimum delay time,
Therefore, by using a sawtooth wave generating means with a high slew rate, a desired pseudo-synchronous signal can be obtained without using complicated methods such as connecting multiple signal delay devices in series.
It has excellent effects, such as being suitable for multi-scan display devices that require support for a wide range of deflection frequencies.

Further, the present invention generates an intermediate purpose sawtooth wave having the same phase as the synchronization signal as a sawtooth wave generating means, and compares this with a threshold sensitive voltage amplitude set at a level lower than its peak value by a certain value. By doing so, by obtaining a phase-advanced synchronization signal that is a predetermined phase ahead of the synchronization signal, and then generating an end-use sawtooth wave having the same phase as this phase-advance synchronization signal,
A desired sawtooth wave can be generated by connecting two types of sawtooth wave generation circuits, one for intermediate use and one for final use, in series via a synchronous phase advancing circuit. Since the pulse width is modulated by comparing the amplitude with a fixed level,
The synchronizing signal can always be phase-advanced by a predetermined amount of time, and the accuracy of pulse width modulation using the end-use sawtooth wave as a carrier can be improved from the side.

In addition, both the intermediate use sawtooth wave generation circuit and the final use sawtooth wave generation circuit are provided with a capacitor that is charged by a constant current supplied from a constant current circuit and discharged during the synchronization signal period or the advanced synchronization signal period. It can be configured to generate a sawtooth wave voltage with an inclination angle determined by the value and capacitance of the capacitor, and has effects such as being able to obtain a highly accurate sawtooth wave as the terminal voltage of a capacitor charged with a constant current. play.

Further, the amplitude comparing means includes a DA converter that converts digital data given from the outside into an analog signal, and a comparator that uses the output of the DA converter as a threshold and compares the voltage amplitude of the output of the sawtooth wave generating means. By doing this, the phase difference between the pseudo synchronization signal and the synchronization signal can be set accurately and easily.This allows the screen display position to be adjusted regardless of the deflection frequency using commands from a personal computer connected to a multi-scan display device. This provides effects such as automatically adjusting the display to the center or moving the screen display position in steps with minimum increments.

[Brief explanation of drawings]

Fig. i is a circuit configuration diagram showing one embodiment of the pseudo synchronous signal generator of the present invention, Figs. 2 and 3 are signal waveform diagrams of various parts of the circuit shown in Fig. 1 at different deflection frequencies, respectively.
FIG. 4 is a circuit configuration diagram showing the main parts of an example of a multi-scan display device to which a conventional pseudo synchronization signal generator is applied, and FIG. 5 is a signal waveform diagram of each part of the circuit shown in FIG. 4. . 319. Personal computer, 11. ,. Pseudo synchronous signal generator, 12, 13, 14. ,. Sawtooth wave generating means, 12. , , Intermediate purpose sawtooth wave generation circuit, 13. ,,synchronous phase advance circuit,14. ,. Final use sawtooth wave generation circuit, 1B, Constant current circuit, 1
7. ,, Peak hold circuit, 18. . , subtractor, 19, 20. ,,Comparator,21. ,. DA converter. 20°21. Voltage amplitude comparison means C. capacitor.

Claims (5)

[Claims] (1) In a pseudo synchronization signal generation device that advances or delays a synchronization signal and generates a pseudo synchronization signal that determines the screen display position, a sawtooth wave with a synchronization signal period having a constant inclination angle,
The sawtooth wave generation means generates a sawtooth wave by advancing the synchronization signal by a certain phase, and the output sawtooth wave of the sawtooth wave generation means is compared with a threshold value that can be arbitrarily set from the outside, and the voltage amplitude is compared with a threshold value that can be arbitrarily set from the outside. A pseudo synchronization signal generation device comprising voltage amplitude comparison means for generating a pseudo synchronization signal having a phase difference according to the threshold value with respect to the synchronization signal. (2) The sawtooth wave generating means includes an intermediate sawtooth wave generation circuit that is triggered by the synchronization signal and generates an intermediate sawtooth wave having the same phase as the synchronization signal and a constant slope angle; a synchronous phase advance circuit that compares the voltage amplitude of the output of the wave generation circuit with a threshold value set at a level lower than its peak value by a certain value, and outputs a phase advance synchronization signal that is advanced by a predetermined phase with respect to the synchronization signal; and an end-use sawtooth wave generating circuit that is triggered by the output of the synchronous phase advancing circuit and generates an end-use sawtooth wave having a constant slope angle. . (3) The intermediate purpose sawtooth wave generating circuit has a capacitor that is charged by a constant current supplied from a constant current circuit and discharged during a synchronization signal period, and has a slope angle determined by the charging current value and capacitor capacity. 3. The pseudo synchronization signal generating device according to claim 2, wherein the pseudo synchronization signal generating device is configured to generate a sawtooth wave voltage. (4) The end-use sawtooth wave generating circuit has a capacitor that is charged by a constant current supplied from a constant current circuit and discharged during the phase advance synchronization signal period, and has a slope determined by the charging current value and capacitor capacity. 3. The pseudo synchronous signal generating device according to claim 2, wherein the pseudo synchronous signal generating device is configured to generate a sawtooth wave voltage having an angle. (5) The voltage amplitude comparison means compares the voltage amplitude of the output of the sawtooth wave generation means with a DA converter that converts externally applied digital data into an analog signal, using the output of this DA converter as a threshold value. 2. The pseudo synchronization signal generating device according to claim 1, further comprising a comparator.