JPH0242480A - Horizontal frequency switching circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a horizontal frequency switching circuit suitable for application to a signal supply device such as a personal computer that can vary horizontal resolution.

"(Niku's technology)" Usually a personal computer (hereinafter referred to as a personal computer)
Natote supplies the signal-processed data to the CRT and
It is displayed on the T screen.

In recent years, a computer has been proposed in which the resolution of the image is improved by varying the horizontal frequency when the image signal is subjected to 1G processing in a personal computer.

When a high-resolution image signal is supplied from the computer to the CRT, in order to maintain that resolution, the horizontal frequency of the CRT must be changed to the horizontal frequency of the supplied image No. 18 (the horizontal frequency of frequency).

To do this, it is necessary to detect differences in horizontal frequencies of signals supplied from the personal computer.

Conventionally, the determination is made by counting the number of pulses of the horizontal gate signal during one vertical interval of the image signal supplied to the CRT ill. Or, use a multi-vibrator to open horizontally! The II signal is subjected to frequency/voltage conversion for discrimination.

``Problem to be Solved by the Invention'' By the way, as mentioned above, when the horizontal frequency on the CRT side is switched by counting the number of pulses of the horizontal synchronizing signal, there is a problem in that it takes time for the frequency switching signal to be output. be.

In addition, when discrimination is performed using a multivibrator, it is converted to analog once, so the frequency is cut off. ! ! In order to obtain the signal, an integrator, a comparator, etc. are required, and the problem is that the circuit becomes complicated.

Therefore, the present invention solves these conventional problems with a simple structure, and by adding information for determining the horizontal frequency to the signal generated on the signal supply device side, the horizontal frequency on the CRT side is The present invention proposes a horizontal frequency switching circuit that can easily and reliably detect frequencies.

"Means for Solving the Problems" In order to solve the above-mentioned problems, in the present invention, in a signal supply device that can vary the horizontal frequency, the pulse width of the horizontal or vertical synchronizing signal is determined based on the selection mode of the horizontal frequency. The present invention is characterized by comprising: a variable pulse width circuit; and switching means for switching the pulse width of the variable pulse width circuit according to a horizontal frequency selection mode.

"Function" In the horizontal frequency switching circuit having such a configuration, as shown in FIG. 14 can be switched.

Next, depending on the selected horizontal resolution, the variable pulse width circuit 12 controls the horizontal or vertical I! The pulse width of the 11 signal is varied.

As a result, the horizontal or vertical synchronizing signal output from the signal supply device 10 includes information for determining its horizontal frequency.

Therefore, on the display means (CRT) 20 side, the horizontal frequency can be easily detected in real time from the supplied signal by using a simple circuit (configuration).

"Embodiment" Next, an example of the horizontal frequency switching circuit according to the present invention will be explained in detail with reference to FIG. 1 and subsequent figures.

Fig. 1 is a diagram showing a personal computer having a 1-system horizontal frequency switching circuit according to the present invention and a CRT having a detection means for detecting the horizontal frequency from signals supplied from the personal computer, and Fig. 2 is a timing chart of each signal. be.

As shown in FIG. 1, a personal computer 10 includes a CRT controller 11 that generates a horizontal synchronizing signal a (FIG. 2 A) as a horizontal frequency switching circuit 1, a horizontal frequency switching circuit 1, and a CRT controller 11 that generates a horizontal synchronizing signal a (FIG. 2 A). , a first monostable multivibrator 12 which is a pulse width variable circuit variable by C2, a mode selection circuit 13 that operates when a horizontal resolution is selected and outputs a mote selection signal m according to the selected mode, A switching means 14 is provided which can be switched depending on the selection number m.

On the other hand, the CRT 20 has a preset pulse width Z.
a second monostable multivibrator 21 that outputs a signal e (D in FIG. 2), and a second monostable multivibrator 2
A pulse signal generating means 22 that generates a pulse signal P (E in the same figure) that rises at the falling timing of the signal e output from I, and a horizontal A detection means 2 constituted by a D-type flip-flop 23 for outputting a frequency switching signal and a third monostable multivibrator 24 for reproducing the same gate signal are provided.

A horizontal frequency switching circuit with such a configuration! First, on the PC lo side, use the operation key (not shown) to set the horizontal resolution.
selected by A mote selection signal m is output from the mote selection circuit 13 in accordance with this selection mode.

The switching means 4 is switched to the A or B side in response to this mode selection signal fn. As a result, the pulse width of the first monostable multivibrator 12 is determined by the resistor R and the capacitor C1 or C2.

The horizontal open signal 1Ijl+=a generated from the CRT controller 11 as shown in FIG. 2A is changed by the first monostable multivibrator I2 to a pulse width corresponding to the selected mote.

For example, in order to obtain normal horizontal resolution, the switching means 14 may be
When it is switched to the side, the synchronization signal is changed to a pulse [X determined by the resistor R and the capacitor C1 as shown in FIG. 2B.

Further, when changing to a higher horizontal resolution than usual, the switching means 14 is switched to the B side. At this time, as shown in FIG. 2C, a synchronizing signal with a pulse width Y (Y>X) set by the resistor R and the capacitor C2 is output.

The synchronizing signal t whose pulse width has been changed in this way is supplied from the personal computer 10 to the CRT 20.

The second monostable multivibrator 21 rises in synchronization with the supplied synchronizing signal t, and generates a pulse IgZ signal e, which is set in advance by the resistor R2 and the capacitor C3.
is output (see second diagram).

This pulse width Z is determined by the first monostable multivibrator 12
The pulse width is set to be intermediate between the pulse width X and the pulse width Y of the synchronization signal t output from the synchronization signal t.

1 output from the second monostable multivibrator 21
The word e is supplied to pulse signal generating means 22. The pulse signal generating means 22 generates the pulse signal P as described above, and outputs it to the clock terminal of the D flip-flop 23.

As a result, in order to obtain normal horizontal resolution, if the synchronizing signal t as shown in FIG. It becomes a low level signal (see Figure 2 F).

On the other hand, in order to obtain high horizontal resolution, when the same gate signal t as shown in FIG. 2C is fed to the D flip-flop, its output Q becomes high level (see FIG. 2G).

Therefore, different frequency switching signals can be obtained depending on the pulse width of the synchronization signal t supplied from the personal computer 10.

When the horizontal frequency oscillator (not shown) of the CRT 20 is driven based on the frequency switching signal thus generated, the image is scanned at a horizontal frequency that matches the horizontal frequency of the image signal supplied from the personal computer 10. The image is displayed on the CRT 20.

Note that the synchronizing signal t thus supplied from the personal computer 10 has a changed pulse width, so it cannot be used as a synchronizing signal as is.

Therefore, in the third monostable multivibrator 24, CR
A signal with the same pulse width T as the pulse width T of Domon No. 13 a (see Figure 2 A) output from the T controller I roller 11 is generated using a resistor R3 and a capacitor C4, and the synchronizing signal a is regenerated. (Figure H).

Therefore, the horizontal frequency of the signal supplied from the personal computer 10 can be easily and reliably detected without affecting other circuits that use the peer signal.

In this embodiment, a personal computer is used as the signal supply device and a CRT is used as the display means, but the present invention is not limited to this.

Further, the configuration of the horizontal frequency switching circuit y3 in this example is only an example, and is not limited to this.

In the above description, the pulse width of the horizontal synchronizing signal is varied, but the horizontal frequency can also be detected by varying the pulse width of the vertical Ill signal.

"Effects of the Invention" As explained above, the present invention provides a signal supply device capable of varying the horizontal frequency.
The present invention is characterized in that the pulse width of the horizontal or vertical synchronizing signal at the position can be varied in accordance with the horizontal frequency.

Therefore, by adding information for detecting the horizontal frequency to the horizontal or vertical synchronizing signal supplied from the signal supply device, the display means can easily detect the horizontal frequency in real time.

On the side of a display means such as a CRT, the horizontal frequency of the supplied signal can be easily and reliably detected by a detecting means having a simple configuration.

Furthermore, the horizontal frequency in the display means can be quickly switched.

Therefore, the horizontal frequency cut-off circuit according to the present invention is extremely suitable for application to the above-mentioned personal computers and the like.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the circuit configuration of a horizontal frequency switching circuit according to the present invention, and FIG. 2 is a timing chart of each signal of the horizontal frequency switching circuit according to the present invention. ]...Horizontal frequency switching circuit 2...Detection means 10...Signal supply device 12...Pulse width variable circuit 14...Switching means 20...Display means

Claims (1)

[Claims] (1) A signal supply device capable of varying the horizontal frequency, comprising: a variable pulse width circuit that varies the pulse width of a horizontal or vertical synchronizing signal based on a horizontal frequency selection mode; 1. A horizontal frequency switching circuit comprising switching means for switching depending on a selection mode.