JPH03107199A - Operation mode switching device - Google Patents

Abstract

PURPOSE:To decrease patterns and the number of lead wires when a circuit system is going to be packed on a printed circuit board by setting the constant corresponding to a control voltage, thereby decreasing the signal wires to just one piece at the time of switching of three operation modes. CONSTITUTION:The circuit constant is so set that the control voltages from detecting circuits 14, 16 are respectively 0V and that HSF is made into 15kHz by the constant to be set at the off of control transistors Q1, Q2, when the frequency of the input horizontal synchronizing signal HS is 15kHz. The circuit constant is switched and controlled to such constant that only the control voltage from the circuit 14 attains 15V and the Q1 turns on to cause the HSF to attain 24kHz when the signal HS attains 24kHz. The circuit constant is so selected that 5V, 10V are respectively outputted form the circuits 14, 16, that only the 10V is impressed to a signal line L and that the Q2 turns on and the HSF attains 31kHz when the frequency of the signal HS attains 31kHz.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to an operation mode switching device suitable for application to a display device connected to a computer or the like.

"Prior Art" A display device connected to a computer is provided with an operation mode switching device as shown below.

That is, the video signal output from the computer has different horizontal frequencies supplied to the display device depending on the output resolution. For example, the horizontal frequency is 15 kHz or 24 kHz depending on the resolution.

Different horizontal frequencies, such as 31 kHz, are output.

A multi-scan operation mode switching device is provided so as to operate as a multi-scan display device compatible with such a plurality of horizontal frequencies.

FIG. 2 shows a conventional example of this operating mode switching device 1o, and a terminal 12 is supplied with a horizontal synchronizing signal output from a computer terminal.

As described above, this horizontal synchronization signal is, for example, 15 kHz or 24 kHz in response to multi-scanning.

A horizontal frequency of 31 kHz is selected.

The horizontal synchronization signal supplied to the terminal 12 is supplied to the first and second detection circuits 14 and 16. First detection circuit 14
In this case, it is configured to transversely transmit a frequency of 24kHz,
Further, the second detection circuit 16 is configured to detect a frequency of 31 kHz.

The outputs of the first and second detection circuits 14.16 are connected to the signal lines L1. It is supplied to the constant switching circuit 2° via L2.

As shown in the figure, the constant switching circuits 20 each have signal lines L1.
Control transistor Q1.L2 corresponds to control transistor Q1. Q2 are provided, and these control transistors Q1 .
By controlling Q2, the constant is switched. The constant is, for example, a constant for forming a horizontal deflection frequency, and by appropriately selecting the constant, a horizontal deflection frequency corresponding to the above-mentioned horizontal frequency can be obtained.

Signal line L1. A third control transistor Q3 is further connected between L2, and the control transistor Q3 is turned on by the control voltage obtained on the signal line L2, and the output level of the signal line L1 is grounded.

Now, in the operation mode switching device 10 configured in this way, the first detection circuit 14 detects the frequency of 24kHz, so only when a 24kHz horizontal synchronization signal is input manually, a predetermined signal is applied to the signal line L1. An output voltage (5V in this example) is output. Therefore, if the frequency of the horizontal synchronization signal is other than 15kHz,
The output voltage becomes OV.

Similarly, the second detection circuit 16 detects a frequency of 31 kHz, and outputs a predetermined voltage (5V in this example) only when a 31 kHz horizontal synchronizing signal is input. When a horizontal synchronization signal is input, Ov is output in all cases.

Therefore, when a 15kHz horizontal synchronizing signal is input to terminal 12, signal line L1. Since the output voltage of both L2 is OV, the control transistors Ql and Q
2 are both in the off state. The operation mode set by the constant switching circuit 20 in this control state is 15
The circuit constants of the horizontal deflection system are set to provide a kHz horizontal scanning mode.

In this state, when the frequency of the horizontal synchronizing signal now reaches 24 kHz, only the control transistor Q+ is turned on, so that the circuit constants of the horizontal deflection system are switched so that the operation mode becomes 24 kHz.

Similarly, when the frequency of the horizontal synchronizing signal becomes 31 kHz, only the control transistor Q2 is turned on, so that its constant is switched so that the horizontal deflection frequency becomes 31 kHz.

At this time, the control transistor Q3 is turned on, and the signal line L
The output voltage of l is fixed at 0■. As a result, the control transistor Q1 is held in the off state, so that the constant of the constant switching circuit #i20 is determined only by the control transistor Q2.

"Problem to be Solved by the Invention" By the way, in the conventional operation mode switching device 10 configured as described above, when the display device is configured to switch between three operation modes, at least one signal line is You will need two pieces.

On the other hand, as a practical matter, such an operation mode switching device 1
0 on a printed circuit board, circuits that require switching depending on the operating mode are usually distributed on the printed circuit board, so in such cases, multiple signal lines are always connected to the circuit. It is necessary to connect by pattern or lead wire.

However, in the case of connection using a pattern, this leads to a decrease in the degree of integration of the printed circuit board, and in the case of connection using a lead wire, this becomes a factor of increased cost.

Therefore, the present invention solves these conventional problems, and even when switching between at least three operation modes, the switching control can be performed using a single signal line. It has been made possible.

This makes it possible to eliminate all of the above-mentioned defects in printed wiring.

"Means for Solving the Problems" In order to solve the above-mentioned problems, the present invention detects the frequencies of at least three human-powered horizontal synchronization signals and generates a control voltage for operating mode switching corresponding to the detected frequencies. First and second control voltage generation means, and means for wire-ORing the three control voltages output from the first and second control voltage generation means, each having a different voltage level, through a forward diode, respectively. and a constant switching means to which a wired-OR control voltage is supplied, and the constant switching means is configured to select a corresponding operation mode by switching to a constant corresponding to the control voltage. It is characterized by:

"Function" When the frequency of the horizontal synchronizing signal is 15 kHz, the output control voltages of the first and second detection circuits 14 and 16, which function as means for generating control voltages for switching operation modes, are both 0. It is. Therefore, the control transistor Q1 . connected to a single signal line. Q2 is both off. As a result, in the off state, the constant switching circuit 2θ switches the constant so that the horizontal scanning frequency becomes 15kHz, and enters the first operation mode (first scan mode).
is set to

When the frequency of the horizontal synchronizing signal is 24kHz, the control voltage of only the first detection circuit 14 is 5■, and the control voltage of the second detection circuit 16 is OV, so the control voltage of 5■ is , control transistor Q1 . Supplied to Q2.

Since a Zener diode DZ that turns on at a voltage of 5■ or more is connected to the base side of the control transistor Q2, when the control voltage is 5■, the control transistor Q1
Turn on only. At this time, the horizontal scanning frequency is 24kHz
The constant is switched so that Now the second
The operation mode (second scan mode) is selected.

Further, when the frequency of the human horizontal synchronization signal is 31 kHz, the first detection circuit 14 outputs a control voltage of 5V, and the second detection circuit 16 outputs a control voltage of 10V.

As a result, in this case, only the diode D2 is turned on, thereby reverse biasing the diode D1, so that only the control voltage of IOV is output to the signal line Ll. This control voltage! Since the Zener diode DZ is turned on due to the second current, the control transistor Q2 is turned on.

Since the control transistor Q3 is also turned on as the Zener diode DZ is turned on, the control transistor Q1 is controlled to be in the off state. As a result, when the frequency of the horizontal peer signal is 31 kHz, only the second transistor Q2 is turned on. By turning on the second control transistor Q2, its constant is switched so that the horizontal scanning frequency becomes 31 kHz. The third operation mode (third scan mode) is now selected.

Therefore, according to this configuration, even when switching between at least three operation modes, only one signal line is required, so even when mounting this circuit system on a printed circuit board, patterns can be reduced or The number of lead wires can be reduced.

Embodiment Next, a case in which an example of the operation mode switching device according to the present invention is applied to the above-mentioned multi-scan display device for a computer will be described in detail with reference to FIG.

As mentioned above, the number of multi-scans is 3 (1
5kHz, 24kHz and 31kHz) are exemplified.

A horizontal synchronization signal is input to the terminal 12. As mentioned above, this horizontal synchronization signal is supplied from the terminal side of the computer. The horizontal synchronization signal is supplied to first and second detection circuits 14 and 16 that function as control voltage generation means for generating a control voltage for switching operation modes.

The first detection circuit 14 is for detecting a frequency of 24kHz, and when a horizontal synchronization signal of 24kHz or more is input, the control voltage obtained from this becomes a predetermined voltage, for example, 5V. Output. However, 24k
For frequencies below Hz, ie 15 kHz, the control voltage is 0.

Similarly, in the second detection circuit 16, the predetermined control voltage (I
OV) is obtained, and when a horizontal comrade signal of other frequencies, 15kHz or 24kHz, is manually generated,
In both cases, the control voltage is OV.

The control voltages output from the first and second detection circuits 14 and 16 are connected to diodes DI and DI connected in the forward direction, respectively.
It is configured to be wired-ORed via D2. Diode D1. Both D2 are diodes for blocking backflow.

The wired-ORed control voltage is supplied to the constant switching circuit 20 via a single signal line.

As described above, the constant switching circuit 20 includes the first and second control transistors Q1. Q2 is provided, and the control voltage transmitted through the signal line is supplied to the first control transistor Q1 and is also supplied to the second control transistor Q2 via the Zener diode DZ.
control transistor Q2.

Further, a third control transistor Q2 is connected to the base of the second control transistor Q2.
transistor Q3 is connected, and the second transistor Q
2 is turned on, the third control transistor Q
3 is turned on, and the first control transistor Q1 is controlled to be turned off.

The first control transistor Q1 has a horizontal scanning frequency of 24k.
The second control transistor Q2 is a transistor for setting the constant so that the horizontal scanning frequency is 31 kHz.

The Zener voltage of the Zener diode DZ mentioned above is 5
■It is set to 10V or more.

Next, the operation of the operation mode switching device 10 according to the present invention will be explained.

First, when the frequency of the human-powered horizontal synchronization signal is 15kHz, the control voltages output from the first and second detection circuits 14.16 are both OV, so the control voltages transmitted by the signal line Depending on the first and second control transistors Q1. Both Q2 maintain an off state.

As a result, these first and second control transistors Ql
, It is assumed that the circuit constants are set so that the horizontal scanning frequency is 15 kHz by the constants set when Q2 is in the off state. This operating mode is the first operating mode (first scan mode).

When the frequency of the human-powered horizontal synchronizing signal reaches 24 kHz, a 5V v control voltage is generated only from the first detection circuit 14, so in this case, this is applied to the first control transistor Q! via the diode DI. , the first control transistor Q1 is turned on and the horizontal scanning frequency is switched to a constant of 24 kHz. This is the second operation mode (second scan mode).

Note that in this operation mode, since the Zener diode DZ remains off, the second control transistor Q2 remains off.

Next, when the frequency of the human horizontal synchronization signal reaches 31kHz, the first detection circuit 14 outputs a control voltage of 5■, and the second detection circuit 16 outputs a control voltage of 1OV, but each is the diode D1. Since it is wired-ORed by D2, only the forward direction diode D2 is conductive, and the other diode D1 is in a reverse bias state, so that only the control voltage of IOV is applied to the signal line.

Since the Zener voltage of the Zener diode DZ is selected to be between 5V and 10V, when a control voltage of 10V is applied, the Zener diode F'DZ turns on and the second control transistor Q2 turns on. do. As a result, circuit constants are selected so that the horizontal scanning frequency is 31 kHz. This is because in the third operation mode (third scan mode), the third control transistor Q3 is turned on, which controls the first control transistor Ql to be off. The constant switching is performed only by the second control transistor Q2.

In this way, even if there are three or more operating modes, if you set three voltages with different levels as control voltages for switching each operating mode, you can switch between three operating modes by simply using a single signal line. It becomes possible to switch between two operating modes.

In the above-mentioned operation mode switching device 10, the first and second control voltage generation means for obtaining the control voltage for operation mode switching are not limited to a detection circuit, and for example, a frequency/voltage converter may also be used. can. When this frequency/voltage converter is used, a control voltage proportional to the frequency of the human-powered horizontal synchronization signal is directly output, so that the same effect as described above is obtained.

Further, in the above description, the third control transistor Q3 is used to control the transition to the first operation mode when setting the third operation mode, but it is also possible to not use the third control transistor Q3. It is possible to configure

For example, in the case of a 24 kHz manual horizontal synchronization signal, the first control transistor Ql is turned on, thereby correcting the constant. When a 31 kHz horizontal synchronization signal is input, this first control transistor Ql is turned on in addition to the second control transistor, and the circuit constants are set so that a horizontal scanning frequency of 31 kHz can be obtained only by each of them. . In this way, the third control transistor Q3 can be omitted.

In the above description, the voltage levels are weighted using OV, 5V, and IOV as control voltages corresponding to the three operation modes, but the values of the voltage levels to be weighted are arbitrary and are not limited to the above examples. do not have.

"Effects of the Invention" As explained above, in this invention, by using control voltages with different weighting as control voltages corresponding to the operation modes, the signal line of the control voltage to be transmitted to the constant switching circuit can be used. It has been modified so that it can be replaced with a single signal line.

Therefore, according to this, even when mounting an operation mode switching device on a printed circuit board, only a single conductive wire (turn) is required, so it is possible to improve the degree of integration of the printed circuit board. Even in such a case, one lead wire can be omitted, so it is possible to reduce costs.

Therefore, the operation mode switching device according to the present invention is extremely suitable for application to a multi-scan display device used as an output terminal device of a computer as described above.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a connection diagram showing an example of an operation mode switching device according to the present invention, and FIG. 2 is a connection diagram of a conventional operation mode switching device. Ql. D.I. Q2゜1 4゜D2・Dispute・Diode DZ・・・Zener diode L・・・Signal line Q3・Content・1st to 3rd control transistor 10・Operation mode switching device 16・Control voltage generation means Detection circuit 20 that functions as a constant switching circuit Applicant Sharp Corporation

Claims (1)

[Claims] (1) First and second control voltage generating means that detect the frequencies of at least three input horizontal synchronizing signals and generate control voltages for switching operation modes corresponding to the frequencies; The control voltage generating means includes means for wire-ORing three control voltages each having a different voltage level outputted from the control voltage generating means through forward diodes, and constant switching means to which the wired-ORed control voltages are supplied. . An operation mode switching device, characterized in that the constant switching means is configured to select a corresponding operation mode by switching to a constant corresponding to the control voltage.