JP2669163B2 - Ghost prevention keyboard matrix circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a personal computer, a word processor,
Alternatively, the present invention relates to a keyboard device that transmits a human command to a computer or a control device such as an information terminal device.

[0002]

2. Description of the Related Art A conventional keyboard device uses a so-called matrix circuit shown in FIG. 9 as a circuit for detecting which key of a plurality of key switches is being pressed. That is, each of the vertical and horizontal lines is composed of two lines, and a predetermined voltage (+5 V) is applied to predetermined resistors R ₁ and R ₂ , and the vertical line is grounded via the switching transistor Y ₁₂ . The horizontal lines are connected to the digital input circuits X ₁ and X ₂ . Key switches A, B, C, and D are provided at four places where the vertical line and the horizontal line cross and approach each other, and these two lines are connected. The switching transistors Y ₁ and Y ₂ are controlled by a microcomputer or the like so that they are sequentially turned on.

If the key switch A is depressed in this conventional example, when the switching transistor Y ₁ is turned on with the key switch A being depressed, the digital input circuit X ₁ is turned off. Voltage is LO
When the key switch A enters the W state, it is detected that the key switch A has been pressed. If the key switch B is pressed in the same manner, the voltage of the digital input circuit X ₂ is detected by to LOW state switching transistors Y ₁ is in the ON state. In the case where the key switch C is pressed, the voltage of the digital input circuit X ₁ switching transistor Y ₂ is in the ON state is detected by to LOW state. If further key switch D is depressed, the voltage of the digital input circuit X ₂ is detected by to LOW state switching transistors Y ₂ is in the ON state.

[0004]

However, in the method of detecting a key press by such a matrix circuit, for example, when three keys are pressed simultaneously in FIG. 9, another key which is not pressed is also pressed. It has the disadvantage of being detected as it was.

[0005] For example, as shown in FIG. 9, three key switches A, C, if D is depressed at the same time, when the switching transistor Y ₁ in the ON state, none of the digital input circuit X _1, X ₂ is LOW Thus, the key switch B is erroneously detected as being depressed. This is because if the three key switches A, C, and D are pressed down at the same time and the switching transistor Y ₁ is turned on, the current flowing from the power source to the switching transistor Y ₁ through the resistor R ₁ and the resistance from the power source are turned on. R ₂ , a current flowing to the switching transistor Y ₁ through the key switch C and the key switch A is generated, and both the digital input circuits X ₁ and X ₂ are at L level.
This is because the OW state is set. Such false detection is called a keyboard matrix ghost.

In order to prevent such a ghost, conventionally, as shown in FIG. 10, each key switch A, B, C,
There was a circuit in which diodes Da, Db, Dc and Dd were connected in series with D. In this circuit, when the three key switches A, C and D are simultaneously depressed, even if the switching transistor Y ₁ is turned on, the diode Dc works so that the resistance R ₂ and the key switches C and A are removed from the power supply.
The can prevent the current flowing to the switching transistor Y ₁ occurs through. As a result, the digital input circuit X ₂ is not brought into the LOW state, and the ghost can be prevented from occurring.

As described above, the conventional example shown in FIG. 10 is effective for preventing the occurrence of a ghost, but each key switch A,
The diodes Da, Db, Dc, and Dd must be connected to each of B, C, and D, which has a drawback that the manufacturing cost becomes high and the mounting process is complicated and troublesome.

It is an object of the present invention to solve such disadvantages and to provide an anti-ghost keyboard matrix structure which is advantageous in terms of manufacturing cost and mounting.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above-mentioned object. Means for detecting a current value supplied to this circuit, such as a keyboard matrix circuit, and a change in the current value are provided. A ghost prevention keyboard matrix circuit comprising: control means for determining that there is a possibility that a ghost signal has occurred when the value exceeds a predetermined value and not performing key press detection.

[0010]

Therefore, according to the present invention, attention is paid to the fact that the value of the current supplied to the circuit changes when a ghost occurs,
When this change becomes a value equal to or more than a predetermined value, it is determined that a ghost signal may have occurred, and the key press detection is not performed, thereby preventing the occurrence of a ghost.

[0011]

1 to 2 show an embodiment of the present invention. FIGS. 2 to 8 show the operation of the circuit of FIG.

FIG. 1 is substantially the same as FIG.
A resistor R for detecting a current value from the power source is provided on the side that supplies the power source. Also, AD is analog
It is a digital converter. The key switches A, B,
C, D, switching transistors Y _1, Y _2, a digital input circuit X _1, X _2, resistors R _1, R ₂ are same as the conventional, resistors R ₁ and R ₂ have the same resistance value.

Next, the operation of the matrix circuit and the fact that the current value changes when a ghost occurs will be described with reference to FIGS.

[0014] In FIG. 2, when the switching transistor Y ₁ is turned ON in a state where the key switch A is pressed, the resistance from the power source R, a current flows to the switching transistor Y ₁ through R _1. Thus the voltage of the digital input circuit X ₁ becomes a LOW state, it can be detected that the key switch A is pressed.

Similarly, when the key switch B is depressed, as shown in FIG. 3, the switching transistor Y ₁
When is turned on, the voltage of the digital input circuit X ₂ goes into the LW state, so that detection is performed.

When the key switch C is depressed,
As shown in FIG. 4, the switching transistor Y ₂ is O
Digital input circuit X ₂ is LOW when it is N state
Detection is performed when the state is reached.

Similarly, when the key switch D is pushed down, as shown in FIG.
₂ turns on, the digital input circuit X ₂ goes low.
When the O state is reached, detection is performed.

Next, a key switch A and a key switch C
If but the depressed simultaneously, the slip quenching transistor Y ₁ as shown in FIG. 6 the voltage of the digital input circuit X ₁ becomes a LOW state at ON state, the switching transistor Y ₂ is a digital input circuit X ₁ in the ON state When the voltage becomes LOW, the depression of the key switches A and C is detected. Note that the matrix circuit in the case where the key switch A and the key switch C is depressed at the same time, through the current flowing to the switching transistor Y ₁ from the power supply resistor R, through R _1, resistor from a power source R, the R ₂ , a current flowing through the key switch C and the key switches a through the switching transistor Y ₁ occurs. Therefore, the resistance of the matrix circuit becomes R + R _1/2 since the resistance R ₁ and the resistance R ₂ have the same resistance value.
To power supply V to the resistor R, the current of the _{V ÷ (R + R 1/} 2) flows. At this time, the input impedances of the digital input circuits X ₁ and X ₂ are so large that they can be ignored in this matrix circuit. Even if the key switch B and D is depressed at the same time in the same manner, as shown in FIG. 7, since the current through the current through resistor R ₁ a resistor R ₂ occurs, the resistor R, the resistors R ₁ and current V ÷ since the R ₂ have the same resistance value (R + R _1/2) flows.
That is, this current value becomes this value at least when the key switches A and C or the key switches B and D are simultaneously pressed.

The case where the ghost signal is generated in the keyboard matrix circuit of this embodiment is, for example, the case where the key switches A, C, and D are simultaneously depressed (FIG. 8). When the switching transistor Y ₁ is in the ON state, the digital input circuit X ₁
And X ₂ are both becomes LOW state, even following when the switching transient data Y ₂ are turned ON, the digital input circuit X ₁ and X ₂ are thus both a LOW state. Therefore, if it is left as it is, the key switch B is erroneously detected as being depressed. However, at this time,
Than that the value of the current flowing through the resistor R is _{V ÷ (R + R 1/} 2), the key switches A and C, the key switches B and D
It is detected that are pressed simultaneously.

Therefore, the value of the current flowing through the resistor R is detected,
When the current value exceeds a predetermined value, the key control means does not detect the key depression, so that when the ghost signal is generated (FIG. 8), the key is mainly detected and the key switch B is activated. It is possible to prevent erroneous detection of a pressed object. The fact that key press detection has not been performed by, for example, turning on an alarm lamp may be transmitted to a person operating the keyboard.

The value of the current flowing through the resistor R is detected by the voltage drop across the resistor R, and the analog-to-digital converter A
It shall be known as a digital value through D. Then, the microcomputer that controls the switching transistors Y ₁ and Y ₂ and reads the outputs of the digital input circuits X ₁ and X ₂ can judge the possibility of generating a ghost signal by reading the digital value.

In the present embodiment, the matrix circuit having four key switches A, B, C and D has been described as an example in FIGS. 1 and 2, but the present invention can be applied even if the number of key switches is increased. The basic principle is the same, and the present invention is generally applicable to a matrix circuit having an arrangement of n × m key switches.

[0023]

As is apparent from the above-described embodiment, the present invention is provided with means for detecting the current value supplied to the keyboard matrix circuit, judges the possibility that a ghost signal is generated by the change of the current value, and By not performing the press detection, it is possible to prevent erroneous detection of a key press due to the occurrence of a ghost. In particular, even in a large-scale keyboard matrix having a large number of key switches, it suffices to provide means for detecting the current value supplied to the entire circuit, and there is no need to provide a diode as in the conventional example for each key switch. Therefore, the manufacturing cost can be reduced, which is advantageous in terms of mounting in the manufacturing process.

[Brief description of the drawings]

FIG. 1 is a keyboard matrix circuit according to one embodiment of the present invention.

FIG. 2 is an operation explanatory diagram of FIG. 1;

FIG. 3 is an operation explanatory diagram of FIG.

FIG. 4 is an operation explanatory diagram of FIG.

5 is an explanatory diagram of the operation of FIG.

FIG. 6 is an operation explanatory diagram of FIG.

FIG. 7 is an operation explanatory diagram of FIG. 1.

8 is an explanatory diagram of the operation of FIG.

FIG. 9 is a diagram of a conventional keyboard matrix circuit.

FIG. 10 is a diagram of a conventional keyboard matrix circuit performing ghost prevention.

[Explanation of symbols]

R ₁ , R ₂ , R resistance Y ₁ , Y ₂ switching transistor X ₁ , X ₂ digital input circuit A, B, C, D key switch Da, Db, Dc, Dd diode AD analog-digital converter

Claims (1)

(57) [Claims] 1. In a keyboard matrix circuit,
A means for detecting the current value supplied to this circuit, and a control means for judging that a ghost signal may have occurred when the change in the current value exceeds a predetermined value and not performing key press detection. With anti-ghost keyboard matrix circuit.