JPH0335684B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a matrix drive device, and in particular,
The present invention relates to a matrix drive device that scans and drives and controls each diode in a diode matrix formed of a plurality of light emitting diodes.

(Technical background of the invention and its problems) For example, an optical coordinate input device includes a light emitting element array. A plurality of light emitting diodes are arranged in a matrix in this array, and each light emitting diode is designed to emit light and be driven when the row and column signals as scanning signals coincide with each other in timing.

Incidentally, the scanning signal is a rectangular pulse signal, and in this type of input device, if a failure occurs in the scanning signal generating section and the scanning signal is fixed, the scanning signal is not fixed at the corresponding row-column position. Only the light emitting diodes present are continuously emitted and driven. Therefore, the lifespan of this light emitting diode is shortened,
Another drawback was that it could be destroyed by continuous driving.

(Object of the Invention) An object of the present invention is to provide a matrix drive device having a configuration in which the light emitting diode is not driven even if a scanning signal specifying the light emitting diode is fixed.

(Summary of the Invention) The present invention is characterized in that the driving of the driving means for causing the light emitting diode to emit light is stopped when the scanning signal is fixed.

(Embodiments of the Invention) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a matrix drive according to the invention. This matrix drive device includes a diode matrix including a light emitting diode D,
This diode matrix has an arrangement of m rows and n columns. That is, the (m×n) light emitting diodes are arranged in a matrix as D ₁₁ to D _1o , D ₂₁ to _{D 2o} , . . . D _n1 to _{D no} .

Signals for driving and controlling these light emitting diodes D are supplied via the CPU 10. That is, the row signal output terminal of the CPU 10
A plurality of row control signals Sl ₁ to Sl _p are output from Ol ₁ to Ol _p , and
A plurality of column control signals Sr ₁ -Sr _g are output from column signal output terminals Or ₁ -Or _g of the CPU 10, respectively. A plurality of row control signals Sl ₁ to Sl _p are supplied to the row address decoder 2.
0 signal input terminals _I1 to _Ip , respectively.
The plurality of column control signals Sr ₁ -Sr _g are supplied to signal input terminals I ₁ -I _g of the column address decoder 30, respectively.

Signal output terminal O ₁ of row address decoder 20 ~
O _n is m PNPs driving the row side of the diode matrix through PNP transistors T ₁ to _{T n}
They are connected to the bases of the transistors Ql ₁ to Ql _n , respectively, and the row signals SL ₁ to _{SL n} as scanning signals
Output. The bases of transistors T ₁ -T _n are commonly connected and grounded.

Also, the signal output terminal of the column address decoder 30
O ₁ to O _o are n transistors that drive the column side of the diode matrix through PNP transistors T′ ₁ to T′ _o .
They are connected to the bases of NPN transistors Qr ₁ to Qr _o , respectively, and output column signals SR ₁ to _{SR o} .
The bases of the transistors T′ ₁ to T′ _o are commonly connected to the Q terminal of the retriggerable monostable multivibrator 40 . In this embodiment, the retriggerable monostable multivibrator 40 is implemented as an IC.
An HD74LS123 is used and has A and B inputs and a Clear input. The A input is fixed at "L", the B input is fixed at "H", and the Clear input is connected to the control terminal CON of the CPU 10. This retriggerable monostable multivibrator 40
If the A and B inputs are fixed as described above, when a "H" pulse signal is input to the Clear input, a "L" pulse signal will be output from the terminal, and a "L" pulse signal will be output to the Clear input. When a pulse signal is input, the terminal changes to "H". and,
When the Clear input is held at “L” or “H”,
The Q terminal is maintained in the "H" state.

The emitters of the transistors Ql ₁ to _{Ql n} are commonly connected to a drive voltage (+Vc.c.) source, and their collectors are commonly connected to the anode side of the light emitting diodes in each row. Also, the transistor Qr ₁ ~
The emitters of Qr _o are commonly connected and grounded, and the collectors of each are commonly connected to the cathode sides of the light emitting diodes in each column via resistors R ₁ to _{R o} , respectively.

Next, the operation of the matrix drive device according to the present invention will be explained below.

The CPU 10 receives a pulse signal of a predetermined period from a pulse oscillator (not shown), and in response to the pulse signal, generates row control signals Sl _{1 to 1} to cause each light emitting diode in a desired row and column of the diode matrix to emit light continuously one by one. Sl _p and column control signals Sr ₁ to _{Sr g} are output. In this case, both control signals Sl ₁ ~ Sl _p and Sr ₁ ~
Output Sr _g . In this case, both control signals Sl ₁ ~ Sl _p
and Sr ₁ to Sr _g are all rectangular wave signals.

Now, as an example, consider the case where the diode D ₂₂ emits light. This diode _D22 is located in the second row and second column, and the row address must be "2" and the column address must be "2".

Therefore, the CPU 10 outputs the row control signal Sl ₂ and also outputs the column control signal Sr ₂ . Therefore, the signal input terminals of the row address decoder 20 "I _p . . . I ₂ ,
Since the address signal "0...1,0" will be input to " _I1 ", the row address decoder 20
decodes this address signal as "2" and outputs the row signal SL ₂ as a scanning signal from the signal output terminal O ₂ . Further, since the address signal "0...1, 0" is input to the signal input terminal "Ig...I ₂ , I ₁ " of the column address decoder 30, the column address decoder 30 receives this address signal. is decoded as "2", and the column signal SR ₂ is output as a scanning signal from the signal output terminal O ₂ .

Incidentally, the signal output terminals O ₁ to _On of the row address decoder 20 are held at "H" during non-scanning, and the row signal SL ₂ for the second row mentioned above is output as an "L" signal. Therefore, the collector of the transistor _T2 changes to "L" and is turned on, so that the base voltage of the drive transistor _Ql2 in the second row changes to "L". On the other hand, the signal output terminals O ₁ to _{O o} of the column address decoder 30 are held at "L" during non-scanning, and the column signal SR ₂ of the second column mentioned above is output as an "H" signal. In addition, the CPU 10 outputs a control terminal every time it outputs a column signal.
Since the “H” pulse signal P is output from CON,
This pulse signal P is input to the Clear input of the retriggerable monostable multivibrator 40, and the terminal changes to "L". As a result, the bases of transistors T' ₁ to T' _o are switched to "L". Therefore, transistor T′ ₂ is connected to the column signal
SR ₂ changes the emitter to “H” and turns ON.
Therefore, the base voltage of the second column drive transistor _Qr2 changes to "H". Therefore, positive voltage source + Vc.c. → emitter-collector of transistor Ql ₂ → diode D ₂₂ → resistor R ₂ → transistor
Since a closed circuit is formed from the collector/emitter of Qr ₂ to the ground, only the light emitting diode D ₂₂ is energized and emits light.

The above is the control operation when the diode _D22 emits light. When the other matrix diodes are caused to emit light, they are controlled by the signal states of the row control signals Sl ₁ -Sl _p and column control signals Sr ₁ -Sr _g output from the CPU 10, respectively.

By the way, if an abnormality occurs in the pulse oscillator or the CPU 10, for example, the row signal Sl ₂ and the column signal
_Sr2 is fixed at "L" or "H". Therefore,
The transistor Ql ₂ in the second row and the transistor Qr ₂ in the second column remain conductive, and the diode D ₂₂
Try to make it emit light continuously.

However, in this embodiment, the Clear input of the retriggerable monostable multivibrator 40 is connected to the control terminal CON of the CPU 10.
Therefore, if an abnormality occurs in the pulse oscillator or CPU 10, the control terminal CON of the CPU 10 will also be set to "L".
or “H”, so the retriggerable monostable multivibrator 4
Clear input of 0 is held at “L” or “H”,
The Q terminal is maintained in the "H" state. Therefore, transistors T' ₁ to T' _o become non-conductive, and all driving transistors Qr ₁ to Qr _o also become non-conductive.
As a result, not only the light emitting diode _D22 but also the other light emitting diodes D are not energized, thereby preventing their destruction.

Another embodiment of the invention is shown in FIG. In this embodiment, counter 1 and counter 2 of the CPU 10 count pulse signals from a pulse oscillator (not shown) and output row control signals Sl ₁ to Sl _p and column control signals Sr ₁ to _{Sr g} each time they are counted. . The counter 3 of the CPU 10 outputs a negative pulse signal P' every time a predetermined number of clocks are input from the clock circuit 10a. This negative pulse signal P' is applied to the bases of transistors T' ₁ to T' _o via a capacitor Ct and a resistor Rt. The time constants of the capacitor Ct and the resistor Rt are set to be the same as or larger than the pulse signal P'. Further, a power supply voltage +Vc.c. is applied to the bases of these transistors T' ₁ to T' _o via a resistor Rt. Note that the clock circuit 10a is also used for synchronizing each counter.

In this embodiment, the row address decoder 20 and the column address decoder 30 normally output the row signal.
Every time SL ₁ to _{SL o} and column signals SR ₁ to SR _o are output, a pulse signal P' is output from the counter 3 of the CPU 10, and this pulse signal P' is sent to the transistor.
Since T' to T' _o are turned on, the light emitting diodes D are sequentially scanned and emit light.

On the other hand, if an abnormality occurs in the pulse oscillator or the CPU 10, the counter 3 of the CPU 10 is fixed to either "L" or "H".
A power supply voltage +Vc.c. is continuously applied to the bases of the transistors T' ₁ to T' _o via a resistor RT. Therefore, transistors T′ ₁ to T′ _o become non-conductive, so
In the same way as described above, power to all the light emitting diodes D is stopped.

FIG. 3 shows yet another embodiment of the invention. In this embodiment, row address decoder 20
A one-shot multivibrator 50 with a reset is disposed between the signal output terminals O ₁ -O _n and the driving PNP transistors Ql ₁ -Ql _n , respectively. Further, signal output terminals O ₁ to _{O o} of the column address decoder 30 and driving NPN transistors Qr ₁ to Qr _o
A one-shot multivibrator 50' with a reset is disposed between the two. For example, as shown in FIG. 4, the multivibrator 50 has a reset input connected to each signal output terminal of the row address decoder 20, and a PNP transistor.
Equipped with terminals connected to each base of Ql ₁ to Ql _n ,
A time constant is set by the capacitor Ct' and the resistor Rt' so that a negative pulse is output from the terminal with a pulse width equal to or greater than the pulse width of the row signal. This multivibrator with reset 50 outputs a negative pulse from the terminal every time a negative pulse is input to the reset input. Therefore, when a row signal of "L" level, for example, row signal SL ₂ , is output from the row address decoder 20, a negative pulse is output from the corresponding terminal of the multivibrator with reset 50, and the PNP transistor Ql ₂ is turned on. do.

Also, the other multivibrator with reset 5
0' has a reset input connected to each signal output terminal of the column address decoder 30, and a Q terminal connected to each base of the NPN transistors QR ₁ to _{QR o} . A constant is set. This multivibrator with reset 50' outputs a positive pulse from the Q terminal every time a positive pulse is input to the reset input. Therefore, for example, when the column address decoder 30 outputs the column signal SR ₂ at the "H" level, a positive pulse is output from the Q terminal of the corresponding multivibrator with reset 50', turning on the NPN transistor QR ₂ . .
Therefore, the light emitting diode _D22 is driven and emits light.

On the other hand, if an abnormality occurs in the pulse oscillator or CPU 10, the row signals SL ₁ to SL _n and the column signals SR ₁ to
Since SR _o is fixed, all Q terminals of the group of multivibrators 50 with reset are held at "H" level, and multivibrator 50' with reset
All Q terminals of the group are held at "L" level. Therefore, driving transistors Ql ₁ to Ql _n and Qr ₁
Since ~Qr _o is maintained in a non-conducting state, all diodes D are de-energized.

In the embodiment shown in FIG. 3, the same effect can be obtained by simply using either the 50 group or 50' group of multivibrators with reset.

(Effects of the Invention) According to the present invention, the driving means for causing the light emitting diode to emit light is stopped when the scanning signal is fixed. It is possible to reliably prevent the light emitting operation from occurring. Therefore, it is possible to provide a matrix drive device that can cause the light emitting diodes to emit light stably over a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a matrix drive device according to the present invention, FIGS. 2 and 3 are circuit diagrams according to other embodiments of the present invention, and FIG. 4 is an example of a multivibrator with reset. It is a diagram. 10...CPU, 20, 30...Address decoder, 40...Retriggerable monostable
Multivibrator, 50, 50'...One-shot multivibrator with reset, Ql ₁ ~
Ql _n ...transistor, Qr ₁ ~Qr _o ...〃, D ₁₁ ~D _no
……Light emitting diode, Sl ₁ ~ Sl _p ……Row control signal,
Sr ₁ ~ Sr _g ...Column control signal.

Claims (1)

[Claims] 1. A diode matrix in which a plurality of light emitting diodes are arranged in a matrix; a scanning means for outputting a scanning signal for scanning the plurality of light emitting diodes; and a scanning means for outputting a scanning signal for scanning the plurality of light emitting diodes. A driving means for emitting and driving the light emitting diode; and a driving means for monitoring the changing state of the scanning signal and outputting a driving stop signal to the driving means at a fixed point in time when the change does not occur within a preset time. A matrix drive device comprising: a stopping means; 2. The matrix drive device according to claim 1, wherein the drive stop means is a monostable multivibrator.