JPS61235896A - Abnormality detection circuit for dynamic display system - 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] Technical Field The present invention relates to an abnormality detection circuit for a dynamic display system, and in particular is used to drive a protection circuit to prevent display elements from being destroyed when a failure occurs in a dynamic lighting type display device. This invention relates to an abnormality detection circuit for a dynamic display system.

A conventional protection circuit for a display system is constructed as shown in the block diagram of FIG. In the figure, a display location selection circuit 1 generates a lighting selection signal 12 using a display location selection signal 10 and a display location identification signal 11 from a pulse generation circuit 2, and this signal 12 is converted into a matrix. Input to circuit 3. The matrix conversion circuit 3 converts the lighting selection signal 12 into a display element selection signal 13, and this display element selection signal 13 is directly output as a display element lighting drive signal 14 via the protection switch circuit 4.

This display element lighting drive signal 14 is configured to selectively turn on any one of the four display elements 81 to 84, for example, as shown in FIG. The display element lighting drive signal 14, which is the circuit output, is connected to the signal line x1. ×2. This corresponds to Y and Y2.

For example, when the signal line x1 becomes high level and the signal line Y1 becomes low level at the same time, the display element (LED) 81
It is as if only the display is selectively driven and turned on.

As shown in FIG. 5, the display element protection circuit for a dynamic display system having such a configuration includes an oscillation stop detector 5 that monitors the output pulse of the pulse generation circuit 2, and a state of the output signal 12 of the display location selection circuit 1. It consists of a non-selectable detector 6, which monitors the input/output signals 12 and 13 of the matrix conversion circuit 3, and a conversion abnormality detector 7, which monitors the signal states of the input/output signals 12 and 13 of the matrix conversion circuit 3, and constantly monitors the functions of each circuit block 1 to 3. If an abnormality occurs in any block, the abnormality detection signal 1
5, 16, or 17 to drive and control the protection switch circuit 4.

In this way, if an abnormality occurs in the display system, the switch circuit 4 is turned off and the display element lighting drive signal 14 to the display element section shown in FIG. 6 is cut off, thereby protecting the display element. -ing

In this configuration, since an abnormality detection function is added to each of the functional blocks 1 to 3 of the display system, the circuit configuration becomes complicated and large-scale, which causes high costs.

11. An object of the present invention is to provide an abnormality detection circuit for a dynamic display system that can reliably detect abnormalities in the display system with an extremely simple circuit configuration.

1. An abnormality detection circuit for a dynamic display system according to the present invention includes an OR gate means which receives all the display selection signal lines that select the display drive of the display element, and a disconnection of the output of the OR gate means. and a signal generating means for detecting an abnormality detection signal and generating an abnormality detection signal.

11th day Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention, and portions and signals equivalent to those in FIG. 5 are designated by the same reference numerals and their explanations will be omitted. In the figure, an OR gate 8 which inputs all lines of the lighting selection signal 13 which is the output of the matrix conversion circuit 3, and an abnormality detector 9 which detects disconnection of this OR gate output 15 and generates an abnormal signal are provided. This detection output 16 becomes a drive control signal for the protection switch circuit 4.

FIG. 2 shows a specific example of the abnormality detection section shown in FIG.
(Monostable multivibrator) 9 is an example of an abnormality detector. The MMV 9 is a so-called retriggerable MMV that can be retriggered, and its time constant is set to be slightly larger than one cycle of the lighting selection signal 13.

FIG. 3 is a circuit example in which FIG. 2 is further detailed, and is an example in which the matrix of the matrix conversion circuit 3 is, for example, 4×4. All the signal lines of the display element selection signal 13 of this matrix conversion circuit 3 are commonly connected via unidirectional diode elements, respectively, in a so-called wired OR format, and this OR output 15 is an MMV.
9 re-trigger input.

FIG. 4 shows an example of the timing waveforms of signals 15 and 16. If the display system is operating normally, the lighting selection signal is sequentially transmitted to the signal lines X to X4 and Y1 to chronologically at a predetermined period. Since it is generated so as to scan Y4, the OR output 15 of this signal 13 is generated as shown on the left side of FIG.
has a waveform with almost continuous high levels. Therefore, since the output of MMV9 which uses this signal 15 as a trigger input is always retriggered, its output 16
shows a high level.

On the other hand, if an abnormality occurs somewhere in the display system, OR output 1
5 is disconnected for at least one cycle, so MM
Retriggering of V9 becomes impossible.

As a result, the signal 16 transitions to a low level, making it possible to detect an abnormality in the display system. If this detection signal 16 is used to control the relay coil 41 of the protection switch circuit, the relay will be released and the relay contacts will be turned off in the event of an abnormality, making it possible to protect the display element.

In the above, the abnormality detection signal 16 is used to drive the protection switch, but this detection signal 16 may also be used for warning such as abnormality display.

1. As mentioned above, according to the present invention, all abnormalities in the display system can be easily detected with an extremely simple configuration, which results in the simplification of the circuit and the reduction in the number of parts used. This has the effect of reducing overall circuit failure.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 and FIG.
4 is a specific example circuit diagram showing the details of the embodiment of the present invention, FIG. 4 is a timing chart showing the operation of the embodiment of the present invention, and FIG.
The figure is a block diagram of a conventional abnormality detection circuit for a display system, and FIG. 6 is a diagram for explaining a method of driving a dynamic display element. Explanation of symbols of main parts 8...ORGATE 9...MMV

Claims (2)

[Claims] (1) An abnormality detection circuit for a dynamic display system that dynamically controls the display of a display element, which includes an OR gate means that receives all of the display selection signal lines that select the display drive of the display element; 1. An abnormality detection circuit for a dynamic display system, comprising signal generation means for detecting a disconnection of the output of the sum gate means and generating an abnormality detection signal. (2) The abnormality detection circuit according to claim 1, wherein the signal generating means is a retriggerable monostable multivibrator having a time constant larger than one cycle of the display selection signal. .