JPH05158431A - Driving circuit for display element - Google Patents

Abstract

PURPOSE:To realize a display element driving circuit having a simple circuit configuration and capable of preventing an reverse bias from being applied on a display element and also capable of preventing a continuous current from being supplied, in a circuit for driving the display element in accordance with driving data. CONSTITUTION:In the display element driving circuit constituted of a display means 10, a driving means 20 for driving a display means 20, a driving data generating means 30 for setting data for turning on/off plural display elements 11 to 1n of the display means 10, a timing signal generating means 40 for generating a display timing signal for the display means 10 and a timing signal for detecting an alarm, a monitoring means 50 for detecting the abnormality of a driving signal for driving the display means 10 and outputting an alarm signal and a clearing means 60 for clearing the driving data generating means 40 when the abnormality is detected and the alarm signal is outputted by the monitoring means 50, the circuit is provided with a reverse bias preventing means 70 for preventing a reverse voltage from being applied on the display means 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit for driving a display element according to drive data. For example, in a building management system, a large number of display elements such as light emitting diodes are used to indicate the operating state and failure state of various equipment such as electric power, air conditioning, and elevators in a building.

Therefore, when a failure occurs in various equipment, it is necessary to take measures in accordance with the display of a display element such as a light emitting diode, and the display element is required to have high reliability.

Therefore, a driving circuit for driving these many display elements is required to have a simple structure and not damage the display elements even if a failure occurs in the driving circuit. ing.

[0004]

2. Description of the Related Art FIG. 4 shows a diagram for explaining a conventional example. The figure shows a light emitting diode (hereinafter, LED) as the display elements 11 to 1n.
(Hereinafter referred to as)) is used, which is an example in which 16 LEDs in one group are constituted by a total of 128 LEDs in 8 groups.

Reference numeral 21 in the drawing denotes a drive signal generation circuit, 31
Is a data setting circuit, 41 is a timing generation circuit, 51 is an alarm detection circuit, 52 is a flip-flop circuit (hereinafter referred to as FF circuit), 61 is a clear circuit, and L1 to L32
(L33 to L128 are not shown) is an LED, and
(I = 1 to 8, but i = 3 to 8 is not shown) is an LED
Driving transistors, Ri1, Ri2, Ri3, Rj
4 (j = 1 to 16, but j = 3 to 15 is not shown),
R is a resistor, Di1 is a diode, and PHi is a photocoupler.

In the figure, the signal from the drive signal generating circuit 21 is input to the base of the transistor Ti for driving the LED, so that the transistor Ti is sequentially turned on, and the LEDs L1 to 16 and the LEDs L17 to 32 are sequentially turned on.
16 LEDs in a group can be driven.

Here, the data setting circuit 31 converts the input data into an LED lighting signal and inputs it to the cathode side of the LED, and lights 16 LEDs according to each data.

In the conventional example, the LEDs L1 to L128 are composed of 8 groups and are driven periodically,
The current supplied to the LEDs L1 to L128 is about 3 of the normal value.
It is doubling.

Therefore, when the transistor Ti is short-circuited, a large current continuously flows through the LED, and the LED is damaged or deteriorated.
Further, since the electronic parts used in the vicinity of the LED may be deteriorated, the alarm detection circuit 51 detects an alarm, and the clear circuit 61 clears the data setting circuit 31 so that a continuous current does not flow to the LED. ing.

[0010]

In the above-mentioned conventional example, L
Reverse bias is applied to ED except during the drive period.
For example, when the transistor T1 is on, the transistor T2 is off, and the LEDL1 is on, the transistor T1 is on, so that its collector voltage is 11 V and L
Since the terminal voltage VF of EDL1 is 5V, the cathode voltage of LEDL1 is 6V. (LEDL1, LED17
The voltage of the line to which the cathode is connected is 6V
Becomes On the other hand, since the transistor T2 is off, its collector voltage is 1.6 V, and this voltage is applied to the anode of the LEDL17. The cathode of LEDL17 is an LED
Since the same potential as the cathode of L1 is applied, 6V is applied, and the reverse bias of 4.4V is applied to the LED L17. LEDL3 connected to transistors T3 to T8
Similarly, a reverse bias of 4.4 V is applied to 3 to L128.

Applying such a reverse bias to the LED causes damage or deterioration of the LED. The present invention does not apply a reverse bias to the display element, and
An attempt is made to realize a drive circuit for a display element having a simple circuit configuration capable of preventing continuous current from flowing.

[0012]

FIG. 1 is a block diagram for explaining the principle of the present invention. Reference numeral 10 in the figure denotes a display means including a plurality of display elements 11 to 1n, and 20 denotes the display means 1
0 is a drive means, and 30 is a display means 10.
Drive data generating means for setting data for turning on / off the plurality of display elements 11 to 1n.

Numeral 40 is a timing signal generating means for generating a display timing signal for the display means 10 and a timing signal for alarm detection, and numeral 50 is for detecting an abnormality of a drive signal for driving the display means 10 and outputting an alarm signal. Reference numeral 60 denotes a drive data generating means 40 when the monitor means 50 detects an abnormality and outputs an alarm signal.
It is a clear means for clearing.

Further, reference numeral 70 denotes a reverse bias preventing means which is provided in the drive circuit of the display element and prevents the reverse voltage from being applied to the display means 10. The means solves the problem.

[0015]

The display means 10 is composed of a plurality of display elements 11 to 1n. The drive means 20 applies a voltage for driving the display elements 11 to 1n.

In this state, the driving data generating means 30 receives the data D1 to Dn for independently driving the display elements 11 to 1n as an input, applies a voltage to the display elements 11 to 1n for displaying, and drives the driving means. Only the display element to which the voltage is applied from 20 and the drive data generating means 30 displays.

The monitoring means 50 is the timing signal generating means 4
An abnormality of the drive signal is monitored by a timing signal generated by 0, and when an abnormality is detected, an alarm signal is output, and the clear means 60 clears the drive data generating means 30 by this alarm signal, and the display means 10 continues. Prevents energization.

Further, it is possible to prevent the reverse voltage from being applied to the display means 10 by the reverse voltage prevention means 70, and prevent the display means 10 from being damaged or deteriorated.

[0019]

FIG. 2 is a diagram for explaining an embodiment of the present invention.
Similar to the conventional example, the figure shows LEDs as the display elements 11 to 1n.
This is an example in which 16 LED elements in one group are configured in a total of 128 LED elements in 8 groups.

Reference numeral 21 in the drawing denotes a drive signal generating circuit, 31
Is a data setting circuit, 41 is a timing generation circuit, 51 is an alarm detection circuit, 52 is an FF circuit, 61 is a clear circuit, and L1 to L32 (L33 to L128 are not shown) are L
ED, Ti (i = 1 to 8, but i = 3 to 8 is not shown) is a transistor for driving LEDs, TD and TS are transistors, Di is a diode for preventing reverse voltage, and Ri is
1, Ri2, Ri3, Rj4 (j = 1 to 16, provided that j
= 3 to 15 are omitted), R is a resistor, Di1 is a diode, and PH1 is a photocoupler.

+ 12V is applied to the emitter of the LED driving transistor Ti. In the figure, a drive signal is generated by the drive signal generation circuit 21, and the drive signal is sequentially applied to the base of the LED driving transistor Ti through the diode Di1,
The transistors Ti are sequentially turned on. Therefore, LE
DL1-L16, LEDL17-L32 ... 1 group 1
The six LEDs can be turned on in sequence. TD in the drive signal generation circuit 21 is a transistor for driving the transistor Ti.

Here, in the transistor TS in the drive data setting circuit 31, the input data is converted into a lighting signal of the LED and is inputted to the cathode side of the LED through the resistor Rj4. Turn on the LEDs.

Also in this embodiment, as in the conventional example, LE
Since DL1 to L128 are composed of 8 groups and are dynamic drives of 1/8 cycle, LEDs L1 to L1
The current applied to 28 is about three times the normal value, and due to the afterimage effect, it appears to the human eye as if it were continuously lit.

The photocoupler PH1 detects an abnormality in the drive signal of the LED. The output is latched by the FF circuit 52 of the alarm detection circuit 51, and the output resets the data setting circuit 31 via the clear circuit 61. is doing.

In this embodiment, a reverse bias preventing diode Di is connected to the collector of the LED driving transistor Ti, the cathodes of the eight diodes Di are connected in parallel, and a photo is made through a resistor R13. It is input to the coupler PH1.

Since the collector of the transistor in the photocoupler PH1 is connected to + 5V through the resistor R in the alarm detection circuit 51, it outputs low when any of the transistors Ti is turned on.

With this configuration, when the transistor T1 is on, the transistor T2 is off, and the LEDL1 is on, the collector voltage of the transistor T1 is 11 V and the voltage drop of the diode D1 is 0.7 V, so that the cathode of the diode D1 is The voltage becomes 10.3V.

Since the cathode of the diode D1 is connected to the collector of the transistor T2 through the diode D2 in the opposite direction, the LEDs L16 to L32 are not reverse-biased. Although the LEDs L16 to L32 connected to the transistor T2 have been described as a representative here,
Similarly, the reverse bias is not applied to the LEDs L33 to L128 connected to T3 to T8.

FIG. 3 is a time chart of the embodiment of the present invention. The circled numbers in the figure show the signal waveforms at the points indicated by the circled numbers in FIG. This is the output of the drive signal generation circuit 21 that drives the transistor T1.

This is the output of the drive signal generation circuit 21 that drives the transistor T2. This is a signal output during a period when a signal for driving the transistors T1 to T8 is not input. Transistors Ti and T
There is a time difference between the signals for driving i + 1, and the signals are set to be off during normal times.

A indicated by a broken line in the figure is a transistor T1.
Is abnormal, the current is always on, and there is no time to turn off. It is a clock signal generated from the timing generation circuit 41.

This is the output of the FF circuit 52 which receives the signal of (1) with the clock signal of (3). This is the data for driving the 16 LEDs L of the data setting circuit 31, and it is detected that the transistor T1 is abnormal. Therefore, when the data is reset, the LED connected to this line does not pass the current.

[0033]

According to the present invention, the drive signal generating means for generating the drive signal for driving the display element is provided with the reverse voltage preventing means for preventing the application of the reverse bias. Reverse bias is not applied to the display element, and it is possible to prevent a large current from being continuously applied. Therefore, damage or deterioration of the display element can be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating the principle of the present invention.

FIG. 2 is a diagram illustrating an embodiment of the present invention.

FIG. 3 is a time chart of an example of the present invention.

FIG. 4 is a diagram illustrating a conventional example.

[Explanation of symbols]

10 Display Means 11 to 1n Display Elements L1 to L32 L
ED 20 drive means 21 drive signal generation circuit 30 drive data generation means 31 data setting circuit 40 timing signal generation means 41 timing generation circuit 50 monitoring means 51 alarm detection circuit 52 FF circuit 60 clear means 61 clear circuit 70 reverse bias prevention means T1 T2, TD, TS transistors R11, R12, R21, R22, R13, R23, R
14, R24, R164, R Resistors D1, D2, D11, D21 Diodes PH1, PH2 Photocoupler

Claims (2)

[Claims] 1. A circuit for driving a plurality of display elements (11 to 1n), comprising display means (1) comprising a plurality of display elements (11 to 1n).
0) and drive means (20) for driving the display means (10)
And a plurality of display elements (11 to 1n) of the display means (10)
Drive data generating means (30) for setting data for turning on / off, a timing signal generating means (40) for generating a display timing signal of the display means (10) and an alarm detection timing signal, and the display means ( Monitoring means (50) for detecting an abnormality of a drive signal for driving the driving means (10) and outputting an alarm signal; and the drive data generating means (50) for outputting an alarm signal when the monitoring means (50) detects an abnormality. 30) A display element drive circuit comprising a clearing means (60) for clearing, wherein a reverse bias preventing means (70) for preventing application of a reverse voltage to the display means (10) is provided. Device drive circuit. 2. The drive means (20) is composed of a transistor (Ti), and the reverse bias prevention means (70).
The drive circuit for the display element according to claim 1, wherein the drive circuit is constituted by a diode (Di) for preventing reverse bias connected to the collector side of the transistor (Ti).