JPH0610380Y2 - LED defect detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial field of application) The present invention relates to an LED defect detecting device in an LED display circuit for processing an input signal and performing a predetermined display.

(Prior Art) Conventionally, as a display circuit for displaying the magnitude of the DC signal V _1N by a bar, for example, a DC signal V _1N as shown in FIG.
A / D converter ₁ for converting the signal into a digital signal D _1N , for example, four bar display LEDs 3 to 6 containing 8 elements, and LED 3
1 to 6 are sequentially selected in a ring shape, and during the conversion cycle T _AD of the A / D converter 1, for example, the LED decode circuit 7 that outputs the LED decode signal SLD that makes two cycles and the digital signal D _1N and the LED decode signal SLD are used as address signals, and each address corresponds to each element of the LED, for example, 8
Bit binary display signal I _D is stored, and 4 LEs are stored.
R which outputs the display signal _ID by the signal line common to D3 to 6
I used a circuit consisting of OM2.

FIG. 4 shows a time chart of this circuit.

As shown in FIG. 4, in order to prevent the display bleeding phenomenon, the LED decode signal SLD generally has a pause time t in which no LED is selected (“0”) while the LEDs 3 to 6 are selected.
Indicates that the LED is not lit), and the data of the display signal _ID of the address of the ROM 2 at that time is the data for turning off the LED.

(Problems to be solved by the invention) According to the above conventional configuration, when an LED failure occurs, the ROM 2
It is difficult to determine whether it is due to poor memory or due to a defect in the LED, and a visual inspection is required to confirm the defect in the LED, resulting in poor maintainability.

To check the LED, the LED has to be removed, which requires more confirmation work.

It was necessary to check the data stored in the ROM and the LED separately, which resulted in an increase in test time.

The present invention has been made to solve the above problems, and enables visual inspection with a simple operation, eliminates the LED inspection test, reduces cost, shortens test time, and facilitates maintainability. It is an object of the present invention to provide an LED defect detection device that can be realized.

[Configuration of Device] (Means for Solving Problems) In order to achieve the above-mentioned object, the LED decode signal of the LED decode circuit is used as the data of the address of the ROM selected during the pause time when no LED is selected. The data for lighting all the segments of is stored, and when the LED decoding signal changes from the pause state of the LED selection to the next selection, all the segments of the LED are lighted for a short time.

(Operation) Therefore, all of the selected LEDs are lit up and the unlit LEDs are detected as a defect only for a short time when the display is switched from the rest state to the data display.

(Examples) Examples will be described below with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of an LED defect detecting device according to the present invention.

In the present embodiment, all the LEs are turned on by turning on all the display signals _ID of the address when the LED decode signal SLD is the rest time t when no LED is selected (for example, all the bits are “1”).
It was configured to light D minutely.

The operation will be described with reference to the time chart of FIG. When the LED decode signal SLD selects any one of the bar display LEDs 3 to 6, the ROM 2 is responsive to the magnitude of the DC signal V _1N .
The stored display signal _ID is output to each LED.

Further, when the LED decode signal does not select any of the LEDs 3 to 6, the display signal _{ID of the} ROM 2 is data for all lighting (all bits “1”). When the LED decode signal SLD is to select the next LED, switching despite the display signal I _D of ROM2 is because the delayed time _delta t against switching despite the LED decode signal SLD, time of the selected LED is _delta t Only all lights up.

By selecting the ratio of the LED selection time T _S of the time _delta t and LED decode signal SLD of the full lighting without mistake viewing the display of the LED of the regular, it can be micro-lighted.

In addition, the LEDs 3 to 6 are all minutely lit by the dynamic display. In short, the inspection operation by the inspection signal and the inspection switch is unnecessary, and the LED trouble can be detected by a simple method.

It is obvious that the same effect can be obtained even if the display content is not a bar display but a numerical display.

[Effect of the Invention] As described above, according to the present invention, the LED can be easily inspected, and the cost can be reduced by saving the test time.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention, FIG. 2 is a time chart for explaining the operation, FIG. 3 is a configuration example diagram for explaining a conventional technique, and FIG. 4 is a time chart for explaining the operation of FIG. Is. 1 ... A / D converter, 2 ... ROM 3 to 6 ... LED display, 7 ... LED decoding circuit

Claims (1)

[Scope of utility model registration request] 1. A specific display is performed using display data.
LEDs, an LED decoding circuit for sequentially selecting one of the LEDs in a ring shape, an input digital signal and the L
In an LED display circuit which comprises an ED decode signal as an address signal and a ROM which stores n-bit display data corresponding to the input digital signal at each address, and which performs a dynamic display based on the input digital signal,
Which LED is included in the LED decode signal of the LED decode circuit?
The data for lighting all the LED segments is stored as the data of the ROM address selected during the non-selected idle time, and when the LED decode signal changes from the LED selection pause state to the next selection, all the LED segments LED defect detection device characterized by turning on the LED for a short time.