JPH02278884A - Luminous intensity variable testing circuit for light emitting diode - Google Patents

Abstract

PURPOSE:To simultaneously conduct tests of a light emitting diode and a driving circuit by applying a defect signal to the base of a driving semiconductor terminal element to control it at the time of defect occurrence, generating a test signal at the time of testing the diode, and applying it to the base of the terminal element to control it. CONSTITUTION:A light emitting diode 1 is connected in series with a driving semiconductor 3 terminal element 2 for lighting it, one end of the circuit is connected to a DC voltage, and the other one end is connected to a ground. Defect signal output means 3 for applying a signal corresponding to the defect to the base of the element 2 when a defect occurs, to light the diode 1 to emit a light, and test signal generating means 4 for generating a test signal by turning ON, OFF a switch 5 applied at one end with a DC voltage, applying the test signal to the base of the element 2 to emit a light with the diode 1 set in a quasi-lighting state are provided. The element 2 is controlled so that the diode 1 can display both light emitting states of a lighting state and a guasi- lighting state. Thus, when the diode is tested, the tests of the diode and the driving circuit can be concurrently performed.

Description

[Detailed Description of the Invention] [Summary] Regarding a display test circuit that uses a light emitting diode to indicate a fault that occurs, when testing the light emitting diode, it is possible to simultaneously test the light emitting diode and the light emitting diode drive circuit. In order to provide a light emitting diode test circuit, a light emitting diode and a driving semiconductor three-terminal element for lighting the light emitting diode are connected in series, one end of the series connected circuit is set to a DC voltage, and the other end is set to a DC voltage. When a fault occurs in a circuit whose one end is connected to ground, a signal corresponding to the fault is applied to the base of the driving semiconductor three-terminal element, and a fault signal is output to turn on the light emitting diode and emit light. and test signal generating means for generating a test signal by turning on and off a switch to which a DC voltage is applied to one end, and applying the test signal to the base of the semiconductor three-terminal element to cause the light emitting diode to emit light in a quasi-lit state. and are provided to control the driving semiconductor three-terminal element so that the light emitting diode can display a re-emission state of a lighting state and a semi-lighting state.

[Industrial application field]

The present invention relates to a display test circuit that uses light emitting diodes to indicate a fault that has occurred.

In a monitoring system that monitors data transmission paths, a master station,
The operation status and failure status of slave station equipment are constantly monitored, and for this purpose, light emitting diodes are widely used to indicate failures. In this case, even during a test of the light emitting diode, it is necessary to detect a fault by displaying it on the LED in order to improve the reliability of the system.

[Conventional technology]

FIG. 4 is a diagram showing a conventional circuit. In FIG. 4, 41 is a light emitting diode (hereinafter referred to as LED).

42 is an LED drive circuit, which includes a failure signal input cover sofa gate G4 and a transistor Tr for driving the LED;
, and a resistor R4□ connected to the base of the drive transistor Tr, , and a resistor R connected to the collector of the transistor Tr, .
It consists of 43. Here, R4z is selected to be a sufficiently small resistance so that a base current sufficient to drive the transistor Tr41 flows, and the resistor R42 is selected to a value that turns on the LED 41 when current flows to the collector of the transistor Tra+. .

Note that 43 is a test signal generation circuit, S41 is a switch for LED testing, R41 is a resistor for adjusting the brightness of LED 41, and D41 is a diode for protection against reverse current when a plurality of LEDs are connected in parallel. The resistor R41 is selected so that there is a clear difference in luminous intensity between the luminous intensity of the LED 41 during the test and the luminous intensity when the LED 41 is turned on at the time of a failure.

The test signal generation circuit 43 is a Susochi S4 with one end grounded.
1, the resistor R41, and the cathode of the diode D41 are connected in series, and the anode of the diode D41 is connected to the LED4.
The cathode of the LED 41 is connected to the cathode of the LED 41, and a positive DC voltage (+V) is supplied to the anode of the LED 41. Then, a resistor R is connected in parallel at the output end of the test signal generation circuit 43 (the connection point between the anode of D41 and the cathode of LED 41).
Connect the collector of the transistor Tr through 4,
Further, the emitter of the transistor 'rra+ is connected to ground, and the transistor Tr4. An LED drive circuit 42 to which a fault signal is input is connected to the base of the LED drive circuit 42 via an input buffer gate 041 and a resistor R4t. Note that when testing multiple light emitting diodes connected in parallel, the test switch S41 of the LED41 is used as a common circuit, and the resistor R
41, a diode D41, and an LED drive circuit 42 are separately provided and connected in parallel to the output terminal of the switch Sa+.

In the circuit connected in this way, when the LED test switch 341 is closed, the LED test current I41 flows through the diode Oat with the resistor R1 to the LED41, causing the LED41 to emit light and become semi-lit. . Next, the fault signal is input manually to turn on the input cover sofa gate G41 and cause the base current to flow through the transistor Tr41.Therefore, the transistor Tr41 is turned on and causes the LED41 to emit light so that the collector current t4g flows.
A current of 141+14g is applied to , at this time Ia+ and ■4
Between □, 141<14! The resistor R41 is adjusted so as to maintain the following relationship.

By setting the current of the LED 41 in this way, L
When testing the ED41, the LED41 is turned on with a current of 141 to create a "semi-lit state."Furthermore, when a fault signal is applied in a weighted manner, the LED41 has a current of 141+I4.
! A current equal to the sum of both currents flows, but both currents have 141<
[Because of the relationship 4□, the light is turned on with a sufficiently brighter luminous intensity than the luminous intensity at the time of the test of L E 041, creating a "lighting state".

That is, a circuit configuration is adopted in which a test signal generation circuit 43 is provided in parallel with the output end of an LED drive circuit 42 that drives the LED 41, and the lighting intensity is determined when a failure occurs in the LED 41.

The lighting current of the LED 41 is set so that a clear difference in luminous intensity occurs between the actual lighting intensity and the standard lighting intensity during the test.

[Problem to be solved by the invention]

Therefore, when testing a light emitting diode using the above circuit, a problem arises in that the light emitting diode drive circuit is not tested.

SUMMARY OF THE INVENTION An object of the present invention is to provide a light emitting diode test circuit that can simultaneously test a light emitting diode and a light emitting diode drive circuit when testing a light emitting diode.

[Means to solve the problem]

In the present invention, as shown in FIG. 1, a light-emitting diode 1 and a driving semiconductor three-terminal element 2 for lighting the light-emitting diode 1 are connected in series, one end of the series-connected circuit is connected to a DC voltage, and the other end is connected to a DC voltage. When a fault occurs in a circuit whose one end is connected to ground, a signal corresponding to the fault is added to the base of the driving semiconductor three-terminal element 2, and a fault signal is output to turn on the light emitting diode 1 and emit light. A test signal is generated by turning on and off a means 3 and a switch 5 to which a DC voltage is applied to one end, and the test signal is applied to the base of the semiconductor three-terminal element 2 to cause the light emitting diode 1 to emit light in a quasi-on state. A test signal generating means 4 is provided to control the driving semiconductor three-terminal element 2, so that the light emitting diode 1 can display both a light-emitting state and a semi-lighting state.

[For production]

In the present invention, as shown in FIG. 1, when a fault occurs, the fault signal from the fault signal output means 3 is added to the base of the driving semiconductor three-terminal element 2 for control, and when testing the light emitting diode 1, A test signal is generated from the test signal output means 4 by turning on and off the switch 5, and the test signal is applied to the base of the driving semiconductor three-terminal element 2 for control.

Therefore, by controlling the driving semiconductor three-terminal element 2,
The light emitting diode 1 can be displayed in both light-emitting states, such as a lit state and a semi-lit state.

〔Example〕

FIG. 2 is a diagram showing a circuit according to an embodiment of the present invention. In the figure, 21 is a light emitting diode (hereinafter referred to as LED). Reference numeral 22 designates a driving semiconductor three-terminal element and an LED driving circuit as a fault signal output means, such as transistors Tr, which are semiconductor three-terminal elements.
The base driving resistance R2 of the transistor Tr,
, the resistor R2□ connected to the collector of , the gate 9□ for the interference signal input cover sofa, and the diode D! for preventing reverse current. It consists of I. Here, the resistance R1I and the resistance R0 are
Similar to the conventional example shown in FIG. 4, the resistor R11 is selected to be sufficiently small so that a base current sufficient to drive the transistor 'rrx+ flows when a fault signal is input, and the resistor R0 is selected to be a sufficiently small resistance so that a base current sufficient to drive the transistor 'rrx+ flows when a fault signal is input. r
The current flowing through the collector of t+ is selected so that the LED 21 emits light.

23 is a switch S2, a diode D0, and a resistor R1.
The test signal generation circuit consists of 3, where SZ+ is a switch for LED testing, R13 is a resistor for adjusting the brightness of LED21, and D is a diode for reverse current prevention protection that allows parallel testing of multiple LEDs. be. The resistance R here
Similarly to Fig. 4, 0 is selected at a value such that there is a clear difference in luminous intensity between the luminous intensity during the test of the LED 21 and the luminous intensity when the fault signal is input and the LED 21 is completely lit ( .

The test signal generation circuit 23 has a configuration in which a switch SKI whose one end is connected to a DC voltage, a cathode of a diode D0, and a resistor R0 are connected in series, and the output end of the resistor R0 is connected to the LED drive circuit 22.

Note that one end of the LED drive circuit 22 is connected to the cathode of the LED 21 to which a +E polarity DC voltage (+V) is applied to the anode. And the cathode of the LED 21 is
Transistor T'r! via resistor R1z. +, and also connected to the collector of the transistor Tr.

The emitter of the transistor Tr is connected to ground, and the emitter of the transistor Tr is connected to ground.
The base of □ has a gate Gz□ for the cover sofa that receives the fault signal.
Diode D! The circuit configuration is such that a fault signal is input via I and resistor Rt. Note that the output of the test signal generation circuit 23 is connected to the connection point between the diode Dzl and the resistor R1I. When testing multiple LEDs 21 connected in parallel, use the test switch S! l as a shared circuit, resistor R0 and diode D! ! The LED drive circuit 22 is separately provided and connected in parallel to the output terminal of the switch sg+.

In the circuit connected in this way, when the LED test switch SZ+ is closed, the DC voltage V! is diode D! !
, outputs the LED test signal to the LED drive circuit 22 through the resistor R0, drives Rll, and causes the current g+ of the LED test current corresponding to the "quasi-on state" of the LED 21 to flow through the transistor Tr, . Then, a fault signal is input, and the transistor Tr passes through the input buffer gate G□, the diode Do11, and the resistor R2.
, , and the LED test switch S
When Z+ is open, the transistors Tr,, are turned on, causing a collector current 121 to flow, causing the LED 21 to emit light, and causing a current zt to flow through the LED 21. And this r
Between z+ and It□, the ratio of Rzz/Rt+ is set to a sufficiently large value (
For example, by setting it to about 30 to 200 times), the LED
When testing No. 21, LED 21 was turned on with a current of ■z+.

Create a semi-lit state. Furthermore, when a fault signal is applied in a weighted manner, a current equal to the sum of the two currents I□+Izt flows through LEDJI, but since there is a relationship between both currents It+<121, the luminous intensity is compared to the luminous intensity at the time of the test of LED21. to create a ``lit state'' with sufficient brightness.

That is, a transistor Tr that drives the LED 21.

In parallel to the base of the LED from the test signal generation circuit 23
The test signal and the fault signal that passed through the input buffer gate Gffi diode I)z+ are added, and both signals create a magnitude relationship in the current flowing to the collector of the transistor T'rz+, and when a fault occurs in LED2i, The lighting current of the LED 21 is set so that a difference in luminous intensity is generated between the lighting intensity and the standard lighting intensity during the test.

FIG. 3 is a diagram showing another embodiment of the present invention. In FIG. 3, 31 is a lamp, 32 is a lamp drive circuit, and Darlington-connected transistors Tr3. and T'r3x, the resistance R of the base drive of Trot
It consists of a resistor R3□ connected to the collector of Tr1, , and a diode D□ for preventing reverse current, which covers the input of fault signals. is LE in Figure 2 above.
It operates in the same way as the D drive circuit 22. Further, the test signal generation circuit 33 includes a switch S31 and a diode D. , resistance R
3! The test signal generation circuit 23 operates in the same manner as the test signal generation circuit 23 shown in FIG. Note that this circuit includes the Darlington-connected transistors Tr, . . . , and Tr3. This makes it possible to drive the lamp 31 with a large current.

〔Effect of the invention〕

As described above, according to the present invention, when testing a light emitting diode, the main circuits of the light emitting diode and the light emitting diode drive circuit can be tested simultaneously.

Therefore, it is possible to contribute to improving the reliability of the data transfer monitoring and display system.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the principle configuration of the present invention, Fig. 2 is a diagram showing a circuit of one embodiment of the invention, Fig. 3 is a diagram showing a circuit of another embodiment of the invention, and Fig. 4 is a diagram showing a circuit of another embodiment of the invention. The figure which shows the circuit of a conventional example, is shown. In the figure, 1 is a light emitting diode, 2 is a driving semiconductor three-terminal element, 3 is a fault signal output means, and 4 is a test signal generation means. The principle of shame g11 a 9 tat f41 diagram incomplete θ, jfs-p weight example 4 circuits tree f ■ Figure 2 Figure Figure

Claims (1)

[Claims] A light-emitting diode (1) and a driving semiconductor three-terminal element (2) for lighting the light-emitting diode (1) are connected in series, one end of the series-connected circuit is set to a DC voltage, and the other end is connected to a DC voltage. When a fault occurs in a circuit whose one end is connected to ground, a signal corresponding to the fault is applied to the base of the driving semiconductor three-terminal element (2), and the light emitting diode (1) is turned on. A test signal is generated by turning on and off a fault signal output means (3) that emits light and a switch (5) to which a DC voltage is applied to one end, and the test signal is applied to the base of the semiconductor three-terminal element (2). a test signal generating means (4) for causing the light emitting diode (1) to emit light in a quasi-on state, and controlling the driving semiconductor three-terminal element (2);
A light intensity variable test circuit for a light emitting diode, characterized in that the light emitting diode (1) is capable of displaying both light emitting states of a lit state and a quasi-lit state.