JP3649658B2 - LED display device and inspection method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an LED (Light Emitting Diode) display device and an inspection method thereof, and more particularly to a dot matrix type LED display device in which LEDs are arranged in a matrix and an inspection method thereof.
[0002]
[Prior art]
In general, a dot matrix type LED display device has 256 LEDs arranged in a matrix so as to be 16 dots wide × 16 dots long as one character unit, and is formed of 256 LEDs in one character unit. A display unit is formed by arranging an arbitrary number of the units in a matrix. FIG. 9 shows a configuration of a conventional LED display device configured as described above. The LED display device shown in FIG. 9 is shown only for one character unit in order to briefly explain the configuration and operation thereof.
[0003]
The LED display device of FIG. 9 scans in the vertical direction (longitudinal direction) with the display unit 1 composed of LED1.1, LED1.2,..., LED16.16 arranged in a 16 × 16 matrix. A switching element group 2 composed of N-channel MOS transistors S1, S2,..., S16 for switching the LEDs in the display unit for each row, and NPN transistors D1, D2, for simultaneously switching the LEDs in each row. ..., a switching element group 3 constituted by D16 and a control circuit 5 for controlling the switching element groups 2 and 3.
[0004]
For example, when the control circuit 5 turns on the transistor Sm (where m is a natural number of 1 ≦ m <16) by the control circuit 5, the LED display device having such a configuration is displayed in the m-th row of the display unit 1. The power supply voltage VDD is applied to the anodes of the LEDs m. At this time, when data is given to the switching element group 3 from the control circuit 5 and, for example, the transistor Dn (n is a natural number of 1 ≦ n ≦ 16) of the switching element group 3 is turned ON, the LEDm.n The cathode is grounded through the resistor Rn and the transistor Dn. Therefore, the current flows through LEDm.n and lights up. Thus, a character is displayed when the LED provided in the display unit 1 performs a lighting operation. At this time, the LEDs in the row connected to the transistors that are OFF in the switching element group 2 are not lit.
[0005]
[Problems to be solved by the invention]
However, depending on the connection state of the wiring between the display unit 1 and the switch element group 2, the current flowing in the wiring between the transistor of the switching element group 2 turned on by the control circuit 5 and the display unit 1 and other Due to the influence of the operation of the circuit, an induced voltage may be generated in the wiring between the display element 1 and another transistor turned off in the switching element group 2. Therefore, since the transistors in the switching element group 2 are OFF, a very small amount of current generated by the influence of the induced voltage flows in the row of the display unit 1 connected to the transistors, where the current does not flow. The LED whose cathode is grounded by the group 3 is slightly lit.
[0006]
In recent years, such LED display devices may use InGaN-based high-luminance blue, green, and white light emitting LEDs. This InGaN-based LED has a withstand capability of about 200 V at C = 200 pF, whereas it has only a withstand capability of about 50 V, so that it has a low resistance to surges due to static electricity due to its structural factors. . Therefore, depending on the handling of the manufacturing process, static electricity may be applied to the LED, which may cause damage to the LED element and a decrease in reliability. Is a cause of malfunctions that do not light up in a short period of time.
[0007]
Furthermore, in order to avoid this problem, as a method of determining a damaged LED, there is a method of detecting a change in characteristics in which the leakage current in the LED increases when a reverse voltage is applied. In order to perform such an inspection, a probe is applied to each LED and a reverse current is measured. Therefore, the measurement takes time and a measuring instrument including a probe is newly required.
[0008]
In view of such a problem, an object of the present invention is to provide an LED display device capable of preventing an abnormal operation due to an induced voltage generated in a wiring. Another object of the present invention is to provide an LED display device and an inspection method thereof that can easily detect an LED having a reverse characteristic abnormality.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, an LED display device of the present invention applies a first voltage to a display unit composed of a plurality of LEDs arranged in a matrix and to the first terminal of each LED for each row. A plurality of first switching elements, a plurality of second switching elements for applying a second voltage to the second terminal of the LED for each column, and ON / OFF of the first switching element and the second switching element. An LED display device in which an LED determined by turning on the first switching element and the second switching element among the plurality of LEDs is turned on. Provided for each switching element and connected between the first switching element and the display unit For wiring A plurality of impedance elements having one end connected and the second voltage applied to the other end And the impedance element comprises a series circuit of a resistor and a Zener diode. It is characterized by that.
[0010]
In such an LED display device, by making the impedance of the impedance element lower than the impedance of the LED constituting the display unit, the current flowing in another circuit or the wiring in the wiring between the display unit and the first switching element, etc. When a dielectric voltage is generated under the influence of the above, a current generated by the dielectric voltage flows through the impedance element. Therefore, it is possible to prevent the LED connected to the first switching element that is turned off from being lit by the current generated by the dielectric voltage.
[0011]
In such an LED display device, The first switching element may be a MOS transistor, and the second switching element may be a junction transistor. Further, a plurality of third switching elements provided for each of the first switching elements and connected in series with the impedance element may be provided.
[0012]
Further, in the present invention, as an inspection method for such an LED display device, all the second switching elements are turned off, and the first switching elements are time-division driven and sequentially turned on, so that they are reversed. Provided is an inspection method for an LED display device, characterized by detecting an LED having a reverse characteristic abnormality in which a leak current flows.
[0013]
In such an inspection method, when there is an LED having an abnormal reverse characteristic among the LEDs arranged in the same row, when the first switching element other than the first switching element connected to the LED is turned ON, Since the second voltage is applied to the second terminal of the LED via the reverse characteristic abnormal LED and the impedance element, all LEDs in the same row other than the reverse characteristic abnormal LED are lit. Therefore, when this occurs, when there are LEDs that are lit in the LEDs in the same row, the LEDs that are not lit are detected as LEDs having reverse characteristic abnormalities. If all the LEDs in the same row are not lit, the LEDs arranged in that row are assumed to operate normally.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, each embodiment of the present invention will be described.
[0015]
<First Embodiment>
A first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block circuit diagram showing the internal configuration of the LED display device according to this embodiment. Note that the LED display device shown in FIG. 1 is shown only for one character unit in order to briefly explain the configuration and operation of the LED display device shown in FIG.
[0016]
The LED display device of FIG. 1 includes a display unit 1 in which 256 LEDs LED1.1 to LED16.16 are arranged in a matrix, and N-channel MOS transistors S1 to S16, and the display unit 1 is arranged vertically. A switching element group 2 that scans in the direction and controls switching of the LEDs for each row; a switching element group 3 that includes NPN transistors D1 to D16 and simultaneously controls switching of the LEDs in each row of the display unit 1; Impedance element group 4 composed of loads Z1 to Z16 having one end connected to each source of transistors S1 to S16 of group 2 and the other end grounded, and control circuit 5 for controlling switching element groups 2 and 3 And have.
[0017]
At this time, the power supply voltage VDD is applied to the drains of the transistors S1 to S16, and a control signal is supplied from the control circuit 5 to each gate. The emitters of the transistors D1 to D16 are grounded, the respective collectors are connected to one ends of the resistors R1 to R16, and control signals are given to the respective bases from the control circuit 5. Furthermore, the anodes of LED1.1 to LED1.16, LED2.1 to LED2.16,..., LED16.1 to LED16.16 are connected to the sources of the transistors S1, S2,. The cathodes of LED1.1 to LED16.1, LED1.2 to LED16.2,..., LED1.16 to LED16.16 are connected to the other ends of R1, R2,.
[0018]
As in the LED display device shown in FIG. 9, when the transistor Sm is turned on by the control circuit 5, the LED display device configured in this way has LED m.1 to LEDm.16 in the m-th row of the display unit 1. The power supply voltage VDD is applied to the anode, and current flows. At this time, for example, when the transistor Dn is turned on by the control circuit 5, the cathode of LEDm.n existing in the nth column of the display unit 1 is grounded via the resistor Rn and the transistor Dn. .n lights when current flows.
[0019]
Thus, when the LED in the m-th row lights up, an induced voltage is generated in the wiring between the LEDs other than the m-th row and the switching element group 2, and a weak current is generated in the wiring in which the induced voltage is generated. Tries to flow. Now, the loads Z1 to Z16 of the impedance element group 4 are set sufficiently lower than the impedance due to the LEDs of the display unit 1 and the resistors R1 to Rn. That is, the impedance of the load Z1 is set to be sufficiently lower than the impedance due to the LEDs 1.1 to LED 1.16 and the resistors R1 to R16.
[0020]
Therefore, the weak current flowing through the wiring in which the induced voltage is generated flows through the load of the impedance element group 4, so that it can be prevented from flowing into the display unit 1. That is, when an induced voltage is generated in the wiring between the first row of the display unit 1 and the transistor S1 when the transistor S1 is OFF, a weak current due to the induced voltage flows through the load Z1, so that the display unit It is possible to prevent the LED 1 to LED 1.16 from being turned on.
[0021]
Further, a method for detecting an LED having an abnormal reverse characteristic damaged by static electricity or the like in such an LED display device will be described below. When performing the inspection method for detecting the LED having the reverse characteristic abnormality, first, all the transistors D1 to D16 constituting the switching element group 3 are turned off. Then, the switching elements 2 are driven in a time-sharing manner by turning on the transistors S1, S2,. At this time, since all of the transistors D1 to D16 are OFF, if all the LEDs constituting the display unit 1 operate normally, the transistors S1 to S16 constituting the switching element group 2 are turned on even when turned on. There is nothing to do.
[0022]
However, when there is an LED having an abnormal reverse characteristic, the cathodes of the other 15 LEDs arranged in the row where the LED having the abnormal reverse characteristic exists are the LED having the abnormal reverse characteristic and the anode of this LED. It will be in the state grounded through the load connected to. Therefore, when the transistors in the switching element group 2 connected to the anodes of the other 15 LEDs are turned on, a current flows through each of the LEDs and lights up.
[0023]
That is, for example, in the display unit 1, if only the LED 1.1 is an LED having an abnormal reverse characteristic, first, when only the transistor S1 of the switching element group 2 is turned ON, a current flows through the LED 1.1. Does not light because there is no. Next, the transistor S1 is turned off and only the transistor S2 is turned on. A circuit model focusing on the LED 1.1 at this time is shown in FIG. Since a reverse leakage current flows through LED 1.1, a leakage current flows through LED 1.1 via load Z1. Thus, the cathode of LED 2.1 is grounded via LED 1.1 and load Z1, and its anode is supplied with power supply voltage VDD via transistor S2, so that current flows through LED 2.1. Light.
[0024]
Similarly, when the transistors S3, S4,..., S16 in the switching element group 2 are sequentially turned on, the cathodes of LED3.1, LED4.1, ... LED16.1 are grounded via LED1.1 and load Z1, respectively. It becomes a state. Therefore, by sequentially turning on the transistors S3, S4,..., S16 in the switching element group 2, a current flows sequentially through the LEDs 3.1, LED4.1,. Therefore, among the LEDs 1.1 to 16.1 arranged in the same column, all the LEDs except the LED 1.1 are turned on. Therefore, it is possible to detect the LED 1.1 that is not lit as an LED having an abnormal reverse characteristic.
[0025]
In this way, when there are LEDs that are lit on the same column, it is possible to detect a non-lit LED on this column as an LED having an abnormal reverse characteristic. Further, when the switching element group 2 is driven in a time-sharing manner as in this inspection method, if all the LEDs constituting the display unit 1 are not lit, it can be assumed that all the LEDs are normal. As described above, the switching element group 3 is turned off and the switching element group 2 is driven in a time-sharing manner, whereby it is possible to easily detect the LED having the reverse direction characteristic abnormality in the display unit 1.
[0026]
<Second Embodiment>
A second embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a block circuit diagram showing an internal configuration of the LED display device according to the present embodiment. Note that the LED display device shown in FIG. 3 is shown only for one character unit in order to briefly describe the configuration and operation thereof, similarly to the LED display device shown in FIG. Also, in FIG. 3, parts used for the same purpose as in FIG.
[0027]
The LED display device shown in FIG. 3 uses resistors r <b> 1 to r <b> 16 for the impedance element group 4. That is, the other ends of the resistors r1, r2,..., R16 having one end grounded are connected to the sources of the transistors S1, S2,. About another structure, it is the structure similar to the LED display apparatus of 1st Embodiment (FIG. 1).
[0028]
In this configuration, by reducing the resistance values of the resistors r1 to r16, the induced voltage generated in the wiring between the transistor in the switching element group 2 turned off by the control circuit 5 and the display unit 1 Current flowing in the impedance element group 4 side can prevent the LEDs in the row not scanned by the switching element group 2 from being lit. As described above, in order to turn off the LEDs in the row that is not scanned, the effect appears by setting the LED display device to about 10 kΩ or less, although it depends on the state of the wiring in the LED display device.
[0029]
However, since the power consumed in the impedance element group 4 is inversely proportional to the resistance values of the resistors r1 to r16, the power consumption in the impedance element group 4 increases as the resistance values of the resistors r1 to r16 are decreased. Further, if this power consumption increases, it is necessary to make the resistors r1 to r16 constituting the impedance element group 4 have large rated power, which is not desirable. Therefore, the resistance values of the resistors r1 to r16 are usually set so that the power consumed by each of the resistors r1 to r16 is 1 W or less, preferably 0.01 W or less. Therefore, when the power supply voltage VDD applied to the LED display device is 5 V, the resistance values of the resistors r1 to r16 are preferably 2.5 kΩ or more and 10 kΩ or less.
[0030]
By configuring the impedance element group 4 with the resistors r1 to r16 in this way, the LED element which works effectively when a DC induced voltage is generated in the wiring between the display unit 1 and the switching element group 2 and does not light up originally. Lighting can be prevented.
[0031]
<Third Embodiment>
A third embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a block circuit diagram showing an internal configuration of the LED display device according to the present embodiment. Note that the LED display device shown in FIG. 4 is shown only for one character unit in order to briefly explain the configuration and operation, similarly to the LED display device shown in FIG. 4, parts used for the same purpose as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.
[0032]
The LED display device shown in FIG. 4 uses capacitors C <b> 1 to C <b> 16 for the impedance element group 4. That is, the other ends of the capacitors C1, C2,..., C16 having one end grounded are connected to the sources of the transistors S1, S2,. About another structure, it is the structure similar to the LED display apparatus of 1st Embodiment (FIG. 1).
[0033]
With this configuration, the capacitor functions as an impedance element having a low impedance with respect to a high-frequency voltage. Therefore, when the induced voltage generated in the wiring between the display unit 1 and the switching element group 2 is pulsed. A current generated by the induced voltage flows through the impedance element group 4 of the capacitors C1 to C16. By configuring the impedance element group 4 with the capacitors C1 to C16 in this way, the LED element that works effectively when a high-frequency induced voltage is generated in the wiring between the display unit 1 and the switching element group 2 and does not light up originally. Lighting can be prevented.
[0034]
<Fourth Embodiment>
A fourth embodiment of the present invention will be described with reference to the drawings. FIG. 5 is a block circuit diagram showing the internal configuration of the LED display device according to the present embodiment. Note that the LED display device shown in FIG. 5 is shown only for one character unit in order to briefly explain the configuration and operation thereof, like the LED display device shown in FIG. Further, in FIG. 5, parts used for the same purpose as in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.
[0035]
The LED display device shown in FIG. 5 uses a parallel circuit of resistors r1 to r16 and capacitors C1 to C16 for the impedance element group 4. That is, the other ends of the resistors r1, r2,..., R16 having one end grounded and the other ends of the capacitors C1, C2,. And are connected. About another structure, it is the structure similar to the LED display apparatus of 1st Embodiment (FIG. 1).
[0036]
In such a configuration, the resistor acts as a low impedance impedance element with respect to a DC voltage and the capacitor acts as a low impedance voltage with respect to a high frequency voltage. Therefore, when the induced voltage generated in the wiring between the display unit 1 and the switching element group 2 is a DC voltage, the current generated by the induced voltage flows to the impedance element group 4 of the resistors r1 to r16. In addition, when the induced voltage generated in the wiring between the display unit 1 and the switching element group 2 is in a pulse shape, the current generated by the induced voltage flows to the capacitors C1 to C16.
[0037]
As described above, the impedance element group 4 is configured by the parallel circuit of the resistors r1 to r16 and the capacitors C1 to C16, and thus works effectively when an induced voltage is generated in the wiring between the display unit 1 and the switching element group 2. Therefore, it is possible to prevent the lighting of the LED that is not originally lit.
[0038]
<Fifth Embodiment>
A fifth embodiment of the present invention will be described with reference to the drawings. FIG. 6 is a block circuit diagram showing an internal configuration of the LED display device according to the present embodiment. Note that the LED display device shown in FIG. 6 is shown only for one character unit in order to briefly explain the configuration and operation of the LED display device shown in FIG. Also, in FIG. 6, the parts used for the same purpose as in FIG.
[0039]
The LED display device shown in FIG. 6 uses a series circuit of resistors r1 to r16 and Zener diodes Z1 to Z16 for the impedance element group 4. That is, one end of resistors r1, r2,..., R16 is connected to the sources of transistors S1, S2,..., S16, and the other end of resistors r1, r2,. The cathodes of the diodes Z1, Z2,..., Z16 are connected. About another structure, it is the structure similar to the LED display apparatus of 1st Embodiment (FIG. 1).
[0040]
With this configuration, since the voltage applied to the Zener diodes Z1 to Z16 is constant, when there is an LED having an abnormal reverse characteristic in the display unit 1, the cathode of the LED arranged in the same row as this LED Is prevented from being grounded via a load in the impedance element group 4 connected to the LED having the reverse characteristic abnormality. That is, if the voltage for operating the Zener diodes Z1 to Z16 is Va, a higher voltage than the voltage Va is applied to the cathode of the LED arranged in the same row as the LED having the abnormal reverse characteristic. Therefore, at this time, a voltage lower than VDD-Va is applied to the LED. By making this voltage VDD-Va lower than the operating voltage of the LED, it is possible to prevent a normal LED from malfunctioning.
[0041]
Now, for example, the operation of the display unit 1 when only the LED 1.1 is an LED having an abnormal reverse characteristic will be described. A circuit model focusing on the LED 1.1 at this time is shown in FIG. Assume that the transistor S2 in the switching element group 2 is ON and the transistor D1 in the switching element group 3 is OFF. At this time, when the LED 2.1 operates normally, the LED 2.1 is not lit. However, as in the second embodiment (FIG. 3), when the impedance element group 4 is composed of only resistors, the power supply voltage VDD is applied to the anode of the LED 2.1 via the transistor S2, and the LED 2 Since the cathode of .1 is grounded via the LED 1.1 and the resistor r1, a current flows through the LED 2.1 and it is lit.
[0042]
Therefore, as in this embodiment, by providing a Zener diode in the impedance element group 4 through which current flows when a reverse voltage of Va is applied, the LED 2.1 is connected to the cathode via the LED 1.1 and the resistor r1. The voltage Va is applied. By setting the voltage Va to such a voltage that the LED in the display unit 1 is not driven by VDD-Va, it is possible to prevent the current from flowing through the LED 2.1 and to turn off the LED. That is, assuming that the drive voltage of the LED is Vb, Vb> VDD−Va, and therefore, VDD−Vb is applied to the Zener diode Z1.
[0043]
Therefore, a voltage lower than Va is applied to the Zener diode Z1, and no current flows through the Zener diode Z1, so that the LED 2.1 is not driven. As described above, according to the LED display device of the present embodiment, even if there is an LED having an abnormal reverse characteristic in the display unit 1, other normal LEDs can be operated normally without being affected by them.
[0044]
<Sixth Embodiment>
A sixth embodiment of the present invention will be described with reference to the drawings. FIG. 8 is a block circuit diagram showing the internal configuration of the LED display device according to this embodiment. Note that the LED display device shown in FIG. 8 is shown only for one character unit in order to briefly explain the configuration and operation, similarly to the LED display device shown in FIG. Further, in FIG. 8, parts used for the same purpose as in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.
[0045]
The LED display device shown in FIG. 8 has a configuration in which a switching element group 6 connected to the impedance element group 4 is further provided. That is, N-channel MOS transistors T1, T1, and D16 are connected to the other ends of loads Z1, Z2,..., Z16 having one ends connected to the sources of the transistors S1, S2,. T2, ..., T16 are provided. The transistors T1 to T16 are also ON / OFF controlled by a signal supplied to the gate from the control circuit 5. Other configurations are the same as those of the LED display device of the first embodiment (FIG. 1).
[0046]
In the LED display device configured as described above, the switching element group 6 performs the ON / OFF operation in synchronization with the ON / OFF operation of the switching element group 2. However, the transistors in the switching element group 6 connected to the same row as the transistors that are turned on in the switching element group 2 are turned off, and the 15 transistors in the other switching element group 6 are turned on.
[0047]
That is, when the transistor S1 is turned on and the transistors S2 to S16 are turned off to turn on the LEDs in the first row in the display unit 1, the transistor T1 is turned off in the switching element group 6. At the same time, the transistors T2 to T16 are turned on. Similarly, when the LEDs in the second and subsequent rows in the display unit 1 are lit, in the switching element group 6, the transistors connected to the wiring of the row to be lit are turned off and the other 15 Each transistor is turned on.
[0048]
By operating the switching element groups 2 and 6 in this way, current is applied to the load in the impedance element group 4 connected to the row scanned by the switching element group 2 of the display unit 1 and supplied with data from the switching element group 3. Since it can be prevented from flowing, the power consumption in the impedance element group 4 can be reduced. At this time, for the LEDs in the row that is not lit by the switching element group 2 in the display unit 1, since the transistors in the switching element group 6 are ON, the current generated by the generation of the induced voltage is the impedance element group. Since it flows to the 4 side, lighting can be prevented. As described above, according to the present embodiment, the load in the impedance element group 4 connected to the row to be lit on the display unit 1 can be electrically disconnected, so that useless power consumption can be prevented.
[0049]
In the present embodiment, the impedance element group 4 may be the impedance element group 4 in the second to sixth embodiments.
[0050]
【The invention's effect】
According to the present invention, depending on the state of the wiring between the display unit and the first switching element, the current generated by the induced voltage caused by the influence of other circuit operations flows into the display unit by flowing through the impedance element. Can be prevented. Therefore, when the first switching element is OFF, the current generated by the induced voltage generated in the wiring flows into the display unit, and the LEDs in the row connected to the OFF first switching element are lighted slightly. Can be prevented, and can be operated normally without malfunction. Further, according to the present invention, in order to detect an LED having an abnormal reverse characteristic due to the influence of a surge such as static electricity, it is easily inspected without providing a new measuring instrument as in the prior art. be able to. Therefore, a highly reliable LED display device can be obtained.
[Brief description of the drawings]
FIG. 1 is a block circuit diagram showing an internal configuration of an LED display device according to a first embodiment.
FIG. 2 is a block circuit diagram showing a part of the LED display device for explaining an inspection method of the LED display device.
FIG. 3 is a block circuit diagram showing an internal configuration of an LED display device according to a second embodiment.
FIG. 4 is a block circuit diagram showing an internal configuration of an LED display device according to a third embodiment.
FIG. 5 is a block circuit diagram showing an internal configuration of an LED display device according to a fourth embodiment.
FIG. 6 is a block circuit diagram showing an internal configuration of an LED display device according to a fifth embodiment.
7 is a block circuit diagram showing a part of the LED display device of FIG. 6;
FIG. 8 is a block circuit diagram showing an internal configuration of an LED display device according to a sixth embodiment.
FIG. 9 is a block circuit diagram showing an internal configuration of a conventional LED display device.
[Explanation of symbols]
1 Display section
2,3 Switching element group
4 Impedance element group
5 Control circuit

Claims (6)

A display unit composed of a plurality of LEDs arranged in a matrix, a plurality of first switching elements for applying a first voltage to the first terminals of the LEDs for each row, and a first of the LEDs for each column. A plurality of second switching elements for applying a second voltage to two terminals; a control circuit for controlling ON / OFF of the first switching element and the second switching element; In the LED display device in which the LED determined by turning on the first switching element and the second switching element is turned on,
A plurality of impedance elements provided for each of the first switching elements, one end of which is connected to the wiring connected between the first switching element and the display unit, and the second voltage is applied to the other end. And having
The LED display device, wherein the impedance element comprises a series circuit of a resistor and a Zener diode. The LED display device according to claim 1 , wherein the first switching element is a MOS transistor. LED display device according to claim 1 or claim 2, wherein the second switching element is a junction transistor. 4. The LED display device according to claim 1 , further comprising a plurality of third switching elements provided for each of the first switching elements and connected in series with the impedance element. 5. The LED display device according to claim 4 , wherein the third switching element is a MOS transistor. A display unit composed of a plurality of LEDs arranged in a matrix, a plurality of first switching elements for applying a first voltage to the first terminals of the LEDs for each row, and a first of the LEDs for each column. A plurality of second switching elements for applying a second voltage to two terminals; a control circuit for controlling ON / OFF of the first switching element and the second switching element; In the inspection method of the LED display device in which the LED determined by turning on the first switching element and the second switching element is turned on,
The LED display device includes a plurality of impedance elements, one end of which is connected to a wiring connected between the first switching element and the display unit, and the second voltage is applied to the other end. For each switching element,
All of the second switching elements are turned off, and the first switching elements are time-division driven and sequentially turned on to detect an LED having a reverse characteristic abnormality in which a leak current flows in the reverse direction. Inspection method for LED display device.

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