JPH05283748A - Detecting circuit for failure of discontinuity and short circuit of light-emitting diode - Google Patents
Detecting circuit for failure of discontinuity and short circuit of light-emitting diodeInfo
- Publication number
- JPH05283748A JPH05283748A JP8246492A JP8246492A JPH05283748A JP H05283748 A JPH05283748 A JP H05283748A JP 8246492 A JP8246492 A JP 8246492A JP 8246492 A JP8246492 A JP 8246492A JP H05283748 A JPH05283748 A JP H05283748A
- Authority
- JP
- Japan
- Prior art keywords
- transistor
- emitting diode
- diode
- light emitting
- potential
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Landscapes
- Led Devices (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】この発明は、表示器などに使われ
る発光ダイオードの故障検出回路に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a failure detection circuit for a light emitting diode used in a display or the like.
【０００２】[0002]
【従来の技術】従来、発光ダイオードの故障検出回路
は、図２に示すような構成をしており、接地ライン１と
電源ライン２の間に、発光ダイオード７と２つのトラン
ジスタ５、６と、発光ダイオード７のカソードとトラン
ジスタ５のコレクタの間に抵抗８が接続されて、前記発
光ダイオード７のカソードとトランジスタ６のベースの
間に抵抗９が接続されている。さらにトランジスタ５の
ベースには抵抗１０が接続され、この抵抗の片側が発光
ダイオード７を駆動するための入力端子３となる。抵抗
８は、発光ダイオード７を発光させるために十分な電流
を流すための抵抗値に設定する。抵抗９は発光ダイオー
ド７の光量が、トランジスタ５が遮断状態のとき十分暗
くなり、かつトランジスタ６を導通状態にすることがで
きるような値に設定する。2. Description of the Related Art Conventionally, a failure detection circuit for a light emitting diode has a structure as shown in FIG. 2, in which a light emitting diode 7 and two transistors 5 and 6 are provided between a ground line 1 and a power supply line 2. A resistor 8 is connected between the cathode of the light emitting diode 7 and the collector of the transistor 5, and a resistor 9 is connected between the cathode of the light emitting diode 7 and the base of the transistor 6. Further, a resistor 10 is connected to the base of the transistor 5, and one side of this resistor serves as an input terminal 3 for driving the light emitting diode 7. The resistor 8 is set to a resistance value for allowing a sufficient current to cause the light emitting diode 7 to emit light. The resistor 9 is set to a value such that the light amount of the light emitting diode 7 becomes sufficiently dark when the transistor 5 is in the cutoff state and the transistor 6 can be turned on.
【０００３】発光ダイオード７が正常の時、発光ダイオ
ード７のカソード１１の電位は、（電源ライン２の電
位）−（発光ダイオード７の順方向降下電圧）となり、
トランジスタ６を導通状態にする。発光ダイオード７が
断線した時、発光ダイオード７のカソード１１の電位
は、接地ライン１と同電位となりトランジスタ６は遮断
状態になる。When the light emitting diode 7 is normal, the potential of the cathode 11 of the light emitting diode 7 becomes (potential of the power supply line 2)-(forward drop voltage of the light emitting diode 7),
The transistor 6 is turned on. When the light emitting diode 7 is broken, the potential of the cathode 11 of the light emitting diode 7 becomes the same potential as the ground line 1 and the transistor 6 is cut off.
【０００４】[0004]
【発明が解決しようとする課題】しかし、従来の回路で
は、発光ダイオード７が短絡した時、発光ダイオード７
のカソード１１の電位は、電源ライン２と同電位にな
り、トランジスタ６は導通状態になって、発光ダイオー
ド７が正常の時との区別がつかないため、短絡による故
障が検出できないという課題があった。However, in the conventional circuit, when the light emitting diode 7 is short-circuited, the light emitting diode 7
The potential of the cathode 11 becomes the same as that of the power supply line 2, the transistor 6 becomes conductive, and the light emitting diode 7 is indistinguishable from the normal state. Therefore, there is a problem that a failure due to a short circuit cannot be detected. It was
【０００５】[0005]
【課題を解決するための手段】上記課題を解決するため
に、この発明によれば、発光ダイオードの故障検出回路
において、アノードが電源ラインに接続された発光ダイ
オードと、この発光ダイオードを駆動する第１のトラン
ジスタと、発光ダイオードのカソードにアノードを接続
する第１のダイオードと、このダイオードのカソードと
第２のトランジスタのベースを接続する抵抗と、第２の
トランジスタのエミッタにコレクタを接続し、エミッタ
を接地ラインに接続する第３のトランジスタと、エミッ
タを電源ラインに接続する第４のトランジスタと、この
トランジスタのベースにアノードを接続する第２のダイ
オードと、このダイオードのカソードと第１のダイオー
ドのカソードを接続する抵抗と、第４のトランジスタの
コレクタと第３のトランジスタのベースを接続する抵抗
を含むことによって発光ダイオードの短絡状態の故障検
出が図れるようにした。In order to solve the above problems, according to the present invention, in a failure detection circuit for a light emitting diode, a light emitting diode whose anode is connected to a power supply line and a first light emitting diode driving the light emitting diode are provided. 1 transistor, a first diode connecting the anode to the cathode of the light emitting diode, a resistor connecting the cathode of this diode to the base of the second transistor, and a collector connected to the emitter of the second transistor To the ground line, a fourth transistor to connect the emitter to the power line, a second diode to connect the anode to the base of the transistor, and a cathode of the diode and the first diode. The resistor connecting the cathode, the collector of the fourth transistor and the third And so attained that fault detection of a short-circuit state of the light emitting diode by including a resistor connecting the base of the transistor.
【０００６】[0006]
【作用】上記のように構成された発光ダイオードの故障
検出回路においては、発光ダイオードの断線故障の時、
第２のトランジスタが遮断され、さらに発光ダイオード
の短絡故障の時は第３及び第４のトランジスタが遮断さ
れる。発光ダイオードが正常な時、第２、第３、第４の
トランジスタは全て導通する。このように作動して、出
力端子を第２のトランジスタのコレクタとすれば、出力
端子と接地ライン間の遮断状態を検出することで、発光
ダイオードの断線及び短絡の検出ができることとなる。In the light-emitting diode failure detection circuit configured as described above, when the light-emitting diode has a disconnection failure,
The second transistor is cut off, and in the case of a short-circuit failure of the light emitting diode, the third and fourth transistors are cut off. When the light emitting diode is normal, the second, third and fourth transistors are all conductive. By operating in this way and using the output terminal as the collector of the second transistor, it is possible to detect disconnection and short circuit of the light emitting diode by detecting the cutoff state between the output terminal and the ground line.
【０００７】[0007]
【実施例】以下に、この発明の実施例を図に基づいて説
明する。発光ダイオード７は、そのアノードが電源ライ
ン２に接続され、またそのカソードは、第１の抵抗８を
介して第１のトランジスタ５のコレクタ５ａと接続され
ている。さらに発光ダイオード７のカソード側には、第
１のダイオード１６のアノード側が接続されている。こ
の第１のダイオード１６のカソード側は、第２の抵抗９
を介して第２のトランジスタ６のベースと接続されてい
る。第２のトランジスタ６のエミッタ側は、第３のトラ
ンジスタ１４のコレクタと接続されている。第３のトラ
ンジスタ１４のエミッタは、接地ライン１と接続されて
いる。Embodiments of the present invention will be described below with reference to the drawings. The light emitting diode 7 has its anode connected to the power supply line 2 and its cathode connected to the collector 5 a of the first transistor 5 via the first resistor 8. Further, the cathode side of the light emitting diode 7 is connected to the anode side of the first diode 16. The cathode side of the first diode 16 has a second resistor 9
Is connected to the base of the second transistor 6 via. The emitter side of the second transistor 6 is connected to the collector of the third transistor 14. The emitter of the third transistor 14 is connected to the ground line 1.
【０００８】電源ライン２は、エミッタ側にて第４のト
ランジスタ１５が接続されている。第４のトランジスタ
１５のベース側は、第２のダイオード１７のカソード側
と接続されている。第２のダイオード１７のアノード側
は、第３の抵抗１８を介して、第１のダイオード１６の
アノード側と接続している。第３のトランジスタ１４の
ベースは、第４の抵抗１９を介して第４のトランジスタ
１５のエミッタと接続されている。第１のトランジスタ
５のエミッタ側は接地ライン１に接続されている。The power supply line 2 is connected to the fourth transistor 15 on the emitter side. The base side of the fourth transistor 15 is connected to the cathode side of the second diode 17. The anode side of the second diode 17 is connected to the anode side of the first diode 16 via the third resistor 18. The base of the third transistor 14 is connected to the emitter of the fourth transistor 15 via the fourth resistor 19. The emitter side of the first transistor 5 is connected to the ground line 1.
【０００９】発光ダイオード７が正常なとき、発光ダイ
オード７のカソード端子の点１１の電位は、 （電源ライン２の電位）−（発光ダイオード７の順方向
電圧降下） となる。このとき、第１のダイオード１６のカソード側
端子の点１２の電位は、 （電源ライン２の電位）−（発光ダイオード７の順方向
電圧降下）−（ダイオード１６の順方向電圧降下） となり、この電位は第２の抵抗９を介して第２のトラン
ジスタ６のベースに加えられて第２のトランジスタ６は
順方向にバイアスされて導通状態になる。When the light emitting diode 7 is normal, the potential at the point 11 of the cathode terminal of the light emitting diode 7 becomes (potential of the power supply line 2)-(forward voltage drop of the light emitting diode 7). At this time, the potential of the point 12 on the cathode side terminal of the first diode 16 becomes (potential of the power supply line 2)-(forward voltage drop of the light emitting diode 7)-(forward voltage drop of the diode 16). The potential is applied to the base of the second transistor 6 via the second resistor 9, and the second transistor 6 is forward biased and becomes conductive.
【００１０】さらに、第４のトランジスタ１５のエミッ
タの電位は電源ライン２の電位であり、この第４のトラ
ンジスタ１５のベースの電位は、 （１２の点の電位）＋（ダイオード１７の順方向電圧降
下） となって、第４のトランジスタ１５のエミッタ・ベース
間は順方向にバイアスされ、第４のトランジスタ１５は
導通状態となって、この第４のトランジスタ１５のコレ
クタから第４の抵抗１９を介して第３のトランジスタ１
４を導通させる。発光ダイオード７が正常なときは、前
述のように第２のトランジスタ６と、第３のトランジス
タ１４が導通状態になって、第２のトランジスタ６のコ
レクタである出力４は接地ライン１と導通する。Further, the potential of the emitter of the fourth transistor 15 is the potential of the power supply line 2, and the potential of the base of the fourth transistor 15 is (potential at point 12) + (forward voltage of the diode 17). Then, the emitter-base of the fourth transistor 15 is forward biased, the fourth transistor 15 becomes conductive, and the fourth resistor 19 is connected to the fourth resistor 19 from the collector of the fourth transistor 15. Through the third transistor 1
Conduct 4 When the light emitting diode 7 is normal, as described above, the second transistor 6 and the third transistor 14 become conductive, and the output 4 which is the collector of the second transistor 6 becomes conductive to the ground line 1. ..
【００１１】次に、発光ダイオード７が断線したときの
動作を図１によって説明する。発光ダイオードが断線す
ると、点１１の電位が前述の電位を保つことができない
ため、第２のトランジスタ６は遮断状態となって、出力
４は接地ライン１と遮断される。次に、発光ダイオード
が断線したときの動作を図１によって説明する。発光ダ
イオード７が短絡すると、点１１の電位は電源ライン２
の電位と等しくなるので、点１２の電位は、 （電源ライン２の電位）−（ダイオード１６の順方向電
圧降下） となる。この時、第１のダイオード１６と第２のダイオ
ード１７の順方向電圧降下が等しいとすれば、第４のト
ランジスタ１５のベース電位は電源ライン２の電位と等
しくなって、第４のトランジスタ１５は遮断され、第３
のトランジスタ１４も遮断状態になる。この状態では出
力４は接地ラインと遮断状態になる。Next, the operation when the light emitting diode 7 is broken will be described with reference to FIG. When the light emitting diode is broken, the potential at the point 11 cannot maintain the above-mentioned potential, so that the second transistor 6 is cut off and the output 4 is cut off from the ground line 1. Next, the operation when the light emitting diode is broken will be described with reference to FIG. When the light emitting diode 7 is short-circuited, the potential at the point 11 becomes the power line 2
Therefore, the potential at the point 12 becomes (potential of the power supply line 2)-(forward voltage drop of the diode 16). At this time, if the forward voltage drops of the first diode 16 and the second diode 17 are equal, the base potential of the fourth transistor 15 becomes equal to the potential of the power supply line 2, and the fourth transistor 15 becomes Shut off, third
The transistor 14 of is also turned off. In this state, the output 4 is cut off from the ground line.
【００１２】このような動作を行わせ、出力４が接地ラ
インと遮断された状態を発光ダイオードが異常とし、出
力４が接地ラインと導通した状態を発光ダイオードが正
常とするように構成した例である。In an example in which the above operation is performed, the light emitting diode is abnormal when the output 4 is disconnected from the ground line, and the light emitting diode is normal when the output 4 is electrically connected to the ground line. is there.
【００１３】[0013]
【発明の効果】この発明は、以上説明したように発光ダ
イオードの短絡による故障と発光ダイオードの断線によ
る故障を、発光ダイオードの駆動信号の有無にかかわら
ずに検出することを可能にする、という構成としたの
で、発光ダイオードを表示器として使用する機器の保守
性の向上をはかる効果がある。As described above, the present invention makes it possible to detect a failure due to a short circuit of a light emitting diode and a failure due to a disconnection of the light emitting diode regardless of the presence or absence of a drive signal for the light emitting diode. Therefore, there is an effect of improving the maintainability of the device using the light emitting diode as a display.
【図１】本発明の一実施例による発光ダイオードの故障
検出回路を示した回路図である。FIG. 1 is a circuit diagram illustrating a failure detection circuit for a light emitting diode according to an exemplary embodiment of the present invention.
【図２】従来の方法の回路図である。FIG. 2 is a circuit diagram of a conventional method.
１ 接地ライン ２ 電源ライン ３ 発光ダイオード駆動信号入力 ４ 故障検出信号出力 ５ 第１のトランジスタ ６ 第２のトランジスタ ７ 発光ダイオード ８ 第１の抵抗 ９ 第２の抵抗 １４ 第３のトランジスタ １５ 第４のトランジスタ １６ 第１のダイオード １７ 第２のダイオード １８ 第３の抵抗 １９ 第４の抵抗 1 Ground Line 2 Power Line 3 Light Emitting Diode Drive Signal Input 4 Failure Detection Signal Output 5 First Transistor 6 Second Transistor 7 Light Emitting Diode 8 First Resistor 9 Second Resistor 14 Third Transistor 15 Fourth Transistor 16 1st diode 17 2nd diode 18 3rd resistance 19 4th resistance
Claims (1)
ダイオードと、この発光ダイオードを駆動するための第
１のトランジスタと、前記発光ダイオードのカソードと
第１のトランジスタのコレクタとを接続する第１の抵抗
と、前記発光ダイオードのカソードにアノードを接続し
た第１のダイオードと、このダイオードのカソードと第
２のトランジスタのベースを接続する第２の抵抗と、前
記第２のトランジスタのエミッタにコレクタを接続して
エミッタを接地ラインに接続した第３のトランジスタ
と、エミッタが電源ラインに接続された第４のトランジ
スタと、このトランジスタのベースにアノードが接続さ
れた第２のダイオードと、このダイオードのカソードと
第１のダイオードのカソードを接続する抵抗と、前記第
４のトランジスタのコレクタと前記第３のトランジスタ
のベースを接続する抵抗とを有することを特徴とする発
光ダイオードの断線及び短絡故障検出回路。1. A light emitting diode having an anode connected to a power supply line, a first transistor for driving the light emitting diode, and a first transistor connecting a cathode of the light emitting diode and a collector of the first transistor. A resistor, a first diode having an anode connected to the cathode of the light emitting diode, a second resistor connecting the cathode of the diode to the base of a second transistor, and a collector connected to the emitter of the second transistor. A third transistor whose emitter is connected to the ground line, a fourth transistor whose emitter is connected to the power supply line, a second diode whose anode is connected to the base of this transistor, and a cathode of this diode. The resistor connecting the cathode of the first diode and the resistor of the fourth transistor. A disconnection and short-circuit fault detection circuit for a light emitting diode, comprising a resistor and a resistor connecting the base of the third transistor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP8246492A JP2814160B2 (en) | 1992-04-03 | 1992-04-03 | Light emitting diode disconnection and short circuit fault detection circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP8246492A JP2814160B2 (en) | 1992-04-03 | 1992-04-03 | Light emitting diode disconnection and short circuit fault detection circuit |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH05283748A true JPH05283748A (en) | 1993-10-29 |
| JP2814160B2 JP2814160B2 (en) | 1998-10-22 |
Family
ID=13775235
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP8246492A Expired - Fee Related JP2814160B2 (en) | 1992-04-03 | 1992-04-03 | Light emitting diode disconnection and short circuit fault detection circuit |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2814160B2 (en) |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2006016706A1 (en) * | 2004-08-13 | 2006-02-16 | Semiconductor Energy Laboratory Co., Ltd. | Light emitting device and driving method thereof |
| JP2007005257A (en) * | 2005-06-27 | 2007-01-11 | Matsushita Electric Works Ltd | Lighting system |
| JP2010107341A (en) * | 2008-10-30 | 2010-05-13 | Hitachi Automotive Systems Ltd | Power supply circuit |
| US7973670B2 (en) | 2005-12-28 | 2011-07-05 | Semiconductor Energy Laboratory Co., Ltd. | Display device and method for inspecting the same |
| US8044949B2 (en) | 2005-05-02 | 2011-10-25 | Semiconductor Energy Laboratory Co., Ltd. | Light emitting device and electronic apparatus for displaying images |
| JP2020502549A (en) * | 2016-12-20 | 2020-01-23 | 京東方科技集團股▲ふん▼有限公司Ｂｏｅ Ｔｅｃｈｎｏｌｏｇｙ Ｇｒｏｕｐ Ｃｏ．，Ｌｔｄ． | OLED pixel circuit, driving method thereof, and display device |
-
1992
- 1992-04-03 JP JP8246492A patent/JP2814160B2/en not_active Expired - Fee Related
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2006016706A1 (en) * | 2004-08-13 | 2006-02-16 | Semiconductor Energy Laboratory Co., Ltd. | Light emitting device and driving method thereof |
| US7923937B2 (en) | 2004-08-13 | 2011-04-12 | Semiconductor Energy Laboratory Co., Ltd. | Light emitting device and driving method thereof |
| US8354794B2 (en) | 2004-08-13 | 2013-01-15 | Semiconductor Energy Laboratory Co., Ltd. | Light emitting device and driving method thereof |
| US8044949B2 (en) | 2005-05-02 | 2011-10-25 | Semiconductor Energy Laboratory Co., Ltd. | Light emitting device and electronic apparatus for displaying images |
| JP2007005257A (en) * | 2005-06-27 | 2007-01-11 | Matsushita Electric Works Ltd | Lighting system |
| US7973670B2 (en) | 2005-12-28 | 2011-07-05 | Semiconductor Energy Laboratory Co., Ltd. | Display device and method for inspecting the same |
| JP2010107341A (en) * | 2008-10-30 | 2010-05-13 | Hitachi Automotive Systems Ltd | Power supply circuit |
| JP2020502549A (en) * | 2016-12-20 | 2020-01-23 | 京東方科技集團股▲ふん▼有限公司Ｂｏｅ Ｔｅｃｈｎｏｌｏｇｙ Ｇｒｏｕｐ Ｃｏ．，Ｌｔｄ． | OLED pixel circuit, driving method thereof, and display device |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2814160B2 (en) | 1998-10-22 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP2881755B2 (en) | Power element drive circuit | |
| CN111739458B (en) | Drive circuit and display drive chip | |
| JP2814160B2 (en) | Light emitting diode disconnection and short circuit fault detection circuit | |
| JPH0630543B2 (en) | Output circuit abnormality detection notification circuit | |
| CN107481678A (en) | Backlight drive current monitoring circuit, method and the display device of backlight module | |
| WO2022156195A1 (en) | Test board | |
| JP2005051317A (en) | Signal output circuit, detection switch, and multiple optical axis photoelectric switch | |
| CN112701654B (en) | Short-circuit protection device, circuit system and short-circuit protection method thereof | |
| JP2008098495A (en) | Led fault detection apparatus | |
| EP0479515B1 (en) | Logic circuit including a fault detection circuit | |
| CN1396658A (en) | Semiconductor integrated circuit | |
| JPH11150461A (en) | High voltage switch circuit | |
| JP2000354322A (en) | Protection relay | |
| JP3401827B2 (en) | Bipolar output circuit | |
| CN220207801U (en) | Bypass contactor fault detection device | |
| JP3311764B2 (en) | Photoelectric switch | |
| KR0132233Y1 (en) | Main power control circuit for projection tv | |
| JP2601172Y2 (en) | IGBT drive circuit protection circuit | |
| JPH06276072A (en) | Driving control circuit for semiconductor switch | |
| JP2000028655A (en) | Output disconnection monitoring circuit of low-voltage power supply | |
| JP3625402B2 (en) | Semiconductor laser driving circuit, semiconductor laser chip inspection apparatus and assembly apparatus having the same | |
| KR920004335Y1 (en) | Driving apparatus for inverter | |
| JPS6110449Y2 (en) | ||
| JP2571745Y2 (en) | Protection circuit for load drive circuit | |
| JPS643079Y2 (en) |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| S111 | Request for change of ownership or part of ownership |
Free format text: JAPANESE INTERMEDIATE CODE: R313111 |
|
| R350 | Written notification of registration of transfer |
Free format text: JAPANESE INTERMEDIATE CODE: R350 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20080814 Year of fee payment: 10 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20080814 Year of fee payment: 10 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20090814 Year of fee payment: 11 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20090814 Year of fee payment: 11 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20100814 Year of fee payment: 12 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20100814 Year of fee payment: 12 |
|
| RD03 | Notification of appointment of power of attorney |
Free format text: JAPANESE INTERMEDIATE CODE: R3D03 |
|
| LAPS | Cancellation because of no payment of annual fees |