JP3181770B2 - Light emitting diode drive circuit - Google Patents
Light emitting diode drive circuitInfo
- Publication number
- JP3181770B2 JP3181770B2 JP26652093A JP26652093A JP3181770B2 JP 3181770 B2 JP3181770 B2 JP 3181770B2 JP 26652093 A JP26652093 A JP 26652093A JP 26652093 A JP26652093 A JP 26652093A JP 3181770 B2 JP3181770 B2 JP 3181770B2
- Authority
- JP
- Japan
- Prior art keywords
- emitting diode
- light emitting
- turned
- transistor
- transistors
- 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.)
- Expired - Fee Related
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Description
【０００１】[0001]
【産業上の利用分野】本発明は、光通信機器等に使用す
る発光ダイオードを点滅駆動するための発光ダイオード
駆動回路に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting diode driving circuit for blinking a light emitting diode used in an optical communication device or the like.
【０００２】[0002]
【従来の技術】発光ダイオードの点灯および消灯によっ
て信号を伝送する場合、発光ダイオードの順方向電圧Ｖ
ｆは、図２に示す発光ダイオードの等価回路において、
直列抵抗Ｒｓと拡散容量Ｃｄおよび並列抵抗Ｒｐ（ただ
し、順方向電流Ｉｆによって変動する）の並列回路との
直列回路から求められる時定数にしたがって上昇・下降
する。このため、一定電流で発光ダイオードを点灯させ
ようとすると、高速の信号伝送時に不都合が生じる。2. Description of the Related Art When a signal is transmitted by turning on and off a light emitting diode, a forward voltage V of the light emitting diode is used.
f is the equivalent circuit of the light emitting diode shown in FIG.
It rises / falls according to a time constant obtained from a series circuit of a series circuit of a series resistor Rs, a diffusion capacitor Cd, and a parallel resistor Rp (which fluctuates depending on the forward current If). For this reason, if the light emitting diode is turned on with a constant current, inconvenience occurs at the time of high-speed signal transmission.
【０００３】そこで、従来の発光ダイオード駆動回路
は、図３に示すように、差動増幅回路を構成する一対の
トランジスタＱ１，Ｑ２の一方のトランジスタＱ１のコ
レクタ側に発光ダイオードＤを接続し、さらにトランジ
スタＱ１のベース側にコンデンサＣ１および抵抗Ｒ１の
並列回路を、トランジスタＱ２のベース側にコンデンサ
Ｃ２および抵抗Ｒ２の並列回路を、それぞれ並列ピーキ
ングとして接続する構成を有する。Therefore, in the conventional light emitting diode driving circuit, as shown in FIG. 3, a light emitting diode D is connected to the collector side of one of the pair of transistors Q1 and Q2 constituting the differential amplifier circuit, and furthermore, A parallel circuit of a capacitor C1 and a resistor R1 is connected to the base of the transistor Q1 and a parallel circuit of a capacitor C2 and a resistor R2 is connected to the base of the transistor Q2 as parallel peaking.
【０００４】この構成において、トランジスタＱ１側の
入力電圧ｖ１がトランジスタＱ２側の入力電圧ｖ２より
大きくなると発光ダイオードＤが点灯し、トランジスタ
Ｑ２側の入力電圧ｖ２がトランジスタＱ１側の入力電圧
ｖ１より大きくなると発光ダイオードＤが消灯する。In this configuration, when the input voltage v1 on the transistor Q1 side becomes higher than the input voltage v2 on the transistor Q2 side, the light emitting diode D is turned on, and when the input voltage v2 on the transistor Q2 side becomes higher than the input voltage v1 on the transistor Q1 side. The light emitting diode D turns off.
【０００５】しかも、この構成によれば、高速の信号伝
送時にトランジスタＱ１，Ｑ２のベース電圧にピーキン
グをかけることで、一時的に発光ダイオードＤの順方向
電流を増加させ、発光ダイオードＤの点灯に要する時間
を短縮できる。In addition, according to this configuration, the peak current of the transistors Q1 and Q2 is peaked at the time of high-speed signal transmission, thereby temporarily increasing the forward current of the light emitting diode D, thereby turning on the light emitting diode D. The time required can be reduced.
【０００６】[0006]
【発明が解決しようとする課題】ところが、従来の発光
ダイオード駆動回路では、発光ダイオードＤの消灯時は
発光ダイオードＤの順方向電流をゼロにして内部容量Ｃ
ｄの自然放電によって消灯するようにしているため、消
灯時間の短縮が図れなかった。However, in the conventional light emitting diode driving circuit, when the light emitting diode D is turned off, the forward current of the light emitting diode D is reduced to zero and the internal capacitance C is reduced.
Since the light was turned off by the spontaneous discharge of d, the light-off time could not be reduced.
【０００７】また、発光ダイオードＤの電圧−電流特性
は、図４に示すように、順方向電圧Ｖｆが所定の電位を
超えると順方向電流Ｉｆが急峻に立ち上がる順方向特性
と、逆方向電圧Ｖｒが所定の電位を超えると逆方向電流
Ｉｒが急峻に立ち下がる逆方向特性とを有し、しかも発
光ダイオードＤの発光強度は順方向電流Ｉｆに比例する
ため、一度発光ダイオードＤの蓄積電荷を放電し切って
しまうと、再度点灯するには発光ダイオードＤが発光し
始める電位（図４のＡ点）まで内部容量Ｃｄを充電しな
ければならず、点灯までの時間を短縮する妨げとなって
いた。As shown in FIG. 4, the voltage-current characteristics of the light emitting diode D include a forward voltage characteristic in which the forward current If rises sharply when the forward voltage Vf exceeds a predetermined potential, and a reverse voltage Vr. Has a reverse characteristic in which the reverse current Ir sharply falls when the potential exceeds a predetermined potential, and since the light emission intensity of the light emitting diode D is proportional to the forward current If, the accumulated charge of the light emitting diode D is once discharged. If the lighting is completed, the internal capacitance Cd must be charged to a potential (point A in FIG. 4) at which the light-emitting diode D starts to emit light again, which hinders shortening the time until lighting. .
【０００８】本発明の目的は、発光ダイオードの消灯お
よび点灯時間を短縮して高速な信号伝送が可能な発光ダ
イオード駆動回路を提供することにある。SUMMARY OF THE INVENTION An object of the present invention is to provide a light emitting diode drive circuit capable of shortening the time for turning off and turning on the light emitting diode and transmitting signals at high speed.
【０００９】[0009]
【課題を解決するための手段】本発明による発光ダイオ
ード駆動回路は、一方のトランジスタの出力に発光ダイ
オードを接続した第１の差動増幅回路と、この第１の差
動増幅回路と同一の入力を有し一方のトランジスタの出
力に抵抗を接続した第２の差動増幅回路と、コレクタ端
子およびエミッタ端子が発光ダイオードの両端に接続さ
れ、コレクタ端子およびベース端子が抵抗の両端に接続
された放電用トランジスタとを設け、第１および第２の
差動増幅回路の各一方のトランジスタのオンによって発
光ダイオードが点灯すると共に放電用トランジスタが遮
断し、第１および第２の差動増幅回路の各一方のトラン
ジスタのオフによって発光ダイオードが消灯すると共に
放電用トランジスタが導通して発光ダイオードの内部電
荷を放電し、且つ、該発光ダイオードの端子間電圧を予
め定めた消灯時の電圧にまで引き下げるように構成す
る。According to the present invention, a light emitting diode driving circuit according to the present invention has a first differential amplifier circuit in which a light emitting diode is connected to the output of one of the transistors, and the same input as the first differential amplifier circuit. A second differential amplifier circuit having a resistor connected to the output of one of the transistors, a discharge terminal having a collector terminal and an emitter terminal connected to both ends of the light emitting diode, and a collector terminal and a base terminal connected to both ends of the resistor. A light emitting diode is turned on by turning on one transistor of each of the first and second differential amplifier circuits, and the discharging transistor is cut off, so that each one of the first and second differential amplifier circuits is turned off. The light emitting diode is turned off by turning off the transistor, and the discharging transistor is turned on to discharge the internal charge of the light emitting diode, and Configured to pull down to a predetermined voltage during off voltage between the terminals of the light emitting diode.
【００１０】この場合、放電用トランジスタは、発光ダ
イオードの消灯時、すなわち導通時であってもベース・
エミッタ間に流れる一定電流によって発生する電位によ
って発光ダイオードの順方向のバイアス電圧を一定に保
ち、導通時であっても該発光ダイオードに電流を流すこ
とを可能とする。In this case, even when the light emitting diode is turned off, that is, when the light emitting diode is turned on, the discharging transistor is connected to the base transistor.
The forward bias voltage of the light emitting diode is kept constant by the potential generated by the constant current flowing between the emitters, so that the current can flow through the light emitting diode even during conduction.
【００１１】[0011]
【作用】本発明の構成において、発光ダイオード消灯時
は、発光ダイオードに流れる順方向電流をゼロにすると
共に、放電用トランジスタを導通させて発光ダイオード
の両端の電圧を強制的に消灯電位に下げることで発光ダ
イオードに蓄積された電荷の放電を促し、消灯にかかる
時間を短縮する。In the structure of the present invention, when the light emitting diode is turned off, the forward current flowing through the light emitting diode is reduced to zero, and the discharge transistor is turned on to forcibly lower the voltage across the light emitting diode to the light-off potential. Promotes the discharge of the electric charge stored in the light emitting diode, and shortens the time required for turning off the light.
【００１２】発光ダイオード点灯時は、発光ダイオード
消灯時も発光ダイオードに一定量の蓄積電荷が残ってい
るため、順方向電流の印加と共に発光が始まり、ピーキ
ングによる順方向電流の増加とあわせて点灯にかかる時
間を短縮する。When a light emitting diode is turned on, a certain amount of accumulated charge remains in the light emitting diode even when the light emitting diode is turned off. Therefore, light emission starts when a forward current is applied, and the light is turned on in conjunction with an increase in the forward current due to peaking. Reduce this time.
【００１３】[0013]
【実施例】図１は、本発明による発光ダイオード駆動回
路の一実施例を示す構成図で、図３に示す構成と同一部
分には同一符号を付して説明する。本実施例は、差動増
幅回路１を構成するトランジスタＱ１，Ｑ２の一方のト
ランジスタＱ１のコレクタ側に発光ダイオードＤを接続
し、トランジスタＱ１のベースに並列ピーキングとして
のコンデンサＣ１および抵抗Ｒ１の並列回路を接続し、
トランジスタＱ２のベースに並列ピーキングとしてのコ
ンデンサＣ２および抵抗Ｒ２の並列回路を接続する構成
を有する。FIG. 1 is a block diagram showing one embodiment of a light emitting diode drive circuit according to the present invention. The same parts as those shown in FIG. In this embodiment, a light emitting diode D is connected to the collector side of one of the transistors Q1 and Q2 of the differential amplifier circuit 1, and a parallel circuit of a capacitor C1 and a resistor R1 as a parallel peaking is connected to the base of the transistor Q1. And connect
It has a configuration in which a parallel circuit of a capacitor C2 and a resistor R2 as parallel peaking is connected to the base of the transistor Q2.
【００１４】また、差動増幅回路１と並列に一対のトラ
ンジスタＱ３，Ｑ４からなる差動増幅回路２を備え、さ
らに、発光ダイオードＤの蓄積電荷を放電するために差
動増幅回路１と並列に接続されたトランジスタＱ５を備
え、トランジスタＱ５のベース端子はトランジスタＱ３
のコレクタおよび抵抗Ｒ３の接続中点に、トランジスタ
Ｑ５のエミッタ端子は発光ダイオードＤのカソードに、
トランジスタＱ５のコレクタ端子は発光ダイオードＤの
アノードに、それぞれ接続されている。Further, a differential amplifier circuit 2 comprising a pair of transistors Q3 and Q4 is provided in parallel with the differential amplifier circuit 1, and further in parallel with the differential amplifier circuit 1 for discharging the accumulated charge of the light emitting diode D. A transistor Q5 is connected, and the base terminal of the transistor Q5 is connected to the transistor Q3.
, The emitter terminal of the transistor Q5 is connected to the cathode of the light emitting diode D,
The collector terminal of the transistor Q5 is connected to the anode of the light emitting diode D, respectively.
【００１５】さらに、トランジスタＱ１，Ｑ２のエミッ
タ側は定電流源ＩＦに接続され、トランジスタＱ３，Ｑ
４のエミッタ側は定電流源ＩＧに接続され、トランジス
タＱ５のエミッタ側は定電流源ＩＨに接続され、それぞ
れ定電流Ｉf ，Ｉg ，Ｉh が流れるように構成されてい
る。Further, the emitters of the transistors Q1 and Q2 are connected to a constant current source IF.
The emitter side of the transistor 4 is connected to a constant current source IG, and the emitter side of the transistor Q5 is connected to a constant current source IH so that constant currents If, Ig, and Ih flow therethrough.
【００１６】この構成において、外部から消灯信号が入
ると、トランジスタＱ２，Ｑ４側の入力電圧ｖ２がトラ
ンジスタＱ１，Ｑ３側の入力電圧ｖ１より大きくなるの
で、トランジスタＱ２，Ｑ４がオンとなり、トランジス
タＱ１，Ｑ３がオフとなる。これにより、トランジスタ
Ｑ１のコレクタには電流が流れないため発光ダイオード
Ｄは消灯する。In this configuration, when a light-off signal is input from the outside, the input voltage v2 on the transistors Q2 and Q4 becomes higher than the input voltage v1 on the transistors Q1 and Q3, so that the transistors Q2 and Q4 are turned on and the transistors Q1 and Q1 are turned on. Q3 turns off. As a result, since no current flows through the collector of the transistor Q1, the light emitting diode D is turned off.
【００１７】しかし、この場合、発光ダイオードＤが光
らない程度のバイアス電流Ｉ0 を流すとすると、トラン
ジスタＱ５のエミッタに流れる電流は、Ｉh −Ｉ0 とな
る。したがって、発光ダイオードＤの両端には、次式で
定まる電圧Ｖoff がかかることになる。[0017] However, in this case, the flow of the bias current I 0 to the extent that the light emitting diode D is not light, the current flowing through the emitter of the transistors Q5, the Ih -I 0. Therefore, a voltage Voff determined by the following equation is applied to both ends of the light emitting diode D.
【００１８】 Ｖoff ＝ｋＴ／ｑ・ｌn ((Ｉh −Ｉ0 ）／Ｉs ） ＋Ｒ３・（Ｉh −Ｉ0 ）／ｈfe ただし、ｋ：ボルツマン定数 Ｔ：周囲温度（Ｋ） ｑ：電子のエネルギー Ｉs ：トランジスタＱ５の逆方向飽和電流 ｈfe：トランジスタＱ５の電流増幅率Voff = kT / q · ln ((Ih− I0 ) / Is) + R3 · (Ih− I0 ) / hfe where k: Boltzmann constant T: ambient temperature (K) q: electron energy Is : Reverse saturation current of transistor Q5 h fe : current amplification factor of transistor Q5
【００１９】この電圧Ｖoff はトランジスタＱ５のベー
ス・エミッタ間電圧と抵抗Ｒ３の降下電圧との和であ
る。また、トランジスタＱ５はエミッタ電流（Ｉh −Ｉ
0 ）で発光ダイオードＤの蓄積電荷を放電するため、発
光ダイオードＤの消灯までの時間を短縮することができ
る。This voltage Voff is the sum of the base-emitter voltage of the transistor Q5 and the voltage drop of the resistor R3. The transistor Q5 has an emitter current (Ih-I
Since the accumulated charge of the light emitting diode D is discharged in 0 ), the time until the light emitting diode D is turned off can be shortened.
【００２０】次に、外部から点灯信号が入ると、トラン
ジスタＱ１，Ｑ３側の入力電圧ｖ１がトランジスタＱ
２，Ｑ４側の入力電圧ｖ２より大きくなるので、トラン
ジスタＱ１，Ｑ３がオンとなり、トランジスタＱ２，Ｑ
４がオフとなる。これにより、トランジスタＱ１のコレ
クタに電流Ｉf が流れ、トランジスタＱ３のコレクタに
電流Ｉg が流れる。Next, when a lighting signal is input from the outside, the input voltage v1 on the transistors Q1 and Q3 side becomes the transistor Q1.
Since the input voltage V2 is higher than the input voltage v2 on the side of the transistors Q2 and Q4, the transistors Q1 and Q3 are turned on, and the transistors Q2 and Q3 are turned on.
4 turns off. As a result, the current If flows through the collector of the transistor Q1, and the current Ig flows through the collector of the transistor Q3.
【００２１】発光ダイオードＤの点灯時の順方向電圧を
Ｖｆとすると、抵抗Ｒ３の降下電圧Ｉg ×Ｒ３が電圧Ｖ
ｆより大きくなるように電流Ｉg を設定すれば、発光ダ
イオードＤの点灯時にはトランジスタＱ５が遮断し、発
光ダイオードＤに流れる電流は「Ｉf ＋Ｉｈ 」とな
る。Assuming that the forward voltage when the light emitting diode D is turned on is Vf, the drop voltage Ig × R3 of the resistor R3 is the voltage V
If the current Ig is set to be larger than f, the transistor Q5 is turned off when the light emitting diode D is turned on, and the current flowing through the light emitting diode D becomes “If + Ih”.
【００２２】したがって、この電流がピーキングによっ
て急峻に発光ダイオードＤに流れ込み、さらに発光ダイ
オードＤは消灯時に電圧Ｖoff 分の電荷を予め蓄積して
いるため点灯までの時間が短縮される。Therefore, this current sharply flows into the light emitting diode D due to the peaking, and the light emitting diode D previously stores the charge corresponding to the voltage Voff when the light is turned off, so that the time until the light is turned on is reduced.
【００２３】[0023]
【発明の効果】本発明によれば、発光ダイオードの消灯
時は、点灯時に蓄積された内部電荷を強制的に放電する
ので消灯にかかる時間を短縮することができる。また、
発光ダイオードの点灯時は、消灯時に点灯しない程度の
バイアス電圧をかけてあるので点灯にかかる時間を短縮
することができる。これにより既存の発光ダイオードを
用いてより高速な信号伝送が可能になる。According to the present invention, when the light emitting diode is turned off, the internal charges accumulated when the light emitting diode is turned on are forcibly discharged, so that the time required for turning off the light emitting diode can be reduced. Also,
When the light-emitting diode is turned on, a bias voltage that does not turn on when the light-emitting diode is turned off is applied, so that the time required for lighting can be reduced. This enables faster signal transmission using existing light emitting diodes.
【図１】本発明による発光ダイオード駆動回路の一実施
例を示す構成図である。FIG. 1 is a configuration diagram showing one embodiment of a light emitting diode drive circuit according to the present invention.
【図２】発光ダイオードの等価回路である。FIG. 2 is an equivalent circuit of a light emitting diode.
【図３】従来の発光ダイオード駆動回路の構成図であ
る。FIG. 3 is a configuration diagram of a conventional light emitting diode drive circuit.
【図４】発光ダイオードの電圧−電流特性図である。FIG. 4 is a voltage-current characteristic diagram of a light emitting diode.
１，２ 差動増幅回路 Ｃ１，Ｃ２ コンデンサ Ｄ 発光ダイオード ＩＦ，ＩＧ，ＩＨ 定電流源 Ｑ１，Ｑ２，Ｑ３，Ｑ４，Ｑ５ トランジスタ Ｒ１，Ｒ２，Ｒ３ 抵抗 Ｃｄ 拡散容量 Ｒｐ 並列抵抗 Ｒｓ 直列抵抗 1,2 Differential amplifier circuit C1, C2 Capacitor D Light emitting diode IF, IG, IH Constant current source Q1, Q2, Q3, Q4, Q5 Transistor R1, R2, R3 Resistance Cd Diffusion capacitance Rp Parallel resistance Rs Series resistance
Claims (1)
ードを接続した第１の差動増幅回路と、 前記第１の差動増幅回路と同一の入力を有し一方のトラ
ンジスタの出力に抵抗を接続した第２の差動増幅回路
と、 コレクタ端子およびエミッタ端子が前記発光ダイオード
の両端に接続され、コレクタ端子およびベース端子が前
記抵抗の両端に接続され、導通時であってもベース・エ
ミッタ間に流れる一定電流によって発生する電位を該発
光ダイオードの順方向バイアス電圧として該発光ダイオ
ードに電流を流す放電用トランジスタとを備え、 前記第１および第２の差動増幅回路の各一方のトランジ
スタのオンによって、前記発光ダイオードが点灯すると
共に、前記放電用トランジスタが遮断し、 前記第１および第２の差動増幅回路の各一方のトランジ
スタのオフによって、前記発光ダイオードが消灯すると
共に、前記放電用トランジスタが導通して該発光ダイオ
ードの内部電荷を放電し、且つ、該発光ダイオードの端
子間電圧を予め定めた消灯時の電圧にまで引き下げるこ
とを特徴とする発光ダイオード駆動回路。1. A first differential amplifier circuit in which a light emitting diode is connected to an output of one of the transistors, and a resistor connected to an output of one of the transistors having the same input as the first differential amplifier circuit. a second differential amplifier circuit, a collector terminal and an emitter terminal connected to both ends of the light emitting diode, the collector terminal and the base terminal connected to both ends of said resistor, the base-e even when conductive
The potential generated by the constant current flowing between
The light emitting diode is used as a forward bias voltage of the photodiode.
A discharge transistor that causes a current to flow through the circuit, and when one of the transistors of the first and second differential amplifier circuits is turned on, the light emitting diode is turned on, and the discharge transistor is turned off. by off of each one of the transistors of the first and second differential amplifier circuit, together with the light emitting diode is turned off, said discharging transistor is rendered conductive to discharge the internal charge of the light-emitting diode, and, the light emitting diode End of
LED driving circuit according to claim and this <br/> pulling up the voltage when turned off with predetermined child voltage.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP26652093A JP3181770B2 (en) | 1993-10-25 | 1993-10-25 | Light emitting diode drive circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP26652093A JP3181770B2 (en) | 1993-10-25 | 1993-10-25 | Light emitting diode drive circuit |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH07122783A JPH07122783A (en) | 1995-05-12 |
| JP3181770B2 true JP3181770B2 (en) | 2001-07-03 |
Family
ID=17432039
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP26652093A Expired - Fee Related JP3181770B2 (en) | 1993-10-25 | 1993-10-25 | Light emitting diode drive circuit |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3181770B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8439460B2 (en) * | 2008-08-22 | 2013-05-14 | Bsh Bosch Und Siemens Hausgeraete Gmbh | Domestic appliance for installation in a furniture frame |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP6029053B2 (en) * | 2011-08-05 | 2016-11-24 | 学校法人 東洋大学 | Semiconductor light emitting device |
| JP2012028820A (en) * | 2011-11-07 | 2012-02-09 | Omron Corp | Led drive circuit |
-
1993
- 1993-10-25 JP JP26652093A patent/JP3181770B2/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8439460B2 (en) * | 2008-08-22 | 2013-05-14 | Bsh Bosch Und Siemens Hausgeraete Gmbh | Domestic appliance for installation in a furniture frame |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH07122783A (en) | 1995-05-12 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| LAPS | Cancellation because of no payment of annual fees |