JP2002190392A - Led drive circuit - Google Patents
Led drive circuitInfo
- Publication number
- JP2002190392A JP2002190392A JP2000386273A JP2000386273A JP2002190392A JP 2002190392 A JP2002190392 A JP 2002190392A JP 2000386273 A JP2000386273 A JP 2000386273A JP 2000386273 A JP2000386273 A JP 2000386273A JP 2002190392 A JP2002190392 A JP 2002190392A
- Authority
- JP
- Japan
- Prior art keywords
- current limiting
- led
- current
- circuit
- limiting resistor
- 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.)
- Pending
Links
Landscapes
- Circuit Arrangement For Electric Light Sources In General (AREA)
- Liquid Crystal Display Device Control (AREA)
- Control Of Indicators Other Than Cathode Ray Tubes (AREA)
- Control Of El Displays (AREA)
- Led Devices (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、ＬＥＤ駆動回路に
関し、特に、ＬＥＤを駆動する電源電圧が変動してもＬ
ＥＤの輝度をほぼ一定に保つことを可能としたＬＥＤ駆
動回路に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an LED driving circuit, and more particularly, to an LED driving circuit which operates even when a power supply voltage for driving an LED fluctuates.
The present invention relates to an LED driving circuit capable of keeping the luminance of an ED almost constant.
【０００２】[0002]
【従来の技術】図５に従来のＬＥＤ駆動回路を示す。2. Description of the Related Art FIG. 5 shows a conventional LED drive circuit.
【０００３】図５において、電源電圧（＝電池パック）
５１はＬＥＤ５２のアノードに接続され、カソードは電
流制限抵抗５３に接続されている。電流制限抵抗５３は
トランジスタＴｒ５４のドレインに接続され、Ｔｒ５４
のソースは接地され、ゲートは制御部５５に接続されて
いる。In FIG. 5, a power supply voltage (= battery pack)
51 is connected to the anode of the LED 52, and the cathode is connected to the current limiting resistor 53. The current limiting resistor 53 is connected to the drain of the transistor Tr54.
Are connected to the ground, and the gate is connected to the control unit 55.
【０００４】図５に示された従来例の動作について説明
するに、ＬＥＤ５２を“ＯＮ”（点灯）する場合には、
Ｔｒ５４のゲートを“ＨＩＧＨ”、ＬＥＤ５２を“ＯＦ
Ｆ”（消灯）する場合には“ＬＯＷ”とする。The operation of the conventional example shown in FIG. 5 will be described. When the LED 52 is turned "ON" (lit),
The gate of Tr54 is set to "HIGH" and the LED 52 is set to "OF".
When "F" (light is turned off), "LOW" is set.
【０００５】ユーザが何らかのアクション（スイッチＳ
Ｗ操作等）を行った場合に、制御部５５はこれを感知
し、Ｔｒ５４のゲートを“ＨＩＧＨ”にしてＬＥＤ５２
を“ＯＮ”にする。[0005] When the user performs some action (switch S
When a W operation or the like is performed, the control unit 55 senses this, sets the gate of the Tr 54 to “HIGH”, and sets the LED 52
To “ON”.
【０００６】しばらくの間アクションが無ければ、ＬＥ
Ｄ不必要と判断し、Ｔｒ５４を“ＬＯＷ”にしてＬＥＤ
５２を“ＯＦＦ”とする。これがＬＥＤの動作である。If there is no action for a while, LE
D is unnecessary and set Tr54 to "LOW" and LED
52 is set to “OFF”. This is the operation of the LED.
【０００７】現在ますます情報化が進むモバイルシーン
の中でＬＣＤ（Ｌｉｑｕｉｄ Ｃｒｙｓｔａｌ Ｄｉｓ
ｐｌａｙ）の果たす役割がさらに重要になってきてい
る。そのＬＣＤを見やすくするために使用されるＬＥＤ
（Ｌｉｇｈｔ Ｅｍｉｔｔｉｎｇ Ｄｉｏｄｅ、発光ダ
イオード）バックライトの輝度を一定に保ち、ユーザに
快適な視野性を提供することが要望されている。[0007] In the mobile scene, which is increasingly information-oriented, LCD (Liquid Crystal Dis)
play) has become even more important. LEDs used to make the LCD easier to see
(Light Emitting Diode, Light Emitting Diode) There is a demand for maintaining a constant luminance of a backlight and providing a comfortable visual field to a user.
【０００８】[0008]
【発明が解決しようとする課題】ＬＥＤは流れる電流に
より輝度（明るさ）が変化する。電流が多く流れれば輝
度は高く、電流が少なく流れれば輝度は低い。ここで、
従来ＬＥＤ駆動回路において問題となってくるのが、電
池パック電圧は変化するということである。フル充電さ
れた電池パック電圧は４Ｖ、低電圧警報がでる電圧は３
Ｖであり、１Ｖの差がここで生ずる。電源電圧に１Ｖの
差が生ずると輝度にも差が生じてしまう。電流で比較す
ると４Ｖで３３ｍＡ、３Ｖで２３ｍＡ、１Ｖの電圧差で
ＬＥＤに流れる電流は１０ｍＡも変化してしまう。この
１０ｍＡの電流差はＬＥＤの輝度の差につながる。The brightness (brightness) of an LED changes according to the flowing current. The luminance increases when a large amount of current flows, and the luminance decreases when a small amount of current flows. here,
A problem in the conventional LED drive circuit is that the battery pack voltage changes. The voltage of a fully charged battery pack is 4 V, and the voltage at which a low voltage alarm is issued is 3
V and a difference of 1 V occurs here. If a difference of 1V occurs in the power supply voltage, a difference also occurs in luminance. When compared with the current, the current flowing through the LED changes by as much as 10 mA with a voltage difference of 33 mA at 4 V, 23 mA at 3 V, and 1 V. This 10 mA current difference leads to a difference in LED brightness.
【０００９】この電流の計算としては、図５の電流制限
抵抗５３の抵抗値＝１００Ω、ＬＥＤ５２のＶＦ（順方
向電圧）＝０．７Ｖ近似として、電池パック５１の電圧
が４Ｖならば、＜（４−０．７）／１００＞で求められ
る。故に、従来の回路では電池パック電圧値によってＬ
ＥＤの輝度が変化してしまうという欠点があった。The calculation of this current is as follows. Assuming that the resistance value of the current limiting resistor 53 in FIG. 4-0.7) / 100>. Therefore, in the conventional circuit, L depends on the battery pack voltage value.
There is a disadvantage that the luminance of the ED changes.
【００１０】本発明は従来の上記実情に鑑みてなされた
ものであり、従って本発明の目的は、従来の技術に内在
する上記欠点を解消すると共に、上記要望を満足させる
ことを可能とした新規なＬＥＤ駆動回路を提供すること
にある。SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional circumstances, and accordingly, an object of the present invention is to solve the above-mentioned disadvantages inherent in the prior art and to satisfy the above-mentioned demands. Another object of the present invention is to provide a simple LED driving circuit.
【００１１】[0011]
【課題を解決するための手段】上記目的を達成する為
に、本発明に係るＬＥＤ駆動回路は、ＬＥＤを有する携
帯型端末装置において、前記ＬＥＤの電流を制限する第
１の電流制限回路と、該第１の電流制限回路に直列に接
続された複数の第２の電流制限回路と、該第２の電流制
限回路の“ＯＮ／ＯＦＦ”を制御する制御手段とを備え
て構成され、前記第２の電流制限回路の組み合わせと、
前記第１の電流制限回路の組み合わせにより前記ＬＥＤ
に流れる電流をほぼ一定に保つことを特徴としている。In order to achieve the above object, an LED driving circuit according to the present invention comprises: a portable terminal device having an LED; a first current limiting circuit for limiting a current of the LED; A plurality of second current limiting circuits connected in series to the first current limiting circuit; and control means for controlling “ON / OFF” of the second current limiting circuit. A combination of two current limiting circuits;
The LED according to the combination of the first current limiting circuit
It is characterized in that the current flowing through is kept substantially constant.
【００１２】前記第１の電流制限回路は第１の電流制限
抵抗を有し、前記ＬＥＤは該第１の電流制限抵抗に直列
に接続されている。The first current limiting circuit has a first current limiting resistor, and the LED is connected in series to the first current limiting resistor.
【００１３】前記第２の電流制限回路は、第１のトラン
ジスタと、第２の電流制限抵抗と第２のトランジスタの
直列回路と、第３の電流制限抵抗と第３のトランジスタ
の直列回路とが並列に接続されて構成されている。[0013] The second current limiting circuit includes a first transistor, a series circuit of a second current limiting resistor and a second transistor, and a series circuit of a third current limiting resistor and a third transistor. It is configured to be connected in parallel.
【００１４】前記第１の電流制限回路を複数個設けるこ
ともできる。A plurality of the first current limiting circuits may be provided.
【００１５】前記ＬＥＤに供給される電圧を絶えずモニ
タして前記制御手段に報告する電圧モニタを有し、前記
制御手段は、前記電圧モニタより供給される電圧値を基
にして前記第２の電流制限回路を制御することを特徴と
している。A voltage monitor for continuously monitoring a voltage supplied to the LED and reporting the voltage to the control means, wherein the control means controls the second current based on a voltage value supplied from the voltage monitor; It is characterized in that the limiting circuit is controlled.
【００１６】前記ＬＥＤはＬＣＤのバックライトとして
使用される。The LED is used as a backlight of an LCD.
【００１７】[0017]
【発明の実施の形態】次に、本発明をその好ましい各実
施の形態について図面を参照しながら詳細に説明する。Next, preferred embodiments of the present invention will be described in detail with reference to the drawings.
【００１８】[0018]
【第１の実施の形態】図１は、本発明による第１の実施
の形態を示す基本的回路構成図である。FIG. 1 is a basic circuit configuration diagram showing a first embodiment according to the present invention.
【００１９】[0019]
【第１の実施の形態の構成】図１を参照するに、電源電
圧１１はＬＥＤ１２のアノードに接続され、ＬＥＤ１２
のカソードは電流制限抵抗（１）１３に接続されてい
る。Referring to FIG. 1, a power supply voltage 11 is connected to the anode of
Is connected to the current limiting resistor (1) 13.
【００２０】電流制限抵抗（１）１３は３つに分岐さ
れ、１つはトランジスタＴｒ（１）１４のドレインに、
１つは電流制限抵抗（２）１５に、もう１つは電流制限
抵抗（３）１６にそれぞれ接続されている。電流制限抵
抗（２）１５はトランジスタＴｒ（２）１７のドレイン
に、電流制限抵抗（３）１６はトランジスタＴｒ（３）
１８のドレインにそれぞれ接続されている。そしてそれ
ぞれのトランジスタＴｒのソースは接地され、ゲートは
制御部１９に接続されている。The current limiting resistor (1) 13 is branched into three, one is connected to the drain of the transistor Tr (1) 14,
One is connected to the current limiting resistor (2) 15 and the other is connected to the current limiting resistor (3) 16. The current limiting resistor (2) 15 is connected to the drain of the transistor Tr (2) 17, and the current limiting resistor (3) 16 is connected to the transistor Tr (3).
18 are connected to the respective drains. The source of each transistor Tr is grounded, and the gate is connected to the control unit 19.
【００２１】図４に本発明が適用される一般的な携帯電
話・ＰＨＳのブロック構成例を示す。FIG. 4 shows an example of a block configuration of a general portable telephone / PHS to which the present invention is applied.
【００２２】図４において、アンテナＡＮＴ４１は電波
を受信もしくは送信し、受信電波は無線部４２により増
幅され、制御部４３で復調されて音声となる。In FIG. 4, an antenna ANT41 receives or transmits a radio wave, and the received radio wave is amplified by a radio unit 42 and demodulated by a control unit 43 to be sound.
【００２３】送信する場合には、音声をディジタルデー
タに変換し、無線部４２にて変換されたディジタル信号
を変調し、アンテナＡＮＴ４１から変調した信号の電波
を送信する。When transmitting, the voice is converted into digital data, the digital signal converted by the radio section 42 is modulated, and the radio wave of the modulated signal is transmitted from the antenna ANT41.
【００２４】ＬＣＤ４４は時刻等の表示をし、キーＳＷ
４５は電話番号等の入力を行う。電池パック４６は装置
の電源で全ての動作用電源となる。ＬＥＤ４７はＬＣＤ
４４とキーＳＷ４５のバックライトを実現するものであ
り、暗闇での表示確認やキーＳＷ４５の確認に使われ、
制御部４３にて制御されている。電源は電池パック４６
である。４８は電圧モニタであり、電池パック４６の電
圧を絶えずモニタし、その結果を制御部４３へ報告して
いる。これは主に残電池容量をユーザに報告するために
使われている。The LCD 44 displays the time, etc.
Numeral 45 inputs a telephone number and the like. The battery pack 46 is a power source for the apparatus and serves as a power source for all operations. LED47 is LCD
It realizes the backlight of 44 and key SW45, and is used for confirmation of display in darkness and confirmation of key SW45,
It is controlled by the control unit 43. Power supply is battery pack 46
It is. Reference numeral 48 denotes a voltage monitor which constantly monitors the voltage of the battery pack 46 and reports the result to the control unit 43. This is mainly used to report the remaining battery capacity to the user.
【００２５】[0025]
【第１の実施の形態の動作】次に、本発明による第１の
実施の形態の動作について図面を参照して説明する。Next, the operation of the first embodiment according to the present invention will be described with reference to the drawings.
【００２６】図２は本発明に係るＬＥＤ駆動回路の第１
の実施の形態の一実施例を示す回路構成図である。FIG. 2 shows the first embodiment of the LED driving circuit according to the present invention.
FIG. 3 is a circuit configuration diagram showing an example of the embodiment.
【００２７】図２を参照するに、図１と同様に、電池パ
ックの電圧１１はＬＥＤ１２のアノードに接続され、Ｌ
ＥＤ１２のカソードは電流制限抵抗（１）１３（＝例え
ば７０Ω）に接続される。電流制限抵抗（１）１３は３
つに別れ、１つはＴｒ（１）１４のドレインに、１つは
電流制限抵抗（２）１５（＝例えば２０Ω）に、もう１
つは電流制限抵抗（３）１６（＝例えば３０Ω）に接続
される。電流制限抵抗（２）１５はＴｒ（２）１７のド
レインに、電流制限抵抗（３）１６はＴｒ（３）１８の
ドレインに接続される。そしてＴｒ１４、Ｔｒ１７、Ｔ
ｒ１８のそれぞれのソースは接地され、ゲートは制御部
１９のＡ・Ｂ・Ｃ端子にそれぞれ接続される。Referring to FIG. 2, similarly to FIG. 1, the voltage 11 of the battery pack is connected to the anode of
The cathode of the ED 12 is connected to a current limiting resistor (1) 13 (= 70Ω, for example). The current limiting resistor (1) 13 is 3
One is connected to the drain of Tr (1) 14, one is connected to the current limiting resistor (2) 15 (= for example, 20Ω), and the other is connected to
One is connected to a current limiting resistor (3) 16 (= for example, 30Ω). The current limiting resistor (2) 15 is connected to the drain of Tr (2) 17, and the current limiting resistor (3) 16 is connected to the drain of Tr (3) 18. And Tr14, Tr17, T
The respective sources of r18 are grounded, and the gates are connected to the A, B, and C terminals of the control unit 19, respectively.
【００２８】制御部１９のＡ・Ｂ・Ｃ端子の“ＯＮ／Ｏ
ＦＦ”の組み合わせにより４種類の電流制限抵抗値を作
ることが可能になる。例えば、端子Ｃのみ“ＨＩＧＨ”
ならば、Ｔｒ４８のみ“ＯＮ”となり、トータル電流制
限抵抗値は、電流制限抵抗（１）１３（＝例えば７０
Ω）＋電流制限抵抗（３）１６（＝例えば３０Ω）で例
えば１００Ωとなる。"ON / O" of the A, B and C terminals of the control unit 19
It is possible to create four types of current limiting resistance values by combining FF ". For example, only terminal C is" HIGH "
Then, only the Tr 48 is turned “ON”, and the total current limiting resistance value becomes the current limiting resistance (1) 13 (= 70 for example).
Ω) + current limiting resistor (3) 16 (= 30 Ω, for example), for example, 100 Ω.
【００２９】また、電圧モニタ１１０は電池パック１１
の電圧を絶えずモニタし、制御部１９へ電圧を報告して
いる。The voltage monitor 110 is connected to the battery pack 11
Is constantly monitored, and the voltage is reported to the control unit 19.
【００３０】制御部１９は電圧モニタ１１０よりの電圧
値を元に端子Ａ・Ｂ・Ｃの制御を行う。The control unit 19 controls the terminals A, B and C based on the voltage value from the voltage monitor 110.
【００３１】表１に端子状態別のトータル電流制限抵抗
値を示す。Table 1 shows the total current limiting resistance for each terminal state.
【００３２】[0032]
【表１】 [Table 1]
【００３３】制御部１９の端子状態が“ＨＩＧＨ”なら
トランジスタＴｒは“ＯＮ”する。Ｔｒが“ＯＮ”した
経路に電流が流れ、その経路の電流制限抵抗＋電流制限
抵抗（１）１３がトータルの電流制限抵抗値となる。If the terminal state of the control unit 19 is "HIGH", the transistor Tr is turned "ON". A current flows through the path where Tr is “ON”, and the current limiting resistance of the path plus the current limiting resistance (1) 13 becomes the total current limiting resistance value.
【００３４】表１に示すように、４つの電流制限抵抗値
を作成することができる。それぞれを状態１〜４とす
る。この４状態を電源電圧別に使用すれば、ＬＣＤの輝
度はほぼ一定に保てることになる。例えば、電圧が高い
ときには電流制限抵抗値を高く選び、ＬＥＤに流れる電
流を抑え、電圧が低いときには電流制限抵抗値を低く選
んでＬＥＤに流れる電流を増やせばよい。As shown in Table 1, four current limiting resistance values can be created. These are referred to as states 1 to 4, respectively. If these four states are used for each power supply voltage, the brightness of the LCD can be kept almost constant. For example, when the voltage is high, the current limiting resistance value is selected to be high to suppress the current flowing through the LED, and when the voltage is low, the current limiting resistance value is selected to be low to increase the current flowing to the LED.
【００３５】表２に電源電圧（電池パック電圧）に対し
て状態１〜４をどのように使うかを示す。Table 2 shows how the states 1 to 4 are used for the power supply voltage (battery pack voltage).
【００３６】[0036]
【表２】 [Table 2]
【００３７】電源電圧が４〜３．９Ｖまでは状態４が選
択され、３．８〜３．６Ｖまでは状態３が、３．５〜
３．３Ｖまでは状態２が、３．２〜３．０Ｖまでは状態
１がそれぞれ選択されて使用される。State 4 is selected when the power supply voltage is 4 to 3.9 V, and State 3 is 3.5 to 3.8 to 3.6 V.
State 2 is selected and used up to 3.3 V, and state 1 is selected and used up to 3.2 to 3.0 V.
【００３８】このようにすることで、ＬＥＤに流れる電
流は従来回路で１０ｍＡの差が発生していたが、本発明
により３ｍＡ程度に収まっている。By doing so, the current flowing through the LED has a difference of 10 mA in the conventional circuit, but is reduced to about 3 mA by the present invention.
【００３９】ＬＥＤに流れる電流のばらつきが小さくな
ったかもしくは無くなったということは、ＬＥＤ輝度の
ばらつきが小さくなったかもしくは無くなったというこ
とになる。When the variation in the current flowing through the LED is reduced or eliminated, it means that the variation in the LED brightness is reduced or eliminated.
【００４０】図２の電流制限抵抗（２）１５、（３）１
６とそれらに接続されるトランジスタＴｒの組み合わせ
を増やせば、ＬＥＤに流れる電流を更に細かく分割でき
ることになり、より一層輝度は安定する。The current limiting resistors (2) 15, (3) 1 in FIG.
If the number of combinations of the transistors 6 and the transistors Tr connected thereto is increased, the current flowing through the LED can be divided more finely, and the luminance is further stabilized.
【００４１】また、本発明のＬＥＤ駆動回路は回路構成
が簡素であるということのみならず、ＩＣ化が非常に容
易なので、部品数の増加が少なく原価的なコストアップ
も少ない。Further, the LED drive circuit of the present invention is not only simple in circuit configuration, but also very easy to integrate into an IC, so that the number of parts is not increased and cost increase is small.
【００４２】[0042]
【第２の実施の形態】次に、本発明による第２の実施の
形態について図面を参照して説明する。Second Embodiment Next, a second embodiment according to the present invention will be described with reference to the drawings.
【００４３】図３は本発明による第２の実施の形態の一
実施例を示す回路構成図である。FIG. 3 is a circuit diagram showing an example of the second embodiment according to the present invention.
【００４４】図３を参照するに、前述した第１の実施の
形態に示すように、１つのＬＥＤを独立して駆動する場
合もあるが、大画面のＬＣＤのバックライトとしてＬＥ
Ｄを使う場合には、数個のＬＥＤをパラレルに使うこと
が多い。この様子を図５に示す。Referring to FIG. 3, there is a case where one LED is driven independently as shown in the above-described first embodiment, but the LE is used as a backlight for a large-screen LCD.
When D is used, several LEDs are often used in parallel. This is shown in FIG.
【００４５】図５において、ＬＥＤは５個パラレルに接
続されている（ＬＥＤ（１）３１〜（５）３５）。ま
た、ＬＥＤ３１〜３５のそれぞれに電流制限抵抗（１）
３６〜（５）３１０が接続されている。各電流制限抵抗
３６〜３１０の先には、Ｔｒ（１）３１１のドレイン、
電流制限抵抗（６）３１２、電流制限抵抗（７）３１３
がそれぞれ接続されている。In FIG. 5, five LEDs are connected in parallel (LEDs (1) 31 to (5) 35). Each of the LEDs 31 to 35 has a current limiting resistor (1).
36 to (5) 310 are connected. The drain of Tr (1) 311 is connected to the end of each of the current limiting resistors 36 to 310,
Current limiting resistor (6) 312, current limiting resistor (7) 313
Are connected respectively.
【００４６】電流制限抵抗（６）３１２、電流制限抵抗
（７）３１３はそれぞれＴｒ（２）３１４のドレイン、
Ｔｒ（３）３１５のドレインに接続され、Ｔｒ（１）３
１１、Ｔｒ（２）３１２、Ｔｒ（３）３１３の各ソース
は接地され、Ｔｒ３１１、Ｔｒ３１４、Ｔｒ３１５の各
ゲートはそれぞれ制御部３１６の端子Ａ、Ｂ、Ｃへ接続
されている。ＬＥＤ３１〜３５の電源は電池パック３１
７の電圧が使用され、電圧モニタ２１８は電池パック３
１７の電圧を絶えずモニタし制御部３１６へ電圧を報告
している。The current limiting resistor (6) 312 and the current limiting resistor (7) 313 are respectively a drain of the Tr (2) 314,
Tr (3) 315 is connected to the drain of Tr (1) 3
11, the sources of Tr (2) 312 and Tr (3) 313 are grounded, and the gates of Tr 311, Tr 314 and Tr 315 are connected to terminals A, B and C of the control unit 316, respectively. The power source of the LEDs 31 to 35 is the battery pack 31
7, the voltage monitor 218 is connected to the battery pack 3
17 is constantly monitored and the voltage is reported to the control unit 316.
【００４７】図２のＬＥＤシングル駆動回路と異なるの
は、電流制限抵抗（６）３１２、電流制限抵抗（７）３
１３の抵抗値でシングルの場合と比べると５倍の電流が
流れるために、抵抗値を１／５にしている点である。こ
のようにすれば、ＬＥＤがパラレルに何個接続されても
対応は可能となる。The difference from the LED single drive circuit of FIG. 2 is that the current limiting resistor (6) 312 and the current limiting resistor (7) 3
In this case, the resistance value is reduced to 1/5 because a current five times as large as that in the case of the single resistance value 13 flows. In this way, it is possible to handle any number of LEDs connected in parallel.
【００４８】[0048]
【発明の効果】本発明は以上の如く構成され、作用する
ものであり、本発明によれば以下に示すような効果が得
られる。The present invention is constructed and operates as described above. According to the present invention, the following effects can be obtained.
【００４９】従来のＬＥＤ駆動回路では電池パック電圧
値によりＬＥＤの輝度が変化してしまっていたが、本発
明により電池パック電圧値が変化してもＬＥＤの輝度を
ほぼ一定に保つことが可能となる。In the conventional LED driving circuit, the brightness of the LED changes depending on the battery pack voltage value. However, the present invention makes it possible to keep the LED brightness almost constant even when the battery pack voltage value changes. Become.
【図１】本発明による第１の実施の形態の基本的回路構
成を示す回路構成図である。FIG. 1 is a circuit configuration diagram showing a basic circuit configuration of a first embodiment according to the present invention.
【図２】本発明による第１の実施の形態の一実施例を示
す回路構成図である。FIG. 2 is a circuit configuration diagram showing an example of the first embodiment according to the present invention.
【図３】本発明による第２の実施の形態の一実施例を示
す回路構成図である。FIG. 3 is a circuit diagram showing an example of the second embodiment according to the present invention.
【図４】本発明に適用される一般的な携帯電話・ＰＨＳ
を示すブロック図である。FIG. 4 is a general mobile phone / PHS applied to the present invention.
FIG.
【図５】従来技術によるＬＥＤ駆動回路の回路図であ
る。FIG. 5 is a circuit diagram of an LED driving circuit according to the related art.
１１…電源電圧（電池パック） １２…ＬＥＤ １３…電流制限抵抗１ １４…Ｔｒ１ １５…電流制限抵抗２ １６…電流制限抵抗３ １７…Ｔｒ２ １８…Ｔｒ３ １９…制御部 １１０…電圧モニタ DESCRIPTION OF SYMBOLS 11 ... Power supply voltage (battery pack) 12 ... LED 13 ... Current limiting resistor 1 14 ... Tr1 15 ... Current limiting resistor 2 16 ... Current limiting resistor 3 17 ... Tr2 18 ... Tr3 19 ... Control unit 110 ... Voltage monitor
Claims (6)
て、前記ＬＥＤの電流を制限する第１の電流制限回路
と、該第１の電流制限回路に直列に接続された複数の第
２の電流制限回路と、該第２の電流制限回路の“ＯＮ／
ＯＦＦ”を制御する制御手段とを有し、前記第２の電流
制限回路の組み合わせと、前記第１の電流制限回路の組
み合わせにより前記ＬＥＤに流れる電流を一定に保つこ
とを特徴としたＬＥＤ駆動回路。1. A portable terminal device having an LED, a first current limiting circuit for limiting a current of the LED, and a plurality of second current limiting circuits connected in series to the first current limiting circuit. And "ON / ON" of the second current limiting circuit.
An LED drive circuit having control means for controlling "OFF", wherein a current flowing through the LED is kept constant by a combination of the second current limiting circuit and a combination of the first current limiting circuit. .
限抵抗を有し、前記ＬＥＤは該第１の電流制限抵抗に直
列に接続されていることを更に特徴とする請求項１に記
載のＬＥＤ駆動回路。2. The method of claim 1, wherein the first current limiting circuit has a first current limiting resistor, and wherein the LED is connected in series with the first current limiting resistor. The LED driving circuit as described in the above.
ンジスタと、第２の電流制限抵抗と第２のトランジスタ
の直列回路と、第３の電流制限抵抗と第３のトランジス
タの直列回路とが並列に接続されて構成されたことを更
に特徴とする請求項１または２のいずれか一項に記載の
ＬＥＤ駆動回路。3. The second current limiting circuit includes a first transistor, a series circuit of a second current limiting resistor and a second transistor, and a series circuit of a third current limiting resistor and a third transistor. 3. The LED driving circuit according to claim 1, wherein the LED driving circuit is configured to be connected in parallel.
ことを更に特徴とする請求項１に記載のＬＥＤ駆動回
路。4. The LED driving circuit according to claim 1, further comprising a plurality of said first current limiting circuits.
ニタして前記制御手段に報告する電圧モニタを有し、前
記制御手段は、前記電圧モニタより供給される電圧値を
基にして前記第２の電流制限回路を制御することを更に
特徴とする請求項１または３のいずれか一項に記載のＬ
ＥＤ駆動回路。5. A voltage monitor for continuously monitoring a voltage supplied to the LED and reporting the voltage to the control means, wherein the control means controls the second voltage based on a voltage value supplied from the voltage monitor. 4. The current limiting circuit according to claim 1, further comprising:
ED drive circuit.
て使用することを更に特徴とする請求項１〜５のいずれ
か一項に記載のＬＥＤ駆動回路。6. The LED driving circuit according to claim 1, wherein the LED is used as a backlight of an LCD.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2000386273A JP2002190392A (en) | 2000-12-20 | 2000-12-20 | Led drive circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2000386273A JP2002190392A (en) | 2000-12-20 | 2000-12-20 | Led drive circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JP2002190392A true JP2002190392A (en) | 2002-07-05 |
Family
ID=18853394
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2000386273A Pending JP2002190392A (en) | 2000-12-20 | 2000-12-20 | Led drive circuit |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2002190392A (en) |
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2005302712A (en) * | 2004-03-19 | 2005-10-27 | Citizen Watch Co Ltd | Led driving circuit and liquid crystal device using it |
| US7391407B2 (en) | 2003-11-27 | 2008-06-24 | Samsung Sdi Co., Ltd. | Back-light driving circuit in field sequential liquid crystal display |
| JP2008524790A (en) * | 2004-12-20 | 2008-07-10 | ヘイズ，スティーブン・ブライス | Lighting apparatus and method |
| JP2010171199A (en) * | 2009-01-22 | 2010-08-05 | Panasonic Electric Works Co Ltd | Light emitting diode driving device and lighting instrument using the same, in-cabin lighting device, and lighting device for vehicle |
| JP2011049050A (en) * | 2009-08-27 | 2011-03-10 | Kyocera Corp | Lighting control device, and mobile phone |
| WO2013051658A1 (en) * | 2011-10-04 | 2013-04-11 | シチズンホールディングス株式会社 | Led illumination device |
| WO2013155736A1 (en) * | 2012-04-16 | 2013-10-24 | 深圳市华星光电技术有限公司 | Drive circuit of backlight module and display device using same |
| WO2014126258A1 (en) * | 2013-02-18 | 2014-08-21 | シチズンホールディングス株式会社 | Led drive circuit |
| KR101508006B1 (en) * | 2013-04-05 | 2015-04-06 | 주식회사 씨티에스 | Light emitting diode type hybrid power package module |
| US9030459B2 (en) | 2011-04-06 | 2015-05-12 | Samsung Display Co., Ltd. | Back light unit and display device including the same |
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2000
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Cited By (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7391407B2 (en) | 2003-11-27 | 2008-06-24 | Samsung Sdi Co., Ltd. | Back-light driving circuit in field sequential liquid crystal display |
| JP2005302712A (en) * | 2004-03-19 | 2005-10-27 | Citizen Watch Co Ltd | Led driving circuit and liquid crystal device using it |
| JP2008524790A (en) * | 2004-12-20 | 2008-07-10 | ヘイズ，スティーブン・ブライス | Lighting apparatus and method |
| JP2010171199A (en) * | 2009-01-22 | 2010-08-05 | Panasonic Electric Works Co Ltd | Light emitting diode driving device and lighting instrument using the same, in-cabin lighting device, and lighting device for vehicle |
| JP2011049050A (en) * | 2009-08-27 | 2011-03-10 | Kyocera Corp | Lighting control device, and mobile phone |
| US9030459B2 (en) | 2011-04-06 | 2015-05-12 | Samsung Display Co., Ltd. | Back light unit and display device including the same |
| WO2013051658A1 (en) * | 2011-10-04 | 2013-04-11 | シチズンホールディングス株式会社 | Led illumination device |
| US9380657B2 (en) | 2011-10-04 | 2016-06-28 | Citizen Holdings Co., Ltd. | LED lighting device |
| US20140361695A1 (en) * | 2011-10-04 | 2014-12-11 | Citizen Electronics Co., Ltd. | Led lighting device |
| WO2013155736A1 (en) * | 2012-04-16 | 2013-10-24 | 深圳市华星光电技术有限公司 | Drive circuit of backlight module and display device using same |
| US9277615B2 (en) | 2013-02-18 | 2016-03-01 | Citizen Holdings Co., Ltd. | LED drive circuit |
| WO2014126258A1 (en) * | 2013-02-18 | 2014-08-21 | シチズンホールディングス株式会社 | Led drive circuit |
| JPWO2014126258A1 (en) * | 2013-02-18 | 2017-02-02 | シチズン時計株式会社 | LED drive circuit |
| KR101508006B1 (en) * | 2013-04-05 | 2015-04-06 | 주식회사 씨티에스 | Light emitting diode type hybrid power package module |
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