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JP2012010269A - Visual light communication transmitter - Google Patents

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JP2012010269A
JP2012010269A JP2010146478A JP2010146478A JP2012010269A JP 2012010269 A JP2012010269 A JP 2012010269A JP 2010146478 A JP2010146478 A JP 2010146478A JP 2010146478 A JP2010146478 A JP 2010146478A JP 2012010269 A JP2012010269 A JP 2012010269A
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circuit
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signal
visible light
light source
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JP5635312B2 (en
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Hiroyuki Kurokawa
裕之 黒川
Koji Kito
浩二 木藤
Fuminori Yui
史典 油井
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Outstanding Technology Co Ltd
Kaga Electronics Co Ltd
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Kaga Electronics Co Ltd
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Abstract

【課題】高速大容量の可視光通信を行うことができるバックライト装置を用いた可視光通信送信機を提供する。
【解決手段】可視光通信送信機は、ディスプレイのバックライト装置として使用されるＬＥＤ光源１を用いて可視光通信を行なうバックライト装置を用いた可視光通信送信機である。多数のＬＥＤ７を並列及び直列に接続したＬＥＤ光源１と、ＬＥＤ光源１に直流電力を供給するＬＥＤ駆動回路２と、ＬＥＤ光源１とＬＥＤ駆動回路２との間に接続される変調信号重畳回路３と、を備える。変調信号重畳回路３には、トランス１０がその二次側をＬＥＤ光源１とＬＥＤ駆動回路２間に直列して設けられ、トランス１０の二次側の入力側とグランド間にコンデンサ１１が接続される。トランス１０の一次側には、送信情報信号により搬送波を変調してなる高周波信号を供給する変調信号回路６が接続される。
【選択図】図１A visible light communication transmitter using a backlight device capable of high-speed and large-capacity visible light communication is provided.
A visible light communication transmitter is a visible light communication transmitter using a backlight device that performs visible light communication using an LED light source 1 used as a backlight device of a display. An LED light source 1 in which a large number of LEDs 7 are connected in parallel and in series, an LED drive circuit 2 for supplying DC power to the LED light source 1, and a modulation signal superimposing circuit 3 connected between the LED light source 1 and the LED drive circuit 2 And comprising. In the modulation signal superimposing circuit 3, a transformer 10 is provided with a secondary side in series between the LED light source 1 and the LED driving circuit 2, and a capacitor 11 is connected between the secondary side input side of the transformer 10 and the ground. The The primary side of the transformer 10 is connected to a modulation signal circuit 6 that supplies a high-frequency signal obtained by modulating a carrier wave with a transmission information signal.
[Selection] Figure 1

Description

本発明は、ディスプレイに用いられるバックライト装置のＬＥＤ光源を使用して、高速の可視光通信を行うことができる可視光通信送信機に関するものである。 The present invention relates to a visible light communication transmitter capable of performing high-speed visible light communication using an LED light source of a backlight device used for a display.

液晶テレビ等のディスプレイに用いられるバックライト装置は、従来、冷陰極管が通常使用され、インバータ回路により高電圧を発生させ、高電圧で冷陰極管を点灯駆動してバックライトを照射している。   Conventionally, a backlight device used for a display such as a liquid crystal television has conventionally used a cold cathode tube, generates a high voltage by an inverter circuit, and illuminates the backlight by driving the cold cathode tube at a high voltage. .

近年、冷陰極管を用いたバックライト装置に比べ、薄型化が可能で、駆動電圧が低く、低電力での駆動が可能で、より高輝度のバックライトを行なうことができる、ＬＥＤを用いたバックライト装置が、液晶ディスプレイなどで採用されつつある。   In recent years, LEDs have been used that can be made thinner, have a lower driving voltage, can be driven with lower power, and can perform higher-brightness backlighting, compared to backlight devices that use cold-cathode tubes. Backlight devices are being adopted in liquid crystal displays and the like.

ＬＥＤは、通常、直流により駆動され、連続光を発光するが、ＦＥＴなどのスイッチング素子によりパルス状に点灯駆動した場合、非常に高い高速応答性を示し、高周波の変調光を照射することができる。   An LED is usually driven by direct current and emits continuous light. However, when it is lit and driven in a pulsed manner by a switching element such as an FET, it exhibits a very high speed response and can emit high-frequency modulated light. .

そこで、従来、ＬＥＤを用いたバックライト装置を使用して、データ信号を高周波信号により変調した変調信号を、可視光のバックライトに重畳させて送信し、受信機側の受光素子でその可視光を受光し、受光信号に重畳されたデータ信号を復調して、可視光通信を行なう可視光通信送信機が、下記特許文献１で提案されている。   Therefore, conventionally, using a backlight device using an LED, a modulated signal obtained by modulating a data signal with a high-frequency signal is transmitted by being superimposed on a visible light backlight, and the visible light is received by a light receiving element on the receiver side. Patent Document 1 below proposes a visible light communication transmitter that receives visible light, demodulates a data signal superimposed on the received light signal, and performs visible light communication.

特開２００７-４３７０６号公報JP 2007-43706 A

この従来の可視光通信送信機は、バックライト装置のＬＥＤがＬＥＤドライバにより点灯駆動されるが、ＬＥＤドライバは、通常、ＬＥＤを直流駆動するための直流電源回路として構成され、ＬＥＤドライバ回路内にコンデンサ、コイルが使用されるため、データ信号を高周波信号により変調した変調信号をＬＥＤドライバに印加する送信機では、静電容量、リアクタンスなどの影響により、ＬＥＤに高周波電流を流して高速動作させることが困難となる。このため、従来のディスプレイのＬＥＤバックライト装置を使用する可視光通信送信機では、可視光通信の通信速度が制限され、高速大容量の通信を行うことができないという課題があった。   In this conventional visible light communication transmitter, the LED of the backlight device is driven to be lit by an LED driver. The LED driver is usually configured as a DC power supply circuit for DC driving of the LED, and the LED driver circuit includes Since a capacitor and coil are used, a transmitter that applies a modulation signal obtained by modulating a data signal with a high-frequency signal to the LED driver must be operated at high speed by flowing a high-frequency current to the LED due to the influence of capacitance, reactance, etc. It becomes difficult. For this reason, the visible light communication transmitter using the LED backlight device of the conventional display has a problem that the communication speed of visible light communication is limited and high-speed and large-capacity communication cannot be performed.

本発明は、上記の点にかんがみ、高速大容量の可視光通信を行うことができるバックライト装置を用いた可視光通信送信機を提供することを目的とする。   In view of the above points, an object of the present invention is to provide a visible light communication transmitter using a backlight device capable of performing high-speed and large-capacity visible light communication.

本発明の請求項１のバックライト装置を用いた可視光通信送信機は、ディスプレイのバックライト装置として使用されるＬＥＤ光源を用いて可視光通信を行なう可視光通信送信機において、
多数のＬＥＤを並列及び直列に接続したＬＥＤ光源と、
該ＬＥＤ光源に直流電力を供給するＬＥＤ駆動回路と、
該ＬＥＤ光源と該ＬＥＤ駆動回路との間に接続される変調信号重畳回路と、
を備え、該変調信号重畳回路には、トランスがその二次側を該ＬＥＤ光源と該ＬＥＤ駆動回路間に直列に接続して設けられ、該トランスの二次側の入力側とグランド間にコンデンサが接続され、該トランスの一次側には、送信情報信号により搬送波を変調した高周波信号を供給する変調信号回路が接続されたことを特徴とする。 The visible light communication transmitter using the backlight device according to claim 1 of the present invention is a visible light communication transmitter that performs visible light communication using an LED light source used as a backlight device of a display.
An LED light source in which a large number of LEDs are connected in parallel and in series;
An LED drive circuit for supplying DC power to the LED light source;
A modulation signal superimposing circuit connected between the LED light source and the LED driving circuit;
The modulation signal superimposing circuit includes a transformer having a secondary side connected in series between the LED light source and the LED driving circuit, and a capacitor between the input side of the secondary side of the transformer and the ground. And a modulation signal circuit for supplying a high frequency signal obtained by modulating a carrier wave with a transmission information signal is connected to the primary side of the transformer.

この発明によれば、変調信号回路が接続された変調信号重畳回路を、ＬＥＤ光源とＬＥＤ駆動回路との間に接続し、その変調信号重畳回路を通してＬＥＤに変調信号を供給するので、直流電源であるＬＥＤ駆動回路のコンデンサやコイルの影響を受けずに、ＬＥＤに高周波信号を印加して、ＬＥＤから照射される可視光に送信情報信号を重畳して、高速大容量の可視光通信を行うことができる。   According to the present invention, the modulation signal superimposing circuit to which the modulation signal circuit is connected is connected between the LED light source and the LED driving circuit, and the modulation signal is supplied to the LED through the modulation signal superimposing circuit. A high-speed, high-capacity visible light communication is performed by applying a high-frequency signal to an LED and superimposing a transmission information signal on the visible light emitted from the LED without being affected by a capacitor or coil of an LED drive circuit. Can do.

また、請求項２の発明は、上記請求項１の可視光通信送信機において、上記ＬＥＤ駆動回路には直流電力調整用のチョッパ回路が設けれ、上記ＬＥＤ光源のＬＥＤのカソード側に接続された電流検出用抵抗器の検出信号に基づき、該チョッパ回路を動作させて直流電力を一定に調整することを特徴とする。   According to a second aspect of the present invention, in the visible light communication transmitter according to the first aspect, a DC power adjustment chopper circuit is provided in the LED drive circuit and connected to the cathode side of the LED of the LED light source. Based on the detection signal of the current detection resistor, the chopper circuit is operated to adjust the DC power to be constant.

この発明によれば、ＬＥＤの電流が変化したとき、その変化を打ち消すようにチョッパ回路が動作して、ＬＥＤの発光を安定化させることができる。   According to the present invention, when the current of the LED changes, the chopper circuit operates so as to cancel the change, and the light emission of the LED can be stabilized.

また、請求項３の発明は、上記請求項１の可視光通信送信機において、上記ＬＥＤ駆動回路に、オンオフ期間のデューティ比を変えてバックライトの調光を行なう調光回路が接続され、該調光回路に入力される調光信号を上記変調信号回路に入力し、該調光信号のオフ期間には該変調信号回路からの変調信号の出力を停止し、該調光信号のオン期間にのみ変調信号をＬＥＤ電流に重畳することを特徴とする。   According to a third aspect of the present invention, in the visible light communication transmitter according to the first aspect, a dimming circuit for dimming a backlight by changing a duty ratio of an on / off period is connected to the LED driving circuit. The dimming signal input to the dimming circuit is input to the modulation signal circuit, the modulation signal output from the modulation signal circuit is stopped during the off period of the dimming signal, and the dimming signal is turned on. Only the modulation signal is superimposed on the LED current.

この発明によれば、調光回路を備えたバックライト装置で、ＬＥＤ電流のオンオフ期間のデューティ比を調整してバックライトの調光を行なう場合、調光信号のオン期間のみ、変調信号がＬＥＤ電流に重畳されるので、ＬＥＤ電流のオフ期間の影響による送信情報信号の部分的な消失がなく、調光信号により調光を行なう場合でも、可視光通信を正常に行うことができる。   According to the present invention, in a backlight device having a dimming circuit, when the backlight is dimmed by adjusting the duty ratio of the on / off period of the LED current, the modulation signal is LED only during the on period of the dimming signal. Since it is superimposed on the current, there is no partial disappearance of the transmission information signal due to the influence of the off-period of the LED current, and visible light communication can be normally performed even when light control is performed using the light control signal.

本発明のバックライト装置を用いた可視光通信送信機によれば、高速大容量の可視光通信を良好に行うことができる。   According to the visible light communication transmitter using the backlight device of the present invention, high-speed and large-capacity visible light communication can be performed satisfactorily.

本発明の可視光通信送信機の第１実施形態を示すブロック図である。It is a block diagram which shows 1st Embodiment of the visible light communication transmitter of this invention. 同可視光通信送信機の回路図である。It is a circuit diagram of the visible light communication transmitter. 本発明の可視光通信送信機の第２実施形態を示すブロック図である。It is a block diagram which shows 2nd Embodiment of the visible light communication transmitter of this invention. 同可視光通信送信機の回路図である。It is a circuit diagram of the visible light communication transmitter. 調光信号、ＬＥＤ電流などのタイミングチャートである。It is a timing chart, such as a light control signal and LED current.

以下、本発明の第１実施形態の可視光通信送信機の具体例を、図面に基づき説明する。図１は可視光通信送信機の第１実施形態を示すブロック図、図２は同可視光通信送信機の回路図を示している。この可視光通信送信機は、ディスプレイのバックライト装置として使用されるＬＥＤ光源１を用いて可視光通信を行なう可視光通信送信機であり、多数のＬＥＤ７を並列及び直列に接続したＬＥＤ光源１と、ＬＥＤ光源１に直流電力を供給するＬＥＤ駆動回路２と、ＬＥＤ光源１とＬＥＤ駆動回路２との間に接続される変調信号重畳回路３と、を備えて構成される。   Hereinafter, specific examples of the visible light communication transmitter according to the first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a first embodiment of a visible light communication transmitter, and FIG. 2 shows a circuit diagram of the visible light communication transmitter. This visible light communication transmitter is a visible light communication transmitter that performs visible light communication using an LED light source 1 used as a backlight device of a display, and an LED light source 1 in which a large number of LEDs 7 are connected in parallel and in series. The LED drive circuit 2 that supplies DC power to the LED light source 1 and the modulation signal superimposing circuit 3 connected between the LED light source 1 and the LED drive circuit 2 are configured.

ＬＥＤ光源１は、液晶ディスプレイなどのバックライト装置として使用される光源であり、図２のように、多数のＬＥＤ７を並列及び直列に接続して構成され、各列の複数のＬＥＤ７は直列に接続され、各列のＬＥＤ７のアノード側は変調信号重畳回路３を介して直流電源に接続され、各列のＬＥＤ７のカソード側は、電流検出用抵抗器１５を介してグランドに接続される。電流検出用抵抗器１５により、各列のＬＥＤ７を流れる電流を検出し、その検出信号をＬＥＤ駆動回路２のチョッパ回路２０に送るようになっている。各列のＬＥＤ７は複数本が並列接続され、全体で液晶ディスプレイなどのバックライト装置の光源を構成している。   The LED light source 1 is a light source used as a backlight device such as a liquid crystal display, and is configured by connecting a large number of LEDs 7 in parallel and in series as shown in FIG. 2, and a plurality of LEDs 7 in each column are connected in series. The anode side of the LED 7 in each column is connected to a DC power source via the modulation signal superimposing circuit 3, and the cathode side of the LED 7 in each column is connected to the ground via a current detection resistor 15. The current detection resistor 15 detects the current flowing through the LEDs 7 in each column, and sends the detection signal to the chopper circuit 20 of the LED drive circuit 2. A plurality of LEDs 7 in each row are connected in parallel, and constitute a light source of a backlight device such as a liquid crystal display as a whole.

ＬＥＤ駆動回路２は、ＬＥＤ光源１に直流電流を安定供給する昇圧または降圧用のチョッパ回路２０を備えて構成され、図２に示すように、直流電源２７に対しコイル２２、ダイオード２３、及びコイル２４が直列に接続され、コイル２２とダイオード２３間にトランジスタ（ＣＭＯＳ−ＦＥＴ）２６が接続される。トランジスタ２６はチョッパ用のスイッチング素子となるもので、そのゲートには、ＰＷＭ制御回路２１が接続され、そのドレインはコイル２２とダイオード２３間に接続され、そのソースはグランドに接続される。コイル２２はトランジスタ２６のスイッチング動作時に電流を保持して電圧を発生させるために接続され、コイル２４は高周波ノイズを除去するために接続され、ダイオード２３は逆流防止用である。ダイオード２３とコイル２４間に平滑用のコンデンサ２５がグランドとの間に接続される。   The LED drive circuit 2 includes a step-up or step-down chopper circuit 20 that stably supplies a direct current to the LED light source 1, and, as shown in FIG. 24 is connected in series, and a transistor (CMOS-FET) 26 is connected between the coil 22 and the diode 23. The transistor 26 serves as a switching element for a chopper, the PWM control circuit 21 is connected to the gate, the drain is connected between the coil 22 and the diode 23, and the source is connected to the ground. The coil 22 is connected to generate a voltage by holding a current during the switching operation of the transistor 26, the coil 24 is connected to remove high frequency noise, and the diode 23 is used for preventing backflow. A smoothing capacitor 25 is connected between the diode 23 and the coil 24 between the ground.

ＰＷＭ制御回路２１は、図２に示すように、各電流検出用抵抗器１５に流れる電流を電圧信号として入力し、その電流値（電圧値）に基づき、トランジスタ２６のスイッチング間隔を変えて、出力されるパルス幅のデューティ比を調整し、ＬＥＤ７に流れる電流を一定にして、ＬＥＤ７の動作の安定化を図るように構成される。   As shown in FIG. 2, the PWM control circuit 21 inputs the current flowing through each current detection resistor 15 as a voltage signal, changes the switching interval of the transistor 26 based on the current value (voltage value), and outputs it. The operation of the LED 7 is stabilized by adjusting the duty ratio of the pulse width to make the current flowing through the LED 7 constant.

ＬＥＤ駆動回路２の出力側は、図２の如く、変調信号重畳回路３を介してＬＥＤ光源１が接続される。つまり、ＬＥＤ駆動回路２とＬＥＤ光源１との間に、変調信号重畳回路３が接続される。この変調信号重畳回路３は、変調信号回路６から送られる変調信号、つまり高周波の搬送波を、送信しようとする送信情報信号により変調した変調信号を、ＬＥＤ駆動用の直流電流に重畳する回路であり、トランス１０とコンデンサ１１とから構成される。   The LED light source 1 is connected to the output side of the LED drive circuit 2 via a modulation signal superimposing circuit 3 as shown in FIG. That is, the modulation signal superimposing circuit 3 is connected between the LED driving circuit 2 and the LED light source 1. The modulation signal superimposing circuit 3 is a circuit that superimposes a modulation signal transmitted from the modulation signal circuit 6, that is, a modulation signal obtained by modulating a high-frequency carrier wave with a transmission information signal to be transmitted, on a direct current for LED driving. , A transformer 10 and a capacitor 11.

変調信号重畳回路３のトランス１０は、その一次側の一端が変調信号回路６の出力側に接続され、トランス１０の一次側の他端はグランド接続される。トランス１０の二次側はＬＥＤ駆動回路２の出力側とＬＥＤ光源１の入力側つまり、各ＬＥＤ７の各列のアノード側に接続されている。トランス１０の二次側の入力側に、高周波電流の逆流を阻止するためのコンデンサ１１がグランド間に接続されている。この変調信号重畳回路３の動作により、送信しようとする送信情報信号により変調した変調信号が、ＬＥＤ駆動回路２からの直流電流に重畳され、ＬＥＤ光源１に出力されるようになっている。   The transformer 10 of the modulation signal superimposing circuit 3 has one end on the primary side connected to the output side of the modulation signal circuit 6 and the other end on the primary side of the transformer 10 connected to the ground. The secondary side of the transformer 10 is connected to the output side of the LED drive circuit 2 and the input side of the LED light source 1, that is, the anode side of each column of each LED 7. A capacitor 11 for preventing a reverse flow of the high-frequency current is connected between the ground and the secondary input side of the transformer 10. By the operation of the modulation signal superimposing circuit 3, the modulation signal modulated by the transmission information signal to be transmitted is superimposed on the direct current from the LED drive circuit 2 and output to the LED light source 1.

図２に示すように、変調信号回路６は、変調回路４とアンプ５とから構成される。変調回路４は、例えば高周波（数ＭＨｚ〜数十ＭＨｚ）の三角波搬送信号を発振する三角波発振回路とＰＷＭ変調回路とから構成され、ＰＷＭ変調回路は、送信しようとするアナログの送信情報信号と三角波搬送信号を入力し、高周波の三角波搬送信号を送信情報信号により変調し、変調信号として出力するように構成される。   As shown in FIG. 2, the modulation signal circuit 6 includes a modulation circuit 4 and an amplifier 5. The modulation circuit 4 is composed of, for example, a triangular wave oscillation circuit that oscillates a high frequency (several MHz to several tens of MHz) triangular wave carrier signal and a PWM modulation circuit. The PWM modulation circuit is an analog transmission information signal to be transmitted and a triangular wave. A carrier signal is input, and a high-frequency triangular wave carrier signal is modulated by a transmission information signal and output as a modulated signal.

変調回路４から出力された変調信号はリニアに増幅するアンプ５により増幅され、変調信号重畳回路３に送られ、トランス１０を通して変調信号がＬＥＤ駆動回路２からの直流電流に重畳されるようになっている。このとき、変調信号重畳回路３のコンデンサ１１は、変調信号がＬＥＤ駆動回路２側に流れ込まないように作用する。   The modulation signal output from the modulation circuit 4 is amplified by an amplifier 5 that linearly amplifies and is sent to the modulation signal superimposing circuit 3, and the modulation signal is superimposed on the direct current from the LED driving circuit 2 through the transformer 10. ing. At this time, the capacitor 11 of the modulation signal superimposing circuit 3 acts so that the modulation signal does not flow into the LED drive circuit 2 side.

次に、上記構成のバックライト装置を用いた可視光通信送信機の動作を説明すると、ディスプレイのバックライト装置が点灯動作する通常時には、ＬＥＤ駆動回路２からＬＥＤ光源１に直流電流が供給され、ＬＥＤ光源１の各ＬＥＤ７は直流電流により点灯駆動され、発光する。   Next, the operation of the visible light communication transmitter using the backlight device having the above configuration will be described. During normal operation when the backlight device of the display is turned on, a direct current is supplied from the LED drive circuit 2 to the LED light source 1, Each LED 7 of the LED light source 1 is driven to be lit by a direct current and emits light.

このとき、電流検出用抵抗器１５で検出された、各列のＬＥＤ７を流れる電流の検出信号がＬＥＤ駆動回路２のチョッパ回路２０に入力され、チョッパ回路２０のＰＷＭ制御回路２１は、検出信号の電圧値に基づき、トランジスタ２６のスイッチング間隔を変えて、出力されるパルス幅のデューティ比を調整し、ＬＥＤ７に流れる電流を一定にするように、電流制御が行なわれ、照射光の安定化が図られる。   At this time, the detection signal of the current flowing through the LEDs 7 in each column detected by the current detection resistor 15 is input to the chopper circuit 20 of the LED drive circuit 2, and the PWM control circuit 21 of the chopper circuit 20 detects the detection signal. Based on the voltage value, the switching interval of the transistor 26 is changed, the duty ratio of the output pulse width is adjusted, and current control is performed so that the current flowing through the LED 7 is constant, so that the irradiation light is stabilized. It is done.

一方、音声信号或いは各種データ信号などの送信情報信号を、可視光通信送信機から送信する場合、送信情報信号を変調回路４に入力する。変調回路４では、内蔵されるＰＷＭ変調回路が、送信しようとする送信情報信号と、例えば三角波発振回路から出力される数ＭＨｚ〜数十ＭＨｚの高周波の三角波搬送信号を入力して、この三角波搬送信号を送信情報信号により変調し、変調信号として出力する。   On the other hand, when transmitting a transmission information signal such as an audio signal or various data signals from the visible light communication transmitter, the transmission information signal is input to the modulation circuit 4. In the modulation circuit 4, the built-in PWM modulation circuit inputs a transmission information signal to be transmitted and a high-frequency triangular wave carrier signal of, for example, several MHz to several tens of MHz output from the triangular wave oscillation circuit, and this triangular wave carrier The signal is modulated by the transmission information signal and output as a modulated signal.

変調信号はアンプ５で増幅された後、変調信号重畳回路３のトランス１０に入力され、これにより、トランス１０の二次側を流れる直流駆動電流に変調信号が重畳され、ＬＥＤ光源１の各ＬＥＤ７に供給される。このとき、変調信号は、ＬＥＤ駆動回路２とＬＥＤ光源１の間に接続された変調信号重畳回路３のトランス１０を通して、直流電流に重畳されるので、変調信号が数ＭＨｚ〜数十ＭＨｚの高周波信号であっても、ＬＥＤ駆動回路２のコンデンサの静電容量やコイルのインダクタンスの影響を受けず、正常に変調信号を重畳した直流駆動電流がＬＥＤ光源１の各ＬＥＤ７に供給され、ＬＥＤ光源１からは変調信号を重畳した可視光が照射される。そして、図示しない可視光通信受信機の受光器で、照射された可視光が受光され、その受光信号に含まれる情報信号が復調されて取り出される。   The modulation signal is amplified by the amplifier 5 and then input to the transformer 10 of the modulation signal superimposing circuit 3, whereby the modulation signal is superimposed on the direct current drive current flowing on the secondary side of the transformer 10, and each LED 7 of the LED light source 1. To be supplied. At this time, since the modulation signal is superimposed on the direct current through the transformer 10 of the modulation signal superimposing circuit 3 connected between the LED driving circuit 2 and the LED light source 1, the modulation signal has a high frequency of several MHz to several tens of MHz. Even if it is a signal, it is not affected by the capacitance of the capacitor of the LED drive circuit 2 or the inductance of the coil, and a DC drive current on which the modulation signal is normally superimposed is supplied to each LED 7 of the LED light source 1. Is irradiated with visible light on which a modulation signal is superimposed. Then, the irradiated visible light is received by a light receiver of a visible light communication receiver (not shown), and an information signal included in the received light signal is demodulated and extracted.

このように、変調信号回路６が接続された変調信号重畳回路３を、ＬＥＤ光源１とＬＥＤ駆動回路２との間に接続し、その変調信号重畳回路３を通してＬＥＤ７に変調信号を供給するので、直流電源であるＬＥＤ駆動回路２のコンデンサやコイルの影響を受けずに、ＬＥＤ７に高周波信号を印加し、ＬＥＤ７から照射される可視光に送信情報信号を重畳して、高速大容量の可視光通信を行うことができる。   In this way, the modulation signal superimposing circuit 3 to which the modulation signal circuit 6 is connected is connected between the LED light source 1 and the LED driving circuit 2, and the modulation signal is supplied to the LED 7 through the modulation signal superimposing circuit 3. High-speed and large-capacity visible light communication by applying a high-frequency signal to the LED 7 without being affected by the capacitor or coil of the LED drive circuit 2 that is a DC power supply and superimposing a transmission information signal on the visible light emitted from the LED 7 It can be performed.

図３、４は第２実施形態の可視光通信送信機を示している。この可視光通信送信機は、上記構成の可視光通信送信機に使用されるバックライト装置が調光回路３０を備え、調光信号に応じてバックライトの輝度が調光され、調光されたＬＥＤ光源１の可視光を使用して可視光通信を行なうものである。なお、上記第１実施形態と同じ構成については、上記図１，２で使用した符号と同じ符号を図３，４に付して、その説明を省略する。   3 and 4 show the visible light communication transmitter of the second embodiment. In this visible light communication transmitter, the backlight device used in the visible light communication transmitter having the above-described configuration includes the dimming circuit 30, and the luminance of the backlight is dimmed according to the dimming signal. The visible light communication is performed using the visible light of the LED light source 1. In addition, about the same structure as the said 1st Embodiment, the code | symbol same as the code | symbol used in the said FIG. 1, 2 is attached | subjected to FIG.

図３，４に示すように、この可視光通信送信機に使用されるバックライト装置には、調光回路３０が設けられる。調光回路３０は、図４の如く、ＬＥＤ駆動回路２の前段に設けられ、直流電源２７の電源ラインに接続されるトランジスタ（ＣＭＯＳ−ＦＥＴ）３１、そのゲートに接続されるドライバ回路３３、及びコンデンサ３２を備えて構成される。トランジスタ３１は、そのドレインを直流電源２７側に接続し、そのソースを調光回路３０の出力としてＬＥＤ駆動回路２のコイル２２に接続し、トランジスタ３１のスイッチングにより制御された直流電流を、ＬＥＤ駆動回路２に流し、調光信号に応じた調光を行なうようになっている。   As shown in FIGS. 3 and 4, a dimming circuit 30 is provided in the backlight device used in the visible light communication transmitter. As shown in FIG. 4, the dimming circuit 30 is provided in the front stage of the LED drive circuit 2, a transistor (CMOS-FET) 31 connected to the power supply line of the DC power supply 27, a driver circuit 33 connected to the gate thereof, A capacitor 32 is provided. The transistor 31 has a drain connected to the DC power supply 27 side, a source connected to the coil 22 of the LED drive circuit 2 as an output of the dimming circuit 30, and a direct current controlled by switching of the transistor 31 is applied to the LED drive. The light is passed through the circuit 2 and light control according to the light control signal is performed.

ドライバ回路３３は、図示しない外部から送られる調光信号を入力し、その調光信号に基づき、オンオフのデューティ比を変化させるように、トランジスタ３１のスイッチングを制御する。これにより、直流電源２７から供給される直流電力は、調光信号に応じたデューティ比でトランジスタ３１によりスイッチングされて、調光信号により調整された直流電力がＬＥＤ駆動回路２に供給されるようになっている。   The driver circuit 33 inputs a dimming signal sent from outside (not shown), and controls the switching of the transistor 31 so as to change the on / off duty ratio based on the dimming signal. Thus, the DC power supplied from the DC power supply 27 is switched by the transistor 31 at a duty ratio corresponding to the dimming signal, and the DC power adjusted by the dimming signal is supplied to the LED drive circuit 2. It has become.

さらに、図４に示す如く、上記調光信号は調光回路３０と共に変調回路４にも入力される。変調回路４は、例えば高周波（数ＭＨｚ〜数十ＭＨｚ）の三角波搬送信号を発振する三角波発振回路とＰＷＭ変調回路とから構成され、ＰＷＭ変調回路は、送信しようとするアナログの送信情報信号と三角波搬送信号を入力し、高周波の三角波搬送信号を送信情報信号により変調し、変調信号として出力する。このとき、変調回路４は、図５に示すように、調光信号がオフの期間には、変調を停止し、調光信号がオンの期間にのみ、搬送信号を送信情報信号により変調し、変調信号として出力するように構成される。   Further, as shown in FIG. 4, the dimming signal is input to the modulation circuit 4 together with the dimming circuit 30. The modulation circuit 4 is composed of, for example, a triangular wave oscillation circuit that oscillates a high frequency (several MHz to several tens of MHz) triangular wave carrier signal and a PWM modulation circuit. The PWM modulation circuit is an analog transmission information signal to be transmitted and a triangular wave. A carrier signal is input, a high-frequency triangular wave carrier signal is modulated by a transmission information signal, and is output as a modulated signal. At this time, as shown in FIG. 5, the modulation circuit 4 stops the modulation when the dimming signal is off, and modulates the carrier signal with the transmission information signal only when the dimming signal is on. It is configured to output as a modulation signal.

次に、上記構成の可視光通信送信機の動作を説明する。ディスプレイのバックライト装置が点灯動作する通常時には、ＬＥＤ駆動回路２からＬＥＤ光源１に直流電流が供給され、ＬＥＤ光源１の各ＬＥＤ７は直流電流により点灯駆動され、発光する。   Next, the operation of the visible light communication transmitter configured as described above will be described. During normal operation when the backlight device of the display is lit, a direct current is supplied from the LED drive circuit 2 to the LED light source 1, and each LED 7 of the LED light source 1 is driven to light by the direct current and emits light.

このとき、電流検出用抵抗器１５で検出された、各列のＬＥＤ７を流れる電流の検出信号がＬＥＤ駆動回路２のチョッパ回路２０に入力され、チョッパ回路２０のＰＷＭ制御回路２１は、検出信号の電圧値に基づき、トランジスタ２６のスイッチング間隔を変えて、出力されるパルス幅のデューティ比を調整し、ＬＥＤ７に流れる電流を一定にするように、電流制御が行なわれ、照射光の安定化が図られる。   At this time, the detection signal of the current flowing through the LEDs 7 in each column detected by the current detection resistor 15 is input to the chopper circuit 20 of the LED drive circuit 2, and the PWM control circuit 21 of the chopper circuit 20 detects the detection signal. Based on the voltage value, the switching interval of the transistor 26 is changed, the duty ratio of the output pulse width is adjusted, and current control is performed so that the current flowing through the LED 7 is constant, so that the irradiation light is stabilized. It is done.

一方、外部から調光信号が調光回路３０に入力されると、調光回路３０のドライバ回路３３は、その調光信号に応じて、オンオフのデューティ比を変化させるように、トランジスタ３１のスイッチングを制御する。これにより、直流電源２７から供給される直流電力は、調光信号に応じたデューティ比でトランジスタ３１によりスイッチングされ、直流電力が調整される。そして、調光信号により調整された直流電力は、ＬＥＤ駆動回路２に送られ、ＬＥＤ駆動回路２から調整された直流電流がＬＥＤ光源１に供給され、ＬＥＤ光源１の各ＬＥＤ７は調光された輝度で可視光を照射する。   On the other hand, when a dimming signal is input to the dimming circuit 30 from the outside, the driver circuit 33 of the dimming circuit 30 switches the transistor 31 so as to change the on / off duty ratio in accordance with the dimming signal. To control. Thereby, the DC power supplied from the DC power supply 27 is switched by the transistor 31 at a duty ratio corresponding to the dimming signal, and the DC power is adjusted. Then, the DC power adjusted by the dimming signal is sent to the LED drive circuit 2, the DC current adjusted from the LED drive circuit 2 is supplied to the LED light source 1, and each LED 7 of the LED light source 1 is dimmed. Irradiate visible light with brightness.

一方、各種データ信号などの送信情報信号を、可視光通信送信機から送信する場合、送信情報信号が変調回路４に入力され、変調回路４には、調光回路３０からの調光信号が送信情報信号と共に入力される。変調回路４は、内蔵されるＰＷＭ変調回路が、送信しようとする送信情報信号と、三角波発振回路から出力される数ＭＨｚ〜数十ＭＨｚの高周波の三角波搬送信号を入力して、この三角波搬送信号を送信情報信号により変調し、変調信号として出力するが、図５に示すように、調光信号がオフの期間には、変調を停止し、調光信号がオンの期間にのみ、搬送信号を送信情報信号により変調し、変調信号として出力する。   On the other hand, when a transmission information signal such as various data signals is transmitted from a visible light communication transmitter, the transmission information signal is input to the modulation circuit 4, and the dimming signal from the dimming circuit 30 is transmitted to the modulation circuit 4. It is input together with the information signal. The modulation circuit 4 inputs a transmission information signal to be transmitted by the built-in PWM modulation circuit and a high-frequency triangular wave carrier signal of several MHz to several tens of MHz output from the triangular wave oscillation circuit, and this triangular wave carrier signal 5 is modulated by the transmission information signal and output as a modulated signal. As shown in FIG. 5, the modulation is stopped during the period when the dimming signal is off, and the carrier signal is transmitted only during the period when the dimming signal is on. It modulates with a transmission information signal and outputs as a modulation signal.

変調信号はアンプ５で増幅された後、変調信号重畳回路３のトランス１０に入力され、これにより、トランス１０の二次側を流れる直流駆動電流に変調信号が重畳され、ＬＥＤ光源１の各ＬＥＤ７に供給される。このとき、変調信号は、ＬＥＤ駆動回路２とＬＥＤ光源１の間に接続された変調信号重畳回路３のトランス１０を通して、直流電流に重畳されるので、変調信号が数ＭＨｚ〜数十ＭＨｚの高周波信号であっても、ＬＥＤ駆動回路２のコンデンサの静電容量やコイルのインダクタンスの影響を受けず、正常に変調信号を重畳した直流駆動電流がＬＥＤ光源１の各ＬＥＤ７に供給され、ＬＥＤ光源１からは変調信号を重畳した可視光が照射される。   The modulation signal is amplified by the amplifier 5 and then input to the transformer 10 of the modulation signal superimposing circuit 3, whereby the modulation signal is superimposed on the direct current drive current flowing on the secondary side of the transformer 10, and each LED 7 of the LED light source 1. To be supplied. At this time, since the modulation signal is superimposed on the direct current through the transformer 10 of the modulation signal superimposing circuit 3 connected between the LED driving circuit 2 and the LED light source 1, the modulation signal has a high frequency of several MHz to several tens of MHz. Even if it is a signal, it is not affected by the capacitance of the capacitor of the LED drive circuit 2 or the inductance of the coil, and a DC drive current on which the modulation signal is normally superimposed is supplied to each LED 7 of the LED light source 1. Is irradiated with visible light on which a modulation signal is superimposed.

また、調光信号に応じて、ＬＥＤ電流のオンオフ期間のデューティ比を調整してバックライトの調光を行なう場合、図５に示すように、調光信号がオフの期間には、変調を停止し、調光信号がオンの期間にのみ、搬送信号を送信情報信号により変調し、変調信号として出力するので、ＬＥＤ電流のオフ期間の影響による送信情報信号の部分的な消失がなく、調光を行なう場合でも、可視光通信を正常に行うことができる。   In addition, when the backlight is dimmed by adjusting the duty ratio of the LED current on / off period according to the dimming signal, the modulation is stopped during the dimming signal off period, as shown in FIG. However, only when the dimming signal is on, the carrier signal is modulated by the transmission information signal and output as a modulation signal, so there is no partial disappearance of the transmission information signal due to the influence of the off-period of the LED current. Even in the case of performing visible light communication, visible light communication can be performed normally.

１ ＬＥＤ光源
２ ＬＥＤ駆動回路
３ 変調信号重畳回路
４ 変調回路
５ アンプ
６ 変調信号回路
７ ＬＥＤ
１０ トランス
１１ コンデンサ
１５ 電流検出用抵抗器
２０ チョッパ回路
２１ ＰＷＭ制御回路
２２ コイル
２３ ダイオード
２４ コイル
２５ コンデンサ
２６ トランジスタ
２７ 直流電源
３０ 調光回路
３１ トランジスタ
３２ コンデンサ
３３ ドライバ回路 DESCRIPTION OF SYMBOLS 1 LED light source 2 LED drive circuit 3 Modulation signal superimposition circuit 4 Modulation circuit 5 Amplifier 6 Modulation signal circuit 7 LED
DESCRIPTION OF SYMBOLS 10 Transformer 11 Capacitor 15 Current detection resistor 20 Chopper circuit 21 PWM control circuit 22 Coil 23 Diode 24 Coil 25 Capacitor 26 Transistor 27 DC power supply 30 Dimming circuit 31 Transistor 32 Capacitor 33 Driver circuit

Claims (3)

ディスプレイのバックライト装置として使用されるＬＥＤ光源を用いて可視光通信を行なう可視光通信送信機において、
多数のＬＥＤを並列及び直列に接続してなるＬＥＤ光源と、
該ＬＥＤ光源に直流電力を供給するＬＥＤ駆動回路と、
該ＬＥＤ光源と該ＬＥＤ駆動回路との間に接続される変調信号重畳回路と、
を備え、該変調信号重畳回路には、トランスがその二次側を該ＬＥＤ光源と該ＬＥＤ駆動回路間に直列接続して設けられ、該トランスの二次側の入力側とグランド間にコンデンサが接続され、該トランスの一次側には、送信情報信号により搬送波を変調した高周波信号を供給する変調信号回路が接続されることを特徴とする可視光通信送信機。 In a visible light communication transmitter that performs visible light communication using an LED light source used as a backlight device of a display,
An LED light source formed by connecting a large number of LEDs in parallel and in series;
An LED drive circuit for supplying DC power to the LED light source;
A modulation signal superimposing circuit connected between the LED light source and the LED driving circuit;
The modulation signal superimposing circuit includes a transformer having a secondary side connected in series between the LED light source and the LED driving circuit, and a capacitor between the secondary input side of the transformer and the ground. A visible light communication transmitter characterized in that a modulation signal circuit for supplying a high frequency signal obtained by modulating a carrier wave with a transmission information signal is connected to a primary side of the transformer. 前記ＬＥＤ駆動回路には直流電流調整用のチョッパ回路が設けられ、前記ＬＥＤ光源のＬＥＤのカソード側に接続された電流検出用抵抗器の検出信号に基づき、該チョッパ回路を動作させて直流電流を一定に調整することを特徴とする請求項１記載の可視光通信送信機。   The LED drive circuit is provided with a chopper circuit for adjusting a direct current, and the direct current is generated by operating the chopper circuit based on a detection signal of a current detection resistor connected to the cathode side of the LED of the LED light source. The visible light communication transmitter according to claim 1, wherein the visible light communication transmitter is adjusted to be constant. 前記ＬＥＤ駆動回路に、オンオフ期間のデューティ比を変えてバックライトの調光を行なう調光回路が接続され、該調光回路に入力される調光信号を前記変調信号回路に入力し、該調光信号のオフ期間には前記変調信号回路からの変調信号の出力を停止し、該調光信号のオン期間にのみ変調信号をＬＥＤ電流に重畳することを特徴とする請求項１記載の可視光通信送信機。   A dimming circuit for dimming a backlight by changing a duty ratio during an on / off period is connected to the LED drive circuit, and a dimming signal input to the dimming circuit is input to the modulation signal circuit. 2. The visible light according to claim 1, wherein the output of the modulation signal from the modulation signal circuit is stopped during the off period of the optical signal, and the modulation signal is superimposed on the LED current only during the on period of the dimming signal. Communication transmitter.
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