KR101083222B1 - Transmission device for visible light communication - Google Patents

Abstract

The present invention relates to an optical transmission device for visible light communication and a power control method for visible light.
More specifically, the optical transmission device includes a power conversion unit for supplying DC power to the LED lamp for illumination;
A driving unit driven by a switching driving method and supplying an operating current to the lighting LED lamp, and an encoder connected to an external network to receive and code data and supply the data to the driver, the power converter and the driver, and control the operation of the encoder. It includes a control unit. In addition, it may further include a detector for adjusting the brightness of the LED lamp for illumination.

Since the driving unit of the optical transmission device for visible light communication according to the present invention operates in a switching driving method, the power conversion efficiency and the element heating characteristic are very excellent. Moreover, high-speed data transmission is possible because the drive element can drive a high frequency switch. In addition, the power control method of the optical transmission device for visible light communication according to the present invention is very suitable as a lighting device because the brightness can be adjusted according to the user's command.

Description

Optical transmission device for visible light communication {TRANSMISSION DEVICE FOR VISIBLE LIGHT COMMUNICATION}

The present invention relates to an optical transmission device for visible light communication and a power control method for visible light using a plurality of LED lamps, and more particularly, to an optical transmission device and a power control method for visible light communication that enable high-speed data communication and provide high power conversion efficiency. will be.

Recently, the market for electronic products using LED lamps as a light source, which has various advantages such as fast response speed, long lifespan and mercury-free eco-friendliness, is growing rapidly. In addition, with the development of the electronic product market using LED lamps, the expectation of application of indoor wireless communication and near field wireless communication network using Visible Light Communication (VLC) system continues.

The visible light communication technology using LED lamp is the latest communication technology that combines digital LED lighting and communication, which is visible light, and variously wireless communication simply by adding communication function that modulates light to LED lamp lighting equipment. It means to build an environment that can provide services. As wired / wireless voice communication and Internet service are becoming more common, short-range wireless communication technology is being developed in various ways for improved information communication, and communication with lighting is possible by using LED lamp lighting equipment that emits visible light wavelength (380 ~ 780nm). Visible light communication technology is emerging.

 The method of driving the optical transmission device for visible light communication in the visible light communication is largely classified into a switching drive method and a linear drive method. The switching driving method is to drive the semiconductor device in the switching area, and it has the advantage of being very suitable for the large-capacity and high-brightness LED lamp driving circuit because of the excellent power conversion efficiency and the heat generation characteristics of the driving device, but when the switching driving method is applied to visible light communication It is difficult to implement high speed data communication. When the switching driving method is applied to visible light communication, it is difficult to implement high speed data communication. For example, if the switching frequency of the switching drive is about 100KHz, the LED conduction current change frequency tolerance is determined to be up to 50KHz. (Note: Nyquist rate theory of communication, the carrier frequency at signal modulation is the carrier frequency In the case of LED switching driver, the carrier frequency becomes the switching frequency, and the LED conduction current becomes the original signal frequency.) Digital data communication over 50Kbps (bit per second) is impossible. . Due to the slow dynamic characteristics of the switching driving method, the bandwidth is very small, such as several tens of kHz, for constant switching of the LED current, so that it is difficult to implement high-speed data communication over several MHz when applied to visible light communication. There has been no application of visible light communication device. Although the existing technology has a switching driving method that provides such a high power conversion efficiency, the above-mentioned disadvantages cannot be overcome, and thus the optical transmission device is used as the linear driving method.

The linear driving method has the advantage of implementing high-speed data communication by operating a driving device such as a switch in a linear region, but the current is applied to the LED lamp while the operating voltage is always applied to the driving device that sends the signal to the LED lamp. Because of the low power conversion efficiency and low heat generation characteristics of the driving device has a disadvantage that the manufacturing cost is high, and is not suitable for large capacity and high brightness driving circuit.

 In addition, in order to use the optical transmission device for visible light communication together for lighting, the brightness of the LED lamp must be adjustable. However, the switching driving method has a problem in outputting the desired brightness because it cannot control the peak value of the current flowing in the LED lamp. And reliability problems arise.

The present invention has been made to solve the above problems of the prior art, an object of the present invention is to provide an optical transmission device for visible light communication that implements high-speed data communication in the visible light communication.

 Another object of the present invention is to provide an optical transmission device for visible light communication having high power conversion efficiency by applying a switching driving method.

 In addition, another object of the present invention is to provide an optical transmission device for visible light communication having a low-cost high-capacity driving circuit excellent in power conversion efficiency and heat generation characteristics of the drive element, and the present invention is to improve the power conversion efficiency of the optical transmission device for visible light communication current social issues It is to provide an optical transmission device for visible light communication that contributes to energy saving.

Another object of the present invention is to provide a power control method of an optical transmission apparatus corresponding to the change when the threshold range voltage changes according to the brightness adjustment of the user when the LED lamp is used for illumination.

In order to achieve the above object, the optical transmission device for visible light communication according to the present invention includes a power conversion unit for supplying DC power to an LED lamp for lighting, a driving unit for driving a switching drive and supplying an operating current to the lighting lamp, and an external network. And a control unit for controlling the operation of the encoder, the power converter, the driver, and the encoder to receive and code data and supply the data to the driver.

In addition, the optical transmission device for visible light communication of the present invention further includes a detector for power control according to the user's brightness command.

 The power converter of the optical transmission device for visible light communication of the present invention may obtain a desired output voltage or output current through pulse width modulation or pulse frequency modulation, and includes a DC / DC converter including an inductor at an output terminal.

The driving unit of the optical transmission device for visible light communication includes a switching element, and the switching element and the lighting LED lamp are connected in parallel, and the switching element and the lighting LED lamp connected in parallel are connected in series with the inductor of the DC / DC converter. do.

In addition, the driving unit of the optical transmission device for visible light communication of the present invention is turned on / off according to the signal coded by the encoder to operate at a high speed in the switching region.

The detector of the optical transmission device for visible light communication of the present invention detects a current flowing through the inductor of the output terminal of the DC / DC converter, and is located at either the rear end of the inductor or the rear end of the power change unit of the DC / DC converter.

Luminance control according to a user's command input to the control unit of the optical transmission device for visible light communication of the present invention is analog or pulse width modulation.

The inductor at the output end of the optical transmission device for visible light communication of the present invention operates as a current source containing a direct current or alternating current component.

The optical transmission device for visible light communication according to the present invention having the above configuration has excellent power conversion efficiency and element heating characteristics because the driving element of the driving unit operates in a switching driving method. In addition, high frequency switching driving of the driving device enables high-speed data communication.

In addition, the power control method of the optical transmission device for visible light communication according to the present invention is very suitable as a lighting device because the brightness can be adjusted according to the user's command.

In addition, the brightness control of the LED lamp for lighting according to the present invention can minimize the overshoot period by controlling the current of the inductor rather than controlling the current of the LED lamp. In addition, the present invention has the advantage that the electrolytic capacitor which has the most direct effect on the lifetime of the analog circuit is not used.

 In addition, the optical transmission device for visible light communication of the present invention does not interfere with existing radio waves. Therefore, it is possible to transfer the necessary data using the visible light communication device of the present invention in the hospital, aircraft that can cause the malfunction of the device due to the interference of radio waves. In addition, all of the visible lights can be installed, it can be installed and used in offices, indoor and outdoor living spaces where the lights are installed. Therefore, the optical transmission device for visible light communication of the present invention can be used as a terminal device for providing a home network and ubiquitous communication service by providing a data communication function while replacing the positions of these lights.

In addition, the optical transmission device for visible light communication of the present invention can contribute to energy saving, which is currently a social issue, by increasing power conversion efficiency.

1 is a block diagram of an optical transmission device for visible light communication according to the present invention.
FIG. 2 is a block diagram of an optical transmission device for visible light communication showing the first embodiment of FIG.
3 is a block diagram of an optical transmitter for visible light communication showing the second embodiment of FIG.
4 is a block diagram showing a configuration of a control unit.
5 is a flowchart of a power control method of an optical transmission device for visible light communication according to the present invention;
Figure 6 is a comparison diagram showing the change in current according to the brightness control of the analog system.
7 is a comparison diagram showing a change in current according to adjustment of the luminance of a pulse width modulation (PWM).
8 is a detailed circuit diagram of the embodiment of FIG.
9 is a detailed circuit diagram different from FIG. 8 of the embodiment of FIG.

 Hereinafter, the configuration and operation of the embodiments of the present invention will be described with reference to the accompanying drawings.

1 is a block diagram of an optical transmission device for visible light communication according to the present invention, and FIG. 2 is a block diagram of a first embodiment of the optical transmission device for visible light communication shown in FIG. 3 is a block diagram of an optical transmission device for visible light communication showing the second embodiment of FIG. As shown in FIG. 1, the optical transmission device for visible light communication includes a power converter 101, a driver 103, an encoder 105, and a controller 104.

2 and 3, as another embodiment of FIG. 1, further includes a detection unit 120 for controlling current of the lighting LED lamp 108 to adjust brightness by the user's brightness command 106.

The power converter 101 of the optical transmission device 100 for visible light communication according to the present invention includes an inductor 110 which is a current source at an output terminal. The driving unit 103 and the lighting LED lamp 108 are connected in parallel, and the driving unit 103 and the lighting LED lamp 108 connected in parallel are connected in series to the inductor 110 which is a current source.

 The optical transmission apparatus 100 for visible light communication according to the present invention further includes a detector 120 for adjusting the brightness of the LED lamp 108 for illumination according to a user's command, and the detector 120 includes a power changer 101. Is connected in series at the back end.

 The power conversion unit 101 of the optical transmission device 100 for visible light communication according to the present invention is composed of any one of a DC / DC converter or a DC / DC converter only connected in series with the AC / DC converter. Consists of all kinds of converters with an inductor in the output stage.

The current source 110 of the optical transmission device 100 for visible light communication serves as an inductor at an output terminal of the power converter 101.

The driving unit 103 of the optical transmission device 100 for visible light communication includes a switching element, and the switching element includes a MOSFET and all kinds of switching elements capable of high-speed switching in addition to BJT, IGBT, JFET, HEMPT, SCR, and THRISTOR. . Here, the high speed switching means a speed of about 2 Mbps for an audio signal and about 10 Mbps for a video signal. The detector 120 is composed of a resistor.

Since DC power is required to operate the LED lamp 108 for lighting of the visible light communication device 100 for transmitting light according to the present invention, the power converter 101 performs AC / DC conversion, and then, the above-described DC / DC converter. Is converted into an appropriate voltage or current required for the optical transmission device 100 for visible light communication, or the DC / DC converter described above is converted into an appropriate voltage or current required for the optical transmission device 100 for visible light communication.

The inductor 110, which is the current source, receives a voltage or current from the power converter 101 and supplies a current for operating the lighting LED lamp 108 of the optical transmission device for visible light communication of the present invention. Currently-produced general lighting LED lamp 108 emits light at a current of about 10mA ~ 350mA, and in order to use as a light source to supply a plurality of LED lamps, the current source 110 is capable of high voltage, high current operation do. The inductor 110, which is a current source of the present invention, operates as a current source in which an AC component is included in DC or DC. The current value flowing through the inductor 110 of the present invention is controlled through the pulse width modulation or the pulse frequency modulation of the power converter 101, and the switching frequency may operate at a commercially available frequency level (100 KHz).

Data 107 received by the encoding unit 105 of the optical transmission device 100 for visible light communication comes in from the outside, and the encoding unit 105 of the optical transmission device 100 for visible light communication receives data received from the outside ( 107 is coded as a digital signal that can be transmitted to the LED lamp 108 for lighting by switching the switching element of the driver 103 on / off.

The high-speed switch operation of the switching element of the driving unit 103 of the optical transmission apparatus 100 for visible light communication according to the present invention is switched at a speed of about 2 Mbps when the signal coded by the encoder 105 is an audio signal, and the video signal. If the switch is about 10Mbps. When the signal coded by the encoder 105 is high ('1'), the switching element of the driving unit 103 is turned on so that all of the currents of the inductor 110 which is the current source are the switching elements of the driving unit 103. At this time, the illumination LED lamp 108 is turned off. On the contrary, when the signal coded by the encoder 105 is low ('0'), the switching element of the driving unit 103 is opened so that the current of the current source 110 is all directed to the illumination LED lamp 108. The flow of the LED lamp 108 is turned on. As described above, the illumination LED lamp performs visible light communication with an external light receiving device while repeating on / off according to the signal coded by the encoder 105.

Even if the LED lamp for illumination 108 of the visible light communication apparatus for transmitting light according to the present invention is repeatedly turned on / off, the light transmitting apparatus 100 for visible light communication according to the present invention is used for lighting because it is fast enough not to be recognized by the human eye. Can be used. The human eye does not notice blinking more than 100 times per second.

The detection unit 120 of the optical transmission device 100 for visible light communication uses the present invention for lighting in a general home, office, etc., for the user to adjust the brightness of the brightness command 106 for adjusting the brightness of the illumination, the illumination LED In order to control the current of the lamp 108, the output current flowing through the lighting LED lamp 108 is detected through the sensing resistor of the detector 120. Even though the position of the detector 120 is different in FIGS. 2 and 3, the detected output current is equal to the output current of the inductor 110, which is a current source, because the current flowing through the switch and the lighting LED lamp of the driver 103 is the same. The value of the detected current does not change with position.

The magnitude of the detected current is recognized as the brightness of the LED lamp 108 for illumination. For example, a large amount of current is perceived as bright light in the human eye. The intensity of the detected visible light signal is sent to the control unit 104. The magnitude of the current flowing through the lighting LED lamp 108 detected through the detector 120 has a constant value regardless of the operation of the driver 103.

3 is a block diagram of an optical transmission device for visible light communication showing the second embodiment of FIG.

As shown in FIG. 3, the detector 120 is located at the rear end of the inductor 110 as a current source.

The power converter 101 of the optical transmission device 100 for visible light communication according to the present invention includes an inductor 110 which is a current source at an output terminal. The driving unit 103 and the lighting LED lamp 108 are connected in parallel, and the parallel driving unit 103 and the lighting LED lamp 108 are connected in series to the detection unit 120.

The optical transmission device for visible light communication shown in FIG. 3 performs the same operation as described with reference to FIG. 2 except that the position of the detection unit is different from that of FIG.

4 is a block diagram showing the configuration of a control unit.

As shown in FIG. 4, the control unit 104 of the optical transmission device 100 for visible light communication according to the present invention includes an op-amp 160, a controller 104, and a modulator 140. . The op amp 160, the modulator 140, and the controller 150 of the controller 104 compare the current command value of the inductor 110, which is a current source of the DC / DC converter output, with the magnitude of the current detected by the detector 120. do. In this case, the inductor current command value of the output terminal of the DC / DC converter is equal to the luminance command 106 of the user. The control unit of the present invention compares the output command of the luminance command 106 and the inductor 110 detected by the detector 104 to equal the output current of the power change unit 101 and the value of the luminance command 106 of the user. Adjust so that The brightness of the lighting LED lamp 106 according to the brightness command 106 of the user includes an analog brightness control and pulse width modulation (PWM). The luminance control method according to the luminance command 106 of the user will be described later.

5 is a flowchart of a power control method of an optical transmission device for visible light communication according to the present invention.

The brightness command 106 of the user and the output current of the power converter 101 flowing through the inductor 110 which is a current source in the detector 120 are detected and compared with the brightness command 106 to control the power converter 101. Here's how.

First, a step of detecting a current flowing in the illumination LED lamp 108 is performed (510). This detection current is an output current flowing through the LED lamp for lighting when the switching element of the driving unit 103 is turned off, which is the same as the current flowing through the inductor 110 as a current source. In operation 520, a current command value of the inductor 110 of the DC / DC converter output terminal, which is a step of measuring the luminance command 106 of the user, is measured. The magnitude of the output current flowing through the lighting LED lamp is compared with the command value of the inductor 110 of the DC / DC converter output terminal of the power converter 101.

After the comparison step, the power change unit requests power control as a result of the comparison.

 I) When the detected output current is greater than the inductor current command value of the DC / DC converter output terminal (530), the controller requests to lower the output current of the power converter (540).

 Ii) When the detected output current is smaller than the inductor current command value of the DC / DC converter output terminal (550), it is requested to increase the output current of the power converter (560).

I) If the detected output current is within the threshold range of the inductor current command value of the DC / DC converter output terminal (570), the output current of the power converter 101 is maintained (580).

Table 1 below summarizes the above-described power control method.

Output Current Flowing into LED Lamp for Lighting>
Inductor current command value at DC / DC converter output Output current flowing through LED lamp for lighting <
Inductor current command value at DC / DC converter output Output current flowing through lighting LED lamps =
Inductor current command value at DC / DC converter output Output of power converter
Ask to be lowered Output of power converter
Ask to be elevated Output of power converter
Stay current

6 is a comparative diagram showing a change in current according to the brightness control of the analog method when using the optical transmission device for visible light communication according to the present invention for illumination.

As shown, the optical transmission device for visible light communication according to the present invention varies the magnitude of the conduction current of the LED lamp for illumination according to the brightness command of the user. Since the user recognizes the average value of the conduction current of the LED lamp for illumination as the brightness of the illumination lamp, when the magnitude of the conduction current is large, the average value is increased and the user recognizes that the brightness of the illumination lamp is increased. On the other hand, when the magnitude of the conduction current is small, the average value becomes small, and the user recognizes that the brightness of the lamp is reduced.

FIG. 7 is a comparison diagram illustrating a change in current when a brightness of the lighting LED lamp is adjusted by a pulse width modulation (PWM). As shown, in the optical transmission device for visible light communication according to the present invention, the conduction section of the conduction current of the LED lamp for illumination varies according to the brightness command of the user, and the data is carried on either the front or the back of the conduction section. . Since the user recognizes the average value of the conduction current of the illumination LED lamp as the brightness of the illumination lamp, if the conduction section of the conduction current is large, the average value is increased and the user recognizes that the brightness of the illumination lamp is increased. On the other hand, when the conduction section of the conduction current is small, the average value becomes small, and the user recognizes that the brightness of the lamp is reduced.

8 and 9 are detailed circuit diagrams showing an embodiment of the block diagram shown in FIG.

As shown in FIG. 8, the power converter 101 of the present invention is applied to an active clamp forward converter.

9 illustrates an embodiment in which the power converter 101 of the present invention is applied to a half-bridge converter.

100: optical transmission device for visible light communication 130: modulation command
101: power converter 140: modulator
103: driving unit 150: controller
104: control unit 160: OPAMP
105: encoder
106: luminance command
107: data
108: LED lamp for lighting
110: current source inductor
120: detector

Claims (7)

In a light transmitting device for performing visible light communication with an external light receiving device using a plurality of lighting LED lamps that emit visible light as a light source,
A power conversion unit for supplying DC power to the LED lamp for lighting;
A driving unit driven by a switching driving method and supplying an operating current to the lighting lamp;
An encoder connected to an external network to receive and code data and supply the data to the driver;
A controller for controlling operations of the power converter, the driver, and the encoder;
It includes a detection unit for measuring the intensity of the visible light signal transmitted from the LED lamp for illumination,
The detector detects a current flowing through an inductor of an output terminal of the DC / DC converter constituting the power converter, and is located at either the rear end of the inductor or the rear end of the power change unit of the output terminal of the DC / DC converter. Optical transmitter for visible light communication.
delete The method of claim 1, wherein the power conversion unit
Through pulse width modulation or pulse frequency modulation, the desired output voltage or output current can be obtained.
And a DC / DC converter or a converter composed of only a DC / DC converter connected in series with an AC / DC converter, wherein the DC / DC converter has an inductor at an output terminal.
The method of claim 3, wherein the driving unit
Including a switching element,
The switching element and the LED lamp for lighting are connected in parallel,
And the switching element connected in parallel and the LED lamp for illumination are connected in series with the inductor of the AC / DC converter or the DC / DC converter.
The method of claim 1, wherein the driving unit
The optical transmission device for visible light communication, characterized in that on / off in accordance with the signal coded by the encoder to operate at a high speed in the switching area.
delete The optical transmission apparatus of claim 1, wherein the brightness control according to a user's command input to the controller is an analog method or a pulse width modulation method.

Images