JP2010267386A - Discharge lamp lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device suitable as a transmission means for visible light communication with a simple circuit structure for pulse superposing and operating without fail. <P>SOLUTION: The discharge lamp lighting device includes: a DC power supply 11a; an inverter 11b to convert DC power supply output voltage into high frequency AC voltage; a load circuit 11c connected to the inverter AC output terminal including a resonance circuit RC; a discharge lamp 10 connected to the load circuit and makes high-frequency lighting; and a control means 15 capable of controlling the inverter lighting frequency for every period as well as of superimposing carrier frequency on discharge lamp light emission by switching a plurality of lighting frequencies f<SB>L</SB>, f<SB>H</SB>, in such a way that a zero-point phase of a lamp current waveform synchronizes with a polarity inversion phase of the transmission sinal waveform. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a discharge lamp lighting device used as transmission means of an optical communication system that transmits data using visible light emitted from a discharge lamp.

  An optical communication system using visible light using light emitted from a discharge lamp as a transmission medium is known (see, for example, Patent Document 1). As modulation methods in this type of optical communication system, frequency modulation, amplitude modulation, pulse modulation, and the like are known. Pulse modulation includes pulse width modulation, pulse amplitude modulation, pulse density modulation, pulse position modulation, and pulse code modulation. Further, the pulse position modulation includes quaternary pulse position modulation (4PPM) standardized as a visible light ID system by the Japan Electronics and Information Technology Industries Association (JEITA) in 2007 (see Non-Patent Document 1).

  The communication method employed in the above standard is a “visible light ID system” for low-speed communication, and a 4-value PPM method (4-value pulse position modulation) is adopted as a modulation method.

  In the 4-value PPM system, the subcarrier frequency (subcarrier frequency) is set to 28.8 kHz, and 4 data (00, 01, 10 and 11) are used as 4 symbols (4 frames) of the inverter output lighting frequency (main carrier frequency). Use to modulate. One symbol is further equally divided into four slots, and becomes 1 when modulated by superimposing a subcarrier frequency on one of the slots according to data, and the remaining 3 slots are unmodulated. 0. That is, four types of values of 00, 01, 10 and 11 can be indicated depending on where in the four slots the slot indicating 1 is superimposed with the sub-modulation frequency. According to this communication method, a maximum transmission speed of 4.8 kbps can be obtained. Further, the light output is cut off in the modulation section, and the light output is not cut off in the non-modulation section.

JP-A-60-032443

Japan Electronics and Information Technology Industries Association (JEITA) Standard “Visible Light ID System” (CP-1222)

  As a light source for visible light communication, it is generally preferred to use a light emitting diode because of its relatively good switching characteristics. However, optical communication using a light output from a discharge lamp such as a fluorescent lamp as a transmission medium. Is also theoretically possible. However, when switching the lamp current of the discharge lamp in order to superimpose a pulse on the light output, it is necessary to apply a high restart voltage to the discharge lamp when the lamp current is turned off and then turned on. Not only is the life of the device likely to be shortened, but also there is a problem that the circuit configuration becomes complicated, resulting in an increase in cost.

  An object of the present invention is to provide a discharge lamp lighting device suitable as a transmission means for visible light communication that has a simple circuit configuration for pulse superposition and operates reliably.

  In order to solve the above-mentioned problems, a discharge lamp lighting device according to the invention of claim 1 includes a DC power supply; an inverter that converts an output voltage of the DC power supply into a high-frequency AC voltage; and a resonance circuit that is connected to an AC output terminal of the inverter. A connected load circuit; a discharge lamp connected to the load circuit for high-frequency lighting; a lighting frequency of the inverter as a main carrier frequency; this lighting frequency can be controlled for each cycle and a zero point phase of the lamp current waveform is transmitted Control means for superimposing the sub-carrier frequency on the light emission of the discharge lamp by switching a plurality of lighting frequencies so as to be synchronized with the polarity conversion phase of the signal waveform.

  A discharge lamp lighting device according to a second aspect of the present invention is the discharge lamp lighting device according to the first aspect, characterized in that the lighting frequency is in an even multiple relationship with respect to the sub-carrier frequency.

  A discharge lamp lighting device according to a third aspect of the invention is characterized in that, in the discharge lamp lighting device according to the first or second aspect, the load circuit has a resonance frequency of the resonance circuit equal to or less than twice the sub-carrier frequency. .

  A discharge lamp lighting device according to a fourth aspect of the present invention is the discharge lamp lighting device according to any one of the first to third aspects, wherein transmission is stopped when the discharge lamp is not lit at a relatively low output frequency. It is characterized by doing.

  According to the first aspect of the present invention, the plurality of lighting frequencies are switched by the control means that can be controlled for each cycle of the lighting frequency so that the zero point phase of the lamp current waveform is synchronized with the polarity conversion phase of the transmission signal waveform. Since the lamp current phase of the lighting frequency before and after the change coincides at the frequency change point, the switching is performed smoothly, and the light output of the discharge lamp that is turned on via the load circuit including the resonance circuit is kept on. Since it changes instantaneously, it is possible to provide a discharge lamp lighting device that accurately modulates the light output of the discharge lamp in accordance with the data of the transmission signal.

  Moreover, since the switching of the lighting frequency is performed by the control operation of the control means, the circuit configuration is simplified.

  In the invention of claim 2, since the lighting frequency is in an even multiple relationship with respect to the subcarrier frequency, the zero point phase of the lamp current waveform is synchronized with the polarity conversion phase of the transmission signal waveform when switching the lighting frequency. There is an effect that it is possible to provide a discharge lamp lighting device in which the operation of shifting the lighting frequency is not excessive in circuit operation and the pulse modulation operation is accurately performed.

  In addition, if the even-numbered relationship between the lighting frequency and the sub-carrier frequency is a preferred example of 2 times and 4 times, the effect is that the lighting state of the discharge lamp when the light output is low is stable and the circuit design is facilitated. Play.

  In the invention of claim 3, when the resonance frequency of the resonance circuit of the load circuit is not more than twice the subcarrier frequency, the lighting frequency can be set in the phase advance region of the resonance circuit. There is an effect that it is possible to provide a discharge lamp lighting device that has a multiple relationship and can be easily set to a value that increases the light output difference.

  According to the invention of claim 4, by stopping the transmission when the discharge lamp is not lit at a lighting frequency with a relatively low output, the discharge lamp operation becomes unstable and a communication abnormality is likely to occur. By avoiding this, the burden on the discharge lamp and the discharge lamp lighting device can be reduced.

It is a block circuit diagram of the whole optical communication system which implements the discharge lamp lighting device of the present invention. It is a circuit diagram which shows one form for implementing the discharge lamp lighting device of this invention as a transmission means of an optical communication system. Similarly, it is explanatory drawing which shows the relationship between data, a 4 value PPM signal, and an optical output. It is a graph which similarly shows the resonance characteristic curve of a load circuit. It is a wave form diagram explaining the relationship between the light output of a modulation state, and a lighting frequency similarly. Similarly, it is a waveform diagram for explaining the phase relationship between the transmission signal waveform and the lamp current in comparison with that of the comparative example. Similarly, it is a waveform diagram showing an enlarged relationship between a four-value PPM signal, a lamp current waveform, and a light output change.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  An optical communication system that implements the discharge lamp lighting device of the present invention comprises a transmitting means 1 and a receiving means 2 as shown in FIG. In FIG. 1, reference numeral 3 denotes an information source 3 that transmits information data to be transmitted, and reference numeral 5 denotes a device that receives the received information data.

  The transmission means 1, that is, the discharge lamp lighting device of the present invention comprises a discharge lamp 10, such as a fluorescent lamp, a discharge lamp lighting circuit 11, an information data receiving means 12, a pulse modulation means 13, and a drive signal generating means 14. The pulse modulation means 13 and the drive signal generation means 14 are included in the control means 15 in FIG.

  The discharge lamp 10 is a means for generating a signal transmission medium that emits a light-modulated transmission signal, and a discharge lamp such as a low-pressure discharge lamp or a high-pressure discharge lamp can be used. When light modulation is performed using visible light generated by the discharge lamp 10, for example, a fluorescent lamp or an HID lamp can be used, and when light modulation is performed using ultraviolet light, a sterilization lamp can be used.

  When the discharge lamp 10 is a fluorescent lamp, the hermetic container, the phosphor layer, the discharge generating means, and the discharge medium are the main components, and the low-pressure vapor or gas discharge of the discharge medium, which will be described later, enclosed in the hermetic container By irradiating the phosphor layer with the ultraviolet rays emitted by the phosphor, the phosphor is excited to generate visible light.

  The airtight container is formed of a glass bulb or the like, and is allowed to have various known forms such as a straight tube shape, an annular shape, a U shape, a W shape, and a spiral shape. Further, the outer diameter and length of the hermetic container can be variously set according to the type and rating of the fluorescent lamp.

  The phosphor layer can be formed using a known phosphor for a fluorescent lamp. The phosphor used is not particularly limited in the present invention. For example, generally used three-wavelength phosphors or halophosphate phosphors can be used. The phosphor layer can be formed by a conventional method.

  The discharge generating means is a means for generating a low-pressure metal vapor or gas discharge of a discharge medium enclosed in an airtight container, and can be constituted by, for example, an electrode or a high-frequency magnetic field generating means. In the case of electrodes, internal electrodes and external electrodes are known, but either of them may be used.

  As shown in FIG. 2, the discharge lamp lighting circuit 11 includes a DC power source 11a, an inverter 11b, a load circuit 11c, and a load state detection means 16. In FIG. 1, the inverter 11b and the load circuit 11c are illustrated as one circuit block.

  The DC power supply 11a is an input supply means viewed from an inverter 11b described later, and outputs a DC voltage and applies it as an input voltage to the inverter 11b. The DC power supply 11a may be a DC power supply, a battery power supply, a capacitor, or the like obtained by rectifying an AC voltage.

  In the present embodiment shown in FIG. 2, the DC power supply 11a includes a bridge-type full-wave rectifier circuit 11a1 and an active filter 11a2. The bridge-type full-wave rectifier circuit 11a1 has an AC input terminal connected to the low-frequency AC power supply 4 and outputs a pulsating DC voltage to a DC output terminal. The active filter 11a2 is composed of a step-up chopper, and its input end is connected to the DC output end of the bridge-type full-wave rectifier circuit 11a1. Then, the voltage is boosted to a desired voltage between both electrodes of the smoothing capacitor C1 connected in parallel to the DC output terminal of the active filter 11a2, and a smoothed DC voltage is output.

  The inverter 11b is means for converting a DC voltage output from the DC power supply 11a into a high-frequency AC, and includes at least one switching element. In the present invention, the circuit system of the inverter is not particularly limited. For example, a half bridge type inverter, a full bridge type inverter, a single stone type inverter, or the like can be used.

  Further, in order to modulate the transmission signal according to the oscillation frequency, that is, the lighting frequency, the inverter 11b is changed between a plurality of, preferably two, predetermined values by the control means 15 described later. Thus, by varying the lighting frequency, for example, pulse modulation is performed based on a modulation signal such as a quaternary PPM signal. Further, if desired, the high-frequency AC output can be controlled to be constant, or the high-frequency AC output can be varied to dimm the discharge lamp. The inverter 11b is allowed to include an insulated or non-insulated output transformer as desired.

  In the present embodiment shown in FIG. 2, the inverter 11b is a half-bridge inverter, and a series circuit of a pair of switching elements Q1 and Q2 is connected between both ends of the DC power source 11a, that is, between both electrodes of the smoothing capacitor C1. Then, a rectangular wave AC voltage is output between both ends of the switching element Q2.

  The load circuit 11c is circuit means interposed between the inverter 11b and the discharge lamp 10 when the discharge lamp 10 is connected to the discharge lamp lighting device in order to energize the discharge lamp 10 by the output of the inverter 11b. . The load circuit 11c includes a resonance circuit RC. Then, by connecting the discharge lamp 10 to the output terminal of the inverter 11b via the resonance circuit RC, it is possible to apply a resonance voltage that is appropriately resonated to the discharge lamp 10 as desired by the load circuit 11c.

  The resonance circuit RC is preferably a series resonance circuit, and the discharge lamp 10 is connected to a position on the circuit to which the resonance voltage is applied. Moreover, the load circuit 11c can provide a current limiting impedance to the discharge lamp 10 connected thereto. The reactance of the resonance circuit RC can be used as the current limiting impedance.

  In the present invention, the lamp current supplied to the discharge lamp 10 is changed by the resonance characteristics of the load circuit by changing the lighting frequency by the control means described later while the resonance condition of the resonance circuit RC of the load circuit 11c is fixed. Thus, pulse modulation is performed by changing the optical output between the high output state and the low output state. During the pulse modulation, the discharge lamp 10 remains on.

  Further, when there is no modulation, the light output of the discharge lamp 10 can be set to an intermediate output state between the high output state and the low output state at the time of modulation. As a result, the difference between the amount of light at the time of modulation and the amount of light at the time of non-modulation can be reduced. Furthermore, the light output of the discharge lamp 10 can be dimmed at a desired level when there is no modulation.

  In one embodiment of the present invention shown in FIG. 2, the load circuit 11c is mainly composed of a resonance circuit RC formed by a series circuit of an inductor L1 and a resonance capacitor C2, and the inverter 11b is connected via a DC cut capacitor C3. Connected to the output terminal. The discharge lamp 10 has a pair of power supply side terminals connected in parallel between both ends of the resonance capacitor C2. A known filament heating circuit such as a capacitor (not shown) as an electrode preheating circuit can be appropriately connected between the pair of non-power supply side terminals.

  The load state detection means 16 includes a lamp voltage detection circuit and / or a lamp current detection circuit for the discharge lamp 10, and detects the electrical operation state of the discharge lamp 10 to perform feedback control for input control of the discharge lamp 10, which will be described later. The discharge lamp 10 acts for a transmission stop protection operation, a lamp mounting protection operation, and so on when the discharge lamp 10 is in a broken state.

  The transmission data receiving means 12 is constituted mainly by an interface, for example, and receives information data generated from the external information source 3.

  Next, the control means 15 shown in FIG. 2 will be described. The control means 15 is preferably composed mainly of a digital device such as a microcomputer and a DSP (digital signal processor). The oscillation frequency can be controlled for each cycle according to the lighting frequency of the inverter 11b, and a plurality of, preferably two, lightings are performed so that the zero point phase of the lamp current waveform is synchronized with the polarity conversion phase of the transmission signal waveform. Switch the frequency. As a result, since the lamp current supplied to the discharge lamp 10 changes according to the lighting frequency, the subcarrier frequency is superimposed on the light output of the discharge lamp 10 to perform pulse modulation. In the pulse modulation means 13, the information data receiving means 12 accepts information data sent from the information source 3, and the pulse modulation means 13 switches the lighting frequency corresponding to the information data. The drive signal generating means 14 generates a drive signal whose oscillation frequency is controlled to a predetermined value corresponding to the pulse modulation, and alternately drives the switching elements Q1 and Q2 of the inverter 11b.

  The polarity change phase of the transmission signal waveform refers to the rising and falling phases of the transmission signal.

  Next, pulse modulation will be described. In FIG. 3, the left end portion shows data from the top, a quaternary PPM signal, and an optical output. There are four types of data: 00, 01, 10, and 11. The 4-level PPM signal is 1000 when the data is 00, 0100 when the data is 01, 0010 when the data is 10, and 0001 when the data is 11. Then, one symbol time is divided into four equal parts, and four slots are allocated. Further, one slot corresponds to three cycles of 28.8 kHz, the subcarrier frequency. Taking the quaternary PPM signal 1000 for data 00 as an example, the first slot is 1 of the quaternary PPM signal, and the second to fourth slots are quaternary PPM signal 0, respectively. When the quaternary PPM signal is 1, the corresponding slot is pulse-modulated with 3 cycles of 28.8 kHz of the subcarrier frequency. In contrast, when the quaternary PPM signal is 0, the corresponding slot is not modulated, and in this embodiment, the optical output is constant in the medium output state.

  The optical output is pulse-modulated when the quaternary PPM signal is 1, and alternately changes between a high output state and a low output state.

  The above four types of data can be modulated with the four symbol times described above. The maximum transmission speed is 4.8 kbps.

FIG. 4 shows a resonance characteristic curve of the resonance circuit RC of the load circuit 11c, where the horizontal axis represents frequency and the vertical axis represents lamp current. The resonance frequency f ₀ is set to be less than 2 times the 28.8kHz of sub-carrier frequency, the left side phase advancing area of the resonance frequency f _0, the right side is a slow region.

In this embodiment, the operating frequency of the inverter 11b are both set to be positioned to the slow region, the first lighting frequency f _L relatively low, the second operating frequency f _H relatively high, the third operating frequency f _M is an intermediate frequency in between. Further, the first and second lighting frequencies f _L and f _H are selected so as to have an even multiple relationship with respect to the subcarrier frequency of 28.8 kHz. Preferably, the first lighting frequency f _L is 57. which is twice 28.8 kHz. Similarly, the second lighting frequency f _H is 4 times 115.2 kHz. The intermediate frequency _{f M,} the first and second operating frequency _f L, is an intermediate frequency _{f H,} is 67.3KHz.

FIG. 5 shows an enlarged view of a 2-slot portion that is the first half of the first symbol among the four symbols shown in FIG. During modulation of the light output, the lighting frequency is f _L, the optical output becomes high output state. The lighting frequency when is f _H, a low output state. It can be understood that pulse modulation is performed by alternately generating a high output state and a low output state at the subcarrier frequency. Incidentally, the lighting frequency at the time of non-modulation is f _M, because the light output at this time is an intermediate level of high and low, the direction in which the difference in light output of the average optical output and the non-modulated during the time of pulse modulation is reduced You can also understand that it works.

  With reference to FIG. 6, the influence of the phase of the lamp current upon switching of the lighting frequency in pulse modulation will be described. The rectangular waveform in the figure is the transmission signal waveform, and the sinusoidal waveform is the lamp current waveform. FIG. 6A shows this embodiment, and FIG. 6B shows a comparative example.

  In this embodiment, as shown in FIG. 6A, the polarity change phase (frequency change point) of the transmission signal waveform and the 0 phase of the lamp current waveform match. For this reason, when the lighting frequency is switched in synchronization with the polarity switching phase of the transmission signal waveform, the lamp current flowing depending on the lighting frequency after the switching rises from the zero point to the positive polarity, so there is a time delay before and after the frequency switching. It does not occur.

  For this reason, since the lighting frequency can be switched without accompanying a rapid change in the lamp current, the switching is facilitated and no stress occurs in the discharge lamp lighting circuit 11.

  The above switching operation can be easily realized by making the lighting frequency (main carrier frequency) an even multiple relationship with respect to the subcarrier frequency of the transmission signal waveform. In the illustrated form, the lighting frequency is quadrupled with respect to the subcarrier frequency of 28.8 kHz. Accordingly, when the lighting frequency is switched to, for example, twice as much as the polarity switching phase of the transmission signal waveform of the subcarrier frequency, the lamp current flowing according to the lighting frequency after the switching rises from 0 point to positive polarity.

  On the other hand, as shown in FIG. 6B, in the comparative example, the lamp current is not synchronized with the zero point at which the frequency can be changed during the polarity switching phase of the transmission signal waveform having the subcarrier frequency of 28.8 kHz. When the lighting frequency is controlled for each cycle as in this embodiment, the lighting frequency cannot be changed, and therefore it cannot be modulated into a desired pulse waveform. In this comparative example, the lighting frequency is not in an even multiple relationship with respect to the transmission signal waveform whose subcarrier frequency is 28.8 kHz.

7, the lighting frequency in the present embodiment the switching shows the relationship between the lamp current waveform and the optical output waveform due to, in switching between the first operating frequency f _L and a second ignition frequency f _H, the lamp current waveform It shows that the zero point phase and the polarity conversion phase are synchronized.

In embodiments described above, one slot and lighting time of the first lighting frequency f _L, when aliquoted and modulated by the lighting time of the second operating frequency f _H, the first and second lighting frequency Although an embodiment in which f _L and f _H are a plurality of times of the subcarrier frequency has been described, the present invention is not limited to this, and in short, the zero point phase of the lamp current waveform and the polarity conversion phase of the transmission signal waveform are It only needs to be synchronized.

  By the way, the receiving means 2 of the optical communication system is provided with a light receiving means 21, and receives the light output modulated by the transmission signal radiated from the discharge lamp lighting device of the transmitting means 1, and is included therein. This is means for extracting a transmitted signal and communicating with the transmission means. The receiving means 2 can comprise a pulse demodulating means 23 in order to extract information data from a transmission signal included in the light output of the discharge lamp. If desired, a vibration component extracting unit for selectively extracting a communication signal can be interposed between the light receiving unit 21 and the pulse demodulating unit 23. In order to increase the output level of the light receiving means 21 to a desired level, an amplifier 22 can be interposed between the light receiving means 21 and the pulse modulating means 23.

  In this embodiment, the receiving unit 2 includes a light receiving unit 21, an amplifier 22, and a pulse demodulating unit 23.

  The light receiving means 21 is a means for receiving the light output of the discharge lamp 10, for example, a fluorescent lamp. In order to make it easy to extract the transmission signal included in the light output of the discharge lamp 10, a light receiving sensitivity characteristic is provided that can selectively receive main spectral lines of the discharge medium enclosed in the discharge lamp 10 as desired. can do.

  As the main spectral lines of the discharge medium in the discharge lamp 10, for example, in the case of a fluorescent lamp mainly using a low-pressure mercury vapor discharge for general illumination, the spectral lines of wavelengths 405, 435 and 436 nm are almost all types as described above. This is very convenient because it can be easily distinguished from the phosphor emission.

The light receiving means 21 is preferably configured using a photoelectric conversion element. For example, a photodiode, a phototransistor, or the like can be used. As the photodiode, for example, a PIN photodiode, a photoPN diode, a Si photodiode, or the like can be used.
The amplifier 22 amplifies the transmission signal obtained from the light receiving means 21 to a required level.

  The pulse demodulation means 23 restores transmission data by pulse-demodulating the amplified transmission signal. The obtained transmission data is taken out from the receiving means 21 and input to, for example, the external device 5 for communication.

  DESCRIPTION OF SYMBOLS 1 ... Transmission means, 3 ... Information source, 4 ... Low frequency alternating current power supply, 10 ... Discharge lamp, 11 ... Discharge lamp lighting circuit, 11a ... DC power supply, 11a1 ... Bridge type full wave rectification circuit, 11a2 ... Active filter, 11b ... Inverter, 11c ... load circuit, L1 ... inductor, C2 ... resonance capacitor, 15 ... control means, 16 ... load state detection means, Q1, Q2 ... switching element, RC ... resonance circuit

Claims (4)

DC power supply;
An inverter that converts the output voltage of the DC power source into a high-frequency AC voltage;
A load circuit including a resonance circuit and connected to the AC output terminal of the inverter;
A discharge lamp connected to a load circuit and operating at high frequency;
The lighting frequency of the inverter is the main carrier frequency, and this lighting frequency can be controlled for each cycle, and the multiple lighting frequencies are switched so that the zero point phase of the lamp current waveform is synchronized with the polarity conversion phase of the transmission signal waveform. A control means for superimposing the subcarrier frequency on the light emission of the discharge lamp by;
A discharge lamp lighting device comprising:   The discharge lamp lighting device according to claim 1, wherein the lighting frequency has an even multiple relationship with respect to the subcarrier frequency.   The discharge lamp lighting device according to claim 1 or 2, wherein the load circuit has a resonance frequency of the resonance circuit that is not more than twice the sub-carrier frequency.   The discharge lamp lighting device according to any one of claims 1 to 3, wherein the transmission is stopped when the discharge lamp is not lit at a lighting frequency at a relatively low output.

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