JP2009266585A - Lighting system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress noise generation caused by characteristics of light emitting diodes in the primary side voltage of a transformer, in a lighting system equipped with the transformer to the primary side of which an almost sine wave AC voltage is supplied and the light emitting diodes connected to its secondary side. <P>SOLUTION: An impedance circuit Z1 is connected to light emitting diodes D1, D2 in series, and an impedance circuit Z2 is connected to light emitting diodes D3-D18 in series. Therefore, if an AC voltage is impressed on the secondary side of the transformer, no current passes through the light emitting diodes unless the impressed voltage reaches the minimum light emitting voltage or higher, and if the voltage reaches the minimum light emitting voltage or higher, both end voltages are almost fixed regardless of the current, a voltage drop is thereby caused according to the current in the impedance circuits although a voltage waveform becomes close to a rectangular wave. Accordingly, both end voltage waveform on the secondary side of the transformer and both end voltage waveform on the primary side of the transformer become close to a sine wave. Therefore, noise generation in the primary side voltage of the transformer can be suppressed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a lighting device using a light emitting diode.

  2. Description of the Related Art Conventionally, there has been known an illuminating device in which a luminaire is connected to a transformer and the luminaire is lit by supplying power without contact by electromagnetic induction (for example, see Patent Document 1). In addition, instead of a transformer, a discharge tube, a light bulb or a fluorescent lamp is connected to the coil as a lighting fixture, and an electric wire or conductor is passed through the coil. There is known an illuminating device for supplying power to a discharge tube, a light bulb or a fluorescent lamp (see, for example, Patent Documents 2 and 3).

  In the illumination device as described above, the light source is a discharge tube or the like, but there is a demand for using a light emitting diode instead. Therefore, FIG. 4 shows a circuit configuration of a lighting device in which a light emitting diode is connected to a transformer. The lighting device 10 includes a transformer 12 connected to an AC power supply 11 that supplies an alternating current having a substantially sinusoidal wave, and a plurality of light emitting diodes 50 to 65 connected to the secondary side of the transformer 12. 50 to 57 and the light emitting diodes 58 to 65 are respectively connected in series, and the light emitting diodes 50 to 57 and the light emitting diodes 58 to 65 are connected in parallel.

In the above configuration, when an alternating voltage is applied to the light emitting diodes 50 to 65 through the transformer 12, the light emitting diodes 50 to 65 do not flow current unless the applied voltage is not lower than the minimum light emitting voltage. since the voltage across regardless current is substantially constant, the voltage waveform across the light-emitting diodes 50 to 65, i.e. the voltage across v ₂ of the secondary side of the transformer 12 is a square wave, as shown in FIG. 5 (a) Close waveform. Accordingly, the waveform of the voltage across v ₁ on the primary side of the transformer 12, since the secondary voltage waveform of the transformer 12 as described above is a waveform close to a rectangular wave, the mutual induction, shown in FIG. 5 (b) It becomes a waveform close to such a rectangular wave. For this reason, the primary side voltage includes many harmonic components, and noise increases.
Japanese Utility Model Publication No. 7-122447 Japanese Utility Model Publication No.59-46496 Japanese Utility Model Publication No. 1-180152

  The present invention has been made to solve the above-described conventional problems. When a light emitting diode is connected to the secondary side of a transformer to which a substantially sinusoidal alternating current is supplied to the primary side, the light emitting diode is provided. An object of the present invention is to provide an illuminating device that can suppress the generation of noise in the transformer primary voltage due to the characteristics.

  In order to achieve the above object, the invention of claim 1 comprises a transformer to which a substantially sinusoidal alternating current is supplied from an alternating current power source on the primary side, and a light source unit connected to the secondary side of the transformer. In the illumination device, the light source unit includes a light emitting diode and an impedance circuit connected in series to the light emitting diode.

  According to a second aspect of the present invention, in the lighting device according to the first aspect, the impedance circuit includes a semiconductor.

  According to the first aspect of the present invention, when an AC voltage is applied to the secondary side of the transformer, current does not flow in the light emitting diode unless the applied voltage exceeds the minimum light emission voltage. Regardless of the voltage at both ends, the voltage waveform is close to a square wave. However, in the impedance circuit, a voltage drop occurs according to the current, so the voltage waveform at the secondary side of the transformer and the primary side of the transformer. The voltage waveform at both ends approaches a sine wave. For this reason, generation | occurrence | production of the noise in a transformer primary side voltage can be suppressed.

  According to the second aspect of the present invention, it is possible to prevent a current exceeding a predetermined value from flowing through the light emitting diode by the semiconductor, and thus it is possible to protect the light emitting diode.

  Hereinafter, lighting devices according to various embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 shows a circuit configuration of an illumination apparatus according to the first embodiment of the present invention. The lighting device 1 according to this embodiment is connected to transformers 3 and 4 to which a substantially sine wave AC current is supplied from a constant current source 2 (AC power supply) to the primary side, and to the secondary side of the transformers 3 and 4, respectively. Light source units 5 and 6.

  The light source unit 5 includes light emitting diodes D1 and D2 and an impedance circuit Z1 connected in series thereto. The light emitting diodes D1 and D2 are connected in parallel so that the forward directions are opposite to each other.

  The light source unit 6 includes light emitting diodes D3 to D18 and an impedance circuit Z2 connected in series to these. The light emitting diodes D3 to D10 and the light emitting diodes D11 to D18 are respectively connected in series, and the light emitting diodes D3 to D10 and the light emitting diodes D11 to D18 are connected in parallel so that their forward directions are opposite to each other.

  Each of the impedance circuits Z1 and Z2 is configured by a resistor, for example, as shown in the figure, but is not limited thereto, and may be configured by a smoothing circuit, a high-pass filter, or the like.

Here, the current supplied from the constant current source 2 is i ₁ , the voltage across the primary side of the transformer 4 is v ₁ , and the voltage across the secondary side of the transformer 4 is v ₂ .

In the illuminating device 1 having the above-described configuration, a current i ₁ having a substantially sinusoidal waveform as shown in FIG. 2A is supplied from the constant current source 2 to the primary side of the transformer 4. An alternating electromotive force is generated on the secondary side, and an alternating voltage is applied. This AC voltage is divided by the light emitting diodes D3 to D18 and the impedance circuit Z2.

In the light emitting diodes D3 to D18, the current does not flow unless the applied voltage becomes equal to or higher than the minimum light emitting voltage. When the applied voltage becomes equal to or higher than the minimum light emitting voltage, the voltage at both ends becomes substantially constant regardless of the current. It becomes. On the other hand, in the impedance circuit Z2, a current flows even when the applied voltage to the light emitting diodes D3 to D18 is equal to or higher than the minimum light emitting voltage, and a voltage drop occurs according to the value. Accordingly, the voltage across v ₂ of the secondary side of the transformer 4, since it is determined by adding the voltage of the voltage and the impedance circuit Z2 of the light emitting diode D3～D18, as shown in FIG. 2 (b), conventional ( The waveform is closer to a sine wave compared to (shown by a broken line).

Accordingly, the waveform of the voltage across v ₁ on the primary side of the transformer 4, the secondary voltage waveform as described above approaches the sinusoidal, due to mutual induction, as shown in FIG. 2 (c), conventional (dashed line Compared to a sine wave. Thereby, noise generation in the primary side voltage of the transformer 4 due to the minimum light emission voltage characteristics and constant voltage characteristics of the light emitting diodes D3 to D18 can be suppressed. The light source unit 5 can achieve the same effects as described above. As a result, when various electric devices other than the light source units 5 and 6 are further connected, it is possible to prevent the noise from affecting the various electric devices.

  Further, since the power source can be supplied to the light source units 5 and 6 without contact, the light source units 5 and 6 can be used outdoors while suppressing the occurrence rate of electric leakage due to rainwater or the like.

  In the case where the minimum light emission voltage of the light emitting diodes is different between the light source units, the constant current source 2 allows the light emitting diode having a higher minimum light emission voltage to quickly reach the minimum light emission voltage and supply a constant current. In order to ensure, the output voltage is boosted. Therefore, since all the light emitting diodes can be turned on at substantially the same timing and the lighting periods can be made substantially the same, flickering of illumination can be prevented.

(Second Embodiment)
FIG. 3 shows a circuit configuration of an illumination apparatus according to the second embodiment of the present invention. In the figure, the same components as those in the first embodiment are denoted by the same reference numerals. The illumination device 1 of the present embodiment is different from the first embodiment in that the impedance circuit includes a transistor Q1 (semiconductor).

  The lighting device 1 includes a transformer 7 to which an alternating current is supplied from the constant current source 2 on the primary side, and a light source unit 8 connected to the secondary side. The light source unit 8 is provided between a diode bridge 81 for full-wave rectifying the secondary side voltage of the transformer 7, a light-emitting diode D19 to which the full-wave rectified voltage is applied, and the diode bridge 81 and the light-emitting diode D19. And an impedance circuit Z3 connected in series to the light emitting diode D19.

  The impedance circuit Z3 is configured by the transistor Q1 described above. A zener diode D20 and resistors R1 to R3 are connected to the transistor Q1, and these operate as a general protection circuit. The Zener diode D20 causes a current to flow when the overvoltage is applied, thereby reducing the voltage. The resistors R1 to R3 divide the voltage value that has been full-wave rectified by the diode bridge 81, and the divided voltage is applied between the emitter and base of the transistor Q1. When this voltage exceeds a predetermined value, the transistor Q1 operates so that the current value flowing between the collector and the emitter, that is, the current value flowing through the light emitting diode D19 does not exceed a predetermined value, thereby protecting the light emitting diode D19.

  In the present embodiment, the transistor Q1 can prevent a current exceeding a predetermined value from flowing into the light emitting diode D19, and thus the light emitting diode can be protected. In this embodiment, the same effect as that of the first embodiment can be obtained.

  In addition, this invention is not limited to the structure of the said 1st and 2nd embodiment, A various deformation | transformation is possible according to the intended purpose. For example, the number of light source units connected to the secondary side of the transformer is not limited to the above, and may be any number. Further, the arrangement of the light emitting diodes in the light source unit is not limited to the above. Also, the number is not limited to the above, and it may be any number.

The circuit block diagram of the illuminating device which concerns on the 1st Embodiment of this invention. (A) is a current waveform diagram supplied to the transformer primary side of the lighting device, (b) is a voltage waveform diagram across the transformer secondary side, and (c) is a voltage waveform diagram across the transformer primary side. The circuit block diagram of the illuminating device which concerns on the 2nd Embodiment of this invention. The circuit block diagram of the conventional illuminating device. (A) is a both-ends voltage waveform figure of the transformer secondary side of the said illuminating device, (b) is a both-ends voltage waveform figure of the transformer primary side.

Explanation of symbols

1 Lighting device 2 Constant current source (AC power supply)
3, 4, 7 Transformers D1 to D19 Light-emitting diode Q1 Transistor (semiconductor)
Z1, Z2, Z3 Impedance circuit

Claims (2)

In a lighting device comprising a transformer to which a substantially sinusoidal alternating current is supplied from an alternating current power source on a primary side, and a light source unit connected to a secondary side of the transformer,
The light source unit includes a light emitting diode and an impedance circuit connected in series to the light emitting diode.   The lighting device according to claim 1, wherein the impedance circuit includes a semiconductor.

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