LED lighting device

Abstract

To provide a power supply separate installation type LED lighting device without requiring an electric shock countermeasure.SOLUTION: An LED lighting device comprises: a power supply unit 1 having a pair of AC input terminals 11a and 11b, and a pair of DC output terminals 12a and 12b; and an LED unit 2 that has a circuit of an LED to which a DC current is supplied via a pair of power supply lines 3a and 3b connected to the DC output terminals 12a and 12b of the power supply unit 1, and a conductive part 21 that is electrostatically coupled via an LED 22 and a dielectric body. The power supply unit 1 contains a DC-DC converter circuit 15, and comprises a common mode inductor 16 between a secondary side of the DC-DC converter circuit 15 and the pair of DC output terminals 12a and 12b.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This invention relates to a power-separated LED lighting device including an LED unit and a separately-located power supply unit.

Background Art

[0002] As a power-separated LED lighting device in which an LED unit and a power supply unit are separately located, Patent Document 1 discloses an LED lighting device in which LED breakdown does not occur even when a common-mode noise voltage (ground noise voltage) is superimposed on an AC power supply to which the power supply unit is connected.

[0003] Specifically, this LED lighting device, as a countermeasure against damage to the LED unit when common-mode noise is superimposed on the AC power supply of the power-separated LED lighting device, connects the secondary-side ground or the primary-side ground of the DC / DC converter to the conductive part of the LED unit via a first capacitor. Since the first capacitor is a capacitor that connects the secondary-side ground or the primary-side ground of the DC / DC converter to the metal case of the power supply unit, noise current is bypassed through the capacitor to prevent damage to the LED unit due to a decrease in the current of the LED unit.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, as described in paragraphs 0021, 0026, and 0030 of Patent Document 1, since the capacitance of the first capacitor needs to be 1000 pF or more, an increase in leakage current is a concern. The leakage current is 0.1 mA for 1000 pF, 0.33 mA for 2200 pF, and 0.4 mA for 4700 pF (when commercial 242 V, 60 Hz), and a capacitance close to 0.4 mA at which electric shock is felt is required. In practice, it is often selected to be approximately 1000 pF or less considering a margin.

[0006] That is, in the LED lighting device described in Patent Document 1, it is considered necessary to relatively increase the capacitance of the first capacitor to 1000 pF or more, and in that case, there is a problem that it is necessary to separately consider measures against electric shock.

[0007] An object of the present invention is to provide a power supply separate type LED lighting device that does not require measures against electric shock.

Means for Solving the Problems

[0008] The above problems are solved by the following means. (1) A power supply unit including at least a pair of AC input terminals and a pair of DC output terminals, an LED circuit supplied with a DC current via a pair of power supply lines connected to the DC output terminals of the power supply unit, and an LED unit including a conductive portion electrostatically coupled to the LED via a dielectric, An LED lighting device comprising: The power supply unit includes a DC-DC converter circuit, and a power supply separate type LED lighting device characterized in that a common mode inductor is provided between the secondary side of the DC-DC converter circuit and the pair of DC output terminals. (2) A power supply unit including at least a pair of AC input terminals and a pair of DC output terminals, an LED circuit supplied with a DC current via a pair of power supply lines connected to the DC output terminals of the power supply unit, and an LED unit including a conductive portion electrostatically coupled to the LED via a dielectric, An LED lighting device comprising: The power supply unit includes a DC-DC converter circuit, and a common-mode inductor is provided between the secondary side of the DC-DC converter circuit and the pair of DC output terminals. The subsequent stage of the common-mode inductor is connected to the conductive portion of the LED unit via a first capacitor. The first capacitor is a capacitor that connects the common-mode inductor to the metal case of the power supply unit. A power supply-separated type LED lighting device is characterized by this. (3) The power supply-separated type LED lighting device according to item 2 above, characterized in that the capacitance of the first capacitor is 1000 pF or less.

Effect of the Invention

[0009] According to the invention described in item (1) above, since a common-mode inductor is provided between the secondary side of the DC-DC converter circuit included in the power supply unit and the pair of DC output terminals, even if a common-mode noise voltage is applied to the primary side (input side) of the power supply unit, it is possible to suppress the propagation of this noise voltage to the output side of the power supply unit 1. Therefore, it is possible to prevent damage to the LED unit connected via the DC output terminal of the power supply unit and the power line. Also, since a grounding capacitor is not used, no electric shock countermeasures are required.

[0010] According to the invention described in item (2) above, a common-mode inductor is provided between the secondary side of the DC-DC converter circuit included in the power supply unit and the pair of DC output terminals, and the subsequent stage of the common-mode inductor is connected to the conductive portion of the LED unit via a first capacitor. Furthermore, the first capacitor is a capacitor that connects the common-mode inductor to the metal case of the power supply unit. Therefore, a common-mode LC filter is constituted by the common-mode inductor and the first capacitor. Since this common-mode LC filter can suppress the propagation of a common-mode noise voltage applied to the primary side (input side) of the power supply unit to the output side of the power supply unit 1, it is possible to prevent damage to the LED unit.

[0011] Moreover, by configuring a common-mode LC filter, there is also an effect that the inductor for common mode can be simplified, and cost reduction or miniaturization can be achieved.

[0012] In addition, since the common-mode LC filter reduces common-mode noise, it becomes possible to keep the capacitance of the first capacitor relatively small at 1000 pF or less, and there is no need for electric shock countermeasures.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present invention will be described with reference to the drawings. (Embodiment 1) The circuit configuration of the LED lighting device according to Embodiment 1 of the present invention is shown in FIG. 1. The LED lighting device shown in FIG. 1 consists of a separate power supply unit 1 and an LED unit 2, and the two units are connected by three wires, a pair of power lines 3a, 3b and a ground line 4.

[0015] The power supply unit 1 is provided with a pair of AC input terminals 11a, 11b on the input side and a pair of DC output terminals 12a, 12b on the output side. An AC power supply 5 is connected to the AC input terminals 11a, 11b, and for example, a commercial AC voltage of 100 V (50 Hz / 60 Hz) is applied. This AC power supply 5 may have common-mode noise (ground noise voltage) 6 superimposed thereon.

[0016] Inside the metal case 13 of the power supply unit 1, there is a rectifier circuit 14 connected to a pair of AC input terminals 11a and 11b to full-wave rectify the voltage from the AC power supply 5, and a DC-DC converter circuit 15 that power-converts the output voltage of the rectifier circuit 14 and outputs a DC current between the secondary terminals 15a and 15b.

[0017] The DC-DC converter circuit 15 of the present embodiment includes a switching element Q1 that is switched at a high frequency, a transformer T1 with a primary winding connected to a smoothing capacitor C1 via the switching element Q1, a diode D1 connected in series with the secondary winding of the transformer T1 with a polarity that conducts when the switching element Q1 is OFF, and a smoothing capacitor C2 connected to the secondary winding of the transformer T1 via the diode D1, and is a flyback DC-DC converter circuit. Although the control circuit of the switching element Q1 is not shown, for example, it detects the voltage drop of a current detection resistor inserted in series between one inductor L2 of the common-mode inductor 16 described later and the power line 3b, and is configured as a circuit that feedback-controls the ON duty of the switching element Q1 so that the detected value becomes a predetermined value.

[0018] In this DC-DC converter circuit 15, the primary-side circuit connected to the smoothing capacitor C1 and the secondary-side circuit connected to the smoothing capacitor C2 are insulated by the transformer T1, but there are noise-preventing coupling capacitors C3 and C4 between the primary-side ground G1 and the secondary-side ground G2. For this reason, the primary-side ground G1 and the secondary-side ground G2 are coupled at a high frequency at the portion of the coupling capacitors C3 and C4, and the ground noise voltage applied to the primary side of the DC-DC converter circuit 15 may be propagated to the secondary side of the DC-DC converter circuit 15.

[0019] In this embodiment, a common-mode inductor 16 composed of a pair of inductors L1 and L2 is interposed between a pair of output terminals 15a and 15b on the secondary side of the DC-DC converter circuit 15 and a pair of DC output terminals 12a and 12b on the output side of the power supply unit 1. This common-mode inductor 16 serves to prevent the common-mode noise 6 superimposed on the AC power supply 5 from being applied to the input side of the power supply unit 1 and transmitted to the output side of the power supply unit 1 when the noise is propagated to the secondary side of the DC-DC converter circuit 15.

[0020] The LED unit 2 is connected to the DC output terminals 12a and 12b of the power supply unit 1 via a pair of power lines 3a and 3b, is controlled by the DC-DC converter circuit 15, and outputs a DC current that has passed through the common-mode inductor 16. In this embodiment, as wiring between the two units, in addition to the pair of power lines 3a and 3b, a ground line 4 that connects the metal case 13 of the power supply unit 1 and the non-charging conductive portion 21 of the LED unit 2 is provided. This ground line 4 is not limited to a lead wire, and any component that can electrically connect the metal case 13 of the power supply unit 1 to the non-charging conductive portion 21 of the LED unit 2 is acceptable. The non-charging conductive portion 21 of the LED unit 2 is, for example, an aluminum heat sink that also serves as an appliance housing, and although it is not electrically connected to the power lines 3a and 3b, it is electrostatically coupled to each LED chip 22 via a dielectric.

[0021] The LED unit 2 is formed by connecting a plurality of LED chips 22 in series on a wiring board. Since a dielectric sheet, which is an insulator, is disposed between each LED chip 22 and the aluminum heat sink (conductive portion 21) that also serves as the appliance housing, a parasitic capacitance Cy exists between the aluminum heat sink, which is the non-charging conductive portion 21, and each LED chip 22.

[0022] When a pulsed current due to the ground noise voltage flows through this floating capacitance Cy, there is a risk that the LED chip 22 may be damaged. Therefore, in the present embodiment, a common-mode inductor 16 is interposed between the secondary output terminals 15a and 15b of the DC-DC converter circuit 15 and a pair of DC output terminals 12a and 12b on the output side of the power supply unit 1, thereby suppressing the propagation of common-mode noise to the LED unit 2 and preventing the destruction of the LED chip 22.

[0023] In the first embodiment, a ground wire 4 connecting the metal case 13 and the non-charging conductive portion 21 of the LED unit 2 is provided, and the metal case 13 is grounded to the ground. However, the metal case 13 may not be grounded to the ground (even if it floats from the ground).

[0024] In this embodiment, a flyback type DC-DC converter using a transformer T1 is exemplified as the DC-DC converter circuit 15, but the present invention is not limited thereto. For example, a forward type DC-DC converter, a non-isolated type converter, a boost type, a buck type, or a buck-boost type chopper circuit may be used. In short, the present invention can be applied to any circuit configuration that can suppress the propagation of the common-mode noise voltage applied to the primary side (input side) to the secondary side (output side) of the DC-DC converter circuit 15 and to the LED unit 2 side by the common-mode inductor 16.

[0025] As described above, according to the first embodiment, since the common-mode inductor 16 is provided between the secondary side of the DC-DC converter circuit 15 included in the power supply unit 1 and the pair of DC output terminals 12a and 12b, even if a common-mode noise voltage 6 is applied to the primary side (input side) of the power supply unit 1, the propagation of this noise voltage 6 to the output side of the power supply unit 1 can be suppressed. Therefore, it is possible to prevent damage to the LED unit 2. In addition, since a grounding capacitor is not used, no electric shock countermeasures are required. (Second Embodiment) The circuit configuration of the LED lighting device according to Embodiment 2 of the present invention is shown in FIG. 2. In this Embodiment 2, first capacitors C5, C5 for constituting a common-mode LC filter in cooperation with the common-mode inductor 16 are connected. Since the configurations of other DC-DC converter circuits 15, LED units 2, etc. are the same as those in Embodiment 1, their descriptions are omitted.

[0026] In the circuit of FIG. 2, one end of each of a total of two first capacitors C5, C6 is connected to the output sides of the inductors L1, L2 constituting the common-mode inductor 16. Further, the metal case 13 and the non-charging conductive part 21 of the LED unit 2 are connected by the ground wire 4, and the other ends of the first capacitors C5, C6 are connected to the ground wire 4. Therefore, the subsequent stage (output side) of the common-mode inductor 16 is connected to the conductive part 21 of the LED unit 2 via the first capacitors C5, C6. Also, the first capacitors C5, C6 connect the common-mode inductor 16 to the metal case 13 of the power supply unit 1.

[0027] In the LED lighting device according to Embodiment 2, due to the above-described common-mode inductor 16 and first capacitors C5, C6, a state is achieved in which a common-mode LC filter 17 is connected to the secondary side of the DC-DC converter circuit 15. For this reason, even when a common-mode noise voltage 6 is applied to the primary side (input side) of the power supply unit 1, the common-mode LC filter 17 can suppress the propagation of this noise voltage 6 to the output side of the power supply unit 1. Therefore, damage to the LED unit 2 can be prevented.

[0028] Even if some common-mode noise is propagated to the output side of the power supply unit 1, since the non-charging conductive part 21 of the LED unit 2 has the same potential as the metal case 13 via the ground wire 4, it is possible to prevent a noise voltage from appearing between the non-charging conductive part 21 of the LED unit 2 and the power supply lines 3a, 3b. Note that the ground wire 4 and the metal case 13 may be grounded as shown in FIG. 2.

[0029] In addition, by using the first capacitors C5 and C6 to form the common-mode LC filter 17, the common-mode inductor 16 can be simplified, and cost reduction or miniaturization can be achieved.

[0030] Also, compared with the circuit configuration of the LED lighting device in Patent Document 1 that does not use the common-mode inductor 16, the capacitances of the first capacitors C5 and C6 can be kept relatively small, for example, 1000 pF or less. Therefore, no electric shock countermeasures are required.

[0031] In Embodiment 2 shown in FIG. 2, the first capacitors C5 and C6 are connected to the inductors L1 and L2 of the common-mode inductor 16, respectively. However, a configuration in which the first capacitor C5 or C6 is connected to only one of the two inductors L1 and L2 may also be used.

Explanation of Reference Numerals

[0032] 1 Power supply unit 2 LED unit 3a, 3b Power supply lines 4 Ground line 5 AC power supply 6 Common-mode noise 11a, 11b Input terminals 12a, 12b DC output terminals 13 Metal case 14 Rectifier circuit 15 DC-DC converter circuit 15a, 15b Output terminals of the DC-DC converter 16 Common-mode inductor 17 LC filter 21 Conductive part 22 LED chip C1, C2 Smoothing capacitors C3, C4 Coupling capacitors C5, C6 First capacitors Q1 Switching element T1 Transformer D1 Diode

Claims

1. A power supply unit having at least a pair of AC input terminals and a pair of DC output terminals, an LED unit including a circuit of an LED supplied with a DC current via a pair of power lines connected to the DC output terminals of the power supply unit, the LED unit including a conductive portion electrostatically coupled to the LED via a dielectric, An LED lighting device comprising: The power supply unit includes a DC-DC converter circuit, and a common-mode inductor is provided between the secondary side of the DC-DC converter circuit and the pair of DC output terminals. The LED lighting device of the power supply-separated type is characterized in that.

2. A power supply unit having at least a pair of AC input terminals and a pair of DC output terminals, an LED unit including a circuit of an LED supplied with a DC current via a pair of power lines connected to the DC output terminals of the power supply unit, the LED unit including a conductive portion electrostatically coupled to the LED via a dielectric, An LED lighting device comprising: The power supply unit includes a DC-DC converter circuit, and a common-mode inductor is provided between the secondary side of the DC-DC converter circuit and the pair of DC output terminals. The latter stage of the common-mode inductor is connected to the conductive portion of the LED unit via a first capacitor, The first capacitor is a capacitor that connects the common-mode inductor to a metal case of the power supply unit. The LED lighting device of the power supply-separated type is characterized in that.

3. The LED lighting device of the power supply-separated type according to claim 2, characterized in that the capacitance of the first capacitor is 1000 pF or less.

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