JP2022131188A - Power supply device and illumination device - Google Patents

Abstract

To provide a power supply device including a switching element and capable of reducing a noise, and an illumination device including the power supply device.SOLUTION: In an illumination device 10, a power supply device 12 comprises: a power conversion circuit 19 including a switching element Q1 and converting an input power to a prescribed DC power; a composite-type line filter 21 connected to an input unit of the power conversion circuit 19 and having a section in which an impedance peak is a frequency of less than 30 MHz; and a normal mode choke L1 connected to the input unit of the power conversion circuit 19 and having a characteristic for reducing a noise of a low frequency region of less than 30 MHz.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD Embodiments of the present invention relate to a power supply device having a switching element and a lighting device provided with this power supply device.

2. Description of the Related Art Conventionally, for example, a lighting device uses a power supply device that includes a power conversion circuit that converts input power into predetermined DC power using a switching element in order to turn on a light source. In this power supply device, a noise filter is provided in the input wiring connected to the input section of the power conversion circuit in order to reduce noise generated from the switching element or the like.

Since it takes time and effort to provide a noise filter in the input wiring, it is desired that noise can be reduced without providing a noise filter in the input wiring.

JP 2016-162596 A

A problem to be solved by the present invention is to provide a power supply device and a lighting device capable of reducing noise.

A power supply device of an embodiment includes a power conversion circuit that has a switching element and converts input power into a predetermined DC power, a composite line filter with a section connected to an input part of the power conversion circuit, and a power conversion circuit. a normal mode choke connected to the input of the

According to the power supply device of the embodiment, noise can be expected to be reduced.

1 is a circuit diagram of a lighting device including a power supply device according to an embodiment; FIG. 4 is a graph showing the relationship between frequency and impedance of a line filter of the same power supply device; It is the graph which expanded a part of FIG. 2 same as the above. It is a front view of a board|substrate of a power supply device same as the above. 4 is a table showing characteristics of the same line filter;

An embodiment will be described below with reference to the drawings.

As shown in FIG. 1, the illumination device 10 includes a light source 11 and a power supply device 12 that inputs electric power from an AC power source E, which is an external power source, to light the light source 11 .

The light source 11 uses, for example, a light-emitting diode (LED), which is a semiconductor light-emitting element. In addition to the light-emitting diode, other semiconductor light-emitting elements such as organic EL may be used. Further, the light source 11 may be configured integrally with the power supply device 12, for example, or may be configured by a light source unit detachable from the fixture body, and electrically connected to the power supply device 12 when the light source unit is attached to the fixture body. It may be configured to be

The power supply device 12 also includes a noise prevention circuit 15 , a rectifier circuit 16 , and a power conversion circuit 19 including a power factor correction circuit 17 and a constant current circuit 18 .

The noise prevention circuit 15 includes a capacitor C1 connected to both ends of an AC power supply E such as a commercial AC power supply, a pair of normal mode chokes L1 connected to both ends of the capacitor C1, and a pair of normal mode chokes L1. and a composite line filter 21 to which the input end of is connected.

The normal mode choke L1 is a choke coil that mainly reduces noise of normal mode components, and has characteristics of reducing noise in a low frequency range of, for example, less than 30 MHz.

The composite type line filter 21 is a so-called composite type (or hybrid type) with a section that corresponds to noise reduction in a wide range from high frequency to low frequency, and the inductance value of the common mode component and the normal mode It is a common-mode/normal-mode composite choke coil that has both component inductance values.

As shown by solid lines in the graphs of FIGS. 2 and 3, the composite line filter 21 has an impedance peak at a frequency of less than 30 MHz. Since it is 7 pF or less, it has a characteristic of effectively reducing noise in a high frequency range of 30 MHz or higher.

The rectifier circuit 16 is a full-wave rectifier circuit that performs full-wave rectification of the AC voltage from the AC power source E. A pair of input terminals are connected to a pair of output terminals of the composite line filter 21, and the noise prevention circuit 15 It is connected to an AC power supply E via the . A pair of output terminals of the rectifier circuit 16 are connected to a capacitor C2. The rectifier circuit 16 and the capacitor C2 constitute a full-wave rectifier circuit, which rectifies the AC voltage input from the AC power supply E through the noise prevention circuit 15, and smoothes the high-frequency voltage by the power factor correction circuit 17 in the subsequent stage. to convert to a full-wave rectified waveform.

The power factor correction circuit 17 is configured by a boost chopper circuit that boosts the rectified and smoothed DC voltage to improve the power factor. The power factor correction circuit 17 includes a series circuit of an inductor L2 and a switching element Q1 connected across the capacitor C2, and a series circuit of a diode D1 and a capacitor C3 connected in parallel across the switching element Q1. there is

A MOS-FET, which is a field effect transistor, is used as the switching element Q1. It is connected to a control circuit that controls Q1.

The constant current circuit 18 is composed of a step-down chopper circuit that steps down the DC voltage boosted by the power factor correction circuit 17 to a predetermined voltage necessary for lighting the light source 11 and makes the current constant. Constant current circuit 18 includes a series circuit of switching element Q2 and diode D2 connected across capacitor C3, and a series circuit of inductor L3 and capacitor C4 connected across diode D2. A light source 11 is connected across the capacitor C4.

A field effect transistor such as a MOS-FET is used as the switching element Q2, the drain is connected to the connection point between the cathode of the diode D1 and the capacitor C3, and the source is connected to the connection point between the cathode of the diode D2 and the inductor L3. and its gate is connected to a control circuit that controls the switching element Q2.

4 also shows a substrate 30 of the power supply device 12. As shown in FIG. A noise prevention circuit mounting area A for mounting the noise prevention circuit 15 is provided adjacent to the input connector CN1 in the power supply input portion of the substrate 30 . A capacitor C1, a pair of normal mode chokes L1, and a composite line filter 21 are mounted in this noise prevention circuit mounting area A. FIG.

Next, the operation of the power supply device 12 will be described.

When the AC power supply E is turned on, the AC voltage is input to the rectifier circuit 16 through the noise prevention circuit 15, and the AC voltage is rectified by the rectifier circuit 16 and smoothed by the capacitor C2. It is supplied to the power factor correction circuit 17 .

In the power factor correction circuit 17, the switching element Q1 is turned on and off at a predetermined switching frequency by the control circuit, and the rectified and smoothed DC voltage is stepped up to a predetermined voltage. The boosted DC voltage is smoothed by the capacitor C3 and supplied to the constant current circuit 18 .

In the constant current circuit 18, the switching element Q2 is turned on and off at a predetermined switching frequency by the control circuit, and the DC voltage output from the power factor correction circuit 17 is stepped down to a predetermined voltage and made constant current. This constant current DC voltage is supplied to the light source 11, and the light source 11 is lit.

Also, the noise generated mainly by the switching element Q1 of the power conversion circuit 19 is reduced by the capacitor C1, the normal mode choke L1 and the composite line filter 21 of the noise prevention circuit 15. FIG.

As shown by solid lines in the graphs of FIGS. 2 and 3, the composite line filter 21 has an impedance peak at a frequency of less than 30 MHz. Since it is 7 pF or less, it has a characteristic of effectively reducing noise in a high frequency range of 30 MHz or higher.

The dashed lines in the graphs of FIGS. 2 and 3 show the characteristics of the composite line filter of the comparative example (hereinafter referred to as the line filter of the comparative example).

The composite line filter 21 and the line filter of the comparative example are different in coil size, number of turns, L value and inter-line capacitance. Line-to-line capacitance occurs because the coil windings are covered with an insulator, and the insulation intervenes between the windings, creating the same structure as a capacitor. When there are many, the line-to-line capacitance becomes large. The line-to-line capacitance has little effect in the low frequency range, but in the high-frequency range, the larger the line-to-line capacitance is, the more leakage current increases and the impedance decreases.

The composite line filter 21 has a smaller coil size, a smaller number of turns, and a smaller L value and line-to-line capacitance than the line filter of the comparative example.

Therefore, compared with the line filter of the comparative example, the composite line filter 21 has an impedance peak at a high frequency, a high impedance in a frequency range (including 30 Hz or higher) from the impedance peak, and a low frequency from the impedance peak. It has the characteristic that the impedance in the range is low. Therefore, the composite line filter 21 has an impedance value of 1 kΩ or more at 30 MHz and a line-to-line capacitance of 7 pF or less. It has excellent characteristics for reducing

In the table of FIG. 5, the line filter of the comparative example, the composite line filter 21, and the high-frequency line filter having the impedance peak at a frequency of 30 Hz or higher as the second comparative example show the impedance peak parallel resonance Frequency f ₀ , inductance L, line capacitance Cp are shown.

The parallel resonance frequency _f0 is generated by the line-to-line capacitance Cp and by the resonance of the inductor and the capacitor. The parallel resonance frequency _f0 is expressed by the following equation.

The line-to-line capacitance Cp can be obtained from the parallel resonance frequency _f0 and is expressed by the following equation.

In addition, since the composite line filter 21 has excellent characteristics for reducing noise in the high frequency range of 30 MHz or higher, the effect of reducing noise in the low frequency range is reduced. Noise in the frequency range can be reduced, and the noise reduction effect can be complemented.

In addition, the Electrical Appliance and Material Safety Law stipulates noise limit values for noise terminal voltage at 5 kHz to 30 MHz, radiated electric field strength at 30 MHz to 30 MHz, and radiated magnetic field strength at 9 kHz to 30 MHz. The combined use of L1 and the composite line filter 21 can suppress the noise level to a value lower than each limit value in a wide range.

As described above, in the power supply device 12 of the present embodiment, the impedance peak at the input portion of the power conversion circuit 19 is at a frequency of less than 30 MHz, but the impedance value at 30 MHz is 1 kΩ or more and the line capacitance is 7 pF or less. Because of the combination of a composite line filter 21 that effectively reduces noise in a high frequency range of 30 MHz or higher and a normal mode choke L1 that reduces noise in a low frequency range, a wide range of Noise can be reduced.

Moreover, since the composite line filter 21 used here is smaller in size than the line filter of the comparative example, the normal mode choke can be achieved in the limited space of the noise prevention circuit mounting area A of the substrate 30. A space for mounting L1 can be provided, and wide-area noise reduction can be achieved without increasing the size of the substrate 30 .

The power supply device 12 can reduce noise by using it in the lighting device 10, but it can also be used in other electric devices.

While several embodiments of the invention have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the scope of the invention described in the claims and equivalents thereof.

REFERENCE SIGNS LIST 10 lighting device 12 power supply device 19 power conversion circuit 21 line filter L1 normal mode choke Q1 switching element

Claims (4)

a power conversion circuit that has a switching element and converts input power into predetermined DC power;
a composite line filter with sections connected to the input of the power conversion circuit;
a normal mode choke connected to the input of the power conversion circuit;
A power supply device comprising: 2. The power supply device according to claim 1, wherein the line filter has an impedance peak at a frequency of less than 30 MHz and an impedance value of 1 k[Omega] or more at 30 MHz. 3. The power supply device according to claim 1, wherein the line filter has an impedance peak at a frequency of less than 30 MHz and a line-to-line capacitance of 7 pF or less. A lighting device comprising the power supply device according to any one of claims 1 to 3.

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