JP2014010900A - Power supply device for led illumination - Google Patents

Abstract

An object of the present invention is to provide a power supply device for LED lighting that reduces noise generation without increasing leakage current and the number of components, and has high power efficiency and high safety.
A power supply device for LED lighting according to the present invention includes a DC power supply circuit, a transformer, and an output terminal connected to the LED to be lit, and is connected to the output side of the DC power supply circuit and connected to the LED. A DC-DC conversion circuit that supplies a predetermined DC voltage or a predetermined DC current, the transformer includes a core and a wound coil, and the core has a hollow portion whose outer shape is a substantially circular sphere or a substantially elliptic sphere. And the coil is disposed inside the hollow portion of the substantially circular or elliptical sphere.
[Selection] Figure 1

Description

  The present invention relates to an LED illumination power supply device, and more particularly to an LED illumination power supply device including a transformer.

  2. Description of the Related Art Conventionally, there is known a power supply device that converts an AC voltage of a commercial AC power source into a predetermined DC voltage and lights an LED (Light Emitting Diode) (for example, Patent Document 1). The apparatus described in Patent Document 1 converts a DC power supply circuit that converts an AC voltage of a commercial AC power supply into a DC voltage, and converts the output voltage of the DC power supply circuit into a predetermined DC voltage by an on / off operation of a switching element, and outputs it. A DC-DC conversion circuit is provided. This DC-DC conversion circuit is provided with a transformer, a switching element, and a rectifying / smoothing circuit. A light emitting diode provided in a non-grounded storage portion is connected between the outputs of the DC-DC conversion circuit. A bypass capacitor is connected between the output terminal of the DC-DC conversion circuit and the ground in order to prevent the propagation of noise to the power supply line. In the apparatus of Patent Document 1, by providing this bypass capacitor, noise generated on the secondary side of the DC-DC conversion circuit is bypassed from the output terminal side of the DC-DC conversion circuit to the ground side.

JP 2010-80381 A

  However, in the device described in Patent Document 1, when the capacitance of the bypass capacitor is increased to remove noise, there is a possibility that leakage current from the bypass capacitor increases. Further, since it is necessary to separately provide a bypass capacitor for noise removal, the number of parts constituting the apparatus increases.

  In addition, the device described in Patent Document 1 includes a DC-DC conversion circuit having a transformer. The transformer is usually formed by winding a coil around a core. In a general core such as a ring-shaped core, the magnetic field lines generated from the coil cannot be collected, and the magnetic field lines generated from the coil leak to the outside.

  Due to the magnetic field lines leaking to the outside, conduction noise and radiation noise are generated in peripheral circuits such as a switching circuit arranged around the transformer, causing malfunction of the peripheral circuits. Further, the generation of these noises also reduces the power supply efficiency. In addition, a DC-DC conversion circuit including a DC power supply circuit and a transformer may be used by being housed in a strong metal case for circuit protection. If the magnetic field lines from the coil leak into the metal case, there is a possibility that the voltage of the case becomes high, which causes a safety problem.

  The bypass capacitor described in Patent Document 1 eliminates noise generated on the secondary side of the DC-DC conversion circuit, but is generated on the primary side of the DC-DC conversion circuit due to leakage of magnetic field lines from the coil to the outside. Noise cannot be removed. Moreover, even if the bypass capacitor is provided, the possibility that the magnetic force lines from the coil leak into a component member that covers the transformer, such as a metal case, cannot be excluded.

  Further, particularly when the load is an LED, noise in a low frequency band (150 KHz to 10 MHz) becomes a problem. The LED chip tends to cause noise in the low frequency band, and an external device such as a radio may be damaged by the noise in the low frequency band. Even if the bypass capacitor is provided, it is difficult to sufficiently reduce the noise in the low frequency band.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a power supply device for LED lighting that reduces noise generation and increases power efficiency and safety without increasing leakage current and the number of components.

  The present invention relates to an LED lighting power supply device. In order to achieve the above object, a power supply device for LED lighting according to the present invention has a DC power supply circuit, a transformer, and an output terminal connected to an LED to be lit, and is connected to the output side of the DC power supply circuit. And a DC-DC conversion circuit for supplying a predetermined DC voltage or a predetermined DC current to the LED, the transformer includes a core and a wound coil, and the core has a substantially spherical or elliptical outer shape. A hollow portion of a sphere is included, and the coil is disposed inside the hollow portion of a substantially circular sphere or a substantially elliptic sphere.

  The output terminal of the DC-DC conversion circuit and the LED may be connected directly or indirectly. That is, another component or circuit may be interposed between the DC-DC conversion circuit and the LED. The DC-DC conversion circuit may be a constant voltage drive type or a constant current drive type.

  As an example, the power supply device for LED illumination according to the present invention does not include a Y capacitor. As another example, the power supply device for LED illumination according to the present invention can reduce the capacitor capacity of the Y capacitor even when the Y capacitor is provided.

  A “Y capacitor” is a capacitor that is inserted into a circuit mainly for the purpose of removing noise. The Y capacitor is inserted, for example, between the primary side and FG (Frame Ground), between the primary side GND (Ground) and the secondary side GND, and between the secondary side GND and the metal chassis. .

  The DC power supply circuit includes a filter circuit connected to the output side of the AC power supply and a rectifying / smoothing circuit connected to the output side of the filter circuit, and converts the AC voltage output from the AC power supply into a DC voltage for output. You may do. As an example, the DC-DC conversion circuit includes a snubber circuit for suppressing a rapid voltage increase. For example, the DC power supply circuit and the DC-DC conversion circuit may be configured to be housed in a metal case. The metal case is made of, for example, aluminum, iron, magnesium or the like.

  The transformer of the LED lighting power supply device according to the present invention includes a core and a wound coil, the core has a hollow portion whose outer shape is a substantially circular sphere or a substantially elliptic sphere, and the coil is a substantially spherical or substantially spherical shape. It is arranged inside the hollow part of the elliptical sphere. Therefore, since the entire coil is covered with the core, the magnetic field lines from the coil are less likely to leak to the outside. Further, the shape of a substantially circular sphere or a substantially elliptical sphere suppresses the concentration of unbalanced magnetic flux, thereby avoiding power supply efficiency reduction and core heat generation.

  By making it difficult for magnetic field lines from the coil to leak to the outside, conduction noise and radiation noise generated in peripheral circuits arranged around the transformer are suppressed, and malfunction of the peripheral circuits is also reduced. Moreover, the power supply efficiency is increased by suppressing these noises. Moreover, since it can avoid that the structural member which covers a transformer is charged with the magnetic force line which leaked from the coil, safety | security increases. In addition, as will be described in detail later, noise in a low frequency band (150 KHz to 10 MHz) can be reduced.

  As described above, according to the LED illumination power supply device according to the present invention, it is possible to reduce the generation of noise without increasing the leakage current and the number of components, and to improve the power efficiency and safety of the LED illumination power supply device. Can be realized.

  As described above, according to the LED illumination power supply device of the present invention, it is possible to reduce the generation of noise, so that it is not necessary to insert a Y capacitor for the purpose of noise removal. By configuring a power supply device for LED illumination that does not include a Y capacitor, the number of components can be reduced. Further, even when a Y capacitor is provided, it is not necessary to use a large-capacity capacitor for noise removal. Therefore, the capacitor capacity of the Y capacitor can be reduced as compared with the conventional case. By reducing the capacitor capacity, the leakage current from the capacitor can be reduced.

  DC power supply comprising a filter circuit connected to the output side of the AC power supply and a rectifying / smoothing circuit connected to the output side of the filter circuit, and converting the AC voltage output from the AC power supply into a DC voltage and outputting it. When the circuit is configured, a commercial AC power source can be used as the power source of the apparatus. Even when such a circuit configuration is adopted, as described above, according to the LED illumination power supply device according to the present invention, it is possible to reduce the generation of noise. In this case, it is not necessary to insert a Y capacitor for the purpose of noise removal. Even if a Y capacitor is inserted, it is not necessary to increase the capacitor capacity in order to eliminate noise, so a small-capacitance capacitor can be used. Therefore, leakage current from the capacitor can be reduced.

  In the case where a snubber circuit for suppressing a rapid voltage increase is provided, peripheral components can be protected by suppressing a rapid voltage increase. However, as described above, according to the LED illumination power supply device of the present invention, it is possible to reduce the generation of noise, and therefore it is not necessary to provide a snubber circuit for the purpose of noise reduction. Even when a snubber circuit is provided to protect peripheral components from a sudden voltage rise, it is not necessary to increase the capacitance of the capacitor constituting the snubber circuit in order to reduce noise. Therefore, a small-capacitance capacitor can be used for the snubber circuit, and leakage current from the capacitor can also be suppressed.

  When the DC power supply circuit and the DC-DC conversion circuit are housed in a metal case, the DC power supply circuit and the DC-DC conversion circuit can be protected by the metal case. Even in this case, the magnetic lines of force from the coil are difficult to leak to the outside, so that charging of the metal case can be avoided.

It is an equivalent circuit diagram of the power supply device for LED lighting according to the first embodiment. It is a front view of the core of the transformer in the power supply device for LED lighting according to the first embodiment. (A) It is a top view of the lower hemisphere of the core which concerns on 1st Embodiment. (B) It is a front view of the lower hemisphere of the core which concerns on 1st Embodiment. (A) It is a front view of the core and coil which concern on 1st Embodiment. (B) It is a side view of the core and coil which concern on 1st Embodiment. It is sectional drawing of the core and coil which concern on 1st Embodiment. It is a graph which shows the measurement result of the noise terminal voltage of the power supply device for LED lighting which concerns on 1st Embodiment. It is a graph which shows the measurement result of the noise terminal voltage of the conventional LED lighting power supply device.

[First Embodiment]
Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows an equivalent circuit diagram of the LED illumination power supply device according to the first embodiment. The LED lighting power supply device 1 according to the first embodiment supplies power to an LED load 2 including a plurality of LEDs 66 to cause the LEDs to emit light.

  The LED illumination power supply device 1 includes a DC power supply circuit 6 and a DC-DC conversion circuit 7 that converts a DC voltage output from the DC power supply circuit 6 into a predetermined DC voltage. The LED load 2 is connected to the output side of the DC-DC conversion circuit 7 via a pair of output terminals 3 of the DC-DC conversion circuit 7.

  The LED load 2 is a direct-current light-emitting load that emits light according to a direct-current voltage supplied from the LED lighting power supply device 1 and includes a plurality of white LEDs 66 connected in series.

  The DC power supply circuit 6 is a circuit that converts an AC voltage output from the AC power supply 5 into a DC voltage. The DC power supply circuit 6 includes an input filter circuit 9, a Y capacitor A, and a full-wave rectifying / smoothing and inrush current preventing circuit 11. In the present embodiment, the circuit configuration in the case where the Y capacitor A is provided is described as an example. However, as described in detail later, the Y capacitor A may not be provided.

  The input filter circuit 9 includes two capacitors 14 and 15 connected in parallel and two coils 16 and 17 containing iron cores. A pair of output terminals of the AC power supply 5 are connected to both ends of the capacitor 14 arranged on the input side in the input filter circuit 9. The AC power source 5 is a commercial power source that outputs an AC voltage such as AC 100 V from a pair of output terminals. The input filter circuit 9 can reduce noise generated on the input line from the AC power supply 5.

  On the output side of the input filter circuit 9, a Y capacitor A composed of two capacitors 19 and 20 is connected between the primary side and the FG. A full-wave rectifying and smoothing and inrush current preventing circuit 11 is connected to the output side of the Y capacitor A. The full-wave rectifying smoothing and inrush current preventing circuit 11 includes a diode bridge 21, a thermistor 22, and a smoothing capacitor 24. A pair of input terminals of the diode bridge 21 is connected to a pair of output terminals of the AC power supply 5 via the Y capacitor A and the input filter circuit 9. One output terminal of the diode bridge 21 is connected to the DC-DC conversion circuit 7 via the thermistor 22. The other output terminal of the diode bridge 21 is grounded.

  The smoothing capacitor 24 is connected to one output terminal of the diode bridge 21 via the thermistor 22 and to the other output terminal of the diode bridge 21. The voltage that is full-wave rectified by the diode bridge 21 is smoothed by the smoothing capacitor 24. Further, by providing the thermistor 22, an inrush current is prevented from flowing into the DC-DC conversion circuit 7.

  The DC-DC conversion circuit 7 includes a switching circuit 26, a first snubber circuit 27, a second snubber circuit 28, a transformer 30, a switching controller power supply circuit 35, a half-wave rectifying and smoothing circuit 36, and an output. A filter circuit 37 and a constant voltage circuit 39 are provided to constitute an insulating switching regulator. The DC-DC conversion circuit 7 converts the DC voltage output from the DC power supply circuit 6 into a predetermined DC voltage by supplying the DC voltage output from the DC power supply circuit 6 to the transformer 30 via the switching element 46. Then, the converted DC voltage is supplied to the LED load 2.

  The switching circuit 26 includes a switching element 46 and a switching control unit 41 that controls on / off of the switching element 46. In the present embodiment, the switching element 46 is a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). The output terminal of the switching control unit 41 is connected to the gate terminal of the switching element 46 through resistors 42 and 44 connected in series and a diode 43 connected in parallel to the resistor 42. Driving power is supplied to the switching control unit 41 from a switching control unit power supply circuit 35 described later. A series circuit composed of two resistors 47 and 48 is connected between the drive power supply line and the output line of the diode bridge 21.

  The switching control unit 41 includes a reference voltage source (not shown), an error amplifier circuit, a comparator, a triangular wave generator, and the like, and generates an H level or L level control signal based on a feedback signal from a constant voltage circuit 39 described later. The control signal is output to the switching element 46 so that the switching element 46 is controlled by PWM (Pulse Width Modulation).

  The first snubber circuit 27 includes a series circuit composed of a diode 53 and a resistor 51, and a capacitor 52 connected in parallel to the resistor 51 between the series connection point of the series circuit and the output line of the diode bridge 21. The series circuit including the diode 53 and the resistor 51 is connected to the drain terminal of the switching element 46. The second snubber circuit 28 includes a series circuit including a resistor 55 and a capacitor 56, and this series circuit is connected in parallel to the switching element 46 and a resistor 49 connected to the source terminal of the switching element 46. The first snubber circuit 27 and the second snubber circuit 28 absorb a transient high voltage generated in accordance with the on / off control of the switching element 46, thereby preventing the switching element 46 and peripheral electronic components from being damaged.

  The transformer 30 includes a primary winding 31 and a secondary winding 32, and an auxiliary winding 33 provided in a switching control unit power circuit 35 described later. One end of the primary winding 31 is connected to the output terminal of the diode bridge 21, and the other end of the primary winding 31 is connected to the drain terminal of the switching element 46. One end of the secondary winding 32 is connected to the anode terminal of the diode 61 in the half-wave rectifying and smoothing circuit 36, and the other end is grounded.

  The half-wave rectifying / smoothing circuit 36 includes a diode 61 and a smoothing capacitor 62. The cathode terminal of the diode 61 is connected to the anode terminal of the LED load 2 via the output filter circuit 37. One end of the smoothing capacitor 62 is connected to the cathode terminal of the diode 61. The other end of the smoothing capacitor 62 is connected to the other end of the secondary winding 32. In addition, the cathode terminal of the LED load 2 is connected via an output filter circuit 37 including a normal mode choke coil 63 and a smoothing capacitor 64. And grounded.

  In a period in which the switching element 46 is turned on by the control signal output from the switching control unit 41, a direct current flows from the diode bridge 21 to the primary winding 31 and the switching element 46. During the period when the switching element 46 is off, a winding voltage is generated at both ends of the secondary winding 32.

  Since the switching element 46 is turned on and off by the switching control unit 41, an alternating voltage is generated at both ends of the secondary winding 32. This AC voltage is half-wave rectified and smoothed by the half-wave rectifying / smoothing circuit 36 and converted into a predetermined DC voltage. The predetermined DC voltage is applied to the LED load 2 via the output filter circuit 37. The output filter circuit 37 reduces noise generated on the connection line between the half-wave rectifying / smoothing circuit 36 and the LED load 2.

  The capacitor B is inserted between the primary side GND and the secondary side GND of the DC-DC conversion circuit 7 and functions as a Y capacitor. In the present embodiment, as an example, a circuit configuration in the case of including a capacitor B that functions as a Y capacitor has been described. However, as will be described in detail later, in the present invention, the capacitor B functioning as a Y capacitor may not be provided.

  Further, in FIG. 1, a capacitor C functioning as a Y capacitor is clearly shown between the secondary side GND and the metal case 80 for explanation. However, as described in detail later, in the present invention, the capacitor C functioning as a Y capacitor may not be provided.

  The constant voltage circuit 39 monitors the fluctuation of the DC voltage applied to the LED load 2 and feeds it back to the switching control unit 41. One end of the constant voltage circuit 39 is connected to a connection line between the diode 61 and the LED load 2, and the other end of the constant voltage circuit 39 is connected to the switching control unit 41 via a photocoupler 76. The constant voltage circuit 39 includes a voltage detection circuit unit and a feedback unit that feedbacks the detected voltage information to the switching element 46. The voltage detection circuit unit includes resistors 67, 71, 73, a capacitor 72 connected in series to the resistor 71, and a diode 68 connected between the resistor 71 and the resistor 67. The feedback unit includes resistors 75 and 77 connected in series and a photocoupler 76 connected in parallel to the resistor 75.

  The constant voltage circuit 39 detects a DC voltage applied to the LED load 2 by the voltage detection circuit unit, and uses the signal indicating the DC voltage value as a feedback signal as a feedback signal via the photocoupler 76 of the feedback unit. Output to. As described above, the switching control unit 41 generates an H-level or L-level control signal based on the feedback signal from the constant voltage circuit 39, and PWM-controls the switching element 46 with this control signal. Therefore, a stable DC voltage can be supplied to the LED load 2.

  As described above, the switching control unit power supply circuit 35 is a circuit that supplies the switching control unit 41 with drive power for on / off control of the switching element 46. The switching control unit power supply circuit 35 includes a half-wave rectifying / smoothing circuit including a diode 58 and a smoothing capacitor 57, an auxiliary winding 33 of the transformer 30, and a resistor 59. One end of the auxiliary winding 33 is connected to the anode terminal of the diode 58 via the resistor 59, and the cathode terminal of the diode 58 is connected to the smoothing capacitor 57 and the voltage input terminal of the switching control unit 41. The other end of the auxiliary winding 33 is connected to the smoothing capacitor 57 and the ground terminal of the switching control unit 41.

  A winding voltage is generated in the auxiliary winding 33 while the switching element 46 is off. The smoothing capacitor 57 is charged by the winding voltage generated from the auxiliary winding 33. The voltage across the smoothing capacitor 57 is supplied to the switching control unit 41 as a drive voltage.

  The primary winding 31, the secondary winding 32, and the auxiliary winding 33 (illustrated by a two-dot chain line enclosure) provided in the transformer 30 described above are covered with a substantially spherical core. Below, the core which comprises the transformer 30 is explained in full detail.

  FIG. 2 is a front view of the core 100 used in the transformer 30 of the LED illumination power supply device 1 according to the first embodiment. As shown in FIG. 2, the core 100 has a hollow portion 102 whose outer shape is a substantially circular sphere, and the hollow portion 102 of the substantially circular sphere defines a space 101 inside thereof. The inner surface of the hollow portion 102 that defines the space 101 is substantially a sphere along the outer shape of the hollow portion 102. The core 100 includes a shaft portion 104 formed continuously with the inner surface of the hollow portion 102 inside the hollow portion 102. The shaft portion 104 is provided along the central axis X1 of a substantially circular sphere. Therefore, the shaft portion 104 is accommodated in the space 101 inside the hollow portion 102. The core 100 is formed using, for example, ferrite powder, iron dust, permalloy molybdenum powder, silicon steel plate, or the like.

  Further, the core 100 is divided into two equal parts along a dividing surface S1 that intersects the shaft portion 104 perpendicularly. 3A and 3B are a top view and a front view, respectively, of the lower hemisphere of the core 100 divided into two equal parts. The core 100 divided into two equal parts has a substantially hemispherical hollow portion 102b. The hollow portion 102 of the core 100 that is not divided is provided with two through holes 105 (FIG. 2) penetrating from the inside to the outside. The through hole 105 is provided so as to cut out a part of the dividing surface S1. As a result, the first and second cutout portions 105a and 105b are formed on the split surface S1 in the pair of hemispheres of the core 100 divided into two equal parts.

  In the present embodiment, the winding is wound around the core 100 via the bobbin 110. FIG. 4A shows a front view of the bobbin 110 and the core 100 wound with the winding, and FIG. 4B shows a side view of the bobbin 110 and the core 100 wound with the winding. About the core 100, the divided | segmented substantially hemispherical hollow parts 102a and 102b are shown.

  The wire forming the coil is wound around a cylindrical bobbin shaft formed at the center of the bobbin 110. First and second flanges 112a and 112b are provided at both upper and lower ends of the bobbin shaft so that the wound coil does not fall off from both ends of the bobbin shaft by the first and second flanges 112a and 112b. It has become.

  The bobbin 110 includes a terminal support plate 114 extending in a direction perpendicular to the bobbin axial direction. The terminal support plate 114 is provided at the axial center of the bobbin shaft, and the length in the longitudinal direction (the length of the end portion of the terminal support plate 114 shown in FIG. 4B) is longer than the diameter of the core 100, The length in the short direction (the length of the end portion of the terminal support plate 114 shown in FIG. 4A) is shorter than the length in the longitudinal direction of the through hole 105. Terminals 115 protrude from both ends of the terminal support plate 114 in the longitudinal direction along the short direction.

  Coils corresponding to the primary winding 31, secondary winding 32, and auxiliary winding 33 of the transformer 30 are formed on the bobbin shaft. In the bobbin shaft divided into an upper part and a lower part by the terminal support plate 114, the primary winding 31 is wound on the upper part to form the primary coil 111a, and the secondary winding 32 is wound on the lower part to form the secondary coil. 111b is formed. In the present embodiment, the auxiliary winding 33 is wound around the primary coil 111a to form an auxiliary coil (not shown).

  After winding the primary winding 31, the secondary winding 32, and the auxiliary winding 33, the tape is wound from above the primary coil 111a, the auxiliary coil, and the secondary coil 111b, and the bobbin 110 in this state is immersed in an impregnating material. Then, the impregnating material is cured by applying a temperature. Thereby, the primary coil 111a, the auxiliary coil, and the secondary coil 111b are fixed to the bobbin shaft. Further, both ends of the primary coil 111a, the auxiliary coil, and the secondary coil 111b are soldered to terminals and electrically connected.

  The bobbin 110 to which the coil is fixed is attached inside the core 100. FIG. 5 shows a cross-sectional view of the core 100 to which the bobbin 110 is attached. The central axis of the bobbin shaft 116 coincides with the central axis X1 of the core 100. A through hole is formed in the center of the bobbin shaft 116, and first and second openings 117a and 117b are formed in the first and second flanges 112a and 112b. A through-hole formed at the center of the bobbin shaft 116 is shaped to fit with the shaft portion 104 of the core 100.

  The shaft portion 104 protruding from the lower hemisphere of the core 100 is inserted into the through hole of the bobbin shaft 116 through the second opening 117b, and the notch portion 105a in which both end portions in the longitudinal direction of the terminal support plate 114 form the through hole 105. , 105b, the bobbin is attached to the core 100. Thereafter, the shaft portion 104 protruding from the upper hemisphere of the core 100 is inserted into the through hole of the bobbin shaft 116 through the first opening 117a. As a result, the bobbin 110 in which the coil is formed is accommodated inside the substantially spherical core 100, and the terminals 115 projecting from both longitudinal ends of the terminal support plate 114 are connected to the core 100 via the through holes 105. Can be exposed to the outside.

  According to the core 100 which concerns on 1st Embodiment, since the whole coil is covered with the core 100, the magnetic force line L1 becomes difficult to leak outside. As shown in FIG. 5, the lines of magnetic force L1 from the primary coil 111a, the secondary coil 111b, and the auxiliary coil are generated along a substantially circular outer shape. In this way, the magnetic lines of force L1 are collected inside the core 100, so that the magnetic lines of force L1 can be prevented from leaking to the outside of the core 100.

  Further, when the hollow portion 102 of the core 100 is formed in an angular shape such as a rectangular parallelepiped, magnetic flux concentrates on the corner, leading to a core loss, reducing power supply efficiency and increasing heat generation of the core 100. Since the core 100 according to the first embodiment has a substantially circular hollow portion 102 having no corners, concentration of unbalanced magnetic flux is suppressed, and a reduction in power supply efficiency and heat generation of the core 100 can be avoided. .

  The core 100 to which the coil is attached can be mounted on the coil mounting substrate 120. The coil mounting substrate 120 is provided with a circular coil mounting opening 121. The core 100 is fitted into the coil mounting opening 121 and supported by the periphery of the coil mounting opening 121. As a result, the core 100 having a substantially spherical outer shape can be stably mounted on the coil mounting substrate 120. The transformer 30 mounted on the coil mounting substrate 120 is housed in a metal case 80 (FIG. 1) together with other circuit configurations of the DC-DC conversion circuit 7 and the DC power supply circuit 6.

  Next, the operation of the LED illumination power supply device 1 according to the first embodiment will be described. The AC voltage output from the commercial AC power supply 5 is converted into a DC voltage by the DC power supply circuit 6. The DC voltage output from the DC power supply circuit 6 is input to the DC-DC conversion circuit 7 and supplied to the transformer 30 via the switching element 46 that is on / off controlled. The winding voltage generated in the secondary winding 32 of the transformer 30 is converted into a DC voltage by the DC-DC conversion circuit 7 and supplied to the LED load 2. As described above, since the on / off of the switching element 46 is controlled based on the feedback signal from the constant voltage circuit 39, a stable DC voltage can be supplied to the LED load 2.

  Further, in the LED illumination power supply device 1 according to the first embodiment, as described above, the coil of the transformer 30 is covered by the core 100 including the hollow portion 102 of a substantially circular sphere, and therefore, the magnetic lines of force L1 from the coil. (FIG. 5) does not leak into the peripheral case such as the switching circuit 26 arranged around the transformer 30 and the metal case 80 (FIG. 1) that houses the transformer 30.

  In the LED illumination power supply device 1 according to the first embodiment, the transformer 30 includes the core 100 described above, so that the generation of noise can be significantly reduced. FIG. 6 is a graph showing the measurement result of the noise terminal voltage of the LED illumination power supply device 1 according to the first embodiment. FIG. 7 shows the measurement results of the noise terminal voltage of the conventional LED illumination power supply device. A general conventional ring-shaped core is used for the transformer of the conventional power supply device for LED lighting. 6 and 7, the horizontal axis indicates the frequency [Hz], and the vertical axis indicates the noise level [dBμV]. In the measurements shown in FIGS. 6 and 7, a 100 V, 50 Hz AC power source is used as the power source.

  In some cases, a power factor correction (PFC) circuit is mounted on the power supply device. When this power factor correction circuit is installed, noise is likely to occur. In the measurement shown in FIG. 6, the power factor correction circuit is mounted on the LED lighting power supply device 1, and the measurement is performed under conditions where noise is more likely to occur. The load in the measurement of FIG. 6 is 40 W, and the load in the measurement of FIG. 7 is 20 W.

  In the graphs of FIGS. 6 and 7, the limit values of the quasi-peak value (Limit 1: QP) and the average value (Limit 2: AV) in the noise standard are displayed together with the measurement results. As is apparent from a comparison of the graphs of FIG. 6 and FIG. 7, the noise level of the LED illumination power supply device 1 according to the first embodiment is significantly lower than that of the conventional LED illumination power supply device. And even if the power supply device 1 for LED lighting according to the first embodiment is equipped with a power factor correction circuit as shown in FIG. 6, the limit value of noise standard (Limit 1: QP, Limit 2: AV) In addition to satisfying the above condition, this margin has a sufficient margin.

  In addition, when the load is an LED, as described above, noise in the low frequency band (150 KHz to 10 MHz) is particularly problematic, but it is difficult to take a countermeasure. However, as shown in the graph of FIG. 6, according to the LED illumination power supply device 1 according to the first embodiment, the noise terminal voltage in the low frequency band is reduced. Compared with the measurement results shown in FIG. 7, noise removal of 20 to 30 dBμV or more is achieved in the low frequency band by the LED illumination power supply device 1 according to the first embodiment. As a result, the influence of noise on an external device such as a radio can be extremely reduced.

  As described above, in the LED illumination power supply device 1 according to the first embodiment, since the generation of noise is suppressed, it is not necessary to insert the capacitors B and C functioning as the Y capacitor A and the Y capacitor. Further, as shown in FIG. 1, as an example, even when the capacitors B and C functioning as the Y capacitor A and the Y capacitor are inserted, it is not necessary to increase the Y capacitance in order to remove noise. The leakage current can be extremely reduced. As an example, the capacitance of the capacitor constituting the Y capacitor A can be reduced from 2200 pF to 220 pF, that is, 1/10. Similarly, capacitors B and C can be capacitors having a small capacity.

  The first snubber circuit 27 and the second snubber circuit 28 are provided in order to suppress a rapid voltage rise and protect peripheral components, but as a result, also serve to remove noise. However, since the transformer 30 includes the core 100 having the substantially spherical hollow portion 102, sufficient noise removal is realized. Therefore, also in the first snubber circuit 27 and the second snubber circuit 28, There is no need to increase the capacitance of the capacitors 52 and 56 constituting the circuit. Therefore, the capacitors 52 and 56 having a small capacity can be used for the first snubber circuit 27 and the second snubber circuit 28.

  In addition, when other components or designs can protect peripheral components from sudden voltage rise, both the first snubber circuit 27 and the second snubber circuit 28 are connected to the LED lighting power source. You may delete from the apparatus 1. FIG. This is because it is not necessary to install a snubber circuit for the purpose of noise removal.

  As described above, the LED lighting power supply device 1 according to the first embodiment reduces noise generation without increasing the leakage current and the number of components, and realizes high power efficiency and high safety. doing.

[Other Embodiments]
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications and changes can be made based on the technical idea of the present invention. For example, in the LED illumination power supply device 1 according to the first embodiment, the outer shape of the hollow portion 102 of the core 100 is substantially a sphere, but is not limited thereto. For example, the outer shape of the hollow portion 102 of the core 100 may be a substantially elliptical sphere. Depending on the generated magnetic field lines L1, the one that further matches the shape of the magnetic field lines L1 can be selected.

  In the LED illumination power supply device 1 according to the first embodiment, the constant voltage drive is executed using the constant voltage circuit 39, but the present invention is not limited to this. For example, instead of the constant voltage circuit 39, a constant current circuit may be provided to execute constant current driving. In this case, the constant current circuit may be configured to detect a current flowing through the LED load 2 and transmit a signal indicating the detected current value to the switching control unit 41 as a feedback signal. The switching control unit 41 may be configured to on / off control the switching element 46 so that the DC-DC conversion circuit 7 outputs a predetermined direct current to the LED load 2.

DESCRIPTION OF SYMBOLS 1 LED illumination power supply device 2 LED load 3 DC-DC conversion circuit output terminal 6 DC power supply circuit
7 DC-DC conversion circuit 9 Input filter circuit 11 Full-wave rectification smoothing and inrush current prevention circuit 27 First snubber circuit 28 Second snubber circuit
30 transformer 80 metal case 100 core 102 hollow part

Claims (6)

A DC power supply circuit;
A DC-DC conversion circuit having a transformer and an output terminal connected to the LED to be lit, connected to the output side of the DC power supply circuit, and supplying a predetermined DC voltage or a predetermined DC current to the LED; With
The transformer includes a core and a wound coil, and the core has a hollow portion whose outer shape is a substantially circular sphere or a substantially elliptic sphere, and the coil is the hollow of the substantially sphere or the substantially elliptic sphere. A power supply device for LED lighting, which is disposed inside the unit.   The LED lighting power supply device according to claim 1, wherein no Y capacitor is provided.   2. The LED illumination power supply device according to claim 1, wherein even if a Y capacitor is provided, the capacitor capacity of the Y capacitor can be reduced.   The DC power supply circuit includes a filter circuit connected to the output side of the AC power supply and a rectifying / smoothing circuit connected to the output side of the filter circuit, and converts the AC voltage output from the AC power supply into a DC voltage. The LED illumination power supply device according to any one of claims 1 to 3, wherein the LED illumination power supply device is output in the same manner.   5. The LED illumination power supply device according to claim 1, wherein the DC-DC conversion circuit includes a snubber circuit for suppressing a rapid voltage increase.   6. The LED illumination power supply device according to claim 1, wherein the DC power supply circuit and the DC-DC conversion circuit are housed in a metal case.

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