JP5916390B2 - Power supply unit and LED lighting device using the same - Google Patents

Description

  The present invention relates to a power supply unit and an LED lighting device using the power supply unit.

  Patent Literature 1 discloses an LED lighting apparatus including a power supply unit that receives an input from an AC power supply and an LED unit that is connected to the power supply unit via wiring. The power supply unit of the reference example is composed of a flyback DC / DC converter, has a detection resistor for detecting an output current on the secondary side of the converter, and the switching element on the primary side of the converter is PWM-controlled so that the detection voltage is constant. .

  Patent Document 2 discloses a lighting fixture in which a power supply unit that receives input from an AC power supply and an LED unit are integrated. The power supply unit of the reference also includes a flyback type DC / DC conversion circuit, and the low-potential side output terminal of the DC / DC conversion circuit is connected to the case of the power supply unit via a bypass capacitor. Grounded.

JP 2010-198761 A JP 2010-80381 A

  By the way, in the LED lighting apparatus using a power supply unit like patent document 1 and 2, it is necessary to cope with various noise problems. For example, it is necessary to take measures against common mode noise (ground noise) from an AC power supply. This is because common mode noise (pulse voltage) is propagated to the LED element, and the LED element is destroyed when the pulse voltage exceeds the withstand voltage of the LED element. Further, it is necessary to prevent the switching noise generated from the DC / DC converter of the power supply unit, in particular, normal mode noise (line-to-line noise) from being propagated to the power supply line. That is, it is necessary to suppress the influence on other electronic devices connected to the same AC power source by setting the noise terminal voltage and the noise power to the reference value or less.

  Here, in the device of Patent Document 1, noise countermeasures are taken by the filter circuit of the input unit, but the above various noise problems cannot be sufficiently dealt with only by the input filter circuit. On the other hand, in the apparatus of Patent Document 2, countermeasures are taken against common mode noise that can be propagated from the AC power supply to the LED unit side and switching noise that can be propagated from the power supply unit to the AC power supply side. Specifically, common mode noise from an AC power supply is bypassed to a grounding point via a power supply unit housing by a bypass capacitor, and the LED unit is integrated with the power supply unit, so that common mode noise is generated by the LED element. Never reach. Further, since the switching noise from the DC / DC converter is also bypassed to the ground point via the casing of the power supply unit by the bypass capacitor, the switching noise is not propagated to the AC power supply side. In particular, the larger the capacitance of the bypass capacitor, the more effective the countermeasures against common mode noise and switching noise.

  However, since the casing constituting the power supply unit is made of metal, it becomes a kind of antenna and may pick up radiation noise from the LED unit. In addition, in the case of an LED lighting device with separate power supply, such as the device of Patent Document 1, it is necessary to consider radiation noise from a cable connecting the power supply unit and the LED unit. In particular, when the bypass capacitor is increased in capacity in anticipation of an increase in the bypass effect of common mode noise, the pulse noise superimposed on the wiring in the power supply unit increases from the radiation noise, and this superimposed pulse noise is generated by the DC / DC converter. May cause the control circuit to malfunction. More specifically, when radiation noise from the LED element enters the control circuit of the DC / DC converter of the power supply unit and is mounted on the small signal wiring, the output operation of the DC / DC converter (for example, PWM for constant current) Control) is not properly performed, a protective operation (for example, a light-off operation) is unnecessarily induced, and conversely, a necessary protective operation is not performed.

Then, this invention makes it a subject to provide the power supply unit which solves the problem of said common mode noise, switching noise, and radiation noise, and an LED lighting apparatus using the same,
In particular, it is an object to prevent malfunction of the power supply unit due to radiation noise. In the following description of the present specification, the output operation and the protection operation contrary to the design purpose as described above are collectively referred to as malfunctions.

  The first aspect of the present invention is a power supply unit for lighting an LED. The power supply unit consists of a metal casing having an AC input section, a DC output section to which the LED element is connected, and a grounding terminal. The metal casing converts the AC input from the AC input section into DC. A direct current conversion circuit, a pair of output lines connecting the output node of the direct current conversion circuit and the direct current output unit, a control circuit for controlling the direct current conversion circuit, a first capacitor in which one node is a pair of the output lines A first capacitor connected to at least one of the output lines and having the other node connected to the metal casing; and an output node of the DC converter circuit and one of the first capacitors on at least one of the output lines. It has an inductor inserted between them.

  Here, the inductor may be a line filter that magnetically couples a pair of output lines.

  Further, the DC conversion circuit has a primary side rectifying / smoothing circuit for rectifying and smoothing an AC input, a transformer, a switching element for switching the primary winding of the transformer, and a secondary side rectifying / smoothing circuit for rectifying and smoothing the voltage of the secondary winding of the transformer. And a second capacitor for connecting the low potential side node (N2) of the primary side rectifying / smoothing circuit and the low potential side node (N4) of the secondary side rectifying / smoothing circuit, and the control circuit is low in the primary side rectifying / smoothing circuit. The switching element may be PWM controlled using the potential side node (N2) as a reference potential.

  Furthermore, a series circuit of the inductor and the current detection resistor is inserted between the low potential side node (N4) of the secondary side rectifying and smoothing circuit and one node of the first capacitor, and a detection voltage generated in the current detection resistor. The control circuit may be configured to PWM control the switching element so that becomes equal to the set value.

  Moreover, it is preferable that the capacity of the first capacitor is 100 pF or more and 10,000 pF or less, and the inductance of the inductor is 100 μH or more and 2 mH or less.

  According to a second aspect of the present invention, there is provided the above power supply unit, an LED lamp configured of a metal casing having a ground terminal, and holding the LED element, and a cable connecting the LED element to the DC output portion of the power supply unit. This is an LED lighting device of a separate power supply type.

  A third aspect of the present invention is a power supply integrated LED lighting device including the above-described power supply unit and an LED lamp that holds an LED element connected to a DC output unit of the power supply unit.

  According to the present invention, in a power supply unit for lighting an LED and an LED lighting device using the same, a malfunction due to radiation noise from an LED element, a cable, or the like is solved while solving problems such as common mode noise from an input power supply. It can be effectively prevented.

1 is a circuit diagram of an LED lighting device according to a first embodiment of the present invention. It is a circuit diagram explaining the modification of the 1st Example of this invention. It is a circuit diagram explaining the other modification of the 1st Example of this invention. It is a circuit diagram of the LED lighting apparatus by the 2nd Example of this invention. It is a circuit diagram of the LED lighting apparatus by the 3rd Example of this invention.

Example 1.
FIG. 1 shows a circuit diagram of an LED lighting apparatus according to a first embodiment of the present invention. The LED lighting device includes a power supply unit 1 and an LED lamp 5. The power supply unit 1 includes a metal casing 2 having AC input portions T1 and T2, DC output portions T3 and T4, and a ground terminal E1. The metal casing 2 includes therein a DC conversion circuit 3, a control circuit 4 that controls the DC conversion circuit 3, output lines L 1 and L 2 from the DC conversion circuit 3, and between the output line L 1 and the metal casing 2. A capacitor 19 to be connected and an inductor 20 inserted in the output line L1 are included. It is assumed that the metal casing 2 is grounded from the grounding terminal E1 through the ground wire.

  The DC conversion circuit 3 converts the AC input from the AC input units T1 and T2 to DC. The DC converter circuit 3 includes a rectifier circuit 10 such as a diode bridge that rectifies an AC input from the AC power supply AC, and a smoothing capacitor 11 that smoothes the output of the rectifier circuit 10 (the rectifier circuit 10 and the smoothing capacitor 11 are combined to be primary. Side rectification smoothing circuit). The DC conversion circuit 3 also includes a transformer 12, a switching element 13 for switching the primary winding of the transformer 12, a rectifying element 14 for rectifying and smoothing the voltage of the secondary winding of the transformer 12, and a smoothing capacitor 15 (with the rectifying element 14 and The smoothing capacitor 15 is combined to be referred to as a secondary side rectifying and smoothing circuit). The DC conversion circuit 3 further includes a coupling capacitor 16 for connecting the low potential side node N2 of the primary side rectifying and smoothing circuit and the low potential side node N4 of the secondary side rectifying and smoothing circuit for stable operation.

  The control circuit 4 includes a PWM control circuit 17. The PWM control circuit 17 is supplied with power, for example, from the high potential side node N1 of the primary side rectifying and smoothing circuit via the resistor 18, and the low potential side node N2 is used as a reference potential (ground). Yes. The PWM control circuit 17 includes a driver IC and the like, and performs PWM control of the switching element 13 so that the output current of the DC conversion circuit 3 becomes a predetermined value. Although FIG. 1 shows an open loop control circuit, it may be configured to perform current feedback as shown in FIG.

  In the circuit of FIG. 2, a current detection resistor 21 for detecting LED current is inserted into the output line L2, and a voltage generated in the current detection resistor 21 is input to the PWM control circuit 17 as a detection voltage via the photocoupler 22. . The PWM control circuit 17 includes an error amplification circuit (not shown), and controls the ON width in the switching operation of the switching element 13 so that the detected voltage matches the target value. The target value of the LED current may be obtained by dividing a constant voltage source (not shown) in the control circuit 4 or the PWM control circuit 17 with respect to the reference potential (N2).

  In the circuit of FIG. 1 or FIG. 2, the control circuit 4 may include a protection circuit (not shown). For example, in order to detect an abnormality in the AC power supply AC, a configuration in which a voltage between the node N1 and the node N2 is detected and a detected input voltage is compared with a threshold value by a comparator may be used. In this case, the operation of the PWM control circuit 17 is stopped when the detected input voltage is equal to or higher than the threshold value. In order to detect a failure of the LED element 50, a configuration in which an output voltage between the node N3 and the node N4 is detected and the detected output voltage is compared with a threshold value by a comparator may be used. In this case, the operation of the PWM control circuit 17 when the detected output voltage is equal to or higher than the upper limit value (when the LED element has an open failure) or lower than the lower limit value (when a part of the LED element is short-circuited). Stop or reduce output. In any protection operation, the predetermined range or the upper limit value or the lower limit value may be a value obtained by dividing the constant voltage source in the control circuit 4 or the PWM control circuit 17 with respect to the reference potential (N2).

  1 and 2, output lines L1 and L2 are pattern wirings that connect the output nodes N3 and N4 of the DC conversion circuit 3 and the DC output units T3 and T4, respectively. The capacitor 19 has one node N5 connected to the output line L2 and the other node N6 connected to the metal casing 2. The inductor 20 is inserted between the node N4 and the node N5 on the output line L2.

  The LED lamp 5 includes a metal housing 6 having a ground terminal E <b> 2, and holds the LED element 50 by a dielectric that is schematically shown by a capacitor 51. The DC output units T3 and T4 of the power supply unit 1 and the LED element 50 are connected by cables W1 and W2, respectively. It is assumed that the metal housing 6 is grounded from the ground terminal E2 through a ground wire.

  1 and 2 show a power supply unit type LED lighting device in which the power supply unit 1 and the LED lamp 5 are connected via cables W1 and W2, the power supply unit of the present invention is shown in FIG. As shown in FIG. 5, the present invention can also be applied to a power supply integrated LED lighting device in which the LED element 50 is held in proximity to the DC output portions T3 and T4 of the power supply unit 1. In addition, the housing | casing 7 in the LED lamp 5 of FIG. 3 does not need to be earth | grounded and does not need to be metal.

  By inserting the inductor 20 into the output line L1, radiation noise from the LED element 50 or the cables W1 and W2 is prevented from being drawn into the output line L2 via the metal casing 2 and the capacitor 19. That is, the pulse voltage resulting from the radiation noise that can be drawn by the capacitor 19 is attenuated by the inductor 20, and the propagation to the node N4 side is suppressed. Therefore, by inserting the inductor 20 into the output line L2, the noise pulse voltage enters the control circuit 4 via the node N4, the coupling capacitor 16 and the node N2, or via the parasitic capacitance between the mounting patterns on the substrate. Can be prevented.

  Specifically, if pulse noise enters the drive IC of the PWM control circuit 17 from the node N2, the PWM control becomes unstable and the output current value is not constant at a desired value. Such a state can be prevented. Further, when the control circuit 4 has the above-described protection circuit, a line for inputting a detection value (for example, a detection value for an AC input voltage, a detection value for a DC output voltage, etc.) and a threshold value are input to the comparator. If the line pulse noise is placed between the line and the line, an accurate comparison operation is not performed and an unnecessary protection operation can be induced. However, such a state can be prevented by the above configuration. Thereby, it is possible to prevent malfunction of the control circuit 4 due to the radiation noise from the LED element 50 or the cables W1 and W2 no matter how the LED lamp 5 is arranged with respect to the power supply unit 1.

  As described above, by inserting the inductor 20 into the output line, it is possible to increase the capacity of the capacitor 19 and to obtain an advantageous effect that the degree of design freedom for countermeasures against high frequency noise is increased. Further, by inserting the current feedback detection resistor 21 in series with the inductor 20 as shown in FIG. 2, the effect of attenuating the pulse noise voltage can be further obtained.

  1 and 2, the capacitor 19 is connected to the low-potential side output line L2 and the inductor 20 is inserted. However, since the smoothing capacitor 15 allows high-frequency noise to pass, the high-potential side A capacitor may be connected between the output line L1 and the metal housing 2 and an inductor may be inserted on the output line L1.

Example 2
In the first embodiment, a configuration is shown in which a capacitor is connected to one output line and an inductor is inserted. In this embodiment, a capacitor is connected to both output lines L1 and L2 and an inductor is inserted. An example is shown. This embodiment is based on the recognition that the smoothing capacitor 15 allows high-frequency noise such as common mode noise and radiation noise to pass through without being attenuated.

  FIG. 4 shows a circuit diagram of the LED lighting device according to the present embodiment. The difference from the first embodiment shown in FIG. 1 is that the power supply unit 1 includes a capacitor 23 and an inductor 24. That is, in the capacitor 23, one node N7 is connected to the output line L1 on the high potential side, and the other node N8 is connected to the metal casing 2. The inductor 24 is inserted between the output node N3 and the node N7 on the output line L1.

  According to the present embodiment, by connecting the capacitor 23 between the output line L1 and the metal casing 2, the common mode noise from the AC power supply AC becomes the node N2, the coupling capacitor 16, the node N4, the smoothing capacitor 15, and the node. Propagation to the LED element 50 through N3 and the output line L1 is prevented. In order to obtain the same effect as that of the inductor 20 in the first embodiment, the inductor 24 is inserted on the output line L1. That is, by inserting the inductor 24, the radiation noise from the LED element 50 or the cables W1 and W2 is changed to the metal housing 2, the node N8, the capacitor 23, the node N7, the node N3, the smoothing capacitor 15, the node N4, and the coupling capacitor. 16 and the node N2 or the parasitic capacitance between the mounting patterns on the substrate can be prevented from entering the control circuit 4. Therefore, according to the present embodiment, further enhanced noise countermeasures can be taken.

  In the present embodiment, either one of the capacitors 19 and 23 may be omitted. Also in this embodiment, the current feedback circuit and the protection circuit described in the first embodiment may be used.

Example 3
In the second embodiment, a configuration is shown in which a capacitor is connected to one output line and an inductor is inserted. In this embodiment, a configuration using a line filter that magnetically couples both output lines L1 and L2 is shown. .

  FIG. 5 shows a circuit diagram of the LED lighting device according to this embodiment. The difference from the first embodiment shown in FIG. 1 is that the power supply unit 1 includes a line filter 25 that magnetically couples between the output line L1 and the output line L2. According to the configuration of the present embodiment, in addition to the effects obtained in the first or second embodiment, normal mode noise (line-to-line noise) due to radiation noise or switching noise is generated on the primary side of the DC conversion circuit 3 or the AC power supply AC. The effect which suppresses propagating to is acquired.

  In the present embodiment, a capacitor may be connected between the output line L1 on the high potential side and the metal casing 2 in the same manner as the configuration related to the line L2 on the low potential side. Further, instead of a configuration in which a capacitor is connected only between the low-potential side output line L2 and the metal casing 2, a configuration in which a capacitor is connected only between the high-potential side output line L1 and the metal casing 2 is provided. It is good. Also in this embodiment, the current feedback circuit and the protection circuit described in the first embodiment may be used.

  In each of the above embodiments, increasing the capacitance of the capacitor 19 (23) to about 10,000 pF increases the effect of passing high-frequency noise (for example, common mode noise). The influence of the inductance component to be increased increases, and the effect of passing high-frequency noise is reduced. Therefore, the capacitance of the capacitor 19 (23) is preferably set to 100 pF or more and 10,000 pF or less.

  Under the assumption that the capacitance of the capacitor 19 (23) is not less than 100 pF and not more than 10000 pF, increasing the inductance of the inductor 20 (24, 25) to about 2 mH increases the attenuation effect of high-frequency noise, but exceeds that. If it is increased, the influence of the capacitance between the coil windings becomes larger, and the high frequency noise attenuation effect is reduced. Therefore, the inductance of the inductor 20 is preferably set to 100 μH or more and 2 mH or less.

  According to the structure shown in each said Example, the power supply unit which solves the problem of various high frequency noise, and the LED lighting apparatus using the same can be provided. In particular, the power supply unit and LED lighting device of each embodiment can effectively prevent malfunction due to radiation noise from LED elements, cables, and the like.

Although the said Example and modification show the most suitable example of this invention, this invention can be suitably changed in the range which does not deviate from the meaning.
For example, in each of the above embodiments, the capacitor input type is shown as the primary side rectifying / smoothing circuit of the DC conversion circuit 3, but it may be configured to include a boost converter having a power factor improving function. In each embodiment, the input power source is an AC power source. However, when the input power source is a DC power source, the rectifier circuit and the smoothing capacitor may be omitted.
In each of the above embodiments, a flyback type DC / DC converter is shown as the DC conversion circuit 3. However, other types of switching power supply circuits such as a forward type, a step-up type, a step-down type, and a step-up / down type chopper circuit are used. It may be used. Further, the smoothing capacitor may be reduced in capacity or omitted, and an AC / DC converter may be used for the DC conversion circuit 3.

1. 1. Power supply unit 2. Metal housing DC conversion circuit 4. 4. Control circuit LED lamps6. Metal casing 7. Housing 10. Rectifier circuits 11, 15. Smoothing capacitor 12. Transformer 13. Switching element 14. Rectifying element 16. Coupling capacitor 17. PWM control circuits 19, 23. Capacitors 20, 24. Inductor 21. Detection resistor 25. Line filter 50. LED elements T1, T2. AC input units T3, T4. DC output units E1, E2. Grounding terminals L1, L2,. Output lines W1, W2. Cables N1 to N8. node

Claims (7)

A power supply unit for lighting an LED,
It consists of a metal casing having an AC input unit, a DC output unit to which the LED element is connected, and a grounding terminal,
The metal casing is inside,
A direct current conversion circuit for converting the alternating current input from the alternating current input unit into direct current,
A pair of output lines connecting the output node of the DC converter circuit and the DC output unit;
A control circuit for controlling the DC conversion circuit;
A first capacitor having one node connected to at least one output line of the pair of output lines and the other node connected to the metal casing; and
In order to prevent the radiation noise from entering the control circuit by drawing the radiation noise due to the lighting of the LED to the one output line through the metal casing and the first capacitor, prior Symbol least one of the output on line, the power supply unit with the inserted inductor during the previous SL one node of said output node and said first capacitor of said DC converter circuit.   The power supply unit according to claim 1, wherein the inductor is a line filter that magnetically couples between the pair of output lines. The power supply unit according to claim 1 or 2,
The DC conversion circuit includes a primary side rectifying / smoothing circuit for rectifying and smoothing the AC input, a transformer, a switching element for switching the primary winding of the transformer, and a secondary side rectifying for rectifying and smoothing the voltage of the secondary winding of the transformer. A smoothing circuit, and a second capacitor for connecting the low potential side node (N2) of the primary side rectification smoothing circuit and the low potential side node (N4) of the secondary side rectification smoothing circuit,
A power supply unit configured such that the control circuit performs PWM control of the switching element using a low potential side node (N2) of the primary side rectifying and smoothing circuit as a reference potential.   4. The power supply unit according to claim 3, wherein a series circuit of the inductor and a current detection resistor is provided between a low potential side node (N4) of the secondary side rectifying and smoothing circuit and the one node of the first capacitor. A power supply unit that is inserted and configured to PWM-control the switching element so that a detection voltage generated in the current detection resistor by the control circuit is equal to a set value.   5. The power supply unit according to claim 1, wherein the first capacitor has a capacitance of 100 pF to 10,000 pF, and the inductor has an inductance of 100 μH to 2 mH. The power supply unit according to any one of claims 1 to 5,
A power supply-separated type LED lighting device comprising a metal casing having a grounding terminal, the LED lamp holding the LED element, and a cable connecting the DC element and the DC element of the power supply unit. A power supply integrated LED lighting device comprising: the power supply unit according to any one of claims 1 to 5; and an LED lamp that holds the LED element connected to the DC output unit of the power supply unit.

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