JP2017192223A - Led power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a power of an LED power supply device, and to improve an insulation technology thereof.SOLUTION: Provided is an LED power supply device 10 that comprises: a power supply insulation circuit 16 that supplies a power to an LED element 22 while securing insulation properties between a power supply 12 and the LED element 22; and a control circuit 18. The power supply insulation circuit 16 comprises an input side switch S10 and an output side switch S20. An inductor L1 and a first charging capacitor C1 are provided at a secondary side of the input side switch S10 and at a primary side of the output side switch S20, and a second charging capacitor C2 is provided at a secondary side of the output side switch S20. The control circuit 18 charges the first charging capacitor C1 by turning on the S10 and turning off the S20, and charges the second charging capacitor C2 with a power charged in the inductor L1 and the first charging capacitor C1 by turning off the S10 and turning on the S20. The LED element 22 is lighted by a power charged in the C2.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an LED power supply device, and more particularly, to an increase in power of the LED power supply device and improvement of insulation technology.

  With the recent development of semiconductor technology, switching power supply devices have been used in various fields. In particular, power supply to the LED element, which was difficult to supply power stably until a long time ago, can be realized by using a switching device using recent semiconductor technology. And the replacement from the conventional light source is progressing rapidly by the technical improvement of a switching power supply device, the luminous efficiency improvement of an LED element, etc. By the way, it was originally a disadvantage of LED elements that the light output per unit is small. However, a stable power supply is made using a switching power supply device, and many LED elements are combined in series and parallel. By increasing the light output, the replacement of the conventional HID lamp with an LED lamp has been performed.

  In general, an LED module in which a large number of LED lamps are arranged often has a structure that solves a thermal problem by contacting with a case that also serves as a radiator in order to obtain good heat dissipation. In such a case, the radiator (or case) is often grounded, and some kind of protection function is required when a short circuit or ground fault occurs. Therefore, in recent years, an insulation transformer that operates at a high frequency is used to protect the power supply device, and a flyback type switching power supply device (LED power supply device) that can obtain good DC power with a small number of components is used. This solves such a problem (Patent Document 1). Moreover, in patent document 2, in order to protect a power supply device from the high voltage arc discharge in the conventional power supply device (power supply device which does not utilize a flyback transformer), regardless of the presence or absence of arc discharge, Alternatively, a technique for stopping supply of direct current to the LED module at random is disclosed.

Patent No. 5595255 JP 2014-35943 A

  However, in the flyback-type LED power supply device that lights the LED module using a commercial AC power supply as in Patent Document 1, it is difficult to increase the power due to the production of a transformer. In practice, it is said that a power supply device using a flyback transformer has a limit of about 100 W. The main reasons for this are that the surface area of the transformer itself does not increase in proportion to the increase in size due to the increase in size of the transformer due to the increase in power, and the distance of heat generated inside the transformer increases and heat accumulates. It may be easier.

  Therefore, a conventional power supply device (a power supply device that does not use a flyback transformer) may be used to increase the power consumption of the power supply device. However, as described above, the LED module is grounded to improve heat dissipation. Since the conventional power supply device is not electrically insulated, it cannot be used as it is. And in the power supply circuit of patent document 2, in order to stop supply of direct current to an LED module periodically, it is provided with the switching element which performs a switch function, but it cannot be said that it is an insulation type power supply circuit composition, It is not possible to achieve sufficient circuit protection when the power is increased. Another problem is that the LED power supply is generally grounded, so the electrostatic capacity (ground capacity and stray capacity) between the LED module and the ground becomes very large, and the LED power supply is installed. Later, there is a problem that the noise level becomes larger than the actual specification of the LED power supply device.

  Here, noise in the power supply circuit (power supply device) will be described. In general, noise can be divided into two types according to the conduction method. As shown in FIG. 6, noise generated between signal lines and between power supply lines is generally called normal mode noise. This normal mode noise is characterized in that the direction of the noise current is opposite. As shown in FIG. 7, the noise generated between the signal line or the power supply line and the ground is generally called common mode noise. This common mode noise is characterized in that the direction of the noise current is the same as shown in FIG. In the LED power supply device, since the radiator is grounded, common mode noise as shown in FIG. Specifically, as described above, common mode noise has the same direction of noise current, and can be said to be a high-frequency current due to the influence of stray capacitance or the like. Therefore, the LED power supply device acts as a pseudo antenna as a whole LED power supply device as shown in FIG. 8 due to common mode noise from the outside or common mode noise due to high-speed switching inside the LED power supply device. As a result, reception and transmission of radiation noise are promoted. Here, radiated noise refers to radio noise that is transmitted through space by alternately intertwining the electric and magnetic fields according to Maxwell's electromagnetic equation (vector notation by Hevisite), and noise similar to radio noise caused by other causes. Say. As a general antenna technology, the parallel plate capacitor shown in FIG. 9 is used as a basis, and the capacitor is opened as shown in FIG. 10 and the electric flux current is opened to the space (the two capacitor plates are changed to rods). Is the basic antenna shape (dipole antenna). There is a method in which one of the two rods is replaced with the ground (earth), and the LED power supply with the heat sink grounded receives the radiation noise by the antenna action (FIG. 8). It encourages outgoing calls.

  In other words, there is a possibility that high power can be realized by making the LED power supply device a conventional power supply circuit, but the conventional power supply device cannot realize sufficient insulation from the ground of the radiator. (Originally, flyback LED power supply devices have become mainstream to achieve insulation). And even if sufficient insulation with respect to the grounding of the heatsink for radiating the LED module by some method can be realized, as shown in FIG. Since the entire LED power supply device has an antenna action and radiation noise increases, it is extremely difficult to use the conventional power supply device as it is as the LED power supply device.

  The present invention has been made in view of the above-mentioned problems of the prior art, and its purpose is to realize a large power of a switching power supply device that can be used for lighting an LED module or the like, and to maintain sufficient insulation. In addition, the present invention is to realize a switching power supply device capable of supplying stable power with little radiation noise.

In order to solve the above-described problems, an LED power supply device according to the present invention includes:
A rectifier circuit that adjusts an AC voltage from a commercial power supply, and a power supply that adjusts the voltage rectified by the rectifier circuit to a DC voltage and supplies power to the LED element and ensures insulation between the commercial power supply and the LED element. An LED power supply device comprising: an insulation circuit; and a control circuit for sending an appropriate control signal to the power supply insulation circuit,
The power supply isolation circuit includes an input side switch and an output side switch, and a first input side switch is disposed on the high potential side of the input side switch and a second input side switch is provided on the low potential side. A first output side switch is disposed on the high potential side of the output side switch and a second output side switch is disposed on the low potential side;
Further, the power supply insulation circuit includes a first charge which is a secondary side of the input side switch and an inductor on the primary side of the output side switch, and one is connected to the high potential side and the other is connected to the low potential side. A second charging capacitor having one side connected to the high potential side and the other side connected to the low potential side on the secondary side of the output side switch;
The first input side switch and the second input side switch are simultaneously turned on and off,
The first output side switch and the second output side switch are simultaneously turned on and off,
The control circuit charges the first charging capacitor by turning on the input side switch and turning off the output switch, turns off the input side switch, and turns on the output side switch. The second charging capacitor is charged with electromagnetic energy generated by an inductor and the electric power charged in the first charging capacitor, and the LED element is supplied with electric power charged in the second charging capacitor.

Moreover, the LED power supply device according to the present invention is
The control circuit includes a pause period in which both the input side switch and the output side switch are turned off.

Moreover, the LED power supply device according to the present invention is
The input side switch and the output side switch include semiconductor elements, and diodes are connected in series in the forward direction of the semiconductor elements.

According to the present invention, the power supply insulating circuit includes the input side switch and the output side switch, and when the input side switch is on, the output side switch is turned off and the first charging capacitor is charged to turn off the input side switch and output. By turning on the side switch, the second charging capacitor is charged by the electromagnetic energy of the inductor, the electric charge charged by the first charging capacitor is discharged, and the second charging capacitor is charged at the same time. It is possible to realize an LED power supply device that can realize electric power and maintain sufficient insulation.
Further, by controlling the control circuit to provide a pause period during which the input side switch and the output side switch are simultaneously stopped, power supply to the LED element can be realized while maintaining reliable insulation. Further, by controlling so that the input side switch and the output side switch are not turned on at the same time, it is possible to reduce radiation noise due to the antenna action of the entire power supply device while maintaining more reliable insulation.

1 shows a simplified schematic principle diagram of an LED power supply device according to the present invention. FIG. FIG. 3 shows a second simplified schematic diagram of an LED power supply device according to the present invention. The schematic block diagram of the LED power supply device which concerns on embodiment of this invention is shown. The semiconductor element example utilized for each switch with which the LED power supply device which concerns on embodiment of this invention is provided is shown. The time chart of each switch by the control signal from the control circuit with which the LED power supply device which concerns on embodiment of this invention is provided is shown. A schematic explanatory diagram of general normal mode noise is shown. The schematic explanatory drawing of general common mode noise is shown. The schematic explanatory drawing about the antenna effect | action of the power supply circuit by common mode noise is shown. A schematic diagram of the displacement current when an AC power supply is connected to the parallel plate capacitor is shown. The schematic of the dipole antenna which is the basic form of an antenna is shown.

  Hereinafter, although the LED power supply device of this invention is demonstrated using drawing, it will not be limited to the following examples at all unless it exceeds the meaning of this invention.

  First, a characteristic configuration of the LED power supply device according to the embodiment of the present invention will be described using a simplified principle diagram. FIG. 1 is a simplified schematic principle diagram of an LED power supply device according to an embodiment of the present invention. The LED power supply device 110 shown in the figure is for supplying an appropriate voltage while maintaining insulation between the power source 112 that supplies a DC voltage (and DC current) and the power source 112 side and the load side (LED element 122 side). Power supply insulation circuit 116. The power supply insulating circuit 116 includes an input side switch S10, a free wheel diode D1, a first coil L1, a first charging capacitor C1, an output side switch S20, and a second coil for suppressing the peak value of the current. L2 and a second charging capacitor C2 for supplying stable DC power to the LED element 122.

  What is characteristic about the present invention is that the power supply insulation circuit 116 includes the input side switch S10 and the output side switch S20, and there is no period in which the input side switch S10 and the output side switch S20 are simultaneously turned on. It is controlled so that. The input side switch S10 includes a high input side switch S11 disposed on the high potential side and a low input side switch S12 disposed on the low potential side, and the output side switch S20 is disposed on the high potential side. It is composed of a high output side switch S21 and a low output side switch S22 arranged on the low potential side. Basically, the high input side switch S11 and the low input side switch S12 are simultaneously turned on / off, and the high output side switch S21 and the low output side switch S22 are simultaneously turned on / off.

  When the power source 112 is turned on, the DC voltage reaches the input side switch S10 provided in the power supply insulating circuit 116 from the power source 112. At this time, the input side switch S10 (input side high voltage switch S11, input side low voltage S12) is turned on by a control signal from a control circuit (not shown), and the DC power from the power source 112 is converted to the power source 112. → High input side switch S11 → First coil L1 → First charging capacitor C1 → Low input side switch S12 → Power supply 112 is charged to charge the first charging capacitor C1. At this time, the output side switch S20 (output side high pressure switch S21, output side low pressure switch S22) is turned off by a control signal from the control circuit. Therefore, the power supply 112 on the input side, the second charging capacitor C2 on the output side, and the LED element 122 are insulated. Next, the input side switch S10 (high input side switch S11, low input side S12) is turned off, and the output side switch S20 (high output side switch S21, low output side S22) is turned on. Then, the current as the magnetic field energy stored in the first coil L1 is as follows: first coil L1 → high output side switch S21 → second coil L2 → second charging capacitor C2 → low output side switch S22 → diode D1 → first. The second charging capacitor C2 is charged by flowing through one coil L1. The charge stored in the first charging capacitor C1 is as follows: first charging capacitor C1 → high output side switch S21 → second coil L2 → second charging capacitor C2 → low output side switch S22 → first charging capacitor C1. The second charging capacitor C2 is charged by flowing, and the LED element 122 is turned on by the electric power charged in the second charging capacitor C2. Thus, since the energy from both the first coil L1 and the first charging capacitor C1 is stored in the second charging capacitor C2, the LED power supply device 110 capable of supplying a large amount of DC power can be realized. is there.

  As described above, when the input side switch S10 is on, the output side switch S20 is off. Conversely, when the output side switch S20 is on, the input side switch S10 is off. Since it repeats, the power supply 112 and the LED element 122 are always kept in the insulated state.

FIG. 2 shows a second simplified schematic principle diagram of the LED power supply device according to the embodiment of the present invention.
The LED power supply device 210 in FIG. 2 is different from the LED power supply device 110 in FIG. 1 in that the first coil L1 is arranged on the low potential side instead of the high potential side in FIG. As shown in FIG. 2, even if the first coil L1 is arranged on the low potential side, an LED power source that can supply high-power DC power while maintaining insulation, as in the power supply circuit shown in FIG. A device can be realized. At the timing when the DC voltage reaches the power supply insulation circuit 216 from the power supply 212, the input side switch S10 (high input side switch S11, low input side switch S12) is turned on, and the DC power from the power supply 212 is The first charging capacitor C1 is charged by flowing from 212 → high input side switch S11 → first charging capacitor C1 → first coil L1 → low input side switch S12 → power supply 212. At this time, the output side switch S20 (high output side switch S21, low output side switch S22) is turned off. Then, the input side switch S10 (high input side switch S11, low input side switch S12) is turned off, and the output side switch S20 (high output side switch S21, low output side switch S22) is turned on, whereby the first The current as the magnetic field energy stored in the coil L1 is as follows: first coil L1 → diode D1 → high output side switch S21 → second coil L2 → second charging capacitor C2 → low output side switch S22 → first coil L1. Flows to charge the second charging capacitor C2. The charge stored in the first charging capacitor C1 flows in the order of the first charging capacitor C1, the high output side switch S21, the second coil L2, the second charging capacitor C2, the low output side switch S22, and the first charging capacitor C1. Thus, the second charging capacitor C2 is charged, and the LED element 222 is turned on.

  As described above, the LED power supply device 210 in FIG. 2 is also a high-power DC power while maintaining the insulation between the input-side power supply 212 and the output-side LED element 222 in the same manner as the LED power supply device 110 in FIG. LED power supply device capable of supplying

  Next, the LED power supply device according to the embodiment of the present invention will be described. FIG. 3 shows a schematic diagram of an LED power supply apparatus according to an embodiment of the present invention. Here, the LED power supply device in the present specification is a switching power supply device for performing stable power supply to the LED elements. The LED power supply device 10 shown in the figure includes a power supply 12 for supplying a commercial AC voltage, a rectifying / smoothing circuit 14 for rectifying the AC voltage, and adjusting the power from the rectifying / smoothing circuit 14 to the LED element 22. A power supply insulation circuit 16 for supplying DC power; a control circuit 18 for controlling the power supply insulation circuit 16; and a detection circuit 20 for detecting a current flowing through the LED element 22 and sending it to the control circuit 18 as a detection signal. I have.

First, the rectifying / smoothing circuit 14 will be described.
The rectifying / smoothing circuit 14 includes a filter circuit 24, a diode bridge circuit DB, a smoothing capacitor Ca, a power factor correction circuit 26, and an electrolytic capacitor Cb. When an AC commercial voltage (AC 100 V, AC 200 V, etc.) is applied by the power supply 12, the commercial voltage reaches the diode bridge circuit DB via the filter circuit 24. The diode bridge circuit DB is composed of a diode element or the like, but may be composed of another semiconductor element as long as it can perform the same function. The voltage (also referred to as a pulsating voltage) that has been full-wave rectified by the diode bridge circuit DB is smoothed to a rough DC voltage by the smoothing capacitor Ca. Then, the smoothed voltage reaches the power factor correction circuit 26. The power factor correction circuit 26 generates a boosted voltage by charging the electrolytic capacitor Cb after passing a current through the inductor by turning on and off the switching element. In this way, the voltage that has been boosted and whose power factor has been improved reaches the power supply insulation circuit 16.

  Next, the power supply insulation circuit 16 will be described. The power supply insulation circuit 16 basically operates on the principle described in FIG. 1 (and FIG. 2). The power supply insulation circuit 16 includes an input side switch S10, a freewheeling diode D1, a first coil L1, a first charging capacitor C1, an output side switch S20, and a second coil L2 for suppressing a peak value of current, And a second capacitor C <b> 2 for supplying stable DC power to the LED element 22. The input side switch S10 includes a high input side switch S11 disposed on the high potential side and a low input side switch S12 disposed on the low potential side, and the output side switch S20 is disposed on the high potential side. An output side switch S21 and a low output side switch S22 arranged on the low potential side are provided. The four switches may be any switch as long as high-speed switching can be performed, but is preferably a semiconductor element such as a MOSFET or IGBT (see FIG. 4). For example, as shown in FIG. 4, it is preferable to connect diodes in series in the forward direction in order to prevent additional diodes between MOSFET parasitic diodes and IGBT CEs.

  When the voltage from the rectifying and smoothing circuit 14 reaches the input side switch S10, the control circuit 18 turns on the input side switch S10 (control signal ds1) and turns off the output side switch S20 (control signal ds2). At this time, the power from the rectifying / smoothing circuit 14 flows from the high input side switch S11 → the coil L1 → the first charging capacitor C1 → the low input side switch S12 → the rectifying / smoothing circuit 14 (electrolytic capacitor Cb). Capacitor C1 is charged. At this time, the output side switch S20 (the high output side switch S21 and the low output side switch S22) is turned off by the control signal ds2 from the control circuit 18 as described above. Therefore, the input-side power supply 12 (and the rectifying / smoothing circuit 14) and the output-side LED element 16 (and the second charging capacitor C2) are insulated. Next, the control circuit 18 turns off the input side switch S10 (high input side switch S11 and low input side S12) and turns on the output side switch S20 (high output side switch S21 and low output side S22). Then, the current as the magnetic field energy stored in the first coil L1 is as follows: first coil L1 → high output side switch S21 → second coil L2 → second charging capacitor C2 → low output side switch S22 → diode D1 → first. The second charging capacitor C2 is charged by flowing through one coil L1. The charge stored in the first charging capacitor C1 flows in the order of the first charging capacitor C1, the high output side switch S21, the second coil L2, the second charging capacitor C2, the low output side switch S22, and the first charging capacitor C1. Thus, the second charging capacitor C2 is charged, and the LED element 22 is turned on by the DC power charged in the second charging capacitor C2.

  Here, the control operation of the control circuit 18 will be described. FIG. 5 shows a time chart for on / off of each switch (input-side switch S10 and output-side switch S20) receiving the control signal from the control circuit 18. The control signal ds1 shown in FIG. 3 represents the control signal for the input side switch S10 (S11 and S12), and the control signal ds2 represents the control signal for the output side switch S20 (S21 and S22). At point a in FIG. 5, the input side switch S10 (S11 and S12) is turned on by sending the control signal ds1, and the output side switch S20 (S21 and S22) is turned off by the control signal ds2. That is, in this period (point a), the first charging capacitor C1 is charged. At point b in FIG. 5, the control circuit 18 turns off the input side switch S10 by sending a control signal ds1, and turns on the output side switch S20 by sending a control signal ds2. That is, during this period (point b), the second charging capacitor C2 is charged, and the LED element 22 is turned on by the electric power charged in the second charging capacitor C2. Here, in FIG. 5, a pause period T is provided between points a and b. That is, in the actual control operation of the LED power supply device 10, reliable insulation is realized by providing a pause period T during which both the input side switch S10 and the output side switch S20 (four switches) stop operating. -ing

  Then, the current supplied to the LED element 22 is detected as a feedback control signal by the current detection resistor R1 included in the detection circuit 20, and is sent to the control circuit 18 via the insulation amplifier OP. Based on this feedback control signal, the control circuit 18 calculates a switching operation signal so that the LED element 22 can properly perform the lighting operation. Based on the calculated operation signal (signals ds1 and ds2), the input side switch S10 and The output side switch S20 is repeatedly turned on and off.

As described above, when the input side switch S10 is turned on, the output side switch S20 is turned off, and a pause period T in which both the input side switch S10 and the output side switch S20 are turned off is provided, and the input side switch S10 is turned off and the output side switch is turned off. By repeating the operation of turning on S20, sufficient power supply is achieved while ensuring sufficient insulation of the LED power supply device 10.

About reduction of radiation noise Here, reduction of radiation noise in the LED power supply device 10 of the present invention will be described. As described above, the LED power supply device 10 maintains good heat dissipation by connecting the LED element 22 to a grounded radiator. This grounding of the radiator generates common mode noise. As a result, an antenna action occurs in the entire LED power supply device, and radiation noise is generated (see FIGS. 7 and 8). The common mode noise may be generated by an external noise source, or may be generated by a high-speed switching operation by each switch (input side switch S10 and output side switch S20) in the LED power supply device. . Regardless of the cause, the increase of the stray capacitance or ground capacitance due to the grounding of the radiator causes a loop of high frequency noise current between the LED power supply 10 and the ground, and common mode noise is generated. Possible (see FIG. 7).

  Therefore, in the LED power supply device 10 according to the present invention, the input side switch S10 and the output side switch S20 are turned on and off by the control circuit 18 as shown in the time chart of FIG. 4 in order to ensure insulation of the power supply device. The common mode noise is removed by intermittently connecting the circuit on the side (power supply 12 side) and the output side (LED element 22 side) in terms of high frequency, and as a result, the antenna action is interrupted. That is, the switching operation according to the present invention realizes high power, secures insulation of the LED power supply device, and at the same time reduces radiation noise due to antenna action.

As described above, according to the LED power supply device 10 of the present invention, the input side switch S10 and the output side switch S20 are provided. When the input side switch S10 is on, the output side switch S20 is turned off and the first charging capacitor is charged. By turning on the output-side switch S20 and turning off the input-side switch S10, the second charging capacitor C2 is charged by the electromagnetic energy of the first coil L1, and the charge charged by the first charging capacitor C1 is released simultaneously. By charging the second charging capacitor C2, it is possible to increase the power of the LED power supply device 10 and to realize an LED power supply device that maintains sufficient insulation.
Furthermore, by performing control with a pause period T during which the input side switch S10 (S11 and S12) and the output side switch S20 (S21 and S22) are simultaneously stopped, it is possible to realize power supply while maintaining reliable insulation. . And by performing control not to turn on the input side switch S10 and the output side switch S20 at the same time, it is possible to realize reduction of radiation noise due to the antenna effect of the entire LED power supply device.

10 110 210 LED power supply device 12 112 212 Power supply 14 Rectification smoothing circuit 16 116 216 Power supply insulation circuit 18 Control circuit 20 Current detection circuit 22 122 222 LED element 24 Filter circuit 26 Power factor improvement circuit S10 Input side switch S11 High input side switch S12 Low input side switch S20 Output side switch S21 High output side switch S22 Low output side switch DB Diode bridge circuit D1 Free-wheeling diode L1 First coil L2 Second coil Ca Smoothing capacitor Cb Electrolytic capacitor C1 First charging capacitor C2 Second Charging capacitor R1 Current detection resistor OP Insulation amplifier

Claims (3)

A rectifier circuit that adjusts an AC voltage from a commercial power supply, and a power supply that adjusts the voltage rectified by the rectifier circuit to a DC voltage and supplies power to the LED element and ensures insulation between the commercial power supply and the LED element. An LED power supply device comprising: an insulation circuit; and a control circuit for sending an appropriate control signal to the power supply insulation circuit,
The power supply isolation circuit includes an input side switch and an output side switch, and a first input side switch is disposed on the high potential side of the input side switch and a second input side switch is provided on the low potential side. A first output side switch is disposed on the high potential side of the output side switch and a second output side switch is disposed on the low potential side;
Further, the power supply insulation circuit includes a first charge which is a secondary side of the input side switch and an inductor on the primary side of the output side switch, and one is connected to the high potential side and the other is connected to the low potential side. A second charging capacitor having one side connected to the high potential side and the other side connected to the low potential side on the secondary side of the output side switch;
The first input side switch and the second input side switch are simultaneously turned on and off,
The first output side switch and the second output side switch are simultaneously turned on and off,
The control circuit charges the first charging capacitor by turning on the input side switch and turning off the output switch, turns off the input side switch, and turns on the output side switch. An LED power source characterized in that the second charging capacitor is charged with electromagnetic energy generated by an inductor and electric power charged in the first charging capacitor, and the LED element is supplied with electric power charged in the second charging capacitor. apparatus. The LED power supply device according to claim 1,
The LED power supply device according to claim 1, wherein the control circuit provides a pause period in which both the input side switch and the output side switch are turned off. The LED power supply device according to any one of claims 1 and 2,
The input power switch and the output switch include a semiconductor element, and a diode is connected in series in the forward direction of the semiconductor element.

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