JP2010192406A - Led lighting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light bulb type LED lamp securing heat dissipation efficiency while suppressing generation of noise or complication of control. <P>SOLUTION: A driving circuit 25 varies a rotating direction at the start of an air cooling fan 42 and a rotational velocity of the cooling fan 42 during driving according to prescribed conditions. Heat dissipation efficiency can be secured suppressing the generation of noise or the complication of control unlike conventional control of varying the rotating direction of the air cooling fan 42 during driving thereof. The consumed power can be suppressed since the air cooling fan 42 can be rotated and driven only when needed by varying the rotational velocity of the air cooling fan 42 according to the prescribed conditions. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an LED lighting device provided with an air cooling fan.

  Conventionally, an LED bulb as an LED lighting device of this type used as an alternative to a bulb has a glove attached to a metal base substrate on which a plurality of LEDs, which are light emitting elements, are mounted on one main surface side. A radiator is attached to the back side of the base substrate, a base is attached to cover the metal base substrate and the radiator, and a lighting circuit for lighting the LED is provided between the base and the radiator. The lighting circuit board is accommodated. The heat generated by the LED is dissipated by the heat dissipating body, thereby achieving stable lighting and long life of the LED. In recent years, with the miniaturization of LED bulbs, in order to more efficiently dissipate heat from high-temperature components such as LEDs, a configuration in which an air cooling fan is attached to forcibly dissipate heat is known (for example, see Patent Document 1). .).

  However, if the air cooling fan is rotated only in a certain direction, dust may accumulate at a predetermined position, which may adversely affect the apparatus. For this reason, a configuration is known in which the heat dissipation efficiency is ensured by periodically reversing the rotation direction of the air cooling fan and blowing away dust (see, for example, Patent Documents 2 and 3).

JP 2008-198478 A (Page 5-7, FIG. 3) Japanese Utility Model Publication No. 7-11718 (page 5-7, FIG. 1) Japanese Patent Laid-Open No. 6-4980 (page 3, FIG. 1)

  However, the configuration described in Patent Document 2 described above is merely a configuration in which dust is blown off by the reverse rotation of the air cooling fan, and the heat dissipation efficiency at the time of reverse rotation of the air cooling fan is not taken into consideration. There is a risk that it will not be possible.

  Further, in the configuration described in Patent Document 3 described above, the heat dissipation efficiency can be improved by normal rotation and reverse rotation of the air cooling fan, but noise may be generated by reversing the air cooling fan during driving of the air cooling fan. In addition, there is a risk of complicated control because the air cooling fan is frequently reversed.

  This invention is made | formed in view of such a point, and it aims at providing the LED lighting device which ensured the thermal radiation efficiency, suppressing generation | occurrence | production of noise and complication of control.

  The LED lighting device according to claim 1 includes: an LED; a lighting means for lighting the LED; an air-cooling fan capable of rotating forward and reverse for radiating the LED; and a rotational drive of the air-cooling fan to control rotation of the air-cooling fan. Fan control means for changing at least one of the rotation direction and the rotation speed of the air-cooling fan in accordance with a predetermined condition.

  The lighting means controls the LED current using, for example, a step-down regulator circuit.

  As the air cooling fan, for example, an axial fan that is driven to rotate by a motor or the like is used.

  The change in the rotation speed of the air cooling fan includes the stop of the rotation of the air cooling fan.

  The predetermined condition is, for example, when the temperature of the LED is low, such as when the apparatus is activated, or when the LED is turned on and the temperature is high.

  According to a second aspect of the present invention, there is provided the LED lighting device according to the first aspect, further comprising a temperature sensor that monitors the temperature of the LED, and the fan control means rotates the air cooling fan according to the temperature detected by the temperature sensor. Is something that changes.

  The temperature sensor may directly detect the temperature of the LED, or may indirectly detect the temperature of the LED via the ambient temperature of the LED or the like.

  Changing the rotation speed of the air cooling fan in accordance with the temperature detected by the temperature sensor means increasing or decreasing the rotation speed of the air cooling fan in accordance with the detected temperature of the temperature sensor, for example.

  According to a third aspect of the present invention, in the LED lighting device according to the second aspect, the fan control means switches the presence / absence of rotation of the air cooling fan in accordance with the temperature detected by the temperature sensor.

  Switching the presence or absence of rotation of the air cooling fan according to the temperature detected by the temperature sensor means, for example, stopping the rotation of the air cooling fan when the temperature detected by the temperature sensor is low.

  The LED lighting device according to a fourth aspect is the LED lighting device according to the second or third aspect, wherein the fan control means switches the rotation direction of the air cooling fan when any of the air cooling fans is activated.

  Switching the rotation direction of the air cooling fan at the time of activation of any of the air cooling fans means, for example, reversing the air cooling fan at every activation or once at several activations.

  The LED lighting device according to claim 5 is the LED lighting device according to claim 1, further comprising polarity detection means for detecting the power supply polarity when the power is turned on, and the fan control means has the power supply polarity detected by the polarity detection means. The air cooling fan is activated in the corresponding direction.

  An AC power source is used as the power source.

  The polarity detection means is composed of, for example, a comparator and a latch circuit.

  According to the LED lighting device of the first aspect, the fan control means changes at least one of the rotation direction at the start of the air cooling fan and the rotation speed of the air cooling fan according to a predetermined condition, thereby generating noise and Heat dissipation efficiency can be ensured while suppressing control complexity.

  According to the LED lighting device of claim 2, in addition to the effect of the LED lighting device of claim 1, the fan control means changes the rotational speed of the air cooling fan according to the temperature detected by the temperature sensor, For example, when the ambient temperature is low, the rotation number of the air cooling fan can be suppressed, and power consumption can be suppressed.

  According to the LED lighting device of claim 3, in addition to the effect of the LED lighting device of claim 2, the fan control means switches the presence or absence of rotation of the air cooling fan according to the temperature detected by the temperature sensor, For example, the air cooling fan can be stopped when the temperature is low, such as immediately after startup, and the power consumption can be further suppressed.

  According to the LED lighting device of the fourth aspect, in addition to the effect of the LED lighting device of the second or third aspect, the fan control means reverses the rotation direction of the air cooling fan when any of the air cooling fans is started. Thus, when the air cooling fan is started, the rotation direction of the air cooling fan can be set to the normal rotation direction or the reverse rotation direction, so that accumulation of dust can be prevented while ensuring a heat radiation effect.

  According to the LED lighting device of claim 5, in addition to the effect of the LED lighting device of claim 1, the fan control means activates the air cooling fan in a direction corresponding to the power supply polarity detected by the polarity detection means. Thus, when the air cooling fan is started, the rotation direction of the air cooling fan can be set to the normal rotation direction or the reverse rotation direction with a probability of approximately 1/2, so that dust accumulation can be prevented with a simple configuration while ensuring a heat dissipation effect. .

It is a circuit diagram of the LED lighting device which shows the 1st Embodiment of this invention. It is a longitudinal cross-sectional view of an LED lighting device same as the above. It is an external view of a LED lighting device same as the above. It is a circuit diagram of the LED lighting device which shows the 2nd Embodiment of this invention.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  1 to 3 show a first embodiment. FIG. 1 is a circuit diagram of an LED lighting device, FIG. 2 is a longitudinal sectional view of the LED lighting device, and FIG. 3 is an external view of the LED lighting device.

  2 and 3, reference numeral 11 denotes a light bulb shaped LED lamp which is a light bulb shaped lamp as an LED lighting device. The light bulb shaped LED lamp 11 is a heat radiator in which an LED substrate portion 12 which is a substrate portion is a heat transfer material. An air cooling means 15 is housed in a housing portion 14 attached to one end side of the heat dissipating body 13 and provided on the other end side of the heat dissipating body 13, and the heat dissipating body 13 together with the air cooling means 15 is a hollow, substantially cylindrical main body case. 16, a glove 17 is attached to one end side of the main body case 16 so as to cover the LED board portion 12, and a housing case 19 that houses the lighting circuit board portion 18 is disposed on the other end side of the main body case 16. It is attached and a base 20 is attached to the housing case 19. The bulb-shaped LED lamp 11 has the same total length as a so-called mini-krypton bulb.

  The LED substrate unit 12 includes an LED substrate 23 which is a circular substrate in plan view, and a fan control for driving the LED 24 and the air cooling means 15 which are a plurality of light emitting elements mounted on the one main surface 23a side of the LED substrate 23. And a drive circuit 25 as means.

  The LED substrate 23 is a metal base substrate formed of a metal material such as aluminum having good heat dissipation or an insulating material, for example, and the other main surface 23b is in thermal contact with the radiator 13 .

  The LED 24 includes, for example, a bare chip (not shown) that emits blue light and a resin part (not shown) formed by a silicone resin or the like that covers the bare chip. A phosphor (not shown) that mainly emits yellow light which is a complementary color of blue is mixed, and each LED 24 is configured to obtain white illumination light.

  The drive circuit 25 is a circuit for supplying DC power to the air cooling means 15.

  Further, in the radiator 13, one end portions (upper end portions) of the plurality of radiating fins 31 are connected by a substantially circular connecting portion 32 in a plan view, and the storage portion 14 is partitioned inside the radiating fins 31. . The radiator 13 is formed of, for example, a metal material such as aluminum having a good thermal conductivity, or a resin material.

  The heat radiating fins 31 are formed at positions near the outer periphery of the connecting portion 32, and are formed at substantially equal intervals in the circumferential direction of the heat radiating body 13. Therefore, a ventilation portion 33 that communicates with the storage portion 14 is formed between the radiation fins 31.

  The connecting portion 32 is a board mounting surface 34 having a flat upper surface, and the board mounting surface 34 is in close contact with the other main surface 23b of the LED board 23 and thermally connected thereto. Yes.

  The air cooling means 15 is configured by unitizing a motor 41 and an air cooling fan 42 that is rotationally driven by the motor 41.

  In the motor 41, the rotation direction and the rotation speed are controlled by the electric power supplied from the drive circuit 25. The air cooling fan 42 is connected to the one end 52a side of the rotating shaft 52, and the other end 52b side of the rotating shaft 52 is radiated. The air cooling fan 42 can be rotated forward and backward by being inserted into a substantially cylindrical bearing portion 55 press-fitted into the mounting hole 37 of the body 13 and rotatably supported.

  The air cooling fan 42 is, for example, an axial fan, and has a substantially cylindrical fan central portion 61 connected to the rotating shaft 52 of the motor 41, and a plurality of blade portions 62 projecting radially from the fan central portion 61. And have. A plurality of blade portions 62 are formed in the circumferential direction, and are configured to flow air along the vertical direction, that is, the axial direction of the air cooling fan 42 by rotation. Note that the air cooling fan 42 is configured such that the flow rate thereof does not change, that is, the heat dissipation effect of the LED 24 does not change during both forward rotation and reverse rotation.

  The main body case 16 is formed of a member with good heat dissipation. Furthermore, support portions 71 that support the heat radiating body 13 from the lower side are formed so as to protrude toward the central axis side at substantially central positions at both ends in the axial direction (vertical direction) of the main body case 16. Further, on the outer peripheral surface of the main body case 16, a lower opening 73 serving as a first intake / exhaust port as a plurality of first openings communicating with the ventilation portion 33 is adjacent to the support portion 71 at a position on the one end 16 a side. Thus, openings are formed spaced apart from each other in the circumferential direction. Further, upper openings 74 as second intake / exhaust openings as a plurality of second openings communicating with the ventilation portion 33 are formed on the outer peripheral surface of the other end 16b of the main body case 16 so as to be spaced apart from each other in the circumferential direction. Has been. An attachment recess 75 for attaching the globe 17 is formed on the inner peripheral side of the other end 16b of the main body case 16.

  The lower opening 73 is for taking outside air into the main body case 16 when the air cooling fan 42 of the air cooling means 15 is rotating forward, and exhausting the air inside the ventilation portion 33 when the air cooling fan 42 is rotating reversely. It is formed in a long hole shape along the axial direction of 16 and is spaced apart at substantially equal intervals in the circumferential direction of the main body case 16.

  The upper opening 74 allows the air taken into the main body case 16 from the lower opening 73 during the normal rotation of the air cooling fan 42 of the air cooling means 15 through the storage part 14 and the ventilation part 33 in the radiator 13. This is for exhausting outside and taking in the outside air into the main body case 16 when the air cooling fan 42 is reversed, facing the outer peripheral surface of the radiating fins 31 and at substantially equal intervals in the circumferential direction of the main body case 16. They are spaced apart.

  Further, the globe 17 is formed in a flat spherical shape with light diffusing glass or synthetic resin, and one end 17a is attached to the mounting recess 75 of the main body case 16 and is positioned on one end side of the radiator 13. The main body case 16 is continuous in shape with the other end 16b side.

  In addition, the lighting circuit board unit 18 includes a lighting circuit board 81 that is a flat lighting device body, and a lighting circuit 82 that is formed on the lighting circuit board 81 and serves as lighting means. The lighting circuit 82 is, for example, a circuit that supplies a constant current to the LED 24, and is electrically connected to the LED substrate unit 12 via a wiring (not shown).

  The housing case 19 is formed in a substantially cylindrical shape that is fitted to the one end 16a side of the main body case 16 with an insulating material such as PBT resin, for example, and the radiator case 13, the main body case 16, and the base 20 are Insulates between. The housing case 19 may be filled with a silicone-based resin, which is a filler having heat dissipation and insulation properties, so that the lighting circuit board portion 18 is buried.

  The base 20 is, for example, of the E17 type having a screw thread to be screwed into a lamp socket of a lighting fixture (not shown), and is electrically connected to the lighting circuit board 18 side by wiring (not shown).

  Next, the circuit configuration of the first embodiment will be described.

  As shown in FIG. 1, the light bulb shaped LED lamp 11 is connected to the commercial AC power source e through the capacitor C1 having the function of a noise filter and the input side of a full wave rectifying element REC as a rectifying means. A step-down regulator circuit 91 is connected to the output side of the wave rectifier element REC via a smoothing capacitor C2, and a series circuit of LEDs 24 and an air cooling means 15 (motor 41) are connected to the output side of the step-down regulator circuit 91. The lighting circuit 82 is configured by the full-wave rectifying element REC, the capacitors C1 and C2, the step-down regulator circuit 91, and the like. The driving circuit 25 for driving the air cooling means 15 is connected to a temperature sensor 93 for detecting the temperature of the LED 24 and a current control means 94 for controlling the operation of the step-down regulator circuit 91, respectively.

  In the step-down regulator circuit 91, a series circuit of a diode D, a switching element Q, and a resistor R1 is connected in parallel to the capacitor C2, and an inductor L is connected to the connection point between the anode side of the diode D and the drain terminal of the switching element Q. The primary winding L1 is connected, and a capacitor C3 is connected in parallel with the diode D on the output side of the primary winding L1. Further, the secondary winding L2, which is the auxiliary winding of the inductor L, the gate terminal of the switching element Q, and the connection point between the source terminal of the switching element Q and the resistor R1 are connected to the current control means 94, respectively. .

  For example, the temperature sensor 93 is disposed on the main surface of the LED substrate 23 (FIG. 2) on the back side of the LED 24, or on the same main surface as the LED 24 of the LED substrate 23 (FIG. 2) and in the vicinity of the LED 24. The heat (temperature) associated with is detected indirectly by detecting the ambient temperature of the LED 24 and output to the drive circuit 25.

  The current control means 94 has a configuration capable of so-called PWM (Pulse Width Modulation) control in which the current flowing through the LED 24 is controlled to a desired value by controlling the on-duty (off-duty) of the switching element Q. .

  The air cooling means 15 is powered from the output side of the step-down regulator circuit 91, but is not limited to this configuration.

  Next, the operation of the first embodiment will be described.

  When the bulb-shaped LED lamp 11 is energized with the base 20 attached to a predetermined socket, the lighting circuit 82 of the lighting circuit board unit 18 operates to supply power to the LED board unit 12 side.

  Specifically, the AC power supply from the commercial AC power supply e is full-wave rectified by the full-wave rectifying element REC and smoothed by the capacitor C2. Then, the current control means 94 controls the on-duty of the switching element Q, thereby controlling the LED current to a desired value. The current control means 94 detects the current flowing through the switching element Q via the resistor R1 that is the source resistance of the switching element Q, and determines the turn-off timing of the switching element Q based on the detected current. The turn-on timing is controlled by the voltage of the secondary winding L2 of the inductor L so as to operate in the critical mode.

  As a result, each LED 24 emits light, and the emitted light is diffusely irradiated through the globe 17.

  Further, the heat generated from each LED 24 in the LED board portion 12 is transmitted to the heat radiating body 13 through the board mounting surface 34 and is radiated through the heat radiating fins 31 of the heat radiating body 13.

  At this time, the drive circuit 25 supplies DC power to the motor 41 to rotate the air cooling fan 42 via the motor 41 as necessary. Specifically, the drive circuit 25 controls the rotational speed during the rotational drive of the air cooling fan 42 (motor 41) according to the temperature detected by the temperature sensor 93, for example.

  For example, when the temperature of the LED 24 detected by the temperature sensor 93 is equal to or lower than a predetermined temperature, such as immediately after activation of the bulb-shaped LED lamp 11 (immediately after turning on the power) or when the ambient temperature is low, the air cooling fan 42 is determined not to rotate, the air cooling fan 42 (motor 41) is not rotationally driven (the air cooling fan 42 (motor 41) is stopped), and the temperature of the LED 24 detected by the temperature sensor 93 is preset. When the temperature is higher than the set predetermined temperature, it is determined that the air cooling fan 42 needs to be rotated, and the air cooling fan 42 (motor 41) is rotated.

  Further, the drive circuit 25 rotates the air cooling fan 42 (motor 41) and then turns the air cooling fan 42 (motor 41) on, for example, when the power is turned off or when the temperature detected by the temperature sensor 93 becomes low. When the air-cooling fan 42 (motor 41) is rotationally driven again once it has been stopped, it is rotated in the direction opposite to the previous rotational direction.

  As a result, during the forward rotation of the air cooling fan 42, the external air is sucked into the main body case 16 from the lower opening 73 into the main body case 16 due to the negative pressure accompanying the forward rotation, and the sucked outside air is After passing through the air cooling fan 42 in the axial direction and sprayed on the back surface of the connecting portion 32 of the heat radiator 13, it flows in the radial direction through the ventilation portion 33 and passes from the upper opening 74 to the outside of the main body case 16. Then, the air is exhausted from below to above (see the solid line in FIG. 2). Further, when the air cooling fan 42 is reversed, outside air is sucked into the main body case 16 from the upper opening 74 into the main body case 16 due to the negative pressure caused by the reverse rotation, and the sucked outside air is sucked into the ventilation portion. After flowing in the radial direction through the air cooling fan 33, the air passes through the air cooling fan 42 in the axial direction and is blown to each part in the ventilation portion 33, so that dust accumulated during the normal rotation of the air cooling fan 42 is blown off, and the lower opening The air is discharged from 73 toward the outside of the main body case 16 from above to below (see the imaginary line in FIG. 2).

  Then, the heat generated from the LED 24 is forcibly cooled via the radiator 13 by forced air blowing by the air cooling means 15.

  As described above, in the first embodiment, the drive circuit 25 changes the rotation direction when the air cooling fan 42 is activated and the rotation speed of the air cooling fan 42 according to predetermined conditions.

  For this reason, for example, compared to conventional control that changes the rotation direction during driving of the air cooling fan 42, it is possible to ensure heat dissipation efficiency while suppressing noise generation and control complexity, and according to predetermined conditions. By changing the rotational speed of the air cooling fan 42, the air cooling fan 42 can be rotationally driven only when necessary, so that power consumption can be suppressed.

  Specifically, the drive circuit 25 switches the presence / absence of rotation of the air cooling fan 42 according to the temperature detected by the temperature sensor 93 to stop the air cooling fan 42 when the temperature is still low, for example, immediately after startup. And power consumption can be further suppressed.

  The drive circuit 25 reverses the rotation direction of the air cooling fan 42 each time the air cooling fan 42 is started, so that the rotation direction of the air cooling fan 42 is set to the normal rotation direction every time the air cooling fan 42 is started. Therefore, it is possible to prevent the accumulation of dust that occurs when the air-cooling fan 42 continues to rotate only in a certain direction while ensuring a heat dissipation effect. That is, the air cooling fan 42 can sufficiently secure the flow rate of the cooling air regardless of whether the air cooling fan 42 is rotated in the normal direction or the reverse direction, so that not only the dust can be blown away but also the heat dissipation effect can be ensured.

  In the first embodiment, the control for reversing the rotation direction of the air cooling fan 42 at the start-up is not performed every time the air-cooling fan 42 is started. It is good also as a structure performed at the time of starting.

  Further, the drive circuit 25 may be configured to change the rotation speed of the air cooling fan 42 in accordance with the temperature detected by the temperature sensor 93. Specifically, for example, the lower the temperature detected by the temperature sensor 93, the lower the rotational speed of the air cooling fan 42 (motor 41), and the temperature detected by the temperature sensor 93 is equal to or lower than a preset predetermined temperature. Alternatively, the air cooling fan 42 may be stopped. In this case, for example, when the ambient temperature is low, the rotational speed of the air cooling fan 42 can be suppressed, and power consumption can be suppressed.

  Next, FIG. 4 shows a second embodiment, and FIG. 4 is a circuit diagram of the LED lighting device. In addition, about the structure and effect | action similar to the said 1st Embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  In the second embodiment, the drive circuit 25 is connected to the polarity detection means 96 in the first embodiment.

  The polarity detection means 96 detects the power supply polarity when the power is turned on via resistors R2 and R3 connected to the output side of the full-wave rectifying element REC. Although not shown, the polarity detection means 96 is composed of a comparator, a latch circuit, and the like, and is configured to instruct the drive circuit 25 in the direction of rotation using an H / L signal.

  Further, the drive circuit 25 is configured to switch the rotation direction of the air cooling fan 42 (motor 41) in accordance with the H / L signal from the polarity detection means 96. For example, when the H level signal is output from the polarity detection means 96, the air cooling fan 42 (motor 41) is rotated forward, and when the L level signal is output from the polarity detection means 96, the air cooling fan 42 ( The motor 41) is controlled to reverse.

  When the power is turned on, the power polarity immediately after the power is turned on is determined by the polarity detecting means 96, and either the H level signal or the L level signal is output to the drive circuit 25 according to the power polarity. As a result, the drive circuit 25 rotates the air-cooling fan 42 (motor 41) forward or backward.

  The lighting circuit 82 controls the lighting of the LED 24 as in the first embodiment.

  As a result, the air-cooling fan 42 is normally or reversely rotated with a probability of 1/2 at the start-up without requiring a reversing means for reversing the rotation direction of the air-cooling fan 42 while the air-cooling fan 42 is driven. Therefore, it is possible to prevent the accumulation of dust that occurs when the air-cooling fan 42 is continuously rotated only in a certain direction while ensuring the heat dissipation effect.

  In addition, if the air cooling fan 42 is frequently reversed during driving, not only complicated control is required, but also the rotation direction of the air cooling fan 42 may change during driving, which may cause noise. Thus, since the rotation direction of the air-cooling fan 42 is reversed only at the time of start-up, complicated control is not required, and noise caused by a change in the rotation direction can be prevented.

  In each of the above embodiments, the lighting means for lighting the LED 24 is not limited to the lighting circuit 82 using the step-down regulator circuit 91.

  Further, the LED lighting device is not limited to a light bulb type.

11 Light bulb shaped LED lamp as LED lighting device
24 LED
25 Drive circuit as fan control means
42 Air cooling fan
82 Lighting circuit as lighting means
93 Temperature sensor
96 Polarity detection means

Claims (5)

With LED;
Lighting means for lighting the LED;
A forward and reverse air cooling fan for heat dissipation of the LED;
Fan control means for controlling rotation driving of the air cooling fan and changing at least one of a rotation direction at the time of starting the air cooling fan and a rotation speed of the air cooling fan according to a predetermined condition;
The LED lighting device characterized by comprising. A temperature sensor for monitoring the temperature of the LED;
The LED lighting device according to claim 1, wherein the fan control means changes the rotational speed of the air cooling fan in accordance with the temperature detected by the temperature sensor. The LED lighting device according to claim 2, wherein the fan control means switches presence / absence of rotation of the air cooling fan according to a temperature detected by the temperature sensor. 4. The LED lighting device according to claim 2, wherein the fan control means switches a rotation direction of the air cooling fan when any one of the air cooling fans is started. 5. Provided with polarity detection means for detecting the power supply polarity at power-on,
The LED lighting device according to claim 1, wherein the fan control means activates the air cooling fan in a direction corresponding to the power supply polarity detected by the polarity detection means.

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