KR20140088440A - LED dimming converter - Google Patents

Abstract

The present invention relates to an LED converter for supplying rated power for lightening a light emitting diode (LED), and more particularly, to a high efficiency LED dimming converter capable of stably adjusting illumination (brightness) of the LED, which includes a power factor improving unit, a PWM unit and a dimming control unit. The power factor improving unit improves the power factor of a commercial power source which serves as an input power source. The PWM unit allows constant power to be supplied to the LED. In this case, the power factor improving unit and the PWM unit are not driven independently from each other, but the power factor improvement and the constant power supply are simultaneously performed by a power factor improving PWM unit. The dimming control units compares the voltage and current output to the LED with a dimming instruction signal to generate a dimming control signal, and transmits the dimming control signal to the power factor improving PWM unit. A high efficiency LED dimming converter according to the present invention includes a rectifying unit for rectifying an input power; a transformer for voltage-converting ripple power output from the rectifying unit; a direct current unit for converting output power of the transformer into DC power and supplying the DC power to the LED; a power factor improving PWM unit for controlling switching of the transformer in a PWM scheme in order to allow the constant current to be supplied to the LED and for improving a power factor; and a dimming control unit for transmitting a dimming control signal for adjusting illumination of the LED to the power factor improving PWM unit.

Description

High efficiency LED dimming converter {LED dimming converter}

[0001] The present invention relates to a light emitting diode, that is, an LED converter for supplying a rated power for lighting an LED, and more particularly, to an LED converter for improving the power factor of a commercial power source, The power factor improving unit and the PWM unit are not separately driven but the power factor improvement and the supply of the constant power source are performed simultaneously in the power factor improving PWM unit and the dimming control unit compares the voltage and current output from the LED with the dimming command signal To a high efficiency LED dimming converter capable of stably controlling the illuminance (brightness) of an LED by generating a dimming control signal and transmitting the generated dimming control signal to a power factor improving PWM unit.

The light source of the lighting apparatus is an incandescent lamp and a fluorescent lamp. Recently, an LED is used.

LED has a variety of advantages such as high illuminance, low power consumption, semi-permanent life span, environment-friendly and emotional lighting, and has recently become a popular light source for lighting fixtures.

The converter is a power supply that converts the commercial power to the rated power required for lighting by turning on the LED.

In general, a converter for LED has a transformer for converting a commercial power source into a rated power source, and a PWM unit for switching a transformer in a PWM manner, and a converter having a power factor improving unit for improving the power factor of a commercial power source while emphasizing energy efficiency .

1 is a circuit diagram of a conventional constant current type power supply device for a high-brightness LED lighting device, which is a converter (i.e., a power supply device) according to the prior art of FIG. 1, However,

A power factor improving unit (PFC) 30 for improving the power factor of the input power source so that the voltage and the current are in phase with each other, a smoothing unit 30 for smoothing the power factor- And the PWM units 40 and 60 convert the transformer T2 into a rated power by switching the transformers T2 and C3 in the PWM manner.

The power factor improving unit 30 (PFC) and the PWM units 40 and 60 are independently driven to have unique IC chips U1 and U2 to improve the power factor and make the rated power.

That is, in the prior art, the power factor improving unit 30 (PFC) and the PWM units 40 and 60 are separately provided, and the smoother DC power is supplied to the transformer T2 at the output side of the power factor improving unit 30 Smoothing portions C3, C7, R1, R4, R5, and R12 are provided.

In the current trend of reducing energy consumption, that is, reducing unnecessary power loss and increasing efficiency, while the energy resources are gradually getting depleted, the converter according to the related art has a power factor improving unit 30 (PFC) and a PWM unit 40 60 and the smoothing units C3, C7, R1, R4, R5, and R12 on the output side of the power factor improving unit, the sum of the power consumed by each of them is not negligible.

The converter has a feedback unit for sensing the voltage supplied to the LED and / or the voltage to continuously supply the rated power to the LED, that is, the constant voltage and / or the constant current, and transmitting the PWM to the PWM unit for controlling the switching of the transformer. It is necessary to have its own driving power to compare the voltage or / and voltage to the reference voltage and / or current and to transmit the comparison result to the PWM section,

In the prior art, the driving power of the feedback unit is converted into a direct current power of the transformer and an output power of the direct current unit which supplies the output power of the transformer to the LED is converted into a driving power of a constant voltage by the regulator.

The power loss is unexpectedly large when the output power of the direct current part is converted and used as the driving power of the feedback part as in the prior art and the driving power of the feedback part is difficult to be maintained when a short circuit occurs in the LED load. There is a danger that the feedback can not be made, and the converter is damaged due to failure to feed the overcurrent due to the short circuit.

Another way to save energy is to introduce a converter with dimming capability that can control the brightness of the LED light by adjusting the ambient illumination or the user's choice, ie, adjusting the power consumption of the LED.

LED converters having a dimming function have been disclosed variously as disclosed in Korean Patent Laid-Open No. 10-2012-0114421 entitled " Dimming Adjusting LED Lighting Device and Method ", Registered Patent No. 1130334 entitled "LED Street Lamp Variable in Brightness According to Ambient Illumination ".

A converter according to the related art having a dimming function is a system in which a PWM unit for controlling the switching of a transformer receives and processes an external dimming command signal. In other words, the PWM unit not only controls the switching of the transformer, but also performs various functions such as feedback of the voltage and current supplied to the LED for controlling the switching, receiving the dimming command signal, and the like. Thus, the PWM part that performs many functions is so heavy that it exceeds the processing limit, and there is a great risk that operation errors will occur or be damaged.

Therefore, it is necessary to provide a dimming function to the converter to save energy, but it is necessary to prevent the malfunction or damage by preventing the load of the PWM part from being increased for dimming control.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the problems of the conventional LED converters,

It improves the power factor and at the same time introduces the power factor improvement PWM unit which converts to the rated power and does not need the smoothing part for the switching method of the transformer of the transformer to maximize the energy efficiency by minimizing the power consumed by the converter, Efficiency LED dimming converter having a dimming function so as to adjust the brightness of the LED,

The dimming control signal for adjusting the brightness of the LED is not input to the PWM section separately from the voltage and current feedback signals supplied to the LED but is also applied to the dimming command signal which is inputted from the outside and the feedback signal of voltage and current, The dimming control signal for controlling the brightness of the control signal, that is, the brightness of the LED, is transmitted to the PWM unit by a dimming control signal in which the voltage and current feedback signals supplied to the LED are combined into one unit, thereby reducing the load on the PWM unit, Another object of the present invention is to provide an LED dimming converter,

In addition, when the driving power for driving the dimming control section, the dimming interface section, and the feedback section is dimmed to a brightness of 5% or less using the voltage induced in the auxiliary winding separately connected to the secondary side of the transformer, By stabilizing the supply of power, it is possible to prevent the LED light from flickering due to unstable feedback operation and to keep the driving power for a short time even when the LED load is short, The present invention also provides a high efficiency LED dimming converter that can protect the LEDs.

To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein,

A rectifying section for rectifying input power;

A transformer for transforming the pulsating current power outputted from the rectifying section;

A direct current (DC) unit for directing the output power of the transformer to the LEDs;

A power factor improving PWM unit for controlling the switching of the transformer by a PWM method so as to supply a constant current to the LED and improving a power factor;

And a dimming control unit for transmitting a dimming control signal for adjusting the illuminance of the LED to the power factor improving PWM unit.

And a dimming interface unit for buffering a dimming command signal input from the outside and delivering the dimming command signal to the dimming control unit.

The dimming interface unit

A buffer for buffering an externally input dimming command signal and delivering the dimming command signal to the dimming control unit,

And a comparator for transmitting an off signal to the dimming control unit when the buffered dimming command signal is lower than a minimum value,

A voltage sensing unit for sensing a voltage and a current respectively output from the direct current unit, and a current sensing unit,

The dimming control unit

And compares the voltage and the current sensed by the voltage sensing unit and the current sensing unit with a dimming command signal to generate a dimming control signal.

The high efficiency LED dimming converter according to the present invention having such a configuration is provided with a power factor improving unit for increasing energy efficiency and a PWM unit for controlling the switching of the transformer for the rated power source, The power factor is improved and the rated power is generated. Further, since the smoothing part for PWM switching is not separately provided, the power consumption consumed in the entire converter is minimized and the energy efficiency is maximized. In addition, The dimming control signal for adjusting the brightness of the LED, that is, the dimming control signal for dimming control, is synthesized with the feedback signal of the voltage and current for the rated power and transmitted together with the feedback signal of the rated power, It is possible to prevent malfunctions and damages, and it is possible to provide a dimming control unit, a dimming interface And the feedback power of the feedback section is supplied from the auxiliary winding wound separately on the secondary side of the transformer to reduce the power loss and to stabilize the power supply even when dimming is performed at low illumination level to prevent the light from being shaken. Efficiency LED dimming converter that can protect the converter by detecting the overcurrent due to the short-circuit by keeping the driving power for a short period of time.

1 is a circuit diagram of a conventional LED converter;
2 is a schematic configuration diagram of a high efficiency LED dimming converter according to the present invention.
3 is a specific circuit diagram of a high efficiency LED dimming converter according to the present invention.

Hereinafter, a high efficiency LED dimming converter according to the present invention will be described in more detail with reference to the drawings.

Before describing the converter according to the present invention in more detail,

While the present invention has been described in connection with certain embodiments, it is obvious that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention. It is to be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but on the contrary, is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

In the drawings, the same reference numerals are used for the same reference numerals, and in particular, the numerals of the tens and the digits of the digits, the digits of the tens, the digits of the digits and the alphabets are the same, Members referred to by reference numerals can be identified as members corresponding to these standards.

In the drawings, the components are expressed by exaggeratingly larger (or thicker) or smaller (or thinner) in size or thickness in consideration of the convenience of understanding, etc. However, It should not be.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the term " comprising " or " consisting of ", or the like, refers to the presence of a feature, a number, a step, an operation, an element, a component, But do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

In the following description of the present invention, it is to be noted that the reference numerals added to the respective components are not related to the reference numerals used in the prior art shown in FIG.

2 and 3, the present invention includes an EMI filter 10, a rectifying unit 20, a power factor improving PWM unit 30, a transformer T1, a DC unit 40, a feedback unit 50, A supply unit 60, a dimming control unit 70, a dimming interface unit 80, and the like.

3A, the input side to which the commercial power is input includes a fuse F1 for blocking the overcurrent when the overcurrent is inputted to the commercial power supply to protect the converter, and a fuse F1 for clamping the instantaneous overvoltage when the surge voltage is input, And a varistor (MOV1) for protecting the converter is connected.

The EMI filter 10 is connected to the output side of the fuse F1 and the varistor MOV1 to remove a conductive noise included in a commercial power source.

The EMI filter 10 includes two line filters LF1 and LF2 on both sides and capacitors C3 and C10 provided on output sides of the two line filters LF1 and LF2 and two line filters LF1 and LF2, And the intermediate point between the two capacitors C1 and C2 connected in series is grounded to flow the conductive noise included in the commercial power supply to the ground.

The rectifier 20 performs full-wave rectification of the commercial power output from the EMI filter 10 and converts it into a pulsed power supply.

The rectifying unit 20 includes bridge diodes D1 to D4.

The transformer (T1) transforms the pulsating current output from the rectifying unit (20) and outputs a rated power having improved power factor.

The power factor improving PWM unit 30 improves the power factor and controls the switching of the transformer T1 so as to output the rated power.

The power factor improving section PWM section 30

A switching device (Q1) for turning on and off the transformer (T1)

A control unit U1 for controlling the switching of the switching device Q1,

Start resistors R2 and R24 and a capacitor C9 for providing a start voltage for initial operation of the control unit U1,

R2, R3, and C6 that sense the voltage waveform of the output pulsating current of the rectifying unit 20 and provide the detected voltage waveform to the control unit U1,

An auxiliary coil t1 wound on the primary side of the transformer T1 and magnetically coupled thereto,

R28, Q3, C14, C12, R21, ZD1, and Q3 that convert the voltage induced in the auxiliary coil t1 into a voltage and supply the voltage to the control unit U1,

 A current sensing unit R13 for sensing a current induced by the switching of the transformer T1 from the auxiliary coil t1 and sensing a zero point where the current intensity is zero and providing the zero point to the control unit U1;

Snares (D9, R12, C11) for limiting and protecting the intensity of counter electromotive force induced on the primary side of the transformer (T1)

(R5, 7, 8, 9, 10, 11, 14, C8, etc.) connected to drive the control unit (U1).

The driving power source units D12, R28, Q3, C14, C12, R21, ZD1, and Q3 maintain a stable driving voltage even at dimming of 5% or less so that the power factor improving PWM unit 30 can operate stably even at low illuminance.

The control unit U1 controls the switching of the switching device Q1 so that the waveform of the current induced in the transformer T1 matches the waveform of the voltage output from the rectifier 20, And the current is in phase to improve the power factor.

More specifically, the control unit U1 controls the voltage of the output pulsating current source of the rectifier unit 20 sensed by the voltage sensing units R1, R23, R3, and C6, The switching element Q1 is switched on and off at a low frequency and the switching element Q1 is switched on and off at a relatively high frequency at the point of time when the voltage is weak, The voltage waveform and the period are the same and the shapes are matched to improve the power factor.

Referring again to FIG. 4,

When the waveform of the one period voltage PV output from the rectifying unit 20 and detected by the voltage sensing units R1, R23, R3, and C6 is the same as shown in the drawing,

At the time when the voltage waveform PV starts, the control unit U1 shortly turns off the switching element Q1 after turning on the switching element Q1,

When the control unit U1 is turned on at a time point at which the intensity of the current induced by the transformer T1 is lowered as the current sensed by the current sensing unit R13 decreases and becomes zero as the switching element Q1 is turned off, Turns on the switching element Q1 and then turns off. At this time, since the voltage intensity of the voltage waveform is increased earlier than that before, the turn-off period is slightly longer, that is, Lt; / RTI >

Thus, the turn-on / turn-off period (i.e., the period) is turned on at each time point when the zero point is sensed by the current sensing unit R13 and is proportional to the voltage intensity at that time, When the turn-off period is long (i.e., switched to low frequency) and the turn-off period is gradually shortened (i.e., switched to high frequency) while going to both sides, the current Pi ), The waveform of the triangular waveform is the same as that of the triangular waveform, and the total current (PI) waveform of the average value connecting the current Pi waveforms has the same period and the same waveform as the voltage PV waveform, And the current (PI) are in phase and the power factor is improved.

The power factor of the pulsating power source improved by the present invention reaches 95%, and the power factor can be improved close to perfection.

The direct current unit 40 directs the output power induced on the secondary side of the transformer T1 to direct current and supplies the direct current to the load LED (L).

The direct current unit 40 includes a diode D7 for rectifying the output power of the transformer T1, a capacitor C5 for smoothing and direct current, and a capacitor C5 for generating an overvoltage on the secondary side of the transformer T1 at the time of turn- And a resistor R20 and a capacitor C18 as a snubber that protects and protects the capacitor C18.

And a line filter (LF3) for removing noise from a rated power supplied as an LED load is provided on the output side of the direct current part (40).

A regulator (not shown) for supplying power to a receiving module (for example, RS485, DALI, Zigbee, PIR sensor, RF / IR interface or the like) for receiving a dimming command signal from the outside by wire or wireless is provided on the output side of the DC unit 40 And a zener diode ZD3 for protecting the regulator U2 from an overvoltage and a connector CN4 for connecting the receiving module to the regulator U2 are connected.

A resistor R18 as a voltage sensing unit for sensing a voltage supplied to the LED as a load, resistors R30 and R31 as a current sensing unit for sensing a current supplied to the LED, And a dimming power supply unit 90 for providing a reference voltage for dimming is connected.

The resistor R18 as the voltage sensing unit provides the voltage sensed through the first terminal to the dimming control unit 70. The resistor R31 as the current sensing unit supplies the sensed current to the dimming And supplies the reference voltage for dimming to the dimming control unit 70 and the dimming interface unit 80 through the fifth terminal and the fifth terminal, respectively.

The dimming power supply unit 90 provides a reference voltage for dimming, that is, a maximum voltage in a range of the dimming command signal that changes the illuminance of the LED. For example, when the dimming command signal has a range of 0 to 10 volts, the maximum voltage of 10 volts becomes a reference voltage for dimming and is provided to the dimming control unit 70 and the dimming interface unit 80. This reference voltage ensures that the dimming command signal received and received by the dimming interface unit 80 and the dimming control unit 70 does not exceed 10 volts even if the dimming command signal is input with a magnitude larger than the reference voltage.

The dimming power supply unit 90 includes resistors R41, R42 and R26, a capacitor C26 and a variable regulator U3. The output voltage of the direct current unit 40 is connected to the resistors R41 and R42 To generate a reference voltage of 10 volts.

The dimming interface unit 80 provides the dimming command signal to the dimming control unit 70 while preventing the externally inputted dimming command signal from affecting the dimming control unit 70. When the input dimming command signal is below the minimum reference value And supplies the light-off signal to the dimming control unit 70 so as to be turned off.

Referring to FIG. 3B, the dimming interface 80 receives a dimming command signal through terminals 8 and 2 ', receives a reference voltage for dimming through terminal 5', receives a reference voltage for terminal 6 ' The driving power is inputted through the power supply.

The dimming command signal inputted through the terminals 8 and 2 'is input to the non-inverting terminal of the buffer U201-A through the resistor R207, the capacitor C201 and the diode D202,

The dimming command signal buffered in the buffer U201-A is output through the 4 'terminal, and the output dimming command signal is transmitted to the dimming controller 70 through the terminal No. 4,

In addition, the dimming command signal buffered in the buffer U201-A is input to the non-inverting terminal of the comparator U201-B via the resistor R202,

The comparator U201-B receives the reference voltage input through the resistor R204 and the resistor R205 via the resistor R204 and receives the voltage from the inverting terminal, Compares the input buffered dimming command signal and outputs an unlit signal via the terminal 7 'when the dimming command signal is smaller than the voltage-divided reference voltage, and delivers the unlit signal to the dimming controller 70. For example, when the reference voltage input through terminal 5 'is 10V and the voltage divided reference voltage to the comparator is 1V, when the buffered dimming command signal is above 1V, the comparator outputs high (15V) The control unit 70 controls the voltage supplied to the LED, which is a load of the direct current unit 40, to be higher, thereby lighting the LED. The comparator outputs a low voltage (0 V) to control the voltage supplied from the dimming control unit 70 to the LED, which is the load of the direct current unit 40, to be lowered to turn off the LED.

The dimming control unit 70 outputs a voltage sensed by the voltage sensing unit R18 and a current sensed by the current sensing unit R31 to a dimming control unit 80 including a dimming command signal The dimming control signal is generated so that the dimming of the LED is controlled to be turned on at a constant illuminance and is transmitted to the power factor improving PWM unit 30 through the feedback unit 50 (P1).

Referring to FIG. 3C, the dimming control unit 70 receives the output voltage of the direct current unit 40, which is sensed by the resistor R18 of the voltage sensing unit through the first terminal, through the resistors R104 and R105, A dimming command signal outputted from the terminal 7 'of the dimming interface unit 80 via the terminal # 4, a current sensed by the resistor R31 of the current sensing unit through the terminal # 4, Receives the dimming command signal outputted from the terminal 4 'of the unit 80, receives the reference voltage for dimming through the terminal 5, receives the driving power required for driving through the terminal 6, To the photocoupler (P1) of the feedback unit (50).

The output voltage of the direct current unit 40 input to the first terminal is input to the IC U101 through the resistor R104. At this time, the low signal (0V; , The transistor Q101 maintains the turn-off state so that the output voltage of the direct current unit 40 is directly input to the IC U101 through the resistor R104 (12V) (when a dimming command signal of 1V or more is inputted in the dimming command signal having a range of 0 to 10V) is inputted to the terminal No. 7, the transistor Q101 is turned on and the output voltage of the direct current section 40 Is inputted to the IC U101 through the combined resistance of the two resistors R104 and R105 so that the output voltage of the dc portion 40 of the IC U101 becomes high The voltage supplied to the LED, which is the load of the DC unit 40, is controlled to be higher, .

The output current of the DC unit 40 sensed by the resistor R31 of the current sensing unit and the output current of the dimming interface unit 0 of the dimming interface unit 0 are input to the fourth terminal of the IC U101, The output current of the direct current unit 40 is greatly attenuated through the resistor R31 of the current sensing unit and the current corresponding to the dimming command signal is supplied to the resistor R201 ) Through the relatively less attenuated. For example, if the output current of the dc portion 40 attenuated to a large extent through the resistor R31 of the current sensing portion has a magnitude of 1, then the resistor R201 connected to the terminal 4 ' The current due to the dimming command signal becomes a magnitude of 10 and the IC U101 has a relatively small influence on the output current of the dc portion 40 so that the current due to the relatively large dimming command signal Thereby generating a dimming control signal. Therefore, the dimming control signal generated by the IC (U101) may be slightly unstable at the initial stage of the input of the dimming command signal, but is stabilized immediately so that a stable constant current is supplied to the LED. When the dimming command signal is inputted in the range of 0 to 10 V but the dimming command signal is changed in units of 1 V when the brightness of the LED is adjusted step by step, The output current of the direct current section 40 is reduced to be equal to or less than 1 V (the current can be converted into the voltage through the resistor), the output current of the direct current section 40 So that it is possible to eliminate instability at the initial stage of the input of the dimming command.

When the signal input through the voltage sensing unit and the current sensing unit is a short signal, the dimming control unit 70 transmits a dimming control signal to stop the operation of the power factor improving PWM unit 30 to protect the converter.

The feedback unit 50 includes a dimming control unit 70 that is generated by comparing a voltage and current supplied from the DC unit 40, that is, a LED load, and a dimming command signal input through the dimming interface unit, To the control unit U1 of the power factor improving PWM unit 30 so that the control unit U1 can supply a stable and stable rated power (constant voltage or / and constant current) to the LED load, Thereby controlling the switching of the transistor Q1.

It may be preferable that the feedback unit 50 uses a photocoupler P1 in which the input and output (that is, the input side light emitting element and the output side light receiving element) are electrically insulated and the transmission of the signal is stable.

The photocoupler P1 of the feedback unit is supplied with driving power from the driving power supply unit 60 and the driving of the photocoupler P1 is controlled by the dimming control signal of the dimming control unit 70.

The driving power supply unit 60 includes a photocoupler P1 of the feedback unit 50, an IC U101 of the dimming control unit 70, a buffer U201-A of the dimming interface unit 80, U201-B).

The driving power supply unit 60 includes an auxiliary winding t2 magnetically coupled to a secondary side of the transformer T2, a diode D11 rectifying a voltage induced in the auxiliary winding t2, R4, R15, capacitors C13, C16, a transistor Q2, and a zener diode ZD2.

The driving power supplied to the driving power supply unit 60 is supplied to the photocoupler P1 via the resistor R32 and is supplied to the ICs of the dimming control unit 70 through the terminals 6 and 6 ' U101 of the dimming interface unit 80 and the buffer U201-A of the dimming interface unit 80 and the comparator U201-B.

The driving power supply unit 60 maintains a stable driving voltage even at dimming of 5% or less, so that light is not shaken even at low illumination.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, The present invention is not limited thereto.

10: EMI filter 20: rectification part
30: Power factor improving PWM unit 40: DC part
50: feedback section 60: driving power supply section
70: dimming control unit 80: dimming interface unit
T1: Trance

Claims (4)

A rectifying section for rectifying input power;
A transformer for transforming the pulsating current power outputted from the rectifying section;
A direct current (DC) unit for directing the output power of the transformer to the LEDs;
A power factor improving PWM unit for controlling the switching of the transformer by a PWM method so as to supply a constant current to the LED and improving a power factor;
And a dimming control unit for transmitting a dimming control signal for adjusting the illuminance of the LED to the power factor improving PWM unit. The method according to claim 1,
And a dimming interface unit for buffering an externally input dimming command signal and transmitting the buffered dimming command signal to the dimming control unit. 3. The method of claim 2,
The dimming interface unit
A buffer for buffering an externally input dimming command signal and delivering the dimming command signal to the dimming control unit,
And a comparator for transmitting an off signal to the dimming control unit when the buffered dimming command signal is less than a minimum value. 4. The method according to any one of claims 1 to 3,
A voltage sensing unit for sensing a voltage and a current respectively output from the direct current unit, and a current sensing unit,

The dimming control unit
And a dimming control signal is generated by comparing a voltage and a current sensed by the voltage sensing unit and the current sensing unit with a dimming command signal.

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