KR101306522B1 - Led current driving circuit - Google Patents

Abstract

The present invention provides a first transistor for controlling a current flowing through the LED assembly, a second transistor connected between the LED assembly and the first transistor, and an amount of current flowing to the LED assembly by applying a predetermined voltage to the first transistor. The feedback unit includes a feedback unit, one end of which is connected to the first transistor and the other end of which is connected to ground, an amplifier receiving a reference voltage through a positive terminal, and an output terminal and a first transistor of the amplifier. And a second switching element connected between a negative terminal of the amplifier and one end of the resistor. According to the present invention, it is possible to provide an LED current driving circuit capable of shortening the turn-on time by preventing the turn-on time from being delayed due to switching noise.

Description

LED Current Driving Circuit {LED CURRENT DRIVING CIRCUIT}

The present invention relates to an LED current driving circuit, and more particularly, to a LED current driving circuit that can implement a short turn-on time by preventing the turn-on time is delayed by switching noise or the like.

Cold Cathode Fluorescent Lamp (CCFL) was used as a light emitting device. However, in the case of CCFL, the response speed is about 15ms and color reproducibility is low. In addition, the use of mercury can lead to environmental hazards. Therefore, in recent years, light emitting diodes (LEDs) have attracted attention as environmentally friendly materials.

In addition, the light emitting diodes are environmentally friendly due to less mercury use and power consumption compared to CCFLs, fast response speed, and excellent color reproducibility. In addition, since the brightness and color temperature of the backlight may be arbitrarily adjusted by adjusting the amount of light of the light emitting diodes emitting red, green, and blue colors, the amount of light of the backlight may be adjusted according to an image displayed on the display device.

The driving device for lighting the light emitting diode includes an LED assembly formed by connecting a plurality of diodes. Since the optical characteristics of the light emitting diode are determined by the current flowing through the light emitting diode, it is preferable to adjust the voltages of both ends of the light emitting diode.

1 is a view showing a current driving circuit borrowed in a conventional LED driving circuit for controlling the current flowing in the LED assembly.

Referring to FIG. 1, a conventional LED current driving circuit includes a first transistor P1 for controlling a current I flowing in an LED assembly (not shown), and a second transistor connected between the LED assembly and the first transistor P2. The PWM control unit 550 controls the feedback unit 520 to control the amount of current flowing to the LED assembly by applying a predetermined voltage to the transistor P2, the first transistor P1, and the second transistor P2 and the switch P3. ).

The feedback unit 520 includes an amplifier 530, a switch P3, and a resistor R. The amplifier 530 receives a reference voltage V through a positive terminal and a resistor R through a negative terminal. The voltage formed by) is fed back through the switch P3.

However, when the switch P3 existing between the amplifier 530 and the resistor R is turned off, the amount of charge at the negative terminal of the amplifier 530 is changed by the switching noise and the charge injection effect. The output of the 530 also changes accordingly, and there is a concern that the turn-on time of the first transistor P1 may be delayed.

That is, it takes a predetermined time for the output voltage of the amplifier 530 affected by the turn-off of the switch P3 to stabilize to the desired driving voltage of the first transistor P1.

An object of the present invention devised to solve the above-described problem is to prevent the turn-on time delayed by switching noise, etc. to realize a short turn-on time, according to the LED current driving circuit capable of fast PWM drive frequency and fine dimming control To provide the furnace.

According to a feature of the present invention for achieving the above object, the LED current drive circuit of the present invention, the first transistor for controlling the current flowing to the LED assembly, and is connected between the LED assembly and the first transistor. A second transistor and a feedback unit configured to apply a predetermined voltage to the first transistor to adjust an amount of current flowing to the LED assembly, wherein the feedback unit is connected to one end of the first transistor and the other end of which is connected to ground; An amplifier receiving a reference voltage through a positive terminal, a first switching element connected between an output terminal of the amplifier and a gate electrode of the first transistor, and a negative terminal of the amplifier and one end of the resistor; And a second switching element.

The feedback unit may further include a feedback capacitor connected between the output terminal of the amplifier and the negative terminal.

The first switching device may be turned on and off simultaneously with the second switching device.

The second transistor may be turned on before the first switching element and the second switching element, and turned off after the first switching element and the second switching element.

The first transistor may include a first electrode connected to the second electrode of the second transistor, a second electrode connected to the resistor, and the second transistor may include a first electrode connected to the LED assembly. The second electrode is connected to the first electrode of the first transistor, and the gate electrode is connected to the PWM controller.

In addition, the first switching element and the second switching element is set as a transistor, the first switching element, the first electrode is connected to the output terminal of the amplifier, the second electrode is connected to the gate electrode of the first transistor A gate electrode connected to the PWM control unit, the second switching device, a first electrode connected to a negative terminal of the amplifier, a second electrode connected to a second electrode of the first transistor, The gate electrode is connected to the PWM control unit.

In addition, the first switching device is characterized in that the gate electrode is connected to the gate electrode of the second switching device.

LED current driving circuit of the present invention, the current control unit for controlling the current of the LED assembly in response to the first control signal and the feedback signal, a resistor, the feedback between the voltage between the current control unit and the resistor in response to the second control signal And a first switching element configured to provide the feedback signal to the current control unit in response to the second control signal.

The first switching element may provide the feedback signal to the current control unit when the voltage between the current control unit and the resistor is fed back, and the feedback unit controls switching noise of the feedback signal using a feedback capacitor. It is characterized by removing.

The feedback unit may receive a reference voltage and a voltage between the current control unit and the resistor to generate the feedback signal, and convert the voltage between the current control unit and the resistor into the amplifier in response to the second control signal. And a feedback capacitor connected between an input terminal of the amplifier receiving the voltage between the current control unit and the resistor and an output terminal of the amplifier outputting the feedback signal.

According to the present invention as described above, the turn-on time is shortened by preventing the turn-on time from being delayed by switching noise, etc., thereby providing an LED current driving circuit capable of fast PWM driving frequency and fine dimming control. have.

1 is a view showing a current driving circuit borrowed in a conventional LED driving circuit to control the current flowing in the LED assembly.
2 is a view showing an LED driving circuit according to a preferred embodiment of the present invention.
3 is a view showing an LED current driving circuit according to a preferred embodiment of the present invention.
4 is a timing diagram illustrating an operation of the LED current driving circuit shown in FIG. 3.
5 is a view showing an LED current driving circuit according to another embodiment of the present invention.

The details of other embodiments are included in the detailed description and drawings.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments described below, but may be embodied in various forms. In the following description, it is assumed that a part is connected to another part, But also includes a case in which other elements are electrically connected to each other in the middle thereof. In the drawings, parts not relating to the present invention are omitted for clarity of description, and like parts are denoted by the same reference numerals throughout the specification.

Hereinafter, the LED current driving circuit of the present invention will be described with reference to embodiments of the present invention and drawings for describing the same.

2 is a view showing an LED driving circuit according to a preferred embodiment of the present invention.

Referring to FIG. 2, the LED driving circuit 100 according to the preferred embodiment of the present invention includes an LED assembly 140, a high voltage generation unit 110, a PWM control unit 120, and a current driving circuit unit 130.

In the LED assembly 140, a plurality of light emitting diode strings (LED strings) including a plurality of light emitting diodes (LEDs) 142 connected in series are arranged in parallel.

In addition, the LED assembly 140 emits light in response to the current flowing in each LED row. The light emitting diodes emit red, green, and blue light, and can adjust luminance of red, green, and blue, respectively.

The high voltage generator 110 receives the input voltage Vin and boosts the voltage to the LED assembly 140. The coil L, the diode D, the transistor M3, the gate driver 110a, and the booster controller 110b and the capacitor C. FIG.

The high voltage generation unit 110 causes a change in the current flowing through the coil L by the turn-on / turn-off operation of the transistor M3 to generate a high voltage by the electromotive force generated in the coil L.

Then, the current is output in one direction by the diode D. The current output through the diode D is applied to the LED assembly 140 at a high voltage through the capacitor C.

The current output through the diode D is fed back by the first resistor r1 and the second resistor r2 to control the booster controller 110b.

The booster controller 110b receives the pulse width modulated signal by the PWM controller 120 to drive the gate driver 110a to adjust the turn-on / turn-off time of the transistor M3, thereby controlling the electromotive force generated in the coil L. You can adjust the size.

The configuration is only one embodiment of the high voltage generation unit 110, but is not necessarily limited to the configuration.

The PWM controller 120 controls the high voltage generator 110 and the current driver circuit 130 by generating a pulse width modulated signal and transferring the pulse width modulated signal to the high voltage generator 110 and the current driver circuit 130.

The high voltage generation unit 110 receiving the predetermined pulse width modulated signal boosts the input voltage Vin to the LED assembly 140, and the current driving circuit unit 130 receiving the predetermined pulse width modulated signal is the LED. A predetermined constant current flows in the assembly 140. In this case, the PWM controller 120 may operate in response to a predetermined control signal EN supplied to the outside.

The current driving circuit unit 130 includes a plurality of LED current driving circuits 130a ... 130j, and light emitting diode rows in the LED assembly 140 are respectively connected to the respective LED current driving circuits 130a ... 130j. do.

Therefore, the amount of current flowing through the LED assembly 140 is determined by the respective LED current driving circuits 130a... 130j to adjust the brightness of light emitted from the LED assembly 140.

3 is a view showing an LED current driving circuit according to a preferred embodiment of the present invention. In particular, one LED current driving circuit 130a of the plurality of LED current driving circuits 130a ... 130j employed in the LED driving circuit 100 of the present invention will be described.

Referring to FIG. 3, the LED current driving circuit 130a includes a current controller 210 and a feedback unit 200.

The current controller 210 controls the current flowing in the LED assembly 140 in response to a predetermined voltage signal applied from the feedback unit 200.

The current control unit 210 may include at least one transistor, and preferably, may include a first transistor M1 and a second transistor M2.

The first transistor M1 controls the current Iled flowing in the LED assembly 140 in response to a predetermined voltage supplied from the feedback unit 200.

To this end, the first transistor M1 may have a first electrode connected to the second transistor M2, a second electrode connected to the first node N1, and a gate electrode connected to the second node N2. have.

The first node N1 may be defined as a contact point where the second electrode of the first transistor M1, one end of the resistor Rset included in the feedback unit 200, and the second switching device S2 meet each other. .

In addition, the second node N2 may be defined as a contact point where the gate electrode of the first transistor M1 and the first switching device S1 included in the feedback unit 200 meet each other.

The second transistor M2 is connected between the LED assembly 140 and the first transistor M1, and electrically connects or cuts off the LED assembly 140 and the first transistor M1 through a turn-on / turn-off operation. Let's do it.

To this end, the second transistor M2 has a first electrode connected to a light emitting diode row included in the LED assembly 140, a second electrode connected to a first electrode of the first transistor M1, and a gate electrode PWM. It may be connected to the control unit 120.

Accordingly, the turn-on / turn-off of the second transistor M2 may be controlled by the pulse width modulation signal supplied from the PWM controller 120.

In this case, the first electrode and the second electrode of each of the transistors M1 and M2 may be set to different electrodes. For example, when the first electrode is a drain electrode, the second electrode is set as a source electrode.

The feedback unit 200 controls the first transistor M1 by applying a predetermined voltage to the first transistor M1, thereby adjusting the amount of current flowing to the LED assembly 140.

To this end, the feedback unit 200 includes a resistor Rset, a first switching device S1, a second switching device S2, and an amplifier 220.

The resistor Rset is connected between the first transistor M1 and ground, one end of which is connected to the second electrode (first node N1) of the first transistor M1, and the other end of which is connected to the ground voltage. It is preferable.

The amplifier 220 receives a reference voltage Vref at a positive terminal, receives a voltage formed by a resistor Rset at a negative terminal, and outputs a predetermined voltage to a gate electrode of the first transistor M1 at an output terminal. Voltage can be applied.

The first switching device S1 is connected between the output terminal of the amplifier 220 and the gate electrode of the first transistor M1, and the second switching device S2 is connected to the negative terminal of the amplifier 220 and the resistor Rset. Is connected between one end (first node N1).

The voltage of the negative terminal of the amplifier 220 is changed according to the switching noise and the charge injection effect generated when the second switching element S2 is turned off, and this change depends on the gain of the amplifier 220. In order to prevent the amplified output from being applied to the first transistor M1, the first switching device S1 is installed, and the first switching device S1 and the second switching device S2 are simultaneously turned on and off. desirable.

In particular, in the preferred embodiment of the present invention, the feedback capacitor 200 further includes a feedback capacitor Cfb.

The feedback capacitor Cfb is connected between the output terminal of the amplifier 220 and the negative terminal of the amplifier 220, so that the voltage of the negative terminal of the amplifier 220 is changed by switching noise of the second switching element S2. Even if the voltage is changed, the voltage at the output terminal of the amplifier 220 can be stably fixed through negative feedback. Accordingly, the voltage required for turning on the first transistor M1 can be secured more quickly, resulting in faster turn-on. You will have time.

The first switching element S1 and the second switching element S2 may be implemented as transistors including a first electrode, a second electrode, and a gate electrode.

In this case, in the first switching device S1, a first electrode is connected to an output terminal of the amplifier 220, a second electrode is connected to a gate electrode of the first transistor M1, and the gate electrode is the PWM controller 120. Can be connected to.

In addition, in the second switching device S2, the first electrode is connected to the negative terminal of the amplifier 220, the second electrode is connected to the first node N1, and the gate electrode is connected to the PWM controller 120. Can be.

The gate electrode of the first switching element S1 and the gate electrode of the second switching element S2 are electrically connected to each other so as to be simultaneously controlled as one signal without receiving a separate signal from the PWM controller 120. It is desirable to be connected.

The PWM controller 120 may control turn-on / turn-off operations of the second transistor M2, the first switching device S1, and the second switching device S2.

In particular, it is preferable to control the first switching element S1 and the second switching element S2 to be turned on at the same time and to be turned off at the same time, and the second transistor M2 is the first switching element S1 and the second switching element. It is preferable to control to turn on before the element S2 and to turn off later than the first switching element S1 and the second switching element S2.

The reason for this is that, when the first and second switching elements S1 and S2 are turned on when the second transistor M2 is turned off, no current flows to the resistor Rset, so the ground voltage is applied to the first node N1. When the ground voltage is transmitted to the first node N1, the ground voltage is transmitted to the negative terminal of the amplifier 220, so that the voltage at the output terminal of the amplifier 220 is lowered, and eventually, the second transistor M2 is again. This is because when it is turned on, it takes a long time for the gate electrode voltage of the first transistor M1 to rise, so that the switching time is not increased.

4 is a timing diagram illustrating an operation of the LED current driving circuit shown in FIG. 3. Referring to FIG. 4, the LED current driving circuit 130a is formed by the first control signal VM2, the second control signal VS1, and the third control signal VS2, which are pulse width modulation signals supplied from the PWM controller 120. ) Is operated.

At this time, the first control signal VM2 is a signal supplied for the control of the first transistor M1, the second control signal VS1 is a signal supplied for the control of the first switching element S1, The third control signal VS2 is defined as a signal supplied for controlling the second switching element S2.

At this time, the second control signal VS1 and the third control signal VS2 are preferably set to the same signal.

When the first control signal VM2 becomes high in the first section T1, the second transistor M2 is turned on. Thereafter, as the second control signal VS1 and the third control signal VS2 become high at the same time, the first switching device S1 and the second switching device S2 are turned on at the same time.

By turning on the second transistor M2, the current Iled may flow from the LED assembly 140 in the ground direction. At this time, the voltage of the first node N1 formed by the resistor Rset is input to the negative terminal of the amplifier 220 through the turned-on second switching element S2.

In the second section T2, as the second control signal VS1 and the third control signal VS2 transition to a low state, the first switching device S1 and the second switching device S2 are first turned off. Thereafter, as the first control signal VM2 transitions to the low state, the second transistor M2 is turned off.

As the second transistor M2 is turned off, the current Iled no longer flows to the LED assembly 140.

In addition, as the first switching device S1 is turned off, the output terminal of the amplifier 220 and the gate electrode of the first transistor M1 are electrically cut off, and as the second switching device S2 is turned off, the amplifier The negative terminal of 220 and the first node N1 are electrically blocked.

At this time, the feedback capacitor Cfb forms a negative feedback path from the output terminal of the amplifier 220 to the negative terminal, so that the voltage of the output terminal of the amplifier 220 is applied to the switching noise of the second switching element S2. It remains stable regardless.

In the third section T3, the operation in the first section T1 is repeated. At this time, the voltage charged in the feedback capacitor Cfb is applied to the gate electrode of the first transistor M1, so that the first transistor ( M1) can be turned on quickly regardless of switching noise of the second switching element S2.

In addition, the output terminal voltage of the amplifier 220 and the gate electrode voltage of the first transistor M1 immediately before the first switching element S1 is turned off are maintained by the feedback capacitor Cfb and the parasitic capacitor, respectively. As a result, a current-overshoot phenomenon of the first transistor M1 generated when the first switching device S1 is turned on can be prevented.

5 is a view showing an LED current driving circuit according to another embodiment of the present invention. Here, the differences from the embodiment described with reference to FIG. 3 will be mainly described, and the same description will be omitted.

Referring to FIG. 5, the LED current driving circuit 130a includes a current control unit 210, a resistor Rset, a feedback unit 200, and a first switching device S1.

The current controller 210 controls the current flowing in the LED assembly 140 in response to the first control signal and the feedback signal output from the feedback unit 200.

The current control unit 210 may include at least one transistor, and preferably, may include a first transistor M1 and a second transistor M2.

The first transistor M1 controls the current Iled flowing in the LED assembly 140 in response to a predetermined voltage supplied from the feedback unit 200.

To this end, the first transistor M1 may have a first electrode connected to the second transistor M2, a second electrode connected to the first node N1, and a gate electrode connected to the second node N2. have.

The first node N1 may be defined as a contact point where the second electrode of the first transistor M1, one end of the resistor Rset, and the second switching device S2 meet each other.

In addition, the second node N2 may be defined as a contact point where the gate electrode of the first transistor M1 and the first switching element S1 meet.

The second transistor M2 is connected between the LED assembly 140 and the first transistor M1, and electrically connects or cuts off the LED assembly 140 and the first transistor M1 through a turn-on / turn-off operation. Let's do it.

To this end, the second transistor M2 has a first electrode connected to a light emitting diode row included in the LED assembly 140, a second electrode connected to a first electrode of the first transistor M1, and a gate electrode PWM. It may be connected to the control unit 120.

Accordingly, the turn-on / turn-off of the second transistor M2 may be controlled by the first control signal VM2, which is a pulse width modulation signal supplied from the PWM controller 120.

In this case, the first electrode and the second electrode of each of the transistors M1 and M2 may be set to different electrodes. For example, when the first electrode is a drain electrode, the second electrode is set as a source electrode.

The resistor Rset is connected between the current control unit 210 and the ground. More specifically, the resistor Rset may be connected between the first transistor M1 in the current control unit 210 and the ground. That is, one end of the resistor Rset is connected to the second electrode (first node N1) of the first transistor M1, and the other end is connected to the ground voltage.

The feedback unit 200 receives the voltage between the current control unit 210 and the resistor Rset in response to the second control signal VS1 to generate the feedback signal.

In addition, the feedback unit 200 controls the current controller 210 by supplying a feedback signal to the current controller 210 through the first switching device S1 to control the amount of current flowing to the LED assembly 140.

In this case, when the voltage between the current controller 210 and the resistor Rset is fed back, the first switching device S1 serves to supply the feedback signal to the current controller 210.

In addition, the feedback unit 200 may remove switching noise of the feedback signal output through the feedback capacitor Cfb.

The first switching device S1 transfers the feedback signal output from the feedback unit 200 to the current control unit 210 in response to the second control signal VS1. In detail, the feedback signal output from the amplifier 220 in the feedback unit 200 may be transmitted to the first transistor M1 in the current control unit 210.

For this purpose, the first switching element S1 is preferably connected between the output terminal of the amplifier 220 and the gate electrode of the first transistor M1.

The feedback unit 200 includes an amplifier 220, a second switching device S2, and a feedback capacitor Cfb.

The amplifier 220 receives a reference voltage Vref through a positive terminal and receives a voltage formed between the current control unit 210 and a resistor Rset through a negative terminal, and at the output terminal of the first transistor M1. The feedback signal may be supplied to the gate electrode.

The second switching device S2 transfers a voltage between the current control unit 210 and the resistor Rset (the voltage of the first node N1) to the amplifier 220 in the feedback unit 200. For this purpose, the second switching element S2 is preferably connected between the negative terminal of the amplifier 220 and one end of the resistor Rset (first node N1).

The voltage of the negative terminal of the amplifier 220 is changed according to the switching noise and the charge injection effect generated when the second switching element S2 is turned off, and this change depends on the gain of the amplifier 220. In order to prevent the amplified output from being applied to the first transistor M1, the first switching device S1 is installed, and the first switching device S1 and the second switching device S2 are simultaneously turned on and off. desirable.

In particular, in the preferred embodiment of the present invention, the feedback unit 200 may stabilize the voltage of the feedback signal by using the feedback capacitor Cfb.

The feedback capacitor Cfb is connected between the output terminal of the amplifier 220 and the negative terminal of the amplifier 220, so that the voltage of the negative terminal of the amplifier 220 is changed by switching noise of the second switching element S2. Even if the voltage is changed, the voltage at the output terminal of the amplifier 220 can be stably fixed through negative feedback. Accordingly, the voltage required for turning on the first transistor M1 can be secured more quickly, resulting in faster turn-on. You will have time.

The first switching element S1 and the second switching element S2 may be implemented as transistors including a first electrode, a second electrode, and a gate electrode.

In this case, in the first switching device S1, a first electrode is connected to an output terminal of the amplifier 220, a second electrode is connected to a gate electrode of the first transistor M1, and the gate electrode is the PWM controller 120. Can be connected to.

In addition, in the second switching device S2, the first electrode is connected to the negative terminal of the amplifier 220, the second electrode is connected to the first node N1, and the gate electrode is connected to the PWM controller 120. Can be.

The gate electrode of the first switching element S1 and the gate electrode of the second switching element S2 are electrically connected to each other so as to be simultaneously controlled as one signal without receiving a separate signal from the PWM controller 120. It is desirable to be connected.

The PWM controller 120 may control turn-on / turn-off operations of the second transistor M2, the first switching device S1, and the second switching device S2.

In particular, it is preferable to control the first switching element S1 and the second switching element S2 to be turned on at the same time and to be turned off at the same time, and the second transistor M2 is the first switching element S1 and the second switching element. It is preferable to control to turn on before the element S2 and to turn off later than the first switching element S1 and the second switching element S2.

The reason for this is that, when the first and second switching elements S1 and S2 are turned on when the second transistor M2 is turned off, no current flows to the resistor Rset, so the ground voltage is applied to the first node N1. When the ground voltage is transmitted to the first node N1, the ground voltage is transmitted to the negative terminal of the amplifier 220, so that the voltage at the output terminal of the amplifier 220 is lowered. This is because when it is turned on, it takes a long time for the gate electrode voltage of the first transistor M1 to rise, so that the switching time is not increased.

It will be understood by those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims rather than the foregoing detailed description, and all changes or modifications derived from the meaning and scope of the claims and the equivalents thereof are included in the scope of the present invention Should be interpreted.

100: LED driving circuit 110: high voltage generation unit
120: PWM control unit 130: current driving circuit unit
130a ... 130j: LED current drive circuit 140: LED assembly
200: feedback unit 210: current control unit
220: Amplifier

Claims (10)

A first transistor for controlling the amount of current flowing through the LED assembly, a second transistor connected between the LED assembly and the first transistor, and applying a predetermined voltage to the first transistor to adjust the amount of current flowing to the LED assembly Including feedback
The feedback unit,
An amplifier connected at one end to the first transistor and connected at the other end to ground, an amplifier receiving a reference voltage through a positive terminal, a first switching device connected between the output terminal of the amplifier and the gate electrode of the first transistor; And a second switching device connected between the negative terminal of the amplifier and one end of the resistor. The method of claim 1, wherein the feedback unit,
LED current driving circuit further comprises a feedback capacitor connected between the output terminal and the negative terminal of the amplifier. The method of claim 1 or 2, wherein the first switching device,
LED current driving circuit is turned on and off at the same time with the second switching element. The method of claim 3, wherein the second transistor,
LED is turned on earlier than said first switching element and said second switching element, and turned off later than said first switching element and said second switching element. The method of claim 1,
The first transistor has a first electrode connected to the second electrode of the second transistor, the second electrode is connected to the resistor,
Wherein the second transistor has a first electrode connected to the LED assembly, a second electrode connected to a first electrode of the first transistor, and a gate electrode connected to a PWM controller. 6. The method of claim 5,
The first switching element and the second switching element are set as transistors,
The first switching device, the first electrode is connected to the output terminal of the amplifier, the second electrode is connected to the gate electrode of the first transistor, the gate electrode is connected to the PWM controller,
The second switching device, the first electrode is connected to the negative terminal of the amplifier, the second electrode is connected to the second electrode of the first transistor, the gate electrode is connected to the PWM control unit LED current drive circuit. The method of claim 6, wherein the first switching device,
And a gate electrode is connected to the gate electrode of the second switching element. A current control unit controlling an amount of current flowing in the LED assembly in response to the first control signal and the feedback signal;
resistance;
A feedback unit receiving the voltage between the current control unit and the resistor in response to a second control signal to generate the feedback signal; And
A first switching device configured to provide the feedback signal to the current control unit in response to the second control signal; Lt; / RTI >
The first switching device, when the voltage between the current control unit and the resistor is fed back, provides the feedback signal to the current control unit,
The feedback unit, the LED current driving circuit, characterized in that for removing the switching noise of the feedback signal by using a feedback capacitor. delete The method of claim 8, wherein the feedback unit,
An amplifier receiving the reference voltage and the voltage between the current controller and the resistor to generate the feedback signal;
A second switching element providing a voltage between the current control unit and the resistor to the amplifier in response to the second control signal; And
A feedback capacitor connected between an input terminal of the amplifier receiving the voltage between the current control unit and the resistor and an output terminal of the amplifier outputting the feedback signal; LED current driving circuit comprising a.

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