LED control device and lighting device including the same

Abstract

One embodiment of the present invention provides an LED control device comprising: a light source module including a first LED string that outputs light of a first color temperature and a second LED string that outputs light of a second color temperature, a power supply unit connected to a first driving node and a second driving node that receive driving power from an LED driver; a square wave generator that operates by a first internal power supply voltage output by the power supply unit and generates a square wave; a duty ratio controller that integrates the square wave generated by the square wave generator and outputs it as a control signal, and outputs a change in the slope of the control signal in response to a change in a time constant; and a switch unit that operates by a second internal power supply voltage output by the power supply unit and controls the current ratio of the current applied to the first LED string and the current applied to the second LED string according to the change in the slope of the control signal.

Description

Technology Field

[0001] The present invention relates to an LED control device and a lighting device including the same. Background Technology

[0003] Light-emitting diodes (LEDs) possess advantages such as low power consumption and a long lifespan, and are rapidly replacing conventional fluorescent and incandescent lights. Recently, various types of lighting devices employing LEDs as light sources have been developed and sold, and there is a growing trend of active research into lighting devices equipped with diverse functions beyond simple illumination. For example, a feature capable of controlling the color temperature of light can be incorporated into lighting devices. The problem to be solved

[0005] One of the objectives of the technical concept of the present invention is to provide an LED control device capable of implementing a color temperature control function at a low cost and a lighting device including the same. means of solving the problem

[0007] One embodiment of the present invention provides an LED control device comprising: a light source module including a first LED string that outputs light of a first color temperature and a second LED string that outputs light of a second color temperature, a power supply unit connected to a first driving node and a second driving node that receive driving power from an LED driver; a square wave generator that operates by a first internal power supply voltage output by the power supply unit and generates a square wave; a duty ratio controller that integrates the square wave generated by the square wave generator and outputs it as a control signal, and outputs a change in the slope of the control signal in response to a change in a time constant; and a switch unit that operates by a second internal power supply voltage output by the power supply unit and controls the current ratio of the current applied to the first LED string and the current applied to the second LED string according to the change in the slope of the control signal.

[0008] One embodiment of the present invention provides an LED control device comprising: a power supply unit connected to a first driving node and a second driving node that receive driving power from an LED driver, wherein the light source module includes a first LED string and a second LED string connected in parallel and emitting light with different color temperatures; a square wave generator that operates by the power supply unit and generates a square wave; a duty cycle controller that outputs a control signal by integrating the square wave generated by the square wave generator and outputs a change in the slope of the control signal in response to a change in the time constant; and a switch unit having first and second switch elements that control the current supplied to the first and second LED strings, respectively, according to the first and second PWM signals, wherein the switch unit operates by the power supply unit and outputs a first PWM signal in which the timing of triggering changes according to the change in the slope of the control signal output from the duty cycle controller, and a second switch driver that inverts and outputs the first PWM signal output from the first switch driver.

[0009] One embodiment of the present invention provides a lighting device comprising: an LED driver that generates a driving power for driving LEDs using an AC power source and outputs the driving power through a first driving node and a second driving node; a light source module that is turned on by the driving power and includes a first LED string emitting light of a first color temperature and a second LED string emitting light of a second color temperature; and an LED control device having a power supply unit connected to the first driving node and the second driving node, a square wave generator that operates by the power supply unit and generates a square wave, a duty ratio controller that integrates the square wave generated by the square wave generator and outputs it as a control signal, and outputs a change in the slope of the control signal in response to a change in a time constant, and a switch unit that operates by the power supply unit and controls the current ratio of the current applied to the first LED string and the current applied to the second LED string according to the change in the slope of the control signal. Effects of the invention

[0011] According to one embodiment of the present invention, a color temperature control function of a lighting device can be additionally implemented by connecting an LED control device to driving nodes that connect an LED driver and a light source module, without the need to replace or upgrade the LED driver included in the existing lighting device. Therefore, a lighting device that maximizes user convenience while minimizing waste of existing installed devices can be implemented.

[0012] The various and beneficial advantages and effects of the present invention are not limited to those described above and will be more easily understood in the process of explaining specific embodiments of the present invention. Brief explanation of the drawing

[0014] FIG. 1 is a simplified block diagram of a lighting device according to one embodiment of the present invention. Figures 2(a) and 2(b) are examples of variations of the lighting device of Figure 1. FIG. 3 is a simplified block diagram of an LED control device according to one embodiment of the present invention. FIG. 4 is a block diagram showing in detail a part of the configuration of the LED control device of FIG. 3. Figure 5 is a modified example of the duty cycle control unit of Figure 3. FIGS. 6(a) to 8(c) are drawings provided to explain signals output from each part of an LED control device according to an embodiment of the present invention. FIG. 9 is a simplified block diagram of an LED control device according to one embodiment of the present invention. FIGS. 10(a) to 10(d) are drawings provided to explain signals output from each part of an LED control device according to an embodiment of the present invention. Specific details for implementing the invention

[0015] Hereinafter, preferred embodiments of the present invention are described as follows with reference to the attached drawings.

[0016] FIG. 1 is a simplified block diagram of a lighting device according to one embodiment of the present invention, and FIG. 2(a) and FIG. 2(b) are modified examples of the lighting device of FIG. 1.

[0018] Referring to FIG. 1, a lighting device (10) according to one embodiment of the present invention may include an LED driver (20) connected to a power source (1), a light source module (30), and an LED control device (40). The LED driver (20) is an AC power source (V) output by the power source (1). AC It receives ) and provides a driving power supply (V) for driving LEDs included in the light source module (30). DRV ) can output. For example, the LED driver (20) can output a driving current (I) for driving the LEDs. LED) can output a constant current. The LED driver (20) can output a driving power supply (V) through the first driving node (21) and the second driving node (22). DRV Can output ).

[0019] The LED driver (20) is an AC power source (V) output by the power source (1). AC A rectifier circuit that rectifies ) into a DC power source, and a driving power source (V) using the rectified DC power source. DRV It may include a converter circuit that generates ). According to embodiments, an EMI (Electro-Magnetic Interference) filter, etc. may be further connected between the power supply (1) and the rectifier circuit. The structure and operation of the LED driver (20) will be described later.

[0020] The light source module (30) includes a plurality of LEDs, and the plurality of LEDs may provide at least two LED strings with different color temperatures. For example, the plurality of LEDs may include first LEDs that emit light of a first color temperature and second LEDs that emit light of a second color temperature different from the first color temperature. For example, the first LEDs may output light of the Cool White series, and the second LEDs may output light of the Warm White series. The first LEDs may provide at least one first LED string, and the second LEDs may provide at least one second LED string. The first LED string and the second LED string may be connected in parallel with each other. However, the number of LED strings included in the light source module (30) is not necessarily limited to two.

[0021] The LED control device (40) may include a power supply unit, a square wave generator unit, a duty cycle controller unit, a switch unit, etc. The power supply unit includes a driving power supply (V DRVAn internal power voltage required for the operation of the square wave generator and the switch unit can be generated using the square wave generator, and the square wave generator can generate a square wave having a constant period and wavelength. The duty cycle control unit can convert the square wave output from the square wave generator into a triangular wave and output it as a control signal to control the switch unit. The switch unit can operate in response to the control signal of the duty cycle control unit. For example, the switch unit is directly connected to the light source module (30) and can control a plurality of LEDs included in the light source module (30) in response to the control signal.

[0022] In one embodiment illustrated in FIG. 1, the LED control device (40) may be implemented on a separate package substrate from the LED driver (20) and the light source module (30). Accordingly, the LED control device (100) can be optionally added to an existing lighting device implemented with the LED driver (20) and the light source module (30), and the additional functions provided by the LED control device (40) can be implemented in the lighting device while utilizing the components of the existing lighting device as they are.

[0023] However, this is not limited thereto, and depending on the embodiment, the LED control device (40) may be included in the LED driver (20) or in the light source module (30). For example, as shown in FIG. 2(a), the LED control device (40) may be implemented on a single package substrate with the LED driver (20A) of the lighting device (10A). Also, as shown in FIG. 2(b), the LED control device (40) may be implemented on a single package substrate with the light source module (30A) of the lighting device (10B).

[0025] FIG. 3 is a simplified block diagram of an LED control device according to an embodiment of the present invention, and FIG. 4 is a block diagram showing in detail a part of the configuration of the LED control device of FIG. 3. The LED control device of FIG. 3 is an example of the LED control device shown in FIG. 1.

[0026] Referring to FIGS. 3 and 4, an LED control device (100) according to one embodiment of the present invention may include a power supply unit (110), a square wave generator (120), a duty cycle control unit (130), and a switch unit (140), etc.

[0028] The power supply unit (110) is the driving power (V) output by the LED driver. DRV Using ) the internal power voltage (V) required for the operation of the square wave generator (120) and the switch unit (140) INT1 , V INT2 ) can be generated. According to embodiments, the operating voltage of the square wave generator (120) and the operating voltage of the switch unit (140) may be different from each other, and the power supply unit (110) may supply a first internal power supply voltage (V) to the square wave generator (120). INT1 ) supplies, and the second internal power voltage (V) to the switch unit (140). INT2 ) can be supplied. The power supply unit (110) can supply a first internal power supply voltage (V INT1 A first regulator generating ) and a second internal power supply voltage (V INT2 It may include a second regulator that generates ).

[0030] The square wave generator (120) has a first internal power supply voltage (V INT1 It can operate by receiving input and can generate a square wave (SS) having a constant period and wavelength. The square wave generator (120) may include a first Schmitt trigger inverter (U1), a first capacitor (C1), and a first resistor (R1). The first capacitor (C1) may be connected between the second driving node (102) and the input terminal of the first Schmitt trigger inverter (U1). The first resistor (R1) is a feedback resistor, is connected to the output terminal of the first capacitor (C1), and may be connected in parallel with the first Schmitt trigger inverter (U1).

[0032] The square wave generator (120) of one embodiment has the advantage of being able to be configured with a small number of components. In addition, the square wave generator (120) of one embodiment can set the frequency of the generated square wave (SS) through a time constant determined by the resistance component of the first resistor (R1) and the capacitor component of the first capacitor (C1). Therefore, the square wave generator (120) of one embodiment can change the frequency of the square wave (SS) only by changing the time constant of the first capacitor (C1) and the first resistor (R1). Thus, when acoustic noise occurs in the light source module (30), the noise can be eliminated by changing the frequency of the square wave (SS) to tens of kHz or more, thereby using a square wave (SS) of a specific frequency band. Therefore, the square wave generator (120) of one embodiment can supply a square wave (SS) with a wider variable frequency range compared to the case where a square wave is generated using a separate micro controller unit.

[0034] The duty cycle control unit (130) may be positioned between the output terminal of the square wave generator (120) and the input terminal of the switch unit (140). The duty cycle control unit (130) may convert the square wave (SS) output from the square wave generator (120) into a triangular wave and output it as a control signal (CTR) to control the switch unit (140), and may change the slope of the triangular wave. The duty cycle control unit (130) may be a so-called T-filter having three nodes, and a second resistor (R2), a second capacitor (C2), and a first variable resistor (R3) may be positioned at each node. The second resistor (R2) may be connected to the output terminal of the square wave generator (120), and the second capacitor (C2) may be connected between the second resistor (R2) and the second driving node (102). The first variable resistor (R3) can be connected between the second capacitor (C2) and the input terminal of the switch unit (140). In one embodiment, the duty cycle control unit (130) can transform a square wave input to the duty cycle control unit (130) into a triangular wave through a time constant determined by the resistance component of the second resistor (R2) and the capacitor component of the second capacitor (C1). Additionally, the duty cycle control unit (130) can change the slope of the output triangular wave by changing the size of the first variable resistor (R3). When the slope of the output triangular wave from the duty cycle control unit (130) is changed, the time it takes for the Schmitt trigger inverter to reach the trigger level can be adjusted by the control signal (CTR) input to the Schmitt trigger inverter included in the switch unit (140) connected to the output terminal, and thereby the duty cycle of the PWM signal supplied to the light source module (30) can be adjusted. This will be described later. The first variable resistor (R3) may be implemented as a single variable resistor element, but is not limited thereto. For example, as shown in FIG. 5, the first variable resistor may include a third resistor (R3-1) and a plurality of resistors (R3-2 to R3-4) arranged in parallel with the third resistor (R3-1) and selected by a switch.

[0036] The switch unit (140) is connected to the light source module (30), and the first current (I) flowing through the first LED string (31) included in the light source module (30) LED1 ) and the second current (I) flowing through the second LED string (32) LED2 By controlling the current ratio of the light source module (30), the color temperature of the light emitted from the light source module (30) can be controlled. The light source module (30) may include a first LED string (31) and a second LED string (32) connected in parallel with each other. The first LED string (31) may include first LEDs (LED1), and the second LED string (32) may include second LEDs (LED2). For example, the first LED string (31) may output cool white light, and the second LED string (32) may output warm white light.

[0037] The switch unit (140) may include a switch driver unit and a switch element unit. The switch driver unit (141, 142) may generate a Pulse Width Modulation (PWM) signal that controls the on / off of the switch element according to a control signal (CTR) input from the duty cycle control unit (130). The turn-on time and turn-off time of the switch element unit (143, 144) may be determined by the duty cycle of the PWM signal of the switch driver unit (141, 142).

[0038] The switch element section (143, 144) can be turned on / off according to the PWM signal of the switch driver section to control the current applied to the light source module (30). The switch driver section (141, 142) and the switch element section (143, 144) can each be arranged in a number corresponding to the number of LED strings included in the light source module (30).

[0039] In one embodiment, the switch driver section (141, 142) may include a first switch driver (141) and a second switch driver (142). The first switch driver (141) may output a first PWM signal (PWM1) for controlling a first switch element (143), and the second switch driver (142) may output a second PWM signal (PWM2) for controlling a second switch element (144). The switch element section (143, 144) may include a first switch element (143) controlled by the first switch driver (141) and a second switch element (144) controlled by the second switch driver (142).

[0040] The first switch driver (141) and the second switch driver (142) may each include one Schmitt trigger inverter (U2, U3). For example, the first switch driver (141) may include a second Schmitt trigger inverter (U2), and the second switch driver (142) may include a third Schmitt trigger inverter (U3). The second Schmitt trigger inverter (U2) and the third Schmitt trigger inverter (U3) may be of the same type. Since the timing at which the first switch driver (141) reaches the trigger level varies depending on the slope of the control signal (CTR) input from the duty cycle control unit (130), the duty cycle of the first PWM signal (PWM1) output from the first switch driver (141) may be varied. For example, if the slope of the input control signal (CTR) is steep, the time it takes for the first switch driver (141) to reach the trigger level is shortened, so the duty cycle of the first PWM signal (PWM1) decreases. On the other hand, if the slope of the control signal (CTR) is gentle, the time it takes for the first switch driver (141) to reach the trigger level is longer, so the duty cycle of the first PWM signal (PWM1) increases.

[0041] The second switch driver (142) can output an inverted first PWM signal (PWM1) output from the first switch driver (141). That is, the second switch driver (142) can output a second PWM signal (PWM2) that has the same magnitude and has an opposite phase to the first PWM signal (PWM1). Therefore, when the duty cycle of the first PWM signal (PWM1) increases, the duty cycle of the second PWM signal (PWM2) decreases, and when the duty cycle of the first PWM signal (PWM1) decreases, the duty cycle of the second PWM signal (PWM2) increases. Since the first LED string (31) and the second LED string (32) are driven complementarily by the first switch driver (141) and the second switch driver (142), the color temperature of the light emitted from the light source module (30) can be adjusted.

[0043] FIGS. 6(a) to 8(c) are drawings provided to explain signals output from each part of an LED control device according to an embodiment of the present invention.

[0044] With reference to the illustrated block diagram of FIG. 4 and FIGS. (a) through FIGS. 8(c), the signals output from each part of the LED control device (40) will be described.

[0045] FIG. 6(a) is a diagram illustrating a square wave output from the square wave generator (120) of FIG. 4. The frequency of the square wave output from the first Schmitt trigger inverter (U1) of the square wave generator (120) can be set through the + trigger level and - trigger level of the first Schmitt trigger inverter (U1), the resistance component of the first resistor (R1), and the capacitor component of the second capacitor (C2). If the frequency of the square wave is set to a low frequency of several hundred Hz or less, a flicker phenomenon in which the light emitted from the light source module (30) blinks slightly, or a shimmer phenomenon in which the light emitted from the light source module (30) ripples may occur. In this case, the frequency of the square wave can be increased to improve the situation.

[0046] 6(b) is a diagram showing the voltage applied to both ends of the second capacitor (C2) of the duty cycle control unit (130) of FIG. 4. It can be seen that the square wave output from the square wave generator (120) is integrated to produce a triangular wave.

[0047] FIG. 7(a) illustrates a control signal (CTR) input to the input terminal of the first switch driver (141). The control signal (CTR) input to the first switch driver (141) is triggered by the +trigger level (Vt+) and -trigger level (Vt-) of the second Schmitt trigger inverter (U2) included in the first switch driver (141), and can be output as a first PWM signal (PWM1) to the output terminal of the first switch driver (141). The first PWM signal (PWM1) is output during the first turn-on time (T) of the period (TD). ON1 The first switch element (143) can be turned on during )

[0048] The second switch driver (142) is connected to the output terminal of the first switch driver (141) and can receive the first PWM signal (PWM1) output from the first switch driver (141). The second switch driver (142) can invert the first PWM signal (PWM1) and output it as a second PWM signal (PWM2). As shown in FIG. 7(c), since the second PWM signal (PWM2) is a signal obtained by inverting the first PWM signal (PWM1), the first turn-on time (T) during the period (TD) ON1 Second turn-on time (T excluding ) ON2 The second switch element (144) can be turned on during ). Since the first switch element (143) and the second switch element (144) are turned on complementarily to each other, the first LED string (31) and the second LED string (32), whose current is controlled by the first switch element (143) and the second switch element (144), can also be turned on complementarily.

[0050] Next, with reference to FIGS. 8(a) to 8(c), the process of the current applied to the first LED string (31) and the second LED string (32) changing as the slope of the control signal (CTR) changes will be explained.

[0051] FIG. 8(a) illustrates a control signal (CTR) input to the input terminal of the first switch driver (141). Compared to the control signal (CTR) illustrated in FIG. 7(a) described earlier, there is a difference in that the slope of the control signal (CTR) is reduced. It can be seen that the slope of the control signal (CTR) illustrated in FIG. 8(a) is gentler because the amplitude of the triangular wave is reduced compared to the control signal (CTR) illustrated in FIG. 7(a). Additionally, compared to the control signal (CTR) in FIG. 7(a), it can be seen that the timing of triggering by the +trigger level (Vt+) and the -trigger level (Vt-) has changed. Specifically, the timing of reaching the +trigger level (Vt+) is delayed, so compared to FIG. 7(b), the first PWM signal (PWM1) has a third turn-on time (T), which is the time during the period (TD) when the first switch element (143) is turned on. ON3 It can be seen that ) has increased compared to the first PWM signal (PWM1) of Fig. 7(b) examined earlier. Therefore, it can be confirmed that as the slope of the control signal (CTR) becomes gentler, the turn-on time of the first PWM signal (PWM1) increases. On the other hand, the fourth turn-on time (T), which is the turn-on time of the second PWM signal (PWM2), ON4 ) is the second turn-on time (T) of Fig. 7(c) examined earlier. ON2 It can be seen that it has decreased compared to ). Therefore, it can be confirmed that when the slope of the control signal (CTR) becomes gentler, the turn-on time of the second PWM signal (PWM2) decreases. From this, it can be seen that the turn-on time of the first LED string (31) and the second LED string (32) can be adjusted by changing the slope of the triangular wave included in the control signal (CTR).

[0053] With reference to FIGS. 9 to 10(d), an LED control device according to one embodiment will be described. FIG. 9 is a simplified block diagram of an LED control device according to one embodiment of the present invention, and FIGS. 10(a) to 10(d) are drawings provided to explain signals output from each part of an LED control device according to one embodiment of the present invention.

[0054] The LED control device (100A) illustrated in FIG. 9 has a different duty cycle control unit (130') compared to the LED control device (100) of FIG. 3 examined earlier. Since the other components are identical to the LED control device (100) described in FIG. 3, a detailed description is omitted.

[0055] The duty cycle control unit (130') according to one embodiment has the difference of including a low-pass filter (130A) and a comparator (130B). Compared to the duty cycle control unit (130) of the previously described embodiment, the comparator is additionally included, so additional power must be supplied through the power supply unit (110), but it has the advantage of being able to control the duty cycle more precisely than the LED control device of the previously described embodiment. This will be explained with reference to FIGS. 10(a) to 10(d).

[0056] FIG. 10(a) is a diagram illustrating the voltage applied to the low-pass filter (130A). V R Figure 10(b) illustrates the reference potential applied to the comparator (130B). Figure 10(b) illustrates the control signal (CTR) output from the output terminal of the comparator (130B). The reference potential (V) of the comparator (130B) R It can be seen that voltage components of a magnitude lower than ) are removed, and only the upper signal of the triangular wave is output. While the previously described embodiment adjusts the control signal (CTR) input to the first switch driver (141) by changing only the slope of the control signal (CTR), one embodiment adjusts the slope of the control signal (CTR) and the reference potential (V) of the comparator (130B).R There is a difference in that the control signal (CTR) input to the first switch driver (141) is adjusted using ). The point at which the first switch driver (141) reaches the trigger level is determined by the slope of the control signal (CTR) and the reference potential (V) of the comparator (130B). R It can be determined by ). Accordingly, the fifth turn-on time (T), which is the turn-on time of the first PWM signal (PWM1) of one embodiment, ON5 ) and the 6th turn-on time (T), which is the turn-on time of the 2nd PWM signal (PWM2). ON6 ) is the slope of the control signal (CTR) and the reference potential (V) of the comparator (130B). R Since it is controlled by ), it has the advantage of being able to control the duty cycle more precisely compared to the LED control device of the previously described embodiment.

[0058] The present invention is not limited by the embodiments described above and the attached drawings, but is intended to be limited by the appended claims. Accordingly, various substitutions, modifications, and changes may be made by those skilled in the art within the scope of the technical concept of the present invention as described in the claims, and such are also to be considered to fall within the scope of the present invention. Explanation of the symbols

[0060] 10: Lighting device 20, 100: LED driver 30: Light source module 40: LED control unit 110: Power supply 120: Square wave generator 130: Duty control unit 140: Switch section

Claims

Claim 1 An LED control device comprising: a light source module including a first LED string that outputs light of a first color temperature and a second LED string that outputs light of a second color temperature, a power supply unit connected to a first driving node and a second driving node that receive driving power from an LED driver; a square wave generator that operates by a first internal power voltage output by the power supply unit and generates a square wave; a duty ratio controller that integrates the square wave generated by the square wave generator unit and outputs it as a control signal, and outputs a change in the slope of the control signal in response to a change in a time constant; and a switch unit that operates by a second internal power voltage output by the power supply unit, wherein the switch driver unit includes a first switch driver and a second switch driver, and controls the current ratio of the current applied to the first LED string and the current applied to the second LED string by adjusting the time at which the first switch driver reaches a trigger level according to a change in the slope of the control signal. Claim 2 The LED control device according to claim 1, wherein the switch unit comprises a switch element unit having first and second switch elements that are disposed between the light source module and the second driving node and control the current supplied to the first and second LED strings, respectively; wherein the first switch driver is disposed between the duty cycle control unit and the switch element unit, operates by the second internal power supply voltage, and outputs a first PWM (Pulse Width Modulation) signal that controls the first switch element based on the control signal, and the second switch driver is connected to the output terminal of the first switch driver, receives the first PWM signal, and outputs a second PWM signal that is inverted from the first PWM signal to control the second switch element. Claim 3 In paragraph 2, the LED control device wherein the first PWM signal and the second PWM signal have opposite phases and are of the same magnitude. Claim 4 An LED control device according to claim 2, wherein when the first switch element is turned on, the second switch element is turned off, and when the second switch element is turned on, the first switch element is turned off. Claim 5 In claim 1, the square wave generating unit comprises a first Schmitt trigger inverter connected to the input terminal of the duty cycle control unit, a first capacitor connecting the input terminal of the first Schmitt trigger inverter to the second driving node, and a first resistor element connecting the input terminal of the first Schmitt trigger inverter to the output terminal, and the square wave is an LED control device in which the frequency is determined by a time constant determined by the resistance component of the first resistor element and the capacitor component of the first capacitor. Claim 6 In paragraph 2, the duty cycle control unit comprises a second resistor element connected to the output terminal of the square wave generator, a second capacitor element connected between the second resistor element and the second driving node, and a first variable resistor element connected between the second resistor element and the first switch driver, wherein the time constant changes according to the change in the resistance component of the first variable resistor element. Claim 7 In paragraph 2, the duty cycle control unit includes a low-pass filter connected to the output terminal of the square wave generator and a comparator connecting the low-pass filter and the switch unit, and the low-pass filter includes a second resistor element connected to the output terminal of the square wave generator and a second capacitor element connected between the second resistor element and the second driving node, and the time constant is determined by the resistance component of the second resistor element and the capacitor component of the second capacitor element, in an LED control device. Claim 8 In paragraph 2, the first and second switch drivers each comprise a second and third Schmitt trigger inverter, respectively, in an LED control device. Claim 9 In paragraph 8, the second and third Schmitt trigger inverters are LED control devices of the same type. Claim 10 In claim 1, the power supply unit includes a first regulator that generates the first internal power supply voltage and a second regulator that generates the second internal power supply voltage, and the first internal power supply voltage and the second internal power supply voltage have different magnitudes, in an LED control device. Claim 11 An LED control device comprising: a power supply unit connected to a first driving node and a second driving node that receive driving power from an LED driver, wherein the light source module including a first LED string and a second LED string connected in parallel and emitting light of different color temperatures; a square wave generator that operates by the power supply unit and generates a square wave; a duty cycle controller that outputs a control signal by integrating the square wave generated by the square wave generator and outputs a change in the slope of the control signal in response to a change in the time constant; and a switch unit having first and second switch elements that control the current supplied to the first and second LED strings, respectively, according to the first and second PWM signals, wherein the switch unit operates by the power supply unit and outputs a first PWM signal in which the timing triggered by the change in the slope of the control signal output from the duty cycle controller changes, and inverts and outputs the first PWM signal output from the first switch driver. Claim 12 In paragraph 11, the first and second switch drivers each comprise an LED control device including a Schmitt trigger inverter. Claim 13 In claim 11, the duty cycle control unit comprises a second resistor element connected to the output terminal of the square wave generator, a second capacitor element connected between the second resistor element and the second driving node, and a first variable resistor element connected between the second resistor element and the first switch driver, wherein the slope of the control signal changes according to the change in the resistance component of the first variable resistor element, an LED control device. Claim 14 In claim 11, the duty cycle control unit comprises a low-pass filter connected to the output terminal of the square wave generator and a comparator connecting the low-pass filter and the first switch driver, wherein the low-pass filter comprises a second resistor element connected to the output terminal of the square wave generator and a second capacitor element connected between the second resistor element and the second driving node, and the slope of the control signal is determined by the resistance component of the second resistor element and the capacitor component of the second capacitor element. Claim 15 An LED driver that generates a driving power for driving LEDs using AC power and outputs the driving power through a first driving node and a second driving node; a light source module that is turned on by the driving power and includes a first LED string emitting light of a first color temperature and a second LED string emitting light of a second color temperature; and a switch unit that operates by a second internal power voltage output by the power supply unit, comprising a power supply unit connected to the first driving node and the second driving node, a square wave generator unit that operates by the power supply unit and generates a square wave, a duty cycle controller unit that integrates the square wave generated by the square wave generator unit and outputs it as a control signal, and outputs a change in the slope of the control signal in response to a change in the time constant, and a switch driver unit; A lighting device comprising a switch driver unit including a first switch driver and a second switch driver, and an LED control device that controls the current ratio of the current applied to the first LED string and the current applied to the second LED string by adjusting the time at which the first switch driver reaches a trigger level according to a change in the slope of the control signal. Claim 16 In claim 15, the switch unit further comprises a switch element unit having first and second switch elements that are disposed between the light source module and the second driving node and control the current supplied to the first and second LED strings, respectively; wherein the first switch driver is disposed between the duty cycle control unit and the switch element unit and outputs a first PWM (Pulse Width Modulation) signal that controls the first switch element based on the control signal, and the second switch driver is connected to the output terminal of the first switch driver, receives the first PWM signal, and outputs a second PWM signal that is inverted from the first PWM signal to control the second switch element. Claim 17 A lighting device according to claim 16, wherein when the first LED string is turned on, the second LED string is turned off, and when the second LED string is turned on, the first LED string is turned off. Claim 18 In claim 16, the duty cycle control unit comprises a second resistor element connected to the output terminal of the square wave generator, a second capacitor element connected between the second resistor element and the second driving node, and a first variable resistor element connected between the second resistor element and the first switch driver, and a lighting device in which the time constant changes according to a change in the resistance component of the first variable resistor element. Claim 19 In claim 16, the duty cycle control unit comprises a low-pass filter connected to the output terminal of the square wave generator and a comparator connecting the low-pass filter and the switch unit, wherein the low-pass filter comprises a second resistor element connected to the output terminal of the square wave generator and a second capacitor connected between the second resistor element and the second driving node, and the lighting device wherein the time constant is determined by the resistance component of the second resistor element and the capacitor component of the second capacitor. Claim 20 In claim 15, the LED driver comprises a rectifier circuit that rectifies the AC power supply and a converter circuit that generates the driving power supply using the output of the rectifier circuit.

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