KR20180128547A - Hybrid control type ac direct driving led apparatus - Google Patents

Abstract

The present invention provides an LED device comprising: an N (N is a natural number of 2 or more) number of LED modules connected in series; a rectifying unit for providing rectified voltage; an N number of power switches for controlling electrical connection of an input node or an output node of each LED module with a common node electrically connected to the rectifying unit; an inductor connected in series with the rectifying unit and the LED module; a control unit for selecting one power switch among the N number of power switches to change the number of the LED modules turned on according to the magnitude of the rectified voltage, linearly controlling the one power switch in a first time period, and controlling a pulse width modulation (PWM) in a second time period; and a diode for providing a circulation path of a current flowing in the inductor when the one power switch is turned off.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a hybrid control type AC direct drive LED device,

The present invention relates to an LED device. And more particularly to a technique for driving a plurality of LED modules connected in series with each other.

An LED is a semiconductor device that emits light by flowing current to a compound (for example, gallium arsenide) in another expression of a light emitting diode (LED). Recently, a semiconductor device using an electroluminescent phenomenon that emits light when a current flows in a fluorescent organic compound has been developed as an organic light emitting diode (OLED). Such an organic light emitting diode (OLED) It can be seen as a kind.

LEDs can save up to 90% of energy because of the high efficiency of converting electrical energy into light energy. As a result, attention has been paid to a next-generation light source that can replace incandescent and fluorescent lamps whose energy efficiency is only about 5%.

In order to drive the LED, the driver must supply a voltage equal to or higher than the threshold voltage VTH to the LED, and conventionally, such a voltage is supplied as a direct current (DC).

Accordingly, a separate power conversion circuit is required for the LED driving device.

For example, a PFC (Power Correction Circuit) and a DC / DC converter have been essentially used in the case of a conventional LED driving apparatus for generating a voltage for driving an LED from a commercial power source having an AC form.

Here, the PFC performs the function of rectifying the AC voltage and the function of maintaining the power factor within a predetermined range, and the DC / DC converter converts the high-voltage DC voltage generated by the PFC into a voltage suitable for the LED Respectively.

Conventional incandescent lamps and fluorescent lamps are being replaced by LED devices for environmentally friendly energy consumption. However, a conventional LED device requires a separate power conversion device, for example, a PFC and a DC / DC converter as described above, which is a problem in terms of cost.

In view of the foregoing, it is an object of the present invention to provide a technique relating to an apparatus for driving an LED using an AC voltage directly.

In order to achieve the above-mentioned object, in one aspect, the present invention provides a light emitting device comprising: N LED modules (N is a natural number of 2 or more) connected in series; A rectifying section for providing a rectified voltage; N power switches for controlling electrical connection between a common node electrically connected to the rectifying unit and an input node or an output node of each LED module; An inductor connected in series with the rectifying part and the LED module; One of the N power switches is selected so that the number of the LED modules turned on according to the magnitude of the rectified voltage is changed, and the one power switch is linearly controlled in a first time period, A controller for controlling PWM (Pulse Width Modulation); And a diode for providing a circulating path of current flowing in the inductor when the one power switch is turned off.

In such an LED device, the one power switch, the inductor and the diode may be operated as a buck converter. And, the second time interval may follow the first time interval.

According to another aspect of the present invention, there is provided an image processing apparatus comprising: N LED modules (N is a natural number of 2 or more) connected in series; A rectifying section for providing a rectified voltage; A power switch for controlling electrical connection between the N LED modules and the rectifying part; N-1 bypass switches connected in parallel to the different numbers of the LED modules, an inductor connected in series with the rectifying part and the LED module, One of the N-1 bypass switches is turned on so that the number of the LED modules turned on according to the magnitude of the rectified voltage is changed, the power switch is linearly controlled in the first time interval, A PWM (Pulse Width Modulation) control unit; And a diode for providing a circulating path of a current flowing in the inductor when the power switch is turned off. As described above, according to the present invention, it is possible to reduce the number of parts and reduce the cost by directly using an AC voltage for driving an LED (LED).

Fig. 1 shows a configuration of a general LED device.
Fig. 2 shows the voltage and current waveforms of the LED device shown in Fig.
Fig. 3 shows a configuration of an LED device according to the first embodiment.
4 shows the voltage and current waveforms of the LED device according to the first embodiment.
5 is an internal configuration example of the LED module.
6 is a main waveform diagram of an LED device according to the first embodiment.
7 is a diagram showing a driving waveform according to the first embodiment.
8 and 9 show current paths when the first power switch is PWM controlled.
Figs. 10 and 11 show current paths when the second power switch is PWM-controlled.
12 is a view showing a structure in which capacitors are connected in parallel to an LED module.
13 shows a current path when the second power switch is turned off in a structure in which a capacitor is further added.
14 is a diagram illustrating an internal configuration of the control unit.
15 shows a configuration of an LED device according to the second embodiment.
16 shows a configuration of an LED device according to the third embodiment.
17 shows a configuration of an LED device according to the fourth embodiment.
18 shows a configuration of an LED device according to the fifth embodiment.

Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. It should be noted that, in adding reference numerals to the constituent elements of the drawings, the same constituent elements are denoted by the same reference symbols as possible even if they are shown in different drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

In describing the components of the present invention, terms such as first, second, A, B, (a), and (b) may be used. These terms are intended to distinguish the constituent elements from other constituent elements, and the terms do not limit the nature, order or order of the constituent elements. When a component is described as being "connected", "coupled", or "connected" to another component, the component may be directly connected to or connected to the other component, It should be understood that an element may be "connected," "coupled," or "connected."

Fig. 1 shows the configuration of a general LED device, and Fig. 2 shows voltage and current waveforms of the LED device shown in Fig.

Referring to FIG. 1, the LED device 10 may drive an LED while adjusting the number of LEDs driven according to the magnitude of the input AC voltage Vac.

On the other hand, according to this driving, a difference occurs between the rectified voltage and the voltage applied to the LED because the LED is discretely selected. This difference appears as a loss of power, which causes the efficiency of the LED device 10 to be lowered.

Further, according to such a drive, since the LED (LED) operates in a discrete manner, the current (LED current) applied in the AC power network also has a discrete form. The current (LED current) having such a discrete shape causes the power factor of the LED device 10 to be lowered.

According to an embodiment of the present invention, there is provided a technique for minimizing a loss region by linearly controlling a drive switch or controlling a PWM (Pulse Width Modulation) to improve the above problems.

According to an embodiment to which such control is applied, there is an effect that the efficiency of the LED device is improved and the power factor is improved.

Fig. 3 shows a configuration of an LED device according to the first embodiment.

Referring to FIG. 3, the LED device 100 directly drives the LED module using the AC voltage Vac.

The LED device 100 includes a rectifier 190, a controller 110, a diode D1, an inductor L1, power switches Q1, Q2, Q3 and Q4, and LED modules LEDM1, LEDM2 and LEDM3 , LED M4), and the like.

The LED device 100 may include N (N is a natural number of 2 or more) LED modules connected in series with each other. For convenience of explanation, it is assumed that the LED device 100 includes four LED modules (LEDM1, LEDM2, LEDM3, LEDM4).

The LED device 100 may include a rectifying unit 190 for rectifying the AC voltage Vac. The rectifying unit 190 rectifies an AC voltage Vac supplied from an AC power source, for example, a commercial power grid to generate a rectified voltage Vac.

The LED device 100 may include N power switches. The number of power switches may be the same as the number of LED modules. Hereinafter, for convenience of explanation, it is assumed that the LED device 100 includes four power switches Q1, Q2, Q3, and Q4.

The LED device 100 may include a control unit 110 for controlling on / off of the power switches Q1, Q2, Q3 and Q4 or controlling the power switches Q1, Q2, Q3 and Q4 in a linear region.

Controlling the power switches Q1, Q2, Q3 and Q4 in the linear region means that the power switches Q1, Q2, Q3 and Q4 are turned on completely or not completely, Q4) The current passing through both ends is controlled so as to be proportional to the voltage across both ends of the power switches Q1, Q2, Q3, Q4.

The LED device 100 may include an inductor L1, a diode D1 and a current sensor Rs.

The inductor L1 may be connected in series with the rectifier 190 and the LED modules LEDM1, LEDM2, LEDM3, and LEDM4. The rectified current irec supplied from the rectifying unit 190 can be supplied to the LED modules LEDM1, LEDM2, LEDM3, and LEDM4 via the inductor L1. The rectifier voltage Vrect is connected to one side of the inductor L1 and the voltage of the LED modules LEDM1, LEDM2, LEDM3 and LEDM4 is connected to the other side of the connection so that the inductor voltage (VL) is determined. The shape of the current iL flowing to the inductor L1 is determined by this inductor voltage VL.

The power switches Q1, Q2, Q3, and Q4 may be electrically connected to one common node N2 on one side. The other side of the power switches Q1, Q2, Q3, and Q4 may be electrically connected to the input node or the output node of each of the LED modules LEDM1, LEDM2, LEDM3, and LEDM4. For example, one side of the first power switch Q1 may be connected to the common node N2 and the other side may be electrically connected to the output node of the first LED module LEDM1. One side of the fourth power switch Q4 may be connected to the common node N2 and the other side may be electrically connected to the output node of the fourth LED module LEDM4. N, one side of the Nth power switch Qn may be electrically connected to the common node N2 and the other side may be electrically connected to the output node of the Nth LED module LEDMn.

Since the LED modules (LEDM1, LEDM2, LEDM3, LEDM4) are connected in series with each other, the input node or the output node of one LED module may be the output node or the input node of another LED module. For example, the output node of the first LED module LEDM1 is the input node of the second LED module LEDM2, and the output node of the second LED module LEDM2 is the input node of the third LED module LEDM3 have.

The power switches (Q1, Q2, Q3, Q4) are connected to the intersection of two LED modules so that the current paths of the two LED modules can be branched. For example, the first power switch Q1 electrically connects the intersection point of the first LED module LEDM1 and the second LED module LEDM2 with the common node N2, thereby electrically connecting the current iLED1 flowing to the first LED module, Can be branched.

According to this arrangement of the power switches Q1, Q2, Q3, and Q4, the LED device 100 may be configured such that a current path is formed only in a selected M (M is a natural number less than or equal to N) LED modules among N LED modules . For example, the LED device 100 may turn on the first power switch Q1 connected to the output node of the first LED module LEDM1 disposed at the top and turn off the other power switches. In this case, the LED modules connected to the other power switches are disconnected from the current path, and a current path can be formed only through the first LED module (LEDM1). The LED device 100 may turn on the second power switch Q2 connected to the output node of the second LED module LEDM2 disposed adjacent to the first LED module LEDM1 and turn off the other power switches . In this case, the LED modules connected to the lower side of the second LED module LED2 are cut off and the current path can be formed only in the first LED module LEDM1 and the second LED module LEDM2. In this manner, the LED device 100 can turn on the M th power switch connected to the output node of the M th M th LED module and turn off the other power switches. In this case, the current is cut off by the LED module connected to the lower side of the Mth LED module, and a current path can be formed only from the first LED module to the Mth LED module.

The common node N2 may be electrically connected to the rectifier 190. The rectifier 190 may include a high voltage terminal and a low voltage terminal-for example, a ground voltage terminal. In the embodiment shown in FIG. 3, the common node N2 is electrically connected to the low voltage terminal of the rectifier 190 .

The controller 110 selects and controls one of the N power switches so that the number of the LED modules LEDM1, LEDM2, LEDM3, and LEDM4 is turned on according to the magnitude of the rectified voltage Vrect, Turn on - you can.

Since the rectified voltage Vrect is generated by rectifying the AC voltage, the rectified voltage Vrect is changed in size with time. The control unit 110 may control the N power switches so that the number of the LED modules LEDM1, LEDM2, LEDM3, and LEDM4 turned on according to the varying magnitude of the rectified voltage Vrect. For example, when the magnitude of the rectified voltage Vrect is the maximum, all the LED modules are turned on, and when the magnitude of the rectified voltage Vrect is greater than the threshold voltage of the minimum-LED module, , Only one LED module can be turned on.

Meanwhile, the controller 110 may control the selected power switch by PWM (Pulse Width Modulation).

Light emitting diodes (LEDs) can be adjusted in brightness as needed. In order to adjust the brightness of the LED, the amount of current supplied to the LED must be controlled. The controller 110 may control the amount of current supplied to the LED through the PWM control.

On the other hand, simply by turning the power switches Q1, Q2, Q3 and Q4 on and off, various problems may occur due to the disappearance of the current path supplied to the LED modules (LEDM1, LEDM2, LEDM3, LEDM4) have. For example, an overvoltage may be generated in the power switches Q1, Q2, Q3, and Q4 at the time of off, and the power switches Q1, Q2, Q3, and Q4 may be damaged. In addition, the LED modules (LEDM1, LEDM2, LEDM3, LEDM4) may be excessively blinked to provide inconvenience to the user. In addition, the power loss may be large and the efficiency may be lowered.

The LED device 100 according to the embodiment controls the power switches Q1, Q2, Q3 and Q4 in a buck-type manner by using the inductor L1 and the diode D1, The brightness of the module (LEDM1, LEDM2, LEDM3, LEDM4) can be adjusted.

The control unit 110 PWM-controls a selected one of the power switches. When the power switch is turned on, a current builds up in the inductor L1. When the control unit 110 turns off the corresponding power switch, the current built up in the inductor L1 is circulated through the diode D1. This is the method used in buck converter. The LED device 100 according to the embodiment selects the number of the appropriate LED modules LEDM1, LEDM2, LEDM3, LEDM4 according to the magnitude of the rectified voltage Vrect using the power switches Q1, Q2, Q3, At the same time, a buck converter can be implemented.

One side of the inductor L1 is electrically connected to one side of the uppermost LED module LEDM1 and the other side of the inductor L1 is connected to the cathode of the diode D1 and the high voltage Terminal. The anode of the diode D1 may be electrically connected to the other end of the uppermost LED module LED1 and the first power switch Q1.

Meanwhile, the control unit 110 can linearly control the selected power switch. The control unit 110 can control the amount of current supplied to the LED through the molding control.

4 shows the voltage and current waveforms of the LED device according to the first embodiment. In FIG. 3, four power switches are shown. In FIG. 4, three power switches are illustrated for convenience of explanation.

Referring to FIG. 4, the LED device can control the current applied to the LED through linear control and PWM control of the power switch. According to this control, since the current applied to the LED can be continuously increased or decreased, the current can have a continuous waveform like a sinusoidal wave.

The LED device can linearly control the first power switch Q1 in the first time interval T1 when the first power switch Q1 is controlled. In the subsequent second time period T2, the first power switch Q1 can be PWM-controlled. At this time, the voltage applied to the LED device at the end of the first time period T1 may be the same as the voltage applied to the LED device at the start time of the second time period T2.

When the LED device has a circuit configuration of a buck type, linear control is performed in the preceding time period (T1) and PWM control is performed in the following time period (T2) can do.

Through this control, a continuous waveform can be formed in the current, and the power efficiency and power factor of the LED device can be improved.

5 is an internal configuration example of the LED module.

Referring to FIG. 5, the LED module may be composed of one LED, or a plurality of LEDs may be connected in series. Also, the LED module may be configured by connecting a plurality of LEDs in series or in parallel.

Each of the LED modules shown in FIG. 3 may be formed in the same shape, but may be configured in different shapes, for example, different numbers of LEDs to be used or different arrangements of LEDs.

6 is a main waveform diagram of an LED device according to the first embodiment.

Referring to FIG. 6, the rectified voltage Vrect may have a sinusoidal waveform.

The rectified voltage Vrect has a voltage lower than the threshold voltage Vth1 of one LED module in the first time period t0 to t1. In the first time period (t0 to t1), since the LED module can not be turned on, the LED device turns off all of the LED modules. To turn off all of the LED modules, the LED device turns off all of the power switches Q1, Q2, Q3, and Q4.

The rectified voltage Vrect has a voltage that is larger than the threshold voltage Vth1 of one LED module and smaller than the two threshold voltages Vth2 of the LED module in the second time period t1 to t2. In the second time period (t1 to t2), the LED device turns on only the first LED module (LEDM1). At this time, the LED device can linearly control or PWM control the first power switch Q1.

In PWM control, duty can be constant over all time periods (fixed duty control). In this case, the diode voltage VD and the inductor voltage VL gradually increase in a time interval. When the inductor voltage VL increases, the magnitude of the current increases according to the magnitude of the voltage, Effect.

The rectified voltage Vrect has a voltage that is larger than the two threshold voltages Vth2 of the LED modules and smaller than the three threshold voltages Vth3 of the LED modules in the third time period t2 to t3. In the third time slot (t2 to t3), the LED device turns on only the first LED module (LEDM1) and the second LED module (LEDM2). At this time, the LED device can linearly control or PWM control the second power switch Q2.

The rectified voltage Vrect has a voltage that is larger than the three threshold voltages Vth3 of the LED modules and smaller than the four threshold voltages Vth4 of the LED modules in the fourth time period t3 to t4. In the fourth time period (t3 to t4), the LED device turns on only the first LED module (LEDM1), the second LED module (LEDM2) and the third LED module (LEDM3). At this time, the LED device can linearly control or PWM control the third power switch Q3.

The rectified voltage Vrect has a voltage higher than the four threshold voltages Vth4 of the LED modules in the fifth time period t4 to t5. In the fifth time period (t4 to t5), the LED device turns on all of the LED modules. At this time, the LED device can linearly control or PWM control the fourth power switch Q4.

When the LED device PWM controls one power switch, the remaining power switches can be turned off.

7 is a diagram showing a drive waveform according to the PWM control of the first embodiment.

The control unit can PWM control the power switch through the gate voltage (Vgs). The PWM control period Ts may be set to be less than the period of the alternating voltage-for example, 16.7 ms-, and may generally have a frequency of several KHz or more.

The power switch is turned on in the duty period DTs in one period Ts and turned off in the remaining period in accordance with the waveform of the gate voltage Vgs.

When the power switch is turned on, the inductor is supplied with a voltage (Vrect - sum (VLEDs)) obtained by subtracting the sum of the voltage of the LED modules turned on at the rectified voltage. Then, when the power switch is turned off, the voltage of the LED module in the path of the current circulated to the diode, for example, the voltage (VLED1) of the first LED module located at the uppermost stage, is applied to the inductor inversely. When the power switch is turned off, current flows only to the LED module in the path of the current circulated to the diode, for example, the first LED module, and the current flows to the other LED module, for example, the second LED module It may not flow.

8 and 9 show current paths when the first power switch is PWM controlled.

Referring to FIG. 8, when the first power switch Q1 is turned on, the current supplied from the AC power source flows through the rectifier 190, the inductor L1, the uppermost first LED module LEDM1, Q1). At this time, a voltage obtained by subtracting the voltage of the first LED module from the rectified voltage is applied to both ends of the inductor L1.

Referring to FIG. 9, when the first power switch Q1 is turned off, the current flowing through the inductor L1 flows through the diode D1 because the current path to the rectifier 190 is cut off.

Figs. 10 and 11 show current paths when the second power switch is PWM-controlled.

Referring to FIG. 10, when the second power switch Q2 is turned on, the current supplied from the AC power source flows through the rectifier 190, the inductor L1, the uppermost first LED module LEDM1, And flows through the adjacent second LED module (LEDM2) and the second power switch (Q2). At this time, a voltage obtained by subtracting the voltages of the first and second LED modules from the rectified voltage is applied to both ends of the inductor L1.

Referring to FIG. 11, when the second power switch Q2 is turned off, the current path to the rectifying unit 190 is cut off, so that the current flowing in the inductor L2 is circulated through the diode D1. When only the first LED module LEDM1 is located in the current circulation path of the diode D1, the first LED module LEDM1 is continuously turned on and the second LED module LEDM2 is turned off as shown in FIG. have. In this case, the second LED module LED M2 may repeatedly be turned on and off repeatedly in the PWM control period.

To solve this problem, it is possible to further arrange the capacitors in parallel with the LED module.

12 is a view showing a structure in which capacitors are connected in parallel to an LED module.

Referring to FIG. 12, the capacitors C1, C2, C3, and C4 are connected in parallel with the respective LED modules LEDM1, LEDM2, LEDM3, and LEDM4.

These capacitors C1, C2, C3 and C4 can temporarily store power required for driving each of the LED modules (LEDM1, LEDM2, LEDM3, LEDM4), thereby preventing on-off repetition in PWM control as described above .

13 shows a current path when the second power switch is turned off in a structure in which a capacitor is further added.

13, when the second power switch Q2 is turned off, the inductor L1 current circulates through the first LED module LEDM1 to the diode D1, but the second LED module LEDM2 Power is stored in the second capacitor C2 connected in parallel so that the second LED module LED M2 can be kept turned on without being turned off.

14 is a diagram illustrating an internal configuration of the control unit.

14, the control unit 110 may include a comparator 110, a latch 1120, a signal generator 1130, a selector 1140, an AND logic circuit 1150, and a buffer 1160. Then, the controller 110 outputs the gate signals Vgs1, Vgs2, Vgs3, and Vgs4 to PWM-control the power switch.

The control unit 110 may compare the sensing current CS with the reference current Iref using the comparator 1110. [ The control unit 110 can input the output value of the comparator 1110 to the reset terminal of the latch 1120. [ The control unit 110 may input the output of the signal generator 1130 to the set terminal of the latch 1120. [

The signal generator 1130 may generate a signal at a predetermined period. According to the signal of the signal generator 1130, the latch 1120 can output a signal having a fixed period.

The signal generator 1130 may sense a zero current and generate a signal. Using the signal of this signal generator 1130, the switching loss is reduced by switching the power switch to zero current.

The output of the latch 1120 may be output as the gate signals Vgs1, Vgs2, Vgs3, and Vgs4 via the AND logic circuit 1150 and the buffer 1160. [

The control unit 110 may input a selection signal to the AND logic circuit 1150 to output only one gate signal. This selection signal may be provided by the selector 1140. [

15 shows a configuration of an LED device according to the second embodiment.

Referring to FIG. 15, the LED device 1200 directly drives the LED module using the AC voltage Vac.

The LED device 1200 includes a rectifier 190, a controller 1210, a diode D1, an inductor L1, a power switch Q, a bypass switch S1, S2, S3, and an LED module LEDM1, LEDM2, LEDM3, LEDM4), and the like.

The LED device 1200 may include N (N is a natural number of 2 or more) LED modules connected in series with each other. For convenience of description, it is assumed that the LED device 1200 includes four LED modules (LEDM1, LEDM2, LEDM3, LEDM4).

The LED device 1200 may include a rectifying part 190 for rectifying the AC voltage Vac. The rectifying unit 190 rectifies an AC voltage Vac supplied from an AC power source, for example, a commercial power grid to generate a rectified voltage Vac.

The LED device 1200 may include N-1 bypass switches. The number of bypass switches may be one less than the number of LED modules. Hereinafter, for convenience of explanation, it is assumed that the LED device 1200 includes three bypass switches S1, S2, and S3.

The LED device 1200 may include a power switch Q.

The LED device 1200 may include a controller 1210 that controls on / off of the power switch Q and the bypass switches S1, S2, and S3.

In addition, the LED device 1200 may include an inductor L1, a diode D1, and a current sensor Rs.

The inductor L1 may be connected in series with the rectifier 190 and the LED modules LEDM1, LEDM2, LEDM3, and LEDM4. The rectified current irec supplied from the rectifying unit 190 can be supplied to the LED modules LEDM1, LEDM2, LEDM3, and LEDM4 via the inductor L1. The rectifier voltage Vrect is connected to one side of the inductor L1 and the voltage of the LED modules LEDM1, LEDM2, LEDM3 and LEDM4 is connected to the other side of the connection so that the inductor voltage (VL) is determined. The shape of the current iL flowing to the inductor L1 is determined by this inductor voltage VL.

The other end of the inductor L1 is electrically connected to the cathode of the diode D1 and the high voltage terminal of the rectifying part 190. The other end of the inductor L1 is electrically connected to the high- And an anode of the diode D1 may be electrically connected to the lowermost LED module-the Nth LED module and the power switch Q. [

The power switch Q can control the electrical connection between the LED module and the rectifying part 190. When the power switch Q is turned on, the LED module and the rectifying unit 190 are electrically connected. When the power switch Q is turned off, the LED module and the rectifying unit 190 are not electrically connected.

The bypass switches S1, S2 and S3 may be connected in parallel with a different number of LED modules. For example, the first bypass switch S1 may be connected in parallel with the three LED modules, the second bypass switch S2 may be connected in parallel with the two LED modules, and the third bypass switch S3 may be connected in parallel with one LED module. Each of the bypass switches S1, S2, and S3 may be commonly connected to one node N3. One node N3 may be connected to the power switch Q and the lowermost LED module.

The control unit 1210 may turn on one of the N-1 bypass switches so that the number of the LED modules LEDM1, LEDM2, LEDM3, and LEDM4 turned on according to the magnitude of the rectified voltage Vrect . For example, the control unit 1210 may turn on the first bypass switch S1 to turn on only the first LED module LEDM1, turn on the second bypass switch S2 to turn on the first LED module LEDM1 and the second LED module LED2 can be turned on.

Meanwhile, the controller 1210 may control the power switch Q linearly or PWM (Pulse Width Modulation).

Light emitting diodes (LEDs) can be adjusted in brightness as needed. In order to adjust the brightness of the LED, the amount of current supplied to the LED must be controlled. The controller 1210 can adjust the amount of current supplied to the LED through linear control or PWM control.

16 shows a configuration of an LED device according to the third embodiment.

Referring to FIG. 16, the LED device 1300 directly drives the LED module using the AC voltage Vac.

The LED device 1300 includes a rectifier 190, a controller 1310, a diode D1, an inductor L1, a power switch Q, a bypass switch S1, S2, S3, and an LED module LEDM1, LEDM2, LEDM3, LEDM4), and the like.

The LED device 1300 may include N (N is a natural number of 2 or more) LED modules connected in series with each other. For convenience of description, it is assumed that the LED device 1300 includes four LED modules (LEDM1, LEDM2, LEDM3, LEDM4).

The LED device 1300 may include a rectifying part 190 for rectifying the AC voltage Vac. The rectifying unit 190 rectifies an AC voltage Vac supplied from an AC power source, for example, a commercial power grid to generate a rectified voltage Vac.

The LED device 1300 may include N-1 bypass switches. The number of bypass switches may be one less than the number of LED modules. Hereinafter, for convenience of explanation, it is assumed that the LED device 1300 includes three bypass switches S1, S2, and S3.

The LED device 1300 may include a power switch Q.

The LED device 1300 may include a control unit 1310 that controls on / off of the power switch Q and the bypass switches S1, S2, and S3.

The LED device 1300 may include an inductor L1, a diode D1, and a current sensor Rs.

The inductor L1 may be connected in series with the rectifier 190 and the LED modules LEDM1, LEDM2, LEDM3, and LEDM4. The rectified current irec supplied from the rectifying unit 190 can be supplied to the LED modules LEDM1, LEDM2, LEDM3, and LEDM4 via the inductor L1. The voltage obtained by subtracting the voltages of the LED modules LEDM1, LEDM2, LEDM3 and LEDM4 which are turned on at both ends of the inductor L1 from the rectified voltage Vrect is supplied in accordance with the connection, and the inductor voltage VL is determined . The shape of the current iL flowing to the inductor L1 is determined by this inductor voltage VL.

The other side of the inductor L1 is electrically connected to the anode of the diode D1 and the power switch Q. The other end of the inductor L1 is electrically connected to the lowermost LED module- The cathode of the diode D1 may be electrically connected to the high voltage terminal of the uppermost LED module - the first LED module (LEDM1) - and the rectifier 190.

The power switch Q can control the electrical connection between the LED module and the rectifying part 190. When the power switch Q is turned on, the LED module and the rectifying unit 190 are electrically connected. When the power switch Q is turned off, the LED module and the rectifying unit 190 are not electrically connected.

The bypass switches S1, S2 and S3 may be connected in parallel with a different number of LED modules. For example, the first bypass switch S1 may be connected in parallel with the three LED modules, the second bypass switch S2 may be connected in parallel with the two LED modules, and the third bypass switch S3 may be connected in parallel with one LED module. Each of the bypass switches S1, S2, and S3 may be commonly connected to one node N4. One node N4 may be connected to the high voltage terminal of the rectifying unit 190. [

The control unit 1310 may turn on one bypass switch among the N-1 bypass switches so that the number of the LED modules LEDM1, LEDM2, LEDM3, and LEDM4 turned on according to the magnitude of the rectified voltage Vrect . For example, the control unit 1310 may turn on the first bypass switch S1 to turn on only the fourth LED module LEDM4, turn on the second bypass switch S2 to turn on the third LED module LEDM3 and the fourth LED module LEDM4 can be turned on.

Meanwhile, the controller 1310 can perform linear control or PWM (Pulse Width Modulation) control of the power switch Q.

Light emitting diodes (LEDs) can be adjusted in brightness as needed. In order to adjust the brightness of the LED, the amount of current supplied to the LED must be controlled. The controller 1310 can adjust the amount of current supplied to the LED through linear control or PWM control.

17 shows a configuration of an LED device according to the fourth embodiment.

Referring to FIG. 17, the LED device 1400 directly drives the LED module using the AC voltage Vac.

The LED device 1200 includes a rectifier 190, a controller 1410, a diode D1, an inductor L1, a power switch Q, a bypass switch S1, S2, S3, and an LED module LEDM1, LEDM2, LEDM3, LEDM4), and the like.

The LED device 1400 may include N (N is a natural number of 2 or more) LED modules connected in series with each other. For convenience of description, it is assumed that four LED modules (LEDM1, LEDM2, LEDM3, LEDM4) are included in the LED device 1400. FIG.

The LED device 1400 may include a rectifier 190 for rectifying the AC voltage Vac. The rectifying unit 190 rectifies an AC voltage Vac supplied from an AC power source, for example, a commercial power grid to generate a rectified voltage Vac.

The LED device 1400 may include N-1 bypass switches. The number of bypass switches may be one less than the number of LED modules. Hereinafter, for convenience of explanation, it is assumed that the LED device 1400 includes three bypass switches S1, S2, and S3.

The LED device 1400 may include a power switch Q.

The LED device 1400 may include a control unit 1410 that controls on / off of the power switch Q and the bypass switches S1, S2, and S3.

The LED device 1400 may include an inductor L1, a diode D1, and a current sensor Rs.

The inductor L1 may be connected in series with the rectifier 190 and the LED modules LEDM1, LEDM2, LEDM3, and LEDM4. The rectified current irec supplied from the rectifying unit 190 can be supplied to the LED modules LEDM1, LEDM2, LEDM3, and LEDM4 via the inductor L1. The rectifier voltage Vrect is connected to one side of the inductor L1 and the voltage of the LED modules LEDM1, LEDM2, LEDM3 and LEDM4 is connected to the other side of the connection so that the inductor voltage (VL) is determined. The shape of the current iL flowing to the inductor L1 is determined by this inductor voltage VL.

The other end of the inductor L1 is electrically connected to the cathode of the diode D1 and the high voltage terminal of the rectifying part 190. The other end of the inductor L1 is electrically connected to the high- And an anode of the diode D1 may be electrically connected to the lowermost LED module-the Nth LED module and the power switch Q. [

The power switch Q can control the electrical connection between the LED module and the rectifying part 190. When the power switch Q is turned on, the LED module and the rectifying unit 190 are electrically connected. When the power switch Q is turned off, the LED module and the rectifying unit 190 are not electrically connected.

The bypass switches S1, S2 and S3 may be connected in parallel with different LED modules. For example, the first bypass switch S1 may be connected in parallel with the second LED module LEDM2, the second bypass switch S2 may be connected in parallel with the third LED module LEDM3, The third bypass switch S3 may be connected in parallel with the fourth LED module LEDM4.

The controller 1410 can control the number of the bypass switches S1, S2, and S3 that are turned on so that the number of the LED modules LEDM1, LEDM2, LEDM3, and LEDM4 turned on according to the magnitude of the rectified voltage Vrect have. For example, the control unit 1410 may turn on all the bypass switches S1, S2, and S3 to turn on only the first LED module LEDM1 and turn on the second bypass switch S2 and the third bypass The switch S3 may be turned on to turn on the first LED module LEDM1 and the second LED module LEDM2.

Meanwhile, the controller 1410 may control the power switch Q linearly or PWM (Pulse Width Modulation).

Light emitting diodes (LEDs) can be adjusted in brightness as needed. In order to adjust the brightness of the LED, the amount of current supplied to the LED must be controlled. The controller 1410 can adjust the amount of current supplied to the LED through linear control or PWM control.

18 shows a configuration of an LED device according to the fifth embodiment.

Referring to FIG. 18, the LED device 1500 directly drives the LED module using the AC voltage Vac.

The LED device 1500 includes a rectifier 190, a controller 1510, a diode D1, an inductor L1, a power switch Q, a bypass switch S1, S2, S3, and an LED module LEDM1, LEDM2, LEDM3, LEDM4), and the like.

The LED device 1500 may include N (N is a natural number of 2 or more) LED modules connected in series with each other. For convenience of explanation, it is assumed that the LED device 1500 includes four LED modules (LEDM1, LEDM2, LEDM3, LEDM4).

The LED device 1500 may include a rectifying part 190 for rectifying the AC voltage Vac. The rectifying unit 190 rectifies an AC voltage Vac supplied from an AC power source, for example, a commercial power grid to generate a rectified voltage Vac.

The LED device 1500 may include N-1 bypass switches. The number of bypass switches may be one less than the number of LED modules. Hereinafter, for convenience of description, it is assumed that the LED device 1500 includes three bypass switches S1, S2, and S3.

The LED device 1500 may include a power switch Q.

The LED device 1500 may include a control unit 1510 for controlling on / off of the power switch Q and the bypass switches S1, S2, and S3.

In addition, the LED device 1500 may include an inductor L1, a diode D1, and a current sensor Rs.

The inductor L1 may be connected in series with the rectifier 190 and the LED modules LEDM1, LEDM2, LEDM3, and LEDM4. The rectified current irec supplied from the rectifying unit 190 can be supplied to the LED modules LEDM1, LEDM2, LEDM3, and LEDM4 via the inductor L1. The voltage obtained by subtracting the voltages of the LED modules LEDM1, LEDM2, LEDM3 and LEDM4 which are turned on at both ends of the inductor L1 from the rectified voltage Vrect is supplied in accordance with the connection, and the inductor voltage VL is determined . The shape of the current iL flowing to the inductor L1 is determined by this inductor voltage VL.

The other side of the inductor L1 is electrically connected to the anode of the diode D1 and the power switch Q. The other end of the inductor L1 is electrically connected to the lowermost LED module- The cathode of the diode D1 may be electrically connected to the high voltage terminal of the uppermost LED module - the first LED module (LEDM1) - and the rectifier 190.

The power switch Q can control the electrical connection between the LED module and the rectifying part 190. When the power switch Q is turned on, the LED module and the rectifying unit 190 are electrically connected. When the power switch Q is turned off, the LED module and the rectifying unit 190 are not electrically connected.

The bypass switches S1, S2 and S3 may be connected in parallel with different LED modules. For example, the first bypass switch S1 may be connected in parallel with the first LED module LEDM1, the second bypass switch S2 may be connected in parallel with the second LED module LEDM2, And the third bypass switch S3 may be connected in parallel with the third LED module LEDM3.

The controller 1510 can control the number of the bypass switches S1, S2 and S3 turned on so that the number of the LED modules LEDM1, LEDM2, LEDM3 and LEDM4 turned on according to the magnitude of the rectified voltage Vrect have. For example, the control unit 1510 may turn on all the bypass switches S1, S2, and S3 to turn on only the fourth LED module LEDM4, and turn on the first bypass switch S1 and the second bypass The switch S2 can be turned on to turn on the third LED module LEDM3 and the fourth LED module LEDM4.

On the other hand, the controller 1510 can control the power switch Q linearly or PWM (Pulse Width Modulation).

Light emitting diodes (LEDs) can be adjusted in brightness as needed. In order to adjust the brightness of the LED, the amount of current supplied to the LED must be controlled. The controller 1410 can adjust the amount of current supplied to the LED through linear control or PWM control.

Several embodiments have been described above. According to this embodiment, the AC voltage can be directly used for driving the LED, thereby reducing the number of components and reducing the cost. In addition, according to this embodiment, it is possible to select the appropriate number of LED modules according to the magnitude of the AC voltage, and adjust the brightness of each LED module through the PWM control.

It is to be understood that the terms "comprises", "comprising", or "having" as used in the foregoing description mean that the constituent element can be implanted unless specifically stated to the contrary, But should be construed as further including other elements. All terms, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, unless otherwise defined. Commonly used terms, such as predefined terms, should be interpreted to be consistent with the contextual meanings of the related art, and are not to be construed as ideal or overly formal, unless expressly defined to the contrary.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

Claims (12)

N LED modules (N is a natural number of 2 or more) connected in series;
A rectifying section for providing a rectified voltage;
N power switches for controlling electrical connection between a common node electrically connected to the rectifying unit and an input node or an output node of each LED module;
An inductor connected in series with the rectifying part and the LED module;
One of the N power switches is selected so that the number of the LED modules turned on according to the magnitude of the rectified voltage is changed, and the one power switch is linearly controlled in a first time period, A controller for controlling PWM (Pulse Width Modulation); And
A diode that provides a circulating path of current to the inductor when the one power switch is turned off;
. The method according to claim 1,
Wherein the one power switch, the inductor and the diode are operated by a buck converter. 3. The method of claim 2,
And the second time interval is subsequent to the first time interval. The method according to claim 1,
Wherein,
And when the one power switch is linearly controlled or PWM controlled, the remaining power switches are turned off. The method according to claim 1,
And the common node is electrically connected to the low voltage terminal of the rectifying unit. The method according to claim 1,
The other end of the inductor is electrically connected to the cathode of the diode and the high voltage terminal of the rectifying part. The anode of the diode is connected to the uppermost And an LED device electrically connected to the other side of the LED module and the first power switch. The method according to claim 1,
And a capacitor connected in parallel with the LED module. The method according to claim 1,
Wherein,
A comparator for generating a reset signal by comparing a sensing current and a reference current, a latch for receiving the set signal at a set terminal and receiving the reset signal at a reset terminal, An AND logic circuit receiving the output of the latch and the selection signal, and a buffer generating an output of the AND logic circuit as a gate signal. The method according to claim 1,
Wherein the control unit performs PWM control of the one power switch with a fixed duty. 9. The method of claim 8,
Wherein the controller controls the duty of the PWM control to adjust the brightness of the LED module. N LED modules (N is a natural number of 2 or more) connected in series;
A rectifying section for providing a rectified voltage;
A power switch for controlling electrical connection between the N LED modules and the rectifying part;
N-1 bypass switches connected in parallel with different numbers of the LED modules;
An inductor connected in series with the rectifying part and the LED module;
One of the N-1 bypass switches is turned on so that the number of the LED modules turned on according to the magnitude of the rectified voltage is changed, the power switch is linearly controlled in the first time interval, A PWM (Pulse Width Modulation) control unit; And
A diode that provides a circulating path of current to the inductor when the power switch is turned off;
. 12. The method of claim 11,
The other end of the inductor is electrically connected to the cathode of the diode and the high voltage terminal of the rectifying part. The anode of the diode is connected to the lowermost LED module and the high- And electrically connected to the power switch.

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