KR102449566B1 - Led driving circuit with improved flicker performance and led luminescent apparutus the same - Google Patents

Abstract

The present invention provides a flicker, which can reduce the light output deviation of the LED lighting device that occurs during the operation section by eliminating the non-emission section of the LED lighting device by using a loopback compensator in the LED lighting device of the AC sequential driving method. Disclosed is an LED lighting device with improved performance.

Description

LED driving circuit with improved flicker performance and LED lighting device including the same

The present invention relates to an LED driving circuit having improved flicker performance and an LED lighting device including the same. More specifically, in the LED lighting device of the AC sequential driving method, the LED driving circuit with improved flicker performance, which can reduce the light output deviation of the LED lighting device that occurs during the operation section by removing the LED off section, and the same It relates to an LED lighting device comprising.

A direct current driving method is common for LED driving. In the case of a DC drive method, an AC-DC converter such as an SMPS is essential, and such a power converter increases the manufacturing cost of the lighting equipment, makes it difficult to miniaturize the lighting equipment, reduces the energy efficiency of the lighting equipment, and has a short lifespan. Accordingly, there is a problem in that the life of the lighting equipment is shortened.

In order to solve the problem of such a DC driving method, an AC driving method of an LED has been proposed. However, in the case of a circuit according to this technology, there is a problem in that the power factor is lowered due to the mismatch between the input voltage and the current output from the LED, and when the non-emission period of the LED is long, the user perceives the flicker of the light. There is a problem that the phenomenon occurs.

1 is a conceptual diagram for explaining a flicker performance. The definition and regulation of flicker, which is the standard of the flicker performance of the recent Energy Star specification (SPEC), are as follows.

(1) Definition of Flicker

Flicker refers to a phenomenon in which the brightness of the light changes for a certain period of time, and in severe cases, the user may perceive the light flickering or flickering. Most of the flicker is a phenomenon that occurs because the maximum light output and the minimum light output are different for a certain period of time.

(2) Types of indicators indicating flicker performance

a) Flicker Index: As shown in FIG. 1 , the flicker index is obtained by dividing the area (Area1) above the average light output by the total light output area (Area1+Area2) on the optical output waveform diagram of one period. means value. Accordingly, the flicker index is a value numerically indicating how much light greater than the average light output is generated during one period, and the lower the flicker index, the better the flicker level.

b) Percent Flicker or Modulation Depth: Percent flicker refers to an index that quantifies the minimum and maximum amount of light for a certain period of time. This percent flicker may be calculated as 100*(maximum light quantity - minimum light quantity)/(maximum light quantity + minimum light quantity).

(3) Energy Star Flicker Index Regulations

- Light output waveform ≥ 120Hz

- Flicker index ≤ frequency x 0.001 (except at Max. Dimmer, over 800 Hz) (thus, flicker index ≤ 0.12 at 120 Hz)

(4) Study results on percent flicker

According to research papers on percent flicker,

Percent flicker < 0.033 x 2 x frequency or less is an unaffected section,

Percent flicker < 0.033 x 2 x frequency or less was declared as a low risk section.

As described above, the level of flicker is emerging as an important criterion in the performance of the LED lighting device.

Meanwhile, FIG. 2 is a schematic block diagram of a 4-stage sequentially driven LED lighting device according to the prior art, and FIG. 3 is a driving voltage versus LED driving current of the 4-stage sequentially driven LED lighting device according to the prior art disclosed in FIG. It is a waveform diagram showing the relationship. Hereinafter, with reference to FIGS. 2 and 3, the problems of the LED lighting device according to the prior art will be looked at.

First, as shown in FIG. 2 , the LED lighting device 100 according to the prior art may include a rectifying unit 10 , an LED light emitting unit 20 , and an LED driving control unit 30 .

The rectifying unit 10 of the LED lighting device 100 according to the prior art rectifies an AC voltage ( _VAC ) input from an external power source to generate a rectified voltage (Vrec), and converts the generated rectified voltage (Vrec) to the LED light emitting unit (20) and configured to output to the LED driving control unit (30). As the rectifying unit 10, one of various well-known rectifying circuits such as a full-wave rectifier circuit and a half-wave rectifier circuit may be used. has been In addition, the LED light emitting unit 20 according to the prior art is composed of four LED groups from the first LED group 21 to the fourth LED group 24 , and sequentially according to the control of the LED driving control unit 30 . It is configured to turn on and turn off sequentially. On the other hand, the LED driving control unit 30 according to the prior art is configured to perform a control function of sequentially turning on and off the first LED group 21 to the fourth LED group 24 according to the voltage level of the rectified voltage Vrec. do.

In particular, the LED driving control unit 30 according to the prior art is configured to increase or decrease the LED driving current according to the voltage level of the input voltage (ie, the rectified voltage Vrec) to perform a constant current control function for each sequential driving section, which is the LED This is to improve the power quality of LED lighting devices by improving the power factor (PF) and total harmonics distortion (THD) by making the driving current take the shape of a step wave close to a sine wave.

The operation process of the LED lighting device 100 according to the prior art will be described in more detail with reference to FIG. 3 . As shown in Figure 3, the LED driving control unit 30 according to the prior art, in order to control the sequential driving of the LED groups, the first constant current switch (SW1), the second constant current switch (SW2), the third constant current switch (SW3), and a fourth constant current switch (SW4) may be included. Specifically, the LED driving control unit 30 according to the prior art has a rectified voltage (Vrec) equal to or higher than the first forward voltage level (Vf1) and less than the second forward voltage level (Vf2). Only the LED group 21 is turned on and the LED driving current (I _LED ) is controlled by a constant current to become the first LED driving current (I _LED1 ). Similarly, the LED driving control unit 30 according to the prior art has the rectified voltage Vrec higher than the second forward voltage level Vf2 and less than the third forward voltage level Vf3. By turning off the first constant current switch SW1 and turning on the second constant current switch SW2, only the first LED group 21 and the second LED group 22 are turned on and the LED driving current (I _LED ) is turned on. ) to the second LED driving current (I _LED2 ) is a constant current control. In addition, the LED driving control unit 30 according to the prior art has a rectified voltage (Vrec) equal to or higher than the third forward voltage level (Vf3) and less than the fourth forward voltage level (Vf4). By turning off the constant current switch SW2 and turning on the third constant current switch SW3, the first LED group 21 to the third LED group 23 are turned on and the LED driving current (I _LED ) A constant current is controlled by the third LED driving current (I _LED3 ). Finally, the LED driving control unit 30 according to the prior art turns off the third constant current switch SW3 in a section in which the rectified voltage Vrec is equal to or greater than the fourth forward voltage level Vf4 (fourth stage operation section) And by turning on the fourth constant current switch (SW4), the first LED group 21 to the fourth LED group 24 are all turned on and the LED driving current (I _LED ) is the fourth LED driving current (I) _LED4 ) to control constant current. 3, the LED driving current (ie, the second LED driving current) in the second stage operation period than the LED driving current in the first stage operation period (ie, the first LED driving current (I _LED1 )) (I _LED2 )) is controlled to be larger, likewise the second LED driving current (I _LED2 ) is controlled to be larger than the third LED driving current (I _LED3 ), and the fourth LED driving current (I _LED4 ) is the most controlled to be large. Accordingly, the total light output of the LED lighting device 100 according to the prior art has a stepped wave shape as shown in FIG. 3 . Therefore, in the case of using the LED lighting device 100 according to the prior art, the light output is different for each operation section because the total number of LEDs emitted and the driving current are different depending on the operation section, and thus the user can use the light output for each operation section. Inconvenience may be felt due to the difference in That is, in the case of the LED lighting device of the sequential driving method according to the prior art as described above, improvement is required because the percent flicker reaches 100%.

In addition, in the case of the LED lighting device 100 according to the prior art as described above, it is configured to sequentially control the driving based on the driving voltage provided to the LED light emitting unit 20, that is, the voltage level of the rectified voltage Vrec. have. However, in the case of such a voltage detection method, there is a problem in that the current/voltage characteristics according to the LED temperature are not properly reflected. That is, although the forward voltage of the LED group differs depending on the “operating temperature of the LED,” the voltage detection method does not properly reflect the I/V characteristics according to the temperature of the LED. For example, a phenomenon in which the LED driving current (LED light output) momentarily drops or overshoots occurs at the time point when the first stage operation period is changed to the second stage operation period) There is a problem that the output is not constant.

The present invention is to solve the problems of the prior art as described above.

The present invention provides an LED driving circuit with improved flicker performance, which can provide natural light to a user by reducing a deviation in light output by removing a non-emission section in an AC sequential driving type LED lighting device, and an LED including the same One object is to provide a lighting device.

In addition, in the LED lighting device of the AC sequential driving method, the light output of the LED lighting device generated between the operation sections by controlling the size of the LED driving current supplied to the LEDs based on the number of LEDs lit for each operation section Another object of the present invention is to provide an LED driving circuit with improved flicker performance, which can reduce deviation, and an LED lighting device including the same.

In addition, the present invention is to provide an LED driving circuit with improved flicker performance, which can provide a constant light output by controlling sequential driving between LED groups based on an LED driving current detection method, and an LED lighting device including the same for another purpose.

In order to achieve the object of the present invention as described above and to achieve the specific effects of the present invention to be described later, the characteristic configuration of the present invention is as follows.

According to an aspect of the present invention, there is provided a rectifying unit for full-wave rectification of an AC voltage connected to an AC power source and providing the full-wave rectified rectified voltage as a first driving voltage to the LED light emitting unit;

The first LED group to the nth LED group (n is a positive integer greater than or equal to 2) is configured to include, and is supplied with the rectified voltage from the rectifier as the first driving voltage in the non-compensation section to emit light, and loopback in the compensation section an LED light emitting unit receiving a second driving voltage from the compensating unit and emitting light;

It is located between the n-1 th LED group and the node between the n th LED group and the LED driving control unit, and charges energy using the rectified voltage in the charging period, and the second in the LED light emitting unit in the compensation period. A loop-back compensator providing a driving voltage; And

LEDs for detecting LED driving current flowing through constant current switches respectively connected to the first LED group to the nth LED group, and controlling sequential driving of the first LED group to the nth LED group according to the detected LED driving current comprising a drive control unit;

The LED driving control unit detects the charging current flowing through the constant current switch connected to the loopback compensator to determine whether to enter or leave the charging period, and turns off the constant current switch connected to the nth LED group at the time of entering the charging period. , Turning on the constant current switch connected to the n-th LED group at the time of departure from the charging section, the LED lighting device is provided.

More preferably, the LED driving control unit turns on the constant current switch connected to the loopback compensator at the time of entering the nth operation period from the n-1 th operation period according to the rise of the rectified voltage, and the charging current flowing through it , and when the detected charging current rises above a preset value, the n-th LED group turns off and enters a charging section, and after entering the charging section, the detected charging current falls below a preset value In this case, the n-th LED group may be turned on again to enter the n-th operation period again.

More preferably, the LED driving control unit is: each connected to the anode terminal of each of the first LED group to the nth LED group to connect or separate the first current path to the nth current path according to the operation section, each a first constant current switch to an n-th constant current switch for constant current control of the LED driving current in the operation period; and the loopback compensator and the LED driving control unit to connect or disconnect the n+1th current path between the loopback compensator and the LED driving control unit, and generate the n+1th LED driving current in the charging section. An n+1th constant current switch for constant current control may be included.

More preferably, the n+1th LED driving current value may be set equal to the n−1th driving current value.

More preferably, the LED driving control unit sets a value of the LED driving current (first LED driving current to nth LED driving current) for each operation section based on the total number of LEDs emitted for each operation section, and sets a value for each set operation section A constant current control of the LED driving current in the corresponding operation section according to the LED driving current value may be set in such a way that the first to nth LED driving currents are sequentially decreased.

More preferably, the LED driving control unit sets the LED driving current (first LED driving current to nth LED driving current) value for each operation section so as to be inversely proportional to the total number of LEDs emitted for each operation section, and sets a value for each set operation section According to the LED driving current value, it may be configured to control the LED driving current in the corresponding operation section with constant current.

More preferably, the LED light emitting unit includes a first LED group and a second LED group, and the light output of the first LED group during a first operation period and the first LED group and the second LED group during a second operation period The difference between the light outputs of the two LED groups may be configured to be less than or equal to a preset light output deviation.

More preferably, the LED light emitting unit may include a first LED group and a second LED group, and the second driving voltage may be configured to be equal to or higher than a forward voltage level of the first LED group.

More preferably, the LED light emitting unit may include a first LED group and a second LED group, and a forward voltage level of the first LED group may be greater than a forward voltage level of the second LED group.

More preferably, the LED lighting device is located between the n-1 th LED group and the node between the n th LED group and the loopback compensator to be turned on or off according to the control of the LED driving controller. and an n+2 th switch that becomes an n + 2 th switch, wherein the LED driving control unit turns on the n + 2 th switch at the time of entering the n th operation period, and turns on the n + 2 th switch at the time of entering the compensation period - can be configured to off.

More preferably, the LED lighting device is connected in parallel to the n-th LED group, and is charged during the n-th operation period and a driving voltage is applied to the n-th LED group during a non-emission period in which the n-th LED group does not emit light. It may further include a second compensation unit for supplying.

More preferably, the LED driving control unit drives the first LED driving current setting unit to the n+1th LED driving current that can set the corresponding LED driving current value among the first LED driving current value to the n+1th LED driving current value, respectively. It may further include a current setting unit.

More preferably, each of the first LED driving current setting unit to the n+1th LED driving current setting unit may be configured as a variable resistor.

According to another aspect of the present invention, there is provided a rectifying unit for full-wave rectification of an AC voltage applied by being connected to an AC power source and providing the full-wave rectified rectified voltage as a first driving voltage to the LED light emitting unit; Consists of a first LED group and a second LED group, receives the rectified voltage from the rectifier as the first driving voltage in the non-compensation section to emit light, and supplies a second drive voltage from the loopback compensator in the compensation section an LED light emitting unit that receives and emits light; It is located between a node between the first LED group and the second LED group and an LED driving control unit, and charges energy using the rectified voltage in a charging period (first operation period), and in the compensation period, the first A loopback compensator for providing the second driving voltage to the LED group and the second LED group; and detecting the LED driving current flowing through the constant current switches respectively connected to the first LED group and the second LED group, and an LED driving control unit for controlling the transformation sequential driving of the first LED group and the second LED group according to the LED driving current, wherein the LED driving control unit detects a charging current flowing through a constant current switch connected to the loopback compensator to determine whether to enter or leave the charging section, turn off the constant current switch connected to the second LED group at the time of entering the charging section, and turn on the constant current switch connected to the second LED group at the time of leaving the charging section A configured LED lighting device is provided.

According to another aspect of the present invention, an LED driving circuit comprising a first LED group and a second LED group, and controlling the driving of an LED light emitting unit receiving a full-wave rectified rectified voltage from the rectifying unit as a first driving voltage, the LED driving circuit comprising: It is located between a node between the first LED group and the second LED group and an LED driving control unit, and charges energy using the rectified voltage in a charging period (first operation period), and in a compensation period, the first LED A loopback compensator for providing a second driving voltage to the group and the second LED group; and detecting the LED driving current flowing through the constant current switches respectively connected to the first LED group and the second LED group, and driving the detected LED and an LED driving control unit for controlling the transformation sequential driving of the first LED group and the second LED group according to the current, wherein the LED driving control unit detects a charging current flowing through a constant current switch connected to the loopback compensator to charge LED configured to determine whether to enter or leave the section, turn off the constant current switch connected to the second LED group at the time of entering the charging section, and turn on the constant current switch connected to the second LED group at the time of leaving the charging section A lighting device is provided.

According to a preferred embodiment of the present invention, by removing the non-emission section using a loop back compensator, it is possible to reduce the variation in light output and provide natural light to the user.

In addition, according to the present invention, in the LED lighting device of the AC sequential driving method, by controlling the size of the LED driving current supplied to the LEDs based on the number of LEDs lit for each operation period, the LED generated during the operation period An effect of reducing the light output deviation of the lighting device can be expected.

In addition, according to the present invention, the present invention is LED lighting according to the prior art for controlling sequential driving between LED groups based on the LED driving voltage detection method by controlling the sequential driving between the LED groups based on the LED driving current detection method An effect of providing a more improved constant light output than the device can be expected.

1 is a conceptual diagram for explaining a flicker performance.
Figure 2 is a schematic configuration block diagram of a 4-stage sequentially driven LED lighting device according to the prior art.
3 is a waveform diagram showing the relationship between the driving voltage and the LED driving current of the LED lighting device according to the prior art shown in FIG.
4 is a schematic block diagram of the LED lighting device according to the first embodiment of the present invention.
5A to 5D are block diagrams illustrating a switch control state and an LED driving current for each operation section of the LED lighting device according to the first embodiment of the present invention shown in FIG. 4;
FIG. 6 is a waveform diagram illustrating a relationship between a rectified voltage, an LED driving current, an input current, and a light output of an LED light emitting unit according to time of the LED lighting device according to the first embodiment of the present invention shown in FIG. 4 .
7 is a schematic structural block diagram of an LED lighting device according to a second embodiment of the present invention.
8A to 8D are block diagrams illustrating a switch control state and an LED driving current for each operation section of the LED lighting device according to the second embodiment of the present invention shown in FIG. 7;
9 is a schematic structural block diagram of an LED lighting device according to a third embodiment of the present invention.
10 is a schematic structural block diagram of an LED lighting device according to a fourth embodiment of the present invention.
11 is a schematic structural block diagram of an LED lighting device according to a fifth embodiment of the present invention.
12A to 12C are block diagrams illustrating a switch control state and an LED driving current for each operation section of the LED lighting device according to the fifth embodiment of the present invention shown in FIG. 11;
13 is a waveform diagram illustrating the relationship between rectified voltage, LED driving current, input current, and light output of an LED light emitting unit according to time of the LED lighting device according to the fifth embodiment of the present invention shown in FIG. 11 .

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0016] Reference is made to the accompanying drawings, which show by way of illustration specific embodiments in which the present invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the present invention. It should be understood that the various embodiments of the present invention are different but need not be mutually exclusive. For example, certain shapes, structures, and characteristics described herein with respect to one embodiment may be implemented in other embodiments without departing from the spirit and scope of the invention. In addition, it should be understood that the location or arrangement of individual components within each disclosed embodiment may be changed without departing from the spirit and scope of the present invention. Accordingly, the detailed description set forth below is not intended to be taken in a limiting sense, and the scope of the present invention, if properly described, is limited only by the appended claims, along with all scopes equivalent to those claimed by the claims. Like reference numerals in the drawings refer to the same or similar functions throughout the various aspects.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art can easily practice the present invention.

[Preferred embodiment of the present invention]

In an embodiment of the present invention, the term 'LED group' refers to a plurality of LEDs (or a plurality of light emitting cells) connected in series/parallel/serial-parallel, and the operation is controlled as a unit according to the control of the LED driving module. It means a set of LEDs that are turned on (that is, turned on/off together).

In addition, the term 'first forward voltage level (Vf1)' means a threshold voltage level capable of driving the first LED group, and the term 'second forward voltage level (Vf2)' is a first LED group connected in series and It means a threshold voltage level capable of driving the second LED group (that is, a voltage level obtained by adding the forward voltage level of the first LED group and the forward voltage level of the second LED group), and the term 'third forward voltage level (Vf3) )' means a threshold voltage level capable of driving the first to third LED groups connected in series. That is, the 'n-th forward voltage level (Vfn)' is a threshold voltage level capable of driving the first to n-th LED groups connected in series (ie, the forward voltage level of the first LED group to the forward voltage of the n-th LED group). voltage level that is the sum of all levels).

In addition, the term 'sequential driving method based on driving voltage detection' or 'multi-stage driving method based on driving voltage detection' refers to an LED driving module that drives an LED by receiving an input voltage that changes in size with time. It refers to a driving method in which a plurality of LED groups are sequentially emitted according to an increase in an input voltage, and a plurality of LED groups are sequentially turned off according to a decrease in an applied input voltage. In addition, the term 'sequential driving method based on driving current detection' or 'multi-stage driving method based on driving current detection' refers to an LED driving module that drives an LED by receiving an input voltage that changes in size over time, It refers to a driving method in which a plurality of LED groups constituting the LED light emitting unit are sequentially turned on and off according to the increase or decrease of the LED driving current flowing through the negative or constant current switch connected to the LED light emitting unit. Meanwhile, regardless of whether the driving voltage detection method or the driving current detection method is used, in the sequential driving method or the multi-stage driving method, the first stage operation period means an operation period in which only the first LED group emits light, and the second stage operation The period means an operation period in which only the first LED group and the second LED group emit light, and similarly, the nth stage operation period means an operation period in which all of the first LED group to the nth LED group emit light. .

In addition, the term 'first driving voltage' refers to a driving voltage that is primarily supplied to the LED groups after the input voltage itself or the input voltage is constantly processed (eg, processed through a process such as a rectifier circuit). In addition, the term 'second driving voltage' refers to a driving voltage that is secondarily supplied to the LED groups from the energy storage device after the input voltage is stored in the energy storage device. The second driving voltage may be, for example, a driving voltage supplied to the LED groups from the charged capacitor after the input voltage is stored in the capacitor. Accordingly, except when specifically referred to as a 'first driving voltage' or a 'second driving voltage', the term 'driving voltage' includes the first driving voltage and/or the second driving voltage supplied to the LED groups. it means

In addition, the term 'compensation section' refers to a section in which the voltage level of the input voltage (rectified voltage) is less than a preset forward voltage level in the sequential driving method, and means a section in which the driving current cannot be supplied to the LED group. For example, the first forward voltage level (Vf1) compensation section means a section in which the voltage level of the rectified voltage is less than Vf1. In this case, the compensation section is a non-emission section. In addition, the second forward voltage level (Vf2) compensation section means a section in which the voltage level of the rectified voltage is less than Vf2. Therefore, the nth forward voltage level (Vfn) compensation section means a section in which the voltage level of the rectified voltage is less than Vfn. In addition, the term first forward voltage level (Vf1) compensation means supplying a driving current to the LED group by supplying a second driving voltage to the LED group in the first forward voltage level (Vf1) compensation section, and the term second forward The voltage level (Vf2) compensation means that the second driving voltage is supplied to the LED group in the second forward voltage level (Vf2) compensation period. Accordingly, the nth forward voltage level (Vfn) compensation means that the second driving voltage is supplied to the LED group in the nth forward voltage level (Vfn) compensation period.

In addition, the term 'non-compensation period' (or 'normal operation period') is a period in which the voltage level of the input voltage (rectified voltage) is higher than or equal to a preset forward voltage level in the sequential driving method, and the input voltage (first driving period) voltage) is supplied to the LED group and means a period in which the LED group(s) emit light. Illustratively, in the embodiment in which the first forward voltage level Vf1 compensation is performed, the 'non-compensation period' (or 'normal operation period') means a period in which the voltage level of the input voltage is Vf1 or higher, and the second forward In the embodiment in which the voltage level Vf2 is compensated, the 'non-compensation period' (or 'normal operation period') means a period in which the voltage level of the input voltage is Vf2 or higher. Accordingly, in the embodiment in which the nth forward voltage level Vfn compensation is performed, the 'non-compensation period' (or 'normal operation period') means a period in which the voltage level of the input voltage is Vfn or more.

Also, terms such as V1, V2, V3, ..., t1, t2, ..., T1, T2, T3, etc. used herein to indicate any specific voltage, specific time point, specific temperature, etc. is not used to indicate an absolute value, but is a relative value used to distinguish each other.

Configuration and function of the first embodiment of the LED lighting device 1000

4 is a schematic structural block diagram of an LED lighting device with improved flicker performance (hereinafter referred to as 'LED lighting device') according to the first embodiment of the present invention. Hereinafter, the configuration and function of the LED lighting device 1000 according to the present invention will be briefly described with reference to FIG. 4 .

First, let's look at the overall technical idea constituting the LED lighting device 1000 according to the present invention. As described above, in the case of a sequentially driven AC LED lighting device according to the prior art, since the LED groups are sequentially turned on and off according to the voltage level of the driving voltage supplied to the LED light emitting unit 20, the driving In a section in which the voltage level of the voltage is less than the first forward voltage level (Vf1), a non-emission section occurs in which no LED group among the LED groups emits light. In addition, in the case of a sequentially driven AC LED lighting device according to the prior art, as the voltage level of the driving voltage supplied to the LED light emitting unit 20 increases, the number of LEDs to be lit increases, and the LED light emitting unit 400 is supplied As the voltage level of the driving voltage decreases, the number of lit LEDs decreases. Due to these characteristics of the sequentially driven AC LED lighting device, there is a problem in that the flicker performance is particularly poor.

Therefore, the most basic technical idea of the present invention is, by removing the section in which the LED light emitting unit 400 of the LED lighting device 1000 does not emit light during the operation of the LED lighting device 1000, that is, the non-emission section, the LED lighting To improve the flicker performance of the device 1000 . In order to perform this function, the present invention proposes a loop-back compensation unit, and supplies a second driving voltage to the LED light-emitting unit 400 in the non-light-emitting section through the loop-back compensation unit 300 . configured to remove the light emitting section.

In addition, in relation to the flicker performance as described above, the reason that the flicker performance is poor in the alternating current LED lighting device of the sequential driving method is that the LED driving current is controlled in proportion to the number of LEDs lit for each operation section. Therefore, in order to solve this problem, the present invention proposes an LED lighting device configured to control the LED driving current for each operation section in inverse proportion to the number of LEDs lit for each operation section. Therefore, by adopting this LED driving current control method according to the present invention, when the number of LEDs lit according to the operation period is relatively small, the LED driving current in the operation period is controlled relatively larger, and the number of lit LEDs is relatively small. In more cases, by controlling the LED driving current in the corresponding operation period to be relatively smaller, an almost uniform light output can be provided for each operation period. The LED driving current control method according to the present invention will be described later with reference to FIGS. 5A to 5D and FIG. 6 .

Meanwhile, as shown in FIG. 4 , the LED lighting device 1000 according to the present invention may include a rectifying unit 200 , a loopback compensation unit 300 , an LED light emitting unit 400 , and an LED driving control unit 500 . have. In addition, among the above-described components, the loopback compensation unit 300 and the LED driving control unit 500 may constitute the LED driving circuit.

First, the LED light-emitting unit 400 may be composed of a plurality of LED groups, and the plurality of LED groups included in the LED light-emitting unit 400 are sequentially emitted according to the control of the LED driving control unit 500 , and sequentially turned off to Although the LED light-emitting unit 400 including the first LED group 410 and the second LED group 420 is disclosed in FIG. 4 , the number of LED groups included in the LED light-emitting unit 400 varies according to need. It will be apparent to those skilled in the art that it can be changed. However, hereinafter, for the convenience of explanation and understanding, the LED light emitting unit 400 will be described based on an embodiment in which two LED groups are configured, but the present invention is not limited thereto. For example, the LED light emitting unit 400 may be composed of four LED groups from the first LED group 410 to the fourth LED group (not shown), or the first LED group 410 to It may be composed of n LED groups up to the nth LED group (not shown), but as long as the technical gist of the present invention is included, it will be apparent to those skilled in the art that it falls within the scope of the present invention.

Meanwhile, according to the configuration of the embodiment, the first LED group 410 and the second LED group 420 may have different forward voltage levels, respectively. For example, when the first LED group 410 and the second LED group 420 are each configured to include a different number of LED elements, or the first LED group 410 and the second LED group 420 are different In the case of having a series, parallel, or series-parallel connection relationship, the first LED group 410 and the second LED group 420 will have different forward voltage levels. However, in a preferred embodiment of the present invention, the first LED group 410 is designed to have a forward voltage level that can be driven by the second driving voltage supplied by the loopback compensator 300 in the compensation section. should be When designed in this way, the first LED group 410 always maintains the turned-on state in the entire cycle of the _AC voltage (VAC).

In addition, in order to improve the flicker performance as described above, the number of LEDs constituting the first LED group 410 that always maintains the turn-on state in the entire period of the AC voltage V _AC emits light only in the second operation period. The second LED group 420 is preferably designed to be larger than the number of LEDs constituting it. Accordingly, in this case, it may be desirable to design the forward voltage level of the first LED group 410 to be significantly higher than the forward voltage level of the second LED group 420 .

The rectifying unit 200 according to the present invention as shown in FIG. 4 is configured to generate and output a rectified voltage Vrec by rectifying an AC voltage V _AC input from an external power source. As the rectifier 200 , one of various well-known rectification circuits such as a full-wave rectifier circuit and a half-wave rectifier circuit may be used. The rectifying unit 200 is configured to provide the generated rectified voltage Vrec to the loopback compensator 300 , the LED light emitting unit 400 , and the LED driving control unit 500 . FIG. 4 shows a bridge full-wave rectifier circuit composed of four diodes D1, D2, D3, and D4.

On the other hand, the loopback compensator 300 according to the present invention is configured to charge energy using the rectified voltage Vrec in the charging section, and to provide a second driving voltage to the LED light emitting unit 400 in the compensation section. In FIG. 4 , the first capacitor C1 is illustrated as the loopback compensator 300 according to the present invention. However, the present invention is not limited thereto, and one of various well-known compensation circuits (eg, a valley-fill circuit, etc.) may be adopted and used as necessary.

5, one end of the loopback compensator 300 is connected to the LED driving control unit 500 through the third constant current switch SW3, and the other end of the loopback compensator 300 is connected to the first LED It is connected to the anode end of the group 410 . Of course, depending on the configuration of the embodiment, the other end of the loopback compensator 300 may be connected to the anode end of another LED group. For example, in the embodiment in which the LED light emitting unit 400 is configured with four LED groups, the other end of the loopback compensator 300 may be configured to be connected to the anode end of the second LED group. In this case, the loopback compensator 300 is configured to supply the second driving voltage to the second LED group (or the second LED group to the third LED group, etc.) in the compensation section. Hereinafter, the other end of the loopback compensator 300 is connected to the anode end of the first LED group 410 to supply the second driving voltage to the first LED group 410 in the compensation section. to proceed with

In addition, in the embodiment shown in FIG. 4 , the loopback compensator 300 according to the present invention has a second operation period (that is, a period in which the voltage level of the rectified voltage Vrec is equal to or greater than the second forward voltage level Vf2). is charged in the non-emission section (that is, the section in which the voltage level of the rectified voltage Vrec is less than the first forward voltage level Vf1) is discharged to provide a second driving voltage to the first LED group 410. have. However, the present invention is not limited to this embodiment, when the LED lighting device 1000 according to the present invention includes four LED groups from the first LED group 410 to the fourth LED group (not shown). , the loopback compensator 300 may be charged in the fourth operation period (ie, the period in which the voltage level of the rectified voltage Vrec is equal to or greater than the fourth forward voltage level Vf4). Also, similarly, when the LED lighting device 1000 according to the present invention includes n LED groups from the first LED group 410 to the nth LED group (not shown), the loopback compensator 300 is It should be noted that the battery may be charged in the n-th operation period (ie, the period in which the voltage level of the rectified voltage Vrec is greater than or equal to the n-th forward voltage level Vfn).

In addition, the forward voltage level compensated by the loopback compensator 300 according to the present invention is the energy charge/discharge element constituting the loopback compensator 300 (eg, the first capacitor C1 in FIG. 4 ). It can be designed in various ways depending on the capacity. In one embodiment, the loopback compensator 300 according to the present invention may be configured to compensate a voltage level of 1/2 of the total forward voltage level (a voltage level summing all forward voltage levels of LED groups). Therefore, in the embodiment in which the forward voltage level of the first LED group 410 is designed to be less than or equal to the forward voltage level of the second LED group 420 , the loopback compensator 300 according to the present invention is configured to operate in the first forward direction in the compensation section. It may be configured to supply a voltage of the voltage level Vf1. In this case, as described above, the first LED group 410 always maintains the turn-on state regardless of the cycle of the AC power.

On the other hand, while the LED driving control unit 500 according to the prior art shown in FIG. 2 is configured to control sequential driving between a plurality of LED groups using a driving voltage detection method, the LED driving control unit 500 according to the present invention is The LED driving current (I _LED ) flowing through the LED light emitting unit 400 or the LED driving current (I _LED ) flowing through the constant current switch(s) (SW1 to SW3) connected to the LED light emitting unit 400 is detected and detected It may be configured to control sequential driving of the first LED group 410 and the second LED group 420 based on the LED driving current (I _LED ). However, it should be noted that the present invention can be similarly applied to an LED lighting device configured to control sequential driving between a plurality of LED groups using a driving voltage detection method.

More specifically, in the LED lighting device 1000 according to the present invention, the LED driving control unit 500 according to the present invention is a first constant current switch SW1 for sequential driving control through the driving current detection method as described above. , a second constant current switch SW2 and a third constant current switch SW3 may be included. 4 shows an embodiment in which the first constant current switch SW1 to the third constant current switch SW3 are implemented as separate switches outside the LED driving control unit 500, but the first constant current switch SW1 to the third constant current switch SW1 It will be apparent to those skilled in the art that the switch SW3 may be included in the LED driving control unit 500 .

In addition, each of the first constant current switches SW1 to the third constant current switches SW3 according to the present invention is turned on according to the control of the LED driving controller 500 to connect the current path or turned off to connect the current path It is configured to perform a function of controlling the constant current to a preset value by detecting the LED driving current (I _LED ) flowing through the connected current path and controlling the LED driving current (I _LED ) to a preset value. More specifically, as shown in FIG. 4 , the first constant current switch SW1 is located between the node between the first LED group 410 and the second LED group 420 and the LED driving control unit 500 . The function of connecting or disconnecting the first current path P1 is performed according to the control of the LED driving controller 500 . Similarly, the second constant current switch SW2 is located between the second LED group 420 and the LED driving control unit 500 to connect the second current path P2 under the control of the LED driving control unit 500 or It performs the function of separating. In addition, the third constant current switch SW3 is located between the loopback compensation unit 300 and the LED driving control unit 500 to connect or separate the third current path P3 according to the control of the LED driving control unit 500 . will perform the function. In the present invention, the first constant current switch SW1 to the third constant current switch SW3 of the present invention as described above may be implemented using various known techniques. For example, in relation to the constant current control function as described above, each of the first constant current switches SW1 to the third constant current switches SW3 according to the present invention includes a sensing resistor for detecting a current, a reference current value and a current detected value. A differential amplifier for comparing current values and a switching element configured to control the connection of the path according to the output of the differential amplifier, and to control the LED driving current value flowing through the path as a constant current when the path is connected. In addition, for example, the switching elements constituting the first constant current switch SW1 to the third constant current switch SW3 of the present invention are a metal oxide semiconductor field effect transistor (MOSFET), an insulated gate bipolar transistor (IGBT), a junction type. It may be implemented using one of a transistor (BJT), a junction-type field effect transistor (JFET), a thyristor (Silicon controlled rectifier), and a triac.

The LED driving control unit 500 of the present invention as shown in FIG. 4 detects the LED driving current (I _LED ), and according to the detected LED driving current (I _LED ), the first constant current switch (SW1) as described above to the third constant current switch SW3 is configured to control sequential driving of the first LED group 410 and the second LED group 420 . Detailed functions of the LED driving control unit 500 will be described in detail below with reference to FIGS. 5 to 6 .

5A to 5D are block diagrams illustrating a switch control state and an LED driving current for each operation section of the LED lighting device according to the first embodiment of the present invention shown in FIG. 4 . Hereinafter, with reference to FIGS. 5A to 5D , as shown in FIG. 4 , an operation process of the LED lighting device 1000 according to the first embodiment of the present invention will be described in detail.

First, FIG. 5A shows the relationship between the control state of the first constant current switch SW1 to the third constant current switch SW3 and the LED driving current I _LED in the first operation section. As shown in FIG. 5A , in the first operation period, the first constant current switch SW1 and the second constant current switch SW2 are turned on, and the third constant current switch SW3 is turned off. In the LED lighting device 1000 according to the present invention, the driving voltage supplied to the LED light emitting unit 400 (the first driving voltage (rectified voltage Vrec) provided from the rectifying unit 200 in the non-compensation section), the compensation section From the point in time when the voltage level of the second driving voltage provided from the loopback compensator 300) becomes the forward voltage level of the first LED group 410, that is, the first forward voltage level Vf1 or higher, the first LED group The LED driving current (I _LED ) flows to the 410, and accordingly the first LED group 410 is turned on. At this time, the LED driving current (I _LED ) flowing through the first LED group 410 is a constant current controlled by the first constant current switch (SW1) to a preset value of the first LED driving current (I _LED1 ).

Next, FIG. 5B shows the relationship between the control state of the first constant current switch SW1 to the third constant current switch SW3 and the LED driving current I _LED in the second operation section. In the state shown in Fig. 5a, the driving voltage supplied to the LED light emitting unit 400 continues to rise and the forward voltage level of the first LED group 410 and the forward voltage level of the second LED group 420 are added. The voltage level, ie, the second forward voltage level (Vf2) or higher, the LED driving current (I _LED ) also flows to the second LED group 420 from the point in time, and accordingly, the second LED group 420 is also turned on. As described above, the second constant current switch SW2 connecting the second LED group 420 to the LED driving control unit 500 through the second current path P2 in the first operation period is turned on. and, accordingly, the LED driving current I _LED flowing through the second constant current switch SW2 may be detected. The LED driving control unit 500 detects the LED driving current (I _LED ) flowing through the second constant current switch (SW2), and the LED driving current (I _LED ) flowing through the second constant current switch (SW2) is in a transient state (current It is judged whether the constant current state is normally maintained after passing the rising and/or falling state). When the LED driving current (I _LED ) flowing through the second constant current switch (SW2) maintains a normal constant current state, that is, when it is stably maintained at a preset value of the second LED driving current (I _LED2 ), the LED driving control unit (500) determines that the driving voltage supplied to the LED light emitting unit 400 is sufficient to drive the first LED group 410 and the second LED group 420 (that is, the voltage level of the driving voltage is the second It is judged that the forward voltage level is higher than the forward voltage level), the first constant current switch SW1 is turned off, and the second operation period is entered. At the same time, the LED driving control unit 500 turns on the third constant current switch (SW3) to connect the third current path (P3), and the loopback compensating unit charging current (Ic) flowing through the third constant current switch (SW3) start to detect The relationship between the control state of the first constant current switch SW1 and the second constant current switch SW2 and the LED driving current I _LED at the time of entering the second operation period is illustrated in FIG. 5B .

On the other hand, since the second LED group 420 emits light together with the first LED group 410 during the second operation period, the number of LEDs that are emitted in the second operation period than in the first operation period increases. Therefore, in order to keep the light output of the LED light emitting unit 400 almost constant in the first operation period and the second operation period, the second LED driving current (I _LED2 ) is a value lower than the first LED driving current (I _LED1 ) can be set to More preferably, a relationship between the second LED driving current (I _LED2 ) and the first LED driving current (I _LED1 ) is established so that an inverse relationship is established with the number of LEDs emitted for each operation section so that the light output for each operation section is almost the same. Relationships can be established.

Next, FIG. 5C shows the relationship between the control state of the first constant current switch SW1 to the third constant current switch SW3 and the LED driving current I _LED in the charging section. As shown in FIG. 5B , the LED driving control unit 500 detects the charging current Ic during the second operation period, and the rectified voltage Vrec gradually rises so that the charging current Ic reaches a preset value. At the time of arrival, the LED driving control unit 500 enters the charging period by turning off the second constant current switch SW2. A block diagram of such a state is shown in FIG. 5C. As shown in FIG. 5C , since the second constant current switch SW2 is turned off in the charging section, the third LED driving current I _LED3 flows through the third current path P3 to the first LED group ( 410) and the loopback compensator 300. Accordingly, in this charging period, only the first LED group 410 emits light and the second LED group 420 is turned off. The LED driving control unit 500 continuously detects the third LED driving current I _LED3 flowing through the third current path P3 during the charging period.

On the other hand, after the rectified voltage Vrec reaches the maximum voltage level, it gradually decreases so that the third LED driving current I _LED3 flowing through the third current path P3 becomes less than or equal to a preset value, the LED driving control unit 500 ) controls the first constant current switch SW1 to the third constant current switch SW3 in the state shown in FIG. 5B to return to the second operation period. That is, the LED driving control unit 500 turns off the third constant current switch SW3 and turns on the second constant current switch SW2 . Therefore, as described above, both the first LED group 410 and the second LED group 420 emit light during the second operation period, and in this case, the LED driving current I _LED is the second LED driving current I _LED2 . ) value is controlled by constant current.

If the rectified voltage Vrec continues to decrease and becomes less than the second forward voltage level Vf2, the LED driving control unit 500 controls the first constant current switch SW1 to the third constant current switch SW3 in the state shown in FIG. 5B. ) to return to the first operation section. As described above, during the first operation period, only the first LED group 410 emits light and the second LED group 420 is turned off. In addition, at this time, the LED driving current (I _LED ) is a constant current control to the first LED driving current (I _LED1 ) value.

If the rectified voltage Vrec continues to decrease and becomes less than the first forward voltage level Vf1, the LED driving control unit 500 controls the first constant current switch SW1 to the third constant current switch SW3 in the state shown in FIG. 5D. ) to enter the compensation section. As can be seen by comparing FIGS. 5A and 5D , the control state of the constant current switches of FIG. 5A and the control state of the constant current switches of FIG. 5D are the same. Therefore, the control of the constant current switches may not occur substantially, and the second driving voltage is naturally supplied from the loopback compensator 300 to the first LED light emitting unit 400 due to a potential difference. Therefore, during the compensation period, the second driving voltage is provided to the first LED group 410 from the loopback compensator 300, and accordingly, the fourth LED driving current I _LED4 flows through the first current path. and the lighting state of the first LED group 410 is maintained. In this case, the fourth LED driving current (I _LED4 ) may be substantially the same as the first LED driving current (I _LED1 ).

As described above, during one cycle of the rectified voltage Vrec, the control of the first operating section, the second operating section, the charging section, the second operating section, the first operating section, and the compensation section is sequentially performed, and the rectification This control is periodically repeated for every cycle of the voltage Vrec.

6 is a waveform diagram illustrating a relationship between a rectified voltage, an LED driving current, an input current, and a light output of an LED light emitting unit according to time of the LED lighting device according to the first embodiment of the present invention shown in FIG. 4 . Figure 6 (a) shows the waveform of the rectified voltage (Vrec) over time, Figure 6 (b) shows the waveform of the LED driving current (I _LED ) over time, Figure 6 (c) ) shows the waveform of the input current Iin input from the AC power source (Vac) to the LED lighting device according to time, and (d) of FIG. 6 shows the light output waveform of the LED light emitting unit 400 according to time are doing

Referring to FIG. 6 , when the LED lighting device 1000 is initially started, since the loopback compensator 300 is not charged, the LED light emitting unit 400 does not emit light. The first LED group 410 is turned on at a time t1 when the voltage level of the rectified voltage Vrec reaches the first forward voltage level Vf1 over time. The state at this time is shown in FIG. 5A.

If the voltage level of the rectified voltage Vrec continues to rise and reaches the second forward voltage level Vf2 (t2), the LED driving control unit 500 controls the second constant current switch SW2 and the third constant current switch SW3. is turned on, and the second operation period is entered by turning off the first constant current switch SW1. This state is shown in Fig. 5b. In the second operation period, both the first LED group and the second LED group 420 are turned on, and as described above, the second LED driving current I _LED2 in the second operation period is the first LED driving current I _LED1 ) is preferably set to a lower value than the constant current control. Of course, it will be apparent to those skilled in the art that the first LED driving current (I _LED1 ) and the second LED driving current (I _LED2 ) may be set to various values as needed. For example, the first LED driving current (I _LED1 ) and the second LED driving current (I _LED2 ) may be set to the same value, and according to an embodiment, the second LED driving current (I _LED2 ) is the first LED driving It may be set higher than the current (I _LED1 ). Accordingly, as shown in (d) of FIG. 6 , the light output of the LED light emitting unit 400 in the second operation period will be substantially equal to the light output of the LED light emitting unit 400 in the first operation period. can Meanwhile, as described above, during the second operation period, the LED driving control unit 500 continuously detects whether the charging current Ic flows through the third constant current switch SW3.

When the voltage level of the rectified voltage Vrec continues to rise and the charging current Ic is stably supplied to the loopback compensator 300 (t3), the LED driving control unit 500 controls the second constant current switch SW2 ) to enter the charging section by turning it off. As shown in FIG. 5C , in this charging period, only the first LED group 410 emits light and the loopback compensator 300 is charged. At this time, the LED driving current (I _LED ) flowing through the first LED group 410 and the loopback compensator 300 is a constant current to the third LED driving current (I _LED3 ) preset by the third constant current switch SW3. may be controlled, and according to an embodiment, the value of the first LED driving current (I _LED1 ) and the value of the third LED driving current (I _LED3 ) may be set to be the same. This is to reduce the optical output deviation according to the operation section.

When the voltage level of the rectified voltage Vrec falls past the highest point and the charging current is not stably supplied to the loopback compensator 300 (t4), the LED driving control unit 500 operates as shown in FIG. 5b. Similarly, by turning on the second constant current switch SW2, the second operation period is entered.

If the voltage level of the rectified voltage Vrec continues to fall and becomes less than the second forward voltage level Vf2 (t5), the LED driving control unit 500 operates the first constant current switch SW1 as shown in FIG. 5A . The first operation period is entered by turning on and turning off the third constant current switch SW3. At this time, the LED driving control unit 500 is configured to determine whether the voltage level of the rectified voltage Vrec is less than the second forward voltage level Vf2 by detecting the second LED driving current I _LED2 . That is, when the detected second LED driving current I _LED2 is less than or equal to a preset value, the LED driving control unit 500 determines that the voltage level of the rectified voltage Vrec is less than the second forward voltage level Vf2. can be

If the voltage level of the rectified voltage Vrec continues to drop and becomes less than the first forward voltage level Vf1 (t6), the second driving voltage from the loopback compensator 300 is applied to the first LED as shown in FIG. 5D . It is supplied to the group 410 so that the first LED group 410 emits light. As described above, at this point in time, a separate constant current switch control is not performed, and discharge from the loopback compensator 300 to the first LED group 410 may be performed naturally by a potential difference.

When the voltage level of the rectified voltage Vrec rises again and becomes equal to or higher than the first forward voltage level Vf1 (t8), the first LED group 410 is turned on again by the rectified voltage Vrec as shown in FIG. 5A . will glow The sequential control processes as described above are periodically repeated for each cycle of the rectified voltage Vrec.

Meanwhile, as can be seen in (d) of FIG. 6 , it can be confirmed that the LED light emitting unit 400 maintains an almost constant light output over all sections of the rectified voltage Vrec. This is an effect that can be achieved by controlling the second LED driving current I _LED2 in the second operation period to a lower value than the first LED driving current I _LED1 .

In the above, for convenience of explanation and illustration, the LED light emitting unit 400 has been described with reference to an embodiment consisting of two LED groups of the first LED group 410 and the second LED group 420, but the LED It will be apparent to those skilled in the art that the same method can be applied to an embodiment in which the light emitting unit 400 consists of three or four or more LED groups, and that these embodiments fall within the scope of the present invention. It will be apparent to those skilled in the art.

Configuration and function of the second embodiment of the LED lighting device 1000

7 is a schematic structural block diagram of an LED lighting device according to a second embodiment of the present invention, and FIGS. 8A to 8D are the operation sections of the LED lighting device according to the second embodiment of the present invention shown in FIG. It is a block diagram showing the switch control state and the LED driving current. Hereinafter, the configuration and function of the LED lighting device 1000 according to the second embodiment of the present invention will be described in detail with reference to FIGS. 7 and 8A to 8D .

The LED lighting device 1000 according to the second embodiment of the present invention shown in FIG. 7 is a fourth between the node between the first LED group 410 and the second LED group 420 and the loopback compensator 300 . The configuration of the LED lighting device 1000 according to the first embodiment shown in FIG. 4 is similar except that the switch SW4 is provided. Therefore, for the overlapping configuration and function, reference will be made to the description of FIG. 4 , and below, the LED lighting device 1000 according to the second embodiment of the present invention will be mainly focused on the differences from the first embodiment. do.

First, the fourth switch SW4 as shown in FIG. 7 may be included to more precisely control the charging/discharging process of the loopback compensator 300 according to the control of the LED driving controller 500 .

Specifically, during the first operation period, the fourth switch SW4 maintains a turn-off state as shown in FIG. 8A . Accordingly, no current flows to the loopback compensator 300 during the first operation period.

Next, as shown in FIG. 8B , at the time of entering the second operation period, the fourth switch SW4 is turned on and the current path between the rectifier 200 and the loopback compensator 300 is connected, and such The charging current Ic may flow to the loopback compensator 300 through the current path.

Next, as shown in FIG. 8C , even at the time of entering the charging section, the fourth switch SW4 maintains the turn-on state so that the loopback compensator 300 is continuously charged by the charging current Ic. make it possible

Again, even when entering the second operation period from the charging period, as shown in FIG. 8B , the fourth switch SW4 maintains the turn-on state. Then, at the time of entering the first operation period from the second operation period, as shown in FIG. 8A , the fourth switch SW4 is turned off.

On the other hand, when the voltage level of the rectified voltage Vrec is less than the first forward voltage level Vf1, the LED lighting device 1000 according to the second embodiment enters the compensation section. Even during the compensation period, the fourth switch SW4 maintains the turn-off state. 8d and 8e show the control state of the first constant current switch SW1 to the fourth switch SW4 in the LED lighting device 1000 during the compensation period.

It should be noted that, unlike the first embodiment, the loopback compensator 300 according to the second embodiment of the present invention is configured to compensate both the second operation period and the first operation period. More specifically, when the voltage level of the rectified voltage Vrec is less than the first forward voltage level Vf1, the second driving voltage from the loopback compensator 300 is generated by the potential difference between the first LED group 410 and the second It is supplied to the LED group 420 . Accordingly, at this time, as shown in FIG. 8D , the first constant current switch SW1 is turned off and the second constant current switch SW2 maintains the turned-on state. At this time, the fourth LED driving current (I _LED4 ) flows, and the fourth LED driving current (I _LED4 ) is constant current controlled to a constant value by the second constant current switch (SW2). The fourth LED driving current (I _LED4 ) may be set to the same value as the second LED driving current (I _LED2 ).

In addition, when the second driving voltage supplied from the loopback compensator 300 decreases over time and becomes less than the second forward voltage level Vf2, the fourth LED driving current I _LED4 is lower than a preset value. falls, and at this point in time, the LED driving control unit 500 turns on the first constant current switch SW1. Therefore, only the first LED group 410 emits light in this section, and the fifth LED driving current I _LED5 flowing at this time is constant current controlled by the first constant current switch SW1 to a preset value. The fifth LED driving current (I _LED5 ) may be set to the same value as the first LED driving current (I _LED1 ).

When the voltage level of the rectified voltage Vrec rises again to reach the first forward voltage level Vf1, the LED lighting device 1000 becomes the state of FIG. 8A. As described above, since the control state of the constant current switches in the last compensation period and the control state of the constant current switches in the first driving period are the same, it is not necessary to control the constant current switches separately.

Configuration and function of the third embodiment of the LED lighting device 1000

9 is a schematic structural block diagram of an LED lighting device according to a third embodiment of the present invention. Referring to FIG. 9 , the configuration and function of the LED lighting device 1000 according to the third embodiment of the present invention will be described in detail.

The LED lighting device 1000 according to the third embodiment of the present invention shown in FIG. 9 is shown in FIG. 4 , except that the second compensation unit 310 is provided in parallel with the second LED group 420 . The configuration of the LED lighting device 1000 according to the first embodiment is similar. Therefore, for the overlapping configuration and functions, reference will be made to the description of FIG. 4 , and below, the LED lighting device 1000 according to the third embodiment of the present invention will be mainly described with respect to the differences from the first embodiment. do.

As shown in FIG. 9 , the second compensation unit 310 according to the present invention may be implemented as a second capacitor C2, but is not limited thereto, and various electrical charging/discharging devices and/or electrical charging/discharging circuits. can be implemented using The second compensator 310 is charged in the second operation period as described above, and in an operation period other than the second operation period (ie, an operation period in which the second LED group 420 is turned off), the second LED group 420 is ) to perform a function of supplying a second driving voltage. Accordingly, in the case of the third embodiment as shown in FIG. 9 , the first LED group 410 and the second LED group 420 may always maintain a lit state over all sections of the rectified voltage Vrec.

Configuration and function of the fourth embodiment of the LED lighting device 1000

10 is a schematic structural block diagram of an LED lighting device according to a fourth embodiment of the present invention. Referring to FIG. 10 , the configuration and function of the LED lighting device 1000 according to the fourth embodiment of the present invention will be described in detail.

The LED lighting device 1000 according to the fourth embodiment of the present invention shown in FIG. 10 is a first LED driving current setting unit 610 for setting the first LED driving current (I _LED1 ) to a desired value, the second A second LED driving current setting unit 620 for setting the LED driving current (I _LED2 ) to a desired value, a third LED driving current setting unit 630 for setting the third LED driving current (I _LED3 ) to a desired value ) may be further included. Except for these points, the configuration of the LED lighting device 1000 according to the first embodiment shown in FIG. 4 is similar. Therefore, for the overlapping configuration and functions, reference will be made to the description of FIG. 4 , and below, the LED lighting device 1000 according to the fourth embodiment of the present invention will be mainly described with respect to the differences from the first embodiment. do.

In the case of the LED lighting device 1000 according to the prior art described with reference to FIGS. 2 and 3 , the first LED driving current (I _LED1 ), the second LED driving current (I _LED2 ), and the third LED driving current (I _LED3 ) ), and the fourth LED driving current (I _LED4 ) could not be set, respectively. That is, in the case of the LED lighting device 1000 according to the prior art, since it is configured to control the LED driving current (I _LED ) for each operation section in the form of a step wave, generally one LED driving current (eg, the fourth The LED driving current (I _LED4 )) was set, and the remaining LED driving currents were configured to be controlled as a ratio of the set LED driving current. For example, the third LED driving current (I _LED3 ) is 80-95% of the fourth LED driving current (I _LED4 ), the second LED driving current ( _ILED2 ) is 65- of the fourth LED driving current (I _LED4 ) 80%, the first LED driving current (I _LED1 ) was set to 30 to 65% of the fourth LED driving current (I _LED4 ). However, in the case of the LED lighting device 1000 according to the prior art, there is a problem that only each LED driving current (I _LED ) cannot be set separately. This is a problem in that it is difficult to arbitrarily set the LED driving current for each operation section rather than adjusting the current. Therefore, in the case of the LED lighting device 1000 according to the fourth embodiment of the present invention, the first LED driving current setting unit 610, the second LED driving current setting unit 620, and the third LED driving current setting unit 630 is provided separately, and is configured to set each LED driving current (I _LED ) as needed. In FIG. 10 , an embodiment in which the first LED driving current setting unit 610 , the second LED driving current setting unit 620 , and the third LED driving current setting unit 630 is implemented using a variable resistor is shown. Although illustrated, it will be apparent to those skilled in the art that the driving current setting unit may be implemented with other suitable devices (eg, capacitors, etc.) or other suitable circuits.

Configuration and function of the fifth embodiment of the LED lighting device 1000

11 is a schematic structural block diagram of an LED lighting device according to a fifth embodiment of the present invention, and FIGS. 12A to 12C are operation sections of the LED lighting device according to the fifth embodiment of the present invention shown in FIG. It is a block diagram showing the switch control state and the LED driving current. Also, FIG. 13 is a waveform diagram illustrating the relationship between the rectified voltage, the LED driving current, the input current, and the light output of the LED light emitting unit according to time of the LED lighting device according to the fifth embodiment of the present invention shown in FIG. 11 . Hereinafter, the configuration and function of the LED lighting device 1000 according to the fifth embodiment of the present invention will be described in detail with reference to FIGS. 11 to 13 .

First, the LED lighting device 1000 according to the fifth embodiment of the present invention operates in two stages in the same way as the LED lighting devices 1000 according to the first to fourth embodiments described above. Although there are similar aspects, there is a difference in that deformation is sequentially driven rather than sequentially driven. Basically, "sequential driving" means "1st stage operation section (discharge section) -> 1st stage operation section (non-compensation section) according to the voltage level of the rectified voltage Vrec based on one cycle of the rectified voltage Vrec. -> 2nd stage operation section (charging section) -> 1st stage operation section (non-compensation section) -> 1st stage operation section (discharge section)” means a driving method in which the operating section is changed. On the other hand, the LED lighting device 1000 according to the fifth embodiment of the present invention has a “two-stage operation section (discharge section) -> 2nd stage operation section (non-compensation section) -> 1st stage operation section (charging section) -> 2nd stage operation section (non-compensation section) -> 2nd stage operation section (discharge section)" This is referred to as a modified sequential driving method. That is, more LED groups emit light in a relatively lower voltage level section, fewer LED groups emit light in a relatively higher voltage level section, and the loopback compensator 300 is charged at the same time. In addition, in this embodiment, the charging section entry voltage level (Vcharge), which is a reference for entering and leaving the charging section, is higher than the second forward voltage level (Vf2). Also, in this embodiment, the loopback compensator 300 is selected to perform the second forward voltage level compensation. That is, the capacity of the loopback compensator 300 is determined to supply the second driving voltage to the first LED group 410 and the second LED group 420 during the compensation period.

In the LED lighting device 1000 according to the fifth embodiment of the present invention, the loopback compensator 300 includes a first LED group 410 as shown in FIG. 11 in order to perform the function as described above. And it is located between the node between the second LED group 420 and the first constant current switch SW1 to be charged during the first stage operation period, and the first LED group 410 and the second LED through the discharge path during the non-compensation period. It is configured to supply a third LED driving current I _LED3 to the group 420 .

In addition, in order to perform the function as described above, the LED driving control unit 500 according to the fifth embodiment of the present invention includes the first constant current switch SW1 and the second constant current switch SW1 according to the voltage level of the rectified voltage Vrec. 2 by controlling the constant current switch (SW2) is configured to control the transformation sequential driving of the first LED group 410 and the second LED group (420). The control of the first constant current switch SW1 and the second constant current switch SW2 may be performed based on one of the driving voltage detection method and the driving current detection method as described above. Hereinafter, a driving control process of the LED lighting device 1000 according to the fifth embodiment of the present invention will be described in detail with reference to FIGS. 12A to 12C and 13 .

First, when the LED lighting device 1000 according to the fifth embodiment of the present invention is started, as shown in FIG. 12A , the second constant current switch SW2 is turned on, and the first constant current switch SW1 is It is turned off. When the LED lighting device 1000 is started, as shown in FIG. 13 , the LED driving current does not flow before the voltage level of the rectified voltage Vrec reaches the second forward voltage level Vf2, and the rectified voltage ( From the time t1 when the voltage level of Vrec) reaches the second forward voltage level Vf2, the second LED driving current I _LED2 flows through the second current path P2. This state is shown in Fig. 12A. At this time, the LED driving current (I _LED ) flowing through the first LED group 410 and the second LED group 420 is a preset value of the second LED driving current (I _LED2 ) to the second constant current switch SW2. is controlled by constant current.

In addition, as shown in FIG. 13 , when the voltage level of the rectified voltage Vrec increases as time elapses and reaches the charging section entry voltage level Vcharge (t2), the LED driving control unit 500 controls the second The charging period is entered by turning off the constant current switch SW2 and turning on the first constant current switch SW1. Here, the charging section entry voltage level Vcharge means a threshold voltage level at which the charging current Ic starts to flow while the first LED group 410 and the loopback compensator 300 are connected in series with each other. A block diagram of this state is shown in Fig. 12B. 12B, since the second constant current switch SW2 is turned off in the charging section, the first LED driving current I _LED1 flows through the first current path P1 to the first LED group ( 410) and the loopback compensator 300. Accordingly, in this charging period, only the first LED group 410 emits light and the second LED group 420 is turned off. The LED driving control unit 500 continuously detects the first LED driving current (I _LED1 ) flowing through the first current path (P1) during the charging period and controls the constant current to a preset first LED driving current (I _LED1 ) value. do.

Meanwhile, since only the first LED group 410 emits light during the first operation period, the number of LEDs that emit light in the first operation period than in the second operation period is reduced. Therefore, in order to keep the light output of the LED light emitting unit 400 almost constant in the first operation period and the second operation period, the second LED driving current (I _LED2 ) is a value lower than the first LED driving current (I _LED1 ) can be set to More preferably, a relationship between the second LED driving current (I _LED2 ) and the first LED driving current (I _LED1 ) is established so that an inverse relationship is established with the number of LEDs emitted for each operation section so that the light output for each operation section is almost the same. Relationships can be established. Therefore, as can be seen in (e) of FIG. 13 , the light output of the LED lighting device 1000 may be constantly maintained over the entire section.

As shown in FIG. 13 , as time elapses, the rectified voltage Vrec gradually decreases after reaching the maximum voltage level and becomes less than the charging section entry voltage level Vcharge (t3), the LED driving control unit 500 is determined to depart from the charging period (ie, the first operation period) and returns to the second operation period by controlling the first constant current switch SW1 and the second constant current switch SW2 in the state shown in FIG. 12A again. . That is, the LED driving control unit 500 turns off the first constant current switch SW1 and turns on the second constant current switch SW2 .

As shown in FIG. 13, when the rectified voltage Vrec continues to decrease over time and becomes less than the second forward voltage level Vf2 (t4), the LED driving control unit 500 is configured as shown in FIG. 12c. In this state, the first constant current switch SW1 and the second constant current switch SW2 are controlled to enter the compensation section. As can be seen by comparing FIGS. 12A and 12C , the control state of the constant current switches of FIG. 12A and the control state of the constant current switches of FIG. 12C are the same. Therefore, the control of the constant current switches may not occur substantially, and only the first LED group 410 and the second LED group 420 naturally receive the second driving voltage from the loopback compensator 300 through the discharge path due to the potential difference. ) will be supplied. Therefore, during the compensation period, the second driving voltage from the loopback compensator 300 is provided to the first LED group 410 and the second LED group 420, and accordingly, the third LED through the second current path. The driving current I _LED3 flows, and the lighting state of the first LED group 410 and the second LED group 420 is maintained. In this case, the third LED driving current (I _LED3 ) may be substantially the same as the second LED driving current (I _LED2 ).

As described above, in the LED lighting device 1000 according to the fifth embodiment of the present invention, during one cycle of the rectified voltage Vrec after the initial start-up, "two-stage operation section (discharge section) -> 2 Stage 1 operation section (non-compensation section) -> 1st stage operation section (charge section) -> 2nd stage operation section (non-compensation section) -> 2nd stage operation section (discharge section)” is controlled sequentially, and rectification This control is periodically repeated for every cycle of the voltage Vrec.

When using the LED lighting device 1000 according to the fifth embodiment of the present invention as described above, compared to the first to fourth embodiments described above, (i) all LED groups emit light in the compensation section Therefore, the light uniformity is improved, (ii) electrical characteristics (power factor, total harmonic distortion factor, etc.) are improved, and (iii) the number of constant current switches is reduced, so that the circuit design is easy and the manufacturing cost is expected to be reduced. can

1000: LED lighting device 200: rectifying unit
300: loopback compensation unit 310: second compensation unit
400: LED light emitting unit 410: first LED group
420: second LED group 500: LED driving control unit
SW1: first constant current switch SW2: second constant current switch
SW3: third constant current switch SW4: fourth switch
610: first LED driving current setting unit 620: second LED driving current setting unit
630: third LED driving current setting unit

Claims (27)

a rectifying unit for full-wave rectification of an AC voltage connected to the AC power source and providing the full-wave rectified rectified voltage as a first driving voltage to the LED light emitting unit;
The first LED group to the nth LED group (n is a positive integer greater than or equal to 2) is configured to include, and is supplied with the rectified voltage from the rectifier as the first driving voltage in the non-compensation section to emit light, and loopback in the compensation section an LED light emitting unit receiving a second driving voltage from the compensating unit and emitting light;
It is located between the n-1 th LED group and the node between the n th LED group and the LED driving control unit, and charges energy using the rectified voltage in the charging period, and the second in the LED light emitting unit in the compensation period. A loop-back compensator providing a driving voltage; And
LEDs for detecting LED driving current flowing through constant current switches respectively connected to the first LED group to the nth LED group, and controlling sequential driving of the first LED group to the nth LED group according to the detected LED driving current comprising a drive control unit;
The LED driving control unit detects the charging current flowing through the constant current switch connected to the loopback compensator to determine whether to enter or leave the charging period, and turns off the constant current switch connected to the nth LED group at the time of entering the charging period. , The LED lighting device that turns on the constant current switch connected to the nth LED group at the time of departure from the charging section.
The method of claim 1,
The LED driving control unit turns on the constant current switch connected to the loopback compensator at the time of entering the nth operation period from the n-1 th operation period according to the rise of the rectified voltage and detects the charging current flowing therethrough, When the detected charging current rises above a preset value, the nth LED group is turned off and enters a charging section, and when the detected charging current falls below a preset value after entering the charging section, the nth LED group is turned off An LED lighting device that re-lights the LED group and enters the n-th operation section again.
3. The method of claim 2,
The LED driving control unit is:
Each of the first LED group to the nth LED group is connected to the cathode terminal to connect or separate the first current path to the nth current path according to the operation period, and the LED driving current is converted into a constant current in each operation period. a first constant current switch to an nth constant current switch for controlling; and
It is located between the loopback compensator and the LED driving control unit to connect or disconnect the n+1th current path between the loopback compensator and the LED driving control unit, and converts the n+1th LED driving current into a constant current in the charging section. An n+1 th constant current switch for controlling, the LED lighting device.
4. The method of claim 3,
The n+1th LED driving current value is set equal to the n-1th driving current value, the LED lighting device.
The method of claim 1,
The LED driving control unit sets the LED driving current (first LED driving current to the nth LED driving current) value for each operation section based on the total number of LEDs emitted for each operation section, and sets the LED driving current value for each operation section In accordance with the constant current control of the LED driving current in the corresponding operation section, the first LED driving current to the nth LED driving current are set in a sequentially decreasing manner.
The method of claim 1,
The LED driving control unit sets the LED driving current (first LED driving current to nth LED driving current) value for each operation section so as to be inversely proportional to the total number of LEDs emitted for each operation section, and sets the LED driving current value for each operation section. An LED lighting device that controls the LED driving current in the corresponding operation section with constant current according to the
The method of claim 1,
The LED light emitting unit includes a first LED group and a second LED group,
The difference between the light output of the first LED group during the first operation period and the light output of the first LED group and the second LED group during the second operation period is equal to or less than a preset light output deviation.
The method of claim 1,
The LED light emitting unit includes a first LED group and a second LED group,
The second driving voltage is equal to or higher than the forward voltage level of the first LED group, the LED lighting device.
The method of claim 1,
The LED light emitting unit includes a first LED group and a second LED group,
and a forward voltage level of the first LED group is greater than a forward voltage level of the second LED group.
3. The method of claim 2,
The LED lighting device,
The n-1 th LED group and the n+2 th switch positioned between the loopback compensator and the node between the n-1 th LED group and turned on or off according to the control of the LED driving controller further comprises: ,
The LED driving control unit turns on the n + 2 th switch at the time of entering the n th operation period, and turns off the n + 2 th switch at the time of entering the compensation period, the LED lighting device.
3. The method of claim 2,
The LED lighting device,
A second compensator connected in parallel to the n-th LED group, charged during the n-th operation period and supplying a driving voltage to the n-th LED group during a non-emission period in which the n-th LED group does not emit light, further comprising , LED lighting devices.
The method of claim 1,
The LED driving control unit further includes a first LED driving current setting unit to an n+1th LED driving current setting unit capable of setting a corresponding LED driving current value among the first LED driving current value to the n+1th LED driving current value, respectively. Including, LED lighting system.
13. The method of claim 12,
Each of the first LED driving current setting unit to the n+1th LED driving current setting unit is composed of a variable resistor, an LED lighting device.
An LED driving circuit comprising a first LED group to an nth LED group (n is a positive integer of 2 or more) and controlling the driving of an LED light emitting unit receiving a full-wave rectified rectified voltage from the rectifying unit as a first driving voltage,
It is located between the n-1 th LED group and the node between the n th LED group and the LED driving control unit, and charges energy using the rectified voltage in the charging period, and a second driving voltage to the LED light emitting unit in the compensation period. A loop-back compensation unit that provides; And
LEDs for detecting LED driving current flowing through constant current switches respectively connected to the first LED group to the nth LED group, and controlling sequential driving of the first LED group to the nth LED group according to the detected LED driving current comprising a drive control unit;
The LED driving control unit detects the charging current flowing through the constant current switch connected to the loopback compensator to determine whether to enter or leave the charging period, and turns off the constant current switch connected to the nth LED group at the time of entering the charging period. , LED driving circuit for turning on the constant current switch connected to the nth LED group at the time of departure from the charging section.
15. The method of claim 14,
The LED driving control unit turns on the constant current switch connected to the loopback compensator at the time of entering the nth operation period from the n-1 th operation period according to the rise of the rectified voltage and detects the charging current flowing therethrough, When the detected charging current rises above a preset value, the nth LED group is turned off and enters a charging section, and when the detected charging current falls below a preset value after entering the charging section, the nth LED group is turned off An LED driving circuit that re-lights the LED group and enters the n-th operation section again.
16. The method of claim 15,
The LED driving control unit is:
Each of the first LED group to the nth LED group is connected to the cathode terminal to connect or separate the first current path to the nth current path according to the operation period, and the LED driving current is converted into a constant current in each operation period. a first constant current switch to an nth constant current switch for controlling; and
It is located between the loopback compensator and the LED driving control unit to connect or disconnect the n+1th current path between the loopback compensator and the LED driving control unit, and converts the n+1th LED driving current into a constant current in the charging section. Including an n+1th constant current switch for controlling, the LED driving circuit.
17. The method of claim 16,
The n+1th LED driving current value is set equal to the n-1th driving current value.
15. The method of claim 14,
The LED driving control unit sets the LED driving current (first LED driving current to the nth LED driving current) value for each operation section based on the total number of LEDs emitted for each operation section, and sets the LED driving current value for each operation section In accordance with the constant current control of the LED driving current in the corresponding operation period, the first LED driving current to the nth LED driving current are set in a sequentially decreasing manner.
15. The method of claim 14,
The LED driving control unit sets the LED driving current (first LED driving current to nth LED driving current) value for each operation section so as to be inversely proportional to the total number of LEDs emitted for each operation section, and sets the LED driving current value for each operation section. LED driving circuit that controls the LED driving current in the corresponding operation section with constant current according to the
15. The method of claim 14,
When the LED light emitting unit includes a first LED group and a second LED group,
The second driving voltage is equal to or higher than the forward voltage level of the first LED group, the LED driving circuit.
15. The method of claim 14,
When the LED light emitting unit includes a first LED group and a second LED group,
and a forward voltage level of the first LED group is greater than a forward voltage level of the second LED group.
16. The method of claim 15,
The LED driving circuit,
The n-1 th LED group and the n+2 th switch positioned between the loopback compensator and the node between the n-1 th LED group and turned on or off according to the control of the LED driving controller further comprises: ,
The LED driving control unit turns on the n+2 th switch at the time of entering the nth operation period, and turns off the n+2 th switch at the time of entering the compensation period, the LED driving circuit.
16. The method of claim 15,
The LED driving circuit,
A second compensator connected in parallel to the n-th LED group, charged during the n-th operation period and supplying a driving voltage to the n-th LED group during a non-emission period in which the n-th LED group does not emit light, further comprising , LED driving circuit.
15. The method of claim 14,
The LED driving control unit further includes a first LED driving current setting unit to an n+1th LED driving current setting unit capable of setting a corresponding LED driving current value among the first LED driving current value to the n+1th LED driving current value, respectively. Including, LED driving circuit.
25. The method of claim 24,
Each of the first LED driving current setting unit to the n+1th LED driving current setting unit is composed of a variable resistor, an LED driving circuit.
a rectifying unit for full-wave rectification of an AC voltage connected to the AC power source and providing the full-wave rectified rectified voltage as a first driving voltage to the LED light emitting unit;
Consists of a first LED group and a second LED group, receives the rectified voltage from the rectifier as the first driving voltage in the non-compensation section to emit light, and supplies a second drive voltage from the loopback compensator in the compensation section an LED light emitting unit that receives and emits light;
It is located between a node between the first LED group and the second LED group and an LED driving control unit, and charges energy using the rectified voltage in a charging period (first operation period), and in the compensation period, the first a loopback compensator providing the second driving voltage to the LED group and the second LED group; And
The LED driving current flowing through the constant current switches respectively connected to the first LED group and the second LED group is detected, and the transformation sequential driving of the first LED group and the second LED group is controlled according to the detected LED driving current. Including an LED driving control unit,
The LED driving control unit detects the charging current flowing through the constant current switch connected to the loopback compensation unit to determine whether to enter or leave the charging period, and turns off the constant current switch connected to the second LED group at the time of entering the charging period. , The LED lighting device that turns on the constant current switch connected to the second LED group at the time of departure from the charging section.
An LED driving circuit comprising a first LED group and a second LED group, the LED driving circuit controlling the driving of an LED light emitting unit receiving a full-wave rectified rectified voltage from the rectifying unit as a first driving voltage,
It is located between a node between the first LED group and the second LED group and an LED driving control unit, and charges energy using the rectified voltage in a charging period (first operation period), and in a compensation period, the first LED a loopback compensator for providing a second driving voltage to the group and the second LED group; And
The LED driving current flowing through the constant current switches respectively connected to the first LED group and the second LED group is detected, and the transformation sequential driving of the first LED group and the second LED group is controlled according to the detected LED driving current. Including an LED driving control unit,
The LED driving control unit detects the charging current flowing through the constant current switch connected to the loopback compensation unit to determine whether to enter or leave the charging period, and turns off the constant current switch connected to the second LED group at the time of entering the charging period. , The LED lighting device that turns on the constant current switch connected to the second LED group at the time of departure from the charging section.

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