KR101498103B1 - Apparatus and method for driving light emitting diode - Google Patents

Abstract

The present invention relates to a light emitting diode driving apparatus, and more particularly, to a light emitting diode driving apparatus in which an output current from a light emitting diode unit having at least one light emitting diode is sensed and a current sensing And a control unit that determines an actual characteristic graph of an output current with respect to a driving voltage of the light emitting diode unit using the sensing signal output from the current sensing unit and determines a size of a plurality of divided output current axes The number of division steps is divided according to the ratio of the number of divisions of the plurality of pre-driving compression sections divided on the basis of the determined threshold voltage of the actual characteristic graph, For each brightness control stage of the brightness control switch And a light emitting diode control unit for calculating a voltage.

Description

TECHNICAL FIELD [0001] The present invention relates to a light emitting diode (LED)

The present invention relates to an apparatus and a method for driving a light emitting diode.

BACKGROUND OF THE INVENTION [0002] Along with the exponential growth of lighting devices using light emitting diodes (LEDs), various circuits have been emerging that supply regulated power to light emitting diodes.

BACKGROUND ART [0002] In recent years, precise control for constant currents has been demanded for light emitting diodes (LEDs) used in a wide range of fields ranging from a flashlight to an electric bulletin board of an athletic field. In most cases, feedback control of the driving state of a light emitting diode A dimming control is performed.

However, due to the brightness characteristic of the driving voltage of the light emitting diode, the amount of change in brightness according to the amount of voltage variation is not constant, so that it is difficult to control the dimming of the light emitting diode.

In particular, when the brightness of the light emitting diode is changed by using the brightness control switch, the brightness variation is not constant and the satisfaction of the user is decreased.

Furthermore, in the case of a high-luminance LED that outputs a current of about 5 A to 50 A, the brightness non-uniformity due to a constant brightness variation becomes more conspicuous, thereby further reducing a user's satisfaction.

Further, when driving a light emitting diode, a driving method of a light emitting diode in consideration of wiring resistance is not developed, and a capacitance change of a light emitting diode due to wiring resistance, that is, a change of an output current is made, There arises a problem of decreasing the amount of water.

Korean Registered Patent No. 10-1002600 (Registered Date: December 14, 2010, Applicant: EGJS Tech Co., Ltd.)

SUMMARY OF THE INVENTION Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art.

Another technical problem to be solved by the present invention is to improve user satisfaction.

According to an aspect of the present invention, there is provided a light emitting diode driving apparatus including a current sensing unit for sensing an output current outputted from a light emitting diode unit having at least one light emitting diode and outputting a corresponding sensing signal, Determining an actual characteristic graph of an output current with respect to a driving voltage of the LED unit using the output sensing signal, dividing a total number of division steps according to a ratio of a plurality of divided output current axes based on a threshold voltage, And a step of dividing the plurality of pre-drive compression sections by a threshold voltage of the determined actual characteristic graph as a reference, And a light emitting diode control unit for calculating a driving voltage for each brightness control stage do.

It is preferable that the total number of division steps is determined according to the total number of brightness control stages of the brightness control switch.

According to another aspect of the present invention, there is provided a light emitting diode driving apparatus including a current sensing unit for sensing an output current outputted from a light emitting diode unit having at least one light emitting diode and outputting a corresponding sensing signal, Wherein the actual characteristic graph of the output current with respect to the driving voltage of the light emitting diode section is determined using the output sensing signal, and a section in which a plurality of parts divided on the basis of the tilt change point in the determined actual characteristic graph are respectively maintained Dividing the number of division steps for a plurality of divided pre-driving compression sections based on the threshold voltage of the actual characteristic graph according to the number of division steps calculated, Light emission for calculating the driving voltage for each brightness control stage of the brightness control switch Including the odd control, and the virtual characteristic graph is a graph obtained using the minimum current point and the maximum current point of the actual characteristic graph.

It is preferable that the inclination change point is a point at which the change amount of the inclination in the actual characteristic graph is equal to or larger than the set value.

The at least one light emitting diode may be a light emitting diode that outputs an output current of 5A to 50A.

Wherein the light emitting diode control unit divides the virtual characteristic graph into a plurality of portions around a point at which the tilt change point and the virtual characteristic graph are perpendicular to each other and adjusts the virtual characteristic graph based on a ratio of a straight line distance to a plurality of portions of the virtual characteristic graph Dividing the total number of division steps for all the straight line distances of the virtual characteristic graph so as to determine the number of division steps respectively assigned to the plurality of portions of the virtual characteristic graph, and based on the number of division steps of the determined virtual characteristic graph So that the number of division steps for each section for each part of the actual characteristic graph can be calculated.

According to another aspect of the present invention, there is provided a method of driving a light emitting diode, the method comprising: outputting a driving voltage to a light emitting diode unit and calculating an actual characteristic graph using an output current outputted from the light emitting diode unit; Dividing the number of division steps into a plurality of current sections based on a threshold voltage of the plurality of current sections, dividing the total number of division steps according to the size ratio of the plurality of divided current sections, Dividing each of the plurality of pre-driving compression sections by setting the determined number of division steps to the number of division steps for a plurality of divided pre-driving compression sections based on at least one threshold voltage of the actual characteristic graph, Based on the divided dividing step, the brightness control switches for each brightness control stage And calculating a driving voltage.

According to another aspect of the present invention, there is provided a method of driving a light emitting diode, the method comprising the steps of: outputting a driving voltage to a light emitting diode unit and calculating an actual characteristic graph using an output current outputted from the light emitting diode unit; Calculating a virtual characteristic graph using a current point, dividing the plurality of portions of the virtual characteristic graph using at least one tilt change point of the real characteristic graph, Dividing a section of a plurality of sections centered at the at least one slope change point in the actual characteristic graph according to a length ratio of the plurality of sections to the number of division steps for each of the plurality of sections, On the basis of the brightness control signal, And a step of calculating the pressure.

It is preferable that the at least one tilt change point is a point where the change amount of the tilt in the actual characteristic graph is equal to or greater than a set value.

The plurality of portions of the virtual characteristic graph may be divided around a point where a straight line passing through the at least one tilt change point is perpendicular to the virtual characteristic graph.

According to this aspect, the drive voltage of the brightness control end of the light emitting diode portion is calculated based on the actual characteristic graph of the light emitting diode portion in which the wiring resistance is reflected. This improves the uniformity of the brightness variation according to the voltage change of the light emitting diode portion regardless of the wiring resistance, thereby increasing the satisfaction of the user.

1 is a block diagram of an LED driving apparatus according to an embodiment of the present invention.
2 is a graph showing the operating characteristics of the light emitting diode.
3 is a flowchart illustrating an operation of the LED controller of the LED driving apparatus according to the embodiment of the present invention.
4 is a view for explaining an example of a method of calculating a driving voltage for each brightness control end of a brightness control switch in an LED controller of an LED driving apparatus according to an embodiment of the present invention.
5 is a graph showing an actual characteristic graph and a virtual characteristic graph in the LED driving apparatus according to an embodiment of the present invention.
FIG. 6 is a graph showing the relationship between the number of division steps of an actual characteristic graph on the basis of the virtual characteristic graph in the LED controller of the LED driving apparatus according to the embodiment of the present invention and calculating the driving voltage for each brightness control end of the brightness control switch Fig. 7 is a view for explaining another example of a method for performing the above-described method.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Hereinafter, an LED driving apparatus and method according to an embodiment of the present invention will be described with reference to the accompanying drawings.

First, a light emitting diode driving apparatus according to an embodiment of the present invention will be described in detail with reference to FIG.

Referring to FIG. 1, an LED driving apparatus according to an exemplary embodiment of the present invention includes a light emitting diode unit 100, a brightness control switch 10 for outputting a brightness control signal of the LED unit 100, A light emitting diode control unit 20 connected to the light emitting diode unit 10, a voltage conversion unit 30 connected between the light emitting diode control unit 20 and the light emitting diode unit 100, And a current sensing unit (40) connected between the current sensing unit (20).

The light emitting diode unit 100 includes at least one light emitting diode (LED). When the light emitting diode unit 100 includes a plurality of light emitting diodes, the plurality of light emitting diodes may be connected in series or in parallel .

At this time, the light emitting diode unit 100 is connected to the voltage conversion unit 30 through the wiring L1, which is an input line, and is connected to the current sensing unit 40 through the wiring L2, which is an output line.

In addition, the light emitting diode constituting the light emitting diode unit 100 may be a high luminance light emitting diode which outputs a current of about 5A to 50A.

The brightness control switch 10 is for changing the brightness state of the light emitting diode unit 100 step by step according to the user's operation and outputs a brightness control signal of a size corresponding to each stage. For example, the number of brightness control stages of the light emitting diode unit 100 by the brightness control switch 10 may be 1,000.

The light emitting diode control unit 20 outputs a driving signal for controlling the brightness state of the light emitting diode unit 100 according to a brightness control signal output from the brightness control switch 10. [

At this time, the light emitting diode control unit 20 determines the operation characteristics of the light emitting diode unit 100 according to the wiring resistance of the wirings L1 and L2 forming the input and output ends of the light emitting diode unit 100, The brightness of the light emitting diode unit 100 is controlled based on the operation characteristics of the light emitting diode unit 100.

The light emitting diode control unit 20 includes a memory 21, and data for stepwise brightness control according to the determined operation characteristics is stored.

The voltage converting unit 30 converts the driving voltage of the analog state output from the light emitting diode control unit 20 into a voltage of a size suitable for the specification of the light emitting diode unit 100 (for example, by decreasing the driving voltage) And outputs the voltage to the light emitting diode unit 100 so that the light emitting diode unit 100 can be turned on and off.

The current sensing unit 40 converts the current flowing through the LED unit 100 into a voltage of a corresponding magnitude and outputs the voltage to the LED controller 20.

The light emitting diode control unit 20 feeds back the operation state of the light emitting diode unit 100 using the voltage output from the current sensing unit 40 to determine the operation characteristics of the light emitting diode unit 100. [ The operation of the LED driving apparatus according to an embodiment of the present invention will be described.

First, referring to FIG. 2, operation characteristics of a light emitting diode will be described.

A light emitting diode is a semiconductor device using a p-n junction, and is a light emitting device that generates light when a current flows in a forward direction to a p-n junction.

As shown in FIG. 2, the light emitting diode operates according to a driving voltage output from the light emitting diode control unit to output a current of a corresponding magnitude (i.e., an output current).

As shown in FIG. 2, as the driving voltage increases, the magnitude of the output current also increases. When a driving voltage of greater than the threshold voltage Vth is supplied, the amount of the output current flowing through the LED dramatically increases.

Referring to the graph G11 of FIG. 2, when the driving voltage is higher than V1, a current starts to flow through the light emitting diode, and the light emitting diode starts to emit light. At this time, the current flowing through the light emitting diode is 'I1' .

However, when the driving voltage gradually increases to be equal to or higher than the threshold voltage 'V2', the amount of current flowing through the light emitting diode increases largely as compared to when the driving voltage before the threshold voltage V2 is applied.

Accordingly, the amount of current change of the output current according to the amount of change of the driving voltage increases, and the graph of the change of the output current according to the driving voltage of FIG. 2 shows that the first slope before the threshold voltage V2 and the second slope after the threshold voltage V2 And the second slope has a value greater than the first slope.

In the graph G11 of FIG. 2, 'I2' is the current flowing through the light emitting diode when the threshold voltage V2 is applied, 'I3' is the maximum output current output from the light emitting diode according to the characteristics of the light emitting diode, When the maximum output current is outputted, the driving voltage supplied becomes the maximum driving voltage 'V3'.

The output currents I1-I3 are output from the light emitting diode unit 100 of the present embodiment and output to the current sensing unit (not shown) 40).

Therefore, even if the driving current is changed by the same amount to control the brightness of the light emitting diode unit 100 step by step, the amount of brightness change, especially the amount of brightness change near the threshold voltage Vth, is not constant.

In addition, even if the same driving voltage is applied depending on the magnitude of the resistance such as wiring resistance, the operation state of the light emitting diode changes according to the operation characteristics, and thus the magnitude of the current flowing through the light emitting diode changes.

For example, as the wiring resistance increases, the light emitting efficiency of the light emitting diode decreases. As shown in FIG. 2, as the wiring resistance increases, the characteristic graph of the light emitting diode shifts to the right direction. That is, as the wiring resistance increases, the magnitude of the driving voltage supplied to obtain an output current of the same magnitude increases.

Therefore, referring to FIG. 2, since the light emitting diode having the characteristic of the graph G12 is affected by the wiring resistance larger than the light emitting diode having the operating characteristic of the graph G11, in the case of the graph G11, In order to obtain the currents I1, I2 and I3 respectively, the magnitudes of the drive voltages outputted from the LED controller are V1, V2 and V3, respectively. In the case of the graph G12, however, the voltages V1, V2 and V3 V4, V5, and V6, respectively, to obtain desired output currents I1, I2, and I3.

Therefore, in the present embodiment, the driving state of the light emitting diode unit 100 is changed according to not only the operation characteristics of the light emitting diode but also the wiring resistance (i.e., the length of the wiring and the thickness of the wiring) The brightness of the light emitting diode unit 100 is controlled to be constant by the brightness control switch 10 regardless of the magnitude of the wiring resistance.

Next, an operation of the LED controller 100 according to an embodiment of the present invention will be described with reference to FIGS. 3 to 6. FIG.

First, the power required for the operation of the LED driving apparatus is supplied. When the operation of the LED control unit 20 starts (S10), the LED control unit 20 first increases the voltage of the voltage conversion unit 30 from 0V The maximum value of the output current Imax which is the maximum value of the output current Iout of the predetermined magnitude is outputted as the light emission current Imax of the light emitting diode control unit 20 to the voltage converting unit 30 The magnitude of the drive voltage Vd is sequentially increased until output from the diode unit 100 to determine the operation characteristics of the light emitting diode unit 100 in which the resistance of the wirings L1 and L2 is reflected.

The voltage converting unit 30 converts the driving voltage Vd output from the light emitting diode control unit 20 and supplies the operating voltage of a corresponding magnitude based on the driving voltage Vd to the light emitting diode unit 100).

The operation state of the light emitting diode unit 100 changes according to an applied operating voltage. As described above with reference to FIG. 2, the timing at which the initial current is output depends on the magnitude of the wiring resistance.

Accordingly, when the light emitting diode unit 100 operates according to the operating characteristics and the wiring resistance of the light emitting diode unit 100 and the current flows, the light emitting diode unit 100 is turned on and corresponds to the applied driving voltage Vd The current Iout of the corresponding magnitude is output to the current sensing unit 40. [

Accordingly, the current sensing unit 40 senses the output current Iout output from the light emitting diode unit 100, and outputs the digital state voltage corresponding to the magnitude of the sensed current to the LED controller 20.

The light emitting diode control unit 20 reads the current sensing voltage output from the current sensing unit 40 and determines the magnitude of the current Iout output from the light emitting diode unit 100 S12).

The maximum driving voltage Vmax which is the maximum value of the driving voltage Vd output from the light emitting diode control unit 20 to the voltage converting unit 30 is determined according to the operation characteristics of the light emitting diode included in the light emitting diode unit 100 It can be different. For example, when the maximum output current Imax, which is the maximum value of the output current Iout outputted from the light emitting diode, is set to 9 A according to the operation characteristics of the light emitting diode, when the output current Iout of 9 A is outputted, The driving voltage Vd becomes the maximum driving voltage Vmax.

As described above, the light emitting diode control unit 20 outputs the driving current Imax to the driving voltage Vmax from 0 V to the maximum driving voltage Vmax until the desired maximum output current Imax is outputted, The output current Iout corresponding to the magnitude of the voltage Vd is determined.

5, when a characteristic graph (hereinafter referred to as an 'actual characteristic graph') G3 of the light emitting diode section 100, which is a graph of a change in the output current Iout with respect to the driving voltage Vd, The diode control unit 20 determines that the driving voltage (e.g., the minimum driving voltage) when the output current Iout starts to be outputted first through the light emitting diode unit 100 is 'V11' It is found that the driving voltage when the flow suddenly changes, that is, the threshold voltage is 'V21' and the maximum driving voltage Vmax which is the driving voltage when 'I31' which is the maximum output current Imax is outputted is 'V31'.

At this time, the light emitting diode control unit 20 is a branch point of the first portion G31 having the first slope and the second portion G32 having the second slope larger than the first slope in the actual characteristic graph G3 of Fig. 5 The threshold voltage V21 is determined as the drive voltage at the time point when the slope change of the actual characteristic curve G3 changes to a value greater than the set value. Also in the actual characteristic graph G2 shown in Fig. 4, the threshold voltage V221 is a driving voltage at a time point when the slope change of the actual characteristic graph G2 is changed to a set value or more.

As a result, the light emitting diode control unit 20 outputs the driving voltage Vd from 0 V to Vmax and reads the current sensing voltage corresponding thereto to determine the output current Iout output from the light emitting diode unit 100, The light emitting diode control unit 20 obtains the actual characteristic graphs G2 and G3 of the light emitting diode unit 100 as shown in FIGS. 4 and 5 (S13), thereby obtaining the respective driving voltages V211, V221, V231 and V11 , V21 and V31 and the values of the output currents I211, I221, I231, I11, I21 and I31 corresponding thereto are determined.

The actual characteristic graphs G2 and G3 are shifted to the left or the right depending on the magnitude of the wiring resistance so that the actuality of the light emitting diode unit 100 obtained by the light emitting diode control unit 20 The characteristic graphs (G2, G3) are characteristic graphs in which the value of wiring resistance is already reflected.

When the actual characteristic graph of the light emitting diode unit 100 in which the magnitude of the wiring resistance is reflected is obtained, the light emitting diode control unit 20 controls the brightness control switch 10 The driving voltage for each brightness control stage is calculated (S14).

First, an example of a method of calculating the driving voltage for each brightness control end of the brightness control switch 10 will be described with reference to FIG.

As described above, since the amount of current change according to the amount of change in voltage is greatly changed based on the threshold voltage (Vth), the light emitting diode is driven with the driving voltage (Vss) corresponding to the brightness control end of the brightness control switch And the like.

At this time, in order to improve the uniformity of the brightness variation amount of the light emitting diode unit 100 which changes for each brightness control stage of the brightness control switch 10, the light emitting diode control unit 20 calculates the threshold voltage Vth in the actual characteristic curve G2, Each of the sections D1 and D2 of the horizontal axis (i.e., pre-drive compression) divided by the vertical axis of the actual characteristic curve G2 is divided into a plurality of division steps based on the vertical axis (i.e., the output current axis) of the actual characteristic curve G2.

The second period D2 is a period having a driving voltage greater than the threshold voltage V221 and the threshold voltage V221 is a period having a driving voltage smaller than the threshold voltage V221, And may be included in both the first section D1 and the second section D2.

The light emitting diode control unit 20 calculates the interval between the minimum current I211 and the maximum output current Imax = V231 of the output current outputted from the light emitting diode unit 100 in the already calculated actual characteristic curve G2, (Hereinafter, referred to as a threshold current) I221 corresponding to a drive voltage V221 determined as a voltage Vth is divided into a first current section VD1 and a second current section VD2 The first current section VD1 is a section for outputting a current smaller than the threshold current I221 and the second current section VD1 is a section for outputting a current larger than the threshold current I221. I221 may be included both in the first section VD1 and the second section VD2.

The light emitting diode control unit 20 then calculates the magnitude I221-I211 of the first current section VD1 using the output currents I211 and I221 and outputs the magnitude I221 to I211 of the second current section I221 to I231 using the output currents I221 and I231. The magnitude ratio between the first current section VD1 and the second current section VD2 is calculated by calculating the magnitude I231-I221 of the current section VD2.

Next, the light emitting diode control unit 20 divides the total number of division steps already determined according to the ratio of magnitudes of the first and second current sections VD1 and VD2, and divides the number of division steps for the first current section VD1 , The number of first divisional steps) and the number of division steps (e.g., the number of second divisional steps) for the second current section VD2.

The light emitting diode control unit 20 then outputs the first and second sections D1 and D2 of the horizontal axis corresponding to the second and second current sections VD1 and VD2 to the current sections VD1 and VD2 The number of division steps.

Therefore, the first section D1 of the horizontal axis is divided according to the number of first division steps, and the second section D2 of the horizontal axis is divided according to the number of the second division steps, and the first section D1 and the second section D1, (D2). ≪ / RTI >

The first and second sections D1 and D2 are sections of a plurality of pre-drive compression sections divided about the threshold voltage of the actual characteristic graph.

At this time, the total number of division steps is determined based on the number of brightness control stages of the brightness control switch 10, and in some cases, the number of brightness control stages of the brightness control switch 10 is greater than 1 .

Therefore, for example, when the number of brightness control stages of the brightness control switch 10 is 30 and the magnitude ratio of the first and second current sections VD1 and VD2 is 1: 2, D1 is 10, and the number of division steps of the second section D2 is 20.

At this time, the dividing intervals in the first section D1 are the same, the dividing intervals in the second section D2 are the same, and the dividing intervals of the first section D1 and the second section D2 are Can be different.

Therefore, the interval (i.e., voltage) between the adjacent divisional steps in the first section D1 is calculated by dividing the size of the first section [D1 = V21-V11] by the number of division steps (I.e., the first voltage change amount) in the second period D2 and the interval (i.e., voltage) between the adjacent stages in the second period D2 corresponds to the number of division steps (for example, 20 (For example, the second voltage change amount).

As described above, the division step of the pre-drive compression is divided according to the ratio of the magnitudes of the first current section VD1 and the second current section VD2 divided on the basis of the threshold voltage V21, and the voltage change amount between adjacent division steps is calculated The drive voltage Vd for each brightness control end of the brightness control switch 10 is calculated and stored in the memory 21 of the light emitting diode control unit 20. [

Accordingly, the light emitting diode control unit 20 matches the brightness control stage of the brightness control switch 10 to each divided stage of the pre-drive compression, and the corresponding drive voltage value of each pre- The driving voltage of the corresponding brightness control stage of FIG.

For example, in FIG. 4, the division step HD1 of the pre-drive compression corresponds to the first brightness control stage of the brightness control switch 10, and the driving voltage V211 corresponding to the division step HD1 is brightness And becomes the driving voltage Vd corresponding to the first brightness control stage of the control switch 10. [

Similarly, the division step HD11 of the pre-drive compression corresponds to the eleventh brightness control stage of the brightness control switch 10 and the driving voltage 'V221' corresponding to the dividing stage HD11 corresponds to the brightness control switch 10, And the driving voltage Vd corresponding to the eleventh brightness control stage of the driving circuit.

As described above, the first section D1 and the second section D2 of the pre-drive compression having different slopes are set on the basis of the ratio of the magnitudes of the first current section VD1 and the second current section VD2 of the output current axis And the amount of change in the drive voltage Vd in the first section D1 and the amount of change in the drive voltage Vd in the second section D2 are adjusted so that the drive between the brightness control stages of the brightness control switch 10 The amount of change of the voltage is determined.

The magnitude of the driving voltage Vd corresponding to each brightness control end of the brightness control switch 10 is determined based on a constant change amount of the output current Iout so that the uniformity of the brightness change amount of the light emitting diode unit 100 Is improved.

At this time, since the drive voltage Vd for each erection control end of the brightness control switch 10 is calculated based on the actual characteristic graph G2 in which the resistances of the wirings L1 and L2 are taken into consideration, The brightness uniformity of the bright light diode unit 100 is improved.

In the case of FIG. 4, since the current periods VD1 and VD2 are divided based on the threshold voltage Vth, the current periods VD1 and VD2 are 'N + 1' when the number of threshold voltages Vth is 'N' (Where N is a positive integer).

Next, another example of a method of calculating the driving voltage for each brightness control end of the brightness control switch 10 will be described with reference to Figs. 5 and 6. Fig.

The graph shown in Fig. 5 shows the actual characteristic graph G3 of the light emitting diode unit 100 in which the magnitude of the wiring resistance is reflected by the operation of the light emitting diode control unit 20 (steps S11 to S13) )to be.

Therefore, in the actual characteristic graph G3, the minimum current point (i.e., the portion having the coordinates of (V11, I11)), which is the point at which the current starts to flow first in the light emitting diode unit 100, (The portion having the coordinates of (V31, I31)) that outputs the maximum output current Imax to the maximum output current Imax of the virtual characteristic graph VG3, And controls the driving voltage Vd applied to the light emitting diode unit 100 according to the graph VG3. At this time, the virtual characteristic graph VG3 is a graph of an ideal output current Iout substantially corresponding to the change of the driving voltage Vd, and is an ideal brightness variation graph of the light emitting diode unit 100.

Therefore, the light emitting diode control unit 20 divides the two portions G31 and G32 of the actual characteristic graph G3 into the driving voltage Vd for each brightness control end of the brightness control switch 10 based on the virtual characteristic graph VG3 And the like.

Therefore, the light emitting diode control unit 20 sets each of the sections D11 and D12 of the horizontal axis (i.e., pre-drive compression) with respect to the two portions G31 and G32 of the actual characteristic curve G3 based on the virtual characteristic graph VG3 Divided into a plurality of division steps, and a driving voltage Vd of a corresponding size is outputted in accordance with each divided division step.

To this end, the light emitting diode control unit 20 uses the tilt change point (i.e., the portion having the coordinates of (V21, I21)), which is a point when the virtual characteristic graph VG3 and the threshold voltage V21 are outputted, , The virtual characteristic graph VG3 is divided into a plurality of parts, for example, two parts VG31 and VG32.

As shown in FIGS. 5 and 6, the first portion VG31 and the second portion VG2 are centered around a point B at which a straight line connected to at least one tilt change point A is perpendicular to the virtual characteristic graph VG3, The first portion VG31 is a portion located downward around the point B and the second portion VG32 is a portion located upwardly about the point B, At this time, the point B may be included both in the first portion VG31 and the second portion VG32.

The light emitting diode control unit 20 then controls the brightness of the light emitting diode unit 100 based on the respective portions VG31 and VG32 of the virtual characteristic graph VG3 so as to control the brightness of each of the portions VG31 and VG32 The number of division steps (for example, the number of first and second division steps) is calculated by using the length ratio of the two parts (VG31 and VG32).

For example, since the total number of division steps for the total linear length of the virtual characteristic graph VG3 is already set, the total number of division steps thus set is divided according to the length ratio of the two parts VG11 and VG32, The number of first and second division steps is determined by the number of division steps of the respective parts (VG31, VG32).

For example, when the total number of division steps is '1000' and the length ratio of the two parts (VG31 and VG32) is 1: 9, the number of first division steps allocated to the first part (VG31) becomes '100' The number of the second division steps allocated to the second portion VG32 becomes '900'.

As described above, the total number of division steps is determined based on the number of brightness control stages of the brightness control switch 10. In some cases, the number of brightness control stages of the brightness control switch 10 is set to 1 'Can be many.

At this time, the intervals (i.e., the dividing intervals) between the adjacent dividing steps in each portion (VG31 or VG32) are constant, but the intervals between adjacent dividing steps in the different portions VG31 and VG32 may be different from each other.

As described above, when the number of division steps for the plurality of portions VG31 and VG32 of the virtual characteristic graph VG3 is calculated, the interval of the horizontal axis (i.e., pre-drive compression) with respect to the first portion G31 in the actual characteristic graph G3 (For example, the first section) D11 is uniformly divided into the calculated number of division steps of the first section VG31 and the section of the horizontal axis relative to the second section G32 in the actual characteristic graph G3 Dividing the number of division steps for the first and second parts G31 and G32 of the actual characteristic graph G3 by dividing the number of divisions D12 into the number of divisions of the calculated second portion VG32.

In this example, the first and second sections D11 and D12 are the sections of the plurality of pre-drive compression sections that are divided around the threshold voltage of the actual characteristic graph, and the first section D11 is set to be smaller than the threshold voltage V21 And the second period D12 is a period having a driving voltage greater than the threshold voltage V21 and the threshold voltage V21 is a period having the first period D11 and the second period D12. It can be included in all.

In this case, the interval (i.e., voltage) of the dividing step in the first section D11 is a value obtained by dividing the magnitude of the first section [D11 = V21-V11] by the number of dividing steps (e.g., And the interval (i.e., voltage) of the dividing step in the second section D12 is a value (for example, a second voltage variation) calculated by dividing the size of the second section [D12 = V31-V21] do. The first voltage change amount and the second voltage change amount may be different from each other.

If the number of divisions of the first and second sections D11 and D12 is determined based on the virtual characteristic graph VG3 as described above, the light emitting diode control section 20, as already described with reference to Fig. 4, Is matched to the brightness control end of the brightness control switch 10, and the drive voltage Vd corresponding to each brightness control end is calculated and stored in the memory 21.

At this time, the voltage change amount between the adjacent brightness control ends in the first section D11 becomes the first voltage change amount, and the voltage change amount between the adjacent brightness control ends in the second section D12 becomes the second voltage change amount.

Accordingly, when the brightness control stage determined by the brightness control signal output from the brightness control switch 10 is the first brightness control mode, the light emitting diode control unit 20 controls the voltage V11 to correspond to the first brightness control stage And outputs the driving voltage Vd to the voltage conversion unit 30. When the operation state of the brightness control switch 10 is the 1001 brightness control, The voltage Vd is V31.

The light emitting diode control unit 20 first determines the characteristic graph of the light emitting diode unit 100 in which the wiring resistance is reflected, and then, using the virtual characteristic graph of the determined characteristic graph, The brightness variation amount uniformity of the light emitting diode unit 100 is improved according to the brightness control stage change of the brightness control switch 10 regardless of the wiring resistance .

5 and 6, the slope change point at which the amount of change of the output current Iout with respect to the drive voltage Vd changes to the set value or more is '(V21, I21)', The portion of the virtual characteristic graph VG3 divided by the reference is the two portions VG31 and VG32.

However, when there are two slope change points, the virtual characteristic graph is divided based on each of these two portions. In this case, the virtual characteristic graph is divided into three portions.

In this way, when the number of gradient change points is N, the virtual characteristic graph is divided into N + 1 (where N is a positive integer).

Next, referring to FIG. 5, an example of a method of calculating the length ratio for the divided two parts (VG31, VG32) with respect to the entire straight line length of the virtual characteristic graph VG3 will be described in more detail.

First, the light emitting diode control unit 20 controls the light emitting diode control unit 20 such that the light emitting diode control unit 20 receives the base line a in the triangle S1 formed by the intersection of the minimum current point A11, the maximum current point A12 and the maximum lateral axis voltage V31, The angle? 1 formed by the hypotenuse c and the length of the hypotenuse c are calculated.

At this time, the length of the base line (a) is calculated by (V31-V11), and the height (b) is calculated by (I31-I11).

Therefore, the length of the hypotenuse (c) of the triangle S1 is calculated using the pythagorean theorem and the angle (θ1) between the base (a) and the hypotenuse (c) is calculated by the trigonometric formula.

Then, the light emitting diode control unit 20 uses the base line a11 and the height b11 in the triangle S2 having the base line a11, the height b11 and the hypotenuse c11 to calculate the base line a11 and the hypotenuse c11 2) is calculated.

That is, since the base line a11 is calculated by (V21-V11) and the height b11 is calculated by (I21-I11), the length of the hypotenuse c11 is also calculated, and the formula of the trigonometric function using the two sides is The angle [theta] 2 is also calculated,

Therefore, the angle? 3 formed by the base line a12 and the hypotenuse c11 in the triangle S3 having the base line a12 and the hypotenuse c11 is calculated. That is,? 3 =? 1 -? 2.

Since the angle? 3 formed by the hypotenuse c11 and the base line a12 is known and the length of the hypotenuse c11 is known, the length of the base line a12 is calculated by the formula of the trigonometric function.

Therefore, the length of the base line a12 is a linear length of the first portion VG31 of the virtual characteristic graph VG3, and the linear length a13 of the second portion VG32 is the length of the hypotenuse of the calculated triangle S1 (a13 = c-a12) obtained by subtracting the straight line length a12 of the first portion VG31 calculated from the length of the first portion (c).

As described above, when the linear distances a12 and a13 of the first portion VG31 and the second portion VG32 of the virtual characteristic graph VG3 are calculated using the trigonometric function and the Pythagorean definition, the distance ratios of the portions VG31 and VG32 with respect to the area (c) are calculated.

Then, as already described, since the total number of division steps (for example, 1,000) for the total linear distance c has already been determined, the total number of division steps is divided according to the ratio of the distances of the respective portions VG31 and VG32, And determines the number of division steps allocated to the portions VG31 and VG32.

Next, the light emitting diode control unit 20 sets the number of division steps allocated to the first portion VG31 of the virtual characteristic graph VG3 to the first section D11 corresponding to the first section G31 of the actual characteristic graph G3 And the second section D12 corresponding to the second section G32 of the actual characteristic graph G3 is divided by the number of division steps allocated to the second section VG32 of the virtual characteristic graph VG3 The number of steps for dividing the driving voltage Vd for the first and second portions G31 and G32 of the actual characteristic graph G3 and the voltage variation amount 2 voltage change amount) is calculated.

As described above, when the drive voltage Vd corresponding to each brightness control end of the light emission control switch 10 is calculated according to the example described with reference to Figs. 4 to 6, the brightness diode control unit 20, And outputs the driving voltage Vd corresponding to the brightness control stage.

Therefore, the light emitting diode control unit 20 reads the brightness control signal output from the brightness control switch 10 to determine a brightness control stage corresponding to the brightness control signal, and uses the data stored in the memory 21 to determine And outputs the driving voltage Vd corresponding to the brightness control stage to the voltage conversion unit 30. [

At this time, since the uniformity of the amount of change of the output current Iout is improved when moving to the adjacent brightness control stage, when the brightness control stage is sequentially changed by the operation of the brightness control switch 10, The user's discomfort due to the brightness change of the user is reduced.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It belongs to the scope of right.

10: Brightness control switch 20: Light emitting diode control unit
30: voltage conversion unit 40: current sensing unit
100: Light emitting diode section L1, L2: Wiring

Claims (10)

A current sensing unit sensing an output current outputted from a light emitting diode unit having at least one light emitting diode and outputting a corresponding sensing signal,
And a control unit for determining an actual characteristic graph of an output current with respect to a driving voltage of the light emitting diode unit using the sensing signal output from the current sensing unit, Dividing the number of division steps into a number of division steps for a plurality of divided pre-drive compression sections based on the determined threshold voltage of the actual characteristic graph, and dividing the plurality of pre-drive compression sections A light emitting diode control unit for calculating a driving voltage for each brightness control stage of the brightness control switch
And a light emitting diode driving device. The method of claim 1,
Wherein the total number of division steps is determined according to the total number of brightness control stages of the brightness control switch. A current sensing unit sensing an output current outputted from a light emitting diode unit having at least one light emitting diode and outputting a corresponding sensing signal,
A current characteristic graph for an output current with respect to a driving voltage of the light emitting diode portion is determined using the sensing signal output from the current sensing portion, and a plurality of portions divided around the tilt changing point in the determined actual characteristic graph The number of division steps for each of the divided sections is calculated on the basis of the virtual characteristic graph, and the number of division steps for each division step is calculated based on the threshold voltage of the actual characteristic graph, A light-emitting diode control section for dividing the number of the brightness control switches and calculating a drive voltage for each brightness control end of the brightness control switch,
Lt; / RTI >
The virtual characteristic graph is a graph obtained by using the minimum current point and the maximum current point of the actual characteristic graph
Emitting diodes. 4. The method of claim 3,
Wherein the tilt change point is a point where a change amount of the tilt in the actual characteristic graph is equal to or greater than a set value. The method according to claim 1 or 3,
Wherein the at least one light emitting diode outputs an output current of 5A to 50A. 4. The method of claim 3,
Wherein the light emitting diode control unit divides the virtual characteristic graph into a plurality of portions around a point at which the tilt change point and the virtual characteristic graph are perpendicular to each other and adjusts the virtual characteristic graph based on a ratio of a straight line distance to a plurality of portions of the virtual characteristic graph Dividing the total number of division steps for all the straight line distances of the virtual characteristic graph so as to determine the number of division steps respectively assigned to the plurality of portions of the virtual characteristic graph, and based on the number of division steps of the determined virtual characteristic graph And calculates the number of division steps for each section for each part of the actual characteristic graph. Outputting a driving voltage to the light emitting diode unit and calculating an actual characteristic graph using an output current outputted from the light emitting diode unit,
Dividing the output current axis of the actual characteristic graph into a plurality of current sections based on at least one threshold voltage,
Dividing the total number of division steps according to the size ratio of the divided plurality of current sections to determine the number of division steps for each of the plurality of current sections,
Dividing each of the plurality of pre-driving compression sections by setting the determined number of division steps to the number of division steps for a plurality of divided pre-driving compression sections based on at least one threshold voltage of the actual characteristic graph, And
Calculating a driving voltage for each brightness control stage of the brightness control switch based on the divided dividing step
Emitting diode. Outputting a driving voltage to the light emitting diode unit and calculating an actual characteristic graph using an output current outputted from the light emitting diode unit,
Calculating a virtual characteristic graph using a minimum current point and a maximum current point of the actual characteristic graph,
Dividing the virtual characteristic graph into a plurality of portions using at least one slope change point of the actual characteristic graph,
Dividing a segment of a plurality of segments centered around the at least one slope change point in the actual characteristic graph according to a length ratio of the plurality of segments of the virtual characteristic graph, Setting, and
Calculating a driving voltage for each brightness control stage of the brightness control switch based on the divided dividing step
Emitting diode. 9. The method of claim 8,
Wherein the at least one tilt change point is a point at which a change amount of the tilt in the actual characteristic graph is equal to or greater than a set value. 9. The method of claim 8,
Wherein the plurality of portions of the virtual characteristic graph are divided around a point where a straight line passing through the at least one tilt change point is perpendicular to the virtual characteristic graph.

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