EP2605620B1

EP2605620B1 - LED driving apparatus and method of driving LED

Info

Publication number: EP2605620B1
Application number: EP12275020.1A
Authority: EP
Inventors: Kyu Tae Seo; Sung Cheol Kim; Ju Rae Kim
Original assignee: Samsung Electro Mechanics Co Ltd
Current assignee: Solum Co Ltd
Priority date: 2011-12-16
Filing date: 2012-03-02
Publication date: 2016-07-13
Anticipated expiration: 2032-03-02
Also published as: EP2605620A1; EP2605620B8; KR101328340B1; KR20130068751A

Description

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a LED driving apparatus and a method of driving an LED, capable of being applied to a driving system driven by a PWM scheme and able to appropriately set a reference current according to a driving voltage varied at the time of changing the LED when the reference current according to the driving voltage is previously set.

Description of the Related Art

Applications of light emitting diodes (LEDs) LEDhave been expanded such as uses in a display, a lighting device, and the like.
An LED module including a plurality of LEDs generally has driving power applied thereto through a DC-DC converter that converts DC power from a power supply device (for example, SMPS) into driving power.
Meanwhile in an LED lighting device using the LED module, a driver having voltage or current of the LED module fedback thereto performs a control operation to supply a constant voltage or constant current to the LED module.
According to an analog scheme of the related art, the LED driver needs to use a separately designed reference circuit at the outside so as to control voltage or current and is set to a predefined reference value to meet LED lighting device output conditions.
However, in the LED driver of the related art, there may be a need to change a design of the reference circuit when the output conditions of the LED lighting device are different, such that it may be difficult to use products commonly used together.
For example in developing an LED lighting device of 50W when there are (1) products having output specifications of a voltage of 50V and current 1A and (2) products having output conditions of a voltage of 25V and current 2A, different reference values are required according to the specifications of the output current such that a design of a circuit should be changed.
Types of LED lighting are gradually being increased as the LED lighting market is gradually expanded. Therefore, a need exists for a technology capable of appropriately controlling various types of LED lighting as well as a technology capable of being applied to various kinds of LED lighting devices while diversifying wattage and controlled voltage/current according to the usage of the LED lighting and an LED light source.
EP 1517588 A1 discloses a lighting method for connecting a lighting head, having one or more LEDs arranged in an optional pattern, to a power supply and lighting the one or more LEDs up by using a power supply having one rating irrespective of the different specifications of the lighting heads.
US 2010/039046 A1 discloses an LED reading light connected to a power supply unit, an LED light means for giving off light with a desired light intensity, and a coding component which is connected to at least one power supply connection.
EP 1517588 A1 and US 2010/039046 A1 both describe conventional LED driving apparatuses that "read" a label of an LED lamp. This brings about the technical problem of current setting for different types of LED lamps by using a single driving apparatus. One of the advantageous effect of the present invention is its ability to overcome the foregoing technical problem.

SUMMARY OF THE INVENTION

An aspect of the present invention provides an LED driving apparatus and a method of driving an LED, capable of being applied to a driving system driven by a PWM scheme and appropriately setting a reference current according to driving voltage varied at the time of changing the LED when the reference current according to the driving voltage is previously set, and being applied to various types of LEDs.
According to an aspect of the present invention, there is provided an LED driving apparatus including: a voltage detection unit detecting a driving voltage supplied from a driving unit for a light emitting unit having a plurality of LEDs; a current detection unit detecting a driving current flowing in the light emitting unit; and a control unit setting a reference current according to a detected voltage from the voltage detection unit and controlling the driving unit according to the reference current and the detected current from the current detection unit, wherein the control unit includes a reference current setting part setting a reference current corresponding to a level of the detected voltage from the voltage detection unit, an A/D converter converting the detected current from the current detection unit into a digital detected current; and a switching controller generating a gate signal according to an error between the reference current and the digital detected current and providing the generated gate signal to the driving unit, and wherein the reference current setting part includes an A/D converter converting the detected voltage from the voltage detection unit into the digital detected voltage; a memory storing a V/I lookup table in which a current level corresponding to each voltage level is preset; and a V/I converter retrieving the current corresponding to the level of the digital detected voltage from the A/D converter from the memory to set the retrieved current as the reference current.
The driving unit may be a DC-DC converter including a switch device operated in response to the gate signal.
The gate signal may be a PWM gate signal.
According to another aspect of the present invention, there is provided a method of driving an LED, comprising: detecting a detected voltage corresponding to a driving voltage provided from a driving unit for a light emitting unit having a plurality of LEDs; detecting a detected current corresponding to a driving current flowing in the light emitting unit; and setting a reference current according to the detected voltage and controlling the driving unit according to the reference current and the detected current, wherein the controlling of the driving unit includes setting the reference current corresponding to a level of the detected voltage; converting the detected current into a digital detected current and generating a gate signal according to an error between the reference current and the digital detected current and providing the generated gate signal to the driving unit, and wherein the setting of the reference current includes converting the detected voltage into the digital detected voltage and converting the digital detected voltage into a corresponding current and setting the converted current as the reference current by using a previously provided V/I lookup table.
The driving unit may be a DC-DC converter including a switch device operated in response to a PWM gate signal.
The gate signal may be the PWM gate signal.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a block diagram of an LED driving apparatus according to an embodiment of the present invention;
FIG. 2 is a diagram showing a variation example of a reference current setting part according to an embodiment of the present invention;
FIG. 3 is a diagram showing another variation example of the reference current setting part according to the embodiment of the present invention;
FIG. 4 is a diagram showing a variation example of a V/I lookup table of a memory according to the embodiment of the present invention;
FIG. 5 is a flow chart of a method of driving an LED according to another embodiment of the present
invention;
FIG. 6 is a flow chart of a light emission drive controlling process according to another embodiment of the present invention;
FIG. 7 is a diagram showing a variation example of a reference current setting process according to another embodiment of the present invention; and
FIG. 8 is a diagram showing another variation example of a reference current setting process according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings.
The present invention should not be limited to the embodiments set forth herein and the embodiments may be used to assist in understanding the technical idea of the present invention. Like reference numerals designate like components having substantially the same constitution and function in the drawings of the present invention.
FIG. 1 is a block diagram of an LED driving apparatus according to an embodiment of the present invention.
Referring to FIG. 1, an LED driving apparatus according to an embodiment of the present invention may include a voltage detection unit 100 detecting a driving voltage Vdrv supplied from a driving unit 10 for a light emitting unit 20 having a plurality of LEDs, a current detection unit 200 detecting a driving current Idrv flowing in the light emitting unit 20, and a control unit 300 setting a reference current Iref according to detected voltage Vd from the voltage detection unit 100 and controlling the driving unit 10 according to the reference current Iref and the detected current Id from the current detection unit 200.
In this configuration, the driving unit 10 may convert an input voltage Vin into a predetermined voltage to provide the driving voltage Vdrv to the light emitting unit 20. In this case, the light emitting unit 20 may include at least one of channels in which the plurality of LEDs are connected with one another in series.
In this case, the voltage detection unit 100 may detect the driving voltage Vdrv supplied from the driving unit 10 of the light emitting unit 20 having the plurality of LEDs and provide the detected driving voltage Vdrv to the control unit 300.
The current detection unit 200 may detect the driving current Idrv flowing in the light emitting unit 20 and provide the detected driving current Idrv to the control unit 300.
Further, the control unit 300 may set the reference current Iref according to the detected voltage Vd from the voltage detection unit 100 and may control the driving unit 10 according to the reference current Iref and the detected current Id from the current detection unit 200.
As an example, the control unit 300 may include a reference current setting part 310 setting the reference current Iref corresponding to a level of the detected voltage Vd from the voltage detection unit 100, an A/D converter 320 converting the detected current Id from the current detection unit 200 into a digital detected current Ida, and a switching controller 330 generating a gate signal SG according to an error between the reference current Iref and the digital detected current Ida and providing the generated gate signal SG to the driving unit 10.
In this case, the reference current setting part 310 may set the reference current Iref corresponding to the level of the detected voltage Vd from the voltage detection unit 100.
The A/D converter 320 may convert the detected current Id from the current detection unit 200 into the digital detected current Ida.
Further, the switching controller 330 may generate a gate signal SG according to the error between the reference current Iref and the digital detected current Ida and provide the generated gate signal SG to the driving unit 10, thereby controlling the driving unit 10.
Meanwhile, the driving unit 10 may include a DC-DC converter including a switch device operated in response to the gate signal SG. In this case, the gate signal SG may be a PWM gate signal that undergoes pulse width modulation.
That is, the DC-DC converter may convert the input voltage Vin into a predetermined voltage according to the PWM gate signal from the control unit 300.
FIG. 2 is a diagram showing a variation example of a reference current setting part according to an embodiment of the present invention.
Referring to FIGS. 1 and 2, the reference current setting part 310 may include an A/D converter 311 converting the detected voltage Vd from the voltage detection unit 100 into the digital detected voltage Vda, and an V/I converter 313 converting the digital detected voltage Vda from the A/D converter 311 into a corresponding current and providing the converted current as the reference current Iref.
In this case, the A/D converter 311 may convert the detected voltage Vd from the voltage detection unit 100 into the digital detected voltage Vda and provide the converted detected voltage Vda to the V/I converter 313.
Further, the V/I converter 313 may convert the digital detected voltage Vda from the A/D converter 311 into a current corresponding to the level thereof and provide the converted current as the reference current Iref.
FIG. 3 is a diagram showing another variation example of the reference current setting part according to the embodiment of the present invention.
Referring to FIGS. 1 and 3, the reference current setting part 310 may include the A/D converter 311 converting the detected voltage Vd from the voltage detection unit 100 into the digital detected voltage Vda, a memory 312 storing a V/I lookup table of which a current level corresponding to each voltage level is preset, and a V/I converter 313 setting the digital detected voltage Vda from the A/D converter 311 as the reference current by retrieving the current corresponding to the level from the memory 312.
In this case, the A/D converter 311 may convert the detected voltage Vd from the voltage detection unit 100 into the digital detected voltage Vda and provide the converted detected voltage Vda to the V/I converter 313.
The memory 312 may store the V/I lookup table in which the current level corresponding to each voltage level is preset, thereby providing the current level corresponding to the voltage level.
Further, the V/I converter 313 may convert the digital detected voltage Vda from the A/D converter 311 as the reference current Iref by retrieving the current corresponding to the level from the memory 312.
FIG. 4 is a diagram showing a variation example of a V/I lookup table of a memory according to the embodiment of the present invention.
Referring to FIG. 4, the V/I lookup table stored in the memory 312 may include reference currents Vref stored therein which are respectively and differently preset according to the level of the digital detected voltage Vda.
For example, in a case in which desired required output is 25 W, when the digital detected voltage Vda is 25V, the reference current Vref may be set to be 1A, when the digital detected voltage is 50V, the reference current Vref may be set to be 500 mA, and when the digital detected voltage Vda is 100V, the reference current Vref may be set to be 250 mA.
FIG. 5 is a flow chart of a method of driving an LED according to another embodiment of the present invention.
Referring to FIGS. 1 and 5, the method of driving an LED according to another embodiment of the present invention may include detecting a detected voltage Vd corresponding to a driving voltage Vdrv supplied from the driving unit 10 for the light emitting unit 20 having a plurality of LEDs (S100), detecting a detected current Id corresponding to the driving current Idrv flowing in the light emitting unit 20 (S200), and setting a reference current Iref according to the detected voltage Vd and controlling the driving unit 10 according to the reference current Iref and the detected current Id (S300).
In this case, the detected voltage Vd corresponding to the driving voltage Vdrv supplied from the driving unit 10 of the light emitting unit 20 having the plurality of LEDs may be detected by the voltage detection unit 100 shown in FIG. 1 (S100).
In addition, the detected current Id corresponding to the driving current Idrv flowing in the light emitting unit 20 may be detected by the current detection unit 200 shown in FIG. 1 (S200).
Further, by the control unit 300 shown in FIG.1, the reference current Iref may be set according to the detected voltage Vd and the driving unit 10 may be controlled according to the reference current Iref and the detected current Id (S300).
Meanwhile, when the entire processing procedures have an end thereof during performing the process described above, the process may end, or otherwise, the above-mentioned process may be repeatedly performed (S400).
FIG. 6 is a flow chart of a light emission drive controlling process according to another embodiment of the present invention.
Referring to FIGS. 1 and 6, the controlling of the driving unit 10 (S300) may include setting the reference current Iref corresponding to the level of the detected voltage Vd
(S310), converting the detected current Id into the digital detected current Ida (S320), and generating a gate signal SG according to the errors between the reference current Iref and the digital detected current Ida and providing the generated gate signal SG to the driving unit 10 (S330).
In this case, the reference current Iref corresponding to the level of the detected voltage Vd may be set by the control unit 300 shown in FIG. 1 (S310). The detected current Id may be converted into the digital detected current Ida (S320).
Further, the gate signal SG according to the error between the reference current Iref and the digital detected current Ida may be generated and may be provided to the driving unit 10 (S330).
Meanwhile, as described above, the driving unit 10 may include a DC-DC converter including a switch device operated in response to the gate signal SG. In this case, the gate signal SG may be the PWM gate signal.
That is, the DC-DC converter may convert the input voltage Vin into the predetermined voltage according to the PWM gate signal from the control unit 300.
FIG. 7 is a diagram showing a variation example of a reference current setting process according to another embodiment of the present invention.
Referring to FIGS. 1 and 7, the setting of the reference current (S310) may include converting the detected voltage Vd from the voltage detection unit 100 into the digital detected voltage Vda and converting the digital detected voltage Vda into the corresponding current and providing the current as the reference current Iref (S312).
In this case, the detected voltage Vd from the voltage detection unit 100 may be converted into the digital detected voltage Vda by the control unit 300 shown in FIG. 1 (S311). Further, the digital detected voltage Vda may be converted into a corresponding current, which may be in turn provided as the reference current Iref (S312).
FIG. 8 is a diagram showing another variation example of a reference current setting process according to another embodiment of the present invention.
Referring to FIGS. 1 and 8, the setting of the reference current (S310) may include converting the detected voltage Vd into the digital detected voltage Vda (S311) and converting the digital detected voltage Vda into a corresponding current and setting the converted current as the reference current by using a previously provided V/I lookup table (S313).
In this case, the detected voltage Vd may be converted into the digital detected voltage Vda by the control unit 300 shown in FIG. 1 (S311). Further, the digital detected voltage Vda may be converted into a corresponding current, and then may be set as the reference current, by using the previously provided V/I lookup table (S313).
As set forth above, the embodiments of the present invention may be applied to the driving system driven by the PWM scheme, may appropriately set the reference current according to the driving voltage varied at the time of changing the LED when the reference current according to the driving voltage is previously set, and may be applied to various types of LEDs.
Further, according to the embodiments of the present invention, the circuits may be simplified by embedding the external circuits in the microcontroller and may be applied to several models without modifying the circuits by allowing the microcontroller to internally vary the reference current and to store several time constant values in the memory and to selectively use the time constant values, or the like.
While the present invention has been shown and described in connection with the embodiments, it will be apparent to those skilled in the art that modifications and variations may be made without departing from the scope of the invention as defined by the appended claims.

Claims

An LED driving apparatus, comprising:
a voltage detection unit (100) detecting a driving voltage supplied from a driving unit (10) for a light emitting unit (20) having a plurality of LEDs;

a current detection unit (200) detecting a driving current (Idrv) flowing in the light emitting unit (20); and

a control unit (300) setting a reference current (Iref) according to detected voltage (Vd) from the voltage detection unit (100) and controlling the driving unit (10) according to the reference current (Iref) and the detected current (Id) from the current detection unit (200),

wherein the control unit (300) includes,

a reference current setting part (310) setting a reference current (Iref) corresponding to a level of the detected voltage (Vd) from the voltage detection unit (100);

an A/D converter (320) converting the detected current (Vd) from the current detection unit (200) into a digital detected current (Ida); and

a switching controller (330) generating a gate signal (SG) according to an error between the reference current (Iref) and the digital detected current (Ida) and providing the generated gate signal (SG) to the driving unit (10), and

wherein the reference current setting part (310) includes,

an A/D converter (311) converting the detected voltage (Vd) from the voltage detection unit (100) into the digital detected voltage (Vda);

a memory (312) storing a V/I lookup table in which a current level corresponding to each voltage level is preset; and

a V/I converter (313) retrieving the current corresponding to the level of the digital detected voltage (Vda) from the A/D converter (311) from the memory to set the retrieved current as the reference current (Iref).
The apparatus of claim 1, wherein the driving unit (10) is a DC-DC converter including a switch device operated in response to the gate signal (SG).
The apparatus of claim 2, wherein the gate signal (SG) is a PWM gate signal.
A method of driving an LED, comprising:
detecting a detected voltage corresponding to a driving voltage provided from a driving unit for a light emitting unit having a plurality of LEDs (S100);

detecting a detected current corresponding to a driving current flowing in the light emitting unit (S200); and

setting a reference current according to the detected voltage and controlling the driving unit according to the reference current and the detected current (S300),

wherein the controlling of the driving unit includes

setting the reference current corresponding to a level of the detected voltage (S310);

converting the detected current into a digital deteched current (S320) and

generating a gate signal according to an error between the reference current and the digital detected current and providing the generated gate signal to the driving unit (S330), and

wherein the setting of the reference current includes

converting the detected voltage into the digital detected voltage (S311) and

converting the digital detected voltage into a corresponding current and setting the converted current as the reference current by using a previously provided V/I lookup table (S313).
The method of claim 4, wherein the driving unit is a DC-DC converter including a switch device operated in response to a PWM gate signal.
The method of claim 5, wherein the gate signal is the PWM gate signal.