News Column

Patent Application Titled "Light Emitting Diode Driving Device" Published Online

July 23, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- According to news reporting originating from Washington, D.C., by VerticalNews journalists, a patent application by the inventors HWANG, Jong Tae (Gyunggi-do, KR); CHA, Sang Hyun (Gyunggi-do, KR); LEE, Chang Seok (Gyunggi-do, KR); PARK, Deuk Hee (Gyunggi-do, KR), filed on May 1, 2013, was made available online on July 10, 2014.

The assignee for this patent application is Samsung Electro-mechanics Co., Ltd.

Reporters obtained the following quote from the background information supplied by the inventors: "The present invention relates to a light emitting diode driving device for directly driving light emitting diodes with alternating current (AC) power.

"Alight emitting diode (LED) is a semiconductor device having a p-n junction structure emitting light through electron-hole recombination, and has recently had applications in a number of fields, according to the development of semiconductor technology. Particularly, since LEDs have high degrees of efficiency, relatively long lifespans, and environmentally friendly properties as compared to various types of light emitting devices according to the related art, a field of application thereof is continuously being broadened.

"Generally, LEDs can be driven by applying several volts of direct current (DC) power thereto, in light of a structure thereof. Therefore, in order to drive LEDs using commercial alternating current (AC) power, a separate device element is required. In order to drive LEDs using commercial AC power, an LED driving device typically includes a rectifying circuit, an AC-DC converter, or the like.

"However, a general AC-DC converter has a relatively large volume and consumes significant amounts of power. Therefore, in the case in which a general AC-DC converter is applied to an LED driving device, advantages of LEDs, such as high-efficiency, small packaging size, long lifespan, and the like, are largely nullified.

"Therefore, research into an LED driving device capable of directly driving LEDs with AC power, without using an AC-DC converter, has recently been conducted.

"In the case of directly driving LEDs with AC power without using an AC-DC converter, a method in which a plurality of switches are connected to a plurality of LEDs, respectively, and switching on and switching off of the plurality of switches are controlled according to levels of AC power to allow current to flow continuously may be generally applied.

"Patent Document 1 relates to an LED driving device directly driving LEDs using AC power, by controlling operations of switches connected to an intermediate node and the last node of an LED array. Patent Document 2 also relates to an LED driving device capable of controlling switching on and switching off of switches based on an order of the switches to which an LED array is connected.

"Both Patent Documents 1 and 2 control the operations of the switches in order to drive LEDs; however, in the case in which the plurality of switches are driven, a number of switches may be turned on simultaneously, thereby causing difficulties in the driving of LEDs, and degrading power factor and total harmonic distortion (THD) characteristics."

In addition to obtaining background information on this patent application, VerticalNews editors also obtained the inventors' summary information for this patent application: "An aspect of the present invention provides a light emitting diode driving device capable of preventing a number of switches from being turned on simultaneously in the case in which a plurality of light emitting diodes are respectively driven using a plurality of switches.

"According to an aspect of the present invention, there is provided a light emitting diode driving device, including: a light emitting diode unit having a plurality of light emitting diodes connected to one another in series and emitting light through receiving rectified power; and a driving unit having a plurality of drivers driving the plurality of light emitting diodes of the light emitting diode unit, respectively, wherein each of the plurality of drivers selects a maximum voltage from among a plurality of detection voltages with respect to current flowing in at least one light emitting diode corresponding thereto and compares the maximum voltage with a preset reference voltage to thereby drive the corresponding light emitting diode.

"The preset reference voltage input to the plurality of drivers may be set to have different voltage levels.

"A voltage level of a reference voltage of a front end driver among the plurality of drivers may be set to be equal to or less than that of a reference voltage of a rear end driver adjacent thereto.

"Each of the plurality of drivers may detect the current flowing in the corresponding light emitting diode and divides the detected voltage to thereby form the plurality of detection voltages, and at least one of a plurality of detection voltages of a rear end driver among the plurality of drivers may be transferred to a front end driver adjacent thereto.

"Each of the plurality of drivers may include a comparator selecting the maximum voltage from among the plurality detection voltages to compare the selected voltage with the reference voltage; a switch switched on and switched off according to a comparison result of the comparator to allow current to flow in the corresponding light emitting diode; and a resistor group having a plurality of resistors connected to one another in series between the switch and a ground to detect the current flowing in the corresponding light emitting diode, and providing the plurality of detection voltages.

"The switch may be connected to a cathode of the corresponding light emitting diode.

"The comparator may include a level shifter group having a plurality of level shifters adjusting respective voltage levels of the plurality of detection voltages; a current source group having a plurality of current sources respectively supplying current according to the adjusting of the voltage levels by the level shifters; a maximum voltage detection unit detecting the maximum voltage from among the plurality of detection voltages level-adjusted from the level shifter group; a current mirror mirroring the maximum voltage detected by the maximum voltage detection unit; and an amplifying unit amplifying the mirrored voltage from the current mirror.

"Each of the plurality of drivers may form at least two detection voltages having different voltage levels, a detection voltage having a lower voltage level of the at least two detection voltages of the rear end driver among the plurality of drivers may be transferred to the front end driver adjacent to the rear end driver, and a detection voltage having a higher voltage level of the least two detection voltages may be transferred to a front end driver of the front end driver adjacent to the rear end driver.

"The light emitting diode driving device may further include a rectifying unit rectifying alternating current (AC) power to supply rectified AC power to the light emitting diode unit.

"According to another aspect of the present invention, there is provided a light emitting diode driving device, including: a light emitting diode unit having a plurality of light emitting diodes connected to one another in series and emitting light through receiving rectified power; and a driving unit having a plurality of drivers driving the plurality of light emitting diodes of the light emitting diode unit, respectively, wherein each of the plurality of drivers selects a maximum voltage from among a plurality of detection voltages with respect to current flowing in at least one light emitting diode corresponding thereto and compares the maximum voltage with a preset reference voltage to thereby drive the corresponding light emitting diode, the plurality of drivers include first to Nth drivers (N is a natural number of 2 or more), a first driver receives a first detection voltage having a low voltage level from a second driver and a second detection voltage having a high voltage level from third to Nth drivers, of the first and second detection voltages with respect to current flowing in at least one light emitting diode corresponding thereto, and compares a maximum voltage among the received detection voltages with a reference voltage to thereby drive the corresponding light emitting diode, second to N-2nd drivers receive a first detection voltage from a rear end driver, receive a second detection voltage from a rear end driver of the rear end driver, and compare a maximum voltage among the received detection voltages with a reference voltage to thereby drive light emitting diodes corresponding thereto, and a N-1st driver receives a first detection voltage from a Nth driver, and the Nth driver receives a sensing voltage from a sensing resistor detecting current flowing in light emitting diodes corresponding thereto to compare the received voltage with a reference voltage to thereby drive the corresponding light emitting diodes.

"Each of the plurality of drivers may include a comparator selecting the maximum voltage from among the plurality detection voltages to compare the selected voltage with the reference voltage; a switch switched on and switched off according to a comparison result of the comparator to allow current to flow in the corresponding light emitting diodes; and a resistor group having a plurality of resistors connected to one another in series between the switch and the sensing resistor to detect the current flowing in the corresponding light emitting diodes, and providing the plurality of detection voltages.

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 schematic configuration diagram of a light emitting diode driving device according to an embodiment of the present invention;

"FIG. 2 is a schematic circuit diagram of a driver employed in the light emitting diode driving device according to the embodiment of the present invention;

"FIG. 3 is a schematic circuit diagram of a comparator of the driver employed in the light emitting diode driving device according to the embodiment of the present invention;

"FIG. 4 is a schematic circuit diagram of the light emitting diode driving device according to the embodiment of the present invention; and

"FIGS. 5 through 7 are graphs showing electrical characteristics of the light emitting diode driving device according to the embodiment of the present invention."

For more information, see this patent application: HWANG, Jong Tae; CHA, Sang Hyun; LEE, Chang Seok; PARK, Deuk Hee. Light Emitting Diode Driving Device. Filed May 1, 2013 and posted July 10, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=5844&p=117&f=G&l=50&d=PG01&S1=20140703.PD.&OS=PD/20140703&RS=PD/20140703

Keywords for this news article include: Electronics, Semiconductor, Light-emitting Diode, Samsung Electro-mechanics Co. Ltd..

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Source: Electronics Newsweekly


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