Patent Application
20150137696
The present disclosure relates in general to the field of AC lighting systems, and in particular, to an AC direct step driver lighting system for providing uniform light distribution.
An alternating current (AC) lighting system refers to a system that directly drives a lighting load such as light emitting diode (LED), organic light emitting diode (OLED), or other light emitting devices or components using rectified AC line voltage from an AC power source. AC lighting systems eliminate the need of a power conversion unit from an AC power source to a direct current (DC) power source. Due to their simple design and less components, AC lighting systems provide a low-cost solution for residential or commercial applications receiving power directly from an AC power source.
Despite their cost advantages, implementation of advanced features such as dimming control, mood lights, and color variations in a conventional AC lighting system poses technical difficulties because the fluctuating AC line voltage. Furthermore, LED segments in a conventional AC lighting system are often driven in a sequential order, therefore light emitted from each LED segment is not uniform across a light fixture.
An AC lighting system for providing uniform light distribution is disclosed. According to one embodiment, the AC lighting system includes an AC driver and LED packages electrically connected to the AC driver. Each LED package includes a plurality of LED elements and is physically distributed over an illuminating surface of the AC lighting system. The AC driver has a first current sink that drives a first LED group and a second current sink that drives the first LED group and a second LED group. The first LED group includes at least one LED element from each of the LED packages, and the second LED group includes at least one LED element other that the first set of LED elements from each of the LED packages.
According to another embodiment, an AC lighting driver includes a voltage input for receiving AC power from an AC power source, and a plurality of current sinks. The first current sink is connected to and drives a first LED group, and the second current sink is connected to and drives a second LED group. The first LED group includes at least one LED element from each of the plurality of LED packages, and the second LED group includes at least one LED element other that the first set of LED elements from each of the plurality of LED packages.
The above and other preferred features, including various novel details of implementation and combination of events, will now be more particularly described with reference to the accompanying figures and pointed out in the claims. It will be understood that the particular systems and methods described herein are shown by way of illustration only and not as limitations. As will be understood by those skilled in the art, the principles and features described herein may be employed in various and numerous embodiments without departing from the scope of the present disclosure.
The accompanying drawings, which are included as part of the present specification, illustrate the presently preferred embodiment and together with the general description given above and the detailed description of the preferred embodiment given below serve to explain and teach the principles described herein.
The figures are not necessarily drawn to scale and elements of similar structures or functions are generally represented by like reference numerals for illustrative purposes throughout the figures. The figures are only intended to facilitate the description of the various embodiments described herein. The figures do not describe every aspect of the teachings disclosed herein and do not limit the scope of the claims.
An AC lighting system for providing uniform light distribution is disclosed. Each of the features and teachings disclosed herein can be utilized separately or in conjunction with other features and teachings to provide a method for providing an AC light system with a control unit for controlling power of an LED. Representative examples utilizing many of these additional features and teachings, both separately and in combination, are described in further detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the claims. Therefore, combinations of features disclosed in the following detailed description may not be necessary to practice the teachings in the broadest sense, and are instead taught merely to describe particularly representative examples of the present teachings.
In the following description, for purposes of explanation only, specific nomenclature is set forth to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that these specific details are not required to practice the present invention.
Some portions of the detailed descriptions that follow are presented in terms of algorithms and symbolic representations of operations on data bits within a computer memory. These algorithmic descriptions and representations are the means used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. An algorithm is here, and generally, conceived to be a self-consistent sequence of steps leading to a desired result. The steps are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like.
Moreover, the various features of the representative examples and the dependent claims may be combined in ways that are not specifically and explicitly enumerated in order to provide additional useful embodiments of the present teachings. It is also expressly noted that all value ranges or indications of groups of entities disclose every possible intermediate value or intermediate entity for the purpose of original disclosure, as well as for the purpose of restricting the claimed subject matter. It is also expressly noted that the dimensions and the shapes of the components shown in the figures are designed to help to understand how the present teachings are practiced, but not intended to limit the dimensions and the shapes shown in the examples.
The present disclosure relates to a system and method for providing uniform light distribution using an AC direct step driver. The AC lighting system refers to a system driving a lighting load such as LED, OLED, and other light emitting devices using rectified AC line voltage directly. The AC lighting system thus eliminates the needs of power conversion from AC to DC. According to various embodiments, the present system and method establishes uniform lighting distribution in AC direct step lighting system.
An AC lighting system for providing uniform light distribution is disclosed. According to one embodiment, the AC lighting system includes an AC driver and LED packages electrically connected to the AC driver. Each LED package includes a plurality of LED elements and is physically distributed over an illuminating surface of the AC lighting system. The AC driver has a first current sink that drives a first LED group and a second current sink that drives the first LED group and a second LED group. The first LED group includes at least one LED element from each of the LED packages, and the second LED group includes at least one LED element other that the first set of LED elements from each of the LED packages.
LED as used herein are a general term for many different kinds of LEDs, such as traditional LED, super-bright LED, high brightness LED, organic LED, etc. The LED driver 101 is configured to drive many different kinds of LEDs. The LED load 110 is electrically connected to the power source 105 and is in the form of a string of LEDs divided into three LED groups, 111-113. However, it should be apparent to those of ordinary skill in the art that the LED load 110 may contain any number of LED groups and LED elements (or LED dies) in each LED group, and may be divided into any suitable number of groups without deviating from the scope of the present subject matter. The LED elements in each LED group may be a combination of the same or different kind, such as different color. The LED load 110 can be connected in serial, parallel, or a mixture of both. In addition, one or more resistances may be included inside each LED group.
The LED driver 101 controls the LED current that flows through the LED load 110. According to one embodiment, the LED driver 101 is a direct AC step driver ACS0804 or ACS0904 by Altoran Chips and Systems of Santa Clara, Calif. The LED driver 101 integrates a plurality of high voltage current sinks 145a, 145b, and 145c. When the rectified voltage, Vrect, reaches a reference voltage Vf, the LED groups 111, 112, and 113 turn on gradually when the corresponding current sink 145 has a headroom. Each LED channel current sink increases up to a predefined current level for each current sink 145 and maintains its level until the following group's current sink reaches to its headroom. At any point in a time domain, there is at least one active LED group. When the active LED group is changed from one group to the adjacent group with a change in the rectified voltage, Vrect, new active group's current gradually increases while the existing active group's current gradually decreases. The mutual compensation between LED groups 111, 112, and 113 achieves a smooth LED current change preventing blinking or flickering.
The LED segments that are closely located on the PCB board are grouped together as an LED group and are connected in series. This configuration simplifies the layout of a PCB board on which the LED elements and wirings are implemented. This configuration also minimizes the cross wiring between the LED segments and groups as the neighboring LED segments and groups connected. However, the serial configuration of the LED groups and LED segments in an LED group may not achieve the best uniform light distribution. For example, LED groups 1, 2, and 3 are located along a line on a mounting surface and form a LED strip. The turning-on sequence may be LED groups 1, 2, and 3 and the turning-off sequence may be LED groups 3, 2, and 1. Although the turning on/off sequences may occur in a quick succession, it may momentarily illuminate one side of the LED strip while the other side is completely off or flicking.
In comparison with the AC lighting system 200 of
A commercially available LED package typically includes multiple LED elements. For example, three LED elements are contained in an LED package as shown in
Multiple LED elements are contained in one LED package. Since the same amount of current flows through each LED package, the same amount of light is lit across the AC lighting system as long as the LED packages are distributed uniformly in the AC lighting system 500. Even when each LED group turns on in sequence, uniform light distribution is achieved over the illuminating surface.
According to one embodiment, each one of the three LED elements from each LED package is connected in series to form three uniformly distributed LED groups. Each LED package has one or more LED elements in one or more rows. For example, each of the LED packages 521, 522, 523, 524, 525, and 526 has a single top (or first row), middle (a second row), and bottom (a third row) LED elements. The top LED elements from each of the LED packages 521, 522, 523, 524, 525, and 526 are connected to in series form the LED group 511. Similarly, the middle LED elements and bottom LED elements are connected to form the LED groups 512 and 513, respectively. It is apparent that an LED package contains any number of rows and each row has any number of LED elements without deviating from the scope of the present disclosure. The voltage input VIN from the LED driver 510 is applied to one terminal end of the LED group 511. The other terminal end of the LED group 511 is connected to the current sink LED 1 of the LED driver 501 that controls the current flowing through the LED group 511. The current sink LED1 of the LED driver 501 is also connected to a terminal end of the second LED group 512. Similarly, the current sink LED2 and LED3 control the current flowing through the LED groups 512 and 513, respectively.
The geometric arrangement of LED elements within an LED package may not be critical in achieving the light uniformity. Therefore, this exemplary geometric arrangement of LED elements in a top, middle, and bottom portion of an LED package may not be too much meaningful depending on the number, the arrangement and the orientation of the LED elements within an LED package. The present example shows that each LED package contains three LED elements arranged in a top, middle, and bottom portion. However, it is apparent that one of ordinary skill in the art would recognize that any number and form of LED elements may be contained in a single LED package without deviating from the scope of the present disclosure. The serial connection of the equal number of LED elements (e.g., one LED element) from each LED package would achieve desired uniform light distribution as long as each of the LED elements draws the same current.
The direct drive AC lighting system 600 serially connects one LED element from each LED package 621, 622, 623, 624, 625, and 626 to form the LED groups 611, 612, and 613. The outer LED elements from each LED package are serially connected to form the LED group 611. Similarly, the middle LED elements, and the inner LED elements from each LED package are serially connected to form the LED groups 611 and 612, respectively. Since each LED group encompasses the perimeter of the AC lighting system 600, light emitted from the AC lighting system 600 is uniformly lit. Depending on the current flowing through the LED groups, the light intensity may vary, but the uniformity of emitted light is maintained due to the uniform distribution of the LED elements in each LED group.
The present disclosure describes various embodiments of an AC direct step lighting system that provides uniform light distribution. The LED packages contained in the AC direct step LED lighting system may be disposed on the illuminating surface of the AC light system with the same or an arbitrary distance between each other to provide uniform light distribution. Each LED groups may be formed by connecting one or more LED terminal(s) in each LED package with the same or an arbitrary distance.
The above exemplary embodiments illustrate various embodiments of implementing an AC lighting system with a direct step LED driver for providing uniform light distribution. Various modifications and departures from the disclosed example embodiments will occur to those having ordinary skill in the art. The subject matter that is intended to be within the scope of the invention is set forth in the following claims.
This application claims the benefits of and priority to U.S. Provisional Application No. 61/906,615, filed on Nov. 20, 2013, entitled “AC Direct Step Driver Lighting System for Equal Light Distribution,” the disclosure of which is hereby incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61906615 | Nov 2013 | US |
