Patent Description:
The present disclosure relates to Light-Emitting Diode (LED) apparatuses and systems, and in particular to a LED apparatus and system with power supply, and methods of controlling and powering the LEDs thereof.

Light-Emitting Diodes (LEDs) are known and have been widely used in industries, mostly as low-power light indicators. In recent years, LEDs with increased power output or increased luminous intensity have been developed and used for illumination. LED lights provide improved energy efficiency, safety, and reliability, and are replacing other types of lights in the market such as incandescent lights, Compact Fluorescent Lamps (CFLs), and the like. As everyday lighting significantly contributes to the burden on power grids and greatly increases the overall requirements for electricity generation, the energy efficiency of LEDs will play a crucial role in future energy savings. It is likely that LEDs will dominate the lighting markets because of their superior energy efficiency.

LEDs with increased power output or increased luminous intensity have also been used for image/video displays such as digital signage and the like. Digital LED signage is a fast-growing industry due to the increasing demand for marketing, advertising, and the like.

Prior-art digital LED signage displays utilize separate power conversion units along with LED drivers to provide electrical power to the LEDs from an external power source such as a power grid. While external power sources usually output alternate-current (AC) power, LEDs generally require direct-current (DC) power. Consequently, the power conversion unit of a digital LED signage requires both an AC-to-DC (AC/DC) converter and a DC-to-DC (DC/DC) converter to convert the AC input power from the external power source into DC power suitable for LEDs. Such converters, however, are usually bulky and heavy. Moreover, they usually produce significant amounts of heat and thus need suitable cooling means such as fans or large heat-sinks for heat dissipation. A well-designed thermal management system is essential to a power conversion unit for LEDs.

<FIG> shows an example of a prior-art LED signage display <NUM>. As shown, the LED signage display <NUM> comprises one or more LED display modules <NUM> having a plurality of LEDs for display, and a cabinet <NUM> for accommodating various electrical components of the LED signage display <NUM> such a power converter, a central controller, and the like. The LED display modules <NUM> are connected to the electrical components in the cabinet <NUM> via one or more cables (not shown). In this example, the LED display module <NUM> is physically coupled to the cabinet <NUM>. However, those skilled in the art will appreciate that, in some prior-art LED signage displays <NUM>, the LED display modules <NUM> may be physically separated from the cabinet <NUM>.

<FIG> is a schematic diagram of the commonly available LED signage <NUM>. As shown, the LED display module <NUM> of the LED signage <NUM> is electrically connected to a power converter <NUM> and a central controller <NUM> in the cabinet <NUM> via one or more cables 16A and 16B. In other words, the power converter <NUM> and a central controller <NUM> are physically separated from the LED display module <NUM> and are electrically connected thereto via the cables 16A and 16B.

The LED display module <NUM> comprises one or more LED drivers <NUM> driving a plurality of LEDs <NUM> which are usually arranged in a matrix form having one or more rows and one or more columns. Each LED <NUM> may be a single-color LED that only emits a single-color light such as a red, green, or blue light, or a multi-color LED such as a tri-color LED that can selectively emit multiple colored lights such as red, green, and blue lights. If single-color LEDs are used, the single-color LEDs may be grouped into one or more LED sets with each LED set comprising a red, green, and blue LEDs arranged in close proximity with each other, thereby forming a pixel of the LED display module <NUM>. On the other hand, if tri-color LEDs are used, each tri-color LED forms a pixel of the LED display module <NUM>.

The LED drivers <NUM> receive electrical power from the power converter <NUM> via one or more power wires or cables 16A for powering the LEDs <NUM>. The LED drivers <NUM> also receive control signals from the central controller <NUM> via one or more signal wires or cables 16B for regulating the power delivered to the LEDs <NUM>, thereby controlling the lighting of each LED <NUM> (for example, off, on, lighting intensity, color, and/or the like) for controlling the display of the LED signage <NUM>. Depending on the driving capacity of the LED drivers <NUM>, each LED driver <NUM> may be electrically connected to and may regulate a subset of the LEDs <NUM> for example <NUM>, <NUM>, or <NUM> LEDs <NUM>.

As described before, the power converter <NUM> is located in the cabinet <NUM>, and is physically separated from the LED display module <NUM> but electrically connected thereto via the electrical cables 16A and 16B. The power converter <NUM> comprises an AC/DC converter <NUM> and a DC/DC converter <NUM>. The AC/DC converter <NUM> converts the AC electrical power from an external power source <NUM> into high-voltage DC power and outputs the converted high-voltage DC power to the DC/DC converter <NUM>. The DC/DC converter <NUM> converts the high-voltage DC power received from the AC/DC converter <NUM> into low-voltage DC power (for example, at about 5V, <NUM>. 5V, or the like) suitable for powering the LEDs <NUM> in the LED display module <NUM>, and outputs the low-voltage DC power to the LED display module <NUM> via the cable 16A. Therefore, existing LED signage displays <NUM> have a low-voltage power distribution (for example, 5V) to their LED display modules <NUM>.

As described above, each LED driver <NUM> is electrically connected to the central controller <NUM> via the cable 16B. The central controller <NUM> is functionally connected to one or more computing devices <NUM> such as a desktop computer, a laptop computer, a smartphone, a tablet, a personal digital assistant (PDA), and the like, via suitable wired or wireless connection for receiving instructions therefrom. In response to the received instructions, the central controller <NUM> sends control signals to the LED drivers <NUM> to regulates the power delivered to the LEDs <NUM> of the LED display module <NUM>, thereby controlling the lighting (for example, off, on, the lighting intensity, color, and the like) of each LED <NUM> thereof for controlling the display of the LED signage <NUM>.

<FIG> is a circuit diagram showing an LED driver <NUM> driving a plurality of LEDs <NUM> in the LED display module <NUM>. For ease of illustration, <FIG> only shows three LEDs <NUM> emitting red, green, and blue lights, respectively, and forming a pixel of the LED display module <NUM>.

As shown, each LED <NUM> is electrically connected in series to a resister R and a switch <NUM> such as a semiconductor switch and, for example, a metal-oxide semiconductor field-effect transistor (MOSFET) switch. The LED driver <NUM> receives control signals from the central controller (not shown in <FIG>) via a wired data bus <NUM>, and individually controls each switch <NUM> via an electrical wire <NUM> to: (i) tum the respective LED <NUM> on and off, and (ii) control the luminous intensity thereof.

The LED driver <NUM> uses a Pulse-Width Modulation (PWM) scheme to turn the respective switch <NUM> on and off at a sufficiently high frequency for controlling the electrical current flowing through each LED <NUM>. In particular, the LED driver <NUM> adjusts the duty cycle of the pulse-width modulated current to control the luminous intensity of each LED <NUM> thereby controlling the luminous intensity thereof. By increasing the duration of the duty cycle, the duration of time that the switch <NUM> is turned on is increased and thus the current flowing therethrough becomes larger, thereby making the LED <NUM> brighter. By controlling the luminous intensity of the light emitted from each of the red, green, and blue LED <NUM> in a pixel in response to a set of control signals sent to the LED driver <NUM> via the data bus <NUM>, the color of the pixel may be dynamically adjusted for displaying an image on the LED display module <NUM>. <FIG> shows a prior-art LED driver <NUM> disclosed in <CIT>.

There are several challenges and difficulties associated with the prior-art digital LED signage displays. For example, due to the fact that a low DC voltage is distributed from the power converter <NUM> to the LED display module <NUM>, the electrical current in the power cable 16A (see <FIG>) and in other wiring of the LED signage display <NUM> is significantly large (as the power consumption of the LED signage display <NUM> is constant), thereby causing substantial amounts of energy losses in the form of heat. Therefore, a prior-art digital LED signage display usually requires multiple fans and/or large heat-sinks for heat dissipation, and consequently requires an effective thermal management system. The large amount of generated heat is also a risk to safety and reliable operation of digital LED signage displays.

Moreover, using fans or rotational parts for the digital LED signage display significantly reduces its reliability since the rotational parts are usually the points of failure in these products.

As each LED driver <NUM> is connected to the central controller <NUM> via the cable 16B (for example, a ribbon cable), a large digital LED signage display <NUM> generally requires one or more ribbon cables 16B having a large number of wires therein, which makes the digital LED signage display <NUM> expensive and unreliable since there is a high risk that the wires in ribbon cables may get disconnected and/or damaged over time, particularly in outdoor applications.

In addition, prior-art LED drivers are not able to smoothly modulate the current flowing through the LEDs thereby decreasing the quality of images displayed on the LED signage during color transitions. Documents <CIT> and <CIT> disclose the preamble of the independent claims.

Further implementations are defined in the dependent claims.

The embodiments of the present disclosure will now be described with reference to the following figures in which identical reference numerals in different figures indicate identical elements, and in which:.

The present disclosure generally relates to a LED apparatus. In some embodiments disclosed herein, the LED apparatus may be a digital LED signage. The LED apparatus disclosed herein comprises a power and control architecture based on an integrated solution distributed along the apparatus. The integrated solution offers a highly efficient and compact solution for the LED apparatus, and has advantages such as higher efficiency, compactness, less wiring, simpler heat removal, and no rotational components (i.e., the disclosed LED apparatus is fan-less). The power and control architectures disclosed herein enable the LED apparatus to achieve improved performance for each individual LED, leading to a highly energy-efficient product.

Turning now to <FIG>, an LED apparatus in the form of a digital LED signage display is shown and is generally identified using reference numeral <NUM>. As shown, the digital LED signage display <NUM> comprises an advanced LED display module <NUM> formed by a plurality of LED display submodules <NUM>. Each LED display submodule <NUM> comprises a plurality of LEDs <NUM> drivable at a driving DC voltage such as 5V, <NUM>. 5V, 12V, or the like, depending on the implementation.

The digital LED signage display <NUM> also comprises a power source or power supply <NUM> in the form of an AC/DC power converter in electrical connection with the LED display submodules <NUM> of the advanced LED display module <NUM>, and a gateway <NUM> in wireless communication with the LED display submodules <NUM> of the LED display module <NUM>.

The AC/DC power supply <NUM> may be mounted at a suitable location of the digital LED signage display <NUM> such as in a housing thereof and is physically separated from the advanced LED display module <NUM>. The AC/DC power supply <NUM> converts the electrical power of an external AC power source <NUM> (such as an AC power grid) into a source DC power at a source DC voltage and outputs the source DC power to the LED display submodules <NUM> (and in particular to an LED power Integrated Circuit (IC) chip <NUM> thereof; described in more detail later) via a power cable <NUM> for powering the LEDs <NUM>. The source DC voltage is generally higher than the driving DC voltage of the LEDs <NUM>. In some embodiments, the source DC voltage of the AC/DC power supply <NUM> is higher than <NUM>. In some embodiments, the source DC voltage of the AC/DC power supply <NUM> is higher than 12V. In some embodiments, the source DC voltage of the AC/DC power supply <NUM> is about 48V.

The AC/DC power supply <NUM> outputs a higher source DC voltage compared to the prior-art, low-voltage power distribution LED signage displays. Therefore, the electrical current passing through the power cable <NUM> and consequently the energy loss on the power cable <NUM> and heat generated therefrom are substantially smaller than that of the prior-art designs that have similar constant power consumption. Furthermore, the high-voltage distribution (for example, 48V) significantly facilitates the integration of solar energy and energy storage (batteries) into the digital LED signage display <NUM>. In comparison, the prior-art designs require multiple power conversion components to implement solar energy and energy storage integration.

Referring again to <FIG>, the gateway <NUM> is configured for wirelessly communicating with the LED display submodules <NUM> (and in particular a wireless communication unit <NUM> thereof; shown in <FIG>, <FIG> and described in more detail later) and with an external computing device <NUM> such as a desktop computer, a laptop computer, a smartphone, a tablet, or the like. Therefore, a user (not shown) of the computing device <NUM> may initiate a command for controlling the LED signage display <NUM> that is sent wirelessly to the gateway <NUM>. In response to the command, the gateway <NUM> then wirelessly communicates with the LED submodules <NUM> to adjust the lighting of the LEDs <NUM> thereof.

In various embodiments, the wireless connection between the gateway <NUM> and the LED submodules <NUM> and/or the wireless connection between the gateway <NUM> and the external computing device <NUM> may be any suitable wireless communication technologies such as WI-FI®, (WI-FI is a registered trademark of the City of Atlanta DBA Hartsfield-Jackson Atlanta International Airport Municipal Corp. , Atlanta, GA, USA), BLUETOOTH® (BLUETOOTH is a registered trademark of Bluetooth Sig Inc. , Kirkland, WA, USA), ZIGBEE® (ZIGBEE is a registered trademark of ZigBee Alliance Corp. , San Ramon, CA, USA), wireless mobile telecommunications technologies (such as GSM, CDMA, LTE, and the like), and/or the like.

<FIG> is a schematic diagram of the advanced LED display module <NUM>. As described above, the advanced LED display module <NUM> comprises a plurality of LED submodules <NUM> wherein the LED submodule 108A at the upper-right corner thereof is shown separated from other LED submodules <NUM> for clearer illustration of submodule. Each LED submodule <NUM> (including submodule 108A) comprises one or more LEDs <NUM>.

In the example shown in <FIG>, the advanced LED display module <NUM> comprises twenty four (<NUM>) LED submodules <NUM> arranged as a <NUM>-by-<NUM> matrix. Of course, in other embodiments, the LED module <NUM> may comprise different numbers of LED submodules <NUM>, and the LED submodules <NUM> may be arranged in different configurations for example, in different numbers of rows and columns and/or in different layouts such as triangles, circles, and the like.

In the example shown in <FIG>, each LED submodule <NUM> preferably comprises nine (<NUM>) LEDs <NUM> arranged in a <NUM>-by-<NUM> matrix which is optimal for this example of an integrated solution based on Applicant's power-loss calculation. However, in other embodiments, an LED submodule <NUM> may comprise different numbers of LEDs <NUM>, and the LEDs <NUM> may be arranged in different configurations such as in different numbers of rows and columns, and/or in different layouts such as triangles, circles, and the like.

<FIG> and <FIG> are simplified block diagrams of an LED submodule <NUM>. As shown, the LED submodule <NUM> comprises and integrates therein one or more LEDs <NUM> and an LED power Integrated Circuit (IC) chip <NUM> that provides a multi-functional, integrated solution for individually powering and controlling each LED <NUM> of the LED submodule <NUM> (for example, via an individual power wire and an individual signal wire). The LED power IC <NUM> may comprise a wireless communication unit <NUM> such as a radio frequency (RF) wireless transceiver, a digital control unit <NUM>, and a multi-output DC/DC converter <NUM>.

The wireless communication unit <NUM> is in signal communication with the digital control unit <NUM> and is in wireless communication with the gateway <NUM> for wirelessly receiving the control information such as color, light intensity, and the like from the gateway <NUM> (or a central controller) of the digital signage <NUM>. In this embodiment, the gateway <NUM> is physically separated from the advanced LED display module <NUM>. In response to instructions received from one or more computing devices <NUM>, the gateway <NUM> communicates with the wireless communication unit <NUM> of the LED Power IC <NUM> of each LED submodule <NUM> via a wireless communication connection <NUM> for controlling the corresponding LEDs <NUM> in the LED submodule <NUM>. The wireless communication unit <NUM> also reports the status of each LED <NUM> in the LED submodule <NUM> for diagnosis and troubleshooting purposes. The wireless communication unit <NUM> thus eliminates the need of control-wires required in conventional designs.

The digital control unit <NUM> provides control signals for the multi-output DC/DC converter <NUM>. It also receives the high-level signals from the wireless communication unit <NUM>, then decodes the information therein and finally, produces appropriate gate signals for the digital switches/MOSFETs (similar to the digital switches <NUM> of <FIG>) of the multi-output DC/DC converter <NUM>. The digital control units <NUM> play a pivotal role in system optimization, diagnosis, and reliability of the advanced LED display module <NUM>. Each digital control unit <NUM> provides substantial flexibility to control LEDs <NUM> of the respective LED submodule <NUM> in an optimized manner, updates the required information through the wireless communication unit <NUM>, and receives system updates.

<FIG> is a simplified circuit diagram of the power architecture of the LED power IC <NUM>, showing the multi-output DC/DC converter <NUM> of the LED power IC <NUM> driving the LEDs <NUM>. As shown, the DC/DC converter <NUM> of the LED power IC <NUM> receives the high-voltage DC power from the AC/DC power supply <NUM> via the power cable <NUM>, converts the high-voltage power to suitable low-voltage DC power such as 5V or 12V DC power depending on the implementation, and independently outputs the low-voltage DC power via an electrical wire or conductor <NUM> to each LED <NUM> of the LED submodule <NUM>. As the DC/DC converter <NUM> is physically in the LED submodule <NUM>, the length of each electrical wire or conductor <NUM> is much shorter than that of the power cable <NUM>.

With above design, a major portion of the electrical path from the AC/DC power supply <NUM> to each LED <NUM> of the advanced LED display module <NUM> is a high-voltage, small-current path. Subsequently, the energy losses in the form of heat through the electrical path are significantly reduced.

Moreover, each multi-output DC/DC converter <NUM> can independently and precisely control the LEDs <NUM> in the respective submodule <NUM> by independently and precisely controlling the current of each output <NUM>. As a result, the light intensity of each LED <NUM> may be smoothly modulated for smooth dimming. The DC/DC converter <NUM> altogether eliminates the need for series resistors and drivers to perform dimming.

The control on the voltage across each LED <NUM> and current therethrough provides substantial flexibility to optimize the operation of the LEDs <NUM> and offers higher overall efficiency of the digital LED signage <NUM>. In addition, the DC/DC converter <NUM> is able to smoothly modulate its output currents by ramping up and down the corresponding output voltages. On the other hand, the PWM signals and the LED drivers of the prior-art LED signage displays instantaneously apply the low-voltage power on LEDs, which creates significant amounts of Electro Magnetic Interference (EMI) and switching losses. By using a tight closed-loop control on the output currents of each multi-output DC/DC converter <NUM>, the output currents thereof can be smoothly modulated. The EMI issues and switching losses are thus eliminated or at least significantly reduced.

In the prior-art design as shown in <FIG>, one or more power cables 16A are required for electrical connection between the power converter <NUM> and each LED driver <NUM> of the LED display module <NUM> for powering the LEDs <NUM>. One or more control cables 16B, for example, in the form of ribbon cables, are also required for electrical connection between the central controller <NUM> and each LED driver <NUM> of the LED display module <NUM> for transmission of control signals.

On the other hand, the digital LED signage <NUM> disclosed herein only requires a power cable <NUM> with each wire therein connecting the AC/DC power supply <NUM> to a respective LED submodule <NUM> (in particular, to the DC/DC converter <NUM> of the LED power IC <NUM> of the LED submodule <NUM>). The digital LED signage <NUM> does not require any control wires because the control signals are transmitted to the LED submodule <NUM> wirelessly. Therefore, the digital LED signage <NUM> and its LED power/lighting management comprise a significantly reduced number of wires thereby reducing the risk of lighting malfunctions caused by broken wires in the cable <NUM>, reducing the cost of manufacturing for digital LED signage <NUM>, and simplifying the diagnoses and repairs in the event that any wires in the cable <NUM> are broken.

In above embodiments, the digital LED signage <NUM> comprises an AC/DC power supply <NUM>. In an alternative embodiment as shown in <FIG>, the digital LED signage <NUM> may comprise a solar panel <NUM> having a high-voltage DC output such as a 48V DC output and in electrical connection with an advanced LED display module <NUM> and an energy-storage unit <NUM> such as a rechargeable battery pack for powering the advanced LED display module <NUM> and for charging the energy-storage unit <NUM>. As those skilled in the art will appreciate, the energy-storage unit <NUM> may also output a high-voltage DC power to the advanced LED display module <NUM>. Therefore, the combination of the solar panel <NUM> and the energy storage unit <NUM> is equivalent to the power supply <NUM> shown in <FIG>.

<FIG> shows a simplified block diagram of a digital LED signage <NUM> according to another embodiment of the present disclosure. The digital LED signage <NUM> in this embodiment comprises an advanced LED display module <NUM> selectively coupled to an AC/DC power supply <NUM> in the form of an AC/DC power converter electrically connectable to an AC power source, and a solar panel <NUM> having an energy storage unit <NUM> such as a rechargeable battery pack via switches S<NUM> and S<NUM>. In other words, the power source of the advanced LED display module <NUM> is switchable between at least the AC/DC converter <NUM> and a combination of a solar panel and an energy storage unit via switches S<NUM> and S<NUM>.

The AC/DC power supply <NUM> receives AC power from an AC grid <NUM> and converts the AC power of the AC grid <NUM> to a high-voltage DC power such as a 48V DC power for selectively outputting the DC power to the advanced LED display module <NUM> when the switch S<NUM> is closed and the switch S<NUM> is open.

The solar panel <NUM> has a high-voltage DC power output such as a 48V DC power output and is in electrical connection with the energy-storage unit <NUM> for charging the energy-storage unit <NUM>. When the switch S<NUM> is open and the switch S<NUM> is closed, both the solar panel <NUM> and the energy-storage unit <NUM> are electrically connected to the advanced LED display module <NUM> for selectively outputting the high-voltage DC power thereto. Therefore, the power supplied to the advanced LED display module <NUM> may be switched as needed between the AC grid <NUM> and the solar panel <NUM>/energy-storage unit <NUM>. For example, the advanced LED display module <NUM> may be powered by the solar panel <NUM>/energy-storage unit <NUM> when the power output therefrom is sufficient, and may be powered by the AC grid <NUM> when the power output from the solar panel <NUM>/energy-storage unit <NUM> is insufficient.

While in above embodiments, the power and control architecture is described for use in digital LED signage, those skilled in the art appreciate that in some alternative embodiments, the power and control architecture may be used in other types of LED devices, such as an LED lighting device having a plurality of LEDs.

Although in above embodiments, an LED display system having an LED signage display is disclosed, in some alternative embodiments, the LED signage display may be an LED lighting apparatus, which, rather than being used for displaying images, is used for lighting purposes. Correspondingly, the LED system in these embodiments is then an LED lighting system.

In above embodiments, the advanced LED display module <NUM> comprises a plurality of LED submodules <NUM>, and each LED submodule <NUM> comprises a plurality of LEDs <NUM>. In some embodiments, each LED submodule <NUM> may comprise only one LED <NUM>. In some embodiments, the advanced LED display module <NUM> may comprise only one LED submodule <NUM>.

In above embodiments, each DC/DC convertor <NUM> is physically integrated into the respective LED submodule <NUM>. In some embodiments, at least some of the DC/DC convertors <NUM> are physically in proximity with the respective LED submodules <NUM>. For example, in one embodiment, at least some of the DC/DC convertors <NUM> may be removably attached to the back of the respective LED submodules <NUM>.

Claim 1:
A LED apparatus (<NUM>) comprising:
a power source (<NUM>) outputting a source DC power at a source DC voltage; and
an LED module (<NUM>) physically separated from the power source (<NUM>) and comprising one or more LED submodules (<NUM>), each LED submodule (<NUM>) comprising therein a DC/DC converter (<NUM>) and a plurality of LEDs (<NUM>) electrically coupled to the DC/DC converter (<NUM>), the plurality of LEDs (<NUM>) being drivable by a driving DC power at a driving DC voltage lower than the source DC voltage;
wherein the DC/DC converter (<NUM>) of each LED submodule (<NUM>) is configured for electrically coupling to the power source (<NUM>) via a power cable (<NUM>) and for converting the source DC power to the driving DC power at the driving DC voltage for driving the plurality of LEDs (<NUM>) of the LED submodule (<NUM>);
wherein in each LED submodule (<NUM>), the DC/DC converter (<NUM>) comprises a plurality of outputs each coupled to a respective one of the plurality of LEDs (<NUM>) in the LED submodule (<NUM>) for outputting the driving DC power thereto;
the LED apparatus (<NUM>) being characterized in that, in each LED submodule (<NUM>), the DC/DC converter (<NUM>) is configured to smoothly modulate a current at each output of the DC/DC converter (<NUM>) by ramping up and down a corresponding output voltage, to thereby smoothly modulate a light intensity of the LED (<NUM>) coupled to the respective output of the DC/DC converter (<NUM>) for smooth dimming.