Apparatus and methods for high power LED lights

A Light-Emitting Diode (LED) light system has a plurality of LED groups connected in parallel with each of the plurality of LED groups having one or more LEDs connected in series, a power circuit having a plurality of outputs with each output of the power circuit is electrically coupled to a respective one of the plurality of LED groups, and a control subsystem electrically coupled to the power circuit for individually controlling each output of the power circuit for controlling the operation of the corresponding LED group and adapting to the characteristics thereof. In some embodiments, at least one LED group may further have a switch and/or a light-angle controlling structure connected with the one or more LEDs in series and controlled by the control subsystem for selectively enabling or disabling the LED group and/or adjusting the light angle thereof.

FIELD OF THE DISCLOSURE

The present disclosure relates to lighting solutions using Light-Emitting Diode (LED) lights, and in particular to apparatus, method, and system for high-power LED lights.

BACKGROUND

Light-Emitting Diodes (LEDs) are known and have been widely used in industries such as for lighting solutions and as low-power light indicators. In recent years, LEDs with increased power output or increased luminous intensity have been developed and used for illumination. For example, with improved energy efficiency, safety, and reliability, LED lights 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, energy-efficient 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.

Lighting solutions for highways and warehouses are important applications requiring high-luminous intensities. Lighting these areas usually requires much higher power compared to other applications such as residential lighting applications. With the advantages such as higher efficiency, high-light intensity, and the like, LEDs with increased power output and/or increased luminous intensity have become promising candidates for highway and warehouse lighting solutions.

FIG.1shows a typical configuration of a prior-art high-power LED light10. As shown, the LED light10comprises a plurality of strings16of LEDs18connected in parallel and an alternate-current to direct-current (AC/DC) converter14for converting the alternate current (AC) from an AC power source12such as an AC grid to direct current (DC) for powering all strings16of LEDs18. However, such a prior-art high-power LED light10may have low power efficiency for the following reasons.

LED characteristics are usually sensitive to deviations in the voltage or the current.FIG.2Ashows the current-voltage (I-V) characteristics of a typical LED where the current is represented using the symbol i and the voltage is represented using the symbol v. It is clear that a small deviation in the voltage or the current may result in significantly different characteristics such as a significantly different equivalent impedance.

LEDs generally have different characteristics and it is difficult or even impossible to ensure all LEDs18of the prior-art high-power LED light10to have the same characteristics. Referring back toFIG.1, since the LED strings16are connected in parallel, all LED strings16are driven by the same voltage. However, as the LEDs18of each string16may have different characteristics, there may be voltage/current deviations on the LEDs18thereof, thereby causing the LEDs18operating in un-optimized conditions and resulting in low power-efficiency. Another issue of the prior-art high-power LED light10is the detrimental impacts of un-optimized operation conditions to the life-time of the LEDs18. For example, operating at high-impedance regions causes thermal stress on LEDs18and shortens their life-time.

As shown inFIG.2B, a LED18has a fixed angular span of light. However, different types of LEDs may have different characteristics such as different light angular-spans, different efficacies, and/or the like. Therefore, based on the application, a specific type of LED has to be selected to provide similar characteristics such as a similar or desired light angular-span. Such a selection requirement usually causes significant burdens to the manufacturing as manufacturers have to make different designs for different applications and cannot use a universal solution. An LED light with the capability to change its light angular-span would greatly facilitate the manufacturing of high-power LED lights.

SUMMARY

According to one aspect of this disclosure, there is disclosed a Light-Emitting Diode (LED) light system comprising: a plurality of LED groups connected in parallel, each of the plurality of LED groups comprising one or more LEDs connected in series; a power circuit comprising a plurality of outputs, each output electrically coupled to a corresponding one of the plurality of LED groups for individually powering the corresponding LED group; and a control subsystem electrically coupled to the power circuit for individually controlling each output of the power circuit for adaptively controlling an operation of the corresponding LED group coupled to said output.

In some embodiments, the control subsystem is configured for individually controlling each output of the power circuit for controlling the operation of the corresponding LED group coupled to said output for adapting to one or more characteristics thereof.

In some embodiments, each of the plurality of LED groups comprises a same number of LEDs.

In some embodiments, at least two of the plurality of LED groups comprise different numbers of LEDs.

In some embodiments, at least a first one of the plurality of LED groups further comprises a switch electrically coupled to the one or more LEDs in series; and the control subsystem is electrically coupled to the switch for selectively enabling or disabling said at least the first one of the plurality of LED groups.

In some embodiments, at least a second one of the plurality of LED groups further comprises a light-angle controlling structure; and the control subsystem is electrically coupled to the light-angle controlling structure for adjusting at least one of a light angle and a light angular-span of said at least the second one of the plurality of LED groups.

In some embodiments, said at least the second one of the plurality of LED groups further comprises a base structure controllable by the light-angle controlling structure thereof for rotating about one or more axes thereof for adjusting the light angle thereof.

In some embodiments, said at least the second one of the plurality of LED groups further comprises one or more sub-platforms each comprising a subset of the LEDs of the LED group; and each of the one or more sub-platforms is controllable by the light-angle controlling structure thereof for rotating about one or more axes thereof for adjusting the light angular-span thereof.

In some embodiments, at least one of the LEDs is rotatably coupled to a microelectromechanical-structure (MEMS) component thereby forming a LED assembly for adjusting light-emission angle hereof under the control of the MEMS component.

In some embodiments, the plurality of LED groups comprise a plurality of LED assemblies printed onto the base.

In some embodiments, the LED light system further comprises a communication subsystem. The control subsystem is coupled to the communication subsystem for receiving and transmitting instructions for controlling the operation of the plurality of LED groups.

In some embodiments, the LED light system further comprises a motion sensor. The control subsystem is coupled to the motion sensor for receiving sensor data therefrom for controlling the operation of the plurality of LED groups.

In some embodiments, the LED light system further comprises a light sensor. The control subsystem is coupled to the light sensor for receiving sensor data therefrom for controlling the operation of the plurality of LED groups.

In some embodiments, the power circuit comprises a transformer having an input on a primary side thereof for receiving electrical power and a plurality of outputs on a secondary side thereof for individually powering the plurality of LED groups.

In some embodiments, the control subsystem comprises a voltage circuit, a first current-control circuit, and a pulse-code modulation (PCM) modulator for controlling a circuitry on the primary side of the transformer for power-factor correction.

In some embodiments, the control subsystem comprises a phase-shift modulator and a plurality of second current-control circuits for controlling a circuitry on the secondary side of the transformer for regulating currents of the plurality of LED groups.

In some embodiments, the control subsystem is configured for controlling the circuitry on the secondary side of the transformer for regulating the currents of the plurality of LED groups based at least on an output of the PCM modulator and output currents of the plurality of outputs on the secondary side of the transformer.

In some embodiments, the control subsystem is configured for controlling the circuitry on the secondary side of the transformer for regulating the currents of the plurality of LED groups based further on an output of the communication subsystem.

In some embodiments, the control subsystem is further configured for providing a phase-shift between voltage waveforms at the primary side of the transformer and voltage waveforms at the secondary side thereof.

According to one aspect of this disclosure, there is disclosed a method for controlling a plurality of LEDs for lighting. The method comprises: partitioning the plurality of LEDs into a plurality of LED groups connected in parallel, each of the plurality of LED groups comprising one or more of the plurality of LEDs connected in series; individually powering each of the plurality of LED groups; and individually controlling the powering of each LED group for adaptively controlling an operation of the LED group.

In some embodiments, said individually controlling the powering of each LED group comprises: individually controlling the powering of each LED group for controlling the operation of the LED group for adapting to one or more characteristics thereof.

In some embodiments, each of the plurality of LED groups comprises a same number of LEDs.

In some embodiments, at least two of the plurality of LED groups comprise different numbers of LEDs.

In some embodiments, said individually controlling the powering of each LED group further comprises: using a switch for selectively enabling or disabling at least a first one of the plurality of LED groups.

In some embodiments, said individually controlling the powering of each LED group further comprises: adjusting at least one of a light angle and a light angular-span of at least a second one of the plurality of LED groups.

In some embodiments, said second LED group further comprises a base structure; and said adjusting the at least one of the light angle and the light angular-span of the at least the second one of the plurality of LED groups comprises: rotating the base structure about one or more axes thereof for adjusting the light angle thereof.

In some embodiments, said at least the second one of the plurality of LED groups further comprises one or more sub-platforms each comprising a subset of the LEDs of the LED group; said second LED group further comprises a base structure; and said adjusting the at least one of the light angle and the light angular-span of the at least the second one of the plurality of LED groups comprises: rotating each of the one or more sub-platforms about one or more axes thereof for adjusting the light angular-span thereof.

In some embodiments, the method further comprises: receiving and transmitting instructions via a communication subsystem for controlling the operation of the plurality of LED groups.

In some embodiments, the method further comprises: detecting motion about the plurality of LED groups; and controlling the operation of the plurality of LED groups based on the motion-detection.

In some embodiments, the method further comprises: sensing light about the plurality of LED groups; and controlling the operation of the plurality of LED groups based on the light-sensing.

In some embodiments, said individually powering each of the plurality of LED groups comprises: using a transformer for receiving electrical power at a primary side thereof and individually powering the plurality of LED groups from a plurality of outputs on a secondary side thereof.

In some embodiments, said individually controlling the powering of each LED group comprises: using a voltage circuit, a first current-control circuit, and a pulse-code modulation (PCM) modulator for controlling a circuitry on the primary side of the transformer for power-factor correction.

In some embodiments, said individually controlling the powering of each LED group comprises: using a phase-shift modulator and a plurality of second current-control circuits for controlling a circuitry on the secondary side of the transformer for regulating currents of the plurality of LED groups.

In some embodiments, said individually controlling the powering of each LED group comprises: controlling the circuitry on the secondary side of the transformer for regulating the currents of the plurality of LED groups based at least on an output of the PCM modulator and output currents of the plurality of outputs on the secondary side of the transformer.

In some embodiments, said individually controlling the powering of each LED group comprises: controlling the circuitry on the secondary side of the transformer for regulating the currents of the plurality of LED groups based further on an output of the communication subsystem.

In some embodiments, said individually controlling the powering of each LED group comprises: providing a phase-shift between voltage waveforms at the primary side of the transformer and voltage waveforms at the secondary side thereof.

DETAILED DESCRIPTION

Turning now toFIG.3, a high-power Light-Emitting Diode (LED) light system is shown and is generally identified using the reference numeral100. As shown, the LED light system100comprises a multi-output power circuit102receiving electrical power from an alternate current (AC) power source104such as an AC grid and converting the AC power to a direct current (DC) voltage for powering a plurality of LEDs106. The multi-output power circuit102comprises a plurality of DC outputs108-1,108-2, . . . ,108-N (collectively denoted using reference numeral108; and N>1 being an integer). Correspondingly, the LEDs106are arranged in to N LED groups110-1,110-2, . . . ,110-N (collectively denoted using reference numeral110), with each LED group110connected to a respective DC output108of the multi-output power circuit102.

Each LED group110comprises one or more LEDs106, a light-angle controlling structure112(also denoted using the symbol Mn, n=1, 2, . . . , N, for the light-angle controlling structure of the n-th LED group), and a switch114(also denoted using the symbol Snfor the switch of the n-th LED group), all connected in series. Each switch114is configurable between an on or closed condition and an off or open condition for selectively enabling or disabling the corresponding LED group110.

Each light-angle controlling structure112is configured for controlling the light angle and/or the light angular-span of the LED group110. For example, in some embodiments as shown inFIG.4A, the LEDs106of each LED group110may be installed, mounted, or otherwise coupled to a base structure142(such as a supporting platform) rotatable about one or more axes144thereof as indicated by the arrow146. One or more motors148are coupled to the base structure144and under the control of the light-angle controlling structure112(not shown) for rotating the base structure142and the LEDs106thereon about the one or more axes144for controlling the light angle.

In some embodiments as shown inFIG.4B, the base structure142may comprise one or more sub-platforms152each comprising a subset of the LEDs106of the LED group110coupled thereon and rotatable under the control of one or more motors (not shown) about one or more axes154thereof for adjusting the light angular-span. As shown inFIG.4B, the light-angle controlling structure112in these embodiments may control both the light angle and the light angular-span.

Those skilled in the art will appreciate that in some embodiments similar to that shown inFIG.4B, the base structure142may not be rotatable. Therefore, the light-angle controlling structure112in these embodiments may only control the sub-platforms152for adjusting the light angular-span.

In the embodiments shown inFIG.4B, the sub-platforms152are rotatably coupled to the base structure142. In some embodiments, the LED group110may not comprise a base structure and each sub-platform152is rotatably coupled to a respective support structure.

In some embodiments, the light direction or light-emission angle of each LED106may be individually controlled. For example, as shown inFIG.4C, a LED assembly160may comprise a LED106rotatably coupled to a microelectromechanical-structure (MEMS) component162such that the MEMS component, in response to suitable electrical signal, controls the light-emission angle of the LED106coupled thereto for adjusting the light direction of the LED106.

Referring back toFIG.3, the LED groups110may each comprise a base structure with one or more LED assemblies160installed thereon such that the light angle and the light angular-span of each LED group110may be more precisely controlled by the light-angle controlling structure112or the control subsystem122. Each LED group110may also comprise one or more LEDs not coupled to or associated with any MEMS components.

As those skilled in the art will appreciate, the base structure may be non-rotatable in some related embodiments, or may be rotatable in some other related embodiments for achieving, e.g., large light-angle adjustment range.

In some embodiments, the LED assemblies160may be printed onto the base structure thereby significantly simplifying the manufacturing process.

As shown inFIG.3, the LED light system100also comprises a control subsystem122configured for controlling the multi-output power circuit102, the light-angle controlling structures112, and the switches114for optimizing the operation of LED groups110. In these embodiments, the control subsystem122receives sensor data and instructions from a motion sensor124and a communication subsystem126, respectively, and uses received data to adjust the operation of the LED groups110. The motion sensor124is used for detecting moving objects such as vehicle traffics, pedestrians, and the like, such that the LEDs groups110are turn on when moving objects are detected. The communication subsystem126is used for receiving LED-group-control instructions from for example a remote control center for controlling the operation of the LED groups110.

With the data and instructions received from the motion sensor124and the communication subsystem126, the control subsystem122may control the multi-output power circuit102to turn on the LED groups110, turn off the LED groups110, adjust the output voltage and/or current, or the like; the control subsystem122may control the light-angle controlling structures112to adjust the light angles of corresponding LED groups110; the control subsystem122may also control the switches114to enable or disable the corresponding LED groups110for adjusting the light intensity of the LED light system100.

By arranging the LEDs106into a plurality of LED groups110and by individually powering each LED group110with a separate DC output108, the system100may adapt to the different characteristics of the LED groups110and optimize the operation of each LED group110individually or separately.

For example, each LED group110may be tested via a calibration process to determine an optimal impedance region thereof and the corresponding current/voltage. Then, the multi-output power circuit102sets the operation current/voltage of each LED group110to its determined current/voltage to ensure that the LED group110operates in its optimal impedance region.

Therefore, as the current/voltage of each LED group110is individually controlled, the discrepancies and tolerances in LED groups110may be compensated accordingly. Although the LEDs106of a LED group110may still have different characteristics such as different voltage/current deviations, the voltage/current applied to the LED group110is adapted to “averaged” characteristics of a relatively small number of LEDs106compared to the prior-art LED light system using a single output to drive all LEDs in which all LEDs are connected in parallel and a same voltage is applied thereto. Such “averaged” characteristics of a relatively small number of LEDs106may exhibit smaller deviations and/or discrepancies than “averaged” characteristics of a large number of LEDs106(e.g., all LEDs in prior-art systems). Adapting the outputs of the multi-output power circuit102to the respective LED groups110may delay the efficiency deterioration of the LEDs106.

Moreover, one may choose the LEDs106such that the LEDs106in a same LED group110are similar in one or more easily-identifiable properties, e.g., manufactured by a same manufacturer, manufactured in a same batch, and/or the like. Such LEDs106may more likely have similar characteristics and the LED group110may have reduced deviations and/or discrepancies from its “averaged” characteristics compared to a LED group110comprising randomly selected LEDs106.

Those skilled in the art will appreciate that a tradeoff may be made between the optimization of LED lighting operation and the system cost. For example, for a given number of LEDs106, the LED light system100in some embodiments may comprise a larger number of LED groups110with each LED group comprising a smaller number of LEDs106to achieve a better-optimized LED lighting operation but with higher cost (due to a larger number of DC outputs and more wiring required). In some other embodiments, the LED light system100may comprise a smaller number of LED groups110with each LED group comprising a larger number of LEDs106to achieve a lower cost (because of a smaller number of DC outputs and less wiring required) but a less-optimized LED lighting operation.

In some embodiments, the LEDs106of each LED group110may be selected to have similar characteristics while the LEDs106of different LED groups110may have different characteristics. Compared to the prior-art system that requires all LEDs to have similar characteristics, the LED light system100in these embodiments imposes less burden to the manufacturing.

Those skilled in the art will appreciate that in some embodiments, different LED groups110may have different numbers of LEDs as needed and/or for achieving an optimized balance between LED lighting operation and cost.

FIG.5is a circuit diagram showing the multi-output power circuit102implemented using a non-resonant power circuit in some embodiments. As shown, the power circuit102provides multiple outputs108-1to108-N for individually powering the LED groups110. The power circuit102also comprises a power-factor correction (PFC) circuit202at the AC side implemented using the inductors L1and L2and the switches S1pand S2p(implemented using metal-oxide-semiconductor field-effect transistors (MOSFETs)) such that the current drained from the AC grid104is nearly sinusoidal and in phase with the grid voltage.

The multi-output power circuit102comprises a transformer204having a single input206at the primary side thereof and a plurality of outputs108-1to108-N with output voltages vo1to voNat the secondary side thereof. The transformer204receives the output of the PFC circuit202at its input206and generates N outputs108-1to108-N at the secondary side thereof, which are then rectified by corresponding synchronous rectifier-switches SR1to SRN(implemented using MOSFETs) with a closed-loop control for regulating the output currents io1to ioNfor powering LED groups110-1to110-N. In these embodiments, the switches S1to SNare also implemented using MOSFETs. As will be described in more detail later, the output current to each LED group110is controlled at the secondary side of the transformer204. The multi-output power circuit102may effectively provide optimal performance for each LED group110. Since the current for each LED group110is individually controlled, any discrepancies and tolerances in LED groups110may be individually compensated.

FIG.6is a block diagram showing a control subsystem122for controlling the non-resonant multi-output power circuit102of the LED light system100. For ease of illustration, the output from the motion sensor124and the light-angle control are omitted in this figure.

As shown, the control subsystem122comprises a voltage controller222, a multiplier223, a current controller224, and a pulse-code modulation (PCM) modulator226for controlling the switches S1pand S2pon the primary side of the transformer204to perform power-factor correction based on a reference voltage Vref, the bus voltage Vbus, the output voltage Vgof the power source104, the output current igof the power source104, and the input current ipto the transformer204. The controllers222and224may be implemented as respective control circuits.

The control subsystem122also comprises current controllers232(which may be implemented as control circuits) and a phase-shift modulator234for controlling the switches SRnand Sn(n=1, 2, . . . , N) on the secondary side of the transformer204based on the PCM of the PCM modulator222, the output currents io1to ioNof the DC outputs108-1to108-N, and the output of the communication subsystem, for regulating the currents io1to ioNflowing through the LED groups110-1to110-N, and for providing a phase-shift between the high-frequency voltage waveforms at the primary side of the transformer204and at the secondary side of the transformer204.

FIG.7is a circuit diagram showing the multi-output power circuit102implemented using a resonant power circuit in some embodiments. The multi-output power circuit102in these embodiments is similar to that shown inFIG.5except that the multi-output power circuit102in these embodiments further comprises a resonant circuit242at the primary side of the transformer204.

The resonant circuit242in these embodiments is implemented using a capacitor Csand inductors Lsand Lp, and supplies a high-frequency sinusoidal current for the high frequency transformer204. The transformer204receives the high-frequency current at its input206and generates N outputs108-1to108-N at the secondary side thereof which are then rectified by corresponding synchronous rectifier-switches SR1to SRN(implemented using MOSFETs) with a closed-loop control for regulating the output currents io1to ioNfor powering LED groups110-1to110-N. The output current to each LED group110is controlled at the secondary side of the transformer204. The multi-output power circuit102can effectively provide optimal performance for each LED group110. Since the current for each LED group110is individually controlled, any discrepancies and tolerances in LED groups110may individually be compensated.

As shown inFIG.8, the control subsystem122shown inFIG.6may also be used for controlling the resonant multi-output power circuit102of the LED light system100.

FIGS.9to11shown the simulation/experimental results of the LED light system100shown inFIG.8whereinFIGS.9and10are in the line frequency scale andFIG.11is in the switching frequency scale. The symbol “I(Lg1)” inFIG.9represents the current on L1(seeFIG.8). The symbol iLEDinFIGS.10and11represents the current flowing through the LEDs106of a randomly-selected LED group110.

In above embodiments, the LED light system100comprises a motion sensor124for providing data to the control subsystem122for controlling the LEDs106. In some alternative embodiments, the LED light system100may also comprise other suitable sensors such as one or more light sensors deployed at suitable locations (e.g., each adjacent a respective LED group110) for providing data regarding the current ambient light level to the control subsystem122for controlling the LEDs106of each LED group110.

Although the LED light system100in above embodiments comprises a motion sensor124, in some alternative embodiments, the LED light system100may not comprise a motion sensor124.

In some embodiments, the LED light system100may comprise a plurality of motion sensors124deployed at suitable locations (e.g., each adjacent a respective LED group110) for detecting motions thereabout and providing motion-detection data to the control subsystem122for controlling the LEDs106of each LED group110.

Although the LED light system100in above embodiments comprises a communication subsystem126, in some alternative embodiments, the LED light system100may not comprise a communication subsystem126.

Although in above embodiments, each LED group comprises a light-angle controlling structure112and a switch114, in some embodiments, at least one LED group may not comprise a light-angle controlling structure112. Yet in some embodiments, at least one LED group may not comprise a switch114. Still in some embodiments, at least one LED group may not comprise a light-angle controlling structure112nor a switch114.