Patent Description:
Conventional LED fixtures comprises three major parts:.

The fixture can also include secondary optics or lenses.

While LED prices are decreasing, and performance is increasing, the driver and housing costs have remained fairly constant.

Large commercial installations may utilize hundreds or thousands of LED fixtures, each including its own expensive AC-DC driver circuit.

Typically, in the United States, power from the power mains is specified at 480V, <NUM> AC, Triple phase. As noted above, power needs to be supplied to individual fixtures of LED lights. The desired LEDs require 20V DC at <NUM> A and power to be current regulated and maintained steady at <NUM> A.

<FIG> illustrates a current system for accomplishing the illumination of a large number of LEDs. As may be seen in <FIG>, each fixture of LEDs utilizes individual drivers that are connected to the main power line. Power electronics are required to convert AC to DC, step down the voltage and regulate the current to the LEDs. This configuration requires expensive electronics for each fixture and expensive power line wiring to each fixture.

<FIG> illustrates another current system for accomplishing the illumination of a large number of LEDs. As may be seen in <FIG>, a centralized AC-DC system with a step-down power source is utilized. A number of fixtures are connected in parallel (for example <NUM> fixtures) and power is supplied using a large AC-DC power source that delivers 20V at <NUM> amps. However, <NUM> amps at <NUM> VDC requires large gauge wires (especially over the long distances in a greenhouse installation), which can significantly increase costs and suffer from major line losses, reducing efficiency. Moreover, the large AC-DC power source is expensive and, in the end, may not deliver much savings over the current method noted above. In addition, some electronics are still required in each fixture to provide current regulation.

<CIT> issued to the current inventor and titled "Driverless LED Fixture" (hereinafter "'<NUM> Patent") teaches the use of a direct current power supply to power a plurality of LEDs in series. See Fig. 2C. However, the '<NUM> Patent only provides for a single circuit and single LED arrays and therefore, does not take advantage of the efficiencies of multi-circuit power supply. <CIT> discloses a constant current driving unit for constant current driving a plural number of series connected light emitting diodes by a pulse-width modulating constant current driving circuit. Bypass circuits, made up by a plural number of thyristors, each connected in parallel with each of series-connected light emitting diodes, are provided with gate potential setting circuits. These gate potential setting circuits afford to the thyristors a gate potential value such that, when the series-connected light emitting diodes are operating as normally, the thyristors are in the off-state. The gate potential setting circuit affords to the thyristors another gate potential value such that, when the light emitting diodes are in the open state, the thyristors connected in parallel with the light emitting diodes in the opened state will be in a turned-on state.

Objects of the present patent document are to provide improved lighting systems that are cheaper to manufacture and cheaper to install than current systems. In preferred embodiments, the lighting systems ameliorate many of the deficiencies in the costs of making and installing current systems. In particular, the embodiments herein are designed to provide the cheapest possible LED lighting solutions for lighting large growing operation such as those found in greenhouses.

In preferred embodiments, the LED system comprises a direct current power supply unit having a first channel and a second channel and a ground; a first circuit in electrical communication with the first channel of the power supply wherein the power supply provides a constant current to the first circuit; a second circuit in electrical communication with the second channel of the power supply wherein the power supply provides a constant current to the second circuit; a third circuit in electrical communication with the ground of the power supply; and a plurality of driverless luminaires connected in series wherein each driverless luminaire in the plurality of driverless luminaires has a first LED array electrically connected in series to the first circuit and a second LED array electrically connected in series to the second circuit and a driverless luminaire ground electrically connected to the third circuit.

In some embodiments, the first channel is comprised of a first three constant current drivers with outputs electrically connected in parallel and the second channel is comprised of a second three constant current drivers with outputs electrically connected in parallel.

In yet other embodiments, generally those embodiments used with three-phase AC power, the power inputs to the first three constant current drivers are electrically connected in a delta configuration and wherein the power inputs to the second three constant current drivers are connected in a delta configuration.

In still other embodiments, generally those with single phase AC power inputs, the power inputs to the first three constant current drivers are connected in parallel and wherein the power inputs to the second three constant current drivers are connected in parallel.

In preferred embodiments, the power supply is configured to adjust a first current on the first channel with respect to a second current on the second channel in response to an input signal. The input signal can be a pair of voltage signals communicated to an input of each of the first three constant current drivers and each of the second three constant current drivers.

In some embodiments, the power supply is configured to supply between <NUM> kilowatts and <NUM> kilowatts. In the preferred embodiment, the power supply is configured to supply <NUM> kilowatts, which is comprised by two <NUM> kilowatt channels and each channel is made up of three <NUM>-watt drivers.

In preferred embodiments, a first LED array anode is electrically connected directly to a first channel anode of the power supply and a second LED array anode is electrically connected directly to a second channel anode of the power supply and there is no driver between the first LED array and the first channel anode and there is no driver between the second LED array and the second channel anode.

In further embodiments, a first LED array cathode is electrically connected directly to a next driverless luminaire's first LED array anode and a second LED array cathode is electrically connected directly to a next driverless luminaire's second LED array anode and there is no driver between the first LED array and the next driverless luminaire's first LED array and there is no driver between the second LED array and the next driverless luminaire's second LED array.

<FIG> is a simplified perspective view of a typical greenhouse <NUM> in which the power distribution system of the present invention can be utilized. Greenhouses, especially when located in the middle and high latitudes, require supplemental artificial lighting in order to grow crops, such as tomatoes, year-round.

The dimensions of a typical section of a greenhouse configuration may be as follows: Length: Typically, between <NUM> and <NUM> feet; Width: <NUM> feet per section width; LED lights: <NUM>,<NUM>,<NUM> Multiple rows (<NUM> shown) approximately <NUM> feet apart in length.

Since lights (fixtures) are typically hung every <NUM> feet, there are from <NUM> to <NUM> light fixtures per row. The Applicant has realized that the size and lighting requirements for many greenhouses have been standardized or are, at a minimum, very often similar. To this end, there is a real opportunity in the market to develop the cheapest possible lighting solution that can illuminate such a space.

<FIG> is a block diagram of a current method for providing power to a power distribution system <NUM>. System <NUM> is powered by a source <NUM> of <NUM> volts, <NUM> AC which is coupled to a series of fixtures <NUM> and <NUM> and the last fixture <NUM> in a row via driver circuits <NUM>, <NUM> and <NUM>, respectively.

<FIG> is a block diagram of a power distribution system that may be used in place of the system shown in <FIG>. A source of AC power <NUM> is coupled to step-down device <NUM> which provides <NUM> VDC and <NUM> amps to a series of LED fixtures <NUM>, <NUM>, <NUM>,.

<FIG> illustrates a schematic view of an LED system <NUM> according to the teachings herein. The LED system <NUM> comprises a power supply unit <NUM> and a plurality of driverless luminaires <NUM>. In preferred embodiments, the power supply unit <NUM> is a direct current power supply unit.

The LED system <NUM> includes a plurality of driverless luminaires <NUM>. In preferred embodiments, each driverless luminaire comprises a housing and at least two LED arrays; a first LED array <NUM> and a second LED array <NUM>. In other embodiments, driverless luminaires <NUM> may be comprised of three, four, five or more LED arrays.

As noted above, a typical luminaire consists of three parts, LED board (or light engine), heat sink or physical enclosure and the driver. The embodiments herein consist exclusively of driverless luminaires that only include the LED board and the heat sink/housing and do not include a driver. A driverless luminaire is one or more LED board(s) (which consist of LED diodes mounted on PCBs) which thermally interface with a heat sink or enclosure. Separate luminaires will necessarily have physically separate heat sinks or enclosures that act as heat sinks.

An LED array is a group of LEDs connected in a series-parallel fashion. Each array consists of nS x mP LED diodes, where n represents the number of LEDs connected in series and m represents the number of LEDs in parallel. More than one array can exist on one PCB and one array can sometimes be mounted on multiple PCBs so the relationship of LED array to PCB is not necessarily one-to-one. For example, in some embodiments, the red channel LEDs are in a <NUM> x 10P array and the white channel LEDs are connected in a <NUM> x 26P array fashion. The driverless luminaire may consist of two PCBs and one heat sink. Each PCB contains <NUM>% of the red LEDs and <NUM>% of the white LEDs.

Each LED array <NUM>, <NUM>, is comprised of a plurality of LEDs, typically from <NUM> to <NUM> but may be up to <NUM> or more. As explained above, within the LED arrays, the individual LEDs are electrically connected in series-parallel fashion. The number of LEDs connected in series in each array is limited by total voltage available to the array divided by the average voltage drop (forward voltage, Vf) of each LED in the array. The number of LEDs in parallel is dictated by the total available current for the array divided by the desired current per LED. Thus, LED arrays can be configured to meet any particular LED driverless luminaire power and efficiency criteria.

The LED system <NUM> has the plurality of driverless luminaires <NUM> electrically connected in series. In particular, a single LED array <NUM>, <NUM>, in each driverless luminaire <NUM> is electrically connected in series with the corresponding LED array <NUM>, <NUM> in the other driverless luminaires <NUM>. To this end, a first LED array <NUM>, in the first driverless luminaire <NUM> is electrically connected in series with the first LED array <NUM> in all the other driverless luminaires <NUM>. In addition, a second LED array <NUM>, in the first driverless luminaire <NUM> is electrically connected in series with the second LED array <NUM> in all the other driverless luminaires <NUM>.

In preferred embodiments, three phase AC power is applied to the power supply unit <NUM>. The AC power may be at any voltage but in typical installations it will be around 480V. While most embodiments will be supplied three phase AC power, because that is often how power is distributed, embodiments may be powered with single phase AC power as explained in more detail below.

In preferred embodiments, the supplied power goes through an EMI filter and then through a bridge rectifier to the main switch. A transformer provides galvanic isolation. Power from the transformer is then rectified to DC via and regulated through a feedback loop consisting of a reference or error amplifier, an optocoupler and a driver signal generator. The power output of the power supply unit <NUM> is constant current DC.

<FIG> shows one embodiment of a power unit <NUM> that receives three-phase AC power and is for use with LED light systems. The power unit <NUM> has multiple channels. In the embodiment shown in <FIG>, the power unit <NUM> has two channels, a first channel <NUM> and a second channel <NUM>. However, other embodiments may have more than two channels and in particular may have three, four or five channels. In yet other embodiments, the power unit <NUM> may have even more than five channels.

As used herein, a "channel" means a current or voltage regulated DC power output with separate cathode and anode terminals. Multiple channels can come from one driver or separate drivers. Separate channels are typically connected to different LED arrays, often with different color LEDs. The channels are controlled independently so their voltage and current levels can be modulated to vary the light intensity of each color LED array, thus varying the total light output spectrum of the luminaire.

When the power supply <NUM> is multi-channel, each channel may be comprised of a number of individual drivers <NUM>. In the embodiment shown in <FIG>, each channel is comprised of three smaller drivers <NUM>. In the embodiment shown in <FIG>, the first channel <NUM> is designed to output <NUM> kilowatts and is comprised of three <NUM>-Watt constant current drivers electrically connected in parallel. The second channel <NUM> is an identical setup. As used herein, the term "driver" means any device that receives the input power and conditions it and outputs either a constant current or constant voltage DC power.

As may be seen in <FIG>, the input to the power supply <NUM> is three phase AC power. In preferred embodiments that use three phase AC power as the input, the power inputs to the constant current drivers may be electrically connected in a delta configuration. In the embodiment shown in <FIG>, the power inputs to the first three constant current drivers are electrically connected in a delta configuration and the power inputs to the second three constant current drivers are electrically connected in a delta configuration.

The Delta or Mesh electrical configuration (Δ) is also known as three phase three wire system (<NUM>-Phase <NUM> Wire). In a Delta (also denoted by Δ) configuration, the starting ends of the three phases or coils are connected to the finishing ends of the coil. Or the starting end of the first coil is connected to the finishing end of the second coil and so on (for all three coils) and it looks like a closed mesh or circuit. In other words, all three coils are connected in series to form a close mesh or circuit. Three wires are taken out from three junctions and all outgoing currents from the junction are assumed to be positive.

In the embodiment shown in <FIG>, the outputs of the first three constant current drivers <NUM> are electrically connected in parallel and the outputs <NUM> of the second three constant current drivers are electrically connected in parallel.

<FIG> shows one embodiment of a power unit <NUM> that receives single phase AC power and is for use with LED light systems. The embodiment in <FIG> is similar to that in <FIG> in that it has two channels <NUM> and <NUM> and each channel is comprised by three drivers <NUM>. However, unlike the embodiment in <FIG>, which is designed for three phase power, the embodiment in <FIG> is designed to accept single phase AC power. To this end, rather than using a delta configuration for the inputs to the drivers, the embodiment in <FIG> electrically connects the power inputs to each of the drivers <NUM> in parallel. As may be seen in <FIG>, the power inputs to the first three constant current drivers <NUM> are connected in parallel and the power inputs to the second three constant current drivers <NUM> are connected in parallel.

The power supply <NUM> or <NUM> may generally run on any input voltage but typically voltages may be <NUM>, <NUM>,<NUM>, <NUM>, <NUM> or 480V.

As may be appreciated, the outputs in <FIG> are connected the same way as the outputs in <FIG>. The outputs of the first three constant current drivers <NUM> are electrically connected in parallel and the outputs <NUM> of the second three constant current drivers are electrically connected in parallel.

In general, to keep electrical installations safe, they should be limited to a maximum voltage of 500V DC on all external electrical wires and cables. Cables/wiring rated to a maximum of 600V are relatively inexpensive and not very bulky. Going to higher voltages increases cable cost as well as risk of shock and fire. It's difficult to design efficient LED arrays below 10V. Since Vf of blue or white LEDs is around <NUM>. 2V, that's only <NUM> LEDs in series. Vf varies slightly from LED to LED due to die manufacturing process variation. Therefore, in order to keep the parallel strings of the LED array as even as possible, it's desirable to have a minimum of <NUM> LEDs in series = 10V per array. This means 500V /10V = <NUM> luminaires max per channel.

Maximum current per channel is dictated by the gauge of cable that's relatively inexpensive and readily available. Keeping the wire gauge above <NUM> AWG is desirable to save costs. That limits max current to about <NUM> amps, especially for long cables. Thus, the maximum power per array is 10V x 10A = 100W. In order to increase the power of each luminaire and still meet all the criteria above, more channels per luminaire may be used. Accordingly, with a three-wire cable interconnect, two channels and 200W per luminaire can be achieved. Three channels on a four-wire cable would provide 300W per luminaire. In some embodiments, the voltage per array could be increased to 20V and the power increased per channel to 200W but that reduces the number of luminaries per 10KW driver to (<NUM>/<NUM>) = <NUM>. For maximum coverage of a <NUM> ft. greenhouse, it is desirable not to reduce the number of driverless luminaires per driver below <NUM> in order to cover the entire row of the <NUM>-foot greenhouse with one driver on one end. Accordingly, the best way to increase the power to the desired 400W per luminaire while still meeting all the other voltage/current requirements above is to add an additional channel.

Luminaires may be electrically connected in series or parallel. In the embodiments herein they are electrically connected in series because it's easier to connect them in a chain/row, smaller gauge wires may be used due to higher voltage, and a lower current is required. The embodiments herein don't use parallel connections because it makes it difficult to connect a large number of luminaires fixtures in a row. In addition, parallel connections would require a high current, which in turn requires large and expensive gauge wires.

In some embodiments, a single <NUM>-Kilowatt driver could be used. However, in preferred embodiments, the power supply includes two, three, four, five or six drivers. Using multiple smaller watt drivers is easier and cheaper than a massive single driver. In preferred embodiments, three 1650W drivers are used.

The most efficient way to run three single phase AC drivers with three phase power is to connect them in delta fashion. This keeps the voltage high per driver and the current low. Drivers typically run more efficiently at higher voltages and the wiring for lower current is smaller and less expensive. Accordingly, the embodiments herein may use three smaller drivers paralleled at the output. This creates a power supply that is easier to design, less expensive to build (than one large driver) and allows the inputs to be connected directly to three phase power.

<FIG> illustrates a schematic view of a plurality of driverless luminaires <NUM> electrically connected to a power supply <NUM>. In the embodiment in <FIG>, the cable connecting the driverless luminaires <NUM> has a first circuit <NUM>, a second circuit <NUM> and a third circuit <NUM>. The first circuit <NUM> is in electrical communication with the first channel of the power supply <NUM>. The power supply <NUM> provides a constant current to the first circuit <NUM>. The second circuit <NUM> is in electrical communication with the second channel of the power supply <NUM>. The power supply provides a constant current to the second circuit <NUM>.

A third circuit <NUM> is in electrical communication with the ground of the power supply and the chassis of each driverless luminaire <NUM> in the plurality of driverless luminaires.

Each driverless luminaire <NUM> in the plurality of driverless luminaires is connected in series such that each driverless luminaire in the plurality of luminaires has a first LED array <NUM> electrically connected in series to the first circuit <NUM> and a second LED array <NUM> electrically connected in series to the second circuit <NUM> and a driverless luminaire ground electrically connected to the third circuit <NUM>.

In a preferred embodiment, the LED system consists of a <NUM>-Kilowatt central power supply unit <NUM> connected to up to <NUM> LED driverless luminaires <NUM> in series fashion. The central power supply unit <NUM> (referred to as a Central Power Pack or CPP) is designed to be a two channel-, constant current LED driver, with each channel supplying up to 500V DC at <NUM> amps. The driverless luminaires <NUM> are connected in series fashion to the CPP <NUM>. In the embodiment shown in <FIG>, all connections between the CCP <NUM> and fixtures <NUM>, 42A and 42B is achieved using a three-wire power cable. One wire for each channel plus a ground. As may be appreciated, for systems with more channels, extra wires in the cable may be used, one extra wire for each channel.

The driverless luminaires <NUM> consist of two sets of the LED arrays, <NUM> and <NUM>. Each LED array <NUM> and <NUM> consists of one or more color LEDs combined to deliver a certain color spectrum. The two LED channels may emit different color spectra such that if the power level to either channel is changed, the emitted spectrum of the LED luminaire changes.

Assuming N number of driverless luminaires in the LED system, where N is an integer greater than two, the driverless luminaires are electrically connected as follows. A first three wire cable <NUM> electrically connects the CPP <NUM> to the first driverless luminaire <NUM>.

On one end of the cable <NUM> a first wire <NUM> connects to the anode (+) terminal for channel one on the CPP <NUM>, a second wire <NUM> connects to the anode (+) terminal of channel two of the CPP <NUM> and wire three <NUM> is connected to the chassis ground.

On the opposite end of this cable <NUM>, the first wire <NUM> is connected to the anode (+) terminal of the channel one LED array <NUM> in the first driverless luminaire <NUM>, the second wire <NUM> is connected to the anode (+) terminal of the channel two LED array <NUM> of the first driverless luminaire <NUM> and the third wire <NUM> is connected to chassis ground of the first driverless luminaire <NUM>.

A second three-wire cable <NUM> electrically connects the first driverless luminaire <NUM> to the second luminaire 42A in the following configuration. On one end of the cable <NUM>, a first wire <NUM> connects to the cathode (-) terminal of the channel one LED array of driverless luminaire <NUM>, a second wire <NUM> connects to the cathode (-) terminal of the channel one LED array of driverless luminaire 42A and the third wire <NUM> connects to chassis ground of driverless luminaire 42B.

On the other end of cable <NUM>, the first wire <NUM> is connected to the Anode (+) terminal of the channel one LED array 43A in driverless luminaire 42A, the second wire <NUM> is connected to the channel two LED array 45A of the driverless luminaire 42A and the third wire <NUM> is connected to chassis ground of the driverless luminaire 42A.

An Nth three-wire cable <NUM> electrically connects driverless luminaire (N-<NUM>) 42A to driverless luminaire N 42B in the following fashion. On one end of the cable <NUM>, the first wire <NUM> connects to the Cathode (-) terminal of the channel one LED array 43A of the N-<NUM> driverless luminaire 42A. A second wire connects to the cathode (-) terminal of the channel <NUM> LED array 45A of the N-<NUM> driverless luminaire 42A and the third wire connects to chassis ground of the N-<NUM> driverless luminaire 42A. On the other end of this cable <NUM>, the first wire <NUM> is connected to the Anode (+) terminal of the channel one LED array 43B in the Nth driverless luminaire 42B, a second wire <NUM> is connected to the channel two LED array 45B of the Nth driverless luminaire 42B and the third wire is connected to chassis ground of the Nth driverless luminaire 42B.

An (N+<NUM>)th three-wire cable <NUM> electrically connects the Nth driverless luminaire 42B back to the CPP <NUM> in the following fashion. On one end of the cable <NUM>, a first wire <NUM> connects to the Cathode (-) terminal of the first channel LED array 43B of Nth driverless luminaire 42B. A second wire connects to the cathode (-) terminal of second channel LED array 45B of the Nth driverless luminaire 42B and the third wire <NUM> connects to chassis ground of Nth driverless luminaire 42B.

On the opposite end of this cable <NUM>, the first wire <NUM> connects to the Cathode (-) terminal for the first channel on the CPP <NUM>. The second wire <NUM> connects to the Cathode (-) terminal of the second channel of the CPP <NUM> and the third wire <NUM> is connected to the chassis ground.

The designs taught herein allow for spectrum control by changing the output light level of each channel independently. <FIG> illustrates one method to achieve this spectrum control using a universal <NUM>-10V control interface.

In <FIG>, the two groups of three drivers in each channel <NUM> and <NUM> are controlled with a two-channel <NUM>-10V controller <NUM>. The <NUM>-10V signals can be generated using a wireless device that generates two-separate <NUM>-10V analog signals. Each <NUM>-10V signal is connected to the input of the <NUM> CLW-CPP-1650W drivers in parallel fashion as shown in <FIG>.

Claim 1:
An LED system (<NUM>) comprising:
a direct current power supply unit (<NUM>) having a first channel (<NUM>) and a second channel (<NUM>) and a chassis ground;
a first circuit (<NUM>) in electrical communication with the first channel (<NUM>) of the direct current power supply unit (<NUM>) wherein the direct current power supply unit (<NUM>) provides a constant current to the first circuit (<NUM>);
a second circuit (<NUM>) in electrical communication with the second channel (<NUM>) of the direct current power supply unit (<NUM>) wherein the direct current power supply unit (<NUM>) provides a constant current to the second circuit (<NUM>);
characterized in that the LED system further comprises:
a third circuit (<NUM>) in electrical communication with the chassis ground of the direct current power supply unit (<NUM>);
a plurality of driverless luminaires connected in series wherein each driverless luminaire (<NUM>) in the plurality of driverless luminaires has a first LED array (<NUM>) electrically connected in series to the first circuit (<NUM>) and a second LED array (<NUM>) electrically connected in series to the second circuit (<NUM>) and a driverless luminaire chassis ground electrically connected to the third circuit (<NUM>).