Abstract:
A direct current power system according to one non-limiting embodiment includes a direct current power source operable to distribute a direct current voltage throughout at least one structure, and at least one controller operable to selectively couple a direct current load to the direct current voltage in response to a wireless signal from an energy-harvesting switch.

Description:
The application claims priority to U.S. Provisional Application No. 61/042,449 which was filed on Apr. 4, 2008. 
    
    
     BACKGROUND OF THE INVENTION 
     This application relates to power distribution systems, and more particularly to a direct current (“DC”) distribution system. 
     Electrical systems for buildings, such as residential buildings, are designed for alternating current (“AC”) and AC loads. Some loads, however, such as light-emitting diodes (“LEDs”), may require DC to operate. Existing LED lighting solutions have incorporated a substantial amount of electronics in a LED lamp to convert AC to DC to power the LED lamp. Other DC loads require AC adapters plugged into electrical outlets that perform an AC to DC conversion. 
     SUMMARY OF THE INVENTION 
     A DC power system according to one non-limiting embodiment includes a DC power source operable to distribute a DC voltage throughout at least one environment, and at least one controller operable to selectively couple a DC load to the DC voltage in response to a wireless signal from an energy-harvesting switch. 
     A DC lighting system according to one non-limiting embodiment includes a DC power source operable to distribute a DC voltage throughout at least one environment, and at least one controller operable to selectively couple a DC lighting source to the DC voltage in response to a control signal. 
     A method for controlling electrical power in an environment includes converting an AC voltage to a first DC voltage, distributing the DC voltage in an environment, converting the first DC voltage to a second DC voltage, and selectively coupling a DC load to the second DC voltage in response to a control signal. 
     These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  schematically illustrates a first low voltage DC distribution system. 
         FIG. 2  schematically illustrates a second DC distribution system. 
         FIG. 3  schematically illustrates a third DC distribution system. 
         FIG. 4  schematically illustrates a fourth DC distribution system. 
         FIG. 5  schematically illustrates a fifth DC distribution system. 
         FIG. 6   a  schematically illustrates a first wireless switching application. 
         FIG. 6   b  schematically illustrates a second wireless switching application. 
         FIG. 7  schematically illustrates the use of the system of  FIG. 1  across a building. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       FIGS. 1-5  schematically illustrate a plurality of DC distribution systems  10   a - e .  FIG. 1  schematically illustrates a first DC distribution system  10   a  that includes an AC power source  12  and a power converter  14  coupled to the AC power source  12 . The power converter  14  is operable to convert an AC input voltage from the AC power source  12  to a DC voltage. 
     Throughout this application an example AC input voltage of 120 VAC is illustrated. However, it is understood that other AC input voltages could be used. For example, 220 VAC is commonly used in Europe, and could be used with any of the disclosed systems  10   a - e . The power converter  14  supplies power throughout at least one structure (see, e.g.  FIG. 7 ) via a plurality of power lines  26  to a plurality of controllers  16   a - c.    
     Each controller  16  is coupled to at least one DC load  18  via power lines  28 . In one example the DC loads  18  include lighting loads (e.g. luminaires having LEDs). Of course, other DC lighting loads, and other DC non-lighting loads could be used. Also, although  FIG. 1  illustrates a single load  18  coupled to each controller  16 , it is understood that the controller  16  could be a multi-channel controller, and that other quantities of loads  18  could be coupled to each controller  16  (see, e.g.,  FIGS. 6   a - b ). In one example each of the controllers  16   a - c  are operable to receive wireless signal commands from an energy-harvesting switch  32  (see  FIGS. 6   a - b ). 
       FIG. 2  schematically illustrates a second DC distribution system  10   b . Instead of a single power converter  14  as in the system  10   a  of  FIG. 1 , the system  10   b  includes a plurality of power converters  20   a - c . In the context of a structure (e.g. a building), AC voltage may be distributed along power lines  25 . The plurality of power converters  20   a - c  are operable to convert the AC voltage to a DC voltage, and to distribute the DC voltage along power lines  26  to the controllers  16 . The controllers  16   a - c  are operable to distribute the DC voltage via power lines  28  to loads  18   a - c.    
       FIG. 3  schematically illustrates a third DC distribution system  10   c  that includes a first power converter  22  and a plurality of second power converters  24   a - c  coupled to the first power converter  22 . The first power converter  22  is operable to convert an AC input voltage from the AC power source  12  into a first DC voltage, which is distributed along power lines  25 . Although  FIG. 3  illustrates the first DC voltage as being 40 VDC, it is understood that other DC voltages could be used. The plurality of second power converters  24   a - c  are operable to convert the first DC voltage to a second DC voltage that is higher or lower than the first DC voltage. The second DC voltage is distributed along power lines  26  to controllers  16   a - c . The controllers  16   a - c  are operable to distribute the second DC voltage along power lines  28  to loads  18   a - c.    
       FIG. 4  schematically illustrates a fourth DC distribution system  10   d  that includes a DC power source  40 , operable to distribute a first DC voltage along power lines  25 . The DC power source  40  may include, for example, a solar power source, a battery stack or plurality of battery stacks, or an electric generator. A plurality of step down DC converters  42   a - c  are operable to convert the first DC voltage from the DC power source  40  to a second DC voltage that is lower than the first DC voltage, for distribution along power lines  26 . The controllers  16   a - c  are operable to distribute the second DC voltage along power lines  28  to loads  18   a - c . Of course, the step down DC converters  42   a - c  could also be step up DC converters and the second DC voltage could be higher than the first DC voltage. 
       FIG. 5  schematically illustrates a fifth DC distribution system  10   e  that includes a first power converter  23  and a plurality of second power converters  41   a - c  coupled to the first power converter  23 . The first power converter  23  is operable to convert a first AC input voltage from the AC power source  12  into a second AC voltage that is higher or lower than the first AC voltage. The second AC voltage is distributed along power lines  25 . The plurality of second power converters  41   a - c  are operable to convert the second AC voltage to a DC voltage. The DC voltage is distributed along power lines  26  to controllers  16   a - c , which are operable to distribute the DC voltage along power lines  28  to loads  18   a - c.    
       FIG. 6   a  schematically illustrates a first example wireless switching application  30   a . An energy-harvesting switch  32   a  is operable to transmit wireless signals to a receiver  34 , which associated with the controller  16 . However, it is understood that the receiver would not need to be included within the controller  16 , and could be external to the controller  16 . Also, it is understood that the controller  16  could act as a housing for a power converter (e.g. power converter  20 ,  24 , etc.). 
     The controller  16  selectively couples a load  36   a - c  to a power source  38  in response to wireless signals sent from the switch  32   a  to the receiver  34 . The load  36   a  is a lighting load coupled to a first channel of the controller  16 , the load  36   b  is a lighting load coupled to a second channel of the controller  16 , and the load  36   c  is coupled to a third channel of the controller  16 . As in the other examples, it is possible that the controller  16  may be coupled to more or less than three items. One energy-harvesting switch is available from Verve Living Systems Product No. X3100, and one controller is available from Verve Living Systems Product No. X2110. However, it is understood that this specific switch and controller would not need to be used. For example, the energy-harvesting switch  32   a  could correspond to a motion sensor may operable to turn lighting loads  36   a - b  ON or OFF. 
       FIG. 6   b  schematically illustrates a second example wireless switching application  30   b , in which a plurality of loads  43   a - d  are connected in parallel to a first channel of controller  16 ′, a plurality of loads  44   a - b  are connected in parallel to a second channel of controller  16 ′, and a plurality of loads  46   a - c  are connected in parallel to a third channel of controller  16 ′. In this example, the loads  43   a - d ,  44   a - b , and  46   a - c  are addressable so-called “smart loads” capable of two-way communication with the receiver  34 ′. Such addressable functionality enables multiple loads such as the loads  43   a - d  to be controlled individually while connected to a single channel of receiver  16 ′. In one example, the controller  16 ′ communicates with the loads  43 ,  44 ,  46  using a DC powerline carrier signal 
     The systems  10   a - d  of  FIGS. 1-4  are applicable to a variety of environments, such as structures (e.g., residential, commercial, and industrial buildings) or outdoor spaces.  FIG. 7  schematically illustrates a residential building  100  incorporating a plurality of the controllers  16  as set forth in  FIG. 1 , coupled to the plurality of DC loads  18 . An electrical power source  102  supplies power through a plurality of power lines  26  to a plurality of controllers  16 . The electrical power source  102  may correspond to the AC power source  12  and power converter  14  collectively (see  FIG. 1 ), the AC power source  12  on its own (see  FIG. 2 ), the AC power source  12  and the first DC converter  22  collectively (see  FIG. 3 ), the DC power source  40  (see  FIG. 4 ), or the AC power source  12  and power converter  23  (see  FIG. 5 ), for example. 
     The building  100  also includes a power converter  104 , which could correspond to one of the power converters  20  of system  10   b  (see  FIG. 2 ), one of the power converters  24  of system  10   c  (see  FIG. 3 ), one of the step down DC converters  42  of system  10   d  (see  FIG. 4 ), or one of the power converters  41  (see  FIG. 5 ), for example. As shown in  FIG. 6 , it is possible to place the power converter  104  at a central location in the building  100 . 
     Each of the controllers  16  are shown to have power lines  28  communicating with various DC loads  18 , some or all of which may correspond to luminaires including LEDs. If the DC loads  18  include LED lights, use of the systems  10   a - e  enables an individual to economically provide DC power to the LED lights in the residential building  100  while avoiding use of expensive LED lights having built-in power conversion electronics. Of course, as described earlier, other DC loads could be used. Thus, it can be seen that the electrical power source (optionally in conjunction with power converter  104 ) distribute a DC voltage throughout a first portion of the building  100  environment, and the controllers  16  distribute a DC voltage throughout a second portion of the building  100  environment. 
     Receptacles may be coupled to the controllers  16 , which could enable an individual to avoid having to use AC adapters to provide DC to electronic items. Also, “smart plug” receptacles operable to convert DC to AC could also be used to so that only DC wiring would be needed in the structure  100 . 
     Although embodiments of this invention have been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.