Patent Publication Number: US-2009224681-A1

Title: Hybrid Solar Powered and Grid Powered Lighting System

Description:
FIELD OF THE INVENTION  
     This invention relates to lighting systems, and more particularly to a lighting system that may be powered at any given time by different power sources, including solar power and grid power, and combinations of power from both of these power sources. The lighting system may optionally be configured to include an emergency battery backup power system. 
     BACKGROUND AND SUMMARY OF THE INVENTION  
     There are innumerable commercially available lighting systems that are powered by electricity generated from solar panels, battery systems and grid power sources. Nonetheless, there is an ongoing need for new lighting systems that are operable from different power sources. The present invention is a hybrid lighting system in which a lamp may be alternately powered by electricity originating from a solar panel and conventional grid electric power. The system is configured to utilize power from both the solar power source and the grid power source; depending upon the amount of power available from the solar panel, additional power may be supplied from the grid power source. In one alternative embodiment, the system may include an optional emergency battery backup power source that powers the lamp. 
     The hybrid lighting system according to the present invention may be used in any setting where grid power is available, but is particularly useful where the alternate solar power sources can offer flexibility in how the lamp is powered. The circuitry is configured so that when grid power is available, the lamp may be powered solely by the solar panel, by combined power from both the solar panel and the grid, or from the grid alone. The circuitry minimizes any “flicker” in the lamp when the power sources change or when the proportion of power from one source relative to another changes, to the point where the flicker is not readily visible. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
       The invention will be better understood and its numerous objects and advantages will be apparent by reference to the following detailed description of the invention when taken in conjunction with the following drawings. 
         FIG. 1  is a schematic view of a hybrid lighting system according to the present invention, showing plural lamps, each with a lamp housing, a solar panel, emergency battery backup, grid power supply, the controller and other components. 
         FIG. 2  is a flow chart showing operation of the hybrid lighting system according to the present invention in various modes and with different power sources. 
         FIG. 3  is an exemplary circuit diagram illustrating wiring for a first embodiment of a hybrid lighting system according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED AND ILLUSTRATED EMBODIMENTS  
     One possible arrangement of the components of a hybrid lamp assembly  10  according to the present invention is shown in the  FIG. 1 . Hybrid lamp  10  comprises several different primary components, specifically, one or more lamps  12 , with each lamp  12  preferably contained in a lamp housing  14 , a controller  16 , and the three alternative power sources, namely solar panel  18 , battery backup  20 , which as detailed below is optional and when included is used in emergency situations when grid power is not available, and grid power  22  (represented by the block shown in the figure). Each of these components is described in detail below. It will be appreciated that the design configuration of the components may vary widely from those shown in the figures, and the figures should on that basis be taken as exemplary but not limiting in any manner. 
     The hybrid lamp  10  is preferably a low-voltage lighting system with power for illuminating the lamps  12  provided from three alternative power sources: (a) power from the grid power  22 , which is standard AC line power; (b) power from the solar panel power supply, which is DC; and optionally, (c) power from the emergency battery backup, which is DC. 
     Hybrid lamp assembly  10  is configured so that the light switch  19 , which is electrically connected in a conventional manner to controller  16 , powers and thus illuminates lamp  12  regardless of the status of the sun. Stated another way, the circuitry in controller  16  is configured so that power is supplied to lamp  12  when the circuit defined by the light switch is closed without regard to whether power is being supplied by solar panel  18 . The lamp assembly  10  is operable in several operational modes relating to power supply. The first mode is when grid power is available. In this mode, if there is enough power being generated by the solar panel  18  to fully illuminate the lamp(s)  12 , then no grid power is used and only power from the solar panel is utilized. If there is not enough current being delivered from the solar panel  18 , for instance during the evening hours or otherwise depending on sun position and cloud cover, if additional current is required to power lamp  12 , the additional power is supplied by the grid power  22 . The controller determines the amount of current available from the solar panel  18  and then obtains any additional power needed to illuminate lamps  12  from the grid. If there is no power being generated by the solar panel  18 , for example at night, the lamps are illuminated only by power from the grid. 
     In a preferred embodiment, and as detailed below, the circuitry provided in controller  16  allows lamp  12  to be powered in the first mode with a combination of power from solar panel  18  and grid power  22 . Thus, the power supply for lamp  12  is principally supplied in its entirely by either solar panel  18  when the solar panel is generating enough power for the lamp, or grid power  22  only when no power is available from solar panel  18 , or a combination of power from the solar panel and grid when not enough power is available from the solar panel. As noted, if the grid power  22  is not available, the lamp  12  cannot be powered from solar panel  18 . 
     The variable power arrangement for powering a lamp  12  is shown in the flow chart of  FIG. 2 . If grid power  22  is available and there is sufficient power from solar panel  18  to fully power lamp  12  (or lamps  12 ), the lamp is illuminated (shown in the flow chart with reference number  30 ) solely with power from the solar panel  18 . If there is no grid power  22 , then the lamp will not be illuminated (shown in the flow chart with reference number  33 ) even if solar power is available. If there is power from solar panel  18 , but not enough to fully power lamps  12 , and if there is also power from grid  22 , then the lamps are illuminated with a combination of power supplied from both solar panel  18  and grid  22  (reference number  32 ). If there is no power available from solar panel  18 , but power is available from grid  22 , lamps  12  are powered solely from the grid power source (reference number  34 ). 
     Hybrid lamp assembly  10  includes an indicator  24  that provides a quick visual indication of which power source (i.e., solar panel  18  or grid power  22 , or both) is powering lamp  12  and the relative proportion of power being supplied from solar panel  18  and grid power  22 . As shown in  FIG. 1 , indicator  24  is preferably closely associated with the controller  16  and switch  19 . Although there are many different kinds of indicators that will suffice, the preferred indicator  24  has a single lamp LED that has  2  colored light emitting diodes (LED) in an array (see, e.g., the circuit diagram of  FIG. 3 ) mounted in a convenient and observable position, for example on the controller  16  adjacent the light switch, or on the lamp housing  14 . The color that the indicator lamp is glowing at any particular time when the lamp assembly  10  is in operation provides an indication of the approximate percentage of solar power to the total power being used to illuminate lamp  12 . For example, the LEDs in indicator  24  are preferably red and green. With such an indicator, when only the red LED is illuminated the indicator is red. When only the green LED is illuminated the indicator glows green. When both the red and the green LEDs are illuminated the indicator glows yellow. 
     Continuing with this example, when only the red LED is illuminated and the indicator is thus red, it would indicate that the power from solar panel  18  is providing from about 0 to 25% of the total power being used to power lamp  12 —the balance of the power for lamp  12  is supplied by grid power  22 . When the indicator glows yellow—that is, when both the red and green LEDs are lit, the power from solar panel  18  is from about 25 to 75% of the total power. And when only the green LED is illuminated and the indicator is thus glowing green, the power from solar panel  18  is providing from about 75 to 100% of the total power required to illuminate the lamp  12 —the balance of necessary power being supplied by grid power  22 . 
     Turning now to the circuit diagram of  FIG. 3 , the primary power supply to lamp  12  is regulated to +15 volts DC, and is then combined with the power supplied by solar panel  18  and connected to the high-efficiency (hi-eff) regulated supply, which is set to +12 volts DC to power the lamp  12 . The lamp  12  requires 1 to 2 ampere, depending on the wattage of the particular lamp being used. It will be appreciated that the “primary” power supply based on this circuit configuration is the grid power  22  because grid power is used to make up any deficiency in power supplied by solar panel  18 . 
     The primary supply can be configured for 120/240 volts. The primary and secondary power supplies, including the battery backup power, may be designed to operate at other voltages depending upon the lamps, such as 24 volts. 
     The transformer&#39;s (refer to the circuit diagram of  FIG. 3 ) output is 14 volts RMS, driving a full-wave-bridge rectifier followed by filter capacitors and through a 0.25 ohm current-sense resistor (R 14 ) to a +15 volt 3-terminal regulator coupled by a diode (D 11 ) to the hi-eff supply. D 11  permits the solar panel voltage to rise above +15 volts. 
     In operation, solar-generated current flows from solar panel  18  through diode (D 1 ) to a 0.25 ohm current sense resistor (R 1 ) to a mosfet (U 2 ) to the hi-eff supply. The mosfet (U 2 ) has to turn off faster than the primary supply. Connecting to the transformer secondary, diode (D 6 ) rectifies its output, which is then filtered by capacitor (C 3 ) connected by resistors R 7  and R 8  to the base of transistor (Q 3 ) to turn off the mosfet. This provides a faster turn off preventing light flicker when turning off the primary supply. D 1  protects the solar panel from the +15 volts at low light levels. 
     The hi-eff supply utilizes a 5 amp step-down voltage regulator (U 6 ). The two input capacitors (c 8 , c 9 ) are very low-series resistance to supply the high current at regulator turn on. The inductor transfers its energy to the output at (U 6 ) turn off through diodes D 12  and D 14 . C 6  (180 uf) capacitor stores the energy and reduces the ripple at the output. C 5  (0.01 uf) capacitor feeds back to boost the gate drive to the internal mosfet in U 6 . Resistors (R 20 , R 21 ) form a voltage divider to set the output at +12 volts. 
     When emergency backup power is supplied from backup battery  20 , D 12  isolates it from the hi-eff supply; D 13  prevents feed back from the +12 volts to the backup power. 
     There are two current sense circuits to control the LED indicator described above. Op-amp U 4  equalizes the voltage across R 13  (249 ohm) with the voltage across R 14  (0.25 ohm) sense resistor. This gives a current through Q 4  that represents the current supplied by the primary power supply. This current is added to the current from Q 1  that represents the current supplied by the solar panel  18 . The sum of the two currents from Q 4  and Q 1  represents the total current the lamp  12  is using. This current generates the reference voltage across R 16  and R 15  to set the 25 and 75% solar-current levels represented by the red and green LED. The current from Q 2  represents the solar current and is applied to R 11 , generating a voltage that is compared to the referenced voltage by op-amps Q 5   a  and Q 5   b.  Q 5   a  drives the red LED and Q 5   b  drives the green LED. For example, when solar current powering lamp  12  is from 0% to about 25%, the red is lit. When solar power is from about 75% to 100% of the total power required to illuminate lamp  12 , the green LED is on. And as detailed above, when solar power from panel  18  is providing between about 25 to 75% of the total power, both the red and green LEDs are lit and the indicator lamp glows yellow. 
     As indicated previously, the invention may be optionally configured to operate in a second mode. The second mode occurs when grid power is unavailable, for example when the utility grid is down. In this mode, which is an optional backup operational mode, lamps  12  are illuminated only with power from backup battery  20  (which could be any external 12 volt power source). In the second mode the system will not utilize power from the solar panel  18  even if it is generating power. If the lamp assembly  10  includes a backup battery  20 , the power source from the battery may be activated by either a manual switch or by an automatic relay that activates when grid power  22  is unavailable. With returning reference to the flow chart of  FIG. 2 , if lamp assembly  10  includes an emergency backup battery  20  and if there is no power available from grid  22 , then lamps  12  are fully powered solely from backup battery  20  (reference number  36 ). 
     While the present invention has been described in terms of a preferred embodiment, it will be appreciated by one of ordinary skill that the spirit and scope of the invention is not limited to those embodiments, but extend to the various modifications and equivalents as defined in the appended claims.