Control circuit for a solar-powered rechargeable power source and load
DCFirst Claim
1. A circuit for controlling the recharging of a rechargeable power source with a photovoltaic panel and for controlling the discharge of the rechargeable power source into a load, comprising:
- a rechargeable power source;
a photovoltaic panel operably connected to the rechargeable power source for supplying a charging current to the rechargeable power source whenever the voltage across the photovoltaic panel is greater than the voltage across the rechargeable power source by a predetermined amount;
means for substantially blocking current flow from the rechargeable power source to the photovoltaic panel;
a load; and
switching means responsive too the voltage across the photovoltaic panel;
for connecting the load across the rechargeable power source when the voltage across the photovoltaic panel drops below a load turn-on threshold, andfor disconnecting the load from the rechargeable power source when the voltage across the photovoltaic panel is above a load turn-off threshold, wherein said load turn-off threshold is unequal to said load turn-on threshold.
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Abstract
An inexpensive circuit for controlling the recharging of a rechargeable power source by a photovoltaic panel is used for powering a load such as the lamp of a walk light. Using a minimum number of components, the circuit can charge a rechargeable battery anytime sunlight is sufficient to place a potential across the battery that is greater than the present potential of the battery, can sense a decrease in voltage across the photovoltaic panel with diminishing ambient light and energize the load, can prevent the load from being energized when the ambient light level is sufficient to re-charge the battery, can provide positive feedback at turn-on of the load, thereby hastening turn-on and providing hysteresis, can provide for adjusting the hysteresis bands, can shift the turn-on and turn-off thresholds, and can provide an adequate current to guarantee turn-on when using low leakage solar panels. A further embodiment can additionally exhibit hysteresis at load turn-off so that the load does not cycle on and off and can further raise the load turn-off threshold above the level where the battery is substantially discharged, thereby hastening recharging of the battery. A still further embodiment provides temperature compensation for improved performance.
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Citations
30 Claims
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1. A circuit for controlling the recharging of a rechargeable power source with a photovoltaic panel and for controlling the discharge of the rechargeable power source into a load, comprising:
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a rechargeable power source; a photovoltaic panel operably connected to the rechargeable power source for supplying a charging current to the rechargeable power source whenever the voltage across the photovoltaic panel is greater than the voltage across the rechargeable power source by a predetermined amount; means for substantially blocking current flow from the rechargeable power source to the photovoltaic panel; a load; and switching means responsive too the voltage across the photovoltaic panel; for connecting the load across the rechargeable power source when the voltage across the photovoltaic panel drops below a load turn-on threshold, and for disconnecting the load from the rechargeable power source when the voltage across the photovoltaic panel is above a load turn-off threshold, wherein said load turn-off threshold is unequal to said load turn-on threshold. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A circuit for controlling the recharging of a rechargeable power source with a photovoltaic panel and for controlling the discharge of the rechargeable power source into the load, comprising:
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a rechargeable power source; a photovoltaic panel; a load; and switching means responsive to the voltage across the photovoltaic panel; for connecting the load across the rechargeable power source when the voltage across the photovoltaic panel drops below a load turn-on threshold, and for disconnecting the load from the rechargeable power source when the voltage across the photovoltaic panel is above a load turn-off threshold, the switching means consisting essentially of three transistors and a plurality of resistors connected so as to form a dual-threshold voltage sensing circuit. - View Dependent Claims (13, 14, 15, 16)
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17. A circuit for controlling the recharging of a rechargeable power source with a photovoltaic panel and for controlling the discharge of the rechargeable power source into the load, comprising:
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a rechargeable power source; a photovoltaic panel; a load; and switching means responsive to the voltage across the photovoltaic panel; for connecting the load across the rechargeable power source when the voltage across the photovoltaic panel drop below a load turn-on threshold, and for disconnecting the load from the rechargeable power source when the voltage across the photovoltaic panel is above a load turn-off threshold, the switching means consisting essentially of four transistors and a plurality of resistors connected so as to form a dual-threshold voltage sensing circuit. - View Dependent Claims (18, 19, 20, 21)
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22. A solar powered accent light comprising:
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a housing having a top, a bottom, and generally triangular sides, a rechargeable power source located in said housing, a solar panel located on the top side of said housing, said solar panel connected and adapted to charge said rechargeable power source, a lens connected to said housing, a lamp positioned behind said lens, said lamp connected to and adapted to be powered by said rechargeable power source, means for preventing said rechargeable power source from discharging through said solar panel upon the condition that the voltage across said solar panel is less than the voltage across said rechargeable power source, and a switching means connected to said lamp, said solar panel and said rechargeable power source, said switching means responsive to the voltage across said solar panel and cooperable to disconnect said lamp from said rechargeable power source upon the condition that the voltage across said solar panel is at or above a threshold, and said switching means being further operable to connect said lamp to said solar rechargeable power source upon the condition that the voltage across said solar panel is below said threshold, whereby said lamp if powered by said rechargeable power source provides illumination which is visible through said lens. - View Dependent Claims (23, 24, 25, 26)
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27. A solar powered accent light comprising:
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a housing, a solitary mounting stake connectable to said housing for mounting said accent light outdoors in the ground, a lens connected to said housing, a lamp positioned behind said lens, a rechargeable power source located in said housing said rechargeable power source connected and adapted to provide power to said lamp, a solar panel located on an upper side of said housing, said solar panel source connected and adapted to charge said rechargeable power, means for preventing said rechargeable power source from discharging through said solar panel upon the condition that the voltage across said solar panel is less than the voltage across said rechargeable power source, and a switching means connected to said lamp, said solar panel and said rechargeable power source, said switching means responsive to the voltage across said solar panel and operable to disconnect said lamp from said rechargeable power source upon the condition that the voltage across said solar panel is at or above a threshold, and said switching means being further operable to connect said lamp to said rechargeable power source upon the condition that the voltage across said solar panel is below said threshold, whereby said lamp if powered by said rechargeable power source provides illumination which is visible through said lens. - View Dependent Claims (28)
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29. A solar powered accent light comprising:
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a housing, a rechargeable power source located in said housing, a solar panel located on a top side of said housing, said solar panel connected and adapted to charge said rechargeable power source, a lamp adapted to be powered by said rechargeable power source, a lens connected to said housing and covering said lamp said lens having at least one face oriented downward, means for preventing said rechargeable power source from discharging through said solar panel upon the condition that the voltage across said solar panel is less than the voltage across said rechargeable power source, and a switching means connected to said lamp, said solar panel and said rechargeable power source, said switching means responsive to the voltage across said solar panel and operable to disconnect said lamp from said rechargeable power source upon the condition that the voltage across said solar panel is at or above a threshold, and said switching means being further operable to connect said lamp to said rechargeable power source upon the condition that the voltage across said solar panel is bellow said threshold, whereby said lamp if powered by said rechargeable power source provides illumination which is visible through said lens. - View Dependent Claims (30)
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Specification