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 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, andfor disconnecting the load from the rechargeable power source when the voltage across the photovoltaic panel is above a load turn-off threshold.
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Accused Products
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.
77 Citations
16 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 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. - 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 a load, comprising:
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a connection between the photovoltaic panel and the rechargeable power source for supplying a charging current to the rechargeable power source; means for substantially blocking current flow from the rechargeable power source to the photovoltaic panel upon the condition that the voltage across the photovoltaic panel is less than the voltage across the rechargeable power source by a predetermined amount; and switching means in a connection between the rechargeable power source and the load for disconnecting the load from the rechargeable power source upon the condition that the voltage across the photovoltaic panel is above a load turn-off threshold and for connecting the load to the rechargeable power source upon the condition that the voltage across the photovoltaic panel is below a load turn-on threshold whereby the rechargeable power source can energize the load when the voltage across the photovoltaic panel is below the load turn-on threshold. - View Dependent Claims (13, 14, 15)
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16. 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 connection between the photovoltaic panel and the rechargeable power source for supplying a charging current to the rechargeable power source; means for substantially blocking current flow from the rechargeable power source to the photovoltaic panel upon the condition that the voltage across the photovoltaic panel is less than the voltage across the rechargeable power source by a predetermined amount; and switching means in a connection between the rechargeable power source and the load for disconnecting the load from the rechargeable power source upon the condition that the voltage across the photovoltaic panel is above a threshold and for connecting the load to the rechargeable power source upon the condition that the voltage across the photovoltaic panel is below said threshold whereby the rechargeable power source can energize the load when the voltage across the photovoltaic panel is below said threshold.
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Specification