초록 ▼

A device for powering a load from an ambient source of energy is provided. The device includes an energy harvesting device for harvesting energy from the ambient source of energy wherein the rate energy is harvested from the ambient source of energy is below that required for directly powering the l

A device for powering a load from an ambient source of energy is provided. The device includes an energy harvesting device for harvesting energy from the ambient source of energy wherein the rate energy is harvested from the ambient source of energy is below that required for directly powering the load. A storage device is connected to the energy harvesting device. The storage device receives electrical energy from the energy harvesting device and is for storing the electrical energy. A controller is connected to the storage device for monitoring the amount of electrical energy stored in the storage device and for switchably connecting the storage device to the load when the stored energy exceeds a first threshold. The system can be used for powering a sensor and for transmitting sensor data, such as tire pressure.

대표청구항 ▼

What is claimed is: 1. An energy harvesting system, comprising: a wheel; an energy harvesting circuit including a piezoelectric material, said energy harvesting circuit mounted on said wheel, wherein said energy harvesting circuit includes a reactive device having an impedance for storing energy de

What is claimed is: 1. An energy harvesting system, comprising: a wheel; an energy harvesting circuit including a piezoelectric material, said energy harvesting circuit mounted on said wheel, wherein said energy harvesting circuit includes a reactive device having an impedance for storing energy derived from said piezoelectric material, wherein said impedance approximately matches impedance of said piezoelectric material, wherein said energy harvesting circuit further includes a low impedance high capacity storage device having a lower impedance and a higher capacity than said reactive device, wherein said low impedance high capacity storage device is switchably connected to receive charge from said reactive device; and an energy using circuit connected to receive power derived from said energy harvesting circuit, said energy using circuit including a sensor and a transmitter, said transmitter for wirelessly transmitting sensor information. 2. A system as recited in claim 1, further comprising a tire mounted on said wheel, wherein said piezoelectric material is mounted on said tire. 3. A system as recited in claim 2, wherein said sensing module includes a sensor for sensing at least one from the group including tire temperature and tire pressure. 4. A system as recited in claim 1, wherein said energy harvesting circuit includes a rechargeable power supply connected to be charged with electricity derived from said piezoelectric material. 5. A system as recited in claim 1, wherein said energy using circuit includes a micro-controller. 6. A system as recited in claim 1, wherein impedance of said reactive device approximately matches impedance of said piezoelectric material at its operating frequency for efficiently transferring electrical energy from said piezoelectric material to said reactive device. 7. A system as recited in claim 6, wherein said reactive device includes a device separate from said piezoelectric material capacitance. 8. A system as recited in claim 7, wherein said device separate from said piezoelectric material capacitance includes a capacitor. 9. A system as recited in claim 8, wherein said capacitor has a capacitance about equal to said piezoelectric material capacitance. 10. A system as recited in claim 1, wherein said energy harvesting circuit includes a control circuit having a monitoring circuit and a first switch, said monitoring circuit connected for monitoring voltage across said low impedance high capacity storage device and for transferring said electrical energy from said low impedance high capacity storage device to said energy using circuit when said voltage across said low impedance high capacity storage device reaches a specified voltage value. 11. A system as recited in claim 10, wherein said control circuit further includes a monitoring circuit switch, wherein said monitoring circuit switch connects said low impedance high capacity storage device with said energy using circuit when voltage across said low impedance high capacity storage device rises to a first threshold and wherein said first switch disconnects said energy using circuit from ground when voltage across said low impedance high capacity storage device falls below a second threshold. 12. A system as recited in claim 1, wherein said energy harvesting circuit includes a rectifier, wherein said piezoelectric material is connected to said reactive device through said rectifier. 13. A system as recited in claim 1, wherein said reactive device includes a capacitor and wherein said energy harvesting circuit includes a DC-DC converter to transfer charge from said capacitor to said low impedance high capacity storage device. 14. A system as recited in claim 13, wherein said circuit further comprises a second switch connected to a terminal of said capacitor, wherein said second switch enables said DC-DC converter when voltage across said capacitor reaches a third threshold value. 15. A system as recited in claim 14, wherein said third threshold value is a multiple of a turn on voltage of said second switch. 16. A system as recited in claim 15, wherein said multiple is provided by a voltage divider. 17. A system as recited in claim 16, wherein said voltage divider has a total resistance exceeding 10 megohms. 18. A system as recited in claim 14, further comprising a timing capacitor for providing an RC time delay to keep said second switch on while said capacitor discharges. 19. An energy harvesting system, comprising: a substrate; an energy harvesting circuit, wherein said energy harvesting circuit includes a piezoelectric material, a first capacitance, a second capacitance, and a voltage conversion circuit, wherein said voltage conversion circuit is for converting a higher DC voltage to a lower DC voltage, wherein said piezoelectric material is mounted on said substrate, wherein said piezoelectric material has a piezoelectric material capacitance, wherein said second capacitance is about equal to said piezoelectric material capacitance, wherein said first capacitance is substantially larger than said piezoelectric material capacitance, wherein said voltage conversion circuit is switchably connected to provide charge from said second capacitance to said first capacitance; and an energy using circuit connected to receive power derived from said energy harvesting circuit. 20. A system as recited in claim 19, wherein said second capacitance includes a device separate from said piezoelectric material capacitance. 21. A system as recited in claim 20, wherein said device includes a capacitor. 22. A system as recited in claim 21, wherein said capacitor has a capacitance about equal to said piezoelectric material capacitance. 23. A system as recited in claim 19, wherein said voltage conversion circuit includes a DC-DC converter. 24. A system as recited in claim 19, further comprising a rectifier, wherein said rectifier is connected between said piezoelectric material and said voltage conversion circuit. 25. A system as recited in claim 24, wherein said rectifier includes a bridge rectifier. 26. A system as recited in claim 19, wherein said substrate includes a wheel. 27. A system as recited in claim 26, further comprising a tire mounted on said wheel, wherein said piezoelectric material is mounted on said tire.