High-efficiency energy harvesting interface and corresponding energy harvesting system

Patent metadata

Field	Value
Publication number	US-9379615-B2
Application number	US-201514749254-A
Country	US
Kind code	B2
Filing date	Jun 24, 2015
Priority date	Sep 17, 2014
Publication date	Jun 28, 2016
Grant date	Jun 28, 2016

Abstract

An electrical-energy harvesting system envisages a transducer for converting energy from an environmental energy source into a transduced signal, an electrical energy harvesting interface for receiving the transduced signal and for supplying a harvesting signal, and an energy storage element coupled to the electrical energy harvesting interface for receiving the harvesting signal. The electrical-energy harvesting system also includes a voltage converter connected to the electrical energy harvesting interface for generating a regulated voltage. The harvesting interface samples an open-circuit voltage value of the transduced signal, generates an optimized voltage value starting from the open-circuit voltage value, and generates an upper threshold voltage and a lower threshold voltage on the basis of the optimized voltage value. The harvesting interface controls the voltage converter in switching mode so that the harvesting signal has a value between the upper and lower threshold voltages in at least one operating condition.

First claim

The invention claimed is:

1. An electrical-energy harvesting system, comprising:
a transducer to convert energy from an environmental energy source into a transduced signal;
a harvesting interface to receive the transduced signal on an input terminal and to supply an electrical-energy harvesting signal on an output terminal;
an energy storage element coupled to the output terminal of the harvesting interface to receive the electrical-energy harvesting signal;
a voltage converter coupled to the output terminal to generate a regulated voltage, wherein the harvesting interface is configured to:
sample an open-circuit voltage value of the transduced signal;
generate an optimized voltage value starting from the open-circuit voltage value;
generate an upper threshold voltage based on the optimized voltage value;
generate a lower threshold voltage based on the optimized voltage value; and
control the voltage converter in a switching mode to thereby maintain the electrical-energy harvesting signal between the upper and lower threshold voltages in a first operating condition;

a first holding element to store said optimized voltage value;
a second holding element to store said upper threshold voltage;
a third holding element to store said lower threshold voltage during said first operating condition; and
controllable decoupling-switching elements to selectively decouple said first, second, and third holding elements during a storage condition of each respective voltage value.

2. The system according to claim 1 , wherein the harvesting interface is configured to:
couple the output terminal to the input terminal during said first operating condition in a condition of maximum power-point tracking; and
decouple the output terminal from the input terminal during a second operating condition of sampling said open-circuit voltage value; and
generate said upper and lower threshold voltages by said harvesting interface during the second operating condition.

3. The system according to claim 2 , wherein the harvesting interface comprises:
a tracking switch coupled between the input terminal and the output terminal to select said first operating condition or said second operating condition.

4. The system according to claim 3 , wherein the harvesting interface comprises:
a sample-and-hold stage configured, during said second operating condition, to sample the open-circuit voltage value of the transduced signal, with the tracking switch in the open state, and configured to generate the optimized voltage value, the upper threshold voltage, and the lower threshold voltage;
a comparator stage with a hysteretic voltage control based on the upper and lower threshold voltages, the comparator stage configured to generate an enabling signal for the voltage converter to maintain the electrical-energy harvesting signal and, with the tracking switch in the closed state, the transduced signal, between the upper and lower threshold voltages in said first operating condition.

5. The system according to claim 2 , wherein the harvesting interface further comprises:
a timing stage to generate control and timing signals to first determine said first operating condition and then to determine said second operating condition.

6. The system according to claim 5 , wherein said timing stage is configured to:
cyclically determine execution of said second operating condition to direct updating said open-circuit voltage value and said upper and lower threshold voltages and execution of said first operating condition following upon each new execution of said second operating condition.

7. The system according to claim 1 , wherein said optimized voltage value corresponds to a condition of substantially maximum coupling between said transducer and said harvesting interface.

8. The system according to claim 1 , wherein:
VTH DOWN <V MPPT <VTH UP ,
where V MPPT is the optimized voltage value, VTH DOWN is the lower threshold voltage, and VTH UP is the upper threshold voltage.

9. The system according to claim 1 , wherein the harvesting interface comprises
a voltage divider to generate the optimized voltage value starting from a sampled value of said open-circuit voltage, wherein a division factor of said voltage divider is configurable as a function of characteristics of said transducer to correspond said optimized voltage value to a condition of substantially maximum coupling between said transducer and said harvesting interface.

10. The system according to claim 9 , wherein the division factor is substantially equal to 0.5 when the transducer is of a thermoelectric type and wherein the division factor is between about 0.75 and about 0.9 in the case where the transducer is of a photovoltaic type.

11. The system according to claim 1 , wherein the harvesting interface comprises:
a first voltage-generator module to generate said upper threshold voltage starting from said optimized voltage value; and
a second voltage-generator module to generate said lower threshold voltage starting from said optimized voltage value, wherein said upper threshold voltage and said lower threshold voltage differ from said optimized voltage value by a same offset value.

12. An electronic device, comprising:
a transducer to convert energy from an environmental or mechanical energy source into a transduced signal;
a harvesting interface to receive the transduced signal on an input terminal and to supply an electrical-energy harvesting signal on an output terminal;
an energy storage element coupled to the output terminal of the harvesting interface to receive the electrical-energy harvesting signal;
a first holding element to store an optimized voltage generated during a first operating condition;
a second holding element to store an upper threshold voltage;
a third holding element to store a lower threshold voltage;
controllable decoupling-switching elements to selectively decouple said first, second, and third holding elements during a storage condition of each respective voltage value;
a voltage converter coupled to the output terminal to generate a regulated voltage, wherein the harvesting interface is configured to:
control the voltage converter in a switching mode to thereby maintain the electrical-energy harvesting signal between the upper threshold voltage and the lower threshold voltages in the first operating condition;
generate said upper and lower threshold voltages during a second operating condition; and
cyclically execute said first operating condition following upon each new execution of said second operating condition; and

an electrical load to receive the regulated voltage.

13. The electronic device according to claim 12 , wherein said electrical load includes a rechargeable battery.

14. The electronic device according to claim 12 , wherein said transducer includes at least one of a photovoltaic and a thermoelectric device.

15. The electronic device according to claim 12 , wherein said electronic device is a mobile electronic device, an automotive device, an industrial device, or an article of clothing.

16. An electrical-energy harvesting method, comprising:
by a transducer, converting energy from an environmental energy source into a transduced signal;
by a harvesting interface:
receiving the transduced signal on an input terminal;
supplying an electrical-energy harvesting signal on an output terminal;
sampling an open-circuit voltage value of the transduced signal;
generating an optimized voltage value starting from the open-circuit voltage value;
storing the optimized voltage

Assignees

• St Microelectronics Srl

Inventors

• Ramorini Stefano
• Gasparini Alessandro
• Cattani Alberto

Classifications

• H02M3/158 Primary

  including plural semiconductor devices as final control devices for a single load · CPC title

• H02J50/001

  Energy harvesting or scavenging · CPC title

• H02J7/35

  with light sensitive cells · CPC title

• H02M3/02

  without intermediate conversion into AC · CPC title

• H02J7/32 Primary

  for charging batteries from a charging set comprising a non-electric prime mover {rotating at constant speed} · CPC title