Energy harvesting circuit and method

Patent metadata

Field	Value
Publication number	US-9577529-B2
Application number	US-201514858651-A
Country	US
Kind code	B2
Filing date	Sep 18, 2015
Priority date	Sep 18, 2014
Publication date	Feb 21, 2017
Grant date	Feb 21, 2017

Abstract

An energy harvesting circuit is based on a switch mode inductive DC-DC converter circuit. The inductor current is sensed and a duration of an on-time is controlled in dependence on the sensed inductor current. A duration of an overall switching period of the converter circuit is controlled in dependence on an on-time set by a first timing control circuit and input and output voltages. This converter circuit enables independent control of the on-time and a full period of a converter cycle. Very rapid switching can be avoided which can give rise to very high energy consumption. The full cycle period can be set to achieve a desired constant value of an input resistance of the DC-DC converter, and thereby maximize power transfer.

First claim

What is claimed is:

1. An energy harvesting circuit, comprising:
an input configured to receive an input voltage from an energy source to be harvested;
a switch mode inductive DC-DC converter circuit configured to generate an output voltage from the input voltage, wherein the switch mode inductive DC-DC converter circuit includes a timing switch configured to control a switching phase of the switch mode inductive DC-DC converter and an inductor;
a current sensor circuit configured to sense an inductor current;
a first timing control circuit configured to control a duration of on-time of the timing switch in dependence on a sensed inductor current; and
a second timing control circuit configured to control a duration of a period of the switch mode inductive DC-DC converter circuit in dependence on the on-time controlled by the first timing control circuit and the input and output voltages.

2. The energy harvesting circuit of claim 1 , wherein the first timing control circuit sets the on-time as the time taken for the inductor current to reach a predetermined level.

3. The energy harvesting circuit of claim 2 , further comprising a calculating unit configured to calculate the predetermined level of the inductor current in dependence on the input and output voltages.

4. The energy harvesting circuit of claim 1 , wherein the second timing control circuit comprises a capacitor, a first current source configured to charge the capacitor, a switch configured to control a timing during which a first current source current flows to the capacitor, a second current source configured to discharge the capacitor, and a detector configured to detect a voltage of the capacitor and generate a timing signal in dependence on the capacitor voltage.

5. The energy harvesting circuit of claim 4 , wherein the detector comprises a comparator configured to generate a timing pulse when the capacitor voltage reaches a reference value.

6. The energy harvesting circuit of claim 4 , wherein the first current source provides a scaled version of the inductor current and the second current source provides a current proportional to the input voltage.

7. The energy harvesting circuit of claim 6 , wherein the switch mode inductive DC-DC converter comprises a buck converter or a buck-boost converter, and wherein the switch is closed during the on-time of the timing switch of the switch mode inductive DC-DC converter.

8. The energy harvesting circuit of claim 6 , wherein the switch mode inductive DC-DC converter comprises a boost converter, and wherein the switch is closed during an inductor conduction period of the switch mode inductive DC-DC converter.

9. An energy harvesting method, comprising:
providing an input voltage to a switch mode inductive DC-DC converter configured to generate an output voltage from the input voltage, wherein the switch mode inductive DC-DC converter comprises a timing switch configured to control a switching phase of the switch mode inductive DC-DC converter and an inductor,
during each cycle of the switch mode inductive DC-DC converter:
monitoring inductor current to determine when a predetermined level has been reached and responsively ending an on-time of the timing switch;
deriving a desired total DC-DC converter cycle period in dependence on the on-time and on the input and output voltages; and
starting a next on-time of the timing switch after the desired total DC-DC converter cycle period has elapsed.

10. The energy harvesting method of claim 9 , further comprising calculating the predetermined level of the inductor current in dependence on the input and output voltages.

11. The energy harvesting method of claim 9 , wherein deriving the desired total DC-DC converter cycle period comprises:
charging a capacitor with an output of a first current source during a first time period and discharging the capacitor with an output of a second current source during a second time period after the first time period, wherein the second time period is longer than the first time period; and
generating a timing signal in dependence on capacitor voltage.

12. The energy harvesting method of claim 11 , further comprising generating a timing pulse when the capacitor voltage reaches a reference value.

13. The energy harvesting method of claim 11 , wherein the first current source provides a scaled version of the inductor current and the second current source provides a current proportional to the input voltage.

14. The energy harvesting circuit of claim 13 , wherein the switch mode inductive DC-DC converter comprises a buck converter or a buck-boost converter, and wherein the method comprises setting the first time period to correspond to the on-time of the timing switch of the switch mode inductive DC-DC converter.

15. The energy harvesting method of claim 13 , wherein the switch mode inductive DC-DC converter comprises a boost converter, and wherein the method comprises setting the first time period to correspond to an inductor conduction period of the switch mode inductive DC-DC converter.

Assignees

• Stichting Imec Nederland

Inventors

• Stanzione Stefano

Classifications

• H02M2001/0032

  Electricity · mapped topic

• H02M3/156 Primary

  with automatic control of output voltage or current, e.g. switching regulators · CPC title

• H02M3/158 Primary

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

• H02M2001/0048

  Electricity · mapped topic

• H02M1/0032

  Control circuits allowing low power mode operation, e.g. in standby mode · CPC title