Device and relative method for scavenging energy

• US 8,803,342 B2
• Filed: 09/23/2011
• Issued: 08/12/2014
• Est. Priority Date: 11/30/2010
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Bottarel, Valeria, Ricotti, Giulio, Rossi, Sandro
• Primary Examiner(s): Patel, Tulsidas C
• Assistant Examiner(s): NGUYEN, VIET P
• Application Number:
  US13/243,058
• Publication Number:
  US 20120133151A1
• Time in Patent Office: 1,054 Days
• Field of Search: 290/1.R, 310/319
• US Class Current: 290/1.R
• CPC Class Codes: H02K 35/02 with moving magnets and stationary coil systems
• CPC Class Codes: H02K 7/1876 with reciprocating, linearly oscillating or vibrating parts
• CPC Class Codes: H02M 7/217 using semiconductor devices only

Abstract

An energy scavenging device includes an electromagnetic transducer adapted to generate a current in response to accelerations impressed thereto. The device also includes a power switching stage input with the current generated by the electromagnetic transducer, having a network of controlled switches adapted to alternately deliver on output nodes of the switching stage an output current that does not invert its sign and to short-circuit the transducer. There is an output capacitor coupled between the output nodes of the power stage. A controller having a sensor coupled to the electromagnetic transducer is to sense the current flowing therethrough, the controller being adapted to drive the switches of the power stage in order to either short-circuit the electromagnetic transducer or to direct the current flowing through the transducer to charge the output capacitor.

Claims

1. An energy scavenging device, comprising:

an electromagnetic transducer configured to generate a current in response to accelerations impressed thereto;

a power switching stage to be input with current generated by said electromagnetic transducer, and comprising a network of controlled switches and output nodes coupled thereto;

said network of controlled switches configured to alternately deliver to said output nodes an output current that does not invert its sign, and to short-circuit said electromagnetic transducer;

an output capacitor coupled between said output nodes and having first and second terminals; and

a controller having a sensor coupled to said electromagnetic transducer configured to sense current flowing therethrough, said controller configured to drive said network of controlled switches to selectively short-circuit said electromagnetic transducer and direct the current flowing through said electromagnetic transducer to charge said output capacitor;

said power switching stage comprising

a high-side switch and a low-side switch coupled in series to short-circuit said electromagnetic transducer when both closed, and a common terminal between the high-side switch and low-side switch being coupled to said first terminal of said output capacitor, and

a high-side diode and a low-side diode each coupled between said second terminal of the output capacitor and said common terminal of said high-side switch and said low-side switch.

2. An energy scavenging device, comprising:

an electromagnetic transducer responsive to accelerations;

a power switching stage coupled to said electromagnetic transducer;

an output capacitor coupled to said power switching stage and having first and second terminals; and

a controller coupled to said electromagnetic transducer and configured to sense current therein and to drive said power switching stage to selectively short-circuit said electromagnetic transducer and direct current flowing through said electromagnetic transducer to charge said output capacitor;

said power switching stage comprising

a high-side switch and a low-side switch coupled in series to short-circuit said electromagnetic transducer when both closed, and a common terminal between the high-side switch and low-side switch being coupled to said first terminal of said output capacitor, and

a high-side diode and a low-side diode each coupled between said second terminal of the output capacitor and said common terminal of said high-side switch and said low-side switch.

3. The energy scavenging device of claim 2, wherein said power switching stage is configured to alternately deliver an output current that does not invert its sign, and to short-circuit said electromagnetic transducer.

4. A method of scavenging energy using a device comprising an electromagnetic transducer configured to generate a current in response to accelerations impressed thereto, a power switching stage input with current generated by the electromagnetic transducer, a network of controlled switches configured to alternately deliver on output nodes of the power switching stage an output current that does not invert its sign and to short-circuit the electromagnetic transducer, an output capacitor coupled between the output nodes and having first and second terminals, a controller having a sensor coupled to the electromagnetic transducer to sense current flowing therethrough, the controller being configured to drive the switches of the power switching stage, the power switching stage comprising a high-side switch and a low-side switch coupled in series to short-circuit the electromagnetic transducer when both closed, and a common terminal between the high-side switch and low-side switch being coupled to the first terminal of the output capacitor, and a high-side diode and a low-side diode each coupled between the second terminal of the output capacitor and the common terminal of the high-side switch and the low-side switch, the method comprising:

monitoring the current flowing through the electromagnetic transducer using the controller; and

driving the switches of the power switching stage, using the controller, to short-circuit the electromagnetic transducer, and depending on the current, selectively continuing to short-circuit the electromagnetic transducer and directing the current flowing through the electromagnetic transducer to charge the output capacitor until the current through the electromagnetic transducer nullifies.

5. The method of claim 4, further comprising:

comparing a time derivative of the current flowing through the electromagnetic transducer with a null value, using the controller; and

configuring the switches to charge the output capacitor when the time derivative crosses the null value until the current through the electromagnetic transducer nullifies, using the controller.

6. The method of claim 4, further comprising configuring, with a fixed switching frequency, the switches to charge the output capacitor until the current through the electromagnetic transducer nullifies, then to short-circuit the electromagnetic transducer, using the controller.

7. The method of claim 4, further comprising:

comparing the current flowing through the electromagnetic transducer with a non-null threshold, using the controller;

when the current flowing through the electromagnetic transducer exceeds the nonnull threshold, configuring with a fixed switching frequency the switches to charge the output capacitor until the current through the electromagnetic transducer nullifies, then to short-circuit the electromagnetic transducer, using the controller.

8. The method of claim 4, further comprising:

comparing the current flowing through the electromagnetic transducer with a nonnull threshold, using the controller; and

keeping the electromagnetic transducer short-circuited when the current is smaller than the nonnull threshold, and directing the current flowing through the electromagnetic transducer to charge the output capacitor until the current through the electromagnetic transducer nullifies, when the current is larger than the nonnull threshold.