Converter and method for extracting maximum power from piezo vibration harvester

• US 8,674,663 B2
• Filed: 03/19/2010
• Issued: 03/18/2014
• Est. Priority Date: 03/19/2010
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Ivanov, Vadim V.
• Primary Examiner(s): Tso, Edward
• Assistant Examiner(s): BOATENG, ALEXIS ASIEDUA
• Application Number:
  US12/661,578
• Publication Number:
  US 20110227543A1
• Time in Patent Office: 1,460 Days
• Field of Search: 320/163, 320/140, 320/166, 320/134, 320/127, 320/119, 320/101, 320/136, 320/118, 320/114, 320/115, 320/107, 320/137, 320/103, 320/145
• US Class Current: 320/163
• CPC Class Codes: H02J 7/04 Regulation of charging current or voltage
• CPC Class Codes: H02M 1/007 Plural converter units in cascade push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826
• CPC Class Codes: H02M 7/219 in a bridge configuration
• CPC Class Codes: H02M 7/2195 the switches being synchronously commutated at the same frequency of the AC input voltage
• CPC Class Codes: H02N 2/181 Circuits; Control arrangements or methods
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A system (1-2) for efficiently transferring harvested vibration energy to a battery (6) includes a piezo harvester (2) generating an AC output voltage (V_P(t)) and current (I_PZ(t)) and an active rectifier (3) to produce a harvested DC voltage (V_hrv) and current (I_hrv) which charge a capacitance (C0). An enable circuit (17) causes a DC-DC converter (4) to be enabled, thereby discharging the capacitance into the converter, when a comparator (A0,A1) of the rectifier which controls switches (S1-S4) thereof detects a direction reversal of the AC output current (I_PZ(t)). Another comparator (13) causes the enable circuit (17) to disable the converter (4) when the DC voltage exceeds a threshold (V_REF), thereby causing the capacitance be recharged.

Claims

1. A system for efficiently transferring harvested vibration energy to an energy storage device including:

(a) piezo harvester means for receiving vibration energy and generating an AC output voltage and an AC output current that together constitute the harvested vibration energy;

(b) means for coupling the AC output voltage and AC output current to active rectifier means for rectifying the AC output voltage and AC output current to produce a harvested DC output voltage and a harvested DC output current;

(c) means for conducting the harvested DC output current into a capacitance to charge the capacitance until the harvested DC output voltage reaches a level at which a direction of the AC output current reverses;

(d) means for detecting the direction reversal;

(e) means for enabling a DC-DC converter in response to the detecting to cause discharging of the capacitance into an inductor of the DC-DC converter in response to the direction reversal; and

(f) means for disabling the DC-DC converter in response to a comparison of the harvested DC output voltage with a reference voltage wherein the harvested DC output voltage is less than the reference voltage,

wherein the means for coupling comprise an active rectifier including first and second switches coupled in series between a harvester output conductor and a first reference voltage, third and fourth switches coupled in series between the harvester output conductor and the first reference voltage, a first comparator for controlling the third and fourth switches, and a second comparator for controlling the first and second switches, a first terminal of the piezo harvester being coupled to a junction between the first and second switches and a first input of the first comparator, and a second terminal of the piezo harvester being coupled to a junction between the third and fourth switches and a first input of the second comparator, wherein the first and second comparators control the rectifying of the harvester output current to charge a capacitance coupled between the harvester output conductor and the first reference voltage, and wherein the first and second comparators also generate output signals indicative of direction reversals of the output current of the piezo harvester.

6. An electronic device utilizing the system for efficiently transferring harvested vibration energy to an energy storage device of claim 1 further comprising:

a piezoelectric energy harvester for generating electrical power coupled to an input of the system for efficiently transferring harvested vibration energy;

a energy storage device coupled to an output of the system for efficiently transferring harvested vibration energy; and

an electronic circuit consuming electric power generated by the piezoelectric energy harvester.

2. A system for efficiently transferring harvested vibration energy to an energy storage device including:

(a) piezo harvester means for receiving vibration energy and generating an AC output voltage and an AC output current that together constitute the harvested vibration energy;

(b) means for coupling the AC output voltage and AC output current to active rectifier means for rectifying the AC output voltage and AC output current to produce a harvested DC output voltage and a harvested DC output current;

(c) means for conducting the harvested DC output current into a capacitance to charge the capacitance until the harvested DC output voltage reaches a level at which a direction of the AC output current reverses;

(d) means for detecting the direction reversal;

(e) means for enabling a DC-DC converter in response to the detecting to cause discharging of the capacitance into an inductor of the DC-DC converter in response to the direction reversal; and

(f) means for disabling the DC-DC converter in response to a comparison of the harvested DC output voltage with a reference voltage wherein the harvested DC output voltage is less than the reference voltage,

wherein the means for conducting comprising a DC-DC converter having a first input coupled to the harvester output conductor, a second input coupled to the first reference voltage, and an output for supplying current to an energy storage device, the DC-DC converter including an inductor coupled to the harvester output conductor, a fifth switch coupled to the inductor, and a rectifying device coupled to the inductor.

7. An electronic device utilizing the system for efficiently transferring harvested vibration energy to an energy storage device of claim 2 further comprising:

a piezoelectric energy harvester for generating electrical power coupled to an input of the system for efficiently transferring harvested vibration energy;

a energy storage device coupled to an output of the system for efficiently transferring harvested vibration energy; and

an electronic circuit consuming electric power generated by the piezoelectric energy harvester.

3. A system for efficiently transferring harvested vibration energy to an energy storage device including:

(a) piezo harvester means for receiving vibration energy and generating an AC output voltage and an AC output current that together constitute the harvested vibration energy;

(b) means for coupling the AC output voltage and AC output current to active rectifier means for rectifying the AC output voltage and AC output current to produce a harvested DC output voltage and a harvested DC output current;

(c) means for conducting the harvested DC output current into a capacitance to charge the capacitance until the harvested DC output voltage reaches a level at which a direction of the AC output current reverses;

(d) means for detecting the direction reversal;

(e) means for enabling a DC-DC converter in response to the detecting to cause discharging of the capacitance into an inductor of the DC-DC converter in response to the direction reversal; and

(f) means for disabling the DC-DC converter in response to a comparison of the harvested DC output voltage with a reference voltage wherein the harvested DC output voltage is less than the reference voltage,

wherein the means for determining reversal comprising a third comparator for comparing a voltage on the harvester output conductor with a second reference voltage to determine when to stop discharge of the capacitance into the inductor.

8. An electronic device utilizing the system for efficiently transferring harvested vibration energy to an energy storage device of claim 3 further comprising:

a piezoelectric energy harvester for generating electrical power coupled to an input of the system for efficiently transferring harvested vibration energy;

a energy storage device coupled to an output of the system for efficiently transferring harvested vibration energy; and

an electronic circuit consuming electric power generated by the piezoelectric energy harvester.

4. A system for efficiently transferring harvested vibration energy to an energy storage device including:

(a) piezo harvester means for receiving vibration energy and generating an AC output voltage and an AC output current that together constitute the harvested vibration energy;

(b) means for coupling the AC output voltage and AC output current to active rectifier means for rectifying the AC output voltage and AC output current to produce a harvested DC output voltage and a harvested DC output current;

(c) means for conducting the harvested DC output current into a capacitance to charge the capacitance until the harvested DC output voltage reaches a level at which a direction of the AC output current reverses;

(d) means for detecting the direction reversal;

(e) means for enabling a DC-DC converter in response to the detecting to cause discharging of the capacitance into an inductor of the DC-DC converter in response to the direction reversal; and

(f) means for disabling the DC-DC converter in response to a comparison of the harvested DC output voltage with a reference voltage wherein the harvested DC output voltage is less than the reference voltage,

wherein the means for enabling any circuitry coupled to the outputs of the first and second comparators, respectively, for both starting the discharge of the capacitance into the inductor and causing switching operation of the fifth switch to steer current in the inductor into the energy storage device in response to each direction reversal to substantially eliminate waste of power for recharging the capacitance of the piezo harvester, wherein the enable circuitry operates as a state machine having a first state in which an enable signal generated by the enable circuitry is at a logical “

1”

level to enable the DC-DC converter and a second state wherein the enable signal is at a logical “

0”

level to disable the DC-DC converter, wherein the enable logic circuit switches from the first state to the second state in response to an output of the third comparator going from a “

1”

level to a “

0”

level, and wherein the enable logic circuit switches from the second state to the first state in response to either the output of the first comparator going from a “

1”

level to a “

0”

level or the output of the second comparator going from a “

1”

level to a “

0”

level.

9. An electronic device utilizing the system for efficiently transferring harvested vibration energy to an energy storage device of claim 4 further comprising:

a piezoelectric energy harvester for generating electrical power coupled to an input of the system for efficiently transferring harvested vibration energy;

a energy storage device coupled to an output of the system for efficiently transferring harvested vibration energy; and

an electronic circuit consuming electric power generated by the piezoelectric energy harvester.

5. A system for efficiently transferring harvested vibration energy to a battery including:

(a) piezo harvester means for receiving vibration energy and generating an AC output voltage and an AC output current that together constitute the harvested vibration energy;

(b) means for coupling the AC output voltage and AC output current to active rectifier means for rectifying the AC output voltage and AC output current to produce a harvested DC output voltage and a harvested DC output current, wherein the means for coupling comprise an active rectifier including first and second switches coupled in series between a harvester output conductor and a first reference voltage, third and fourth switches coupled in series between the harvester output conductor and the first reference voltage, a first comparator for controlling the third and fourth switches, and a second comparator for controlling the first and second switches, a first terminal of the piezo harvester being coupled to a junction between the first and second switches and a first input of the first comparator, and a second terminal of the piezo harvester being coupled to a junction between the third and fourth switches and a first input of the second comparator, wherein the first and second comparators control the rectifying of the harvester output current to charge a capacitance coupled between the harvester output conductor and the first reference voltage, and wherein the first and second comparators also generate output signals indicative of direction reversals of the output current of the piezo harvester;

(c) means for conducting the harvested DC output current into a capacitance to charge the capacitance until the harvested DC output voltage reaches a level at which a direction of the AC output current reverses, wherein the means for conducting comprising a DC-DC converter having a first input coupled to the harvester output conductor, a second input coupled to the first reference voltage, and an output for supplying current to a battery, the DC-DC converter including an inductor coupled to the harvester output conductor, a fifth switch coupled to the inductor, and a rectifying device coupled to the inductor;

(d) means for detecting the direction reversal wherein the means for detecting reversal comprising a third comparator for comparing a voltage on the harvester output conductor with a second reference voltage to determine when to stop discharge of the capacitance into the inductor;

(e) means for enabling a DC-DC converter in response to the detecting to cause discharging of the capacitance into an inductor of the DC-DC converter in response to the direction reversal, wherein the means for enabling any circuitry coupled to the outputs of the first and second comparators, respectively, for both starting the discharge of the capacitance into the inductor and causing switching operation of the fifth switch to steer current in the inductor into the battery in response to each direction reversal to substantially eliminate waste of power for recharging the capacitance of the piezo harvester, wherein the enable circuitry operates as a state machine having a first state in which an enable signal generated by the enable circuitry is at a logical “

1”

level to enable the DC-DC converter and a second state wherein the enable signal is at a logical “

0”

level to disable the DC-DC converter, wherein the enable logic circuit switches from the first state to the second state in response to an output of the third comparator going from a “

1”

level to a “

0”

level, and wherein the enable logic circuit switches from the second state to the first state in response to either the output of the first comparator going from a “

1”

level to a “

0”

level or the output of the second comparator going from a “

1”

level to a “

0”

level; and

(f) means for disabling the DC-DC converter in response to a comparison of the harvested DC output voltage with a reference voltage wherein the harvested DC output voltage is less than the reference voltage.

10. An electronic device utilizing the system for efficiently transferring harvested vibration energy to a battery device of claim 5 further comprising:

a piezoelectric energy harvester for generating electrical power coupled to an input of the system for efficiently transferring harvested vibration energy;

a battery coupled to an output of the system for efficiently transferring harvested vibration energy; and

an electronic circuit consuming electric power generated by the piezoelectric energy harvester.