A self-powered piezoelectric energy harvesting circuit and method

Abstract

The application discloses a self-powered piezoelectric energy capturing circuit and method, relates to the technical field of power supply, and divides the piezoelectric energy capturing step into two steps: firstly, the voltage across the piezoelectric transducer is reversed at the end of the positive half cycle; then, the electric energy of the piezoelectric transducer is extracted at the end of the negative half cycle, so that the output power is not affected by the load, and the energy capturing efficiency is improved. The circuit is composed of basic electronic elements only, and has simple structure and high efficiency. The circuit does not need an external power supply, and the positive half cycle voltage peak value detection module and the negative half cycle voltage peak value detection block can control the duration of the corresponding LC oscillation loop. In particular, the negative half cycle voltage detection module can control the duration of the LC oscillation loop to be 1 / 4 of the oscillation period.

Description

Technical Field

[0001] This invention relates to the field of power supply technology, specifically to a self-powered piezoelectric energy harvesting circuit and method. Background Technology

[0002] With the continuous development of precision electronic equipment and wireless sensor networks, the drawbacks of battery-powered power supply are becoming increasingly apparent. Electromagnetic, electrostatic, and piezoelectric environmental energy harvesting technologies are gaining popularity due to their numerous advantages. Among these, piezoelectric vibration energy harvesting utilizes the piezoelectric effect of piezoelectric materials to convert environmental vibration energy into electrical energy. However, piezoelectric transducers output alternating current (AC), while common small electronic devices require direct current (DC) power. Therefore, an interface circuit with rectification and impedance matching functions needs to be designed between the piezoelectric transducer and the load.

[0003] The most common interface circuit is the full-bridge rectifier circuit. However, due to the parasitic capacitance of the piezoelectric material, a fixed phase difference exists between the voltage and current in this circuit, leading to reactive power generation and significantly reducing energy capture efficiency. Furthermore, the output power of the full-bridge rectifier circuit is greatly affected by the load. Therefore, parallel synchronous switching inductor technology and synchronous charge extraction technology have been proposed. The key to parallel synchronous switching inductor technology is controlling the conduction time of the LC resonant circuit to 1 / 2 of the oscillation period, thereby reducing the phase difference between voltage and current and improving energy capture efficiency. The key to synchronous charge extraction technology is controlling the conduction time of the LC resonant circuit to 1 / 4 of the oscillation period for piezoelectric energy extraction. A significant characteristic of synchronous charge extraction circuits is that their output power is unaffected by the load size. However, most circuits designed based on synchronous charge extraction technology currently have complex structures, low feasibility, and require external power supply, resulting in energy capture efficiency that is even lower than that of the full-bridge rectifier circuit in practical applications. Summary of the Invention

[0004] In view of this, the present invention provides a self-powered piezoelectric energy harvesting circuit and method, which integrates parallel synchronous inductor technology and synchronous charge extraction technology, improves energy harvesting efficiency through voltage multiplication, and the output power of the circuit is not affected by the load size.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: a self-powered piezoelectric energy harvesting circuit, comprising a piezoelectric transducer PEH, a first controllable switch S1, a flip inductor L1, a voltage positive peak detection module U1, a second controllable switch S2, a relay inductor L2, a voltage negative peak detection module U2, a diode D, an energy storage capacitor Cr, and a load RL.

[0006] One end of the piezoelectric transducer PEH, the positive terminal of the positive peak voltage detection module U1, one end of the flip inductor L1, the negative terminal of the negative peak voltage detection module U2, and one end of the second controllable switch S2 are connected.

[0007] The other end of the flip inductor L1 is connected to one end of the first controllable switch S1. The other end of the first controllable switch S1 is grounded.

[0008] The other end of the piezoelectric transducer PEH, the negative terminal of the positive peak voltage detection module, the positive terminal of the negative peak voltage detection module U2, one end of the relay inductor L2, and the negative terminal of the energy storage capacitor Cr are all grounded.

[0009] The other end of the second controllable switch S2, the other end of the relay inductor L2, and the positive terminal of the diode D are connected. The negative terminal of the diode D, the positive terminal of the energy storage capacitor Cr, and one end of the load RL are connected. The other end of the load RL is grounded.

[0010] Further, the positive peak voltage detection module U1 includes a first PNP transistor T1, a first NPN transistor T2, and a detection capacitor. The negative peak voltage detection module U2 includes a second PNP transistor T3, a second NPN transistor T4, and a detection capacitor. The positive peak voltage detection module and the negative peak voltage detection module share the same detection capacitor Cdet. The first PNP transistor T1 constitutes a first controllable switch S1, and the second NPN transistor T4 constitutes a second controllable switch. One end of the piezoelectric transducer PEH, one end of the detection capacitor, and the emitter of the second NPN transistor T4 are connected. The base of the first PNP transistor T1 is connected to the collector of the first NPN transistor T2. The emitter of the first NPN transistor T2, the other end of the detection capacitor, and the emitter of the second PNP transistor T3 are connected. The collector of the second PNP transistor T3 is connected to the base of the second NPN transistor T4. The collector of the second NPN transistor T4, one end of the relay inductor L2, and the anode of the diode D are connected. The other end of the diode D, one end of the energy storage capacitor Cr, and one end of the load RL are connected. The other end of the piezoelectric transducer PEH, the collector of the first PNP transistor T1, the base of the first NPN transistor T2, the base of the second PNP transistor T3, the other end of the relay inductor L2, the other end of the energy storage capacitor Cr, and the other end of the load are all grounded.

[0011] Another embodiment of the present invention provides a self-powered piezoelectric energy harvesting method, which uses the above-mentioned self-powered piezoelectric energy harvesting circuit to perform periodic piezoelectric energy harvesting, with one cycle divided into a positive half-cycle and a negative half-cycle.

[0012] During the positive half-cycle, the voltage at pin 1 of the piezoelectric transducer PEH is higher than the voltage at pin 2. When the voltage at pin 1 reaches its peak value, the first PNP transistor T1 is turned on, and the piezoelectric transducer PEH, the flip inductor L1, and the first PNP transistor T1 form an LC oscillation circuit. Due to the reverse cutoff effect of the first PNP transistor, after 1 / 2 oscillation cycle, the current cannot flow in the reverse direction, and the voltage across the piezoelectric transducer PEH is flipped.

[0013] During the negative half-cycle, the voltage at pin 2 of the piezoelectric transducer PEH is higher than that at pin 1. When the voltage at pin 2 reaches its peak, the second NPN transistor T4 turns on, and the piezoelectric transducer PEH, the relay inductor L2, and the second NPN transistor T4 form an LC oscillation circuit. The voltage across the piezoelectric transducer PEH and Cdet gradually decreases, and the current in the relay inductor gradually increases. After 1 / 4 of the oscillation cycle, the voltage across the detection capacitor Cdet is less than the emitter turn-on voltage of the second PNP transistor T3, and the second PNP transistor T3 and the second NPN transistor T4 turn off. At this time, all the electrical energy on the piezoelectric transducer PEH is converted into magnetic energy and stored in the relay inductor L2, and the current in the relay inductor L2 reaches its maximum value. After that, the current in the relay inductor L2 flows through the diode D to the energy storage capacitor Cr and the load RL, thereby realizing the capture of piezoelectric energy.

[0014] Beneficial effects:

[0015] The advantage of this invention is that it divides the piezoelectric energy capture process into two steps: first, at the end of the positive half-cycle, the voltage across the piezoelectric transducer is flipped; then, at the end of the negative half-cycle, the electrical energy of the piezoelectric transducer is extracted. This not only ensures that the output power is unaffected by the load but also improves the energy capture efficiency. The circuit consists of only basic electronic components, making it simple and efficient. This circuit requires no external power supply; the positive half-cycle voltage peak detection module and the negative half-cycle voltage peak detection block can control the duration of the corresponding LC oscillation circuit. In particular, the negative half-cycle voltage detection module can control the duration of the LC oscillation circuit to 1 / 4 of the oscillation period. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the self-powered piezoelectric energy harvesting circuit of the present invention.

[0017] Figure 2 This is a detailed circuit diagram of the self-powered piezoelectric energy harvesting circuit of the present invention. Detailed Implementation

[0018] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0019] like Figure 1As shown, a self-powered piezoelectric energy harvesting circuit includes a piezoelectric transducer PEH, a first controllable switch S1, a flip-flop inductor L1, a positive peak voltage detection module U1, a second controllable switch S2, a relay inductor L2, a negative peak voltage detection module U2, a diode D, an energy storage capacitor Cr, and a load RL. One end of the piezoelectric transducer PEH, the positive terminal of the positive peak voltage detection module U1, one end of the flip-flop inductor L1, the negative terminal of the negative peak voltage detection module U2, and one end of the second controllable switch S2 are connected. The other end of inductor L1 is connected to one end of the first controllable switch S1. The other end of the piezoelectric transducer PEH, the negative terminal of the positive peak voltage detection module U1, the other end of the first controllable switch S1, the positive terminal of the negative peak voltage detection module U2, one end of the relay inductor L2, the negative terminal of the energy storage capacitor Cr, and one end of the load RL are all grounded. The other end of the second controllable switch S2, the other end of the relay inductor L2, and the positive terminal of the diode D are connected. The negative terminal of the diode D, the positive terminal of the energy storage capacitor Cr, and the other end of the load RL are connected.

[0020] like Figure 2 As shown, the positive peak voltage detection module U1 includes a first PNP transistor T1, a first NPN transistor T2, and a detection capacitor Cdet. The negative peak voltage detection module U2 includes a second PNP transistor T3, a second NPN transistor T4, and a detection capacitor Cdet. The positive and negative peak voltage detection modules share the same detection capacitor Cdet. The first PNP transistor T1 forms a first controllable switch S1, and the second NPN transistor T4 forms a second controllable switch S2. One end of the piezoelectric transducer PEH, one end of the detection capacitor Cdet, and the emitter of the second NPN transistor T4 are connected. The base of the first PNP transistor T1 is connected to the collector of the first NPN transistor T2. The emitter of the first NPN transistor T2, the other end of the detection capacitor Cdet, and the emitter of the second PNP transistor T3 are connected. The collector of the second PNP transistor T3 is connected to the base of the second NPN transistor T4. The collector of the second NPN transistor T4, one end of the relay inductor L2, and the anode of the diode D are connected. The other end of the diode D, one end of the energy storage capacitor Cr, and one end of the load RL are connected. The other end of the piezoelectric transducer PEH, the collector of the first PNP transistor T1, the base of the first NPN transistor T2, the base of the second PNP transistor T3, the other end of the relay inductor L2, the other end of the energy storage capacitor Cr, and the other end of the load RL are all grounded.

[0021] The present invention also provides a method for periodic piezoelectric energy harvesting using the above-mentioned self-powered piezoelectric energy harvesting circuit, wherein one cycle is divided into a positive half-cycle and a negative half-cycle, and its specific working principle is as follows:

[0022] During the positive half-cycle, the voltage at pin 1 of the piezoelectric transducer PEH is higher than the voltage at pin 2. When the voltage at pin 1 reaches its peak, the first PNP transistor T1 turns on, and the piezoelectric transducer PEH, the switching inductor L1, and the first PNP transistor T1 form an LC oscillation circuit. Due to the reverse cutoff effect of the first PNP transistor, after 1 / 2 oscillation cycle, the current cannot flow in the reverse direction, and the voltage across the piezoelectric transducer PEH completes its flip.

[0023] During the negative half-cycle, the voltage at pin 2 of the piezoelectric transducer PEH is higher than the voltage at pin 1. When the voltage at pin 2 reaches its peak, the second NPN transistor T4 turns on, and the piezoelectric transducer PEH, the relay inductor L2, and the second NPN transistor T4 form an LC oscillation circuit. The voltage across the piezoelectric transducer PEH and Cdet gradually decreases, while the current in the relay inductor gradually increases. After 1 / 4 of the oscillation cycle, the voltage across the detection capacitor Cdet is less than the emitter turn-on voltage of the second PNP transistor T3, and the second PNP transistor T3 and the second NPN transistor T4 turn off. At this time, all the electrical energy in the piezoelectric transducer PEH is converted into magnetic energy and stored in the relay inductor L2, and the current in the relay inductor L2 reaches its maximum value.

[0024] Subsequently, the current in the relay inductor L2 flows through the diode D to the energy storage capacitor Cr and the load RL, thereby realizing the capture of piezoelectric energy.

[0025] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A self-powered piezoelectric energy harvesting circuit, characterized in that, It includes a piezoelectric transducer PEH, a first controllable switch S1, a flip-flop inductor L1, a positive peak voltage detection module U1, a second controllable switch S2, a relay inductor L2, a negative peak voltage detection module U2, a diode D, an energy storage capacitor Cr, and a load RL; The first pin (1) of the piezoelectric transducer PEH, the positive terminal of the positive peak voltage detection module U1, one end of the flip inductor L1, the negative terminal of the negative peak voltage detection module U2, and one end of the second controllable switch S2 are connected. The other end of the flip inductor L1 is connected to one end of the first controllable switch S1; the other end of the first controllable switch S1 is grounded. The second pin (2) of the piezoelectric transducer PEH, the negative terminal of the positive peak voltage detection module, the positive terminal of the negative peak voltage detection module U2, one end of the relay inductor L2, and the negative terminal of the energy storage capacitor Cr are all grounded. The other end of the second controllable switch S2, the other end of the relay inductor L2, and the positive terminal of the diode D are connected. The negative terminal of the diode D, the positive terminal of the energy storage capacitor Cr, and one end of the load RL are connected. The other end of the load RL is grounded. The voltage positive peak detection module U1 includes a first PNP transistor T1, a first NPN transistor T2, and a detection capacitor; The voltage negative peak detection module U2 includes a second PNP transistor T3, a second NPN transistor T4, and a detection capacitor; The positive peak voltage detection module and the negative peak voltage detection module share the same detection capacitor Cdet; The first PNP transistor T1 constitutes the first controllable switch S1, and the second NPN transistor T4 constitutes the second controllable switch; One end of the piezoelectric transducer PEH, one end of the detection capacitor, and the emitter of the second NPN transistor T4 are connected, and the base of the first PNP transistor T1 is connected to the collector of the first NPN transistor T2. The emitter of the first NPN transistor T2, the other end of the detection capacitor, and the emitter of the second PNP transistor T3 are connected; The collector of the second PNP transistor T3 is connected to the base of the second NPN transistor T4; The collector of the second NPN transistor T4, one end of the current relay inductor L2, and the positive terminal of the diode D are connected; The other end of the diode D, one end of the energy storage capacitor Cr, and one end of the load RL are connected; The other end of the piezoelectric transducer PEH, the collector of the first PNP transistor T1, the base of the first NPN transistor T2, the base of the second PNP transistor T3, the other end of the relay inductor L2, the other end of the energy storage capacitor Cr, and the other end of the load are all grounded.

2. A self-powered piezoelectric energy harvesting method, characterized in that, The self-powered piezoelectric energy harvesting circuit as described in claim 1 is used for periodic piezoelectric energy harvesting, and one cycle is divided into a positive half-cycle and a negative half-cycle. During the positive half-cycle, the voltage at pin 1 of the piezoelectric transducer PEH is higher than the voltage at pin 2. When the voltage at pin 1 reaches its peak value, the first PNP transistor T1 is turned on, and the piezoelectric transducer PEH, the flip inductor L1, and the first PNP transistor T1 form an LC oscillation circuit. Due to the reverse cutoff effect of the first PNP transistor, after 1 / 2 oscillation cycle, the current cannot flow in the reverse direction, and the voltage across the piezoelectric transducer PEH is flipped. During the negative half-cycle, the voltage at pin 2 of the piezoelectric transducer PEH is higher than that at pin 1. When the voltage at pin 2 reaches its peak, the second NPN transistor T4 turns on, and the piezoelectric transducer PEH, the relay inductor L2, and the second NPN transistor T4 form an LC oscillation circuit. The voltage across the piezoelectric transducer PEH and Cdet gradually decreases, and the current in the relay inductor gradually increases. After 1 / 4 of the oscillation cycle, the voltage across the detection capacitor Cdet is less than the emitter turn-on voltage of the second PNP transistor T3, and the second PNP transistor T3 and the second NPN transistor T4 turn off. At this time, all the electrical energy on the piezoelectric transducer PEH is converted into magnetic energy and stored in the relay inductor L2, and the current in the relay inductor L2 reaches its maximum value. After that, the current in the relay inductor L2 flows through the diode D to the energy storage capacitor Cr and the load RL, thereby realizing the capture of piezoelectric energy.

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