A scalable piezoelectric vibration energy harvesting interface circuit based on RC differentiation

Abstract

This invention discloses a scalable piezoelectric vibration energy harvesting interface circuit based on RC differentiation. It features at least one piezoelectric energy harvesting unit, an NMOS transistor, a PMOS transistor, an inductor, a first diode, a second diode, an energy storage capacitor, and a load resistor. Each piezoelectric energy harvesting unit includes a piezoelectric transducer, an RC differentiation module, and a peak detection module. The RC differentiation module includes a first capacitor and a first resistor, and the peak detection module includes a second capacitor, a first PNP transistor, a first NPN transistor, a second NPN transistor, and a second PNP transistor. The advantages are that the current flow direction remains consistent throughout the entire energy harvesting cycle, eliminating inductor usage conflicts and allowing for on-demand expansion of the piezoelectric energy harvesting unit. When multiple piezoelectric energy harvesting units are present, the control of the NMOS and PMOS transistors by the RC differentiation module in each unit achieves a reduction in the number of internal switching transistors and multiplexing of MOS transistors.

Description

Technical Field

[0001] This invention relates to an energy harvesting interface circuit, and more particularly to a scalable piezoelectric vibration energy harvesting interface circuit based on RC differential. Background Technology

[0002] Under the same excitation, the amount of energy that the circuit can provide to the load is an important indicator of the energy harvesting interface circuit. Currently, the most common energy harvesting interface circuits are synchronous charge extraction circuits and synchronous switching inductor circuits. Although the synchronous charge extraction circuit does not have the problem of load dependence, it has a relatively small maximum output power due to the two-stage energy transfer. On the other hand, the series synchronous switching inductor circuit directly transfers the electrical energy accumulated by the piezoelectric transducer to the load end through CLC resonance and increases the initial voltage across the piezoelectric transducer. Its maximum output power is significantly better than that of the synchronous charge extraction circuit.

[0003] In a series synchronous switching inductor circuit, the synchronous switch closes only when the piezoelectric oscillator displacement reaches its extreme value. Energy is extracted to the inductor and energy storage capacitor over 1 / 4 of a CLC resonant cycle, and then transferred to the energy storage capacitor and the parasitic capacitance of the piezoelectric element over another 1 / 4 of a CLC resonant cycle. This increases the initial voltage of the piezoelectric element and the captured energy. However, in traditional series synchronous switching inductor circuits, the inductor current directions are opposite in the positive and negative half-cycles. When using a single inductor or multiple piezoelectric extensions, the inductor can only be time-division multiplexed. When multiple piezoelectric units reach their peak values ​​simultaneously and require energy extraction, positive and negative charges cancel each other out, reducing the capture efficiency. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a scalable piezoelectric vibration energy harvesting interface circuit based on RC differentiation with a small number of switching transistors, which realizes the reuse of MOS transistors and has a relatively simple overall structure.

[0005] The technical solution adopted by this invention to solve the above-mentioned technical problems is as follows: a scalable piezoelectric vibration energy harvesting interface circuit based on RC differentiation, comprising at least one piezoelectric energy harvesting unit, an NMOS transistor, a PMOS transistor, an inductor, a first diode, a second diode, an energy storage capacitor, and a load resistor. Each piezoelectric energy harvesting unit includes a piezoelectric transducer, an RC differentiation module, and a peak detection module. The RC differentiation module includes a first capacitor and a first resistor. The peak detection module includes a second capacitor, a first PNP transistor, a first NPN transistor, a second NPN transistor, and a second PNP transistor. The positive terminal of the piezoelectric transducer, one end of the first capacitor, the base of the first PNP transistor, the collector of the first NPN transistor, the base of the second NPN transistor, and the collector of the second PNP transistor are connected. The other end of the first capacitor, one end of the first resistor, the gate of the NMOS transistor, and the gate of the PMOS transistor are connected. The emitter of the PNP transistor, the emitter of the second NPN transistor, and one end of the second capacitor are connected. The collector of the first PNP transistor is connected to the base of the first NPN transistor. The collector of the second NPN transistor is connected to the base of the second PNP transistor. The emitter of the first NPN transistor, one end of the inductor, and the cathode of the first diode are connected. The other end of the inductor, one end of the energy storage capacitor, and one end of the load resistor are connected. The emitter of the second PNP transistor, the other end of the energy storage capacitor, the other end of the load resistor, and the anode of the second diode are connected. The anode of the first diode is connected to the source of the NMOS transistor. The cathode of the second diode is connected to the source of the PMOS transistor. The negative terminal of the piezoelectric transducer, the other end of the first resistor, the other end of the second capacitor, the drain of the NMOS transistor, and the drain of the PMOS transistor are all grounded.

[0006] The number of piezoelectric energy harvesting units is five. The number of switches in the piezoelectric energy harvesting units is multiplexed by controlling the NMOS and PMOS transistors through the RC differentiating module, which reduces the number of switches by half compared to previous inventions. Based on the use of a single inductor, the number of components in the expanded circuit is further reduced, thus further reducing the size.

[0007] Compared with existing technologies, the advantages of this invention are that the current flow direction remains consistent throughout the entire energy harvesting cycle, eliminating the problem of inductor usage conflicts and the need for time-division multiplexing of a single inductor. This allows for on-demand expansion of the piezoelectric energy harvesting unit, adapting to the energy differences required by different application scenarios through simple unit accumulation. When multiple piezoelectric energy harvesting units are available, the control of NMOS and PMOS transistors by the RC differentiating module in each piezoelectric energy harvesting unit achieves a reduction in the number of internal switching transistors and multiplexing of MOS transistors, making it more suitable for powering small-sized, low-power wireless sensor nodes.

[0008] Energy capture is divided into four stages. First, the piezoelectric transducer is in a oscillating state. During the positive half-cycle, the piezoelectric transducer begins to move from the zero displacement point to the positive maximum displacement point. The peak detection module detects the voltage of the parasitic capacitance and the second capacitor of the piezoelectric transducer. When the piezoelectric transducer reaches the positive maximum displacement point, the voltage of the parasitic capacitance and the second capacitor also reaches their maximum. Then, the piezoelectric transducer begins to move in the opposite direction and reverse-charges its parasitic capacitance. When the voltage difference between the second capacitor and the parasitic capacitance reaches the emitter-base conduction voltage drop of the first PNP transistor, the peak detection module generates a signal to turn on the first NPN transistor. The RC differentiating module composed of the first resistor and the first capacitor also generates a signal to turn on the PMOS transistor. Then, the parasitic capacitance, inductance, and energy storage capacitor of the piezoelectric transducer form a CLC resonant circuit. After 1 / 4 of a CLC resonant cycle, the electrical energy converted by the piezoelectric transducer is transferred to the inductor and the energy storage capacitor. After another 1 / 4 of a resonant cycle, the energy stored in the inductor is also transferred. The energy is transferred to the negative terminal of the energy storage capacitor and the piezoelectric transducer, increasing the initial voltage of the piezoelectric transducer during the negative half-cycle, which is beneficial to improving the energy conversion efficiency during the negative half-cycle. During the negative half-cycle, the piezoelectric transducer continues to move towards the negative maximum displacement point, accumulating charge on the parasitic capacitance and the second capacitor. When the displacement reaches the extreme value, the accumulated charge also reaches its maximum. At this time, the peak detection module continues to detect the voltage, and the magnitude becomes negative. Subsequently, the piezoelectric transducer begins to move in the positive direction, gradually reducing the parasitic capacitance voltage again, until the peak detection module detects that the base-emitter voltage difference of the second NPN transistor reaches the voltage drop of the conducting transistor, generating a signal to turn on the second PNP transistor. The RC differentiating module generates a positive pulse signal opposite to that of the positive half-cycle, turning on the NMOS transistor. This causes the parasitic capacitance, inductance, and energy storage capacitor of the piezoelectric transducer to form a CLC resonant circuit again. Similarly, after 1 / 2 resonant cycle, the energy converted from the reverse movement is transferred to the energy storage capacitor and the positive terminal of the piezoelectric transducer. Attached Figure Description

[0009] Figure 1 This is a circuit topology diagram of the present invention;

[0010] Figure 2 This is the circuit schematic diagram for Example 1;

[0011] Figure 3 This is a schematic diagram of the circuit structure for Example 2. Detailed Implementation

[0012] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0013] Example 1: As Figure 1 , Figure 2 As shown, a scalable piezoelectric vibration energy harvesting interface circuit based on RC differentiation includes a piezoelectric energy harvesting unit and an NMOS transistor. Mn PMOS transistor Mp ,inductance L First diode Dn Second diode Dp Energy storage capacitor Cr and load resistance RL The piezoelectric energy acquisition unit includes a piezoelectric transducer (PZT), an RC differentiating module, and a peak detection module. The RC differentiating module includes a first capacitor. C der and the first resistor R der The peak detection module includes a second capacitor. C det First PNP tube Q 1 First NPN transistor Q 2 Second NPN transistor Q 3 Second PNP tube Q 4 The positive terminal of the piezoelectric transducer PZT and the first capacitor C der One end, the first PNP tube Q 1 The base of the first NPN transistor Q 2 collector, second NPN transistor Q 3 The base and the second PNP transistor Q 4 collector connection, first capacitor C der The other end, the first resistor R der One end, NMOS transistor Mn Gate and PMOS transistor Mp The gate connection of the first PNP transistor Q 1 emitter, second NPN transistorQ 3 emitter and second capacitor C det One end is connected to the first PNP tube. Q 1 collector and first NPN transistor Q 2 The base connection, the second NPN transistor Q 3 collector and second PNP transistor Q 4 The base connection of the first NPN transistor Q 2 emitter, inductor L one end and the first diode Dn The negative terminal is connected to the inductor. L The other end, energy storage capacitor Cr one end and load resistor RL One end is connected to the second PNP tube. Q 4 emitter, energy storage capacitor Cr The other end, load resistor RL The other end and the second diode Dp The positive terminal is connected to the first diode. Dn The positive electrode and the NMOS transistor Mn The source connection, the second diode Dp negative electrode and PMOS transistor Mp The source connection, the negative terminal of the piezoelectric transducer PZT, and the first resistor R der The other end, the second capacitor C det The other end, NMOS transistor Mn drain and PMOS transistor Mp The drains of all terminals are grounded.

[0014] The working principle of the above embodiments is as follows: The piezoelectric transducer PZT converts the vibration energy in the environment into alternating current energy. During the positive half-cycle, the piezoelectric transducer PZT moves from the zero displacement point to the positive displacement extreme value. At the same time, due to the positive piezoelectric effect, the piezoelectric transducer PZT accumulates charge on both ends of the parasitic capacitor and is positively charged, while also charging the second capacitor. C det During charging, when the piezoelectric transducer PZT is displaced to its maximum positive displacement, the parasitic capacitance and the second capacitance inside the piezoelectric transducer PZT... C det When the open-circuit voltage across the two ends reaches its maximum value, the piezoelectric transducer PZT then shifts in the opposite direction, reverse-charging the parasitic capacitance of the piezoelectric transducer PZT, thus reducing the open-circuit voltage of the piezoelectric transducer PZT. Voc It started to drop, the second capacitor C det The voltage across the two ends is due to the first PNP transistor Q 1 The presence of forward conduction voltage drop and the second NPN transistor Q 3 The reverse bias remains constant when the second capacitor C det The voltage across the terminals is greater than the open-circuit voltage of the piezoelectric transducer (PZT). V oc Just above the first PNP tube Q 1 When the forward voltage drop occurs, a peak detection signal is generated, causing the first NPN transistor to... Q 2 When the PMOS transistor is turned on, the RC differentiating module generates a negative differential pulse signal, causing the PMOS transistor to conduct. Mp The second diode is conducting. Dp This is used to offset the PMOS transistor. Mp Parasitic diodes, parasitic capacitance of PZT piezoelectric transducers C p With the first NPN transistor Q 2 collector-emitter, inductor L Energy storage capacitor Cr Second diode Dp PMOS transistor Mp The source and drain form a CLC resonant circuit, and the second capacitor C det With the first PNP tube Q 1 Emitter-collector, first NPN transistor Q 2 Base-emitter, inductor L Energy storage capacitor Cr Second diode Dp PMOS transistor Mp The source-drain junction also forms a CLC resonant circuit; after 1 / 4 of a resonant cycle, the parasitic capacitance accumulated in the piezoelectric transducer PZT will be... C p Energy is transferred from the inductor L With energy storage capacitor Cr Above, inductor L The current in the inductor gradually increases until it reaches its maximum value; after another quarter of a resonant cycle, the current stored in the inductor will be... L Energy is transferred to the energy storage capacitor. CrThis is achieved by increasing the initial voltage of the piezoelectric transducer PZT during the negative half-cycle operation, which is beneficial for improving the energy conversion efficiency during the negative half-cycle. Then, the piezoelectric transducer PZT continues to move in the opposite direction. When the piezoelectric transducer PZT reaches its maximum reverse displacement point, the parasitic capacitance of the piezoelectric transducer PZT... C p Second capacitor C det The charge accumulated at both ends reaches its maximum, and compared to the positive half-cycle, only the polarity of the capacitor ends is reversed; the piezoelectric transducer PZT then shifts again in the positive direction, causing the charge generated by the vibration conversion to affect the parasitic capacitance. C p The original charge was partially neutralized, while the second capacitor C det The voltage across the two ends is due to the first PNP transistor Q 1 The base-emitter reverse bias voltage and the second NPN transistor Q 3 The base-emitter forward voltage drop remains constant when the second capacitor... C det The voltage across the terminals is equal to the parasitic capacitance of the piezoelectric transducer PZT. C p With the second NPN tube Q 3 When the sum of the base-emitter forward voltage drops is equal to the peak voltage drop, the peak detection module generates a signal to activate the second PNP transistor. Q 4 When the NMOS transistor is turned on, the RC differentiating module generates a positive differential pulse signal that is opposite to the positive half-cycle, causing the NMOS transistor to conduct. Mn During conduction, parasitic capacitance of the piezoelectric transducer PZT is also formed during the negative half-cycle. C p With NMOS transistor Mn Drain-source, first diode Dn ,inductance L Energy storage capacitor Cr、 Second PNP tube Q 4 The CLC resonance formed by the emitter and collector stores the piezoelectric transducer PZT in the parasitic capacitance. C p The energy is transferred within the second capacitor. C det With NMOS transistor Mn Drain-source, first diode Dn ,inductance L Energy storage capacitor Cr Second PNP tube Q 4Emitter-base, second NPN transistor Q 3 The collector-emitter junction also forms a path for the second capacitor. C det A CLC resonant circuit extracts the tiny amount of energy stored in the inductor; similarly, the energy is first transferred to the inductor after 1 / 4 of a resonant cycle. L With energy storage capacitor Cr Above, after another 1 / 4 resonant cycle, the inductor... L The energy is then transferred to the energy storage capacitor. Cr The positive terminal of the piezoelectric transducer PZT also increases the initial voltage for the positive half-cycle operation.

[0015] During the positive and negative half-cycles, the inductor L The inductor current flows from left to right, which solves the problem of a 180° phase difference between the positive and negative half-cycle inductor currents in other existing circuit structures. It can be effectively applied to scenarios where multiple piezoelectric energy harvesting units work together to capture vibration energy to meet greater energy demands.

[0016] Example 2: Figure 3 As shown, there are five piezoelectric energy harvesting units, and each piezoelectric energy harvesting unit has the same internal structure. In each piezoelectric energy harvesting unit, a first NPN transistor is used. Q 2 The emitter serves as the A terminal of the piezoelectric energy harvesting unit, with the first capacitor... C der The other end serves as the B end of the piezoelectric energy harvesting unit, using the second PNP tube. Q 4 The emitter serves as the collector (C) terminal of the piezoelectric energy harvesting unit. The number of switches in the piezoelectric energy harvesting unit is controlled by an RC differentiating module for the NMOS transistor. Mn With PMOS transistor Mp The control enables multiplexing, reducing the energy harvesting circuit structure to half that of the past. By using a single inductor, the number of components in the expanded circuit is further reduced, thus reducing the size.

Claims

1. A scalable piezoelectric vibration energy harvesting interface circuit based on RC differentiation, characterized in that... The device includes at least one piezoelectric energy harvesting unit, an NMOS transistor, a PMOS transistor, an inductor, a first diode, a second diode, an energy storage capacitor, and a load resistor. Each piezoelectric energy harvesting unit includes a piezoelectric transducer, an RC differentiating module, and a peak detection module. The RC differentiating module includes a first capacitor and a first resistor. The peak detection module includes a second capacitor, a first PNP transistor, a first NPN transistor, a second NPN transistor, and a second PNP transistor. The positive terminal of the piezoelectric transducer, one end of the first capacitor, the base of the first PNP transistor, the collector of the first NPN transistor, the base of the second NPN transistor, and the collector of the second PNP transistor are connected. The other end of the first capacitor, one end of the first resistor, the gate of the NMOS transistor, and the gate of the PMOS transistor are connected. The emitters of the first PNP transistor and the second NPN transistor are connected to... One end of the second capacitor is connected to the base of the first PNP transistor, and the collector of the second NPN transistor is connected to the base of the second PNP transistor. The emitter of the first NPN transistor, one end of the inductor, and the cathode of the first diode are connected. The other end of the inductor, one end of the energy storage capacitor, and one end of the load resistor are connected. The emitter of the second PNP transistor, the other end of the energy storage capacitor, the other end of the load resistor, and the anode of the second diode are connected. The anode of the first diode is connected to the source of the NMOS transistor, and the cathode of the second diode is connected to the source of the PMOS transistor. The negative terminal of the piezoelectric transducer, the other end of the first resistor, the other end of the second capacitor, the drain of the NMOS transistor, and the drain of the PMOS transistor are all grounded.

2. The scalable piezoelectric vibration energy harvesting interface circuit based on RC differentiation according to claim 1, characterized in that... The number of piezoelectric energy harvesting units is five.

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