CN107508490A - A kind of piezoelectric vibration energy extracts circuit - Google Patents

Abstract

The piezoelectric vibration energy extraction circuit provided by the present invention uses a passive high-pass filter composed of capacitor C _HP and resistor R _HP to capture the falling edge generated by the OR gate in the circuit control module, and successfully obtains the zero-crossing point of the piezoelectric energy harvester current , to control the closing of the switch module, shorten the discharge time of the capacitor in the piezoelectric energy harvester, and increase the charging time of the piezoelectric energy harvester to the energy storage module, so that more piezoelectric energy can be collected; and by adjusting the capacitor C _HP The capacitance value and the resistance value of the resistor R _HP are used to control the closing time of the switch module, adapting to the working characteristics of different piezoelectric energy harvesters, and the circuit does not contain inductive components, suitable for CMOS integrated circuits, and has fewer auxiliary circuit components , lower power consumption.

Description

A piezoelectric vibration energy extraction circuit

technical field

The invention relates to the field of piezoelectric energy extraction, and more particularly, relates to an efficient piezoelectric vibration energy extraction circuit.

Background technique

In recent years, the development of wireless sensors and wireless communication network nodes has received great attention and has become a major research hotspot. Wireless sensors and wireless communication network nodes can be widely used in scenarios such as building safety detection, environmental control survey, smart home, animal positioning and tracking. However, with the rapid growth of the number of node devices and the gradual reduction in size and distribution of node locations, the conventional technical solution of using chemical batteries for node power supply gradually shows its limitations and shortcomings. Due to the limited service life of chemical batteries and the need for repeated charging, recharging or replacing batteries has become a major problem.

And with the common progress of low-power electronic design and low-power electronic manufacturing, the power consumption of wireless sensors and communication network nodes is further reduced, which can be as low as 10 to 100 μW. Therefore, the piezoelectric effect of piezoelectric materials can be used to convert the ubiquitous vibration energy of the outside world into electrical energy to provide sufficient electrical energy for the node to work. This technical solution is called piezoelectric energy harvesting technology, and the components used are piezoelectric Electric energy harvester (piezoelectric energy harvester).

Since the output of the piezoelectric energy harvester is an alternating current, and its output impedance is capacitive. In order to store and make full use of piezoelectric energy, the circuit needs a rectification interface circuit to convert the output alternating current into direct current suitable for the node. The classic rectification interface circuit is a half-wave or full-wave rectifier bridge followed by an energy storage capacitor. Although this solution has a simple structure and can output a basically stable DC current, the energy extraction efficiency is low. In order to overcome this deficiency, the team of Guyomar, Lefeuvre, and Richard proposed a high-efficiency nonlinear energy extraction circuit called SSHI (Synchronized Switch Harvesting with Inductor), which uses the assistance of inductance and synchronous switch, and applies appropriate control strategies to reduce voltage. The charging and discharging time of the internal clip capacitor of the electric energy harvester and the charging time of the energy storage capacitor are increased, thereby improving the energy extraction efficiency.

In the field of piezoelectric energy harvesting, the non-linear energy extraction circuit SSHI has become a mainstream technology, and in theory it can increase the power of energy harvesting several times, such as the SECE circuit can theoretically increase by 4 times, and the S-SSHI Get 4 times improvement, PSSHI circuit can get more than 8 times improvement. However, this kind of circuit has an inevitable disadvantage. Since the nonlinear energy extraction circuit SSHI needs an inductor with a large inductance value, and the size of this inductor is large, the self-powered design of this type of circuit Cannot be applied to CMOS integrated circuits.

In order to solve the problem that the large size of the inductor cannot be applied to CMOS integrated circuits, the researchers proposed to use inductive impedance to simulate the inductor. However, this method requires high device parameters, is difficult to adjust, and the size of the device is still large. Most importantly, the circuit implementation still requires an external power supply, which cannot achieve a true independent self-power supply.

In 2010, in order to realize the efficient collection of piezoelectric energy on CMOS integrated circuits, Ramadass abandoned the use of inductance in circuit design, and proposed a new synchronous switch interface circuit scheme. In this scheme, the closing time of the switch needs to be based on different piezoelectric energy Chip parameters are manually adjusted, and the circuit cannot realize automatic adjustment control. In order to solve the problem that the switch closing time cannot be self-adjusted, Shaohua Lu proposed a new control circuit. However, the control circuit of this scheme requires more components, resulting in high power consumption.

Contents of the invention

The present invention provides a high-efficiency piezoelectric vibration energy extraction circuit to solve the technical defects of the extraction circuit provided by the prior art that the extraction efficiency is not high and the closing time of the switch circuit included therein cannot be self-adjusted.

For realizing above-mentioned purpose of the invention, the technical scheme that adopts is:

A piezoelectric vibration energy extraction circuit, comprising a piezoelectric energy harvester, a full-wave rectifier bridge, an energy storage module, a switch module and a circuit control module;

Wherein the positive voltage output terminal _Vp of the piezoelectric energy harvester is connected with terminal one of the full-wave rectifier bridge, and the negative voltage output terminal _Vn of the piezoelectric energy harvester is connected with terminal two of the full-wave rectifier bridge; Two are in the diagonal position;

The two input terminals of the energy storage module are respectively connected to terminals 3 and 4 of the full-wave rectifier bridge;

The circuit control module includes a voltage comparator CMP ₁ , a voltage comparator CMP ₂ , a voltage comparator CMP ₃ , an OR gate V _OR , a capacitor C _HP and a resistor R _HP ; the inverting input terminal of the voltage comparator CMP ₁ , the voltage comparator The inverting input terminal of the CMP ₂ is respectively connected with the positive voltage output terminal V _p and the negative voltage output terminal V _n of the piezoelectric energy harvester, the positive input terminal of the voltage comparator CMP ₁ and the positive voltage output terminal of the voltage comparator CMP ₂ The input terminal and the positive input terminal of the voltage comparator CMP ₃ are connected to the reference voltage V _ref ; the output terminals of the voltage comparator CMP ₁ and the output terminal of the voltage comparator CMP ₂ are respectively connected to the two input terminals of the OR gate V _OR , The output terminal of the OR gate V _OR is connected to the inverting input terminal of the voltage comparator CMP ₃ through the capacitor C _HP , and the inverting input terminal of the voltage comparator CMP ₃ is grounded through the resistor R _HP ;

The switch module includes an NMOS transistor M1 and _an NMOS transistor _M2 , wherein the D pole _of the NMOS transistor M1 is connected to the positive voltage output terminal _Vp of the piezoelectric energy harvester, and the S pole _of the NMOS transistor M1 is connected to the NMOS transistor _M2 The S pole of the NMOS transistor _M2 is connected to the negative voltage output terminal _Vn of the piezoelectric energy harvester, the G pole _of the NMOS transistor M1 and the G pole of the NMOS transistor _M2 are connected to the output of the voltage comparator CMP ₃ end connection.

Compared with prior art, the beneficial effect of the present invention is:

The circuit of the present invention uses a passive high-pass filter composed of capacitor C _HP and resistor R _HP in the circuit control module to capture the falling edge generated by the OR gate, successfully obtain the current zero-crossing point of the piezoelectric energy harvester, and control the closing of the switch module , shorten the discharge time of the internal clip capacitor of the piezoelectric sheet, increase the charging time of the piezoelectric sheet to the energy storage module, so that more piezoelectric energy can be collected; and by adjusting the capacitance of the capacitor C _HP and the resistance of the resistor R _HP The value is used to control the closing time of the switch module, adapting to the working characteristics of different piezoelectric energy harvesters, and the circuit does not contain inductive components, is suitable for CMOS integrated circuits, and has fewer auxiliary circuit components and lower power consumption.

Description of drawings

Fig. 1 is a schematic diagram of circuit realization of the present invention.

FIG. 2 is a waveform diagram of various voltages and currents in a steady state of the circuit of the present invention.

Fig. 3 is a schematic diagram of the circuit of the present invention in the initial charging stage.

Fig. 4 is a schematic diagram of the circuit of the present invention in the energy extraction stage.

FIG. 5 is a schematic diagram of the circuit of the present invention in the closing phase of the synchronous switch.

FIG. 6 is a schematic diagram of the circuit of the present invention in the initial charging stage of the second half cycle.

detailed description

The accompanying drawings are for illustrative purposes only and cannot be construed as limiting the patent;

The present invention will be further elaborated below in conjunction with the accompanying drawings and embodiments.

Example 1

As shown in Figure 1, a piezoelectric vibration energy extraction circuit provided by the present invention includes a piezoelectric energy harvester, a full-wave rectifier bridge, an energy storage module, a switch module and a circuit control module;

Wherein the positive voltage output terminal _Vp of the piezoelectric energy harvester is connected to terminal one of the full-wave rectifier bridge, and the negative voltage output terminal _Vn of the piezoelectric energy harvester is connected to terminal two of the full-wave rectifier bridge;

The two input terminals of the energy storage module are respectively connected to terminals 3 and 4 of the full-wave rectifier bridge;

The circuit control module includes a voltage comparator CMP ₁ , a voltage comparator CMP ₂ , a voltage comparator CMP ₃ , an OR gate V _OR , a capacitor C _HP and a resistor R _HP ; the inverting input terminal of the voltage comparator CMP ₁ , the voltage comparator The inverting input terminal of the CMP ₂ is respectively connected with the positive voltage output terminal V _p and the negative voltage output terminal V _n of the piezoelectric energy harvester, the positive input terminal of the voltage comparator CMP ₁ and the positive voltage output terminal of the voltage comparator CMP ₂ The input terminal and the positive input terminal of the voltage comparator CMP ₃ are connected to the reference voltage V _ref ; the output terminals of the voltage comparator CMP ₁ and the output terminal of the voltage comparator CMP ₂ are respectively connected to the two input terminals of the OR gate V _OR , The output terminal of the OR gate V _OR is connected to the inverting input terminal of the voltage comparator CMP ₃ through the capacitor C _HP , and the inverting input terminal of the voltage comparator CMP ₃ is grounded through the resistor R _HP ;

The switch module includes an NMOS transistor M1 and _an NMOS transistor _M2 , wherein the D pole _of the NMOS transistor M1 is connected to the positive voltage output terminal _Vp of the piezoelectric energy harvester, and the S pole _of the NMOS transistor M1 is connected to the NMOS transistor _M2 The S pole of the NMOS transistor _M2 is connected to the negative voltage output terminal _Vn of the piezoelectric energy harvester, the G pole _of the NMOS transistor M1 and the G pole of the NMOS transistor _M2 are connected to the output of the voltage comparator CMP ₃ end connection.

Wherein, the reference voltage V _Ref is less than 0 and greater than the negative diode conduction voltage V _D , that is, -V _D <V _Ref <0.

In a specific implementation process, the energy storage module includes an energy storage capacitor C _rect and _a load resistor R _{rect .} 3. Terminal 4 is connected; one end of the energy storage capacitor C _rect and one end of the load resistor R _rect are grounded.

The charging process of the circuit is divided into four stages. In a stable working state, the waveforms of the voltage and current of the circuit are shown in Figure 2.

As shown in Figure 3, it is the initial charging stage of the circuit. Select the moment when the equivalent current source i _eq of the piezoelectric energy _harvester is 0 as the starting point, that is, at time t ₀ in Fig. Start to charge the internal clip capacitor _Cp , and at the same time, the internal clip resistor _Rp also consumes the energy of the current source. Between time t ₀ and t ₁ , since the energy storage capacitor C _rect maintains the voltage value V _rect , but the voltage across the piezoelectric energy harvester has not yet reached V _rect +2V _D , V _D is the positive voltage of the full-wave rectifier bridge diode The conduction voltage is directed, so the full-wave rectifier bridge is in a non-conducting state, the voltage V _p of the positive voltage output terminal V _p continues to rise from 0, and the voltage V _n of the negative voltage output terminal V _n continues to decrease from 0.

As shown in Figure 4, it is the energy extraction stage of the circuit. Until _t1 , the voltage across the piezoelectric energy harvester reaches V _rect +2V _D , and the full-wave rectifier bridge enters the conduction state. Since the equivalent current source is still in the forward direction, the piezoelectric sheet begins to be the energy storage capacitor C _rect Therefore, during the period from time t ₁ to t _π , the energy of the piezoelectric energy harvester is continuously extracted by the energy storage capacitor C _rect and the load resistance R _rect . This circuit is based on the negative pole of the energy storage capacitor C _rect as the reference ground. Due to the function of the rectifier bridge diode, the voltage V _{n of the negative voltage output terminal V n drops} to -V _D , while the reference voltage V _ref is slightly greater than -V _D . Therefore, after the voltage comparator CMP ₂ compares the reference voltage V _ref with the voltage V _n , the output terminal voltage V ₂ jumps from low level to high level, while the voltage V _p at the positive voltage output terminal V _p is always greater than the reference Voltage V _ref , the voltage V ₁ at the output of the voltage comparator CMP ₁ remains low, and the input terminal of the OR gate receives low level V ₁ and high level V ₂ , therefore, the output voltage V _OR also jumps to high level.

As shown in Figure 5, it is the synchronous switch closing stage of the circuit. When the equivalent current source i _eq drops to 0, the polarity will change from forward to reverse, that is, at the zero-crossing time t _π , the voltage at both ends of the piezoelectric energy harvester begins to drop, and the voltage V at the positive voltage output terminal V _{p p} starts to drop from V _rect +V _D , and at the same time, the voltage V _n of the negative voltage output terminal V _n starts to rise from -V _D. When the voltage V _n rises to be greater than the reference voltage V _ref , that is, at time t _π+ , the output terminal voltage V ₂ of the voltage comparator CMP ₂ receiving the voltage V _n and V _ref at the input terminal jumps from a high level back to a low level. level, the input terminal of the OR gate receives low-level V ₁ and low-level V ₂ , and the output terminal voltage V _OR also jumps from high level to low level. The voltage V _OR is connected to a passive high-pass filter (capacitor C _HP and resistor R _HP ), and the high-pass filter has the characteristics of filtering out low-frequency components, blocking DC components, but passing high-frequency components. Since the voltage V _OR jumps from high level to low level, the high-frequency component of the jump edge can pass through the passive high-pass filter, so the voltage V _RHP drops from 0 to an extreme voltage instantaneously, which is lower than the reference voltage V _ref small, then the capacitor C _HP discharges back to zero state, the discharge speed is related to the time constant τ=R _HP C _HP , the voltage comparator CMP ₃ compares the voltage V _RHP with the reference voltage V _ref , and obtains a short-term High level V _CTR . The NMOS transistors M ₁ and M ₂ acting as switches will enter the conduction state only when their gate-source voltage V _GS voltage is higher than the threshold voltage V _TH . The gate G of the NMOS transistors M ₁ and M ₂ is connected to the voltage V _CTR , and the high level of the voltage V _CTR is greater than the threshold voltage V _TH of the MOS transistor. Therefore, at the time t _π+ , the voltage V _CTR is It can drive the NMOS transistor M1 into the conduction state, and at this time, the body diode _of the NMOS transistor _M2 is in the forward conduction state, therefore, the circuit can complete the closing of the synchronous switch, so that the voltage at both ends of the internal clamp capacitor C _p changes from V _rect +2V _D instantly discharges to 0 value.

Among them, the closing time of the control switch of the circuit control module is t _on , which satisfies Among them, V _H represents the high level, and τ represents the time constant of the passive high-pass filter, which is τ=R _HP C _HP .

After going through the above three stages of the positive vibration cycle, the circuit enters the second half cycle, ie time t _π to t _2π . The circuit first repeats the initial charging phase, but the polarity i _eq of the equivalent current source has changed from forward to reverse, and the flow of current is shown in Figure 6. Afterwards, the circuit enters the stage of energy extraction again, and the stage of synchronous switch closing, which cycles in turn.

Apparently, the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, rather than limiting the implementation of the present invention. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. All modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the claims of the present invention.

Claims (4)

1. A piezoelectric vibration energy extraction circuit, characterized in that: comprising a piezoelectric energy harvester, a full-wave rectifier bridge, an energy storage module, a switch module and a circuit control module; Wherein the positive voltage output terminal _Vp of the piezoelectric energy harvester is connected with terminal one of the full-wave rectifier bridge, and the negative voltage output terminal _Vn of the piezoelectric energy harvester is connected with terminal two of the full-wave rectifier bridge; Two are in the diagonal position; The two input terminals of the energy storage module are respectively connected to terminals 3 and 4 of the full-wave rectifier bridge; The circuit control module includes a voltage comparator CMP ₁ , a voltage comparator CMP ₂ , a voltage comparator CMP ₃ , an OR gate V _OR , a capacitor C _HP and a resistor R _HP ; the inverting input terminal of the voltage comparator CMP ₁ , the voltage comparator The inverting input terminal of the CMP ₂ is respectively connected with the positive voltage output terminal V _p and the negative voltage output terminal V _n of the piezoelectric energy harvester, the positive input terminal of the voltage comparator CMP ₁ and the positive voltage output terminal of the voltage comparator CMP ₂ The input terminal and the positive input terminal of the voltage comparator CMP ₃ are connected to the reference voltage V _ref ; the output terminals of the voltage comparator CMP ₁ and the output terminal of the voltage comparator CMP ₂ are respectively connected to the two input terminals of the OR gate V _OR , The output terminal of the OR gate V _OR is connected to the inverting input terminal of the voltage comparator CMP ₃ through the capacitor C _HP , and the inverting input terminal of the voltage comparator CMP ₃ is grounded through the resistor R _HP ; The switch module includes an NMOS transistor M1 and _an NMOS transistor _M2 , wherein the D pole _of the NMOS transistor M1 is connected to the positive voltage output terminal _Vp of the piezoelectric energy harvester, and the S pole _of the NMOS transistor M1 is connected to the NMOS transistor _M2 The S pole of the NMOS transistor _M2 is connected to the negative voltage output terminal _Vn of the piezoelectric energy harvester, the G pole _of the NMOS transistor M1 and the G pole of the NMOS transistor _M2 are connected to the output of the voltage comparator CMP ₃ end connection. 2. The piezoelectric vibration energy extraction circuit according to claim 1, wherein the piezoelectric energy harvester is a piezoelectric sheet. 3. The piezoelectric vibration energy extraction circuit according to claim 1, characterized in that: the energy storage module comprises an energy storage capacitor C _rect and a load resistor R _rect , the two ends of the energy storage capacitor C _rect and the load resistor R _rect The two ends of the terminal are respectively connected with the terminal three and the terminal four of the full-wave rectifier bridge; one terminal of the energy storage capacitor C _rect and one terminal of the load resistance R _rect are grounded. 4. The piezoelectric vibration energy extraction circuit according to any one of claims 1-3, characterized in that: the reference voltage V _Ref is less than 0 and greater than the negative diode conduction voltage V _D , ie -V _D < V _Ref <0.