With the modern weapon system to fuze reliability, security, versatility and storage life and other technical requirements are becoming higher and higher, the traditional chemical battery power supply mode can not meet the requirements of modern weapon fuze power supply. In order to meet the power supply needs of modern fuze, based on the analysis of the electrical characteristics of piezoelectric materials, the vibration energy acquisition method of the fuze piezoelectric generator is studied, and the energy acquisition method of the fuze piezoelectric generator is optimized, so as to achieve the purpose of efficiently collecting the output energy of the piezoelectric generator. The research method in this paper provides a theoretical reference for the research of vibration and piezoelectric energy acquisition technology of piezoelectric generator, and provides a reference for the further research and design of vibration energy acquisition technology.
Vibration energy is a common energy of natural environment, which is widely used in military
facilities, industrial equipment, human movement and biological activities. Piezoelectric vibration
power generation devices are widely used in vibration energy capture because of their advantages such
as simple structure, flexible shape, high energy density and easy miniaturization[
Due to the characteristics of vibration energy, the output is AC electric energy, which can not directly charge the battery or power the load. Therefore, AC/DC rectifier circuit should be added between piezoelectric material and load to collect electric energy. material is the standard sinusoidal oscillation excitation, defined as
It is assumed that the electric energy excitation generated by the vibration F of the piezoelectric In Equation（1），V0 is voltage amplitude and ω is vibration frequency. According to Kirchhoff's law and the piezoelectric equation, the voltage on the load resistance R0 can be obtained as follows: ( ) = 0sin( ) piezoelectric material, R0 is load resistance, RD is rectifier diode loss resistance, CP is internal static capacitance of piezoelectric material. Then, the average power on the load resistor is: [( 0 + 2 ) + 2 2 ]
Because of the simple structure of standard energy collection circuit, its application field is very wide, but the circuit has the problems of low collection efficiency and high energy loss, and there are
classical full-bridge rectifier circuit. The entire circuit consists of four diodes, with R0 representing the load. many places to be improved. 2.2.
In order to eliminate the problem of high starting voltage and high power consumption caused by a large diode voltage drop, the power MOSFET is used to replace the rectifier and form an active rectifier circuit. The voltage drop of MOSFET is close to zero, and it has approximately the circuit characteristics of ideal diode. Therefore, the power loss and starting voltage of the rectifier circuit can be reduced, and the energy collection efficiency can be improved.
MN1 and MP2 are on, and MN2 and MP1 are off.
As shown in Figure 2, the voltage comparator is used to cross-couple NMOS and PMOS[
MN1 are off. At the end of CP discharge, when V1=V2, all MOSFET cut off. Similarly, when the output voltage of piezoelectric material is in negative half period, due to − 2 > |
After the electric energy output by piezoelectric material passes the rectifier circuit, its voltage
waveform is close to the DC circuit, and the current produces distortion and distortion because the
conduction time of the rectifier tube is too short, which becomes a spike pulse and reduces the power
factor. The passive power factor correction method is to make the input current of the circuit close to
sine wave by adding passive components such as capacitance and inductance into the circuit, that is, to
improve the power factor through reactive power compensation, so as to achieve the purpose of
increasing active power[
When the circuit is charging, D1 in the filling circuit is on, D2 and D3 are off, and the two filter capacitors are connected in series. The series of capacitors reduces the total capacitance value and therefore the time constant. When the circuit discharges, D1 in the filling circuit shuts off, D2 and D3 are on, and the two filter capacitors are connected in parallel. The voltage at both ends of each capacitor is 1⁄2 peak voltage, which reduces the charging threshold when the circuit is recharged. Output power of grain filling circuit is: = =
4 02 2 2 (2
+ )2
= 0, it can be known that the maximum output power and optimal load resistance of piezoelectric material are:
Valley filling circuit can greatly increase the conduction Angle of rectifier tube, by filling the valley point, the input current from the peak pulse to the waveform close to the sine wave, reduce harmonic content, improve the power factor, significantly reduce waveform distortion.
The waveform of the circuit corrected by the filling circuit is similar to that of the DC power supply. At this time, the output voltage can be adjusted by the buck-Boost circuit to make the output voltage meet the requirements of the load. The circuit is shown in Figure 4.
=
1 −
(8) (9) (10) (11) state, so the input capacitor C1 is the main power supply during this process. At the output end, C2 provides energy for R0 by its own discharge. When switch S is off, power supply V charges the input capacitor. Since the current of the inductor cannot be mutated, the inductor L1 supplies power to the output capacitor C2 and the load R0 through the continuation tube D1. After stable operation, the inductance is conserved in volts second. When the switch S is on, the inductance voltage is equal to the input power voltage VIN; When switch S is off, the inductance voltage is equal to the output voltage VOUT. Let T be the cycle, TON be the on-time, TOFF be the off time, D be the duty cycle.
When duty cycle is less than 0.5, output step-down; When duty cycle is greater than 0.5, output boost.
The circuit is shown in Figure 5, figure 6 is the simulation of traditional energy collection circuit, and Figure 7 is the simulation of induced piezoelectric energy collection circuit.
Comparing the output voltage of the traditional energy collection circuit with that of the induced piezoelectric energy collection circuit, the peak voltage is increased by 1.455 V, the valley value is increased by 0.703 V, the average output voltage is increased by 29.4%, and the energy collection efficiency is improved to a certain extent.
In this paper, a piezoelectric energy collection circuit with low power consumption and high acquisition efficiency is designed, which uses active diode instead of traditional diode to reduce the voltage loss and improve the power conversion efficiency. 7. References