CN106300447A - A kind of based on the wireless electric energy transmission device utilizing capacity coupled two-plate virtual address structure - Google Patents

Abstract

The present invention relates to a kind of based on the wireless electric energy transmission device utilizing capacity coupled two-plate virtual address structure.The analysis of the present invention circuit model pluses and minuses by conducting electricity typical capacitance, devises a new electric capacity on its basis and conducts electricity circuit model, increase by a pair plates capacitance and two conductors.The high frequency voltage that can produce at higher-order of oscillation system electric capacity under resonance condition and inductance connection, receives high frequency voltage and will produce faradic current on plates capacitance, it is achieved electric capacity transmission between plates capacitance.The present invention conduct electricity relative to inductance there is simple in construction, efficiency extends the features such as decay is slow with distance；Relatively conventional electric capacity transmission of electricity structure, can cross reduction operating frequency and efficiency of transmission relatively advantages of higher in the case of long distance power transmission.The present invention well solves inductance and conducts electricity the restriction to surrounding requirement, is more suitable for being applied to the situations, such as electric automobile wireless charging such as surrounding tenor is high, mobile phone plane plate wireless charging etc..

Description

A Wireless Power Transmission Based on Two-Plate Virtual Ground Structure Using Capacitive Coupling device

technical field

The invention relates to a high-frequency resonant high-voltage electric field coupling wireless power transmission technology, in particular to a wireless power transmission device based on a two-plate virtual ground structure utilizing capacitive coupling.

Background technique

Inductive Power Transfer Technology (IPT) has been widely applied to electric vehicles and mobile terminal equipment, and its transmission efficiency is already comparable to that of traditional wired power transmission. However, the disadvantage of inductive power transmission is that it depends on the conductor medium. When the concentration of metal substances in the air is high, the magnetic field will generate a current vortex, causing energy loss and increasing the temperature, which is very dangerous. Capacitive transmission is a good solution to this problem.

Capacitive power transfer uses an electric field instead of a magnetic field to transfer electrical energy. The electric field transmits electricity in a space with metal obstacles without causing energy loss. Therefore, capacitive power transmission is more suitable for wireless power transmission in electric vehicles and other aspects. Another advantage of capacitive transfer is low cost. Capacitive power transmission only uses metal plates, which have the advantages of good conductivity, low price, and light weight; while the coils for inductive power transmission must be wound with Litz wire, which is relatively expensive, which is very unfavorable for wireless power transmission popularity. However, the typical capacitive transmission circuit has the following two disadvantages (as shown in Figure 1): as the transmission distance increases, the coupling capacitance value becomes very small, which makes the system resonant frequency increase seriously; and at very high frequencies, The high-frequency power supply required by the system is difficult to manufacture, and the high-frequency resistance increases sharply, which leads to a rapid decline in the overall efficiency of the system. Therefore, it is difficult for the wireless power transmission system based on the traditional capacitive transfer model to realize long-distance power transmission.

Contents of the invention

The invention designs a new capacitive electric circuit model by analyzing the advantages and disadvantages of the typical capacitive electric circuit model. Compared with the traditional inductive power transmission, the present invention has the advantages of simple structure, weak influence by the surrounding medium, and low attenuation rate; high transmission efficiency, stable working frequency, and little influence by transmission distance; The current is very small, at the mA level, so it is not sensitive to the resistance of the capacitor plate. Therefore, it has the advantage of high practicality.

The technical scheme that the present invention adopts is as follows:

A wireless power transmission device based on a two-plate virtual ground structure utilizing capacitive coupling, including a frequency-adjustable high-frequency AC power supply, a transmitting end resonant system, a receiving end resonant system, a plate capacitor C ₂ and two conductors; the plate capacitor C ₂ includes two capacitive plates, namely E plate and F plate, and E plate and F plate are facing each other;

The high-frequency AC power supply, the resonant system of the transmitting end, the E plate of the plate capacitor C2 and the conductor ₁ constitute the transmitting end; the resonant system of the receiving end, the F plate of the plate capacitor C2, the load and the conductor ₂ form the receiving end;

The conduction direction of electric energy is as follows: high-frequency AC power supply, resonant system at the transmitting end, E plate of the plate capacitor _C2 , F plate of the plate capacitor _C2 , resonant system at the receiving end, and load.

The resonant system at the transmitting end includes an inductance L1 and a tuning capacitor _C1 . The high _- frequency AC power supply and the resonant system at the transmitting end form a series loop. A and B are respectively the _two ends of the capacitor _C1 and the E plate of the plate capacitor C2. It is connected to the A terminal of the capacitor _C1 , the A terminal is located between the inductor L1 and the tuning capacitor _C1 , and the B terminal is connected to the conductor _{1 ;} the receiving end resonant system includes the inductor L3 and the tuning capacitor _C3 , and the receiving end resonates The system and the load form a series loop. C and D are the _two ends of the capacitor C3 respectively. _The F plate _of the plate capacitor C2 is connected to the C terminal _of the capacitor C3. _The C terminal is located between the inductor L3 and the tuning capacitor C3. Terminal D is connected to conductor 2.

A rectification circuit is arranged between the resonant system at the receiving end and the load.

Both the resonant system at the transmitting end and the resonant system at the receiving end are coil systems with low internal resistance and high Q value.

The shapes of the conductor 1 and the conductor 2 can be the same or different, and the shapes can be varied, including linear, plate, block, spherical, etc.

The resonant system at the transmitting end is consistent with the natural frequency of the resonant system at the receiving end.

The plate capacitor is made of aluminum foil or iron plate; but not limited to the above two materials.

Compared with inductive power transmission, the present invention has the characteristics of simple structure and slow efficiency attenuation with distance extension; compared with traditional capacitive power transmission structure, it has the advantages of lower working frequency and higher transmission efficiency in the case of long-distance power transmission. The present invention well solves the limitation of inductive power transfer on the surrounding environment, and is more suitable for application to situations such as high metal content in the surrounding environment, such as wireless charging of electric vehicles, wireless charging of mobile phones and tablets, and the like.

Description of drawings

Figure 1 is a typical capacitive power transmission circuit diagram;

Fig. 2 is a schematic diagram of the present invention's improved capacitive transmission;

Fig. 3 is the realization diagram of the system of the present invention;

Fig. 4 is equivalent circuit diagram of the present invention;

Fig. 5 is a schematic diagram of plate capacitive coupling.

detailed description

As shown in Fig. 2, the present invention includes four parts: a frequency-adjustable AC power supply, two sets of resonant systems, plate capacitors and two conductors. The transmitting end is composed of a high-frequency AC power supply, the resonant system of the transmitting end, the E plate of the plate capacitor C2 and conductor ₁ ; the receiving end is composed of the receiving end resonant system, the F plate of the plate capacitor C2, conductor ₂ and the load. The resonant system at the transmitting end includes inductance L ₁ and tuning capacitor C ₁ , the high-frequency AC power supply and the resonant system at the transmitting end form a series loop, the E plate of the plate capacitor C ₂ is connected to the A terminal of the capacitor C ₁ , and the B terminal of the capacitor C ₁ Connect with conductor 1; the resonant system at the receiving end includes inductance L ₃ and tuning capacitor C ₃ , the resonant system at the receiving end forms a series loop with the load, the F plate of the plate capacitor C ₂ is connected to the C terminal of the capacitor C ₃ , and the capacitor C ₃ Terminal D is connected to conductor 2; E and F plates of plate capacitor C ₂ are facing each other. The transmitting end and the receiving end are wirelessly connected, and energy transmission is performed only through the plate capacitance.

Conductor 1 and conductor 2 are equivalent to two ground capacitances relative to infinity. In the resonant state, the high-frequency oscillation system will generate a large high-frequency and high-voltage voltage at the point _A connecting the capacitor _C1 and the inductor L1. When the high-frequency voltage is led to the E terminal of the plate capacitor _C2 , the The plate capacitance forms a loop with the two ground capacitances of conductor 1 and conductor ₂ , and a high-frequency electric field will be generated at both ends of E and F of the plate capacitance C2, thereby generating an induced current. Driven by the high-frequency electric field, the high-frequency voltage generated by the resonant system causes a high-frequency electric field to be generated between the plate capacitors, and a rapidly changing induced current I ₂ is generated between the plate capacitors. When passing through the receiving end capacitor C ₃ , it will be at C ₃ The induction voltage of the same frequency is generated on the circuit, and causes the loop resonance of the receiving end loop C _{3 -L 3} -RL, thereby generating a large current and consuming large power on the receiving end load. In this way, the transmitting end provides energy, the receiving end and the load consume energy, and wireless transmission of electric energy is realized.

_In the present invention, the amplitude of the induced current I in the transmission loop is relatively small and is at the mA level, so it is difficult to generate power in the transmission loop. Therefore, the system does not have high requirements for the parasitic resistance of the transmission loop. If it is very large (such as 5kΩ), it will not significantly affect the transmission efficiency of the system. Therefore, in actual use, it is sufficient to use common metal materials such as aluminum foil paper and iron plates to construct plate capacitors. This is also an important feature of the present invention.

In the present invention, the capacity value of the plate capacitance C2 is very small, about ₃ to 6pF, and the virtual ground capacitance of conductor 1 and conductor 2 is about 30 to 60pF for the infinite distance. In the loop, the capacitance of the virtual ground capacitance is larger than that of the plate capacitance, so the virtual ground capacitance does not have a major impact on the transmission efficiency of the system, and the energy is mainly transferred between the plate capacitances. There are many ways to construct virtual ground capacitors. Isolated conductors such as wires, plates, blocks, and balls can be used to construct virtual ground capacitors.

Step 1 Selection of high frequency AC power supply

The AC power supply needs to have the following three characteristics:

1) The frequency is stable. It can work stably at the resonant frequency of the system for a long time, and the frequency fluctuation must be as small as possible.

2) The frequency is adjustable. Since the wound coils or produced capacitors cannot be guaranteed to be exactly the same, and the working environment of the system will also be different, the resonant frequencies of different wireless energy transfer systems cannot be exactly the same. The designed power supply needs to be able to adapt to different systems, that is, the frequency must be adjustable.

3) Low internal resistance. In order to reduce the energy consumed by the high-frequency AC power supply, it is necessary to choose a power supply with a small internal resistance.

Based on the above requirements, the AC power supply used in the present invention is composed of a DC power supply and an inverter circuit, and the selected inverter circuit has the function of manually adjusting the working frequency, which can not only conveniently and intuitively see the working effect under different frequencies, but also Make the selected high-frequency AC power supply adapt to different systems.

Step 2 Selection of resonant system

The resonant system selected by the present invention is a coil system with low internal resistance and high Q value. The internal resistance of the coil is low, and the system obtains a large induced current. When the high internal resistance generates a higher potential, the middle of the plate capacitance has a higher electric field energy. When the internal resistance of the coil is constant, choosing a coil with a high Q value can reduce the active power consumption of the system impedance, thereby obtaining higher transmission efficiency.

Step 3 Realization of capacitive power transmission

As shown in Figure 2, two pole plates of the pole plate capacitor used in the present invention are opposite, can select simple materials such as tinfoil paper, iron plate for use, pole plate capacitance E plate connects the A end of electric capacity C ₁ , corresponds to it The corresponding plate capacitor F is connected to terminal C _of capacitor C3, and terminals B and _D of capacitors _C1 and C3 are respectively grounded to conductor 1 and conductor 2.

Figure 4 is an equivalent circuit diagram of the present invention. In the present invention, both ends of the resonant capacitor are connected to the conductor, and the conductor forms a capacitance with infinity, which is equivalent to forming a transmission circuit by the plate capacitance C ₂ and two virtual ground capacitances C _g1 and C _g2 connected in series, so that the plate capacitance Induction current I ₂ is generated in C ₂ , but energy transmission cannot be performed between the two conductors. If the capacitance formed by the conductor and infinity is small, the equivalent capacitance reactance of the conductor will be large, so the equivalent capacitance of the conductor The lower the value, the more energy will be consumed on the conductor, the less energy will be transferred through the plate capacitance, the lower the transmission efficiency or not enough to drive the load at all, so a conductor with a larger equivalent capacitance should be selected. For an isolated conductor sphere with radius R in air, the capacitance calculation formula relative to infinity is C _g =4πε ₀ R, where ε ₀ =8.85×10 ^-12 is the vacuum permittivity, and R is the radius of the conductor sphere. When the charge change in the conductor is Δq, the potential change is When the charge of an isolated conductor ball changes, the charge change is more obvious, which is not conducive to the operation of the system. Therefore, it is necessary to choose a conductor with a small potential change and a large equivalent capacitance.

Figure 5 is a schematic diagram of the plate capacitance. The solid line arrows indicate that the high frequency voltage is in the positive half cycle, and the dotted line arrows indicate that when the high frequency voltage is in the negative half cycle, the rapid transformation of the charges on the two plates of the plate capacitor produces a rapidly changing current, thereby realizing energy transmission. The formula for calculating plate capacitance is A is the area of the plate capacitor, d is the distance between the two plate capacitors, the capacitance of the plate capacitor is very small, only pF level can realize the energy transfer between the plate capacitors through electric field coupling. Under the resonant frequency of the high-frequency oscillation system, the conductor has a relatively large capacitance relative to infinity, and the energy is transferred from the capacitance of the plates to drive the load to work.

By establishing Kirchhoff's equations in the operating frequency band:

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; j\&omega;L</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; j\&omega;C</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; j\&omega;C</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; ,</span>\\ {\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; j\&omega;C</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; j\&omega;C</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; j\&omega;C</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; j\&omega;C</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; j\&omega;C</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; j\&omega;C</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; j\&omega;C</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; ,</span>\\ {\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; j\&omega;C</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; j\&omega;L</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; j\&omega;C</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0.</span>}\end{array}\right.$

Among them, R ₁ ＝R _C1 +R _L1 +R _p , R ₃ ＝R _C3 +R _L3 +R _L , R _p is the internal resistance of the power supply, R _C1,3 , R _L1,3 are the resonance system capacitance and the internal resistance of the inductor respectively .

By deriving Kirchhoff's equations, we get The transmission power P _O =|I ₃ | ² R _L is obtained. in R ₁ =R _C1 +R _L1 +R _p , R ₃ =R _C3 +R _L3 +R _L .

After the system of the present invention is connected in sequence, the AC power supply is turned on. At this time, an induced current is generated in the system. Because of the high-frequency effect, a high-frequency voltage is generated between the capacitor and the inductor, and an induced current is generated on the plate capacitor. The natural frequencies of the receiving and transmitting resonant systems used in the present invention are consistent, the energy is transferred between the plate capacitors, and drives the resonant system at the receiving end to resonate, and the rectification circuit rectifies the received high-frequency electric energy to drive the load to work. At this time, the frequency of the AC power supply is adjusted so that the system works at different frequencies, the induced current and induced electromotive force generated by the system are changed, and the electric energy received by the load is also different. In order to enable the system to obtain higher working performance, it is only necessary to adjust the working frequency to maximize the receiving current.

Claims (5)

1. A wireless power transmission device based on a two-plate virtual ground structure utilizing capacitive coupling, characterized in that: it includes a frequency-adjustable high-frequency AC power supply, a transmitting end resonant system, a receiving end resonant system, a plate capacitance C ₂ and two conductor; plate capacitor C ₂ includes two capacitor plates, respectively E plate and F plate, E plate, F plate facing; The high-frequency AC power supply, the resonant system of the transmitting end, the E plate of the plate capacitor C2 and the conductor ₁ constitute the transmitting end; the resonant system of the receiving end, the F plate of the plate capacitor C2, the load and the conductor ₂ form the receiving end; The conduction direction of electric energy is as follows: high-frequency AC power supply, resonant system at the transmitting end, E plate of the plate capacitor _C2 , F plate of the plate capacitor _C2 , resonant system at the receiving end, and load. 2. A wireless power transmission device based on a two-plate virtual ground structure utilizing capacitive coupling according to claim 1, characterized in that: the resonant system at the transmitting end includes an inductance L ₁ and a tuning capacitor C ₁ , high frequency The AC power supply and the resonant system of the transmitting end form a series loop, A and B are the _two ends of the capacitor _C1 respectively, the E plate of the plate capacitor C2 is connected to the A terminal of the capacitor _C1 , and the _A terminal is located at the inductor L1 and the tuning capacitor C ₁ , terminal B is connected to conductor 1; the resonant system at the receiving end includes an inductance L ₃ and a tuning capacitor C ₃ , the resonant system at the receiving end forms a series loop with the load, and C and D are the two ends of the capacitor C ₃ respectively, F plate of the plate capacitor C ₂ is connected to the C terminal of the capacitor C ₃ , the C terminal is located between the inductor L ₃ and the tuning capacitor C ₃ , and the D terminal is connected to the conductor 2 . 3. A wireless power transmission device based on a two-plate virtual ground structure utilizing capacitive coupling according to claim 2, wherein a rectification circuit is arranged between the resonant system at the receiving end and the load. 4. A wireless power transmission device based on a two-plate virtual ground structure utilizing capacitive coupling according to claim 2, wherein both the resonant system at the transmitting end and the resonant system at the receiving end are selected from low internal resistance, high Q value coil system. 5. A wireless power transmission device based on a two-plate virtual ground structure utilizing capacitive coupling according to claim 2, wherein the natural frequency of the resonant system at the transmitting end is the same as that at the resonant system at the receiving end.