CN108616168B - Electromagnetic interference prediction circuit and method for resonant wireless charging system with relay coil - Google Patents
Electromagnetic interference prediction circuit and method for resonant wireless charging system with relay coil Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J50/00—Circuit arrangements or systems for wireless supply or distribution of electric power
- H02J50/10—Circuit arrangements or systems for wireless supply or distribution of electric power using inductive coupling
- H02J50/12—Circuit arrangements or systems for wireless supply or distribution of electric power using inductive coupling of the resonant type
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J50/00—Circuit arrangements or systems for wireless supply or distribution of electric power
- H02J50/50—Circuit arrangements or systems for wireless supply or distribution of electric power using additional energy repeaters between transmitting devices and receiving devices
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J50/00—Circuit arrangements or systems for wireless supply or distribution of electric power
- H02J50/70—Circuit arrangements or systems for wireless supply or distribution of electric power involving the reduction of electric, magnetic or electromagnetic leakage fields
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Abstract
The invention discloses an electromagnetic interference prediction circuit and method for a resonant wireless charging system containing a relay coil, wherein the electromagnetic interference prediction circuit comprises a resonant network and an input side inverter circuit connected to the input end of the resonant network, and the input end of the input side inverter circuit is connected with a direct current input power supply; the filter circuit also comprises an output side rectifying circuit connected with the output end of the resonant network and a filter capacitor connected in parallel with the output side rectifying circuit; the invention establishes an electromagnetic interference model circuit of a resonant wireless charging system containing a relay coil; performing predictive analysis on common mode and differential mode electromagnetic interference of an input side and an output side of the system when the output power is larger; when the system is designed, the reasonable selection of parameters is noticed, guidance is provided for the electromagnetic interference suppression of an actual system, the method can be used for guiding the wireless charging system to design system parameters, the time for designing the wireless charging product system is saved, the research and development process is promoted, the test cost of the product in the production process is saved, resources are saved, and great economic benefits are achieved.
Description
Technical Field
The invention belongs to the field of power electronic electromagnetic interference research, and relates to an electromagnetic interference prediction circuit and method for a resonant wireless charging system with a relay coil.
Background
With the increasing severity of energy and environmental issues, wireless charging systems have attracted attention by their advantages of safety, convenience, and wide application. Therefore, the wireless charging system is widely applied to charging of electric vehicles, power supply of implantable medical devices, and other consumer electronic products, such as electric toothbrushes, mobile phones, and the like. The problem of electromagnetic interference generated by the system during charging is also of increasing concern.
With respect to the electromagnetic interference problem of the wireless charging system, researchers at home and abroad have conducted many studies on related aspects. The disclosed invention is characterized in that: method and apparatus for controlling interference in a wireless power transmission system invented a method of interference control for a Power Transmission Unit (PTU) that can determine whether the PTU is in an interference environment and ultimately control communication parameters of either or both of a neighboring PTU and a Power Receiving Unit (PRU); harmonic reduction device for a wireless power transfer system designs an arrangement of harmonic reduction devices coupled between a switching network and a transmitter coil, the harmonic reduction devices configured to attenuate at least one frequency component; a wireless battery charging apparatus installed in a vehicle and designed to reduce electromagnetic interference provides a wireless battery charging apparatus installed in a vehicle and designed to reduce electromagnetic interference for electrostatic protection to reduce electromagnetic interference caused by radiation from a wireless battery charger.
The method mentioned in the prior art mainly aims at electromagnetic interference suppression, reduction, control and shielding after the system is built, and cannot modify and adjust the system.
Disclosure of Invention
In order to intuitively know the electromagnetic interference condition of the resonant wireless charging system with the relay coil and make guidance for subsequent system design and power efficiency improvement, the invention aims to provide the electromagnetic interference prediction circuit and the method for the resonant wireless charging system with the relay coil.
In order to achieve the purpose, the technical scheme adopted by the invention is that the electromagnetic interference prediction circuit of the resonant wireless charging system with the relay coil comprises a resonant network and an input side inverter circuit connected to the input end of the resonant network, wherein the input end of the input side inverter circuit is connected with a direct current input power supply; the filter circuit also comprises an output side rectifying circuit connected with the output end of the resonant network and a filter capacitor connected in parallel with the output side rectifying circuit;
the resonant network comprises a transmitting side resonant network connected with the input side inverter circuit, a receiving side resonant network connected with the output side rectifier circuit, and a relay coil resonant network connected between the transmitting side resonant network and the receiving side resonant network, wherein parasitic capacitors are connected between the relay coil resonant network and the transmitting side resonant network as well as between the relay coil resonant network and the receiving side resonant network;
the relay coil resonance network comprises n relay coils, wherein n is larger than or equal to 1, and a parasitic capacitor is connected between adjacent relay coils.
The input side inverter circuit is a half-bridge inverter circuit, the half-bridge inverter circuit comprises two switching tubes which are connected in series, a capacitor is connected between a source electrode and a drain electrode of each switching tube, and a ground capacitor is connected between the center of a half bridge, namely the connecting middle point of the two switching tubes, and the ground; the transmitting side resonant network comprises a transmitting coil consisting of a capacitor, an inductor and a resistor which are connected in series, and the transmitting coil is connected between the connection midpoint of the two switching tubes and the negative electrode of the direct-current input power supply;
the output side rectifying circuit is a full-bridge rectifying circuit, four diodes are connected in parallel after being connected in series in pairs, capacitors are connected in parallel between the positive electrode and the negative electrode of each diode, a ground capacitor is connected between the middle point of each bridge arm and the ground, the receiving side resonant network comprises a receiving coil consisting of the capacitors, the inductors and the resistors which are connected in series, and the receiving coil is connected between the middle points of the two bridge arms.
The filter capacitor comprises a high-frequency filter capacitor and a low-frequency filter capacitor.
Each relay coil comprises a capacitor, an inductor and a resistor which are connected in series, wherein a parasitic capacitor is arranged between the inductors of the adjacent relay coils, and two ends of each of the two inductors are connected through the two parasitic capacitors.
The invention also discloses a method for predicting electromagnetic interference of the resonant wireless charging system with the relay coil, which comprises the following steps:
step 1: determining the working parameters of the wireless charging system, including the input voltage U, the working frequency f and the load RL；
Step 2: determining resonant network parameters including a transmitting side resonant inductor L according to the working parameters determined in the step 1pResonant capacitor C on the transmitting sidepA receiving side resonant inductor LsA receiving side resonance capacitor CsRelay coil resonance inductance L1～LnRelay coil resonance capacitor C1～Cn；
And step 3: determining coupling parameters between the coils according to the coil resonance network parameters determined in the step 2, wherein the coupling parameters comprise a coupling coefficient k1～kn、kn+1Then determining the mutual inductance M between the coils based on the coupling coefficient1～Mn、Mn+1；
And 4, step 4: establishing a system electromagnetic interference model, and adding system parasitic parameters;
and 5: and 4, simulating by using the electromagnetic interference model established in the step 4 to obtain the waveforms of the common-mode interference signal and the differential-mode interference signal of the input side and the output side when the power is high.
In step 2, the coil resonance network parameters are related to the working frequency f, and the inductor with the corresponding inductance value is wound according to the selected capacitance value, wherein:
the resonance network parameters and the working frequency of the relay coil satisfy the following relations:
jωLn＝1/jωCn(1-n)
the resonant network parameters of the transmitting side coil and the working frequency satisfy the following relations:
jωLp＝1/jωCp(1-p)
the resonance network parameters of the receiving side coil and the working frequency satisfy the following relations:
jωLs＝1/jωCs(1-s) wherein ω ═ 2 π f.
In the step 3:
determining coupling parameters between the coils according to the coil resonance network parameters determined in the step 2, wherein the coupling parameters comprise a coupling coefficient k1～kn、kn+1Then determining the mutual inductance M between the coils based on the coupling coefficient1～Mn、Mn+1The mutual inductance between the resonance coils, the coupling coefficient and the coil inductance value satisfy the following relationship, wherein:
M1mutual inductance, which is the coupling coefficient of the transmitter coil and the 1 st relay coil:
M2～Mnmutual inductance between relay coils:
Mn+1mutual inductance between the nth relay coil and the receiving coil:
in step 3, the coil coupling coefficient is determined by the distance and relative position of each coil and the properties of the surrounding magnetic medium.
In step 4, the method for determining the parasitic parameters of each device in the circuit comprises the following steps:
1) for the parasitic capacitance parameter between the coils, the magnitude is obtained according to the following calculation formula of the plate capacitance:
wherein S is the facing area of the two plates of the capacitor, d is the distance between the two plates of the capacitor, epsilon is the dielectric constant, k1Is the electrostatic constant;
2) for the parasitic capacitance parameters of the switching device and the diode, the relative area between the plates and the distance between the plates are obtained by searching a device manual MOSFET switching tube, and the equivalent earth parasitic capacitance C is calculated according to a formula (3)qAnd taking values, and calculating the value of the parasitic capacitance to the ground of the diode.
The invention establishes an electromagnetic interference model circuit of a resonant wireless charging system containing a relay coil; performing predictive analysis on common mode and differential mode electromagnetic interference of an input side and an output side of the system when the output power is larger; when the system is designed, the reasonable selection of parameters is noticed, and guidance is provided for the electromagnetic interference suppression of the actual system.
Compared with the prior art, the method has the advantages that the method can be used for guiding the wireless charging system (containing the relay coil) to carry out system parameter design, saves the time for designing the wireless charging product system and promotes the research and development process, and the method can carry out prediction analysis on the system electromagnetic interference before the actual device is put into use, thereby saving the test cost of the product in the production process, saving resources and having great economic benefit. The prediction method can also be used for researching the electromagnetic interference suppression method of the wireless charging product, is beneficial to saving design time and resources, and has remarkable effect.
Drawings
FIG. 1 is a system EMI modeling circuit of the present invention.
FIG. 2 is a circuit diagram of an EMI model of a system including a relay coil according to the present invention.
Fig. 3 shows the common mode interference result at the input side of the system with a relay coil according to the present invention.
FIG. 4 shows the common mode interference result at the output side of the system including a relay coil according to the present invention.
Fig. 5 shows the result of the input-side differential mode interference of the system including a relay coil according to the present invention.
Fig. 6 shows the result of the differential mode interference at the output side of the system with a relay coil according to the present invention.
Detailed Description
The present invention will be described in further detail with reference to the following drawings and examples.
The circuit of the system of the invention is shown in figure 1. The input voltage is direct current, the input side inverter circuit selects a half-bridge inverter circuit, energy is transmitted through a resonant network, the output side rectifier circuit selects a full-bridge rectifier circuit, and the output voltage is direct current after capacitance filtering. L isp、CpForming a transmitting side resonant network, RpIs the equivalent series resistance of the transmitter coil. L iss、CsForming a receiving-side resonant network, RsIs the equivalent series resistance of the receiving coil. L is1、C1Form a 1 st relay coil resonance network, R1Is the equivalent series resistance of the 1 st repeating coil. In the same way, Ln、CnEqual to form an nth relay coil resonant network, RnIs the equivalent series resistance of the nth relay coil. Coupling coefficient k between coils1、k2……kn、kn+1Wherein k is1As the coupling coefficient of the transmitting coil and the 1 st relay coil, k2～knIs a coupling coefficient between the relay coils, kn+1Is the coupling coefficient between the nth relay coil and the receiving coil, RLIs the load of the system.
An electromagnetic interference prediction circuit of a resonant wireless charging system containing a relay coil comprises a resonant network and an input side inverter circuit connected to the input end of the resonant network, wherein the input end of the input side inverter circuit is connected with a direct current input power supply DC; the filter circuit also comprises an output side rectifying circuit connected with the output end of the resonant network and a filter capacitor connected in parallel with the output side rectifying circuit; the filter capacitor comprises a high-frequency filter capacitor CHAnd a low frequency filter capacitor CL；
Wherein the resonant network comprises a transmitting side resonant network connected with the input side inverter circuit, a receiving side resonant network connected with the output side rectifier circuit, and a relay coil resonant network connected between the transmitting side resonant network and the receiving side resonant network, and parasitic capacitors are connected between the relay coil resonant network and the transmitting side resonant network and between the relay coil resonant network and the receiving side resonant network, as shown in fig. 2, the model is a wireless charging system model with one relay coil, wherein C11、C12、C21And C22Are all parasitic capacitances;
the relay coil resonance network comprises n relay coils, wherein n is larger than or equal to 1, and a parasitic capacitor is connected between adjacent relay coils.
The input side inverter circuit is a half-bridge inverter circuit which comprises two switching tubes S connected in series1And S2A capacitor is connected between the source and the drain of each switching tube, and a ground capacitor C is connected between the center of the half bridge, namely the connecting middle point of the two switching tubes, and the groundq(ii) a The transmission side resonant network comprises a capacitor C connected in seriesPInductor LPAnd a resistance RPAssembled transmitting coil, transmittingThe coil is connected between the connection midpoint of the two switching tubes and the negative electrode of the direct-current input power supply DC;
the output side rectifying circuit is a full-bridge rectifying circuit and four diodes D1、D2、D3And D4A connection mode that every two diodes are connected in series and then connected in parallel is adopted, a capacitor is connected between the anode and the cathode of each diode in parallel, and a ground capacitor is connected between the middle point of each bridge arm and the ground; in this embodiment, D1And D3In series, D2And D4In series, D1And D3And D2And D4Then parallel connection is carried out; d, D1And D3Through CtGround, D2And D4Through CrGrounded, the receiving side resonant network comprises a capacitor C connected in seriesSInductor LSAnd a resistance RSThe receiving coil is connected between the middle points of two bridge arms of the full-bridge rectifying circuit.
Each relay coil comprises a capacitor, an inductor and a resistor which are connected in series, wherein a parasitic capacitor is arranged between the inductors of the adjacent relay coils, and two ends of each of the two inductors are connected through the two parasitic capacitors.
For a wireless charging system, the prediction process of the electromagnetic interference situation is as follows:
step 1: determining basic working parameters of the wireless charging system according to the required working scene, wherein the basic working parameters comprise input voltage U, working frequency f and load RLAll are set according to working conditions.
Step 2: determining resonant network parameters including a transmitting side resonant inductance L based on the determined operating parameterspResonant capacitor CpA receiving side resonant inductor LsResonant capacitor CsRelay coil resonance inductance L1、L2……LnResonant capacitor C1、C2……Cn；
The coil resonance network parameters are related to the working frequency f, and the inductor with the corresponding inductance value is wound according to the selected capacitance value, so that the following relation is required to be satisfied:
jωL1＝1/jωC1(1-1)
jωL2＝1/jωC2(1-2)
jωL3＝1/jωC3(1-3)
……
jωLn＝1/jωCn(1-n)
jωLp＝1/jωCp(1-p)
jωLs＝1/jωCs(1-s)
wherein ω is 2 pi f;
and step 3: determining coupling parameters between coils according to the selected coil parameters, including coupling coefficient k1、k2、kn……kn+1Etc.;
coil coupling coefficient k1、k2、kn……kn+1Determined by factors such as the distance and relative position of each coil, M1Mutual inductance being the coupling coefficient of the transmitter coil and the 1 st relay coil, M2～MnFor mutual inductance between relay coils, Mn+1For the mutual inductance between the nth relay coil and the receiving coil, the mutual inductance between the resonance coils, the coupling coefficient and the coil inductance value need to satisfy the following relations:
mutual inductance between the coils can affect the transmission power of the system, and further affect the electromagnetic interference condition of the system.
And 4, step 4: establishing a system electromagnetic interference model, and adding system parasitic parameters; including the associated parasitic capacitance, C, in the system conducted interference model circuit of fig. 1qIs two MOSFET switching tubes S1、S2Equivalent parasitic capacitance to ground, C11And C12Is the parasitic capacitance between the system transmitter coil and the 1 st relay coil, and, similarly, C21And C22Etc. are the parasitic capacitances between the 1 st relay coil and the 2 nd, Cn+1,1And Cn+1,2Is the parasitic capacitance between the nth relay coil and the receiving coil of the system, Ct、CrIs the parasitic capacitance to ground of the diode;
the parasitic parameter adding method of each device in the circuit comprises the following steps:
1) for parasitic parameters between coils, different k values can cause C in a system conducted interference model in practical application process11And C12The parasitic capacitance between the coils changes, and then the electromagnetic interference on the output side is influenced. When the coil coupling coefficient k is increased, the coil distance is close, the relative area is large, C11And C12The magnitude of the capacitance is obtained according to the following calculation formula of the plate capacitance:
wherein S is the facing area of the two plates of the capacitor, d is the distance between the two plates of the capacitor, epsilon is the dielectric constant, and k1 is the electrostatic constant.
2) For the parasitic parameters of the switching device, the relative area between the plates is obtained by searching the device manual MOSFET switching tube, the plate spacing is properly estimated, and the equivalent earth parasitic capacitance C can be calculated according to the formula (3)qTaking values, the parasitic capacitance C to the ground of the diode can be calculated in the same wayt、CrThe value of (c).
And 5: taking the wireless charging system model containing a relay coil in fig. 2 as an example, waveforms of common-mode and differential-mode interference signals at the input side and the output side when the power is large are obtained through simulation;
taking the electromagnetic interference model circuit of the system including a relay coil in fig. 2 as an example, the coil coupling coefficient and the load R at the time of larger output power are selected according to the calculation of the power of the systemLThe coupling coefficient of each coil is 0.02 in the invention, and the load R isLIn the present invention 10 Ω is taken. The simulation results when the input voltage is 10V and the resonant frequency is 1M are shown in FIGS. 3-6.
Step 6: taking the wireless charging system model with one relay coil in fig. 2 as an example, the simulation result is analyzed to provide guidance for electromagnetic interference suppression of the actual system.
According to the simulation results of FIGS. 3-6, it can be seen that:
(1) the input side common mode interference is the most serious and far larger than the differential mode interference, and the maximum value reaches 92.763dB when the resonant frequency is 1M. The common mode interference at the input side mainly comes from the quick on-off of the switching tube, and the interference value is obtained by extracting the parasitic capacitance. Corresponding measures can be taken in subsequent designs to suppress common-mode interference thereof.
(2) The interference is most severe at the resonance frequency in the frequency spectrum and more severe at integer multiples of the resonance frequency. In practical application, the frequency band needs to be paid more attention, and corresponding measures can be taken in subsequent design to suppress the interference of the frequency band.
Claims (8)
1. The electromagnetic interference prediction circuit is characterized by comprising a resonance network and an input side inverter circuit connected to the input end of the resonance network, wherein the input end of the input side inverter circuit is connected with a direct current input power supply; the filter circuit also comprises an output side rectifying circuit connected with the output end of the resonant network and a filter capacitor connected in parallel with the output side rectifying circuit;
the resonant network comprises a transmitting side resonant network connected with the input side inverter circuit, a receiving side resonant network connected with the output side rectifier circuit, and a relay coil resonant network connected between the transmitting side resonant network and the receiving side resonant network, wherein parasitic capacitors are connected between the relay coil resonant network and the transmitting side resonant network as well as between the relay coil resonant network and the receiving side resonant network;
the relay coil resonance network comprises n relay coils, wherein n is more than or equal to 1, and a parasitic capacitor is connected between adjacent relay coils;
the input side inverter circuit is a half-bridge inverter circuit, the half-bridge inverter circuit comprises two switching tubes which are connected in series, a capacitor is connected between a source electrode and a drain electrode of each switching tube, and a ground capacitor is connected between the center of a half bridge, namely the connecting middle point of the two switching tubes, and the ground; the transmitting side resonant network comprises a transmitting coil consisting of a capacitor, an inductor and a resistor which are connected in series, and the transmitting coil is connected between the connection midpoint of the two switching tubes and the negative electrode of the direct-current input power supply;
the output side rectifying circuit is a full-bridge rectifying circuit, four diodes are connected in parallel after being connected in series in pairs, a capacitor is connected in parallel between the positive electrode and the negative electrode of each diode, a ground capacitor is connected between the middle point of each bridge arm and the ground, the receiving side resonant network comprises a receiving coil consisting of a capacitor, an inductor and a resistor which are connected in series, and the receiving coil is connected between the middle points of the two bridge arms;
the electromagnetic interference prediction circuit is characterized in that input voltage is direct current, the input voltage is connected with a transmitting side resonance network in a resonance network through an input side inverter circuit, a receiving side resonance network is connected with an output side rectifier circuit, and the direct current voltage is output through capacitance filtering;
the device comprises a plurality of coupling resonance coils Lp, L1, L2, Ln and Ls, wherein the magnetic resonance coupling among the coupling coils is utilized to realize the transmission of electric energy;
inter-turn capacitances C11 and C12 exist between the coupling coils Lp and L1, coil resistances R1 and C1 exist in the coupling coil L1, inter-turn capacitances C21 and C22 exist between the coupling coils L1 and L2, and coil resistances R2 and C2 exist in the coupling coil L2; the coupling coil Ls and the capacitors Cs and Rs form a receiving side resonant network and are connected to the input end of the full-bridge rectification circuit;
a first end of the resonance coil Lp is connected to one end of a capacitor C11, the other end of the capacitor C11 is connected to a first end of the resonance coil L1, and a second end of the resonance coil Lp is connected to the resistor Rp; a second end of the resonant coil Lp is connected to the source of the switching tube S2 through the resistor Rp, and the other end of the capacitor C12 is connected to a second end of the resonant coil L1; a first end of the resonant coil L1 is connected to a first end of the resonant inductor L2 through a capacitor C21, a 2 nd end of the resonant inductor L1 is connected to a second end of the resonant inductor L2 through a capacitor C22, and Lp and the capacitors Cp and Rp form a transmitting-side resonant network;
a first end of the resonant coil L2 is connected to one end of a capacitor C31, the other end of the capacitor C31 is connected to a first end of the resonant coil L3, and a second end of the resonant coil L2 is connected to a resonant inductor L3 through a capacitor C32; the relay resonant network formed by the resonant coil L2 and the resistor R2 and the capacitor C2 further comprises a direct-current voltage source DC, the drain electrode of the switching tube S1 is connected to the positive electrode of the direct-current voltage source DC, the source electrode of the switching tube S2 is connected to the negative electrode of the direct-current voltage source DC, the switching tube S1 and the switching tube S2 form a half-bridge inverter circuit, capacitors are connected between the source electrodes and the drain electrodes of the switching tubes S1 and S2 respectively, and the drain electrode of the switching tube S2 is grounded through the capacitor Cp;
the full-bridge rectifier circuit is composed of diodes D1, D2, D3 and D4, wherein the diode D1 is connected with the output end of the diode D2, the diode D3 is connected with the input end of the diode D4, the input end of the diode D1 is connected with the output end of the diode D3, and the input end of the diode D2 is connected with the output end of the diode D4; a first end of the resonance coil L2 is connected to an input end of the diode D1 through the capacitor C2 and the resonance coil Lf2 in sequence, a second end of the resonance coil L2 is connected to an input end of the diode D2 through the resistor R2, and an input end of the diode D2 is connected between the capacitor C2 and the resonance coil Lf2 through the capacitor Cf 2;
capacitors are respectively connected between the input ends and the output ends of the diodes D1, D2, D3 and D4; the output end of the diode D3 is grounded through a capacitor Ct, and the output end of the diode D4 is grounded through a capacitor Cr; the output end of the diode D2 is connected to the input end of the diode D4 through a capacitor C3, a capacitor C4 is connected in parallel to both ends of the capacitor C3, and a resistor RL serving as a load is connected in parallel to both ends of the capacitor C3.
2. The relay coil-containing resonant wireless charging system electromagnetic interference prediction circuit of claim 1, wherein the filter capacitor comprises a high frequency filter capacitor and a low frequency filter capacitor.
3. The relay coil-containing resonant wireless charging system electromagnetic interference prediction circuit of claim 1, wherein each relay coil comprises a capacitor, an inductor and a resistor connected in series, wherein a parasitic capacitor is arranged between the inductors of adjacent relay coils, and two ends of each inductor are connected through two parasitic capacitors.
4. The method for predicting the electromagnetic interference of the wireless resonant charging system with the relay coil is characterized by adopting the electromagnetic interference prediction circuit of the wireless resonant charging system with the relay coil, which is disclosed by any one of claims 1 to 3, and comprises the following steps of:
step 1), determining system parameters including input voltage U, resonant frequency f, transmitting side resonant inductance L1, Lf1 and resonant capacitance C1, Cf1 receiving side resonant inductance L2, Lf2 and resonant capacitance C2, Cf2, coil coupling coefficient k and load RL;
step 2), establishing a system electromagnetic interference model, and adding system parasitic parameters;
step 3), simulating and calculating the waveforms of common-mode and differential-mode interference signals at the output side in different working states;
in the step 1), firstly, the input voltage U and the working frequency f are determined, and the resonant network capacitance inductance parameter satisfying the formulas (1a) to (1d) is selected according to the working frequency:
jωLf1＝1/jωCf1(1a)
jωLf2＝1/jωCf2(1b)
jωL1-1/jωC1＝1/jωCf1(1c)
jωL2-1/jωC2＝1/jωCf2(1d)
where ω is 2 pi f, the load RL may affect the system output power and the electromagnetic interference, and is also considered as a variable, and ideally, the transmission power of the resonant network is expressed as follows:
wherein, the effective value of the input and output voltage of the Uin and Uout resonant network, Uout is influenced by the load, M is the mutual inductance between the resonant coils L1 and L2; the coil coupling coefficient k is determined by the coil distance and the relative position, influences the transmission power of the system and is regarded as variable processing in the invention;
the capacitance Cp is the equivalent parasitic capacitance to ground of the two MOSFET switch tubes S1, S2, the capacitances Cs1 and Cs2 are the parasitic capacitances between the system transmitting coil and the system receiving coil, the capacitances Ct, Cr are the parasitic capacitances to ground of the diodes, and the parasitic parameter adding method of each device in the circuit is as follows:
the capacitance values of the capacitances Cs1, Cs2, Cp, Ct, Cr are obtained according to the plate capacitance calculation formula (4):
wherein S is the opposite area of the two polar plates of the capacitor, d is the distance between the two polar plates of the capacitor, epsilon is the dielectric constant, and k1 is the electrostatic constant;
when the coil coupling coefficient k is increased, the coil distance is short, the relative area is large, the Cs1 and the Cs2 are increased, and the capacitance values of the Cs1 and the Cs2 are obtained according to the plate capacitance calculation formula (4);
the relative area between the plates is obtained by searching a device manual MOSFET switching tube, the plate interval is properly estimated, the equivalent earth parasitic capacitance Cp value can be calculated according to a formula (4), and the values of the earth parasitic capacitances Ct and Cr of the diode can be calculated in the same way.
5. The method for predicting electromagnetic interference of the wireless resonant charging system with the relay coil according to claim 4, wherein in the step 2, the coil resonant network parameter is related to the operating frequency f, and an inductor with a corresponding inductance value is wound according to a selected capacitance value, wherein:
the resonance network parameters and the working frequency of the relay coil satisfy the following relations:
jωLn＝1/jωCn(1-n)
the resonant network parameters of the transmitting side coil and the working frequency satisfy the following relations:
jωLp＝1/jωCp(1-p)
the resonance network parameters of the receiving side coil and the working frequency satisfy the following relations:
jωLs＝1/jωCs(1-s)
where ω is 2 pi f.
6. The method for predicting electromagnetic interference of the wireless charging system with the resonance type of the relay coil according to claim 4, wherein in the step 3:
determining coupling parameters between the coils according to the coil resonance network parameters determined in the step 2, wherein the coupling parameters comprise a coupling coefficient k1～kn、kn+1Then determining the mutual inductance M between the coils based on the coupling coefficient1～Mn、Mn+1The mutual inductance between the resonance coils, the coupling coefficient and the coil inductance value satisfy the following relationship, wherein:
M1mutual inductance, which is the coupling coefficient of the transmitter coil and the 1 st relay coil:
M2～Mnmutual inductance between relay coils:
Mn+1mutual inductance between the nth relay coil and the receiving coil:
7. the method for predicting electromagnetic interference in a wireless charging system with a resonance type of relay coil as claimed in claim 6, wherein in step 3, the coil coupling coefficient is determined by the distance and relative position of each coil and the properties of the surrounding magnetic medium.
8. The method for predicting the electromagnetic interference of the wireless charging system with the resonance type of the relay coil according to claim 4, wherein in the step 4, the parasitic parameters of each device in the circuit are determined by the following method:
1) for the parasitic capacitance parameter between the coils, the magnitude is obtained according to the following calculation formula of the plate capacitance:
wherein S is the facing area of the two plates of the capacitor, d is the distance between the two plates of the capacitor, epsilon is the dielectric constant, k1Is the electrostatic constant;
2) for the parasitic capacitance parameters of the switching device and the diode, the inter-board relative area and the inter-board distance are obtained by searching a device manual MOSFET switching tube, the equivalent earth parasitic capacitance Cq value is calculated according to a formula (3), and the earth parasitic capacitance value of the diode is calculated in the same way.
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| CN111022276B (en) * | 2019-12-27 | 2021-03-12 | 哈尔滨工业大学 | Hall effect thruster low-frequency oscillation suppression outer loop |
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| CN115664054B (en) * | 2022-12-29 | 2023-03-14 | 成都西交轨道交通技术服务有限公司 | Vehicle-ground multi-load synchronous wireless power supply system based on relay polar plate |
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