CN113364143A - Wireless charging method and device based on shielding characteristic of magnetic material - Google Patents
Wireless charging method and device based on shielding characteristic of magnetic material Download PDFInfo
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- CN113364143A CN113364143A CN202110600697.6A CN202110600697A CN113364143A CN 113364143 A CN113364143 A CN 113364143A CN 202110600697 A CN202110600697 A CN 202110600697A CN 113364143 A CN113364143 A CN 113364143A
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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
- H02J50/90—Circuit arrangements or systems for wireless supply or distribution of electric power involving detection or optimisation of position, e.g. alignment
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Abstract
The invention discloses a wireless charging method and a wireless charging device based on the shielding characteristic of a magnetic material, wherein the shielding characteristic of the magnetic material is combined with resonant wireless charging, experimental tests and theoretical researches find that the split frequency phenomenon of a coil occurs under the condition of adjusting the frequency, the transmission efficiency of the coil is influenced, and the load resistance is calculated when the split frequency phenomenon is eliminated, so that the transmission efficiency of the wireless charging is improved; the reason that the output power of the magnetic material is reduced when the output current is high is analyzed, the mutual inductance coefficient corresponding to the maximum efficiency value is obtained through simulation, and the corresponding distance between the mutual inductance coefficient and the magnetic material is obtained, so that the transmission efficiency is maximized, and the performance of the wireless charging device is improved; the invention also provides a wireless charging device, and a user places the charging device and the charged equipment according to the distance by arranging the automatic distance measuring module, so that the charging efficiency is improved, and the charging time is shortened.
Description
Technical Field
The invention belongs to the technical field of wireless charging, and particularly relates to a wireless charging method and device based on the shielding characteristic of a magnetic material.
Background
At present, the portable electronic product is mainly charged through a specific wired charger, and a large number of charging ports are used, so that material resources are wasted. The wireless charging technology has wide application prospect in the future electronic market. The inductively coupled transmitter coil and receiver coil are separate, which can create a large leakage inductance. And by utilizing resonant wireless power transmission, a magnetic field is used as a medium for wireless power transmission, the natural frequency of the receiving coil is consistent with the transmitting frequency through resonance between the transmitting coil and the receiving coil, strong electromagnetic coupling is generated, a power transmission channel is established, and wireless power transmission is realized. Different from electromagnetic induction type coupling, resonant wireless power transmission can improve the transmission distance to several meters, and can ensure certain transmission distance and efficiency. When the ferrite is added to the two coil ends respectively, the coupling coefficient between the coils can be improved, and further the transmission efficiency is improved.
However, how to further improve the transmission efficiency is a goal that those skilled in the art are continuously pursuing.
Disclosure of Invention
In view of the above, the present invention provides a wireless charging method and apparatus based on shielding characteristics of a magnetic material, which can improve transmission efficiency during wireless charging.
A wireless charging method based on the shielding characteristic of a magnetic material is characterized in that a primary coil charges a secondary coil through electromagnetic induction, wherein a capacitor, a resistor and an inductor which are connected in series in the primary coil are respectively and correspondingly set as a capacitor C1Resistance R1And self inductance L1The capacitance, resistance and self-inductance coefficient of the secondary coil are respectively set as capacitance C2Resistance R2And self inductance L2The load resistor connected in series in the secondary winding is set as a resistor RL(ii) a During charging, the resistance R is calculated and setLThe value of (c) is such that there is only one resonant frequency between the primary coil and the secondary coil, wherein the calculation method is:
the inductance, capacitance and resistance of the primary coil and the secondary coil are all the same, namely L1＝L2＝L,R1＝R2＝R，C1＝C2C; then
Wherein, ω is1And ω2Respectively representing the other two split resonance frequencies between the primary coil and the secondary coil, wherein M is a mutual inductance coefficient; when the mutual inductance M, the self-inductance L, the capacitance C and the resistance R are set values, let omega1＝ω2＝ω0(ii) a Wherein, ω is0Which is indicative of the resonant frequency,
solving the formula (1) to calculate the resistance value RLAdjusting the load resistance of the secondary winding to RLAnd then wireless charging is carried out.
Furthermore, after magnetic materials are added near the primary coil and the secondary coil to improve the self-inductance coefficient, a group of mutual inductance coefficient M, self-inductance coefficient L and input frequency f value of the primary coil are obtained by traversing the mutual inductance coefficient M, the self-inductance coefficient L and the input frequency f of the primary coil, so that the transmission efficiency between the primary coil and the secondary coil is maximum.
Preferably, the magnetic material is ferrite.
Preferably, matlab is used to traverse the mutual inductance M, the self-inductance L and the input frequency f of the primary coil.
Further, after obtaining a group of mutual inductance M and self-inductance L which enable the transmission efficiency to be maximum and an input frequency f value of the primary coil, calculating the maximum transmission efficiency at the moment; measuring mutual inductance M of the magnetic material when the distance d between the magnetic material and the primary coil and the distance d between the magnetic material and the secondary coil are different, and fitting a functional relation between the distance d and the mutual inductance M; finding the distance between the magnetic material and the coil corresponding to the value of the mutual inductance coefficient when the transmission efficiency is maximum in the function relation, and obtaining the position of the magnetic material at the maximum transmission efficiency; when charging, the magnetic material is placed in this position.
A device for realizing a wireless charging method based on the shielding characteristic of a magnetic material is characterized in that a distance measuring module is arranged in a charged device; the distance measuring module stores the function relation of the distance d to the mutual inductance coefficient M; and meanwhile, the distance measuring device is also used for measuring the distance between the magnetic material and the charging device, obtaining the required distance between the magnetic material and the charging device according to the value of the mutual inductance coefficient M between the current charging device and the charged device, and providing the distance for users.
Preferably, the charged device is a mobile communication device.
Preferably, the mobile communication device is a mobile phone.
The invention has the following beneficial effects:
the invention combines the shielding characteristic of the magnetic material with the resonant wireless charging, finds that the split frequency phenomenon of the coil occurs when the frequency is adjusted through experimental tests and theoretical researches, influences the transmission efficiency of the coil, and calculates the load resistance when the split frequency phenomenon is eliminated, thereby improving the transmission efficiency of the wireless charging;
and the reason that the output power of the magnetic material added under the condition of high output current is reduced is analyzed, the mutual inductance coefficient corresponding to the maximum efficiency value is obtained through simulation, and the corresponding distance between the mutual inductance coefficient and the magnetic material is obtained, so that the transmission efficiency is maximized, and the performance of the wireless charging device is improved.
The invention also provides a wireless charging device, and a user places the charging device and the charged equipment according to the distance by arranging the automatic distance measuring module, so that the charging efficiency is improved, and the charging time is shortened.
Drawings
FIG. 1 is a circuit diagram of a wireless charging string-string compensation structure experiment;
FIG. 2(a) is a graph of output power versus frequency with a split frequency, and FIG. 2(b) is a graph of transmission efficiency versus frequency with a split frequency;
FIG. 3(a) is a graph of frequency output power versus frequency for the cancellation of splitting, and FIG. 3(b) is a graph of frequency efficiency versus frequency for the cancellation of splitting;
FIG. 4 is a diagram illustrating a multi-factor challenge;
FIG. 5(a) is a graph of mutual inductance, frequency versus output power, and FIG. 5(b) is a graph of mutual inductance versus output power;
FIG. 6 is a graph of distance of magnetic material from coil versus mutual inductance.
Detailed Description
The invention is described in detail below by way of example with reference to the accompanying drawings.
The magnetic field is used as a medium for wireless power transmission, the natural frequency of the receiving coil is consistent with the transmitting frequency through resonance between the transmitting coil and the receiving coil, strong electromagnetic coupling occurs, a power transmission channel is established, and wireless power transmission is achieved. Its resonant frequency becomes the resonant frequency. The resonance frequency between the two coils is as follows:
at the resonant frequency, the impedance is at a minimum and the output power is at a maximum. The circuit adopts a series-series structure, as shown in fig. 1, a transmitting coil on the left side is a primary coil, and a receiving coil is a secondary coil. And calculating a formula of theoretical value power and transmission efficiency by using kirchhoff voltage law, and comparing the theoretical value with the measured actual value.
Wherein:
ZP＝RS+R1+jwL1+1/jwC1； (4)
ZS＝RL+R2+jwL2+1/jwC2； (5)
where ω is the input frequency, C1，C2The size of the capacitance used for the transmitter coil and receiver coil, M being the mutual inductance, UinFor the magnitude of the input voltage, RLIs a load resistance of the secondary side, ISIs the magnitude of the output current.
Experimental tests show that in most cases, after data of voltage, resistance, capacitance and inductance are fixed, input frequency is adjusted, two to three resonance peaks are found, and the more the resonance peaks are, the output power of the resonance peaks under the resonance frequency is reduced. In order to investigate this phenomenon, the present invention makes the following theoretical calculation, and finds and eliminates the frequency splitting phenomenon, as shown in fig. 2(a), (b).
According to the mutual inductance theory and the transformer principle, after the secondary side impedance is equivalent to the primary side coil, the impedance change is as follows:
the equivalent total impedance of the system is therefore:
wherein: zpIs the total impedance of the primary winding, RocThe impedance of the secondary winding equivalent to the primary winding.
The inductance, the capacitance and the resistance of the primary coil and the secondary coil of the selected circuit are the same. Namely L1＝L2＝L，R1＝R2＝R，C1＝C2＝C。
When Z isinThe output power is maximum at 0, where three resonant frequencies occur:
wherein w1，w2For two split frequency values, w0Is the value of the resonant frequency.
At the moment, parameters of a mutual inductance M, a self-inductance L, a capacitance C and a resistance R are fixed, and omega is controlled1＝ω2＝ω0The load resistance value at which frequency division does not occur is obtained, and the division frequency is eliminated as shown in fig. 3(a) and 3 (b).
In this embodiment, in order to eliminate the frequency splitting, the splitting frequency is eliminated after the resistance value of the load resistor is adjusted. However, the transmission efficiency is not increased and the transmission efficiency and the output power are continuously decreased by adding the magnetic material.
Through experimental tests and theoretical researches, the influence factors are found to be summarized as follows: 1. eddy currents cause a reduction in output power; 2. the ferrite is added to cause the self-inductance coefficient to be increased, the resonance frequency to be reduced and the curve to be shifted to the left; 3. the increase in the mutual inductance results in an increase in output power.
As shown in FIG. 4, the dotted line is the curve of the power of the coil with frequency without the addition of the magnetic material, f0Corresponding to the original resonant frequency. After the ferrite magnetic material is added, the self-inductance coefficient of the original coil is increased due to the magnetic material, so that the resonance frequency is reduced, and the curve after the ferrite is added is shifted to the left (a solid line after the movement), and is f0The corresponding power value decreases. And the output power is increased due to the increase of the mutual inductance coefficient after the ferrite is added, and the curve is shifted upwards, so the output power is increased again at the resonance frequency of the coil. Finally, the coil moves downwards due to the action of the eddy current. Thus shifting curve f0The corresponding output power has uncertainty, and the result is that various factors resist each other.
The graph of the variation of the output power with the mutual inductance and the operating frequency is shown, and as shown in fig. 5(a), it is understood that the splitting frequency phenomenon occurs when the mutual inductance is larger. As shown in fig. 5(b), the output power tends to increase first and then decrease as the mutual inductance increases. Therefore, MATLAB is used for traversing the mutual inductance M, the input frequency f of the primary coil and the self-inductance L to obtain the maximum value of the transmission efficiency.
And traversing the self-inductance coefficient L, the mutual inductance coefficient M and the frequency f by using MATLAB to obtain each value enabling the efficiency to be maximum and a corresponding maximum transmission efficiency value. And measuring the mutual inductance coefficient of the coil when the ferrite distance is different, fitting a function of the distance between the magnetic material and the coil and the mutual inductance coefficient, finding the distance between the ferrite and the coil corresponding to the mutual inductance coefficient value when the transmission efficiency is maximum in the function relation, and obtaining the position of the magnetic material at the maximum transmission efficiency. The results of the experiment are shown in FIG. 6.
Based on the above conclusion, the present invention provides a magnetic material moving device that maximizes transmission efficiency: a distance measurement module is arranged in the charged device; the distance measuring module stores the function relation of the distance d to the mutual inductance coefficient M; and meanwhile, the distance measuring device is also used for measuring the distance between the magnetic material and the charging device, obtaining the required distance between the magnetic material and the charging device according to the value of the mutual inductance coefficient M between the current charging device and the charged device, and providing the distance for users.
The charged device can be a mobile phone, a built-in module of the mobile phone automatically measures the distance, and then the distance between the magnetic material and the mobile phone when the transmission efficiency is maximum can be determined according to the functional relation between the distance between the magnetic material and the coil and the mutual inductance coefficient, so that the position of the magnetic material is adjusted, and the output power of the transmission efficiency is maximum at the position.
In summary, the above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (8)
1. A wireless charging method based on the shielding characteristic of a magnetic material is characterized in that a primary coil charges a secondary coil through electromagnetic induction, wherein a capacitor, a resistor and an inductor which are connected in series in the primary coil are respectively and correspondingly set as a capacitor C1Resistance R1And self-inductanceCoefficient L1The capacitance, resistance and self-inductance coefficient of the secondary coil are respectively set as capacitance C2Resistance R2And self inductance L2The load resistor connected in series in the secondary winding is set as a resistor RLCharacterized in that, during charging, the resistance R is calculated and setLThe value of (c) is such that there is only one resonant frequency between the primary coil and the secondary coil, wherein the calculation method is:
the inductance, capacitance and resistance of the primary coil and the secondary coil are all the same, namely L1＝L2＝L,R1＝R2＝R，C1＝C2C; then
Wherein, ω is1And ω2Respectively representing the other two split resonance frequencies between the primary coil and the secondary coil, wherein M is a mutual inductance coefficient; when the mutual inductance M, the self-inductance L, the capacitance C and the resistance R are set values, let omega1＝ω2＝ω0(ii) a Wherein, ω is0Which is indicative of the resonant frequency,
solving the formula (1) to calculate the resistance value RLAdjusting the load resistance of the secondary winding to RLAnd then wireless charging is carried out.
2. The wireless charging method based on the shielding property of the magnetic material as claimed in claim 1, wherein after the magnetic material is added near the primary coil and the secondary coil to improve the self-inductance, a set of mutual inductance M, self-inductance L and input frequency f of the primary coil is obtained by traversing the mutual inductance M, the self-inductance L and the input frequency f of the primary coil, so that the transmission efficiency between the primary coil and the secondary coil is maximized.
3. The wireless charging method based on the shielding property of the magnetic material as claimed in claim 2, wherein the magnetic material is ferrite.
4. The wireless charging method based on the shielding property of the magnetic material as claimed in claim 2, wherein matlab is used to traverse the mutual inductance M, the self-inductance L and the input frequency f of the primary coil.
5. The wireless charging method based on the shielding property of the magnetic material as claimed in claim 2, 3 or 4, wherein after obtaining a set of mutual inductance M and self-inductance L which maximize the transmission efficiency and the input frequency f of the primary coil, the maximum transmission efficiency at that time is calculated; measuring mutual inductance M of the magnetic material when the distance d between the magnetic material and the primary coil and the distance d between the magnetic material and the secondary coil are different, and fitting a functional relation between the distance d and the mutual inductance M; finding the distance between the magnetic material and the coil corresponding to the value of the mutual inductance coefficient when the transmission efficiency is maximum in the function relation, and obtaining the position of the magnetic material at the maximum transmission efficiency; when charging, the magnetic material is placed in this position.
6. A device for realizing the wireless charging method based on the shielding characteristic of the magnetic material in the claim 5 is characterized in that a distance measuring module is arranged in the charged device; the distance measuring module stores the function relation of the distance d to the mutual inductance coefficient M; and meanwhile, the distance measuring device is also used for measuring the distance between the magnetic material and the charging device, obtaining the required distance between the magnetic material and the charging device according to the value of the mutual inductance coefficient M between the current charging device and the charged device, and providing the distance for users.
7. The apparatus of claim 6, wherein the charged apparatus is a mobile communication device.
8. The apparatus of claim 7, wherein the mobile communication device is a mobile phone.
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104135088A (en) * | 2014-08-08 | 2014-11-05 | 哈尔滨工业大学 | Non-identical transmitting and receiving coil pair applicable to wireless power transmission and capable of restraining frequency splitting and manufacturing method of non-identical transmitting and receiving coil pair |
| US20160336810A1 (en) * | 2015-05-12 | 2016-11-17 | The Regents Of The University Of Michigan | Nonlinear Resonance Circuit For Wireless Power Transmission And Wireless Power Harvesting |
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- 2021-05-31 CN CN202110600697.6A patent/CN113364143A/en active Pending
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104135088A (en) * | 2014-08-08 | 2014-11-05 | 哈尔滨工业大学 | Non-identical transmitting and receiving coil pair applicable to wireless power transmission and capable of restraining frequency splitting and manufacturing method of non-identical transmitting and receiving coil pair |
| US20160336810A1 (en) * | 2015-05-12 | 2016-11-17 | The Regents Of The University Of Michigan | Nonlinear Resonance Circuit For Wireless Power Transmission And Wireless Power Harvesting |
Non-Patent Citations (2)
| Title |
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| 李光 等: "磁谐振式无线电源系统的传输性能研究", 《通信管理与技术》 * |
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Application publication date: 20210907 |