CN110224506B - Metal foreign matter detection system of series wireless power transmission system - Google Patents
Metal foreign matter detection system of series wireless power transmission system Download PDFInfo
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- CN110224506B CN110224506B CN201910621938.8A CN201910621938A CN110224506B CN 110224506 B CN110224506 B CN 110224506B CN 201910621938 A CN201910621938 A CN 201910621938A CN 110224506 B CN110224506 B CN 110224506B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
- G01V3/08—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices
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- H—ELECTRICITY
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- 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
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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
- H02J50/60—Circuit arrangements or systems for wireless supply or distribution of electric power responsive to the presence of foreign objects, e.g. detection of living beings
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Abstract
A metal foreign matter detection system of a string type wireless power transmission system belongs to the technical field of metal foreign matter detection in wireless power transmission. The invention aims at the problems that the existing wireless power transmission system has low detection sensitivity to metal foreign matters and requires the coaxial transmitting and receiving coils. The high-frequency square wave power supply is used for providing voltage signals which can be decomposed into fundamental waves and various odd harmonics for the transmitting unit of the wireless electric energy transmission system; the receiving unit of the wireless electric energy transmission system comprises fundamental wave energy transfer current; the detection unit is used for detecting the coil set and generating induction voltage based on the transmitting coil; the conversion unit is used for sequentially filtering, rectifying and conditioning the induction voltage to obtain an adjusted amplitude of the induction voltage; the control unit is used for controlling the on-off and the frequency of the high-frequency square wave power supply. On the basis of realizing the detection of the metal foreign matters, the invention does not influence the electric energy transmission, has the advantage of high detection sensitivity, and does not influence the detection effect when the receiving and transmitting coils of the electric energy transmission system are dislocated.
Description
Technical Field
The invention relates to a metal foreign matter detection system of a series wireless power transmission system, and belongs to the technical field of metal foreign matter detection in wireless power transmission.
Background
The magnetic coupling resonance type wireless power transmission technology takes an electromagnetic field as a power transmission medium, adopts a resonance principle, improves transmission efficiency and distance, weakens the requirement on the relative position of a coil, and is safer and more reliable.
Since the magnetic coupling resonant wireless power transmission technology is not a fitting type transmission, a metal foreign matter may occur in a transmission space. The existence of the metal foreign matters can change the electromagnetic parameters of the electric energy receiving and transmitting coil, and the resonance point shifts; meanwhile, eddy current loss occurs inside the metal foreign body, and the electric energy transmission performance of the system is also poor. Excessive eddy current loss locally overheats the metal foreign bodies, which may cause fire hazard and the like.
In order to reduce the influence of the metal foreign matter on the performance and safety of the power transmission system, the metal foreign matter is generally detected and removed. At present, the detection methods for metal foreign matter can be roughly divided into three types: non-electromagnetic detection, magnetic field detection, and system parameter detection. The first two detection methods will add extra equipment and cost; the third detection method needs to add part of circuits, but the existing third detection method has limited detection sensitivity to small-size metal foreign matters, and the foreign matters can be detected only by coaxial transceiver coils.
Therefore, in view of the above disadvantages, it is desirable to provide a new metallic foreign object detection system, so as to improve the sensitivity of metallic foreign object detection, reduce the requirement for the coaxiality of the transceiver coil, and obtain reliable detection results when the transceiver coil is misaligned.
Disclosure of Invention
The invention provides a metal foreign matter detection system of a series type wireless power transmission system, aiming at the problems that the detection sensitivity of the metal foreign matter in the existing wireless power transmission system is low and the receiving and transmitting coils are required to be coaxial.
The invention relates to a metal foreign matter detection system of a serial wireless power transmission system, which comprises a high-frequency square wave power supply, a transmitting part resonance branch, a receiving part resonance branch, a detection unit, a conversion unit and a control unit,
the receiving part resonance branch circuit is used for being connected in series between a load resistor and a receiving coil of a receiving unit of the wireless power transmission system;
the high-frequency square wave power supply is used for providing voltage signals which can be decomposed into fundamental waves and various odd harmonics for the transmitting unit of the wireless electric energy transmission system, so that the transmitting unit of the wireless electric energy transmission system comprises fundamental wave energy transfer current and high-order detection current; the receiving unit of the wireless electric energy transmission system comprises fundamental wave energy transfer current;
the detection unit is used for detecting the coil set and generating an induction voltage based on the emission coil; the detection coil set and the emission coil are coaxially arranged, and the lower surface of the detection coil set is closely adjacent to the upper surface of the emission coil;
the conversion unit is used for sequentially filtering, rectifying and conditioning the induction voltage to obtain an adjusted amplitude of the induction voltage;
the control unit is used for controlling the on-off and the frequency of the high-frequency square wave power supply, judging whether metal foreign bodies exist according to the standard amplitude of the induction voltage and the adjustment amplitude of the induction voltage, and switching off the high-frequency square wave power supply when the metal foreign bodies exist.
According to the metal foreign body detection system of the series-type wireless power transmission system, the detection coil sets of the detection unit comprise an upper detection coil set and a lower detection coil set, the upper detection coil set and the lower detection coil set are tightly connected, and the origin of coordinates are overlapped;
the upper detection coil set comprises a detection coil group C and a detection coil group D, the lower detection coil set comprises a detection coil group A and a detection coil group B, each detection coil group comprises two detection units, and the two detection units of the same detection coil group are connected in series in a reverse direction.
According to the metal foreign matter detection system of the series-type wireless power transmission system, the standard amplitude of the induction voltage of the four detection coils, which can be obtained by the conversion unit when no metal foreign matter exists in the wireless power transmission system, is obtained; and comparing the adjustment amplitude values of the induction voltages of the four detection coils obtained online by the conversion unit with corresponding standard amplitude values by using a control unit, and judging that metal foreign matters exist when the absolute value of a comparison result exceeds a preset threshold value.
According to the metal foreign object detection system of the string-type wireless power transmission system of the present invention, the transmitting unit of the wireless power transmission system includes the transmitting coil L t A transmitting coil connected in series with a capacitor C t And a transmitting part resonance branch circuit which is connected with a capacitor C d And an inductance L d Are connected in parallel;
make two resonance points omega of transmitting unit 1 And omega 2 Comprises the following steps:
A＝L d C d L t C t ，
B＝L d C d +L t C t +L d C t ，
make omega 1 ＝ω 0 ，ω 2 ＝nω 0 N is selected as an odd number; therefore, the transmitting unit of the wireless electric energy transmission system comprises fundamental wave energy transfer current and high-order detection current.
According to the metal foreign object detection system of the string type wireless power transmission system of the present invention, the receiving unit of the wireless power transmission system includes the receiving coil L r A receiving coil connected in series with a capacitor C r Receiving part resonance branch circuit and load resistor R L (ii) a The resonance branch of the receiving part is composed of a capacitor C b And an inductance L b Are connected in parallel;
according to the resonance point omega of the transmitting unit 2 To the capacitor C b And an inductance L b And (3) selecting:
then according to the resonance point omega of the transmitting unit 0 Determining a receive coil series capacitance C r Comprises the following steps:
therefore, only the fundamental wave energy transfer current is contained in the receiving unit of the wireless electric energy transmission system.
According to the metal foreign matter detection system of the series wireless power transmission system, the conversion unit comprises a voltage following circuit, a filter circuit, a rectifying filter circuit and a conditioning circuit which are used for sequentially processing the induction voltage of the detection coil set; finally, the conditioning circuit outputs the adjusted amplitude of the induction voltage;
the voltage follower circuit is used for isolating the induced voltage of the detection coil set from a post-stage circuit;
the induced voltage is u 1 The output voltage of the voltage follower circuit is u 0 ；
The filter circuit is used for removing u 0 The fundamental component in the signal is kept from being attenuated by the n-th harmonic component to obtain a filtered voltage signal u 3 ；
The rectifying and filtering circuit is used for converting the voltage signal u 3 Obtaining a direct current voltage signal;
the adjusting circuit is used for obtaining the adjusting amplitude of the induction voltage from the direct-current voltage signal;
the filter circuit comprises a capacitor C 1 Capacitor C 2 Resistance R 1 Resistance R 2 Resistance R 3 Resistance R 4 And voltage follower U 1 ；
Output end of voltage follower circuit and voltage follower U 1 Between the non-inverting input ends of the capacitors C are connected in series in sequence 1 And a capacitor C 2 Resistance R 1 Connected to a voltage follower U 1 Between the non-inverting input terminal and the power ground, a voltage follower U 1 Is connected with the power ground through a resistor R 3 Voltage follower U 1 Between the inverting input terminal and the output terminal of the capacitor is connected with a resistor R 4 Voltage follower U 1 Is connected with the resistor R 2 One terminal of (1), resistance R 2 Is connected to the capacitor C at the other end 1 And a capacitor C 2 In the meantime.
According to the metal foreign matter detection system of the series wireless power transmission system, the rectification filter circuit comprises a diode D 1 Capacitor C f And a resistance R 5 ，
Diode D 1 Anode of (2) is connected with a voltage follower U 1 Output terminal of (2), diode D 1 A capacitor C is connected between the cathode of the anode and the power ground f Capacitance C f And a resistance R 5 Are connected in parallel.
The invention relates to a metal strip of a string-type wireless power transmission systemThe object detection system, the conditioning circuit comprises a diode D 2 Resistance R 6 Resistance R 7 Resistance R 8 Resistance R 9 And a voltage follower U 2 ，
Resistance R 6 Is connected to a diode D 1 Cathode and voltage follower U of 2 Between the non-inverting input terminal of, a diode D 2 Cathode of the capacitor is connected with a voltage follower U 2 Non-inverting input of, diode D 2 Anode of (2) is connected to power ground, resistor R 7 And diode D 2 Parallel voltage follower U 2 Is connected with the power ground through a resistor R 8 Voltage follower U 2 Is connected with the ground of the power supply through a resistor R 9 (ii) a Voltage follower U 2 The output terminal of the voltage regulator outputs the regulated amplitude of the induced voltage.
According to the metal foreign matter detection system of the series wireless power transmission system, n =9 is selected, and in order to prevent the 9 th harmonic component from being attenuated, the voltage u output by the voltage follower circuit is required 0 To voltage follower U 1 Output voltage signal u 3 The transfer function H(s) of (A) is:
in the formula, s is a virtual variable;
natural angular frequency ω of the filter circuit g Comprises the following steps:
voltage follower U 1 Closed loop gain A of F Comprises the following steps:
make R 1 ＝R 2 ，C 1 ＝C 2 Then the transfer function H(s) is simplified to：
According to the metal foreign matter detection system of the series wireless power transmission system, a core controller of the control unit is a DSP28335 control chip, and the DSP28335 control chip outputs 4 paths of PWM signals to control the on-off of the high-frequency square wave power supply switch tube.
The invention has the beneficial effects that: according to the invention, a transmitting part resonance branch and a receiving part resonance branch are added in the existing series-connection wireless power transmission system, so that a transmitting unit of the wireless power transmission system comprises fundamental wave energy transfer current and high-order detection current; the receiving unit of the wireless electric energy transmission system comprises fundamental wave energy transfer current; therefore, on the basis of realizing the detection of the metal foreign matters, the detection device does not influence the electric energy transmission, has the advantage of high detection sensitivity, and does not influence the detection effect when the receiving and transmitting coils of the electric energy transmission system are dislocated.
After a transmitting part resonance branch and a receiving part resonance branch are added, a transmitting loop unit is provided with a double resonance structure, is formed by connecting a series LC branch and a parallel LC branch in series and is provided with two resonance points, the low resonance point is equal to the frequency of a square wave power supply, the high resonance point is equal to n times of the frequency of the square wave power supply, n is a positive odd number, and when the system works, the transmitting loop unit mainly comprises fundamental wave current and n-th harmonic wave current; the receiving loop unit has a single resonance structure, and is connected with an LC parallel branch circuit with the frequency equal to the n-th harmonic frequency in series, the receiving loop unit has a resonance point equal to the frequency of the square wave power supply, and when the system works, the receiving loop unit only contains fundamental wave current. Therefore, the detection of the metal foreign matters is better realized on the basis of reliable transmission of electric energy.
Drawings
Fig. 1 is a block diagram illustrating a metal foreign object detection system of a serial wireless power transmission system according to the present invention;
fig. 2 is a schematic diagram of a connection circuit of a transmitting part resonance branch and a receiving part resonance branch between a transmitting unit and a receiving unit of a wireless power transmission system;
fig. 3 is a schematic structural view of a detection coil set;
FIG. 4 is a schematic diagram of an implementation circuit of the conversion unit;
fig. 5 is a graph of the conversion result of the conversion unit on the fundamental wave voltage signal; in the figure, 200mV/DIV represents 200 mV/grid, and 5 mus/DIV represents 5 mus/grid;
FIG. 6 is a graph of the conversion result of the conversion unit for an nth harmonic voltage signal;
fig. 7 is a diagram of initial voltage waveforms of the detection coil group a and the detection coil group C;
fig. 8 is an initial voltage waveform diagram of the detection coil group B and the detection coil group D;
fig. 9 is a graph of induced voltage waveforms of the detection coil group a and the detection coil group C when a foreign object is present in the wireless power transfer system.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.
The invention is further described with reference to the following drawings and specific examples, which are not intended to be limiting.
First embodiment, as shown in fig. 1 and 2, the present invention provides a metal foreign object detection system of a serial wireless power transmission system, which is characterized in that the system comprises a high-frequency square wave power source 1, a transmitting part resonance branch 2, a receiving part resonance branch 3, a detection unit 4, a conversion unit 5 and a control unit 6,
the transmitting part resonance branch circuit 2 is used for being connected in series between a capacitor and a transmitting coil of a transmitting unit of the wireless power transmission system, and the receiving part resonance branch circuit 3 is used for being connected in series between a load resistor and a receiving coil of a receiving unit of the wireless power transmission system;
the high-frequency square wave power supply 1 is used for providing voltage signals which can be decomposed into fundamental waves and various odd harmonics for a transmitting unit of the wireless power transmission system, so that the transmitting unit of the wireless power transmission system comprises larger fundamental wave energy transfer current and higher detection current; the receiving unit of the wireless electric energy transmission system comprises fundamental wave energy transfer current; the voltage amplitude of the high-frequency square wave power supply 1 is inversely proportional to the harmonic frequency; the high-frequency square wave power supply 1 can output a square wave voltage signal with the frequency of 90 kHz;
the detection unit 4 is used for generating an induced voltage based on the emission coil through the detection coil set; the detection coil set and the emission coil are coaxially arranged, and the lower surface of the detection coil set is closely adjacent to the upper surface of the emission coil but insulated from each other; that is, the lower surface of the detection coil set and the upper surface of the transmission coil are coaxially and tightly connected together without gaps.
The conversion unit 5 is used for sequentially filtering, rectifying and conditioning the induction voltage to obtain an adjusted amplitude of the induction voltage;
the control unit 6 is used for controlling the on-off and the frequency of the high-frequency square wave power supply 1, and comprises a step of judging whether metal foreign bodies exist according to the standard amplitude of the induction voltage and the adjustment amplitude of the induction voltage, and a step of turning off the high-frequency square wave power supply 1 when the metal foreign bodies exist. The control unit 6 can be a DSP controller, and the safety of the system is ensured when metal foreign matters exist. The metal foreign object detection system according to the present embodiment can be applied to a serial wireless power transmission system. The foreign object detection can be implemented by correspondingly connecting the transmitting part resonance branch 2 and the receiving part resonance branch 3 to a transmitting unit and a receiving unit of the wireless power transmission system. The design of transmission part resonance branch 2 is for making the transmitting element forms two resonant structure, can have the circuit of two kinds of frequencies simultaneously, and the parameter to receiving part resonance branch 3 is further designed again, can make the receiving element contain the resistance wave circuit to only contain the fundamental wave and pass the ability electric current, provide the basis for the foreign matter detects.
As shown in fig. 1, the receiving unit of the wireless power transmission system is connected to a load for supplying the obtained power to the load. The receiving unit of the wireless power transmission system is in electromagnetic field connection with the transmitting unit of the wireless power transmission system.
Further, as shown in fig. 3, the detection coil sets of the detection unit 4 include an upper detection coil set and a lower detection coil set, where the upper detection coil set and the lower detection coil set are tightly connected and the origin of coordinates coincide;
the upper detection coil set comprises a detection coil group C and a detection coil group D, the lower detection coil set comprises a detection coil group A and a detection coil group B, each detection coil group comprises two detection units, and the two detection units of the same detection coil group are connected in series in the reverse direction. For example, the detection coil group C includes a detection unit C1 and a detection unit C2, the detection coil group D includes a detection unit D1 and a detection unit D2, the detection coil group a includes a detection unit A1 and a detection unit A2, and the detection coil group B includes a detection unit B1 and a detection unit B2. As shown in fig. 3, the detection coil sets may be arranged in the order of C1, D2, C2, A1, B1, and B2, and A2 in that order. The detection coil group A, the detection coil group B, the detection coil group C and the detection coil group D are mutually independent and are not connected by a lead. Each detection coil group is provided with two ports for connecting the conversion unit, and when the system works, the induction voltage of the detection coil group can be changed by the occurrence of metal foreign matters.
In this embodiment, the size parameters of the detection coil array can be determined by finite element simulation.
Still further, the standard amplitude values of the induced voltages of the four detection coils, which can be obtained by the conversion unit 5 when no metal foreign matter exists in the wireless power transmission system, are obtained; and the control unit 6 is adopted to compare the adjusted amplitude values of the induction voltages of the four detection coils obtained online by the conversion unit 5 with the corresponding standard amplitude values, and when the absolute value of the comparison result exceeds a preset threshold value, the metal foreign matter is judged to be present.
The standard amplitude values of the induction voltages of the four detection coils can be obtained by testing in advance; for example, in the case where no metallic foreign matter exists, the space of the power transmission system is reservedInitial induced voltage u existing in the initial magnetic field, four detection coil groups A, B, C and D A 、u B 、u C And u D The amplitude can be used as the standard amplitude of the induced voltage of the four detection coils; when a metal foreign body exists, the distribution and the size of a spatial magnetic field change, so that the induced voltages of the four detection coil groups A, B, C and D change, and the absolute value of the change value can be expressed as delta u A 、Δu B 、Δu C And Δ u D (ii) a When Δ u A 、Δu B 、Δu C And Δ u D When the threshold value is exceeded, it is considered that a metallic foreign matter is present. The preset threshold value is set empirically or experimentally. The larger the induced voltage variation, the higher the detection sensitivity for the metallic foreign matter. When the absolute value of the variation value of the induced voltage is greater than the preset threshold value, the value of the 4 paths of control signals output by the control unit 6 is constantly low level, the switching tube of the high-frequency inverter power supply is not conducted, the output voltage of the high-frequency inverter power supply is zero, and the system does not work, so that the safety of the system is ensured.
Still further, as shown in fig. 2, the transmitting unit of the wireless power transmission system includes a transmitting coil L t A transmitting coil connected in series with a capacitor C t And a transmitting part resonance branch 2, wherein the transmitting part resonance branch 2 is composed of a capacitor C d And an inductance L d Are connected in parallel;
two resonance points omega of the transmitting unit 1 And omega 2 Comprises the following steps:
A＝L d C d L t C t ，
B＝L d C d +L t C t +L d C t ，
make omega 1 ＝ω 0 ，ω 2 ＝nω 0 N is selected as an odd number; therefore, the transmitting unit of the wireless power transmission system comprises the fundamental wave energy transfer current and the high-order detection current.
In FIG. 2, the resistor R t To launch a sheetElement parasitic resistance u s Is a DC power supply, i t For emission of current, M tr Is the mutual inductance of the transceiver coil.
Frequency point ω of maximum impedance value of the resonance branch 2 of the transmitting part d Comprises the following steps:
ω d equal to the resonance point of the resonant branch 2 of the transmitting part. Omega can be selected d ＝3ω 0 。
For voltage signals of non-fundamental wave and nth harmonic wave, the filtering effect is good because the impedance of a transmitting loop is extremely large.
Still further, as shown in fig. 2, the receiving unit of the wireless power transmission system includes a receiving coil L r A receiving coil connected in series with a capacitor C r Receiving part resonance branch 3 and load resistor R L (ii) a The resonance branch 3 of the receiving part consists of a capacitor C b And an inductance L b Are connected in parallel;
according to the resonance point omega of the transmitting unit 2 To the capacitor C b And an inductance L b And (3) selecting:
according to omega 2 Determined capacitance C b And an inductance L b The n-th harmonic voltage of the higher frequency at the resonance point of the transmitting part resonance branch 2 has a very large impedance, and only the fundamental wave energy transfer current is ensured to exist in the receiving loop.
Then according to the resonance point omega of the transmitting unit 0 Determining a receive coil series capacitance C r Comprises the following steps:
the capacitance C determined according to the above r It can be ensured that the receiving loop has only one resonance point,i.e. omega 0 (ii) a Therefore, the receiving unit of the wireless power transmission system only contains fundamental wave energy transfer current, and metal foreign matter detection can be realized on the basis of not influencing power transmission of the power transmission system.
The electromagnetic field received by the receiving coil mainly comprises a fundamental component and an n-th harmonic component, and the induction voltage of the receiving coil mainly comprises the fundamental component and the n-th harmonic component; because the receiving loop only has one resonance point omega 0 The impedance is large for the nth harmonic voltage, so that the receiving loop current mainly comprises a fundamental component; the induced voltage generated by the receiving loop current on the detecting coil only contains fundamental wave component.
In FIG. 2, the resistor R r Is the receiving cell parasitic resistance. i all right angle r To receive the current.
Still further, as shown in fig. 4, the conversion unit 5 includes a voltage follower circuit, a filter circuit, a rectifier filter circuit, and a conditioning circuit, which sequentially process the induced voltage of the detection coil set; finally, the conditioning circuit outputs the adjusted amplitude of the induction voltage; the conversion unit 5 is configured to filter a fundamental component in the induced voltage of each detection coil group, and retain an nth harmonic component, so that the converted detection voltage value only includes the nth harmonic component;
the voltage follower circuit is used for isolating the induced voltage of the detection coil set from a post-stage circuit; current is not generated on the detection coil, a magnetic field is not generated, and the system work is not influenced;
the induced voltage is u 1 The output voltage of the voltage follower circuit is u 0 ；
The filter circuit is used for removing u 0 The fundamental component in the signal is kept from being attenuated by the n-th harmonic component to obtain a filtered voltage signal u 3 ；u 3 Containing only nth harmonic component, the current in the receiving unit not affecting u 3 So that the positions of the receiving coils do not align with u 3 Influence is caused, and even if the transmitting coil and the receiving coil are dislocated, the detection of the metal foreign bodies is not influenced;
the rectifying and filtering circuit is used for converting the voltage signal u 3 Obtaining a DC voltage signal U dc ；
The adjusting circuit is used for obtaining the adjusting amplitude of the induction voltage from the direct-current voltage signal; that is, the adjusting circuit is used to adjust U dc And obtaining an output signal which is used as a control signal and input into the DSP control unit.
The filter circuit comprises a capacitor C 1 Capacitor C 2 Resistance R 1 And a resistor R 2 And a resistor R 3 And a resistor R 4 And a voltage follower U 1 ；
Output end of voltage follower circuit and voltage follower U 1 Between the same-phase input ends of the two capacitors C are connected in series in sequence 1 And a capacitor C 2 Resistance R 1 Connected to a voltage follower U 1 Between the non-inverting input terminal and the power ground, a voltage follower U 1 Is connected with the power ground through a resistor R 3 Voltage follower U 1 Between the inverting input terminal and the output terminal of the capacitor 4 Voltage follower U 1 Is connected with the resistor R 2 One terminal of (1), resistance R 2 Is connected at the other end to a capacitor C 1 And a capacitor C 2 In the meantime.
As shown in FIG. 4, a capacitor C 1 And a capacitor C 2 Can be chosen as 194pF, resistance R 1 And a resistor R 2 And a resistance R 3 Can all be selected to be 1k omega, the resistance R 4 May be chosen to be 500 Ω; voltage follower U 1 Of inverting input terminal voltage u 2 。
Still further, as shown in fig. 4, the rectifying and filtering circuit includes a diode D 1 Capacitor C f And a resistance R 5 ，
Diode D 1 Anode of (2) connected to a voltage follower U 1 Output terminal of (2), diode D 1 A capacitor C is connected between the cathode of the anode and the power ground f Capacitor C f And a resistance R 5 And (4) connecting in parallel.
Capacitor C f Can be selected to be 1 mF, resistance R 5 And may be chosen to be 1k omega.
The rectifying and filtering circuit adopts a passive capacitor filter to convert a voltage signal u into a voltage signal u 3 Rectifying currentFiltering to obtain a DC voltage signal U dc In order to ensure a good filtering effect, the turn-off time of the diode in one period, namely the capacitor C f To the resistance R 5 The discharge time of (2) is long, and the time constant tau = R 5 C f Theoretically, the larger the capacitance and the resistance are, the better the filtering effect is, and the direct current voltage signal U is dc ≈U 3 ，U 3 Is u 3 Of the amplitude of (c).
Still further, as shown in FIG. 4, the conditioning circuit includes a diode D 2 And a resistor R 6 Resistance R 7 Resistance R 8 Resistance R 9 And voltage follower U 2 ，
Resistance R 6 Is connected to a diode D 1 Cathode and voltage follower U of 2 Between the non-inverting input terminals of (2), a diode D 2 Cathode of the capacitor is connected with a voltage follower U 2 Non-inverting input terminal of (2), diode D 2 Anode of (3) is connected to power ground, resistor R 7 And diode D 2 Parallel voltage follower U 2 Is connected with the power ground through a resistor R 8 Voltage follower U 2 Is connected with the ground of the power supply through a resistor R 9 (ii) a Voltage follower U 2 The output terminal of the voltage regulator outputs the regulated amplitude of the induced voltage.
As an example, the resistance R 6 And a resistor R 7 And a resistance R 8 Can be all selected to be 1k omega, and the voltage followers U 2 As output of the conversion unit 5.
Still further, n =9 is selected, and the output voltage u of the voltage follower circuit is filtered so as not to attenuate the 9 th harmonic component 0 The fundamental component of (1) is such that the voltage u is output by the voltage follower circuit 0 To voltage follower U 1 Output voltage signal u 3 The transfer function H(s) of (A) is:
wherein s is a virtual variable;
natural angular frequency ω of the filter circuit g Comprises the following steps:
voltage follower U 1 Closed loop gain A of F Comprises the following steps:
make R 1 ＝R 2 ，C 1 ＝C 2 Then the transfer function H(s) is simplified to:
for voltage signals of non-fundamental waves and 9 th harmonic waves, the impedance of a transmitting loop is extremely high, and the filtering effect is good;
as an example, R may be selected 1 ＝R 2 ＝R 3 ＝2R 4 ＝1kΩ，C 1 ＝C 2 ＝198pF。
As an example, the core controller of the control unit 6 is a DSP28335 control chip, and the DSP28335 control chip outputs a PWM signal to control the on/off of the switching tube of the high-frequency square wave power supply 1. When the metal foreign body exists, the switch tube in the power supply is constantly disconnected, and the system safety is ensured.
The high-frequency square wave power supply 1 can adopt a single-phase full-bridge inverter power supply and is provided with four switching tubes, so that the DSP is required to output 4 paths of PWM signals for controlling the on-off of the switching tubes.
When the control unit adopts a DSP controller, the input of the DSP controller needs to be less than 3.3V, so that the conditioning circuit is used for conditioning U dc The amplitude of the signal is adjusted, and the signal is input into a DSP controller as a control signal after meeting the requirement.
The effect of the conversion unit of the present embodiment on the fundamental wave voltage signal will be described with reference to fig. 5, in which the receiving circuits are connected in series as shown in fig. 2A 1k omega resistor is used as a main circuit, a signal generator outputs voltage signals with amplitude of 5V and frequency of 90.6kHz respectively, a conversion circuit 5 is connected in parallel at two ends of the 1k omega resistor, and a voltage source u of the conversion unit 5 1 The terminal voltage of the resistor of 1k omega is observed, and the AC detection voltage u filtered by the conversion unit 5 is observed 3 And rectified DC detection voltage U dc The conversion unit has excellent filtering effect on the fundamental voltage signal.
The effect of the conversion unit according to the present embodiment on the conversion of the nth harmonic voltage signal is described with reference to figure 6,
the double receiving circuits are connected with a resistor of 1k omega in series to serve as a main circuit, a signal generator outputs voltage signals with amplitude of 5V and frequency of 816kHz respectively, a conversion circuit is connected to two ends of the resistor in parallel, and alternating current detection voltage u filtered by the detection voltage conversion circuit is observed 3 And rectified DC detection voltage U dc The conversion unit almost completely retains the 9 th harmonic voltage signal;
the initial voltage waveforms of the detection coils a to D in the operation of the dual resonance structure system according to the present embodiment will be described with reference to fig. 7 and 8, and the effective value U of the initial induced voltages of the detection coils a to D when no metal foreign matter is present will be described A ～U D 4.70V, 3.75V, 5.26V and 4.11V respectively;
FIG. 9 is an induced voltage waveform diagram of a detection coil set when the metal foreign matter is a copper sheet, and the induced voltage waveform, the induced voltage effective value U, of the voltage waveforms of the detection coils A and C of the double-resonance structure system when the radius of the copper sheet is 10mm, the thickness of the copper sheet is 1mm and the coordinates of the copper sheet are (50, 80) are measured A 、U C The voltages induced by the detection coils a and C are respectively 17.4V and 5.1V, and the voltage induced by the detection coil a is increased and almost constant.
Placing the copper sheet in different coordinates of the first quadrant to obtain delta U at each coordinate 1 The parameter table (2) is as follows;
TABLE 1. DELTA.U 1 Parameter table
| x(mm)\ΔU 1 (V)\y(mm) | 0 | 20 | 40 | 60 | 80 | 100 |
| 0 | 0.42 | 7.88 | 11.85 | 12.74 | 12.20 | 4.59 |
| 20 | 3.32 | 6.26 | 6.63 | 10.80 | 12.38 | 4.05 |
| 40 | 9.27 | 5.76 | 7.20 | 14.60 | 1.36 | 1.55 |
| 60 | 9.06 | 9.16 | 12.33 | 7.60 | 11.02 | 1.59 |
| 80 | 22.47 | 17.71 | 21.36 | 9.62 | 8.43 | 2.75 |
| 100 | 4.44 | 4.34 | 6.80 | 1.97 | 3.71 | 1.76 |
Analyzing the data in table 1, it can be seen that the origin is still the detection blind area, and the coordinates, Δ U, other than the origin 1 The maximum is 22.47V, the minimum is 1.36V, and the detection system has higher detection sensitivity to the metal foreign matters.
Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that various dependent claims and the features described herein may be combined in ways different from those described in the original claims. It is also to be understood that features described in connection with individual embodiments may be used in other described embodiments.
Claims (10)
1. A metal foreign body detection system of a series-connection wireless power transmission system is characterized by comprising a high-frequency square wave power supply (1), a transmitting part resonance branch (2), a receiving part resonance branch (3), a detection unit (4), a conversion unit (5) and a control unit (6),
the transmitting part resonance branch circuit (2) is used for being connected in series between a capacitor and a transmitting coil of a transmitting unit of a wireless power transmission system, and the receiving part resonance branch circuit (3) is used for being connected in series between a load resistor and a receiving coil of a receiving unit of the wireless power transmission system;
the high-frequency square wave power supply (1) is used for providing voltage signals which can be decomposed into fundamental waves and odd harmonics for the transmitting unit of the wireless electric energy transmission system, so that the transmitting unit of the wireless electric energy transmission system comprises fundamental wave energy transfer current and high-order detection current; the receiving unit of the wireless electric energy transmission system comprises fundamental wave energy transfer current;
the detection unit (4) is used for detecting the coil set and generating induction voltage based on the transmitting coil; the detection coil set and the emission coil are coaxially arranged, and the lower surface of the detection coil set is closely adjacent to the upper surface of the emission coil;
the conversion unit (5) is used for sequentially filtering, rectifying and conditioning the induction voltage to obtain an adjusted amplitude of the induction voltage;
the control unit (6) is used for controlling the on-off and the frequency of the high-frequency square wave power supply (1), judging whether metal foreign bodies exist according to the standard amplitude of the induction voltage and the adjustment amplitude of the induction voltage, and switching off the high-frequency square wave power supply (1) when the metal foreign bodies exist.
2. The system for detecting metallic foreign objects in a series-type wireless power transmission system according to claim 1, wherein the detection coil sets of the detection unit (4) include an upper detection coil set and a lower detection coil set, the upper detection coil set and the lower detection coil set are closely connected, and the origin of coordinates coincide;
the upper detection coil set comprises a detection coil group C and a detection coil group D, the lower detection coil set comprises a detection coil group A and a detection coil group B, each detection coil group comprises two detection units, and the two detection units of the same detection coil group are connected in series in the reverse direction.
3. The system of claim 2, wherein the metal foreign object detection system of a series wireless power transmission system,
the standard amplitude of the induced voltage of the four detection coils, which can be obtained by the conversion unit (5), is obtained when no metal foreign matter exists in the wireless power transmission system; and the control unit (6) is adopted to compare the adjustment amplitude values of the induction voltages of the four detection coils obtained online by the conversion unit (5) with the corresponding standard amplitude values, and when the absolute value of the comparison result exceeds a preset threshold value, the metal foreign matter is judged to exist.
4. The system for detecting metallic foreign matter of a string-type wireless power transmission system according to claim 3,
the transmitting unit of the wireless power transmission system comprises a transmitting coil L t A transmitting coil connected in series with a capacitor C t And a transmitting part resonance branch (2), wherein the transmitting part resonance branch (2) is composed of a capacitor C d And an inductance L d Are connected in parallel;
two resonance points omega of the transmitting unit 1 And omega 2 Comprises the following steps:
A＝L d C d L t C t ，
B＝L d C d +L t C t +L d C t ，
make omega 1 ＝ω 0 ，ω 2 ＝nω 0 N is selected as an odd number; therefore, the transmitting unit of the wireless power transmission system comprises the fundamental wave energy transfer current and the high-order detection current.
5. The system for detecting metallic foreign matter of a string-type wireless power transmission system according to claim 4,
the receiving unit of the wireless power transmission system comprises a receiving coil L r A receiving coil connected in series with a capacitor C r A receiving part resonance branch (3) and a load resistor R L (ii) a The resonance branch (3) of the receiving part consists of a capacitor C b And an inductance L b Are connected in parallel;
according to the resonance point omega of the transmitting unit 2 To the capacitor C b And an inductance L b And (3) selecting:
then according to the resonance point omega of the transmitting unit 0 Determining the series capacitance C of the receiving coil r Comprises the following steps:
therefore, only the fundamental wave energy transfer current is contained in the receiving unit of the wireless power transmission system.
6. The system for detecting metallic foreign matter of a string-type wireless power transmission system according to claim 5,
the conversion unit (5) comprises a voltage following circuit, a filter circuit, a rectification filter circuit and a conditioning circuit which are used for sequentially processing the induction voltage of the detection coil set; finally, the conditioning circuit outputs the adjusted amplitude of the induction voltage;
the voltage follower circuit is used for isolating the induced voltage of the detection coil set from a post-stage circuit;
the induced voltage is u 1 Output of voltage follower circuitThe output voltage is u 0 ；
The filter circuit is used for removing u 0 The fundamental component in the signal is kept from being attenuated by the n-th harmonic component to obtain a filtered voltage signal u 3 ；
A rectifying-filtering circuit for converting the voltage signal u 3 Obtaining a direct current voltage signal;
the adjusting circuit is used for obtaining the adjusting amplitude of the induction voltage from the direct-current voltage signal;
the filter circuit comprises a capacitor C 1 Capacitor C 2 And a resistor R 1 And a resistor R 2 Resistance R 3 Resistance R 4 And a voltage follower U 1 ；
Output end of voltage follower circuit and voltage follower U 1 Between the same-phase input ends of the two capacitors C are connected in series in sequence 1 And a capacitor C 2 Resistance R 1 Connected to a voltage follower U 1 Between the non-inverting input terminal and the power ground, a voltage follower U 1 Is connected with the power ground through a resistor R 3 Voltage follower U 1 Between the inverting input terminal and the output terminal of the capacitor 4 Voltage follower U 1 Is connected with the resistor R 2 One terminal of (1), resistance R 2 Is connected to the capacitor C at the other end 1 And a capacitor C 2 In between.
7. The system for detecting metallic foreign matter of a string-type wireless power transmission system according to claim 6,
the rectifying and filtering circuit comprises a diode D 1 Capacitor C f And a resistance R 5 ，
Diode D 1 Anode of (2) connected to a voltage follower U 1 Output terminal of (2), diode D 1 Is connected with a capacitor C between the cathode of the capacitor C and the power ground f Capacitor C f And a resistance R 5 And (4) connecting in parallel.
8. The system of claim 7, wherein the modulator is configured to modulate the metal foreign object in the series wireless power transmission systemThe physical circuit comprises a diode D 2 Resistance R 6 Resistance R 7 Resistance R 8 Resistance R 9 And a voltage follower U 2 ，
Resistance R 6 Is connected to a diode D 1 Cathode and voltage follower U of 2 Between the non-inverting input terminals of (2), a diode D 2 Cathode of the capacitor is connected with a voltage follower U 2 Non-inverting input of, diode D 2 Anode of (3) is connected to power ground, resistor R 7 And diode D 2 Parallel voltage follower U 2 Is connected with the power ground through a resistor R 8 Voltage follower U 2 Is connected with the power ground through a resistor R 9 (ii) a Voltage follower U 2 The output terminal of the voltage regulator outputs the regulated amplitude of the induced voltage.
9. The system for detecting metallic foreign matter of a string-type wireless power transmission system according to claim 8,
n =9 is selected, and the voltage u is output from the voltage follower circuit so as not to attenuate the 9 th harmonic component 0 To voltage follower U 1 Output voltage signal u 3 The transfer function H(s) of (A) is:
in the formula, s is a virtual variable;
natural angular frequency ω of the filter circuit g Comprises the following steps:
voltage follower U 1 Closed loop gain A of F Comprises the following steps:
make R 1 ＝R 2 ，C 1 ＝C 2 Then the transfer function H(s) is simplified to:
10. the system for detecting metallic foreign matter of a string-type wireless power transmission system according to claim 9,
the core controller of the control unit (6) is a DSP28335 control chip, and the DSP28335 control chip outputs 4 paths of PWM signals to control the on-off of the switching tube of the high-frequency square wave power supply (1).
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