Planar double-winding coil-based foreign object detection system for wireless charging of electric vehicles

Abstract

The application discloses a kind of based on flat double-winding coil electric vehicle wireless charging foreign matter detection system, including flat double-winding detection coil group, high-frequency excitation signal source, resonance amplification circuit, high-pass filter, quadrature demodulator, ADC module, detection coil control switch and processor;Processor controls detection coil control switch based on time division multiplexing control method, changes the way that flat double-winding detection coil group is connected to resonance amplification circuit, realizes the switching between metal foreign matter and biological foreign matter detection mode;Resonance amplification circuit input end is connected to high-frequency excitation signal source, and output end is sequentially processed by high-pass filter and quadrature demodulator, and voltage amplitude and phase information sampling are realized by ADC module after it, and processor realizes the distinguishing detection of metal foreign matter and biological foreign matter according to the change of voltage amplitude and phase, and its effect is: foreign matter detection system and wireless charging system can work independently, and the effective detection of metal foreign matter and biological foreign matter can be realized.

Description

Technical Field

[0001] This invention relates to wireless charging technology, and more particularly to a foreign object detection system for wireless charging of electric vehicles based on a planar dual-winding coil. Background Technology

[0002] Currently, most electric vehicles use wired charging, which has problems such as easy wear and tear, inflexibility, large footprint, and low safety. In contrast, magnetic coupling wireless power transfer technology has the advantages of high safety, small size, and convenience and flexibility, and has received widespread attention from researchers at home and abroad in the field of electric vehicle charging.

[0003] When a wireless charging system for electric vehicles is in operation, there is a strong electromagnetic field between the transmitting coil and the receiving coil. As a result, organisms that enter this area may experience symptoms such as nausea, dizziness, limb weakness, and high blood pressure due to the influence of the high-intensity magnetic field. For metal that falls onto the transmitting coil, the high-frequency magnetic field will induce eddy currents inside it, causing the surface temperature of the metal to rise. If this continues for a long time, it may even cause a fire.

[0004] To ensure the safe and stable operation of wireless charging systems for electric vehicles and the health of living organisms, research on foreign object detection technology in wireless charging systems for electric vehicles is of great significance. Most existing foreign object detection technologies only target metallic foreign objects and cannot simultaneously meet the requirements for detecting non-metallic foreign objects. Summary of the Invention

[0005] In view of this, the present invention provides a foreign object detection system for wireless charging of electric vehicles based on a planar dual-winding coil. By using a time-division multiplexing method to control the connection between the detection coil and the circuit, and comparing the changes in the amplitude and phase of the output voltage, it enables the detection of both metallic and biological foreign objects in a single detection system.

[0006] To achieve the above objectives, the specific technical solution adopted by the present invention is as follows:

[0007] A wireless charging foreign object detection system for electric vehicles based on a planar dual-winding coil, the key components of which include a planar dual-winding detection coil group, a high-frequency excitation signal source, a resonant amplifier circuit, a high-pass filter, a quadrature demodulator, an ADC module, a detection coil control switch, and a processor; the processor controls the detection coil control switch based on a time-division multiplexing control method, thereby changing the way the planar dual-winding detection coil group is connected to the resonant amplifier circuit, realizing the switching between a metal foreign object detection mode and a biological foreign object detection mode; the input terminal of the resonant amplifier circuit is connected to the high-frequency excitation signal source, and the output terminal of the resonant amplifier circuit is processed sequentially by the high-pass filter and the quadrature demodulator, and then the ADC module acquires voltage amplitude and phase information; the processor distinguishes between metal and biological foreign objects based on changes in voltage amplitude and phase.

[0008] Optionally, the planar dual-winding detection coil group includes multiple detection channels arranged in a row. The number of detection channels is determined according to the size of the entire detection area and the coverage area of ​​a single detection channel. The detection coil in each detection channel adopts a dual-wire winding structure. Each wire is wound into multiple detection squares in a reverse series configuration. The wires of two adjacent detection squares in the same detection channel are wound in opposite directions.

[0009] Optionally, the resonant amplifier circuit includes an operational amplifier, a compensation topology switching switch, a compensation inductor, and a compensation capacitor. The detection coil control switch includes n detection channel switching switches and n detection mode switching switches, where n is the number of detection channels in the planar dual-winding detection coil group. The high-frequency excitation signal is connected to the inverting input terminal of the operational amplifier through a current-limiting resistor. The non-inverting input terminal of the operational amplifier is grounded. The output terminal of the operational amplifier is connected to the high-pass filter. The compensation inductor and the compensation capacitor are selectively switched between the output terminal and the inverting input terminal of the operational amplifier through the compensation topology switching switch. All n detection channels are arranged in parallel between the output terminal and the inverting input terminal of the operational amplifier. The two detection wires in the k-th detection channel are designated as C. ka and C kb The detection channel switching switch is S. 1k The detection mode switch is S. 2k Then the output terminals of the operational amplifier are connected in series with C. kb S 2k C ka and S 1k It is then connected to the inverting input of the operational amplifier, k = 1 to n.

[0010] Optionally, the two wires in each detection channel of the planar dual-winding detection coil group are equivalent to inductors when the detection mode switching switch is on, and the two wires in each detection channel of the planar dual-winding detection coil group are equivalent to planar capacitors when the detection mode switching switch is off.

[0011] Optionally, the processor controls the detection modes in a predetermined order. When entering the metal foreign object detection mode, the compensation capacitor is connected through the compensation topology switching switch, and the n detection mode switching switches are closed. The metal abnormality signals of each detection channel are scanned one by one by gradually closing and opening the n detection channel switching switches. When switching to the biological foreign object detection mode, the compensation inductor is connected through the compensation topology switching switch, and the n detection mode switching switches are opened. The biological abnormality signals of each detection channel are scanned one by one by gradually closing and opening the n detection channel switching switches.

[0012] Optionally, the planar dual-winding detection coil group is arranged above the wireless charging transmitting coil of the electric vehicle.

[0013] Optionally, the high-frequency excitation signal source includes a signal generator and a power amplifier.

[0014] Optionally, in the metal foreign object detection mode, if the processor detects that the voltage threshold is less than the preset threshold and the voltage phase is higher than the preset threshold, it is determined that a metal foreign object exists; in the biological foreign object detection model, if the processor detects that the voltage threshold is less than the preset threshold and the voltage phase is less than the preset threshold, it is determined that a biological foreign object exists.

[0015] The significant effects of this invention are:

[0016] 1) The foreign object detection system and the wireless charging system can use different operating frequencies. The interference signal of the transmitting coil magnetic field to the foreign object detection system is filtered out by a high-pass filter, which ensures that the two systems can work independently.

[0017] 2) Based on the time-division multiplexing control method, metallic and biological foreign objects in the wireless charging system of electric vehicles can be detected, and corresponding removal measures can be taken according to the type of foreign object to ensure the effectiveness of foreign object detection in the presence of multiple types of foreign objects. Attached Figure Description

[0018] Figure 1 This is a system topology diagram in a specific embodiment of the present invention;

[0019] Figure 2 This is a schematic diagram of the detection switch structure and working mode switching principle in an embodiment of the present invention;

[0020] Figure 3This is a timing diagram of the foreign object detection system in an embodiment of the present invention;

[0021] Figure 4 This is an equivalent circuit model diagram of the foreign object detection system in an embodiment of the present invention;

[0022] Figure 5 This is the equivalent circuit model of the two coils in the system when a metallic foreign object is present.

[0023] Figure 6 This is the equivalent circuit model of the two coils in the system when a biological foreign object is present.

[0024] Figure 7 It is a curve showing the relationship between the amplitude and phase of the detection voltage after the intrusion of a metallic foreign object and the rate of change of the quality factor and impedance.

[0025] Figure 8 It is a curve showing the relationship between the amplitude and phase of the detection voltage after the invasion of a biological foreign object and the rate of change of the quality factor and impedance. Detailed Implementation

[0026] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. The embodiments are given for illustrative purposes only and should not be construed as limiting the present invention. The accompanying drawings are for reference and illustration only and do not constitute a limitation on the scope of patent protection of the present invention, because many changes can be made to the present invention without departing from the spirit and scope of the present invention.

[0027] This embodiment provides a foreign object detection system for wireless charging of electric vehicles based on a planar dual-winding coil, which is used in conjunction with a wireless charging energy transfer system for electric vehicles, such as... Figure 1 As shown, the transmitting end of the electric vehicle wireless charging energy transmission system includes a DC power supply, an inverter, a primary resonant network, and a transmitting coil; the receiving end includes a receiving coil, a secondary resonant network, a rectifier circuit, and an on-board battery. In this embodiment, the electric vehicle wireless charging foreign object detection system includes a planar dual-winding detection coil group, a high-frequency excitation signal source, a resonant amplifier circuit, a high-pass filter, a quadrature demodulator, an ADC module, a detection coil control switch, and a processor; the high-frequency excitation signal source in this example includes a signal generator and a power amplifier.

[0028] In practical implementation, the planar dual-winding detection coil group is arranged above the transmitting coil and adopts a reverse series structure. Based on the size of the detection coil and the relative size of the transmitting coil, the planar dual-winding detection coil group contains n detection channels. The number of detection channels is determined by the size of the entire detection area and the coverage area of ​​a single detection channel, ensuring that the overall size of the detection coil group exceeds the coverage area of ​​the transmitting coil. Figure 1As can be seen, n detection channels are set up side by side, and the detection coil in each detection channel adopts a double wire winding structure. Each wire is wound into multiple detection squares in reverse series, and the wires of two adjacent detection squares in the same detection channel are wound in opposite directions.

[0029] In this example, the processor uses a DSP chip. The processor controls the control switch of the detection coil based on the time-division multiplexing control method, thereby changing the way the planar dual-winding detection coil group is connected to the resonant amplifier circuit, realizing the switching between the metal foreign object detection mode and the biological foreign object detection mode. The input terminal of the resonant amplifier circuit is connected to the high-frequency excitation signal source. The output terminal of the resonant amplifier circuit is processed by the high-pass filter and the quadrature demodulator in sequence, and then the voltage amplitude information and phase information are acquired by the ADC module. The processor realizes the differentiation and detection of metal foreign objects and biological foreign objects based on the changes in voltage amplitude and phase.

[0030] In specific implementation, the resonant amplifier circuit includes an operational amplifier, a compensation topology switching switch, a compensation inductor, and a compensation capacitor. The detection coil control switch includes n detection channel switching switches and n detection mode switching switches, where n is the number of detection channels in the planar dual-winding detection coil group. The high-frequency excitation signal is connected to the inverting input terminal of the operational amplifier through a current-limiting resistor. The non-inverting input terminal of the operational amplifier is grounded, and the output terminal of the operational amplifier is connected to the high-pass filter. The compensation inductor and the compensation capacitor are selectively switched between the output terminal and the inverting input terminal of the operational amplifier through the compensation topology switching switch. All n detection channels are arranged in parallel between the output terminal and the inverting input terminal of the operational amplifier. The two detection wires in the k-th detection channel are designated as C. ka and C kb The detection channel switching switch is S. 1k The detection mode switch is S. 2k Then the output terminals of the operational amplifier are connected in series with C. kb S 2k C ka and S 1k It is then connected to the inverting input of the operational amplifier, k = 1 to n.

[0031] Combination Figure 2 It can be seen that the DSP controls two detection coil switch groups, Switch 1 (n detection channel switching switch) and Switch 2 (n detection mode switching switch), as well as the compensation topology switching switch S. rThe system is controlled to sequentially and cyclically scan and detect n detection channels, switching between metal foreign object detection and biological foreign object detection. Switch 1 connects different detection channels to subsequent detection circuits by opening and closing the switch, while Switch 2 changes the connection state of the detection wires, thus switching between metal and biological foreign object detection modes. When the switch is closed, the two wires in the detection channel are connected in the same direction, equivalent to an inductor, and the system detects metal foreign objects. If a metal foreign object intrudes, it will affect the magnetic field distribution. When the switch is open, the two wires in the detection channel are disconnected, equivalent to a planar capacitor, and the system detects biological foreign objects. If a biological foreign object intrudes, the electric field lines passing through its body will affect the capacitance between the two wires.

[0032] Taking one detection channel n of a planar dual-winding coil as an example, it contains two independent wires C. na C nb Each detection channel contains 4 terminals A n1 A n2 B n1 B n2 The foreign object detection mode is switched by changing the connection method between the terminals. When the foreign object detection system is in metal foreign object detection mode, terminal A in detection channel n... n2 B n1 Connected, at this time wire C na C nb When a current of equal magnitude and in the same direction flows through a foreign object, the presence of a metallic foreign object will cause a change in the equivalent self-inductance of the detection channel. When the foreign object detection system is in biological foreign object detection mode, terminal A in detection channel n... n2 B n1 Disconnect, at this time wire C na C nb It is equivalent to two independent electrodes. When a voltage is applied between them, the detection channel can be regarded as a planar capacitor. When a biological foreign object is present, the equivalent capacitance of the detection channel changes.

[0033] Therefore, the processor can control the detection modes in a predetermined order. When entering the metal foreign object detection mode, the compensation capacitor is connected through the compensation topology switching switch, and the n detection mode switching switches are closed. The metal abnormality signals of each detection channel are scanned one by one by gradually closing and opening the n detection channel switching switches. When switching to the biological foreign object detection mode, the compensation inductor is connected through the compensation topology switching switch, and the n detection mode switching switches are opened. The biological abnormality signals of each detection channel are scanned one by one by gradually closing and opening the n detection channel switching switches.

[0034] The foreign object detection system can first be set to metal foreign object detection mode. Switch 1 can then perform a cyclic scan of n detection channels. After one scan cycle, Switch 2 and Switch S can be controlled. r Switching between detection modes and compensation topology puts the foreign object detection system into biological foreign object detection mode, and also performs cyclic scanning detection on n detection channels.

[0035] Taking one detection cycle of the system as an example, through Figure 3 As can be seen, when the foreign object detection system is working, firstly, all switches in Switch 2 are closed, putting the foreign object detection system into metal foreign object detection mode. This is achieved by controlling switch S in Switch 1. 11 S 12 ,…,S 1n The system sequentially closes and opens, cyclically scanning n detection channels. Then, all switches in Switch 2 are turned on, putting the foreign object detection system into biological foreign object detection mode. Similarly, Switch 1 cyclically scans n detection channels. If the detection time for each channel is T... d Then the time required for one detection cycle of the foreign object detection system is T = 2nT d In addition, the resonant compensation network switching switch S r The action time is the same as the Switch 2. When performing metal foreign object detection, S... r Connect a compensation capacitor; when performing biological foreign object detection, S r Connect a compensation inductor.

[0036] Figure 4 Here is the equivalent circuit model of the foreign object detection system, where: E dc U1 is the DC input power supply, and U2 is the AC input voltage on the transmitting side. k To detect the voltage on the coil, I1, I2, and I3 represent the currents on the transmitting coil, the detection coil, and the metallic foreign object, respectively; L P R P For the self-inductance and internal resistance of the transmitting coil, C r C is the inter-turn capacitance of the transmitting coil. f L f C P Constructing a transmitter-side compensation circuit, L S R S For the self-inductance and internal resistance of the receiving coil, C S Constructing a receiving-side compensation circuit, R LOD For electric vehicle load; R M and L M R represents the equivalent resistance and equivalent inductance of the metallic foreign object. d and L d To detect the internal resistance and self-inductance of the coil, Cd To compensate for the capacitor, M PM M Md M Pd These represent the mutual inductance between each pair of the metallic foreign object, the detection coil, and the transmitting coil; the biological foreign object is represented by a three-element impedance model, C m R is the cell membrane capacitance. i R is the intracellular fluid resistance. e For extracellular fluid resistance, C ab and R ab To detect the capacitance between coils Cka and Ckb in channel k, as well as the coil's internal resistance and L... D To compensate for inductance, C bL C aL C bp C ap To detect the mutual capacitance between the detection coils Cka and Ckb and the biological foreign object and the transmitting coil.

[0037] Figure 5 The equivalent circuit model of the detection system with two coils in the presence of a metallic foreign object is given. By incorporating the equivalent circuit parameters of the metallic foreign object into the transmitting and detecting coil circuits, the three-coil equivalent model can be simplified to a two-coil equivalent model, where L′ P and R′ P Let L′ be the equivalent resistance and inductance of the transmitting coil in the two-coil model. d and R′ d In the two-coil model, the equivalent resistance and inductance of the detection coil are given, and the mutual inductance between the transmitting coil and the detection coil becomes M′. Pd The coefficients of change of the equivalent resistance and equivalent inductance of the detection coil after the intrusion of a metallic foreign object are defined as α. MOD and β MOD Its expression is shown in equations (1) and (2).

[0038]

[0039]

[0040] Because metallic foreign objects have high electrical conductivity, their equivalent internal resistance R M The relatively small internal resistance R of the detection coil, along with its numerous turns and small wire diameter, results in a lower coil resistance. d Much larger than R M Therefore, the coefficient of change of the equivalent internal resistance α of the detection coil after the intrusion of a metallic foreign object is... MOD If the value is close to 1, then the expression for the rate of impedance change γ of the detection coil before and after the intrusion of the metallic foreign object is:

[0041]

[0042] Among them, the quality factor Q of the detection coild =ωL d / R d When the frequency of the excitation source of the detection coil is high enough to make Q d When >>1, formula (3) can be simplified to:

[0043]

[0044] Under conditions without metallic foreign objects, the detection system is in a resonant state, and the output voltage of the resonant amplifier circuit is as shown in formula (5). When a metallic foreign object enters, the output voltage is as shown in formula (6), where the parallel resistor of the detection coil is... Parallel inductor to detection coil Figure 7 This is a curve showing the relationship between the amplitude and phase of the detection voltage after the intrusion of a metallic foreign object and the rate of change of the quality factor and impedance.

[0045]

[0046]

[0047] Figure 6 The equivalent circuit model of the detection system in the presence of biological foreign objects is given. When there are no biological foreign objects in the wireless charging system for electric vehicles, the equivalent admittance of the detection coil is Y. dN When a biological foreign object invades, due to its own impedance and the coupling capacitance between it and the detection coil, the equivalent admittance of the detection coil becomes Y. d Formula (7) is the expression for the equivalent admittance of the detection coil before and after the entry of a biological foreign object.

[0048]

[0049] in,

[0050]

[0051] The coefficients of change of the equivalent internal resistance and equivalent capacitance of the detection coil after the invasion of a biological foreign object are defined as α. LOD and β LOD Its expression is shown in formula (9) and formula (10).

[0052]

[0053]

[0054] Since the electrical resistance of living organisms can range from hundreds to thousands of ohms, the equivalent resistance R of a living organism is... L >>1, which makes the coefficient of change of the equivalent internal resistance α of the detection coil after the intrusion of biological foreign objects... LODSince the value is close to 1, the effect of the biological foreign body intrusion on the equivalent internal resistance of the detection coil can be ignored. Therefore, the rate of change of impedance λ of the detection coil before and after the biological foreign body intrusion is:

[0055]

[0056] Among them, the quality factor Q of the detection coil D =ωR ab C ab When the frequency of the excitation source of the detection coil is high enough to make Q D When >>1, formula (11) can be simplified to:

[0057]

[0058] Similarly, the output voltage of the resonant amplifier circuit after the invasion of a biological foreign object is shown in formula (12). Figure 8 The curves show the relationship between the amplitude and phase of the detection voltage after biological foreign body invasion and the rate of change of quality factor and impedance.

[0059] Depend on Figure 7 and Figure 8 It can be seen that the intrusion of both biological and metallic foreign objects alters the amplitude and phase of the output voltage of the resonant amplifier circuit. Both reduce the voltage amplitude, while metallic foreign objects increase the voltage phase, and biological foreign objects decrease the voltage phase.

[0060] Therefore, in the metal foreign object detection mode, if the processor detects that the voltage threshold is less than the preset threshold and the voltage phase is higher than the preset threshold, it can be identified as the presence of a metal foreign object; in the biological foreign object detection model, if the processor detects that the voltage threshold is less than the preset threshold and the voltage phase is less than the preset threshold, it can be identified as the presence of a biological foreign object.

[0061] In summary, the present invention provides a foreign object detection system for electric vehicle wireless charging based on a planar dual-winding coil. By controlling the detection coil control switch via a DSP, different detection channels and modes are allocated to different time segments, allowing for different removal methods based on the type of foreign object detected. The foreign object detection system and the wireless charging system can operate at different frequencies. A high-pass filter removes interference signals from the transmitting coil's magnetic field, ensuring independent operation of the two systems. This system effectively detects both metallic and biological foreign objects located within the electric vehicle wireless charging system.

[0062] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A foreign object detection system for wireless charging of an electric vehicle based on a planar double-winding coil, characterized in that, The metal foreign body detection device comprises a planar double-winding detection coil group, a high-frequency excitation signal source, a resonance amplification circuit, a high-pass filter, a quadrature demodulator, an ADC module, a detection coil control switch and a processor. The resonance amplification circuit input end is connected to the high-frequency excitation signal source, and the resonance amplification circuit output end is sequentially processed through the high-pass filter and the quadrature demodulator, and then the voltage amplitude information and phase information are collected by the ADC module. The planar double-winding detection coil group comprises a plurality of detection channels arranged in an array, and the number of detection channels is determined according to the size of the entire detection area and the coverage area of a single detection channel. The resonance amplification circuit comprises an operational amplifier, a compensation topology switching switch, a compensation inductor and a compensation capacitor, the detection coil control switch comprises n detection channel switching switches and n detection mode switching switches, n is the number of detection channels in the planar double-winding detection coil group, the high-frequency excitation signal source is connected to the inverting input end of the operational amplifier through a current-limiting resistor, the non-inverting input end of the operational amplifier is grounded, the output end of the operational amplifier is connected to the high-pass filter, and the compensation inductor and the compensation capacitor are selectively switched between the output end and the inverting input end of the operational amplifier through the compensation topology switching switch; n detection channels are arranged in parallel between the output end and the inverting input end of the operational amplifier, two detection wires in the kth detection channel are set as C ka and C kb , the detection channel switching switch is S 1k , the detection mode switching switch is S 2k , the output end of the operational amplifier is connected to the inverting input end of the operational amplifier after being sequentially connected to C kb , S 2k , C ka and S 1k , and k=1~n.

2. The planar double-winding coil based electric vehicle wireless charging foreign object detection system of claim 1, wherein, The two wires in each detection channel of the planar double-winding detection coil group are equivalent to inductance elements in the detection mode switching switch conduction state, and are equivalent to planar capacitors in the detection mode switching switch open state.

3. The planar double-winding coil based electric vehicle wireless charging foreign object detection system of claim 2, wherein, The processor controls the detection mode in a predetermined order. When the metal foreign body detection mode is entered, the compensation capacitor is connected through the compensation topology switching switch, the n detection mode switching switches are closed, and the metal abnormal signal of each detection channel is scanned one by one by gradually closing and opening the n detection channel switching switches.

4. The planar double-winding coil based foreign object detection system for electric vehicle wireless charging of any of claims 1-3, wherein, When the biological foreign body detection mode is switched, the compensation inductor is connected through the compensation topology switching switch, the n detection mode switching switches are opened, and the biological abnormal signal of each detection channel is scanned one by one by gradually closing and opening the n detection channel switching switches.

5. The planar double-winding coil based electric vehicle wireless charging foreign object detection system of claim 4, wherein, The planar double-winding detection coil group is arranged above the wireless charging transmitting coil of the electric vehicle.

6. The planar double-winding coil based electric vehicle wireless charging foreign object detection system of claim 4, wherein, The high-frequency excitation signal source comprises a signal generator and a power amplifier. In the metal foreign body detection mode, if the processor detects that the voltage threshold is less than the preset threshold and the voltage phase is higher than the preset threshold, it is determined that there is a metal foreign body. In the biological foreign body detection model, if the processor detects that the voltage threshold is less than the preset threshold and the voltage phase is less than the preset threshold, it is determined that there is a biological foreign body.

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