CN117220425A - Foreign matter detection module for wireless charging and self-oscillation circuit - Google Patents
Foreign matter detection module for wireless charging and self-oscillation circuit Download PDFInfo
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- CN117220425A CN117220425A CN202311189077.3A CN202311189077A CN117220425A CN 117220425 A CN117220425 A CN 117220425A CN 202311189077 A CN202311189077 A CN 202311189077A CN 117220425 A CN117220425 A CN 117220425A
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Abstract
The invention discloses a foreign matter detection module and a self-oscillation circuit for wireless charging, which belong to the technical field of wireless power transmission, wherein the module comprises an exciting coil N p Feedback coil N s And a foreign matter detection coil L d The exciting coil N p And the feedback coil N s First coil layers arranged on the bearing plate in parallel, and foreign matter detection coils L d A second coil layer arranged on the bearing plate and respectively connected with the exciting coil N p And the feedback coil N s And (3) inductive coupling. The effect is that: when the self-oscillation circuit is matched with a corresponding self-oscillation circuit to work, a specific resonant frequency is not required to be set, and the detection precision is prevented from being reduced due to the deviation of the harmonic capacitance in the traditional impedance method. In addition, each coil does not need to be matched with resonance,only a vibration starting capacitor is needed, so that the workload of the arrayed coils is reduced.
Description
Technical Field
The invention belongs to the technical field of wireless power transmission, and particularly relates to a foreign matter detection module and a self-oscillation circuit for wireless charging.
Background
The wireless power transmission technology (wireless power transfer, WPT) is a technology for comprehensively applying related theories and technologies such as power electronics and automatic control, and the like, and realizing the transmission of electric energy between a power grid (or a battery) and electric equipment through a carrier (such as an electric field, a magnetic field, microwaves and laser) in a loose coupling non-electric contact mode. Compared with the traditional electric contact type electric energy access technology, the wireless electric energy transmission technology has the advantages of higher reliability and safety, smaller occupied space, flexible use mode, difficult interference by external environment factors, strong interaction with a power grid, capability of being applied under certain extreme environments and special conditions and the like, and therefore, the wireless electric energy transmission technology has wider development and application in the fields of consumer electronics, medical care, electric automobiles and the like.
The magnetic field coupling type wireless power transmission generates a high-frequency alternating magnetic field through high-frequency alternating current in a transmitting end coil, and the high-frequency alternating magnetic field is used as a carrier for power transmission. However, when metallic foreign matters (such as coins, keys and paperclips) are present in or around the transmitting coil of the MC-WPT system, the distribution of the high-frequency alternating magnetic field of the MC-WPT system will be changed, resulting in the decrease of the transmission efficiency of the system, and the metallic foreign matters may have potential safety hazards due to eddy current effect and hysteresis loss heat generation. If a living body enters a high-frequency alternating magnetic field for a long time, health is affected. In summary, a technique for detecting foreign matters is indispensable.
The existing foreign matter detection scheme mainly comprises three detection methods based on MCR-WPT system parameters, traditional sensors and detection coils. The detection method based on the MCR-WPT system parameters utilizes the influence of the foreign matters on the related parameters of the MCR-WPT system to detect the foreign matters, has lower cost and does not need an additional detection mechanism, but the detection progress is influenced by the power level of the MCR-WPT system, and is not suitable for high-power occasions; the detection method based on the traditional sensor detects the foreign matters by placing the sensor in the system, such as a temperature sensor, a visual camera, an ultrasonic sensor and the like, has large detection coverage area, is not influenced by the power level of the MCR-WPT system, but has high cost, low integration level and high requirement on the sensor; the foreign matter detection method based on the detection coil realizes the identification of the foreign matter by monitoring the related physical quantity on the detection coil, has higher detection precision compared with a mode based on system parameters, and is suitable for various power level scenes.
Disclosure of Invention
Aiming at the defects of the prior art, the invention firstly provides a foreign matter detection module for wireless charging, which has simple structure and convenient design, can quickly convert a foreign matter signal into an electric signal by matching with a corresponding self-excited oscillation circuit, and is convenient for realizing foreign matter detection.
In order to achieve the above purpose, the technical scheme provided by the invention is as follows:
a foreign matter detection module for wireless charging, its key lies in: comprising an exciting coil N p Feedback coil N s And a foreign matter detection coil L d The exciting coil N p And the feedback coil N s First coil layers arranged on the bearing plate in parallel, and foreign matter detection coils L d A second coil layer arranged on the bearing plate and respectively connected with the exciting coil N p And the feedback coil N s And (3) inductive coupling.
Alternatively, the foreign matter detection coil L d At least one part is covered on the exciting coil N p And the feedback coil N s Directly above (2).
Optionally, the exciting coil N p The feedback coil N s And the foreign matter detection coil L d Are all planar coils.
Optionally, the carrier plate is a PCB plate.
Optionally, the exciting coil N p And the feedback coil N s Is detected by the foreign matter detection coil L d And (5) full coverage.
Optionally, the exciting coil N p The feedback coil N s And the foreign matter detection coil L d Is connected to the self-oscillation circuit.
Based on the foreign matter detection module, the invention also provides a self-oscillation circuit, which is characterized in that: exciting coil N p And resistance R 5 Capacitance C 2 And diode VD 2 A first resonant circuit is formed, and the positive electrode of the power supply is connected with the switch tube VT through the first resonant circuit 1 The power supply positive electrode also passes through the resistor R 1 Connected to the switching tube VT 1 Base of (2), switching tube VT 1 Emitter pass resistance R 3 Connect with the negative pole of the power supply and pass through the resistor R 6 And diode VD 3 Feedback to the switching tube VT 1 A base of (2); switching tube VT 1 The base of (2) is also connected with a switch tube VT 2 Collector connection of (C) and switching tube VT 1 The emitter of (2) also passes through a resistor R 4 And a switching tube VT 2 Is connected with the base electrode of the switch tube VT 2 The emitter of the (C) is connected with the negative electrode of the power supply;
foreign matter detection coilL d And resistance R 2 Capacitance C dc Forming a second resonant circuit connected to the switching tube VT 1 Between the base of the (C) and the negative electrode of the power supply, in the foreign matter detection coil L d Is also connected with a diode VD in forward direction in turn between two ends 1 And capacitor C 4 Capacitance C 4 The end voltage of (2) is fed back to the switch tube VT through the optocoupler switch 2 A base of (2);
feedback coil N s And diode VD 3 Resistance R 7 Capacitance C 5 And a third resonance circuit formed from the foreign matter detection coil L d Obtain induced voltage and pass through sampling resistor R 8 And the feedback is carried out to the optical coupler switch to realize the on-off control of the optical coupler switch.
Optionally, a filter capacitor C is connected between the positive electrode and the negative electrode 1 。
Alternatively, capacitor C 2 Reverse series diode VD 2 And then with the exciting coil N p Form a parallel resonant circuit, a resistor R 5 Connected in parallel with capacitor C 2 And (3) upper part.
Optionally, a feedback coil N s Positive string diode VD 3 Rear and capacitance C 5 Form a parallel resonant circuit, a resistor R 7 Connected in parallel with capacitor C 5 And (3) upper part.
The foreign matter detection module and self-oscillation circuit for wireless charging provided by the invention comprise the following components
The beneficial effects are that:
compared with the traditional coil impedance type detection mode, the invention does not need to set specific resonant frequency, and the self-oscillation circuit finally tends to the resonant frequency of the foreign matter detection coil and the corresponding resonant capacitor according to the foreign matter detection coil, so that the detection precision can be prevented from being reduced due to the deviation of the resonant capacitor in the traditional impedance method. In addition, in the conventional impedance method, it is necessary to perform self-inductance measurement for each of the detection coils for the arrayed detection coils, and then select the resistance value one by one to configure the resonance frequency to coincide with the excitation source frequency. By adopting the technology provided by the invention, each coil is not required to be matched with resonance, only a vibration starting capacitor is needed, and the workload of the arrayed coils is reduced.
Drawings
FIG. 1 is a diagram showing a distribution relation of coils of a foreign matter detection module for wireless charging according to the present invention;
fig. 2 is a schematic diagram of a self-oscillating circuit provided in an embodiment of the invention.
Detailed Description
Embodiments of the present invention are described in further detail below with reference to the accompanying drawings and examples. The following examples are illustrative of the invention but are not intended to limit the scope of the invention.
As shown in fig. 1, the present embodiment provides a foreign matter detection module for wireless charging, including an exciting coil N p Feedback coil N s And a foreign matter detection coil L d The exciting coil N is realized by layering printing on the PCB p And a feedback coil N s First coil layer arranged on PCB in parallel, foreign matter detection coil L d A second coil layer arranged on the bearing plate and respectively connected with the exciting coil N p And a feedback coil N s The inductive coupling, the PCB board can be a plane board or an arc panel, and the excitation coil N in this example can be designed according to the specific application scene p Feedback coil N s And a foreign matter detection coil L d Are all plane coils, and the exciting coil N p And a feedback coil N s Foreign matter detection coil L d The full coverage may of course also be made partly so long as it is ensured that the coupling relation with each other is able to meet the level of signal pick-up.
In particular implementation, the coil N is excited p Feedback coil N s And a foreign matter detection coil L d Is connected to the self-oscillation circuit. In connection with a self-oscillating circuit provided in fig. 2, it can be seen that:
exciting coil N p And resistance R 5 Capacitance C 2 And diode VD 2 A first resonant circuit is formed, and the positive electrode of the power supply is connected with the switch tube VT through the first resonant circuit 1 The power supply positive electrode also passes through the resistor R 1 Connected to the switching tube VT 1 Base of (2), switching tube VT 1 Emitter of (c) through resistance R 3 Connect with the negative pole of the power supply and pass through the resistor R 6 And diode VD 3 Feedback to the switching tube VT 1 A base of (2); switching tube VT 1 The base of (2) is also connected with a switch tube VT 2 Collector connection of (C) and switching tube VT 1 The emitter of (2) also passes through a resistor R 4 And a switching tube VT 2 Is connected with the base electrode of the switch tube VT 2 The emitter of the (C) is connected with the negative electrode of the power supply;
foreign matter detection coil L d And resistance R 2 Capacitance C dc Forming a second resonant circuit connected to the switching tube VT 1 Between the base of the (C) and the negative electrode of the power supply, in the foreign matter detection coil L d Is also connected with a diode VD in forward direction in turn between two ends 1 And capacitor C 4 Capacitance C 4 The end voltage of (2) is fed back to the switch tube VT through the optocoupler switch 2 A base of (2);
feedback coil N s And diode VD 3 Resistance R 7 Capacitance C 5 And a third resonance circuit formed from the foreign matter detection coil L d Obtain induced voltage and pass through sampling resistor R 8 And the feedback is carried out to the optical coupler switch to realize the on-off control of the optical coupler switch.
In specific implementation, a filter capacitor C is connected between the positive electrode and the negative electrode of the power supply 1 In the first resonant circuit: capacitor C 2 Reverse series diode VD 2 And then with the exciting coil N p Form a parallel resonant circuit, a resistor R 5 Connected in parallel with capacitor C 2 In the third resonant circuit, above: feedback coil N s Positive string diode VD 3 Rear and capacitance C 5 Form a parallel resonant circuit, a resistor R 7 Connected in parallel with capacitor C 5 And (3) upper part.
The self-oscillation circuit provided by the embodiment is equivalent to a self-oscillation switching power supply circuit, fully utilizes the desaturation characteristic of the triode, and mainly comprises three working processes:
1. the switching tube conducting process comprises the following steps: after the circuit is turned on, the voltage U is input i Through resistance R 1 Is a switching tube VT 1 Providing base current, VT 1 Conducting, collector current path is U 1 Positive electrode-sequentially passing through exciting coil N p 1, 2 ends of (2), switch tube VT 1 Resistance R 3 →U 1 A negative electrode; foreign matter detection coil L d And exciting coil N p Inductive coupling is performed on the foreign matter detection coil L d Generating an induced voltage with positive 3 pins through C dc 、R 2 Is a switching tube VT 1 The base electrode provides feedback current, and the current path is a foreign matter detection coil L d 3 feet C of (2) dc →R 2 Switching tube VT 1 Base → R3 → foreign matter detection coil L d 4 pins of (2), positive feedback current causes the switching tube VT 1 Accelerating conduction and entering into saturation state soon.
2. Switching tube cut-off process: switching tube VT 1 After saturated conduction, exciting coil N p The current in (a) increases linearly, R 3 Increased pressure drop over and VT is reached 2 VT at the on-voltage of the base 2 Start to conduct with VT of 1 The base current is shunted so that VT 1 And exiting saturation and entering an amplified state. VT (VT) 1 Base reduction, collector and excitation coil N p Medium current is reduced in the exciting coil N p A foreign matter detection coil L for generating reverse induced voltage d The induced voltage in (C) is reversed dc Changing from charge state to discharge state to make VT 1 The current of the base electrode is further reduced to form strong negative feedback so as to ensure VT 1 And rapidly cut off. C (C) dc Discharge path: c (C) dc Right end-foreign matter detection coil L d 3 feet of (2) →foreign matter detection coil L d 4 pins of (2), input ground, R3, R6, VD3, R2 and C dc And the left end.
Thirdly,: and (3) a voltage stabilizing process: when the output voltage increases, the feedback coil N s From foreign matter detection coil L d The induced voltage increases, so that the optical coupler switch IC 3 Current increase, VT 2 Base current increases, VT 2 For VT (VT) 1 The base electrode shunt effect is increased and the VT is accelerated 1 To shorten the on-timeThe output voltage drops, maintaining the voltage stable. When the output voltage is reduced, the optocoupler switching current is reduced, the shunt effect is reduced, the conduction time of the switching tube is increased, and the output voltage tends to be stable.
As can be seen from the above analysis, the capacitance C dc The inductance element passing through the charge and discharge is only L d Thus C dc And L d In fact, it plays a role in frequency selection, determining the frequency of oscillation. While the presence of metallic foreign matter changes L d The self-inductance also changes the frequency of self-oscillation. N (N) p The practical function is to control the switching tube in L d The induced voltage is generated in the L process due to the reduction of the current flowing in the switching tube during the cut-off process d Inducing a reverse voltage to N S The amplitude of the output voltage is regulated by the induced voltage, N p And N s The influence of the variation of (c) on the self-excitation frequency is small. In conclusion, the self-inductance of the foreign matter detection coil can influence the self-oscillation frequency, so that the self-inductance of the foreign matter detection coil can be used as a basis for detecting metal foreign matters, and the foreign matter detection can be conveniently and rapidly realized.
The foregoing is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art, who is within the scope of the present invention, should make equivalent substitutions or modifications according to the technical scheme of the present invention and the inventive concept thereof, and should be covered by the scope of the present invention.
Claims (10)
1. A foreign matter detection module for wireless charging, its characterized in that: comprising an exciting coil N p Feedback coil N s And a foreign matter detection coil L d The exciting coil N p And the feedback coil N s First coil layers arranged on the bearing plate in parallel, and foreign matter detection coils L d A second coil layer arranged on the bearing plate and respectively connected with the exciting coil N p And the feedback coil N s And (3) inductive coupling.
2. According to claim 1The foreign matter detection module for wireless charging is characterized in that: the foreign matter detection coil L d At least one part is covered on the exciting coil N p And the feedback coil N s Directly above (2).
3. The foreign matter detection module for wireless charging according to claim 1 or 2, characterized in that: the exciting coil N p The feedback coil N s And the foreign matter detection coil L d Are all planar coils.
4. The foreign matter detection module for wireless charging of claim 3, wherein: the bearing plate is a PCB.
5. The foreign matter detection module for wireless charging of claim 2, wherein: the exciting coil N p And the feedback coil N s Is detected by the foreign matter detection coil L d And (5) full coverage.
6. The foreign matter detection module for wireless charging of claim 1 or 2 or 4 or 5, wherein: the exciting coil N p The feedback coil N s And the foreign matter detection coil L d Is connected to the self-oscillation circuit.
7. Self-oscillation circuit for a foreign object detection module according to any one of claims 1 to 6, characterized in that: exciting coil N p And resistance R 5 Capacitance C 2 And diode VD 2 A first resonant circuit is formed, and the positive electrode of the power supply is connected with the switch tube VT through the first resonant circuit 1 The power supply positive electrode also passes through the resistor R 1 Connected to the switching tube VT 1 Base of (2), switching tube VT 1 Emitter pass resistance R 3 Connect with the negative pole of the power supply and pass through the resistor R 6 And diode VD 3 Feedback to the switching tube VT 1 A base of (2); switching tube VT 1 The base of (2) is also connected with a switch tube VT 2 Collector connection of (C) and switching tube VT 1 The emitter of (2) also passes through a resistor R 4 And a switching tube VT 2 Is connected with the base electrode of the switch tube VT 2 The emitter of the (C) is connected with the negative electrode of the power supply;
foreign matter detection coil L d And resistance R 2 Capacitance C dc Forming a second resonant circuit connected to the switching tube VT 1 Between the base of the (C) and the negative electrode of the power supply, in the foreign matter detection coil L d Is also connected with a diode VD in forward direction in turn between two ends 1 And capacitor C 4 Capacitance C 4 The end voltage of (2) is fed back to the switch tube VT through the optocoupler switch 2 A base of (2);
feedback coil N s And diode VD 3 Resistance R 7 Capacitance C 5 And a third resonance circuit formed from the foreign matter detection coil L d Obtain induced voltage and pass through sampling resistor R 8 And the feedback is carried out to the optical coupler switch to realize the on-off control of the optical coupler switch.
8. A self-oscillation circuit according to claim 7, wherein: a filter capacitor C is connected between the positive electrode of the power supply and the negative electrode of the power supply 1 。
9. A self-oscillation circuit according to claim 7 or 8, wherein: in the first resonant circuit: capacitor C 2 Reverse series diode VD 2 And then with the exciting coil N p Form a parallel resonant circuit, a resistor R 5 Connected in parallel with capacitor C 2 And (3) upper part.
10. A self-oscillation circuit according to claim 7 or 8, wherein: in the third resonant circuit: feedback coil N s Positive string diode VD 3 Rear and capacitance C 5 Form a parallel resonant circuit, a resistor R 7 Connected in parallel with capacitor C 5 And (3) upper part.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311189077.3A CN117220425A (en) | 2023-09-14 | 2023-09-14 | Foreign matter detection module for wireless charging and self-oscillation circuit |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202311189077.3A CN117220425A (en) | 2023-09-14 | 2023-09-14 | Foreign matter detection module for wireless charging and self-oscillation circuit |
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| CN117220425A true CN117220425A (en) | 2023-12-12 |
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