Low-heat-loss magnetic resonance wireless charging circuit

Abstract

The utility model provides a low-heat-loss magnetic resonance wireless charging circuit, and belongs to the technical field of wireless charging. The circuit comprises an energy transmitting end and an energy receiving end, the energy transmitting end and the energy receiving end are coupled and communicated through a coupling mechanism, the coupling mechanism comprises a transmitting coil and a receiving coil, the energy transmitting end comprises a direct current input end and a high-frequency inversion module, and direct current input by the direct current input end generates oscillation signals through the high-frequency inversion module; the signals are transmitted to the receiving coil through the transmitting coil; the energy receiving end comprises a rectifier module and a load. The receiving coil receives the oscillation signal, rectifies the oscillation signal through the rectifier module and transmits the rectified signal to the load. The circuit is high in power, high in energy transmission efficiency and low in heat loss.

Description

Technical Field

[0001] The utility model belongs to the technical field of wireless charging, and particularly relates to a low-heat-loss magnetic resonance wireless charging circuit. Background Art

[0002] Wireless charging technology, as a research hotspot in the current field of electronic technology, has attracted extensive attention at home and abroad. Abroad, technology giants represented by Apple and Samsung have taken the lead in applying wireless charging technology to their products and continuously promoted technological innovation. At the same time, top universities such as the Massachusetts Institute of Technology have also made remarkable breakthroughs in the theoretical research and practical application of wireless charging.

[0003] In China, with the popularization of electronic devices and the increasing demand of consumers for charging convenience, wireless charging technology has developed rapidly. However, the existing wireless charging technology has problems such as low transmission power, low energy transmission efficiency, and large heat loss, which restrict the application of wireless charging technology in various industries. Summary of the Invention

[0004] In view of this, the purpose of the utility model is to provide a low-heat-loss magnetic resonance wireless charging circuit with small size and high reliability to overcome the deficiencies of the prior art.

[0005] The purpose of the utility model can be realized by the following technical solutions: a low-heat-loss magnetic resonance wireless charging circuit, characterized by comprising an energy transmitting end and an energy receiving end, the energy transmitting end and the energy receiving end are coupled and communicated through a coupling mechanism, the coupling mechanism comprises a transmitting coil and a receiving coil, the energy transmitting end comprises a DC input end and a high-frequency inverter module, the direct current input by the DC input end generates an oscillation signal through the high-frequency inverter module and is transmitted to the receiving coil through the transmitting coil; the energy receiving end comprises a rectification module and a load, and after the receiving coil receives the oscillation signal, it is rectified by the rectification module and transmitted to the load.

[0006] Preferably, the high-frequency inverter module comprises a high-frequency transmitting circuit and a driving circuit, the driving circuit comprises a multi-stage driving sub-circuit and a DC blocking circuit, the high-frequency transmitting circuit generates an initial oscillation signal, and successively generates a high-frequency oscillation signal through the multi-stage driving sub-circuit, and the high-frequency oscillation signal is transmitted to the transmitting coil through the DC blocking circuit.

[0007] Preferably, the high-frequency transmitting circuit includes a first capacitor C1, a first resistor R1, a second resistor R2, a wireless charging transmitting chip U1, and a second capacitor C2. The positive electrode of the first capacitor C1 is connected to the positive electrode of the DC input, the negative electrode of the first capacitor C1 is grounded, the first end of the first resistor R1 is connected to the third pin of the wireless charging transmitting chip U1, the second end of the first resistor R1 is connected to the second pin of the wireless charging transmitting chip U1, the first pin of the wireless charging transmitting chip U1 is connected to the positive electrode of the DC input, the fourth pin of the wireless charging transmitting chip U1 is connected to the positive electrode of the DC input, the first end of the second resistor R2 is connected to the positive electrode of the DC input, the second end of the second resistor R2 is connected to the third pin of the wireless charging transmitting chip U1, the fifth pin of the wireless charging transmitting chip U1 is grounded through the second capacitor C2, the sixth pin of the wireless charging transmitting chip U1 is grounded, and the first pin of the wireless charging transmitting chip U1 is also connected to the positive electrode of the transmitting coil.

[0008] Preferably, the multi-stage driving sub-circuit includes wireless charging power amplification chips U2, U3, and U4; the first pin, second pin, third pin, and fourth pin of the wireless charging power amplification chip U2 are connected in parallel and then connected to the negative electrode of the transmitting coil, and the fifth pin, sixth pin, and seventh pin are connected in parallel and then grounded; the first pin, second pin, third pin, and fourth pin of the wireless charging power amplification chip U3 are connected in parallel and then connected to the negative electrode of the transmitting coil, and the fifth pin, sixth pin, and seventh pin are connected in parallel and then grounded; the first pin, second pin, third pin, and fourth pin of the wireless charging power amplification chip U4 are connected in parallel and then connected to the negative electrode of the transmitting coil, and the fifth pin, sixth pin, and seventh pin are connected in parallel and then grounded.

[0009] Preferably, the model of the wireless charging transmitting chip U1 is XKT-901, and the models of the wireless charging power amplification chips U2, U3, and U4 are all XKT-335.

[0010] Preferably, the DC blocking circuit is a capacitor C3.

[0011] Preferably, the rectification module includes a fourth capacitor C4, a fifth capacitor C5, a sixth capacitor C6, a first Schottky diode D1, a seventh capacitor C7, an indicator LED1, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a wireless charging receiving chip U5, an eighth capacitor C8, a second Schottky diode D2, a third Schottky diode D3, a fourth Schottky diode D4, a fifth Schottky diode D5, a sixth Schottky diode D6, a power transistor Q1, a ninth capacitor C9, and an inductor L1; a first end after parallel connection of the fourth capacitor C4, the fifth capacitor C5, and the sixth capacitor C6 is connected to the positive electrode of the output end of the receiving coil, and a second end is connected to the negative electrode of the output end of the receiving coil; a first positive electrode end and a negative electrode end of the first Schottky diode D1 are connected and then connected to the positive electrode of the output end of the receiving coil, and a second positive electrode end of the first Schottky diode D1 is respectively connected to the positive electrode of the seventh capacitor C7, the positive electrode of the indicator LED1, the first end of the fourth resistor, and the second pin of the wireless charging receiving chip U5; the negative electrode of the seventh capacitor C7, the negative electrode of the indicator LED1, and the third pin of the wireless charging receiving chip U5 are all connected to the negative electrode of the output end of the receiving coil; the second end of the fourth resistor R4 is respectively connected to the first pin of the wireless charging receiving chip U5 and the drain of the power transistor Q1; the fourth pin of the wireless charging receiving chip U5 is respectively connected to the first end of the fifth resistor R5 and the first end of the sixth resistor R6; the second end of the fifth resistor R5 is connected to the negative electrode of the output end of the receiving coil, and the second end of the sixth resistor R6 is connected to the fifth pin of the wireless charging receiving chip U5; the sixth pin of the wireless charging receiving chip U5 is connected to the first end of the eighth capacitor C8, and the second end of the eighth capacitor C8, the negative electrode of the second Schottky diode D2, the negative electrode of the third Schottky diode D3, the negative electrode of the fourth Schottky diode D4, the negative electrode of the fifth Schottky diode D5, and the negative electrode of the sixth Schottky diode D6 are all connected to the seventh pin of the wireless charging receiving chip U5, and the positive electrode of the second Schottky diode D2, the positive electrode of the third Schottky diode D3, the positive electrode of the fourth Schottky diode D4, the positive electrode of the fifth Schottky diode D5, and the positive electrode of the sixth Schottky diode D6 are all connected to the negative electrode of the output end of the receiving coil; the eighth pin of the wireless charging receiving chip U5 is connected to the gate of the power transistor Q1, and the source of the power transistor Q1 is respectively connected to the first end of the inductor L1 and the seventh pin of the wireless charging receiving chip U5; the second end of the inductor L1 is connected to the second end of the sixth resistor and the positive electrode of the ninth capacitor C9, and the negative electrode of the ninth capacitor C9 is connected to the negative electrode of the output end of the receiving coil. The positive electrode and the negative electrode of the ninth capacitor C9 are respectively used for connecting a load.

[0012] Preferably, the model of the wireless charging receiving chip U5 is XKT-901.

[0013] Preferably, the shapes of the transmitting coil and the receiving coil are circular rings, the number of turns of the transmitting coil and the receiving coil is 20 - 25 turns, the outer diameter of the transmitting coil and the receiving coil is 75 - 85 mm, and the inner diameter is 15 - 25 mm.

[0014] Compared with the prior art, the low heat loss magnetic resonance wireless charging circuit of the present invention has the following advantages:

[0015] 1. This technology breaks through the limitations of traditional wired charging, realizes contactless transmission of electric energy through electromagnetic fields or magnetic induction, gets rid of the bondage of cables, and also avoids common problems such as cable entanglement and damage, greatly improving the user experience.

[0016] 2. The wireless charging technology has excellent compatibility and universality.

[0017] 3. The wireless charging technology also has a high level of safety. There are no potential safety hazards such as electric sparks that may occur when plugging and unplugging cables.

[0018] 4. The wireless charging technology also embodies the concept of energy conservation and environmental protection. By optimizing the energy transmission process, unnecessary energy losses are reduced, making a positive contribution to environmental protection.

[0019] 5. It realizes high-efficiency, high-power, stable and safe charging. By using a multi-stage drive sub-circuit and a DC-blocking circuit, and through frequency doubling and frequency selection, the frequency of the transmitted signal is increased, thereby ensuring the distance and effect of wireless charging. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is the principle block diagram of an embodiment of the present invention.

[0021] Figure 2 is the circuit schematic diagram of the energy transmitting end of an embodiment of the present invention.

[0022] Figure 3 is the circuit schematic diagram of the energy receiving end of an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] The following are specific embodiments of the present invention and in combination with the accompanying drawings, the technical solutions of the present invention are further described, but the present invention is not limited to these embodiments.

[0024] Such as Figure 1As shown in the figure, the utility model provides a low heat loss magnetic resonance wireless charging circuit, which includes an energy transmitting end and an energy receiving end. The energy transmitting end and the energy receiving end are coupled and connected through a coupling mechanism. The coupling mechanism includes a transmitting coil and a receiving coil. The energy transmitting end includes a DC input end and a high-frequency inversion module. The direct current input through the DC input end generates an oscillation signal through the high-frequency inversion module and is transmitted to the receiving coil through the transmitting coil. The energy receiving end includes a rectification module and a load. After receiving the oscillation signal, the receiving coil is rectified by the rectification module and transmitted to the load.

[0025] Specifically, as Figure 2 shown in the figure, the high-frequency inversion module includes a high-frequency transmitting circuit and a driving circuit. The driving circuit includes multiple levels of driving sub-circuits and a DC blocking circuit. The high-frequency transmitting circuit generates an initial oscillation signal, which successively generates a high-frequency oscillation signal through multiple levels of driving sub-circuits. The high-frequency oscillation signal is transmitted to the transmitting coil through the DC blocking circuit. By means of frequency doubling and frequency selection, the frequency of the transmitted signal is increased, thereby ensuring the distance and effect of wireless charging.

[0026] Among them, the high-frequency transmitting circuit includes a first capacitor C1, a first resistor R1, a second resistor R2, a wireless charging transmitting chip U1, and a second capacitor C2. The positive electrode of the first capacitor C1 is connected to the positive electrode of the DC input end, the negative electrode of the first capacitor C1 is grounded, the first end of the first resistor R1 is connected to the third pin of the wireless charging transmitting chip U1, the second end of the first resistor R1 is connected to the second pin of the wireless charging transmitting chip U1, the first pin of the wireless charging transmitting chip U1 is connected to the positive electrode of the DC input end, the fourth pin of the wireless charging transmitting chip U1 is connected to the positive electrode of the DC input end, the first end of the second resistor R2 is connected to the positive electrode of the DC input end, the second end of the second resistor R2 is connected to the third pin of the wireless charging transmitting chip U1, the fifth pin of the wireless charging transmitting chip U1 is grounded through the second capacitor C2, the sixth pin of the wireless charging transmitting chip U1 is grounded, and the first pin of the wireless charging transmitting chip U1 is also connected to the positive electrode of the transmitting coil. The wireless charging transmitting chip U1 uses XKT-901 as the driving chip of the wireless transmitting circuit to achieve electromagnetic wireless power supply and provide a stable alternating current to the transmitting coil.

[0027] In this embodiment, the multi-stage drive sub-circuit is implemented by cascading three drive sub-circuits. The three drive sub-circuits are respectively composed of wireless charging power amplifier chips U2, U3, and U4, and the wireless charging power amplifier chips U2, U3, and U4 all adopt XKT-335. The first pin, second pin, third pin, and fourth pin of the wireless charging power amplifier chip U2 are connected in parallel and then connected to the negative pole of the transmitting coil, and the fifth pin, sixth pin, and seventh pin are connected in parallel and then grounded; the first pin, second pin, third pin, and fourth pin of the wireless charging power amplifier chip U3 are connected in parallel and then connected to the negative pole of the transmitting coil, and the fifth pin, sixth pin, and seventh pin are connected in parallel and then grounded; the first pin, second pin, third pin, and fourth pin of the wireless charging power amplifier chip U4 are connected in parallel and then connected to the negative pole of the transmitting coil, and the fifth pin, sixth pin, and seventh pin are connected in parallel and then grounded.

[0028] The DC blocking circuit is the third capacitor C3. The two ends of the third capacitor C3 are respectively connected to the positive / negative poles of the transmitting coil, and the direct current is filtered through the third capacitor C3.

[0029] Such as Figure 3As shown in the figure, the rectification module includes the fourth capacitor C4, the fifth capacitor C5, the sixth capacitor C6, the first Schottky diode D1, the seventh capacitor C7, the indicator light LED1, the third resistor R3, the fourth resistor R4, the fifth resistor R5, the sixth resistor R6, the wireless charging receiving chip U5, the eighth capacitor C8, the second Schottky diode D2, the third Schottky diode D3, the fourth Schottky diode D4, the fifth Schottky diode D5, the sixth Schottky diode D6, the power transistor Q1, the ninth capacitor C9 and the inductor L1. In this embodiment, the fourth capacitor C4, the seventh capacitor C7 and the ninth capacitor C9 are all electrolytic capacitors. The wireless charging receiving chip U5 also adopts XKT-901 to receive the alternating current collected by the receiving coil. The first ends of the fourth capacitor C4, the fifth capacitor C5 and the sixth capacitor C6 after being connected in parallel are connected to the positive pole of the output end of the receiving coil, and the second ends are connected to the negative pole of the output end of the receiving coil, forming a rectification circuit to rectify the received alternating current. The first Schottky diode D1 adopts VS-43CTQ100S-M3. After its first positive terminal and negative terminal are connected, they are connected to the positive pole of the output end of the receiving coil. Its second positive terminal is respectively connected to the positive pole of the seventh capacitor C7, the positive pole of the indicator light LED1, the first end of the fourth resistor and the second pin of the wireless charging receiving chip U5. The negative pole of the seventh capacitor C7, the negative pole of the indicator light LED1 and the third pin of the wireless charging receiving chip U5 are all connected to the negative pole of the output end of the receiving coil; the second end of the fourth resistor R4 is respectively connected to the first pin of the wireless charging receiving chip U5 and the drain of the power transistor Q1; the fourth pin of the wireless charging receiving chip U5 is respectively connected to the first end of the fifth resistor R5 and the first end of the sixth resistor R6; the second end of the fifth resistor R5 is connected to the negative pole of the output end of the receiving coil, and the second end of the sixth resistor R6 is connected to the fifth pin of the wireless charging receiving chip U5; the sixth pin of the wireless charging receiving chip U5 is connected to the first end of the eighth capacitor C8, and the second end of the eighth capacitor C8, the negative pole of the second Schottky diode D2, the negative pole of the third Schottky diode D3, the negative pole of the fourth Schottky diode D4, the negative pole of the fifth Schottky diode D5 and the negative pole of the sixth Schottky diode D6 are all connected to the seventh pin of the wireless charging receiving chip U5. The positive poles of the second Schottky diode D2, the third Schottky diode D3, the fourth Schottky diode D4, the fifth Schottky diode D5 and the sixth Schottky diode D6 are all connected to the negative pole of the output end of the receiving coil; the eighth pin of the wireless charging receiving chip U5 is connected to the gate of the power transistor Q1. The source of the power transistor Q1 is respectively connected to the first end of the inductor L1 and the seventh pin of the wireless charging receiving chip U5; the second end of the inductor L1 is connected to the second end of the sixth resistor and the positive pole of the ninth capacitor C9. The negative pole of the ninth capacitor C9 is connected to the negative pole of the output end of the receiving coil. The positive pole and negative pole of the ninth capacitor C9 are respectively used to connect the load.

[0030] In this embodiment, the shapes of the transmitting coil and the receiving coil adopt a circular coil structure, and the specific parameters are as follows: the number of turns is 20 - 25 turns, the outer diameter is 75 - 85 mm, and the inner diameter is 15 - 25 mm. In other embodiments of the present utility model, the shapes of the transmitting coil and the receiving coil can also adopt a square ring coil structure. Specifically, it can be set according to actual requirements.

[0031] The present utility model adopts magnetic resonance technology. An initial oscillation signal is generated through a high-frequency oscillation circuit, and then through the processing of a drive circuit, a transmission signal required for wireless charging is generated and transmitted; by using a multi-stage drive sub-circuit and a DC blocking circuit, the frequency of the transmission signal is increased through frequency doubling and frequency selection, thereby ensuring the distance and effect of wireless charging. And through the parameter design of the transmitting coil and the receiving coil, it is realized that less heat is generated by the coil while ensuring a relatively high power factor of the system.

[0032] The specific embodiments described herein are merely illustrative of the spirit of the present utility model. Those skilled in the art to which the present utility model pertains can make various modifications or supplements to the described specific embodiments or use similar methods for substitution, but will not deviate from the spirit of the present utility model or exceed the scope defined by the appended claims.

Claims

1. A low thermal loss magnetic resonance wireless charging circuit, characterized in that, It includes an energy transmitting end and an energy receiving end. The energy transmitting end and the energy receiving end are coupled and connected through a coupling mechanism. The coupling mechanism includes a transmitting coil and a receiving coil. The energy transmitting end includes a DC input end and a high-frequency inversion module. The direct current input through the DC input end generates an oscillation signal through the high-frequency inversion module and is transmitted to the receiving coil through the transmitting coil. The energy receiving end includes a rectification module and a load. After receiving the oscillation signal, the receiving coil is rectified by the rectification module and transmitted to the load.

2. The low heat loss magnetic resonance wireless charging circuit according to claim 1, characterized in that, The high-frequency inversion module includes a high-frequency transmitting circuit and a driving circuit. The driving circuit includes multiple levels of driving sub-circuits and a DC blocking circuit. The high-frequency transmitting circuit generates an initial oscillation signal, and successively generates a high-frequency oscillation signal through multiple levels of driving sub-circuits. The high-frequency oscillation signal is transmitted to the transmitting coil through the DC blocking circuit.

3. The low thermal loss magnetic resonance wireless charging circuit according to claim 2, wherein The high-frequency transmitting circuit includes a first capacitor C1, a first resistor R1, a second resistor R2, a wireless charging transmitting chip U1, and a second capacitor C2. The positive electrode of the first capacitor C1 is connected to the positive electrode of the DC input end, the negative electrode of the first capacitor C1 is grounded. The first end of the first resistor R1 is connected to the third pin of the wireless charging transmitting chip U1, the second end of the first resistor R1 is connected to the second pin of the wireless charging transmitting chip U1. The first pin of the wireless charging transmitting chip U1 is connected to the positive electrode of the DC input end, the fourth pin of the wireless charging transmitting chip U1 is connected to the positive electrode of the DC input end. The first end of the second resistor R2 is connected to the positive electrode of the DC input end, the second end of the second resistor R2 is connected to the third pin of the wireless charging transmitting chip U1. The fifth pin of the wireless charging transmitting chip U1 is grounded through the second capacitor C2, the sixth pin of the wireless charging transmitting chip U1 is grounded. The first pin of the wireless charging transmitting chip U1 is also connected to the positive electrode of the transmitting coil.

4. A low thermal loss magnetic resonance wireless charging circuit according to claim 3, wherein The multiple levels of driving sub-circuits include wireless charging power amplification chips U2, U3, and U4. The first pin, second pin, third pin, and fourth pin of the wireless charging power amplification chip U2 are connected in parallel and then connected to the negative electrode of the transmitting coil, and the fifth pin, sixth pin, and seventh pin are connected in parallel and then grounded. The first pin, second pin, third pin, and fourth pin of the wireless charging power amplification chip U3 are connected in parallel and then connected to the negative electrode of the transmitting coil, and the fifth pin, sixth pin, and seventh pin are connected in parallel and then grounded. The first pin, second pin, third pin, and fourth pin of the wireless charging power amplification chip U4 are connected in parallel and then connected to the negative electrode of the transmitting coil, and the fifth pin, sixth pin, and seventh pin are connected in parallel and then grounded.

5. A low heat loss magnetic resonance wireless charging circuit according to claim 4, characterized in that, The model of the wireless charging transmitting chip U1 is XKT-901, and the models of the wireless charging power amplification chips U2, U3, and U4 are all XKT-335.

6. A low heat loss magnetic resonance wireless charging circuit according to any one of claims 2-5, characterized in that, The DC blocking circuit is a third capacitor C3, and both ends of the third capacitor C3 are respectively connected to the positive / negative electrodes of the transmitting coil.

7. The low heat loss magnetic resonance wireless charging circuit according to claim 6, wherein The rectification module includes a fourth capacitor C4, a fifth capacitor C5, a sixth capacitor C6, a first Schottky diode D1, a seventh capacitor C7, an indicator light LED1, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a wireless charging receiving chip U5, an eighth capacitor C8, a second Schottky diode D2, a third Schottky diode D3, a fourth Schottky diode D4, a fifth Schottky diode D5, a sixth Schottky diode D6, a power transistor Q1, a ninth capacitor C9, and an inductor L1; the first ends of the fourth capacitor C4, the fifth capacitor C5, and the sixth capacitor C6 after being connected in parallel are connected to the positive pole of the output end of the receiving coil, and the second ends are connected to the negative pole of the output end of the receiving coil; the first positive end and the negative end of the first Schottky diode D1 are connected and then connected to the positive pole of the output end of the receiving coil, and the second positive end of the first Schottky diode D1 is respectively connected to the positive pole of the seventh capacitor C7, the positive pole of the indicator light LED1, the first end of the fourth resistor, and the second pin of the wireless charging receiving chip U5; the negative pole of the seventh capacitor C7, the negative pole of the indicator light LED1, and the third pin of the wireless charging receiving chip U5 are all connected to the negative pole of the output end of the receiving coil; the second end of the fourth resistor R4 is respectively connected to the first pin of the wireless charging receiving chip U5 and the drain of the power transistor Q1; the fourth pin of the wireless charging receiving chip U5 is respectively connected to the first end of the fifth resistor R5 and the first end of the sixth resistor R6; the second end of the fifth resistor R, the second end of the sixth resistor R6 is connected to the fifth pin of the wireless charging receiving chip U5; the sixth pin of the wireless charging receiving chip U5 is connected to the first end of the eighth capacitor C8, and the second end of the eighth capacitor C8, the negative pole of the second Schottky diode D2, the negative pole of the third Schottky diode D3, the negative pole of the fourth Schottky diode D4, the negative pole of the fifth Schottky diode D5, and the negative pole of the sixth Schottky diode D6 are all connected to the seventh pin of the wireless charging receiving chip U5, and the positive poles of the second Schottky diode D2, the third Schottky diode D3, the fourth Schottky diode D4, the fifth Schottky diode D5, and the sixth Schottky diode D6 are all connected to the negative pole of the output end of the receiving coil; the eighth pin of the wireless charging receiving chip U5 is connected to the gate of the power transistor Q1, and the source of the power transistor Q1 is respectively connected to the first end of the inductor L1 and the seventh pin of the wireless charging receiving chip U5; the second end of the inductor L1 is connected to the second end of the sixth resistor and the positive pole of the ninth capacitor C9, and the negative pole of the ninth capacitor C9 is connected to the negative pole of the output end of the receiving coil. The positive and negative poles of the ninth capacitor C9 are respectively used to connect to a load.

8. The low heat loss magnetic resonance wireless charging circuit according to claim 7, characterized in that The model of the wireless charging receiving chip U5 is XKT-901.

9. A low heat loss magnetic resonance wireless charging circuit according to any one of claims 1-5, characterized in that, The shapes of the transmitting coil and the receiving coil are circular rings, the number of turns of the transmitting coil and the receiving coil is 20 - 25 turns, the outer diameter of the transmitting coil and the receiving coil is 75 - 85 mm, and the inner diameter is 15 - 25 mm.

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