Lightweight energy receiving device and energy coupling mechanism for large magnetic field space

Abstract

This invention relates to the field of magnetically coupled resonant wireless power transmission technology, specifically disclosing a lightweight energy receiving device and an energy coupling mechanism for use in large magnetic field spaces. The lightweight energy receiving device includes a cylindrical magnetic core and upper and lower planar magnetic cores respectively disposed at the top and bottom of the cylindrical magnetic core. It also includes a receiving coil wound around the cylindrical magnetic core, the receiving coil being wound into multiple planar coils sequentially connected along the axial direction of the cylindrical magnetic core, each planar coil being radially wound around the cylindrical magnetic core. The energy coupling mechanism includes a cylindrical energy transmitting coil and the lightweight energy receiving device. This lightweight energy receiving device can receive sufficient energy without causing excessive equivalent resistance that limits its power output, meeting the power requirements for long-distance wireless power transmission. It also has a certain resistance to angular offset, and its overall size and weight are small, making it suitable for general low-power electrical equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetically coupled resonant wireless energy transmission, and in particular to a lightweight energy receiving device for a large magnetic field space and an energy coupling mechanism. Background Art

[0002] Wireless power transmission, also known as contactless power transfer (CPT), is a new form of power transmission and a revolutionary advancement. Figure 1 The structure diagram of the wireless charging system is shown, which mainly includes: the conversion circuit from industrial frequency AC to high frequency AC, the primary compensation network and the multi-coil matrix at the power supply end, the secondary compensation network and the receiving end coil, and the high-frequency rectification circuit.

[0003] Wireless power transmission technology uses electromagnetic fields as a medium to achieve power transmission. Wireless charging is to place the primary and secondary windings on the ground and in the electrical equipment respectively, and achieve non-contact power transmission through high-frequency magnetic field coupling. According to the different power transmission mechanisms of wireless charging, it is mainly divided into: Figure 2 Several types are shown.

[0004] The first three transmission forms (electromagnetic wave, electric field coupling and magnetic field coupling) are wireless power transmission using electromagnetic effect. The characteristics of the four common wireless charging methods are compared as shown in Table 1.

[0005] Table 1 Comparison of four wireless charging methods

[0006]

[0007] At present, magnetic field coupling wireless power transmission has received more attention. This method uses the coil on the power supply side to generate an alternating magnetic field, which is coupled to the receiving coil on the load side. The receiving end converter then converts the magnetic field energy into electrical energy, thereby realizing wireless transmission of electrical energy.

[0008] The magnetic induction type uses a loosely coupled transformer to pass an alternating current through the primary side of the transformer, and generates an induced current on the secondary side of the transformer through the principle of electromagnetic induction to achieve power transmission. This system also has its own defects, including large transformer losses, too short transmission distance, rapid decrease in transmission efficiency with increasing distance, and small lateral offset tolerance. Therefore, the general working range is from millimeters to 10cm. In addition, because its energy is divergent, the induced current is much smaller than the input current, so the efficiency of electromagnetic induction power transmission has become the most concerned issue.

[0009] The magnetic coupling resonance type is mainly based on the near-field strong coupling theory. It also uses the magnetic field as a medium to achieve wireless transmission of electrical energy through the magnetic coupling resonance between the transmitting coil and the receiving coil. The magnetic resonance technology has relatively low requirements for distance. It can support charging devices at distances of several centimeters or even meters. Because this technology uses the non-radiative energy characteristics of the near-field area to transfer energy between the transmitting coil and the receiving coil with the same resonant frequency, objects with different frequencies are basically unaffected, resulting in this technology being able to achieve efficient energy transmission over longer distances than inductive coupling technology.

[0010] At present, the distance between the primary transmitting end and the secondary receiving end of most magnetically coupled resonant wireless energy transmission systems is relatively close, and there are few system devices as far as several meters, because too far a distance will lead to low energy transmission efficiency. In addition, since wireless power is supplied to each small load in a larger space (large magnetic field space), there are two problems in the transmission of wireless power. The first is the long transmission distance, which is generally more than one meter, and the second is the small size of the receiving coil, and its energy receiving capacity is limited. Therefore, the energy transmission distance and volume limit the energy receiving capacity of each micro receiving device in a larger space. Specifically, the current problems with using micro receiving devices for energy reception in a large space are:

[0011] 1) The energy receiving device is not small and lightweight enough;

[0012] 2) The energy transmission distance is too far, greater than 1 meter, so that almost no energy can be received;

[0013] 3) The receiving power of the energy receiving device is too small;

[0014] 4) The energy receiving device has insufficient ability to resist angle deviation in space;

[0015] 5) The problem of the power conversion circuit of the energy receiving device being too complicated;

[0016] 6) The winding method and number of turns of the receiving coil in the energy receiving device cause a conflict between the series equivalent resistance and the self-inductance coefficient;

[0017] 7) The energy receiving device is too small and the magnetic core’s magnetic field gathering capacity is insufficient. Summary of the invention

[0018] The present invention provides a lightweight energy receiving device and an energy coupling mechanism for a large magnetic field space, and the technical problem to be solved is: how to overcome all the above problems.

[0019] In order to solve the above technical problems, the present invention provides a lightweight energy receiving device for a large magnetic field space, comprising a cylindrical magnetic core and an upper planar magnetic core and a lower planar magnetic core respectively arranged at the top and bottom ends of the cylindrical magnetic core, and also comprising a receiving coil wound on the cylindrical magnetic core, the receiving coil being wound into a plurality of planar coils connected in sequence along the axial direction of the cylindrical magnetic core, and each planar coil being radially wound on the cylindrical magnetic core.

[0020] Preferably, the upper planar magnetic core is parallel to the lower planar magnetic core, and the cylindrical magnetic core is perpendicular to the upper planar magnetic core and the lower planar magnetic core, and the three form an I-shaped magnetic core.

[0021] Preferably, the receiving coil is made of 0.05 mm diameter, 40 strands of silk-wrapped wire, so that the induced voltage of the receiving coil at any position in the magnetic field space is greater than the required voltage.

[0022] Preferably, the receiving coil is wound with [190, 200] turns, and its equivalent series resistance is 5Ω to 6Ω at a frequency of 150kHz.

[0023] Preferably, the I-shaped magnetic core is made of manganese-zinc ferrite and weighs (12±1) g.

[0024] Preferably, the upper planar magnetic core and the lower planar magnetic core are two identical cubes, the length, width and height of the cubes are (18.0±0.3) mm, (15.5±0.3) mm, and (2.0±0.2) mm, respectively; the height of the cylindrical magnetic core is (38.0±0.5) mm and the diameter is (6.0±0.2) mm.

[0025] A lightweight energy receiving device for a large magnetic field space also includes an energy conversion circuit module connected to the receiving coil; the energy conversion circuit module includes a series resonant capacitor, a rectifier filter circuit and a voltage stabilizing circuit; the rectifier filter circuit uses a rectifier bridge and a first capacitor and a second capacitor connected in parallel in sequence, and the voltage stabilizing circuit uses a linear regulator, a filter capacitor and an energy storage capacitor connected in parallel in sequence; one end of the series resonant capacitor is connected to one end of the receiving coil, and the other end of the series resonant capacitor and the other end of the receiving coil are respectively connected to the two ends of the rectifier bridge.

[0026] The invention provides a lightweight energy receiving device for use in a large magnetic field space, which has the following beneficial effects:

[0027] 1. The magnetic core is designed to be an I-shaped part, which has a better magnetic field gathering effect, and magnetic sheets (upper plane magnetic core and lower plane magnetic core) are added at both ends of the cylindrical magnetic core, so that the energy receiving device has a certain ability to resist angle deviation when receiving energy;

[0028] 2. Considering the equivalent resistance of the receiving coil and the mutual inductance coefficient of the primary and secondary sides, through multiple experiments, a more appropriate number of coil turns and winding method were selected so that the receiving coil can receive enough energy without causing the equivalent resistance to be too large to limit its power output;

[0029] 3. The core part adopts the manganese-zinc ferrite material with mature technology and easy processing. The material is cheap and easy to buy, and the processing procedure is simple;

[0030] 4. The energy conversion circuit module uses a series resonant capacitor for secondary resonance, a rectifier bridge, capacitors, etc. for rectification and filtering, and a linear regulator, capacitors, etc. for voltage stabilization to obtain a DC power of a specific voltage. The circuit is simple and easy to build, and a small circuit board can be obtained;

[0031] 5. The overall size of the energy receiving device is small and the weight is light, meeting the requirements of miniaturization and lightweight;

[0032] 6. The maximum output power measured in the system is 1.05W, which meets the power requirements of long-distance wireless power transmission and is suitable for general low-power electrical equipment.

[0033] The present invention also provides an energy coupling mechanism, including a cylindrical energy transmitting coil, wherein the inner space of the cylindrical energy transmitting coil forms a vertically alternating cylindrical magnetic field space after being excited; and also includes more than one of the above-mentioned lightweight energy receiving devices distributed in the cylindrical magnetic field space.

[0034] Preferably, the cylindrical energy emitting coil is spirally wound into a cylindrical shape, and the diameter of the cylindrical energy emitting coil is (3±0.1) m and the height is (3±0.1) m.

[0035] The energy coupling mechanism provided by the present invention has the following beneficial effects:

[0036] A cylindrical energy transmitting coil (about 3m in diameter) is used to provide a large magnetic field space (vertically alternating cylindrical magnetic field space) for several lightweight energy receiving devices, so that the output power of the energy receiving device at any position in the space is above 1.05W, meeting the power requirements of general small-power electrical equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic block diagram of the structure of a wireless charging system provided by the background technology of the present invention;

[0038] Figure 2 It is a schematic block diagram of the classification of existing wireless power transmission provided by the background technology of the present invention;

[0039] Figure 3is a schematic diagram of a transmitting coil and a receiving coil in an energy coupling mechanism provided by an embodiment of the present invention;

[0040] Figure 4 is a partial cross-sectional view of a transmitting coil magnetic core provided by an embodiment of the present invention;

[0041] Figure 5 is the relationship between the magnetic induction intensity and the length of the receiving coil core provided by the embodiment of the present invention;

[0042] Figure 6 is a structural diagram of a receiving coil and a magnetic core thereof provided in an embodiment of the present invention;

[0043] Figure 7 is a circuit diagram of an energy conversion circuit module provided by an embodiment of the present invention;

[0044] Figure 8 This is a diagram of voltage test results of an energy receiving device at a location with the weakest field strength provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0045] The following specifically illustrates the implementation mode of the present invention in conjunction with the accompanying drawings. The embodiments are provided for illustrative purposes only and cannot be understood as limiting the present invention. The accompanying drawings are provided 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.

[0046] like Figure 3 As shown, this embodiment provides an energy coupling structure, including a cylindrical energy transmitting coil and a lightweight energy receiving device. After the cylindrical energy transmitting coil is excited, its internal space forms a vertically alternating cylindrical magnetic field space. A number of lightweight energy receiving devices are placed in the cylindrical magnetic field space to receive energy. The cylindrical energy transmitting coil (hereinafter referred to as the transmitting coil) is spirally wound by a number of turns of excitation wire, which forms a cylindrical magnetic field space with a diameter of (3.0±0.1) m and a height of (3.0±0.1) m. Since the corresponding transmitting coil in the system is a cylindrical solenoid with a diameter of about 3 m, the direction of the magnetic flux lines inside the cylinder is parallel to the transmitting coil, as shown in FIG. Figure 4 The figure shows a partial cross-sectional view of the transmitting coil, where the arrows are the direction of the magnetic flux lines, the colors represent the magnetic flux density, i.e. the magnetic induction intensity B, the darker the color, the stronger the magnetic field intensity, each black dot arranged vertically on the right represents the cross section of each turn of the transmitting coil, the black concentrated area on the left of the black dot represents the internal space of the transmitting coil, and the right represents the external space. It can be seen that the magnetic field in the internal space is distributed vertically, so the receiving magnetic core of the energy receiving device can be a rod-shaped magnetic core, and the receiving coil is wound horizontally on the rod-shaped magnetic core. When placed, the rod-shaped magnetic core is kept upright in the cylindrical magnetic field space of the transmitting coil to receive energy to the greatest extent.

[0047] Through simulation, we can also know that the magnetic induction intensity has a great relationship with the length of the magnetic core, that is, the longer the magnetic core, the greater the magnetic induction intensity inside the magnetic core. Figure 5 The embodiment of the present invention provides a lightweight energy receiving device for use in a large magnetic field space, such as Figure 6 As shown, it includes a cylindrical magnetic core and an upper planar magnetic core and a lower planar magnetic core respectively arranged at the top and bottom ends of the cylindrical magnetic core, and also includes a receiving coil wound on the cylindrical magnetic core, the receiving coil is wound into a plurality of planar coils connected in sequence along the axial direction of the cylindrical magnetic core, and each planar coil is radially wound on the cylindrical magnetic core.

[0048] The upper planar magnetic core and the lower planar magnetic core are used to further increase the magnetic induction intensity of the cylindrical magnetic core, and at the same time, to reduce the influence of the cylindrical magnetic core on the magnetic induction intensity of the magnetic core when it has a certain inclined angle with the magnetic flux lines of the transmitting coil. Therefore, two thinner planar magnetic cores are added at both ends of the cylindrical magnetic core, and finally an I-shaped magnetic core is formed, which is called an I-shaped magnetic core in this example.

[0049] The transmitting coil has no magnetic core and is a 16-turn hollow spiral wound with Litz wire. When the current of the transmitting coil remains unchanged, the type of Litz wire will not affect the receiving performance of the coil. The number of turns of the transmitting coil is positively correlated with the output of the receiving coil. 16 turns is the minimum number of turns to meet the output power of the receiving coil.

[0050] This embodiment is preferred, such as Figure 6 As shown, the upper plane core is parallel to the lower plane core, and the cylindrical core is perpendicular to the upper plane core and the lower plane core. The height of the cylindrical core is (38.0±0.5) mm and the diameter is (6.0±0.2) mm. The I-shaped core is made of manganese-zinc ferrite. In this example, its weight is controlled at about 12g, and the best weight is (12.0±1) g. The upper plane core and the lower plane core are two identical cubes, and the length, width and height of the cube are (18.0±0.3) mm, (15.5±0.3) mm, and (2.0±0.2) mm respectively.

[0051] When splicing, the centers of the upper and lower ends of the cylindrical core are aligned with the centers of the two planar cores, and JL-498 metal quick-drying strong glue is used for bonding and splicing.

[0052] Commonly used soft magnetic materials include silicon steel sheets, pure iron, Permalloy, nickel-zinc ferrite, manganese-zinc ferrite and amorphous nanocrystalline alloy materials. Among them, the magnetic permeability of silicon steel sheets and nickel-zinc ferrite is relatively low, so they can be excluded first, while the low resistivity of pure iron and Permalloy leads to high eddy current loss, so they can also be excluded, so in the end, two materials are mainly considered, namely manganese-zinc ferrite and amorphous nanocrystalline alloy. Considering the lightweight requirements of the energy receiving device, the weight of the magnetic core should be less than 20g. Since the shape of the magnetic core has been roughly determined, and the soft magnetic materials of amorphous nanocrystalline alloys are mostly thin strips, it is difficult to process them into an I-shaped shape. Although the performance of manganese-zinc ferrite is slightly worse than that of amorphous nanocrystalline alloys, its products are mature, easy to process, and there are many shapes to choose from, which is convenient for procurement, so the material of the magnetic core is finally selected as manganese-zinc ferrite.

[0053] Next is the design of the receiving coil. Since the energy receiving device needs to receive enough energy at any position in the space, and the magnetic field is generally weak in the middle of the space, it is necessary to wind a considerable number of turns to increase the self-inductance of the receiving coil, thereby increasing the mutual inductance coefficient of the primary and secondary sides. At the same time, as the number of coil turns increases, the equivalent series resistance of the coil also becomes non-negligible, and even becomes the main reason for limiting the output power of the receiving coil. Therefore, it is necessary to consider reducing the equivalent series resistance of the receiving coil as much as possible.

[0054] After many experimental comparisons, the Litz wire with a diameter of 0.05mm and 40 strands was selected. When the transmitting coil was passed with an effective value of (9.5±0.5)A alternating current, the induced voltage at any position in the cylindrical magnetic field space was greater than 12.6V, which was convenient for the subsequent circuit to adjust the voltage. Regarding the winding method of the receiving coil, the most important principle is to minimize the inter-turn voltage of the coil as much as possible, thereby reducing the equivalent series resistance of the entire coil. Therefore, the receiving coil is wound into multiple planar coils connected in sequence along the axial direction of the cylindrical magnetic core. Each planar coil is radially wound on the cylindrical magnetic core, such as Figure 6 As shown. When the number of turns of the receiving coil is between 190 and 200, the decrease in its equivalent series resistance at 150kHz is not obvious, while the induced voltage of the coil decreases linearly; when the number of turns of the receiving coil is greater than 200, the induced voltage of the coil rises slowly, while the increase in its equivalent series resistance at 150kHz is large, which causes the output power of the receiving device to decrease and does not meet the power requirements. Therefore, the number of turns of the receiving coil should be between 190 and 200. When the number of turns is 200, the output power of the energy receiving device is the largest. In this example, the receiving coil is wound with about 200 turns, with a total of 4 layers of planar coils, and each layer is wound with about 50 turns. It should be pointed out that Figure 6This is only to illustrate the winding method of the receiving coil, and does not represent the shape of the receiving coil after winding. The equivalent series resistance of the receiving coil is about 5Ω to 6Ω at a frequency of 150kHz. When the lightweight energy receiving device is placed vertically, the output power is the largest, and its maximum offset angle is 60° perpendicular to the bottom surface.

[0055] The lightweight energy receiving device provided in this embodiment also includes an energy conversion circuit module connected to the receiving coil. The function of the energy conversion circuit module is to convert the alternating current sensed by the receiving coil into stable direct current to power the electrical equipment. The energy conversion circuit module mainly includes three parts: a resonant compensation network (using a series resonant capacitor), a rectifier filter circuit, and a voltage stabilization circuit. Figure 7 The rectifier and filter circuit uses a rectifier bridge D2, a first capacitor C7, and a second capacitor C8 connected in parallel in sequence, and the voltage stabilization circuit uses a linear voltage stabilizer U1, a filter capacitor C10, and an energy storage capacitor C9 connected in parallel in sequence. Figure 7 In the figure, the series resonant capacitor is specifically formed by capacitors C1 to C6 connected in parallel. It can be seen from the connection that one end of the series resonant capacitor (through pin 1 of interface H1) is connected to one end of the receiving coil, and the other end of the series resonant capacitor and the other end of the receiving coil (through pin 2 of interface H1) are respectively connected to the two ends of the rectifier bridge D2. The circuit module is simple in structure and easy to build. Except for the slightly larger volume of the energy storage capacitor C9, the volumes of other components are small, and a small circuit board can be obtained as a whole. The size of the circuit board designed in this example is 32*12mm.

[0056] The following describes the power output test process and results of the energy receiving device. When the transmitting coil is passed with an effective value of (9.5±0.5)A AC, a 25Ω resistor is connected to the load of the energy receiving device, and the energy receiving device is placed at the position with the weakest field strength in space. The voltage test results are as follows: Figure 8 As shown, we can see that the voltage across the resistor is 5.13V. According to the formula P = U 2 / R, the load output power is 1.05W.

[0057] In summary, the embodiment of the present invention provides a lightweight energy receiving device for a large magnetic field space, which has the following beneficial effects:

[0058] 1. The magnetic core is designed to be an I-shaped part, which has a better magnetic field gathering effect. Magnetic sheets (upper plane magnetic core and lower plane magnetic core) are added at both ends of the cylindrical magnetic core, so that the energy receiving device has a certain ability to resist angle deviation when receiving energy (the maximum deviation angle is 60° perpendicular to the bottom surface);

[0059] 2. Considering the equivalent resistance of the receiving coil and the mutual inductance coefficient of the primary and secondary sides, through multiple experiments, a more appropriate number of coil turns and winding method were selected so that the receiving coil can receive enough energy without causing the equivalent resistance to be too large to limit its power output;

[0060] 3. The core part adopts the manganese-zinc ferrite material with mature technology and easy processing. The material is cheap and easy to buy, and the processing procedure is simple;

[0061] 4. The energy conversion circuit module uses a series resonant capacitor for secondary resonance, a rectifier bridge, capacitors, etc. for rectification and filtering, and a linear regulator, capacitors, etc. for voltage stabilization to obtain a DC power of a specific voltage. The circuit is simple and easy to build, and a small circuit board can be obtained;

[0062] 5. The overall size of the energy receiving device is small and the weight is light, meeting the requirements of miniaturization and lightweight;

[0063] 6. The maximum output power at the weakest point of the spatial magnetic field measured in the system is 1.05W, which meets the power requirements for long-distance wireless power transmission and is suitable for general low-power electrical equipment.

[0064] An energy coupling mechanism is provided, which has the following beneficial effects:

[0065] A cylindrical energy transmitting coil (about 3m in diameter) is used to provide a large magnetic field space (vertically alternating cylindrical magnetic field space) for several lightweight energy receiving devices, so that the output power of the energy receiving device at any position in the space is above 1.05W, meeting the power requirements of general small-power electrical equipment.

[0066] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. Energy coupling mechanism, characterized in that: The invention comprises a cylindrical energy transmitting coil, which is spirally wound into a cylindrical shape, and the inner space of the cylindrical energy transmitting coil forms a vertically alternating cylindrical magnetic field space after being excited; and more than one lightweight energy receiving device distributed in the cylindrical magnetic field space, wherein the lightweight energy receiving device comprises a cylindrical magnetic core and an upper plane magnetic core and a lower plane magnetic core respectively arranged at the top and bottom ends of the cylindrical magnetic core, and further comprises a receiving coil wound on the cylindrical magnetic core, wherein the receiving coil is wound into a plurality of plane coils sequentially connected along the axial direction of the cylindrical magnetic core, and each plane coil is radially wound on the cylindrical magnetic core; the upper plane magnetic core is parallel to the lower plane magnetic core, and the cylindrical magnetic core is perpendicular to the upper plane magnetic core and the lower plane magnetic core, and the three form an I-shaped magnetic core; when the lightweight energy receiving device is placed, the cylindrical magnetic core is kept upright in the cylindrical magnetic field space of the cylindrical energy transmitting coil.

2. The energy coupling mechanism according to claim 1, characterized in that: The receiving coil is made of 0.05 mm diameter, 40 strands of silk-wrapped wire, so that the induced voltage of the receiving coil at any position in the magnetic field space is greater than the required voltage.

3. The energy coupling mechanism according to claim 2, characterized in that: The receiving coil is wound with [190, 200] turns, and its equivalent series resistance is 5Ω to 6Ω at a frequency of 150kHz.

4. The energy coupling mechanism according to claim 3, characterized in that: The I-shaped magnetic core is made of manganese-zinc ferrite and weighs (12±1) g.

5. The energy coupling mechanism according to claim 4, characterized in that: The upper planar magnetic core and the lower planar magnetic core are two identical cubes, the length, width and height of the cubes are (18.0±0.3) mm, (15.5±0.3) mm and (2.0±0.2) mm respectively; the height of the cylindrical magnetic core is (38.0±0.5) mm and the diameter is (6.0±0.2) mm.

6. The energy coupling mechanism according to any one of claims 1 to 5, characterized in that: It also includes an energy conversion circuit module connected to the receiving coil; the energy conversion circuit module includes a series resonant capacitor, a rectifier filter circuit and a voltage stabilizing circuit; the rectifier filter circuit adopts a rectifier bridge and a first capacitor and a second capacitor connected in parallel in sequence, and the voltage stabilizing circuit adopts a linear regulator, a filter capacitor and an energy storage capacitor connected in parallel in sequence; one end of the series resonant capacitor is connected to one end of the receiving coil, and the other end of the series resonant capacitor and the other end of the receiving coil are respectively connected to the two ends of the rectifier bridge.

7. The energy coupling mechanism according to claim 1, characterized in that: The diameter of the cylindrical energy transmitting coil is (3±0.1) m and the height is (3±0.1) m.

Images