KR20100128395A - Devices and methods for non-contact power transmission - Google Patents

Abstract

PURPOSE: A non-contact power transmitting device and a transmitting method thereof are provided to supply power to single or plural moving devices by simply making the moving device to approach a power transmission surface. CONSTITUTION: A plurality of primary coils(302,312,314,322,324,326) induce an electromagnetic field. The primary coils are two-directionally arranged on the power transmission surface. A driving circuit drives each primary coil. A main device includes a sensing unit which senses load impedance of each driving circuit, a unit for receiving a signal through a power transmission channel, and an AC or DC power source. A moving device includes secondary coils(300,310,320), a rectification circuit which generates DC, and a unit for transmitting a signal through a power transmission channel.

Description

            Devices and Methods for Non-contact Power Transmission

The present invention relates to an apparatus and method for effectively delivering power to a single or multiple mobile devices in a non-contact manner using electromagnetic induction electromotive force. In particular, the present invention relates to a method and an apparatus capable of transferring power to charge a battery of a mobile device.

Personal mobile devices, powered by rechargeable secondary batteries, such as cellular phones, notebook computers, and portable media players, are increasingly used. It is also common for a person to carry more than one of these devices. These mobile devices usually charge the built-in secondary battery through electrical contact. Since the electrical contacts are usually different for each mobile device, the use of multiple mobile devices requires the use of multiple charging devices for each mobile device at home or while traveling.

Due to the different shapes and sizes of the moving devices, it is not easy to unify electrical contacts. Uniform electrical contact limits the design of the mover. When the power is transmitted in a non-contact manner, a single charging device may be used to charge power in a variety of mobile devices, thereby recharging a secondary battery embedded in the mobile device.

Non-contact power transmission methods include magnetic field induction, electromagnetic resonance coupling, and radio wave (rf) transmission. Radio wave transmission methods are commercially available for RFID, toll cards, etc., and magnetic field induction methods are commercially available for electric shavers and electric toothbrushes. In the radio wave transmission method, it is difficult to separate the power mobile device from other foreign substances and transmit power only to the power mobile device, and the power that can be transmitted by the radio wave is restricted by law, so the radio wave transmission method is a mobile device such as a wireless telephone. It is difficult to use for charging purposes.

Magnetic field induction or electromagnetic resonance induction can effectively transfer power over very short distances. There are two types of vertical or horizontal magnetic field methods depending on the direction of the magnetic flux generating the magnetic field. 1A shows a horizontal magnetic field method and FIG. 1B shows a vertical magnetic field method.

An example of a non-contact power transmission device and method using a horizontal magnetic field method has been disclosed in US Pat. No. 6,906,495, International Patent Application WO 03/096512, and Korean Patent Application 10-2004-7018306. In the horizontal magnetic field method, a mobile device can transmit power regardless of a position and a direction on a power transmission surface, and can transfer power to a plurality of mobile devices. However, in the horizontal magnetic field method, it is difficult to selectively transmit power only to the mobile device when both the mobile device and the metallic foreign body exist on the power transmission surface at the same time. When power is delivered to a foreign material, unnecessary power is consumed and heat is generated in the foreign material. If a large amount of heat is generated in the foreign material, there is a danger of fire.

A vertical magnetic field non-contact power transmission device that arranges a plurality of primary coils horizontally and vertically and detects the presence of a portable device adjacent to the primary coil with RFID to transfer power only to the primary coil adjacent to the mobile device is US Patent 7,262,700 Published in the issue. As shown in FIG. 2, only four primary coils 26a, 26b, 26c, and 26d overlapping the secondary coil 25 of the mobile device are transferred to the other coils. It can deliver power only to mobile devices without delivering power. However, US Pat. No. 7,262,700 does not provide a solution for the partial overlap of the primary and secondary coils and the presence of two or more portable devices on the power delivery surface, depending on where the portable device is placed on the power delivery surface. Did not present.

Hatanaka et al. Have published a desk-shaped non-contact power transmission device and a power transmission method in which a plurality of primary coils are arranged in two dimensions [K. Hatanaka, F. Sato, H. Matsuki, S. Kikuchi, J. Murakami, M. Kawase, and T. Satoh, "Power Transmission of a Desk With a Cord-Free Power Supply", IEEE Transactions on Magnetics, Vol. 38, no. 5, pp 3329-3331 (2002)]. The device was able to energize multiple mobile devices by activating primary coils adjacent to the mobile device. Hatanaka et al. Activated the secondary coil of the mobile device to check the voltage induced in the primary coil to find the primary coils adjacent to the mobile device, and activated the primary coils thus found to transfer power to the mobile device. Since the secondary coil cannot be activated when the battery of the mobile device is completely discharged, this device and method cannot deliver power to the mobile device where the battery is fully discharged.

A communication method of a charging device capable of simultaneously charging a battery of several robots by electromagnetic inductive contactless method has been disclosed [M. Ryan and R. Coup, "An Universal, Inductively Coupled Battery Charger for Robot Power Supplies", Proceedings of the 2006 Australasian Conference on Robotics & Automation. In this device and method, signals can be transmitted in both directions to a power supply channel, so that each robot's battery status can be determined and a voltage and current suitable for charging each robot's battery can be provided. However, Ryan and Coop did not explain the size and placement of the primary and secondary coils for electromagnetic inductive power transfer. Since the robot can change its position and posture itself, it is possible to spatially align the fixed primary coil and the secondary coil of the robot, but a mobile device such as a mobile phone cannot move and align itself.

It is an object of the present invention to provide a non-contact power delivery device and method for efficiently delivering power to a mobile device regardless of the relative position and orientation of the mobile device and the power delivery surface.

Another object of the present invention is to provide a non-contact power transmission device and method capable of delivering power to a mobile device regardless of the energy storage state of the mobile device.

Another object of the present invention is to provide a non-contact power transmission device and method for distinguishing between a mobile device to transfer power and a metallic foreign material to transmit power to the mobile device, but does not transmit power to the foreign material.

It is still another object of the present invention to provide a method and apparatus for contactless power transfer, each capable of controlling power delivered to a plurality of mobile devices adjacent to a power transfer surface.

Another object of the present invention is to provide a non-contact power transmission device and method for minimizing the number and weight of parts of a mobile device.

In order to achieve the above object, the system of the present invention comprises a main device having a plurality of primary coils arranged in two dimensions and a moving device having a secondary coil. No matter how the mobile device is placed on the power transfer surface, the secondary coil constitutes the secondary coil of the mobile device in such a size that it can fully overlap with at least one primary coil. Only one primary coil overlapping the secondary coil is activated to transfer power to the mobile device. By using a magnetic field induction signal that transmits power and a modulated signal without using a separate communication channel, the presence of the mobile device is sensed to control the power delivered to the mobile device, and does not transmit power to the foreign matter.

The mobile device may simply be in close proximity to the power delivery surface to power single or multiple mobile devices or to charge the mobile device's battery. Power can be efficiently delivered to a plurality of mobile devices regardless of their position and orientation on the mobile device and the power delivery surface. It is possible to control the power delivered to each mobile device while minimizing the weight of the mobile device and not to deliver foreign materials. The number of primary coils and drive circuits in the main unit can be minimized.

To deliver power to a mobile device without having to align the mobile device in a specific position or direction on the power delivery surface, it must be able to deliver power even if the primary and secondary coils are not aligned. In order to reduce the size and weight of the moving device, it is preferable to have only one secondary coil in the moving device. In order to reduce the standby power of the main unit, it is preferable to activate only the primary coil adjacent to the mobile unit to transfer power to the mobile unit. In the present invention, by activating a primary coil that can most effectively transfer power to the secondary coil of the mobile device in the main device arranged in a plurality of primary coils in two dimensions to minimize the standby power of the main device to prevent power loss Provided are an apparatus and method for effectively delivering power to a mobile device.

If the primary coil and the secondary coil are configured in the same size, the power transmission efficiency is high when the primary coil and the secondary coil are aligned, but the power transmission efficiency is greatly decreased when only a part of the primary coil and the secondary coil are not aligned. In order to transfer power efficiently, a secondary coil having a larger size than the primary coil is used. When only one primary coil is activated, the strength of the magnetic field decreases as the distance from the primary coil increases, so that the power transfer efficiency decreases when the size of the secondary coil is much larger than that of the primary coil. The primary coil and secondary coil are as similar in size as possible and the more they overlap, the better the power transmission efficiency. Select the size of the secondary coil so that when there are two or more primary coils that almost completely overlap with the secondary coil when the primary coil is placed close to the mobile device with the secondary coil on a two-dimensionally arranged power transfer surface. . To improve power transfer efficiency, the secondary coil is fixed to the mover so that it is generally parallel to the power transfer surface. When the power delivery surface is generally horizontal and the mobile device is placed on the power delivery surface, the secondary coil is secured to the mobile device so that the mobile device is parallel to the side in contact with the power delivery surface.

If you use a circular primary coil and a secondary coil, and the primary device with the primary coil placed as close as possible in two dimensions, the outer diameter of the secondary coil is approximately 2.25 (= 1 + 2 / SQRT ( 3)) You can double it. As shown in FIG. 3, circular primary coils densely arranged in two dimensions and secondary coils having an outer diameter of 2.25 times higher than the primary coils may be overlapped in three ways. If there is only one primary coil intimately overlapping with the first secondary coil 300, the primary coil 302 has a better power transfer efficiency than the other primary coils around it. Only by activating the power is delivered to the secondary coil (301). If there are two primary coils that completely overlap with the secondary coils as in the second case of FIG. 3, the two primary coils 312 and 314 activate a primary coil with better power transfer efficiency to transfer power. do. When there are three primary coils that completely overlap with the secondary coil as in the third case of FIG. 3, only one of the three primary coils 322, 324, and 326 is activated to transfer power.

It is also possible to configure the power transfer surface by arranging the primary coils in a square symmetry as shown in FIG. However, as shown in FIG. 3, it is advantageous to arrange the primary coils in triangular symmetry to make the sizes of the primary coil and the secondary coil more similar, which is advantageous in increasing power transmission efficiency.

The shape of the primary and secondary coils does not necessarily have to be circular. 4 shows an example in which a primary coil and a secondary coil of rectangular, hexagonal, and octagonal shapes are used. When the size of the square secondary coil is approximately 2.47 (= 7 X SQRT (2) / 4) times the size of the square primary coil, the square secondary coil is placed on the power transmission surface where the square primary coil is arranged closely. There is at least one primary coil that overlaps completely regardless of position (FIG. 5A). When the size of the regular hexagonal secondary coil is approximately 2.31 (= 4 / SQRT (3)) times the size of the regular hexagonal primary coil, the hexagonal secondary coil is placed in the direction and position where the regular hexagonal secondary coil is placed on the power transmission surface where the primary hexagonal coil is densely arranged. Regardless, there is at least one primary coil that overlaps completely (FIG. 5B). When the primary and secondary coils are circular or regular polygons, the size of the secondary coil is about 2.25 to 2.47 times larger than that of the primary coil, so that the primary coil completely overlaps with the secondary coil without the alignment of the moving device with the secondary coil. Is present (FIG. 5C).

In addition to round, square, hexagonal, and octagonal shapes, primary and secondary coils of other shapes may be used, or the primary and secondary coils may not be the same shape. The primary coil and the secondary coil may be manufactured in various forms. Coils wound around wires of a certain size may be used, or coils formed in a spiral pattern on a printed circuit board may be used. Implementing a secondary coil in a spiral pattern on one layer of a printed circuit board is advantageous to reduce the weight and volume of the mover.

Resonant frequencies of several MHz to several MHz can be used for magnetic field induction or electromagnetic induction between the primary and secondary coils.

In order to prevent unnecessary power loss, it is most desirable to cut off the power to the primary coil other than the primary coil selected adjacent to the mobile device. In addition, foreign matter may be placed on the power delivery surface instead of the mobile device to normally receive power. Metallic foreign materials, especially those with high resistance or ferromagnetic material, such as thin plates, may have a large eddy current that can be heated to high temperatures, so it is necessary to deliver power only to normal mobile devices and not to foreign materials.

Whether there is a load absorbing power around the primary coil can be detected by a change in the load impedance of the driving circuit inducing the electromagnetic field in the primary coil. The load impedance of the drive circuit is minimal when there are no moving devices or foreign matter absorbing power around the primary coil. The presence of a moving device or foreign material that absorbs power around the primary coil increases the load impedance of the drive circuit. Instead of measuring the load impedance directly, other values that increase as the load impedance increases and decrease as the load impedance decreases may be examined to detect the presence of moving devices or foreign objects around the primary coil. Checking the load impedance below includes checking for other values that change with the load impedance.

Any known method of measuring load impedance can be used. LLC circuits are known that can convert power using magnetic field induction or electromagnetic resonance with small volume and high efficiency. The magnitude of the load can be determined by detecting a change in phase difference in the LLC circuit. This is well illustrated in the annex to Yang's doctoral dissertation at Virginia Polytechnic University [Bo Yang "Topology investigation of front end DC / DC converter for distributed power system", Virginia Polytechnic Institute, Ph.D. Dissertation (2003) http://www.scientificcommons.org/7766879]. Since Figure 7 showing LLC resonant power conversion circuit in Fig. 8a, 8b, 8c and Figure 9a, changing the phase of the voltage applied to the Cr according to the load, as shown in 9b to measure the phase of the V _Cr the size of the load impedance Able to know.

In the arrangement of the primary coils shown in FIG. 3, each primary coil may be activated for a while and the load impedance may be inspected to determine whether there is an object absorbing power adjacent to the primary coil. Activating the primary coil only for a short enough time does not significantly increase the temperature of the foreign matter even if it is in close proximity. If the load impedance is minimal, there are no objects absorbing power around it. The primary coils of the main unit are each examined in this way to determine whether there is an object absorbing power around each primary coil. Inspection of all primary coils of the main unit reveals where the mobile unit or power-absorbing debris is present at any location on the power delivery surface.

You can run this test by activating only one primary coil at a time, or you can activate multiple tests at a time. By inspecting multiple primary coils instead of one by one, you can reduce the time required for inspection. If the size of the secondary coil does not exceed three times that of the primary coil, the test is performed by simultaneously activating the primary coils spaced two spaces apart, as shown in FIGS. 9A, 9B, 9C, 9D, 9E, 9F, 9G, 9H, 9i By proceeding, all primary coils can be inspected for nine times the time of inspecting one primary coil. Even when the primary coils are arranged in a square symmetry as shown in FIG. 4, all primary coils can be inspected for 9 times the time of inspecting one primary coil.

In the case of using the claim values in which the primary coils are arranged in hexagonal symmetry as shown in FIG. 3, the load impedance of each selected primary coil is compared with the load impedances of the surrounding six primary coils after checking the load impedance of all primary coils. do. In the case of using the claim values in which the primary coils are arranged in a square symmetry as shown in FIG. 4, the load impedance of each primary coil is compared with the load impedances of eight primary coils. If there is no primary coil with a higher load impedance around the selected primary coil, the selected primary coil is classified as 'active'. If there is a primary coil classified as 'active' around the selected primary coil, the selected primary coil is classified as 'inactive'. In no case should two adjacent primary coils be classified as 'active' at the same time. If there is a primary coil with a higher load impedance around the selected primary coil, then the primary coil with the higher load impedance will have higher power transfer efficiency and classify the selected primary coil as 'inactive'. Since the load impedance of the primary coil 302 is greatest near the first secondary coil 300 of FIG. 3, this is classified as 'active'. Near the second secondary coil 310 of FIG. 3, the load impedances of the two primary coils 312 and 314 will be significantly greater than the other primary coils around, and the primary coil with the higher load impedance will be ' Active '. If the load impedances of the two primary coils are the same, one of the two primary coils is classified as 'active' and the other primary coil is classified as 'inactive'. Near the third secondary coil 320 of FIG. 3, the load impedances of the three primary coils 322, 324, 326 will be significantly larger than the other primary coils around and the primary coil with the largest load impedance. Classify as 'active'. If three primary coils have the same load impedance, one of the three primary coils is classified as 'active' and the other two primary coils are classified as 'inactive'.

In this way, for each mobile device placed on the power delivery surface, the primary coil having the highest power delivery efficiency for that mobile device is classified as 'active'. If there are one mobile device, one primary coil is selected and classified as 'active'. If there are two mobile devices, two primary coils are selected and classified as 'active'.

The claim then attempts digital communication using a primary coil classified as active. The communication method using electric power induced by electromagnetic induction enables communication between the main device and the mobile device even when the battery of the mobile device is completely discharged. This approach was developed to both send and receive signals while inserting power into a device that remotely monitors body signals. [Z. Tang, B. Smith, J. H. Schild, and P. H. Peckham, "Data Transmission from an Implantable Biotelemeter by Load-Shift Keying Using Circuit Configuration Modulator", IEEE Transactions on Biomedical Engineering, Vol. 42, no. 5, pp 524-528 (1995); Y. Hu, J.-F. Gervais, and M. Sawan, "High power efficiency inductive link with full-duplex data communication", Proceeding of the 2002 9th International Conference on Electronics, Circuits and Systems, Vol. 1, pp 359-362. Amplitude shift keying (ASK), frequency shift keying (FSK), and phase shift keying to transmit digital signals in addition to frequency modulation (FM), which transmits analog signals. , PSK) can be used. Lian and Coop have implemented a very simple circuit, a load shift keying (LSK) method, which is a type of ASK. [M. Ryan and R. Coup "An Universal, Inductively Coupled Battery Charger for Robot Power Supplies", Proceedings of the 2006 Australasian Conference on Robotics & Automation.

In FIG. 10, a circuit diagram capable of simultaneous power transfer and communication is shown in a block diagram.

Receiving a prescribed recognition signal within a predetermined time, the assertion can tell that the mobile device is around the 'active' primary coil and information about the type of mobile device. You can use standardized recognition signals, such as RFID's ISO15693 communication protocol, or you can use your own recognition signals. The assertion may continue to communicate with the mobile device to obtain information such as the type, charge state and temperature of the mobile battery. If the mobile device is equipped with another sensor, the signal from that sensor may be transmitted to the host device. If the specified recognition signal is not received within a predetermined time, the primary coil is classified as 'inactive' and the power is cut off. The time to activate the primary coil for communication is short enough to prevent overheating even if there is a foreign object that absorbs power. The time to activate the primary coil classified as 'active' for digital communication may be longer than the time to activate the primary coil to check the load impedance of the primary coil.

Through the communication channel between the mobile device and the host device, the mobile device can transmit a voltage or current signal to the mobile device that is directed to the mobile device. The assertion can feed this signal through the primary coil to induce an appropriate voltage or current to the mobile device. Of course, this feedback adjustment can be made separately for each mobile device. Using this feedback circuit, the voltage converter for charging the battery can be omitted from the mobile device, thereby reducing the volume and weight of the mobile device.

The communication channel between the mobile unit and the host unit monitors the status in real time at the transmitter, which cuts off power delivery in case of full charge, overload, or abnormal temperature rise. This process is shown in a flow chart in FIG.

In addition, when the battery is being charged, the charge level of the battery may be recognized by the host device and displayed on the display of the host device. If necessary, the battery status of the mobile device can also be transferred from the main device to another computer.

New movers can be placed on the power delivery surface, or existing movers can be separated from the power delivery surface, so checking the load impedance of all primary coils is repeated at regular time intervals to 'activate' each primary coil. In this case, the 'inactive' state can be reclassified. Repeating the load impedance test with a time interval longer than necessary for the load impedance test has little effect on battery charge time. For example, if you use a 100 kHz resonant signal and you need 10 cycles of the resonant signal to measure the load impedance of one primary coil, then the load impedance of all primary coils must be at least 10 microseconds X 10 cycles X 9 times = 0.9 milliseconds. It can be measured in seconds. If it takes 10 milliseconds to measure the load impedance of all primary coils, classify 'active', 'inactive', and check for a recognition signal, and repeat this every 2 seconds, then the power will be effective for more than 99.5% of the time. Because it can be delivered, it has little effect on actual battery charge time.

Since the primary coils must be able to be activated separately, a separate driving circuit is required for each primary coil. Therefore, it is desirable to minimize the number of primary coils in order to simplify the construction of the entire circuit when constructing a constant area power transfer surface. If the size of the secondary coil of the mobile device is constant, the number of primary coils can be minimized when the size of the primary coil is maximum. Therefore, if the primary coil and the secondary coil are configured at the ratio of the size proposed in the present invention, the circuit configuration of the main apparatus can be simplified by minimizing the number of primary coils, and a separate power conversion circuit is not required for the mobile apparatus. The circuit configuration of the mobile device can be simplified while effectively delivering power in a non-contact manner.

1A and 1B illustrate a type of magnetic field induction scheme, in which FIG. 1A illustrates a horizontal magnetic flux distribution and FIG. 1B illustrates a vertical magnetic flux distribution.

2 is an example of a non-contact power transmission system of a vertical magnetic field method according to the prior art.

FIG. 3 illustrates three cases in which a circular primary coil and a secondary coil overlap in one embodiment of the present invention.

4 shows an arrangement of a primary coil in another embodiment of the present invention.

5a illustrates a case where a square primary coil and a secondary coil overlap.

5B illustrates a case where the primary coil and the secondary coil of the regular hexagon shape overlap each other.

Figure 5c shows a case where the primary coil and the secondary coil of the octagonal shape overlaps.

6 shows an LLC resonant transducer.

7A, 7B and 7C show the voltage and current of the circuit under heavy load, light load and very light load in the LLC circuit operating regions 1 and 3 of FIG. 6, respectively (see Bo Yang's doctoral dissertation appendix). The phase of the voltage across Cr changes according to the size of the load.

8A and 8B show the voltage and current of the circuit at full load and light load, respectively, in the LLC circuit operating region 2 of FIG. 6 (see Bo Yang's PhD Thesis appendix). The phase of the voltage across Cr changes according to the size of the load.

9a to 9i show the order of measuring the load impedance of all primary coils in the present invention.

10 is a flow chart illustrating the step of delivering power using an 'active' primary coil selected in accordance with an embodiment of the present invention.

11 is a block diagram of a circuit of a main device and a mobile device for power transmission and signal transmission according to an embodiment of the present invention.

Claims (9)

(i) a power transmission surface in which several primary coils capable of inducing electromagnetic fields are arranged in two dimensions, a driving circuit capable of driving each primary coil, means for sensing the load impedance of each driving circuit, A main unit having means for receiving a signal via a power transmission channel, and an alternating current or direct current power source; (ii) a secondary coil about 2 to 3 times larger than the primary coil, a rectifier circuit for rectifying electromagnetic waves induced in the secondary coil to generate direct current, and means for transmitting a signal through a power transmission channel. Consisting of at least one moving device, and when the moving device is located on or near the power transfer surface of the main device, power is transferred to the moving device by electromagnetic induction between the primary coil of the main device and the secondary coil of the moving device. Contactless power delivery system The system of claim 1, wherein the size of the secondary coil is about 2.1 to 2.6 times the primary coil. The system of claim 2, wherein the size of the secondary coil is about 2.1 to 2.4 times the primary coil. The system of claim 1, wherein the mobile device is equipped with a battery. The system according to any one of claims 1 to 3, which transmits the value read by the sensor of the mobile device to the main device. 4. A system according to claim 1, 3 or 3, which feeds back a signal transmitted from the mobile device to the main device to control the voltage or current induced in the mobile device. The method of claim 1, wherein the method for transmitting a signal is selected from the group consisting of ASK, FSK, PSK, and LSK. A power transmission surface in which several primary coils capable of inducing electromagnetic fields are arranged in two dimensions, a driving circuit capable of driving each primary coil, means for sensing a load impedance of each driving circuit, and a power transmission channel Means for receiving a signal, a primary device having an alternating current or direct current power source, and a secondary coil about 2 to 3 times larger than the primary coil, and rectifying electromagnetic waves induced in the secondary coil to generate direct current. When the mobile device is located on or near the power delivery surface of the host device using a non-contact power delivery system comprising a rectifying circuit and at least one mobile device having means for transmitting signals through the power delivery channel. In the non-contact power transfer method for transferring power to the mobile device by electromagnetic induction between the primary coil of the main device and the secondary coil of the mobile device (i) checking the load impedance of all primary coils; (ii) classifying the primary coil having a greater load impedance than the surroundings as 'active' by comparing the load impedance of each primary coil with the load impedance of the surrounding primary coil; (iii) activating a primary coil classified as 'active' and waiting for reception of a defined recognition signal; (iv) activating and supplying power to the primary coil on which the prescribed recognition signal has been received. Non-contact power delivery method comprising. 9. The method of claim 8, wherein the steps of claim 8 are repeated at regular time intervals.

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