JP5770556B2 - Wireless power transmission apparatus and relative position detection method - Google Patents

Description

  The present invention relates to a wireless power transmission device and a relative position detection method.

  2. Description of the Related Art In recent years, attention has been focused on a method of transmitting power in a contactless manner to electronic devices such as mobile phones, digital cameras, and notebook computers. Electric power is transmitted to a secondary coil built in a power receiver such as an electronic device by an alternating magnetic field generated from a primary coil built in the power transmitter.

  If the relative positions of the primary coil and the secondary coil are shifted, the coupling coefficient between the coils becomes small, so that desired power cannot be transmitted or the power transmission efficiency is lowered. In order to avoid this problem, the relative distance between the primary and secondary coils must be within a certain range. Therefore, it is necessary to provide means for detecting that the relative distance between the primary and secondary coils is within a predetermined range, and it is necessary to improve the accuracy of position detection.

  Patent Document 1 describes means for detecting the position of a secondary coil built in a power receiver such as an electronic device. A pulse signal is supplied to a position detection coil provided in the power transmitter, and an echo signal that is excited by this pulse signal and transmitted from the secondary coil to the position detection coil is received. And the position of a secondary coil is discriminate | determined by the receiving circuit which receives an echo signal. After determining the position of the secondary coil, the primary coil is brought close to the secondary coil, and power is transmitted from the primary coil to the secondary coil. The output of the secondary coil is rectified by a diode and then smoothed by a smoothing capacitor to obtain an output voltage Vd.

  Here, FIG. 1 shows an example of a timing chart in the conventional position detection operation. At time ta, the pulse signal Vpl is supplied to the position detection coil. When the pulse signal Vpl falls at time tb, the detection signal Vdt supplied to the receiving circuit gradually attenuates. At this time, since the voltage Vp is not applied to the primary coil, the output voltage Vd, which is the rectified output of the secondary coil, remains 0V.

JP 2009-247194 A

  In such a position detection method, when an element or circuit with a small impedance is incorporated in the subsequent stage of the rectifier circuit of the power receiver, the intensity of the echo signal for position detection is also reduced, and the detection signal supplied to the reception circuit Will also get smaller. Usually, in order to obtain DC power from AC power excited by the secondary coil, it is necessary to rectify the output of the secondary coil by a full-wave rectifier circuit or the like. A smoothing circuit is generally provided at the subsequent stage of the rectifier circuit. However, since the impedance of the smoothing circuit is low in terms of alternating current, the intensity of the echo signal is reduced. Therefore, in order to detect the exact position of the secondary coil, a device such as arranging the position detection coils in a matrix and comparing the echo signals, and a high-sensitivity detection circuit are required to extract the small echo signals. And the configuration becomes complicated.

  The present invention has been made in consideration of such problems, and an object thereof is to accurately detect the relative position between the primary and secondary coils without complicating the configuration of the detection coil and the detection circuit. .

  In order to achieve such an object, the present invention provides a primary coil that supplies electric power to a secondary coil by electromagnetic induction, an excitation coil that excites the secondary coil when a pulse signal is supplied, and the excitation A detection coil for detecting an alternating magnetic field generated from the secondary coil excited by the coil, and a control circuit for detecting a relative position between the primary coil and the secondary coil based on a detection signal excited by the detection coil And after the primary coil is driven for a short period of time, the pulse signal is supplied to the excitation coil to generate the alternating magnetic field.

  In order to achieve such an object, the present invention detects a primary coil that supplies electric power to the secondary coil by electromagnetic induction, and an alternating magnetic field generated from the secondary coil excited by the primary coil. A detection coil; and a control circuit that detects a relative position between the primary coil and the secondary coil based on a detection signal excited by the detection coil, and the primary coil is driven at a first drive frequency for a short period of time. Then, the primary coil is driven at a second drive frequency to generate the alternating magnetic field.

  Furthermore, in order to achieve the above object, the present invention is a method for detecting the relative position between a power transmitter and a power receiver, the smoothing capacitor for smoothing the output of a secondary coil provided in the power receiver. After that, the power transmitter excites the secondary coil provided in the power receiver, detects an AC magnetic field generated from the excited secondary coil, and transmits the transmission based on the detected AC magnetic field. A relative position between the electric device and the electric power receiver is detected.

  According to the present invention, the relative position between the primary and secondary coils can be detected with high accuracy.

The figure which shows the timing chart in the conventional position detection operation 1 is a block diagram of a wireless power transmission device according to a first embodiment of the present invention. Schematic which shows the positional relationship of each coil in 1st Example of this invention. Timing chart showing an example of position detection operation in the first embodiment of the present invention Timing chart showing another example of position detecting operation in the first embodiment of the present invention Block diagram of a wireless power transmission apparatus in a second embodiment of the present invention Schematic which shows the positional relationship of each coil in 2nd Example of this invention. Timing chart showing an example of position detection operation in the second embodiment of the present invention Block diagram of a wireless power transmission apparatus in a third embodiment of the present invention Schematic which shows the positional relationship of each coil in 3rd Example of this invention. Timing chart showing an example of position detection operation in the third embodiment of the present invention

  Embodiments will be described below with reference to the drawings.

  FIG. 2 shows a block of the wireless power transmission apparatus in the first embodiment of the present invention. The power transmitter 10 includes a pulse generation circuit 11, an excitation coil 12, a detection circuit 13, a detection coil 14, a control circuit 15, a smoothing capacitor 16, a drive circuit 17, a primary capacitor 18, and a primary coil 19. The power receiver 20 includes a secondary coil 21, a secondary capacitor 22, a detection capacitor 23, a rectifier circuit 24, a smoothing capacitor 25, an impedance element 26, a control circuit 27, a switch 28, and a load 29.

  First, the configuration of the power transmitter 10 will be described. The drive circuit 17 is supplied with an input voltage Vin from a DC power source DC. The operation of the drive circuit 17 is controlled by a control circuit 15 constituted by a microcomputer as an example. A smoothing capacitor 16 is connected to the input end of the drive circuit 17, and a primary coil 19 and a primary capacitor 18 are connected in series to the output end of the drive circuit 17. The drive circuit 17 supplies AC power to the primary coil 19 and the primary capacitor 18. As an example, the drive circuit 17 is configured by a full bridge circuit, a half bridge circuit, or the like. A pulse signal Vpl is supplied from the pulse generation circuit 11 to the excitation coil 12. The operation of the pulse generation circuit 11 is controlled by the control circuit 15. The detection signal Vdt excited by the detection coil 14 is supplied to the detection circuit 13. As an example, the detection circuit 13 shapes the detection signal Vdt with an amplifier circuit or the like, and supplies the obtained output signal to the control circuit 15. The control circuit 15 obtains the relative distance between the primary and secondary coils based on the output signal supplied from the detection circuit 13. The control circuit 15 can notify the user of information on the relative distance based on the obtained relative distance. For example, the control circuit 15 can notify the user of the relative distance between the primary and secondary coils by controlling elements that generate light, sound, vibration, and the like provided in the power transmitter 10.

  Next, the configuration of the power receiver 20 will be described. The secondary coil 21 receives power from the primary coil 19 by electromagnetic induction. A detection capacitor 23 is connected to both ends of the secondary coil 21 via a secondary capacitor 22. The voltage applied to the detection capacitor 23 is rectified by the rectifier circuit 24. A smoothing capacitor 25, an impedance element 26, and a control circuit 27 are connected in parallel to the output terminal of the rectifier circuit 24. The smoothing capacitor 25 removes a ripple of the output voltage Vd. The impedance element 26 indicates an element such as a voltage regulator provided in the power receiver 20. A load 29 such as a secondary battery is connected to the output terminal of the rectifier circuit 24 via a switch 28. The operation of the impedance element 26 and the switch 28 provided in the power receiver 20 is controlled by a control circuit 27 configured by a microcomputer or the like as an example. The load 29 can be disconnected from the circuit of the power receiver 20 by the switch 28. When the power obtained by the secondary coil 21 is supplied to the load 29, the switch 28 is closed and the output voltage Vd is applied to the load 29.

  Hereinafter, the resonance frequency of the secondary LC resonance circuit composed of the secondary coil 21 and the secondary capacitor 22 is referred to as a secondary resonance frequency fs. The resonance frequency of the resonance circuit composed of the secondary coil 21, the secondary capacitor 22, and the detection capacitor 23 is defined as a detection resonance frequency fd.

  FIG. 3 is a schematic diagram showing the positional relationship among the primary coil 19, the excitation coil 12, the detection coil 14, and the secondary coil 21 in the first embodiment of the present invention. Each of the primary coil 19, the excitation coil 12, the detection coil 14, and the secondary coil 21 has a flat and thin structure. The primary coil 19 and the secondary coil 21 are arranged to face each other. The primary coil 19, the excitation coil 12, and the detection coil 14 are arranged on substantially the same plane, and are arranged so that the central axes of the coils substantially coincide with each other.

Next, the detection operation of the relative distance between the primary coil 19 and the secondary coil 21 will be specifically described. FIG. 4 is a timing chart showing an example of the position detection operation in the first embodiment of the present invention. Note that when performing position detection, the switch 28 provided in the power receiver 20 is opened.
At time t0, supply of the voltage Vp to the primary coil 19 is started. Then, electric power is transmitted from the primary coil 19 to the secondary coil 21, and charging of the smoothing capacitor 25 connected to the output terminal of the rectifier circuit 24 is started. Then, the output voltage Vd gradually increases.
At time t1, voltage supply to the primary coil 19 is stopped. Then, the electric charge accumulated in the smoothing capacitor 25 is slowly discharged by the impedance element 26 and the like. Therefore, the output voltage Vd gradually decreases.
At time t2, a single pulse signal Vpl having a width of 400 ns is supplied to the excitation coil 12. Then, a resonance circuit composed of the secondary coil 21, the secondary capacitor 22, and the detection capacitor 23 is excited. A current that vibrates at the resonance frequency fd for detection flows through the resonance circuit, and an alternating magnetic field is generated around the secondary coil 21. This AC magnetic field is picked up by the detection coil 14 by electromagnetic induction and causes the detection coil 14 to generate a detection signal Vdt as an echo signal returned from the power receiver 20.
At time t3, the pulse signal Vpl falls. Then, the detection signal Vdt is gradually attenuated while freely vibrating. The detection signal Vdt generated at this time increases as the distance between the primary coil 19 and the secondary coil 21 decreases, and decreases as the distance between the primary coil 19 and the secondary coil 21 increases. The detection circuit 13 generates an output signal whose waveform is shaped in proportion to the intensity of the detection signal Vdt at this time. The control circuit 15 obtains the relative distance between the primary coil 19 and the secondary coil 21 based on the output signal supplied from the detection circuit 13. In addition, the control circuit 15 notifies the user of the result of the obtained relative distance with light, sound, vibration, or the like.

  When the pulse signal Vpl is supplied to the excitation coil 12, a current that freely vibrates in the secondary coil 21 is excited. When this excitation energy is absorbed by the smoothing capacitor 25 through the rectifier circuit 24, the current flowing through the resonance circuit is quickly attenuated. Then, the echo signal picked up by the detection coil 14 also becomes small, and the accuracy of detecting the relative distance between the primary and secondary coils is deteriorated. As described above, by supplying the pulse signal Vpl to the excitation coil 12 after charging the smoothing capacitor 25 in advance, the excitation energy can be prevented from being absorbed and attenuated by the smoothing capacitor 25. Therefore, when the pulse signal Vpl is supplied to the excitation coil 12, the alternating magnetic field generated in the secondary coil 21 is strengthened. Therefore, the intensity of the detection signal Vdt picked up by the detection coil 14 can be increased. Thereby, the relative distance between the primary coil 19 and the secondary coil 21 can be detected with high accuracy. Thus, in the present embodiment, the relative distance between the primary and secondary coils can be obtained with high accuracy.

  Note that it is preferable to perform control so that the switch element in the drive circuit 17 is opened at the time of detecting the relative distance between the primary coil 19 and the secondary coil 21. That is, when supplying the pulse signal Vpl, the primary capacitor 18 and the primary coil 19 are prevented from forming a closed loop. This is to prevent an induced current from flowing through the primary coil 19 according to the pulse signal Vpl. When an induced current flows through the primary coil 19, an alternating magnetic field is generated around the primary coil 19. Then, together with the alternating magnetic field generated from the secondary coil 21, the alternating magnetic field generated from the primary coil 19 is picked up by the detection coil 14, and this is superimposed on the detection signal Vdt as noise. In this way, during the relative distance detection operation, the switch element in the drive circuit 17 is controlled to be opened by the control circuit 15 in order to prevent an AC magnetic field from being generated from the primary coil 19.

As an example, the period from time t0 to time t1 when the primary coil 19 is driven is 3 ms here. The longer this period is, the more the output voltage Vd, that is, the amount of charge accumulated in the smoothing capacitor 25 increases. Then, the period in which the supply of the pulse signal Vpl is started after the driving of the primary coil 19 is stopped, that is, the period from the time t1 to the time t2 is set to 1 ms, and the time t2 to the time t3, which is the pulse width of the pulse signal Vpl. The period up to 400 ns. When the driving of the primary coil 19 is stopped, the electric charge accumulated in the smoothing capacitor 25 is gradually discharged, but the supply of the pulse signal Vpl may be started while the output voltage Vd is high. Further, when all the switch elements in the drive circuit 17 are turned off at time t1 and the driving of the primary coil 19 is stopped, a regenerative current flows through the primary coil 19 for a short period. If the supply of the pulse signal Vpl is started at the same time as the driving of the primary coil 19 is stopped, the regenerative current may cause noise to be superimposed on the detection signal Vdt picked up by the detection coil 14. Therefore, the driving of the primary coil 19 is stopped, and the supply of the pulse signal Vpl is started after the regenerative current flowing through the primary coil 19 converges.
Further, the detection signal Vdt picked up by the detection coil 14 as an echo signal can be increased as the output voltage Vd at the time of supplying the pulse signal Vpl increases. Therefore, it is preferable to charge until the charge accumulated in the smoothing capacitor 25 is saturated.
Further, the pulse width of the pulse signal Vpl is determined according to the detection resonance frequency fd. When the pulse width is short, the echo signal intensity decreases, and when the pulse width is longer than a certain value, the echo signal intensity is saturated. The pulse width of the pulse signal Vpl is preferably about half the wavelength of the detection resonance frequency fd. For example, if the detection resonance frequency fd is 1 MHz, it is preferable to use a single pulse of about 400 ns.

FIG. 5 is a timing chart showing another example of the position detecting operation in the first embodiment of the present invention. The operation from time t0 to t3 is the same as the example of the position detection operation described above. After the elapse of time t3, the detection signal Vdt gradually attenuates and the detection signal Vdt converges. Here, it is assumed that the power receiver 20 is moved so that the relative distance between the primary and secondary coils approaches at time t4.
At time t4, the supply of the voltage Vp to the primary coil 19 is started as at time t0. Then, charging of the smoothing capacitor 25 is started, and the output voltage Vd gradually increases.
At time t5, the voltage supply to the primary coil 19 is stopped as in the case of time t1.
At time t6, a single pulse signal Vpl having a width of 400 ns is supplied to the excitation coil 12 as at time t2. Then, a resonance circuit composed of the secondary coil 21, the secondary capacitor 22, and the detection capacitor 23 is excited. A current that vibrates at the resonance frequency fd for detection flows through the resonance circuit, and an alternating magnetic field is generated around the secondary coil 21. This AC magnetic field is picked up by the detection coil 14 by electromagnetic induction and causes the detection coil 14 to generate a detection signal Vdt as an echo signal returned from the power receiver 20.
At time t7, the pulse signal Vpl falls in the same manner as at time t3. Then, the detection signal Vdt is gradually attenuated while freely vibrating. The detection circuit 13 generates an output signal whose waveform is shaped in proportion to the intensity of the detection signal Vdt at this time. The control circuit 15 obtains the relative distance between the primary coil 19 and the secondary coil 21 based on the output signal supplied from the detection circuit 13. The intensity of the detection signal Vdt generated after time t7 is greater than the intensity of the detection signal Vdt generated after time t3. This is because the power receiver 20 is moved so that the relative distance between the primary and secondary coils approaches at time t4.

As described above, the smoothing capacitor 25 may be charged intermittently, and the pulse signal Vpl may be supplied to the excitation coil 12 after each charging operation to detect the relative distance between the primary and secondary coils. Thereby, whenever the pulse signal Vpl is sent by the excitation coil, the relative distance between the primary and secondary coils can be detected, and the movement of the power receiver 20 with respect to the power transmitter 10 can be recognized. As described above, when the intensity of the detection signal Vdt increases, it can be recognized that the relative distance between the primary coil and the secondary coil is close. On the other hand, when the intensity of the detection signal Vdt becomes small, it can be recognized that the relative distance between the primary and secondary coils has increased. When the intensity of the detection signal Vdt does not change, it can be recognized that the relative distance between the primary and secondary coils does not change. When the detection signal Vdt is not detected, it can be recognized that the power receiver 20 is not present or that the secondary coil 21 is sufficiently away from the primary coil 19. Further, the power consumption can be reduced by extending the interval for supplying the voltage to the primary coil 19, that is, the interval from time t0 to t4.
By supplying the pulse to the excitation coil 12 after charging the smoothing capacitor 25 in advance, the intensity of the detection signal Vdt picked up by the detection coil 14 is increased. Therefore, when the relative distance between the primary and secondary coils is continuously detected as described above, a minute change in the relative distance of the power receiver 20 with respect to the power transmitter 10 can be recognized.

In this embodiment, the pulse signal Vpl is supplied after a predetermined time has elapsed since the primary coil 19 is driven, and the detection signal Vdt is picked up. The operation of detecting the relative distance between the primary and secondary coils based on the detection signal Vdt is repeated, but the present invention is not limited to such an operation. After the operation of driving the primary coil 19 and charging the smoothing capacitor 25 is performed once, an echo signal generated when the pulse signal Vpl is supplied is detected by the detection coil 14 and the relative relationship between the primary coil 19 and the secondary coil 21 is detected. The operation of obtaining the distance may be repeated a plurality of times. When the discharge time of the electric charge stored in the smoothing capacitor 25 is sufficiently longer than the relative distance detection operation, the operation may be performed in this way.
In addition, when a secondary battery is used as the load 29 and energy is stored in the secondary battery in advance, the switch 28 is closed instead of driving the primary coil 19 and the smoothing capacitor 25 is charged by the secondary battery. May be. Thereafter, the pulse signal Vpl is supplied after the switch 28 is opened, and the detection signal Vdt may be picked up by the detection coil 14 as an echo signal. By reducing the number of times the primary coil 19 is driven, power consumption can be reduced.

  FIG. 6 shows a block of a wireless power transmission apparatus in the second embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the site | part which has the same function as a 1st Example, and description is abbreviate | omitted. The power transmitter 30 detects a relative distance between the primary and secondary coils without using an excitation coil and a pulse generation circuit. The control circuit 15 is set so that the drive frequency of the primary coil 19 can be switched.

  FIG. 7 is a schematic diagram showing the positional relationship among the primary coil 19, the detection coil 14, and the secondary coil 21 in the second embodiment of the present invention. Each of the primary coil 19, the detection coil 14, and the secondary coil 21 has a flat and thin structure. The primary coil 19 and the secondary coil 21 are arranged to face each other. The primary coil 19 and the detection coil 14 are arranged on substantially the same plane, and are arranged so that the central axes of the coils substantially coincide with each other.

Next, the detection operation of the relative distance between the primary coil 19 and the secondary coil 21 will be specifically described. FIG. 8 is a timing chart showing an example of the position detection operation in the second embodiment of the present invention. Note that when performing position detection, the switch 28 provided in the power receiver 20 is opened.
At time t0, supply of the voltage Vp to the primary coil 19 is started. Then, electric power is transmitted from the primary coil 19 to the secondary coil 21, and charging of the smoothing capacitor 25 connected to the output terminal of the rectifier circuit 24 is started. Then, the output voltage Vd gradually increases. At this time, the primary coil 19 is driven at a frequency relatively close to the secondary resonance frequency fs.
At time t1, voltage supply to the primary coil 19 is stopped. Then, the electric charge accumulated in the smoothing capacitor 25 is slowly discharged by the impedance element 26 and the like. Therefore, the output voltage Vd gradually decreases.
At time t2, voltage supply to the primary coil 19 is started again. At this time, the primary coil 19 is driven at a frequency close to the detection resonance frequency fd. Then, a resonance circuit composed of the secondary coil 21, the secondary capacitor 22, and the detection capacitor 23 is excited. A current that vibrates at the resonance frequency fd for detection flows through the resonance circuit, and an alternating magnetic field is generated around the secondary coil 21. This AC magnetic field is picked up by the detection coil 14 by electromagnetic induction and causes the detection coil 14 to generate a detection signal Vdt as an echo signal returned from the power receiver 20.
At time t3, the voltage supply to the primary coil 19 is stopped. Then, the detection signal Vdt is gradually attenuated while freely vibrating. The detection circuit 13 generates an output signal whose waveform is shaped in proportion to the intensity of the detection signal Vdt at this time. The control circuit 15 obtains the relative distance between the primary coil 19 and the secondary coil 21 based on the output signal of the detection circuit 13. The detection signal Vdt increases as the distance between the primary coil 19 and the secondary coil 21 decreases, and the detection signal Vdt decreases as the distance between the primary coil 19 and the secondary coil 21 increases.
At time t4, the supply of the voltage Vp to the primary coil 19 is started as at time t0. Then, charging of the smoothing capacitor 25 is started, and the output voltage Vd gradually increases. At this time, the primary coil 19 is driven at a frequency relatively close to the secondary resonance frequency fs.
At time t5, the voltage supply to the primary coil 19 is stopped as in the case of time t1.
At time t6, voltage supply to the primary coil 19 is started in the same manner as at time t2. At this time, the primary coil 19 is driven at a frequency close to the detection resonance frequency fd. Then, a resonance circuit composed of the secondary coil 21, the secondary capacitor 22, and the detection capacitor 23 is excited. A current that vibrates at the resonance frequency fd for detection flows through the resonance circuit, and an alternating magnetic field is generated around the secondary coil 21. This AC magnetic field is picked up by the detection coil 14 by electromagnetic induction and causes the detection coil 14 to generate a detection signal Vdt as an echo signal returned from the power receiver 20.
At time t7, the voltage supply to the primary coil 19 is stopped in the same manner as at time t3. Then, the detection signal Vdt is gradually attenuated while freely vibrating. The relative distance between the primary and secondary coils is obtained from the intensity of the detection signal Vdt generated after times t3 and t7.

  Here, the operation of the detection circuit 13 will be described. The detection circuit 13 supplies an output signal having a waveform shaped in proportion to the intensity of the detection signal Vdt to the control circuit 15. As an example, the detection circuit 13 amplifies the detection signal Vdt with an operational amplifier to obtain an amplified signal. The obtained amplified signal is smoothed and then compared with a reference voltage by a comparator to generate an output signal having a pulse width corresponding to the intensity of the detection signal Vdt. The control circuit 15 can determine the relative distance between the primary and secondary coils from the pulse width of the output signal. Alternatively, the detection circuit 13 may simply amplify the detection signal Vdt, and the control circuit 15 may obtain the relative distance between the primary and secondary coils from the maximum value of the waveform of the amplified signal. If the control circuit 15 can evaluate the intensity of the detection signal Vdt, the detection circuit 13 may shape the detection signal Vdt in any way.

  Thus, the echo signal may be generated by driving the primary coil 19. Therefore, when precharging the smoothing capacitor 25, the primary coil 19 is driven at a frequency relatively close to the secondary resonance frequency fs. Further, when exciting a resonance circuit composed of the secondary coil 21, the secondary capacitor 22, and the detection capacitor 23, the primary coil 19 is driven at a frequency close to the detection resonance frequency fd. When generating an echo signal, the primary coil 19 may be continuously driven by alternating current, or may be driven so that a single pulse is generated. By operating in this way, the excitation coil and the pulse generation circuit can be omitted, the configuration can be simplified, and the cost can be reduced.

  FIG. 9 shows a block of a wireless power transmission apparatus according to the third embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the site | part which has the same function as a 1st Example, and description is abbreviate | omitted. The power transmitter 40 is provided with four detection coils to detect one or both of the relative distance between the primary and secondary coils and the direction of displacement. Detection signals Vdt1, Vdt2, Vdt3, and Vdt4 excited by the detection coils 41, 42, 43, and 44 are supplied to the detection circuit 45, respectively. The detection circuit 45 generates an output signal whose waveform is shaped in proportion to the intensity of the detection signals Vdt1, Vdt2, Vdt3, and Vdt4. The control circuit 15 compares and calculates the output result of the detection circuit 45 to determine the relative distance between the primary and secondary coils and the position shift direction. The result of the obtained relative distance and positional deviation direction can be guided to the appropriate position by notifying the user of the position of the power receiver by light, sound, vibration, or the like.

  FIG. 10 is a schematic diagram showing the positional relationship among the primary coil 19, the excitation coil 12, the detection coils 41, 42, 43, 44, and the secondary coil 21 in the third embodiment of the present invention. The primary coil 19, the excitation coil 12, the detection coils 41, 42, 43, 44 and the secondary coil 21 each have a flat and thin structure. The primary coil 19 and the secondary coil 21 are arranged to face each other. The primary coil 19, the excitation coil 12, and the detection coils 41, 42, 43, and 44 are arranged on substantially the same plane. Further, the central axes of the primary coil 19 and the excitation coil 12 are arranged so as to substantially coincide. The distances between the central axes of the detection coils 41, 42, 43, and 44 and the central axes of the primary coil 19 and the excitation coil 12 are substantially the same. The distances between adjacent detection coils, that is, the detection coil 41, the detection coil 42, and the detection coil 44, and the distance between the central axes of the detection coil 43, the detection coil 42, and the detection coil 44 are also substantially the same. In other words, the detection coils are arranged so that the line connecting the central axes of the opposing detection coils 41 and 43 and the line connecting the central axes of the opposing detection coils 42 and 44 are orthogonal to each other. Note that each of the detection coils 41, 42, 43, and 44 may be disposed so as to partially overlap each other in the direction perpendicular to the winding surface.

Next, the relative distance between the primary coil 19 and the secondary coil 21 and the operation for detecting the displacement direction will be specifically described. FIG. 11 is a timing chart showing an example of the position detection operation in the third embodiment of the present invention. Note that when performing position detection, the switch 28 provided in the power receiver 20 is opened.
At time t0, supply of the voltage Vp to the primary coil 19 is started. Then, electric power is transmitted from the primary coil 19 to the secondary coil 21, and charging of the smoothing capacitor 25 connected to the output terminal of the rectifier circuit 24 is started. Then, the output voltage Vd gradually increases.
At time t1, voltage supply to the primary coil 19 is stopped. Then, the electric charge accumulated in the smoothing capacitor 25 is slowly discharged by the impedance element 26 and the like. Therefore, the output voltage Vd gradually decreases.
At time t2, a single pulse signal Vpl having a width of 400 ns is supplied to the excitation coil 12. Then, a resonance circuit composed of the secondary coil 21, the secondary capacitor 22, and the detection capacitor 23 is excited. A current that vibrates at the resonance frequency fd for detection flows through the resonance circuit, and an alternating magnetic field is generated around the secondary coil 21. The AC magnetic field is picked up by the detection coils 41, 42, 43, and 44 by electromagnetic induction, and detection signals Vdt1, Vdt2, Vdt3, and Vdt4 are generated in the detection coils 41, 42, 43, and 44, respectively.
At time t3, the pulse signal Vpl falls. Then, the detection signals Vdt1, Vdt2, Vdt3, and Vdt4 are gradually attenuated while freely vibrating. The detection circuit 45 generates an output signal whose waveform is shaped in proportion to the intensity of the detection signal Vdt at this time. The control circuit 15 compares and calculates the output signal of the detection circuit 13 to obtain the relative distance between the primary and secondary coils and the position shift direction.

  For example, when the intensity of each detection signal Vdt is equal, the distance between the secondary coil 21 and each detection coil 41, 42, 43, 44 is equal. That is, it can be recognized that the central axes of the primary coil 19 and the secondary coil 21 coincide. Further, when the intensity of the detection signal Vdt2 is relatively larger than the other detection signals, it can be recognized that the secondary coil 21 is located in the direction of the detection signal coil 42 from the central axis of the primary coil 19. As another example, as shown in FIG. 11, the intensities of the detection signals Vdt1 and Vdt4 are equal, the intensities of the detection signals Vdt2 and Vdt3 are equal, and the intensities of the detection signals Vdt1 and Vdt4 are intensities of the detection signals Vdt2 and Vdt3. Let it be larger. In such a case, it can be recognized that the secondary coil 21 is located in the direction between the detection signal coils 41 and 44 from the central axis of the primary coil 19.

  Thus, in order to detect the misalignment direction between the primary and secondary coils, it is necessary to use a plurality of detection coils and to compare the detection signal strengths generated in the detection coils. By supplying the pulse to the excitation coil 12 after charging the smoothing capacitor 25 in advance, the intensity of the detection signals Vdt1, Vdt2, Vdt3, and Vdt4 picked up by the detection coils 41, 42, 43, and 44 is increased. By combining such an echo signal detection sensitivity improvement means and a plurality of detection coils with a position shift direction detection means, the detection accuracy in the position shift direction between the primary and secondary coils can be improved. Of course, the relative distance between the primary and secondary coils may be obtained from the intensities of the detection signals Vdt1, Vdt2, Vdt3, and Vdt4. It is also possible to obtain the relative position between the primary and secondary coils by determining both the relative distance between the primary and secondary coils and the direction of displacement.

  In this embodiment, four detection coils 41, 42, 43, 44 are used, and the center axes of the detection coils are arranged so as to be substantially equidistant from the center axis of the primary coil 19. Arranged so that the axis is located at each vertex of the square. However, this is only an example. Using three detection coils, arrange so that the center axis of each detection coil is substantially equidistant from the center axis of the primary coil 19, and so that the center axis of each detection coil is located at each vertex of the equilateral triangle May be. Further, two detection coils are used so that the center axis of each detection coil is substantially equidistant from the center axis of the primary coil 19, and the center axis of each detection coil and the center axis of the primary coil 19 are perpendicular to each other. May be arranged in a straight line. Similarly, the detection accuracy can be further increased by increasing the combination of the two detection coils described above and using a total of six or eight detection coils. In this embodiment, the relative distance between the primary and secondary coils and the direction of displacement can be detected. By using the detection results of the relative distance and the direction of displacement, the relative position between the primary and secondary coils can be detected.

  The above-described values such as the secondary resonance frequency fs, the detection resonance frequency fd, the charging period of the smoothing capacitor 25, and the pulse width of the pulse signal Vpl are merely examples. Of course, the present invention is not limited to such conditions. The present invention can be implemented in various modifications without departing from the spirit thereof, or by combining the embodiments.

10, 30, 40 Power transmitter 11 Pulse generation circuit 12 Excitation coil 13, 45 Detection circuit 14, 41, 42, 43, 44 Detection coil
DESCRIPTION OF SYMBOLS 15 Control circuit 16 Smoothing capacitor 17 Drive circuit 18 Primary capacitor 19 Primary coil 20 Power receiving device 21 Secondary coil 22 Secondary capacitor 23 Detection capacitor 24 Rectifier circuit 25 Smoothing capacitor 26 Impedance element 27 Control circuit 28 Switch 29 Load

Claims (6)

A primary coil that supplies electric power to the secondary coil connected to the smoothing capacitor by electromagnetic induction, an excitation coil that excites the secondary coil when a pulse signal is supplied, and the excitation coil that is excited by the excitation coil A detection coil for detecting an alternating magnetic field generated from the secondary coil, and a control circuit for detecting a relative position between the primary coil and the secondary coil based on a detection signal excited by the detection coil;
A wireless power transmission device, wherein the primary coil is driven in advance for a short period to charge the smoothing capacitor , and then the pulse signal is supplied to the excitation coil to generate the alternating magnetic field.   The wireless power transmission device according to claim 1, wherein when the pulse signal is supplied, a switch element in a drive circuit that drives the primary coil is opened. A primary coil that supplies power by electromagnetic induction to a secondary coil to which a smoothing capacitor is connected, a detection coil that detects an AC magnetic field generated from the secondary coil excited by the primary coil, and a detection coil A control circuit for detecting a relative position between the primary coil and the secondary coil based on the excited detection signal;
A wireless system comprising: first driving the primary coil at a first driving frequency for a short period to charge the smoothing capacitor; and driving the primary coil at a second driving frequency to generate the alternating magnetic field. Power transmission device.   4. The wireless power transmission device according to claim 1, wherein the AC magnetic field is generated after a predetermined period has elapsed after the primary coil is driven for a short period of time.   The wireless power transmission device according to any one of claims 1 to 4, wherein the primary coil is intermittently driven for a short period of time. The detection coil is composed of a plurality of detection coils arranged on substantially the same plane, and the distance between the central axis of each detection coil and the central axis of the primary coil is substantially the same,
6. The control circuit according to claim 1, wherein the control circuit detects one or both of a relative distance and a displacement direction between the primary coil and the secondary coil based on detection signals excited by the plurality of detection coils. The wireless power transmission device according to claim 1.

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