JP5770589B2 - 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.

  In recent years, electromagnetic induction type wireless power transmission devices for portable devices are becoming widespread. 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. The electric power transmitted to the secondary coil is supplied to a load such as a secondary battery through a rectifier circuit or the like. By simply placing the power receiver on the power transmitter, the secondary battery in the power receiver can be charged, and there is no need to plug in or unplug the power connector. Therefore, there are advantages such as excellent convenience, waterproofing, and dustproofing.

  In a general-purpose charger, the standby time is sufficiently longer than the charging operation time, so that even if the charging efficiency is high, the overall power efficiency is reduced when the standby power consumption is increased. Of course, standby power can be eliminated by providing a power switch and turning on the power only during charging. However, the main advantage of the wireless power transmission system is that charging can be started simply by placing the power receiver on the power transmitter. If a manual power switch is provided to reduce standby power, the convenience is impaired. Therefore, in the wireless power transmission device, it is necessary to always check whether the power receiver is placed on the power transmitter. Thus, in an actual wireless power transmission system, it is necessary to design a standby mode that always checks for the presence of a power receiver. Therefore, how to reduce standby power is an important issue.

  Patent Document 1 describes means for detecting at which position on the power transmitter the power receiver is placed by a plurality of position detection coils arranged in the X-axis and Y-axis directions. By supplying a position detection signal to the position detection coil, a secondary coil provided in the power receiver is excited. Then, an echo signal generated from the secondary coil is detected by the position detection coil. Each position detection coil is connected to a receiving circuit via a multiplexer. The multiplexer sequentially switches position detection coils connected to the receiving circuit. And based on the echo signal which a receiving circuit receives, a discrimination circuit discriminate | determines the position of a secondary coil.

  Here, FIG. 1 shows an example of a conventional position detection circuit. The plurality of detection coils 51, 52, 53, 54 are connected to the reception circuit 56 via the multiplexer 55. The output of the receiving circuit 56 is supplied to the calculation unit 57. The multiplexer 55 sequentially outputs echo signals detected by the detection coils 51, 52, 53, 54 to the reception circuit 56. The calculation unit 57 determines the position of the secondary coil based on the intensity of the echo signal supplied from the reception circuit 56.

JP 2010-263663 A

  However, in such a position detection method, it is necessary to switch the detection coil to be connected by the multiplexer 55 in order to determine the presence or absence of an echo signal in each of the detection coils 51, 52, 53 and 54. Therefore, the signals supplied from the detection coils 51, 52, 53, and 54 cannot be detected collectively. As a result, the sampling frequency increases, and standby power increases.

  The present invention has been made in consideration of such problems, and an object thereof is to reduce standby power without impairing the convenience of the wireless power transmission system.

  In order to achieve such an object, the present invention generates a primary coil that supplies electric power to a secondary coil by electromagnetic induction, an excitation coil that excites the secondary coil, and the excited secondary coil. A plurality of detection coils for detecting an alternating magnetic field; and a detection circuit for selectively outputting all or any detection signal excited by the plurality of detection coils to a control circuit. The period for exciting the secondary coil when a detection signal is output to the control circuit, and the secondary coil is excited when the detection circuit sequentially outputs one of the detection signals to the control circuit. It is characterized by being set longer than the period.

  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, the primary coil that excites the secondary coil, and the excited secondary coil. A plurality of detection coils for detecting an alternating magnetic field generated from the detection circuit, and a detection circuit for selectively outputting all or any of the detection signals excited by the plurality of detection coils to a control circuit. Indicates a period for exciting the secondary coil when all detection signals are output to the control circuit, and when the detection circuit sequentially outputs one of the detection signals to the control circuit, the secondary coil It is characterized in that it is set longer than the period of excitation.

  Furthermore, in order to achieve the above object, the present invention is a method for detecting a relative position between a power transmitter and a power receiver, and includes a first step of exciting a secondary coil provided in the power receiver. A second step of collectively detecting the alternating magnetic field generated from the secondary coil excited in the first step by a plurality of detection coils provided in the power transmitter; and the second step A third step of detecting whether the power receiver is disposed in the vicinity of the power transmitter based on the detected AC magnetic field; a fourth step of exciting the secondary coil; A fifth step of sequentially detecting the AC magnetic field generated from the secondary coil excited in the step by the plurality of detection coils; and the transmitter based on the AC magnetic field detected in the fifth step. And the A sixth step of detecting a relative position between the electric appliances, wherein the period for repeatedly exciting the secondary coil in the first step is set longer than the period for repeatedly exciting the secondary coil in the fourth step It is characterized by doing.

  According to the present invention, standby power can be reduced, and the overall power efficiency of the wireless power transmission device can be improved.

Block diagram of a conventional position detection circuit Block diagram of the wireless power transmission device of the present invention Schematic showing the positional relationship of each coil of the present invention Detection circuit for wireless power transmission device of the present invention Timing chart showing detection signal intensity detection operation of the present invention Timing chart in position detection mode of the present invention Timing chart in standby mode of the present invention Another example of the switching circuit of the wireless power transmission device of the present invention Block diagram of a power transmitter in the second embodiment of the present invention

  Embodiments will be described below with reference to the drawings.

  FIG. 2 shows a block diagram of the wireless power transmission apparatus of the present invention. The power transmitter 10 includes a DC power supply 11, a smoothing capacitor 12, a drive circuit 13, a primary resonant capacitor 14, a primary coil 15, a control circuit 16, a pulse generation circuit 17, an excitation coil 18, detection coils 21 to 24, and a detection circuit 25. . The power receiver 30 includes a secondary coil 31, a secondary resonance capacitor 32, a detection capacitor 33, a rectifier circuit 34, a smoothing capacitor 35, a switch 36, and a load 37.

  First, the configuration of the power transmitter 10 will be described. A DC voltage Vin is supplied from the DC power supply 11 to the drive circuit 13. A smoothing capacitor 12 is connected to the input end of the drive circuit 13, and a primary coil 15 and a primary resonant capacitor 14 are connected in series to the output end of the drive circuit 13. The drive circuit 13 supplies AC power to the primary coil 15 and the primary resonant capacitor 14. As an example, the drive circuit 13 is configured by a full bridge circuit, a half bridge circuit, or the like. A pulse signal Vp is supplied from the pulse generation circuit 17 to the excitation coil 18. The operations of the drive circuit 13 and the pulse generation circuit 17 are controlled by a control circuit 16 constituted by a microcomputer as an example. The detection signals Vs1 to Vs4 excited by the detection coils 21 to 24 are supplied to the detection circuit 25. The detection circuit 25 outputs a signal having a pulse width corresponding to the intensity of any of the detection signals Vs1 to Vs4 to the control circuit as an output signal Pos. Alternatively, the logical sum of signals having pulse widths corresponding to the intensities of the detection signals Vs1 to Vs4 is output to the control circuit as the output signal Pos. The operation of the detection circuit 25 is controlled by control signals S1 to S4 supplied from the control circuit 16.

  Next, the configuration of the power receiver 30 will be described. The secondary coil 31 receives power from the primary coil 15 by electromagnetic induction. A detection capacitor 33 is connected to both ends of the secondary coil 31 via a secondary resonance capacitor 32. The voltage applied to the detection capacitor 33 is rectified by the rectifier circuit 34. A smoothing capacitor 35 is connected to the output terminal of the rectifier circuit 34. The smoothing capacitor 35 removes ripples in the output voltage of the rectifier circuit 34. A load 37 such as a secondary battery is connected to the output terminal of the rectifier circuit 34 via a switch 36. The operation of the switch 36 is controlled by a control circuit (not shown) constituted by a microcomputer as an example. The load 37 can be disconnected from the circuit of the power receiver 30 by the switch 36. When the electric power obtained by the secondary coil 31 is supplied to the load 37, the switch 36 is closed and a voltage is applied to the load 37.

  The capacitance of the detection capacitor 33 is designed to be much smaller than the capacitance of the secondary resonance capacitor 32. Thereby, a resonator of the secondary resonance capacitor 32 and the secondary coil 31 is configured in a low load impedance state when the load is connected by the switch 36. On the other hand, in a high load impedance state when the load is interrupted by the switch 36, a resonator including the secondary coil 31, the secondary resonance capacitor 32, and the detection capacitor 33 is configured. That is, the power receiver 30 is a dual resonator. Hereinafter, the resonance frequency of the resonance circuit including the secondary coil 31, the secondary resonance capacitor 32, and the detection capacitor 33 is referred to as a detection resonance frequency fd.

  FIG. 3 is a schematic diagram showing the positional relationship among the primary coil 15, the excitation coil 18, the detection coils 21 to 24, and the secondary coil 31 of the present invention. The upper surface of the power transmitter 10 is substantially planar, and the power receiver 30 is placed on this surface. The primary coil 15, the excitation coil 18, and the detection coils 21 to 24 are built in the power transmitter 10. The primary coil 15, the excitation coil 18, the detection coils 21 to 24, and the secondary coil 31 each have a flat and thin structure. The upper surface of the power transmitter 10 and the winding surface of the primary coil 15 are arranged so as to be substantially parallel. Moreover, the winding surface of the primary coil 15 and the winding surface of the secondary coil 31 are arrange | positioned so that it may each oppose. The primary coil 15, the excitation coil 18, and the detection coils 21 to 24 are arranged on substantially the same plane, and the central axes of the primary coil 15 and the excitation coil 18 are arranged so as to substantially coincide with each other. The distances between the central axes of the detection coils 21 to 24 and the central axes of the primary coil 15 and the excitation coil 18 are substantially the same. The distances between adjacent detection coils, i.e., the detection coil 21, the detection coil 22, and the detection coil 24, and the distance between the central axes of the detection coil 23, the detection coil 22, and the detection coil 24 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 21 and 23 and the line connecting the central axes of the opposing detection coils 22 and 24 are orthogonal to each other. In addition, you may arrange | position each detection coil 21, 22, 23, 24 so that a part may mutually overlap in the orthogonal | vertical direction with a winding surface.

  Power transmission is performed by electromagnetic induction between the primary coil 15 and the secondary coil 31. The efficiency of power transmission varies depending on the relative positions of the primary coil 15 and the secondary coil 31. Generally, the winding surface of the primary coil 15 and the winding surface of the secondary coil 31 are arranged to face each other. It is known that the efficiency is higher as the relative position between the primary coil 15 and the secondary coil 31 is closer, and the efficiency is lower as the relative position is farther away. Therefore, it is necessary to arrange the secondary coil 31 at an appropriate position with respect to the primary coil 15 before performing power transmission.

  For detecting the relative position between the primary coil 15 and the secondary coil 31, the following method may be used. When a pulse signal Vp having a predetermined pulse width is supplied to the excitation coil 18, a current oscillating at the resonance frequency fd for detection flows through the secondary coil 31 accordingly. An alternating magnetic field is generated by this current. The detection coils 21 to 24 provided in the power transmitter 10 pick up echo signals generated as the alternating magnetic field as detection signals Vs1 to Vs4. By arranging the plurality of detection coils 21 to 24 around the primary coil 15, it is possible to obtain the distribution of the intensity of the echo signal around the primary coil 15. The detection circuit 25 sequentially outputs a signal having a pulse width corresponding to the intensity of each of the obtained detection signals Vs1 to Vs4 to the control circuit 16 as an output signal Pos. The control circuit 16 can calculate and determine the orientation of the secondary coil 31 with respect to the primary coil 15 by comparing the relative intensities of the output signals Pos obtained sequentially according to the detection signals Vs1 to Vs4. That is, the detection circuit 25 and the control circuit 16 compare the relative intensities of the obtained detection signals Vs1 to Vs4. When the pulse signal Vp is supplied to the excitation coil 18 and the AC magnetic field generated by the current induced in the secondary coil 31 is picked up by the detection coils 21 to 24, the switch 36 is opened.

  Furthermore, it is possible to notify the user of the orientation of the secondary coil 31 with respect to the primary coil 15 by arranging a light emitting element such as an LED in the power transmitter 10. Around the power transmitter 10, LEDs 1 to 8 are arranged at equal intervals. The distance between each LED and the central axis of the primary coil 15 is substantially the same, and each LED1 to LED8 is arranged to draw a regular octagon. The control circuit 16 can guide the user to move the secondary coil 31 toward the primary coil 15 by turning on an LED located in a certain direction of the primary coil 15 with respect to the secondary coil 31. Is possible. For example, in the state as shown in FIG. 3, one or both of the LED 6 and the LED 7 in the direction in which the primary coil 15 is positioned with respect to the secondary coil 31 may be lit. When the central axes of the primary coil 15 and the secondary coil 31 substantially coincide with each other, the strengths of the detection signals Vs1 to Vs4 are substantially equal to each other. Therefore, the secondary coil 31 is disposed at an appropriate position with respect to the primary coil 15. Can be recognized. Thereafter, power is transmitted from the primary coil 15 to the secondary coil 31. Any number of light emitting elements may be arranged around the power transmitter 10 as long as the number is sufficient to guide the direction. For example, four or six LEDs can be arbitrarily selected such as being arranged at equal intervals.

  Next, FIG. 4 shows a detection circuit of the wireless power transmission apparatus of the present invention. The detection circuit 25 includes amplification circuits AMP1 to AMP4, smoothing circuits SMO1 to SMO4, comparison circuits CMP1 to CMP4, and a switching circuit SEL.

The amplifier circuit AMP1 includes an operational amplifier OP1, a resistor R11, and a feedback resistor R21.
The detection signal Vs1 is supplied to the non-inverting input terminal of the operational amplifier OP1. On the other hand, one end of the resistor R11 is connected to the inverting input terminal of the operational amplifier OP1, and the other end of the resistor R11 is grounded. A feedback resistor R21 is connected between the inverting input terminal and the output terminal of the operational amplifier OP1. A signal output from the operational amplifier OP1 is referred to as an amplified signal Va1.
The amplifier circuits AMP2 to AMP4 also have operational amplifiers OP2 to OP4, resistors R12 to R14, and feedback resistors R22 to R24, respectively, and have the same connection relationship as that of the amplifier circuit AMP1. The signals output from the operational amplifiers OP2 to OP4 are referred to as amplified signals Va2 to Va4, respectively.

The smoothing circuit SMO1 includes a diode D1, a resistor R31, and a capacitor C1.
The anode of the diode D1 is connected to the output terminal of the operational amplifier OP1. One end of a resistor R31 and a capacitor C1 is connected to the cathode of the diode D1, and the other end of the resistor R31 and the capacitor C1 is grounded. A signal at the cathode of the diode D1 is defined as a smoothing signal Vsm1.
The smoothing circuits SMO2 to SMO4 also have diodes D2 to D4, resistors R32 to R34, and capacitors C2 to C4, respectively, and have the same connection relationship as the smoothing circuit SMO1. In addition, the cathode signals of the diodes D2 to D4 are defined as smoothing signals Vsm2 to Vsm4, respectively.

The comparison circuit CMP1 includes a comparator CO1.
The cathode of the diode D1 is connected to the non-inverting input terminal of the comparator CO1, and the smoothing signal Vsm1 is supplied. On the other hand, the reference voltage Vref is supplied to the inverting input terminal of the comparator CO1. A signal output from the comparator CO1 is referred to as a comparison signal Po1.
The comparison circuits CMP2 to CMP4 are also provided with comparators CO2 to CO4, respectively, and have the same connection relationship as that of the comparison circuit CMP1. The signals output from the comparators CO2 to CO4 are referred to as comparison signals Po2 to Po4, respectively.

The switching circuit SEL includes AND circuits AND1 to AND4 and an OR circuit OR1. Each of the AND circuits AND1 to AND4 includes first and second input terminals. The OR circuit OR1 includes first, second, third, and fourth input terminals.
The comparison signal Po1 is supplied to the first input terminal of the AND circuit AND1. A control signal S1 is supplied to the second input terminal of the AND circuit AND1. The AND circuit AND1 calculates and outputs a logical product of the comparison signal Po1 and the control signal S1.
The AND circuits AND2 to AND4 have the same connection relationship as that of the AND circuit AND1.
The output terminals of the AND circuits AND1 to AND4 are connected to the first to fourth input terminals of the OR circuit OR1, respectively. The OR circuit OR1 calculates and outputs a logical sum of signals supplied to the first to fourth input terminals. A signal output from the OR circuit OR1 is defined as an output signal Pos. This output signal Pos is supplied to the control circuit 16.

The amplifier circuits AMP1 to AMP4 amplify the detection signals Vs1 to Vs4 by the operational amplifiers OP1 to OP4, respectively, and output the amplified signals Va1 to Va4.
The smoothing circuits SMO1 to SMO4 respectively rectify and smooth the amplified signals Va1 to Va4 obtained by the diodes D1 to D4, resistors R31 to R34, and capacitors C1 to C4, and output the smoothed signals Vsm1 to Vsm4 that are single peak signals. To do.
The comparison circuits CMP1 to CMP4 compare the smoothed signals Vsm1 to Vsm4 with the reference voltage Vref, respectively. When the smoothed signals Vsm1 to Vsm4 are larger than the reference voltage Vref, the high level is output. When the smoothed signals Vsm1 to Vsm4 are smaller than the reference voltage Vref, the low level comparison signals Po1 to Po4 are output.
The switching circuit SEL selects and outputs one of the comparison signals Po1 to Po4. Alternatively, the logical sum of the comparison signals Po1 to Po4 is calculated and output as the output signal Pos. Which operation is performed is controlled by control signals S <b> 1 to S <b> 4 supplied from the control circuit 16.

  Here, FIG. 5 shows a timing chart showing the detection signal intensity detection operation of the present invention. When the pulse signal Vp is supplied to the excitation coil 18 and the detection signals Vs1 to Vs4 are picked up, the switch 36 provided in the power receiver 30 is opened.

At time t1, a single pulse signal Vp having a width of about 400 ns is supplied to the excitation coil 18.
At time t2 when a predetermined time has elapsed from time t1, an echo signal that vibrates at the detection resonance frequency fd is picked up by the detection coil 21. When the pulse signal Vp is supplied to the excitation coil 18, a resonance circuit including the secondary coil 31, the secondary resonance capacitor 32, and the detection capacitor 33 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 31. The echo signal is an alternating magnetic field sent from the secondary coil 31 to the primary side at this time. This echo signal is picked up by the detection coil 21 by electromagnetic induction, and a detection signal Vs 1 is generated in the detection coil 21. Then, the detection signal Vs1 is amplified by the operational amplifier OP1, an amplified signal Va1 is generated, and the smoothing signal Vsm1 gradually increases. This detection signal Vs1 gradually attenuates while freely vibrating.
At time t3, the smoothing signal Vsm1 becomes larger than the reference voltage Vref. Then, the comparison signal Po1 output from the comparator CO1 is switched from the low level to the high level. Thereafter, the smoothing signal Vsm1 gradually increases, rises to a certain peak value, and then gradually decreases.
At time t4, the smoothing signal Vsm1 becomes smaller than the reference voltage Vref. Then, the comparison signal Po1 output from the comparator CO1 is switched from the high level to the low level. Further, the detection signal Vs1 converges with time while being attenuated. Accordingly, the smooth signal Vsm1 also converges.

  The intensity of the echo signal depends on the distance between the primary coil 15 and the secondary coil 31. The closer the distance between the primary coil 15 and the secondary coil 31, the stronger the intensity of the echo signal, and the longer the pulse width of the comparison signal Po1 obtained. Further, as the distance between the primary coil 15 and the secondary coil 31 increases, the intensity of the echo signal becomes weaker and the pulse width of the obtained comparison signal Po1 becomes shorter.

  Thus, the stronger the echo signal, that is, the detection signal Vs1, the stronger the smoothing signal Vsm1 and the greater the width of the comparison signal Po1. Therefore, the signal strength of the detection signal Vs1 can be evaluated from the pulse width of the obtained comparison signal Po1. If the secondary coil 31 is not disposed in the vicinity of the primary coil 15, no echo signal is generated, and thus the detection signal Vs1 is not detected. Therefore, the comparison signal Po1 remains at a low level. That is, when no echo signal is generated, it can be seen that the secondary coil 31 is sufficiently separated from the primary coil 15. Therefore, not only the intensity of the echo signal, that is, the distance between the primary coil 15 and the secondary coil 31 but also the presence or absence of the secondary coil 31 can be detected from the comparison signal Po1.

  Although only the operations of the amplifier circuit AMP1, the smoothing circuit SMO1, and the comparison circuit CMP1 have been described in FIG. 5, the same signal processing is performed on the amplifier circuits AMP2 to AMP4, the smoothing circuits SMO2 to SMO4, and the comparison circuits CMP2 to CMP4.

  If the signal strengths of the detection signals Vs1 to Vs4 picked up by the plurality of detection coils 21 to 24 are compared and calculated, the orientation of the power receiver 30 with respect to the power transmitter 10 can be obtained. An arithmetic unit such as a microcomputer used as an example of the control circuit 16 has difficulty in processing a plurality of signals at the same time. Therefore, it is necessary to sequentially extract signals to be processed. By using the switching circuit SEL in the detection circuit 25, a signal channel can be selected and taken out.

  Here, FIG. 6 shows a timing chart in the position detection mode of the present invention. The user moves the power receiver 30 on the upper surface of the power transmitter 10 and performs alignment so that the central axes of the primary coil 15 and the secondary coil 31 are substantially matched. Here, it is assumed that the sampling time is sufficiently short with respect to the alignment movement. Therefore, it is assumed that the intensity of the detection signals Vs1 to Vs4 does not change within a short time, that is, the pulse width of the comparison signals Po1 to Po4 does not change.

  A single pulse signal Vp having a width of about 400 ns is supplied to the excitation coil 18 at a predetermined period T1. Each time the pulse signal Vp is supplied, comparison signals Po1 to Po4 having a pulse width corresponding to the distance and orientation between the primary coil 15 and the secondary coil 31 are obtained. In order to sequentially extract the comparison signals Po1 to Po4, every time the pulse signal Vp is applied to the excitation coil 18, only one of the control signals S1 to S4 needs to be sequentially set to the high level. Note that the pulse widths of the control signals S1 to S4 are set to be larger than the expected maximum value of the pulse widths of the comparison signals Po1 to Po4. The period T1 is also set to be larger than the pulse width of the control signals S1 to S4.

  When the (n + 1) th pulse signal Vp is supplied, only the control signal S1 becomes high level, and the other control signals S2 to S4 remain at low level. During this period, the same signal as the comparison signal Po1 is output as it is as the output signal Pos. Before the next pulse signal Vp is supplied, the control signal S1 is switched to the low level.

  When the (n + 2) th pulse signal Vp is supplied, only the control signal S2 becomes high level, and the other control signals S1, S3, and S4 remain at low level. During this period, the same signal as the comparison signal Po2 is output as it is as the output signal Pos. Before the next pulse signal Vp is supplied, the control signal S2 is switched to the low level.

  When the (n + 3) th pulse signal Vp is supplied, only the control signal S3 becomes high level, and the other control signals S1, S2, and S4 remain at low level. During this period, the same signal as the comparison signal Po3 is output as it is as the output signal Pos. Before the next pulse signal Vp is supplied, the control signal S3 is switched to the low level.

  When the n + 4th pulse signal Vp is supplied, only the control signal S4 becomes high level, and the other control signals S1 to S3 remain at low level. During this period, the same signal as the comparison signal Po4 is output as it is as the output signal Pos. Before the next pulse signal Vp is supplied, the control signal S4 is switched to the low level.

  When the n + 5th pulse signal Vp is supplied, only the control signal S1 becomes high level again, and the same operation is repeated thereafter.

  Thus, each time the pulse signal Vp rises, only the control signal corresponding to the comparison signal to be selected is set to the high level, and the other control signals are set to the low level. As a result, only the selected comparison signal is output from the corresponding AND circuit. A signal output from the AND circuit is obtained as an output signal Pos from the OR circuit OR1. The control circuit 16 measures and quantifies the pulse width of the output signal Pos.

  After sequentially extracting the output signals Pos of 4 channels corresponding to the comparison signals Po1 to Po4, the control circuit 16 compares and calculates the relative strengths of the output signals Pos of each 4 channels, and the secondary coil 31 for the primary coil 15 is compared. Find the heading. The control circuit 16 turns on the LED corresponding to the obtained direction and notifies the user of the direction of the secondary coil 31 with respect to the primary coil 15. As described above, since the four-channel output signal Pos is sequentially extracted, the position detection cycle is 4 × T1. This position detection operation is repeated until the relative position between the primary coil 15 and the secondary coil 31 falls within a predetermined range. When the secondary coil 31 is disposed at an appropriate position with respect to the primary coil 15, power transmission or the like is performed from the primary coil 15 to the secondary coil 31. That is, the position detection mode is continued until the relative position between the primary coil 15 and the secondary coil 31 is within a predetermined range.

  Note that although the 4-input OR circuit OR1 is used in the switching circuit SEL, a plurality of 2-input OR circuits may be combined. For example, the output terminals of any two AND circuits are connected to the input terminals of the first two-input OR circuit. The output terminals of the other two AND circuits are connected to the input terminals of the second two-input OR circuit. The output terminal of the first 2-input OR circuit and the output terminal of the second 2-input OR circuit are connected to the input terminals of the third 2-input OR circuit. Then, the output signal Pos is obtained from the output of the third two-input OR circuit. In this way, an equivalent 4-input OR circuit can be configured by combining a plurality of 2-input OR elements.

  As described above, in the position detection mode for detecting the position of the secondary coil 31 with respect to the primary coil 15, the detection signals Vs1 to Vs4 are sequentially extracted. In this case, an appropriate sampling frequency must be ensured in order to ensure the response speed of the detection result with respect to the alignment movement. Of course, the signal processing method in the position detection mode can be applied to a standby mode in which only the presence or absence of a power receiver is checked, but it is desirable to separately provide a standby mode with a low sampling frequency in order to reduce standby power.

  In the position detection mode, it is necessary to accurately measure the pulse widths of the comparison signals Po1 to Po4. On the other hand, in the standby mode, it is only necessary to detect whether or not the secondary coil 31 is in the vicinity of the primary coil 15. That is, it is only necessary to detect the presence or absence of the detection signals Vs1 to Vs4.

  Next, FIG. 7 shows a timing chart in the standby mode of the present invention.

  A single pulse signal Vp having a width of about 400 ns is supplied to the excitation coil 18 at a predetermined period T2. The cycle T2 of the pulse signal Vp in the standby mode is set to be longer than the cycle T1 of the pulse signal Vp in the position detection mode. In order to detect the presence or absence of any of the detection signals Vs1 to Vs4, each time the pulse signal Vp is applied to the excitation coil 18, the control signals S1 to S4 may be simultaneously set to the high level.

  When the (m + 1) th pulse signal Vp is supplied, the control signals S1 to S4 simultaneously become high level. When none of the comparison signals Po1 to Po4 is detected, the output signal Pos also remains at a low level. Therefore, it can be seen that the secondary coil 31 does not exist in the vicinity of the primary coil 15. Before the next pulse signal Vp is supplied, the control signals S1 to S4 are switched to the low level.

  Even when the m + 2nd pulse signal Vp is supplied, the control signals S1 to S4 simultaneously become high level. As shown in the figure, it is assumed that comparison signals Po2 and Po3 having a certain pulse width are detected. A signal obtained by calculating the logical sum of the comparison signals Po1 to Po4 is obtained as the output signal Pos, and it can be seen that the secondary coil 31 exists in the vicinity of the primary coil 15. Before the next pulse signal Vp is supplied, the control signals S1 to S4 are switched to the low level.

  Thus, each time the pulse signal Vp rises, the control signals S1 to S4 are simultaneously set to the high level. Thus, even when only one of the detection signals Vs1 to Vs4 is detected, it can be detected as the output signal Pos, so that the presence / absence of the power receiver 30 can be quickly determined. In addition, since it is not necessary to sequentially extract the comparison signals Po1 to Po4 corresponding to the detection signals Vs1 to Vs4, the timing control method can be simplified.

  When a plurality of comparison signals Po1 to Po4 are detected simultaneously, the signal having the largest pulse width among the comparison signals Po1 to Po4 is output as the output signal Pos. Therefore, the presence / absence of the echo signal from the power receiver 30 can be detected simultaneously in a range where the echo signal can be detected. Therefore, the sampling frequency of the drive pulse Vp in the standby mode can be reduced to a quarter of that in the position detection mode, and the standby power can be significantly reduced by setting the cycle T2 of the drive pulse Vp to be large. it can.

  The pulse signal Vp is repeatedly supplied at a predetermined cycle T2 until the output signal Pos is detected. That is, the standby mode is continued until the output signal Pos is detected. When the output signal Pos is detected, the operation is switched from the standby mode to the position detection mode. In the position detection mode, when no output signal Pos is detected for a predetermined time, the power consumption can be reduced by switching the operation to the standby mode.

  Next, FIG. 8 shows another example of the switching circuit of the wireless power transmission device of the present invention. Parts having the same functions as those of the switching circuit SEL described above are denoted by the same reference numerals and description thereof is omitted.

  The switching circuit SEL ′ includes AND circuits AND1 to AND4 and OR circuits OR1 and OR2. The OR circuit OR2 includes first, second, third, and fourth input terminals. The comparison signals Po1 to Po4 are respectively supplied to the first to fourth input terminals of the OR circuit OR2. The OR circuit OR2 calculates and outputs a logical sum of the comparison signals Po1 to Po4 supplied to the first to fourth input terminals. A signal output from the OR circuit OR2 is defined as an output signal Pos'. This output signal Pos ′ is supplied to the control circuit 16.

  When any of the comparison signals Po1 to Po4 is detected, it appears as the output signal Pos' of the OR circuit OR2. In the standby mode, the output signal Pos' of the OR circuit OR2 is detected without going through the AND circuits AND1 to AND4. The control circuit 16 can detect whether or not the secondary coil 31 is near the primary coil 15 based on the output signal Pos ′. In this case, it is not necessary to supply the control signals S1 to S4 to the detection circuit 25 in the standby mode, and the control operation of the switching circuit SEL 'can be omitted in the standby mode.

  Such a configuration of the switching circuits SEL and SEL ′ is merely an example. Any circuit configuration may be used as long as the detection signals Vs1 to Vs4 are collectively detected in the standby mode and the detection signals Vs1 to Vs4 can be selectively detected in the position detection mode. By using a digital circuit using a logic element, the collective detection operation of the detection signals Vs1 to Vs4 and the switching of the operation of sequentially detecting the detection signals Vs1 to Vs4 can be realized with a simple configuration.

  Next, FIG. 9 shows a block diagram of a power transmitter 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 the Example mentioned above, and description is abbreviate | omitted. The power transmitter 40 includes a DC power supply 11, a smoothing capacitor 12, a drive circuit 13, a primary resonance capacitor 14, a primary coil 15, a control circuit 16, a pulse generation circuit 17, an excitation coil 18, detection coils 21 to 24, a detection circuit 25, and an addition. A circuit 41 and a comparison circuit 42 are provided.

  The detection signals Vs1 to Vs4 excited by the detection coils 21 to 24 are supplied to the addition circuit 41 together with the detection circuit 25. The adder circuit 41 outputs a signal obtained by adding the detection signals Vs <b> 1 to Vs <b> 4 to the comparison circuit 42. The comparison circuit 42 compares the output of the addition circuit 41 with a reference value and outputs the result to the control circuit 16.

  When any one of the detection signals Vs1 to Vs4 is detected, it appears as an output signal of the adder circuit 41. The comparison circuit 42 compares the output of the adder circuit 41 with a reference value. When the output of the adder circuit 41 becomes larger than the reference value, it can be recognized that the secondary coil 31 exists in the vicinity of the primary coil 15. In this case, it is not necessary to supply the control signals S1 to S4 to the detection circuit 25 in the standby mode, and the control operation of the detection circuit 25 can be omitted.

  In the embodiment described above, position detection is performed using four detection coils, but this is only an example. The two detection coils are used so that the central axis of each detection coil is substantially equidistant from the central axis of the primary coil 19, and the central axis of each detection coil is symmetrical with respect to the central axis of the primary coil 15. You may arrange so that. Further, using three detection coils, the detection coils are arranged so that the central axes of the detection coils are substantially equidistant from the central axis of the primary coil 15, and the central axes of the detection coils are positioned at the vertices of the equilateral triangle. You may arrange in. Similarly, five or more detection coils may be used. In any case, detection signals picked up by the respective detection coils may be collectively detected in the standby mode, and detection signals may be selectively detected in the position detection mode.

  Further, the presence / absence of the power receiver 30 and the relative position between the primary coil 15 and the secondary coil 31 are obtained from the pulse widths of the comparison signals Po1 to Po4 obtained by amplifying, smoothing and comparing the detection signals Vs1 to Vo4. However, the position detection method is not limited to such an example. For example, the presence / absence of a power receiver and the relative position between the primary coil 15 and the secondary coil 31 may be obtained from the maximum values of the waveforms of the amplified signals Va1 to Va4 obtained by simply amplifying the detection signals Vs1 to Vo4. As long as the presence / absence of the power receiver 30 and the relative position between the primary coil 15 and the secondary coil 31 can be obtained based on the intensity of the detection signals Vs1 to Vo4, any form may be used.

  Further, the secondary coil 31 may be excited to generate an echo signal without using the pulse generation circuit 17 or the excitation coil 18. For example, instead of supplying the pulse signal Vp to the excitation coil 18, the primary coil 15 is driven at a frequency close to the detection resonance frequency fd for a short time or is driven so that a single pulse is generated. In response to this, a current oscillating at the detection resonance frequency fd flows in the secondary coil 31, and an echo signal is generated. By operating in this way, the excitation coil 18 and the pulse generation circuit 17 can be omitted, a simple configuration can be achieved, and the cost can be reduced. The present invention can be implemented with various modifications without departing from the spirit of the present invention.

10, 40 Transmitter 11 DC power supply 12 Smoothing capacitor 13 Drive circuit 14 Primary resonant capacitor
DESCRIPTION OF SYMBOLS 15 Primary coil 16 Control circuit 17 Pulse generation circuit 18 Excitation coil 21-24 Detection coil 25 Detection circuit 30 Power receiver 31 Secondary coil 32 Secondary resonance capacitor 33 Detection capacitor 34 Rectification circuit 35 Smoothing capacitor 36 Switch 37 Load 41 Addition circuit 42 Comparison circuit

Claims (7)

A primary coil for supplying electric power to the secondary coil by electromagnetic induction, an excitation coil for exciting the secondary coil, and a plurality of detection coils for detecting an alternating magnetic field generated from the excited secondary coil;
A detection circuit that selectively outputs an output signal related to all of the plurality of detection coils or an output signal related to any of the plurality of detection coils to a control circuit;
When the detection circuit outputs an output signal related to all of the plurality of detection coils to the control circuit, a cycle for exciting the secondary coil is sequentially set, and the detection circuit sequentially outputs an output signal related to any of the plurality of detection coils. A wireless power transmission device, characterized in that it is set longer than a period for exciting the secondary coil when outputting to the control circuit. A primary coil for supplying electric power to the secondary coil by electromagnetic induction, the primary coil for exciting the secondary coil, and a plurality of detection coils for detecting an alternating magnetic field generated from the excited secondary coil;
A detection circuit that selectively outputs an output signal related to all of the plurality of detection coils or an output signal related to any of the plurality of detection coils to a control circuit;
When the detection circuit outputs an output signal related to all of the plurality of detection coils to the control circuit, a cycle for exciting the secondary coil is sequentially set, and the detection circuit sequentially outputs an output signal related to any of the plurality of detection coils. A wireless power transmission device, characterized in that it is set longer than a period for exciting the secondary coil when outputting to the control circuit. When said detecting circuit outputs an output signal for all the plurality of detection coils to the control circuit, whether the control circuit based on the output signal, the secondary coil in the vicinity of the primary coil is disposed Standby mode to detect
When the detection circuit sequentially outputs an output signal related to any of the plurality of detection coils to the control circuit, the control circuit detects a relative position between the primary coil and the secondary coil based on the output signal. The wireless power transmission apparatus according to claim 1, further comprising a position detection mode. The light emitting elements arranged at equal intervals around the primary coil are provided, and based on the detection result of the relative position between the primary coil and the secondary coil, the light emitting elements positioned in the direction of the primary coil with respect to the secondary coil The wireless power transmission device according to claim 3, wherein the light emitting element is turned on.   The plurality of detection coils are planar 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. 5. The wireless power transmission device according to claim 4. The detection circuit generates a plurality of comparison signals having a predetermined pulse width according to the intensity of detection signals excited by the plurality of detection coils, and includes a logic circuit.
The logic circuit to be output to said control circuit a logical OR of all the comparison signal as an output signal, or single any one of claims 1 to 5, output to the control circuit one of the comparison signal as an output signal The wireless power transmission device according to the item. A method for detecting a relative position between a power transmitter and a power receiver,
A first step of exciting a secondary coil provided in the power receiver;
A second step of collectively detecting an alternating magnetic field generated from the secondary coil excited in the first step by a plurality of detection coils provided in the power transmitter;
A third step of detecting whether the power receiver is disposed in the vicinity of the power transmitter based on the AC magnetic field detected in the second step;
A fourth step of exciting the secondary coil;
A fifth step of sequentially detecting the alternating magnetic field generated from the secondary coil excited in the fourth step by the plurality of detection coils;
A sixth step of detecting a relative position between the power transmitter and the power receiver based on the AC magnetic field detected in the fifth step;
A relative position detecting method, wherein a period for repeatedly exciting the secondary coil in the first step is set longer than a period for repeatedly exciting the secondary coil in the fourth step.

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