JP2014222994A - Wireless power transmission device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect metallic foreign matter on the basis of a change in inductance of a primary coil and a change in input impedance of an inverter due to the metallic foreign matter.SOLUTION: A wireless power transmission device includes: a primary L-Cresonator comprising a coil Land a capacitor Cconnected in series; a drive power supply which switches DC power at a fixed drive frequency ωto drive the primary L-Cresonator; voltage detection means for detecting the voltage V(L) across the coil Land the voltage V(C) across the capacitor Cduring driving of the primary L-Cresonator; voltage ratio calculation means for calculating a voltage ratio V(L)/V(C) from the detected voltage V(L) across the coil Land the detected voltage V(C) across the capacitor C; and determination means for determining the presence or absence of metallic foreign matter on a mounting surface of a device to be charged, from the calculated voltage ratio V(L)/V(C) and a predetermined threshold.

Description

  The present invention relates to a wireless power transmission device, and more particularly to detection of a metallic foreign object on a power transmission surface of the wireless power transmission device.

2. Description of the Related Art Conventionally, wireless charging that transmits power in a non-contact manner to electronic device terminals such as mobile phones is becoming widespread. Such wireless charging allows non-contact power transmission by generating electromagnetic induction between a power transmission coil L _p built in a power transmitter and a power receiving coil L _s built in a power receiver such as an electronic device terminal. Do. Then, the power transmitted to the power receiving coil L _s is supplied to a load such as a secondary battery built in the power receiver via the rectifier circuit.

  As described above, the wireless charging can be performed simply by placing the power receiver on the power transmitter, and is excellent in convenience because it is not necessary to connect or disconnect the power connector. Furthermore, since there is no need to provide a power connector for charging, there is an advantage that it is easy to add a waterproof function and a dustproof function to the power receiver.

JP 2011-30422 A

  However, in the above-described system, when a metal foreign object comes close to the power transmission / reception coil, an eddy current is induced in the metal foreign object, so that the metal foreign object generates heat and an extra power loss occurs. Therefore, it is desirable to detect a metal foreign object from the viewpoint of power transmission efficiency and use safety (for example, see Patent Document 1).

Here, as one of effective detection methods for metal foreign objects, there is a power measurement method. FIG. 11 shows a conceptual diagram of metal foreign object detection by a power loss method for calculating a conventional power balance. The basic principle is a method to follow the fate of the power P _in injected into the inverter.

That is, there is no metallic foreign matter, injection power _{P in} is the power loss _{P Tx} generated in the inverter or primary _L p -C _p resonator is the sum of the power _{P Rx} secondary side is received. When a metal foreign object is brought close to the power transmission coil, the above power balance is lost, and the difference ΔP between them becomes a vortex loss due to the metal foreign object. Therefore, a metallic foreign object can be detected from the numerical value of ΔP.

However, there are some problems in the detection of metallic foreign objects by this power loss method. First, 1) Many power loss components are included in the power terms _PTx and _PRx , and in order to measure each component, it is necessary to verify an appropriate loss model and theoretical formula. There is a problem that it causes an increase in cost on hardware. 2) Since the on-resistance of the FET of the full-bridge inverter and the Vf of the secondary rectifier diode have temperature characteristics, there is a problem that it is difficult to ensure the power loss calculation accuracy unless temperature correction is performed. Furthermore, there is also a problem that detection takes time because an accurate power loss cannot be obtained unless the power control is stabilized.

  Therefore, the present invention has been made in view of the above-described problems, and wireless power transmission for detecting a metallic foreign object based on a change in inductance of a primary coil or a change in input impedance of an inverter caused by the metallic foreign object. An object is to provide an apparatus.

  The present invention proposes the following matters in order to solve the above problems. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected and demonstrated, it is not limited to this.

(1) In the present invention, the primary L _p -C _p resonator including the coil L _p and the capacitor C _p connected in series, and DC power is switched at a constant drive frequency ω _dr to switch the primary L _p -C. a driving power source for driving the _p resonator, when the drive of the primary _L p -C _p resonator, a voltage detection to detect coil _{L p} voltage V and _{(L p)} and a capacitor _{C p} voltage V _{(C p)} And a voltage ratio calculating means for calculating a voltage ratio V (L _p ) / V (C _p ) from the detected voltage V (L _p ) between the coils L _p and voltage V (C _p ) between the capacitors C _p. And determining means for determining the presence / absence of a metal foreign object on the placement surface of the device to be charged from the calculated voltage ratio V (L _p ) / V (C _p ) and a predetermined threshold value. A wireless power transmission device is proposed.

According to the present invention, or coil _{L p} voltage V _{(L p)} and the capacitor _{C p} voltage V _{(C p)} from the voltage ratio _{V (L p) / V (} C p) is within a predetermined range The presence / absence of a metallic foreign object can be determined based on whether or not it is present. In other words, the determination can be performed using general measurement parameters of the power transmitter, and the determination can be performed at an arbitrary timing, so that the determination process can be executed quickly by a simple method.

(2) In the present invention, the primary L _p -C _p resonator including the coil L _p and the capacitor C _p connected in series, and DC power is switched at the variable drive frequency ω _{dr ′} to switch the primary L _p -C. a driving power source for driving the _p resonator, when the drive of the primary _L p -C _p resonator, a voltage detection to detect coil _{L p} voltage V and _{(L p)} and a capacitor _{C p} voltage V _{(C p)} V (L _p ) / (V (C _p ) * ω _{dr ′} ² ) is calculated from the means, the _detected voltage V (L _p ) between the coils L _p and the voltage V (C _p ) between the capacitors C _p. Based on the voltage ratio calculation means, the calculated voltage ratio V (L _p ) / (V (C _p ) * ω _{dr ′} ² ), and a predetermined threshold value, the presence / absence of a metal foreign object on the surface to be charged is determined. And a wireless power transmission device characterized by comprising: It is.

According to the invention, when the driving frequency omega _{DR 'is} also variable, the coil _{L p} voltage V _{(L p)} and the capacitor _{C p} voltage V _{(C p)} from the voltage ratio V _(L p) / The presence / absence of a metal foreign object can be determined based on whether (V (C _p ) * ω _{dr ′} ² ) is within a predetermined range.

(3) The present invention switches the primary L _p -C _p resonator composed of the coil L _p and the capacitor C _p connected in series, and DC power (V _ddc , I _ddc ) at the drive frequency ω _dr to a driving power source for driving the primary _L p -C _p resonator, when the drive of the primary _L p -C _p resonator monitors the midpoint voltage _{V c} between the coil _{L p} and the capacitor _{C p,} between the coils _{L p} and a peak voltage detecting means for detecting a peak value _{V peak} of the voltage V _{(L p),} between the coils _{L p} from the peak value _{V peak} and driving DC voltage _{V ddc} of the detection out coil _{L p} voltage V _{(L p)} Voltage ratio calculating means for calculating a voltage ratio V (L _p ) / V (C _p ) between the voltage V (L _p ) and the voltage V (C _p ) between the capacitors C _p, and the calculated voltage ratio V (L _p ) / V _{(C p)} with a predetermined threshold value and It proposes a wireless power transmission apparatus characterized by comprising a determination means for determining whether the foreign metal substance in the mounting surface of the Luo be charged device.

According to the present invention, a coil _{L p} and the capacitor _{C p} from the midpoint voltage _{V c} between the detected peak value _{V peak} of the coil _{L p} voltage V _{(L p),} the detected coil _{L p} voltage V (L voltage ratio V (L _p ) / V () of the voltage V (L _p ) between the coils L _p and the voltage V (C _p ) between the capacitors C _p calculated from the peak value V _{peak of p} ) and the drive DC voltage V _ddc. Whether or not there is a metal foreign object can be determined based on whether or not C _p ) is within a predetermined range.

(4) The present invention includes a primary _L p -C _p resonator consisting of a coil _{L p} and a capacitor _{C p} connected in series, the primary _L p -C _p resonance by switching the DC power at the driving frequency omega _dr a driving power source for driving the vessel, at the time of driving of the primary _L p -C _p resonator, enter the midpoint voltage _{V c} between the coil _{L p} and the capacitor _{C p,} the driving frequency omega _dr, midpoint voltage _{V c} A multiplexer that extracts the first ½ period voltage waveform and the second ½ period voltage waveform, and the extracted first ½ period voltage waveform and second ½ period voltage waveform Are respectively smoothed to obtain a first smoothed value and a second smoothed value, and from the first smoothed value and the second smoothed value, the voltage V (L _p ) between the coils L _p. And the voltage ratio V (L _p ) / V (C _p ) between the voltage V (C _p ) between the capacitor C _p A voltage ratio calculating means for calculating, a determining means for determining the presence or absence of a metallic foreign object on the mounting surface of the device to be charged from the calculated voltage ratio V (L _p ) / V (C _p ) and a predetermined threshold value; A wireless power transmission device characterized by comprising:

According to the invention, by a multiplexer, and extracted first half cycle the voltage waveform of the midpoint voltage V _c at the time of driving and the second half cycle the voltage waveform, determined them from the smoothed value Depending on whether or not the voltage ratio V (L _p ) / V (C _p ) between the voltage V (L _p ) between the coils L _p and the voltage V (C _p ) between the capacitors C _p is within a predetermined range, the metal The presence or absence of foreign matter can be determined.

(5) The present invention switches the primary L _p -C _p resonator composed of the coil L _p and the capacitor C _p connected in series and the DC power (V _ddc , I _ddc ) at the drive frequency ω _dr to from a driving power source for driving the primary L _p -C _p resonator, and an output impedance calculating means for calculating an output impedance Z _ddc of the drive power source, with a predetermined threshold value and the output impedance Z _ddc the driving power thus calculated Proposed is a wireless power transmission device comprising: determination means for determining the presence or absence of a metallic foreign object on a mounting surface of a device to be charged.

According to the present invention, the presence or absence of a metallic foreign object can be determined based on whether or not the output impedance Z _ddc of the drive power source is within a predetermined range.

(6) The present invention switches a primary L _p -C _p resonator composed of a series-connected coil L _p and a capacitor C _p and DC power (V _ddc , I _ddc ) at a constant drive frequency ω _dr. a driving power source for driving the primary _L p -C _p resonator Te, during driving of the primary _L p -C _p resonator coil _{L p} voltage V _{(L p)} and the capacitor _{C p} voltage V _{(C p} ) And a voltage ratio V (L _p ) / V (C _p ) from the detected voltage V (L _p ) between the coils L _p and the voltage V (C _p ) between the capacitors C _p. Voltage ratio calculating means for calculating, output impedance calculating means for calculating the output impedance Z _ddc of the driving power source, and the calculated voltage ratio V (L _p ) / V (C _p ) and a predetermined first threshold value And the calculated drive power supply Proposed wireless power transmission apparatus characterized by comprising a determination means for determining whether the foreign metal substance in the mounting surface of the charging device from the comparison with the second predetermined threshold value and the output impedance Z _ddc doing.

The method of determining the presence or absence of a metal foreign object with the output impedance Z _ddc of the drive power supply is simple in itself, but considering that the output impedance Z _ddc of the drive power supply also depends on the terminal load, it is difficult to set the threshold value. There is also. However, according to the present invention, the voltage ratio of the output impedance _Z method of determining the presence or absence of a foreign metal substance in _ddc and a coil _{L p} voltage V of the drive power source _{(L p)} and the capacitor _{C p} voltage V _{(C p)} Reliability is improved by using a combination of the method of determining the presence or absence of a metal foreign matter based on V (L _p ) / V (C _p ).

(7) The present invention switches the primary L _p -C _p resonator composed of the coil L _p and the capacitor C _p connected in series and the DC power (V _ddc , I _ddc ) at the drive frequency ω _dr to a driving power source for driving the primary _L p -C _p resonator, when the drive of the primary _L p -C _p resonator monitors the midpoint voltage _{V c} between the coil _{L p} and the capacitor _{C p,} between the coils _{L p} and a peak voltage detecting means for detecting a peak value _{V peak} of the voltage V _{(L p),} between the coils _{L p} from the peak value _{V peak} and driving DC voltage _{V ddc} of the detection out coil _{L p} voltage V _{(L p)} Voltage ratio calculating means for calculating a voltage ratio V (L _p ) / V (C _p ) between the voltage V (L _p ) and the voltage V (C _p ) between the capacitors C _p , and an output impedance Z _ddc of the drive power supply Output impedance to be calculated A calculation unit, the calculated voltage ratio _{V (L p) / V (} C p) with a predetermined second predetermined first threshold value and the comparison and the output impedance Z _ddc the calculated drive power supply Proposed is a wireless power transmission device comprising: a determination unit that determines presence / absence of a metal foreign object on a mounting surface of a device to be charged based on comparison with a threshold value.

The method of determining the presence or absence of a metal foreign object with the output impedance Z _ddc of the drive power supply is simple in itself, but considering that the output impedance Z _ddc of the drive power supply also depends on the terminal load, it is difficult to set the threshold value. There is also. However, according to the present invention, the voltage ratio of the output impedance _Z method of determining the presence or absence of a foreign metal substance in _ddc and a coil _{L p} voltage V of the drive power source _{(L p)} and the capacitor _{C p} voltage V _{(C p)} Reliability is improved by using a combination of the method of determining the presence or absence of a metal foreign matter based on V (L _p ) / V (C _p ).

(8) The present invention switches the primary L _p -C _p resonator composed of the coil L _p and the capacitor C _p connected in series and the DC power (V _ddc , I _ddc ) at the drive frequency ω _dr to a driving power source for driving the primary _L p -C _p resonator, when the drive of the primary _L p -C _p resonator, enter the midpoint voltage _{V c} between the coil _{L p} and the capacitor _{C p,} the driving frequency omega _dr , A multiplexer for extracting the first ½ period voltage waveform and the second ½ period voltage waveform of the midpoint voltage V _c , the extracted first ½ period voltage waveform and the second Smoothing means for smoothing the half-period voltage waveform to obtain the first smoothed value and the second smoothed value, and the coil L _p from the first smoothed value and the second smoothed value. Voltage ratio V between voltage V (L _p ) and voltage V (C _p ) between capacitors C _p Voltage ratio calculating means for calculating (L _p ) / V (C _p ), output impedance calculating means for calculating the output impedance Z _ddc of the drive power supply, and the calculated voltage ratio V (L _p ) / V (C _p ) is compared with a predetermined first threshold value, and the calculated output impedance Z _ddc of the drive power supply is compared with a predetermined second threshold value to determine the presence or absence of metallic foreign matter on the surface to be charged. And a wireless power transmission apparatus characterized by comprising a determination means for determining.

The method of determining the presence or absence of a metal foreign object with the output impedance Z _ddc of the drive power supply is simple in itself, but considering that the output impedance Z _ddc of the drive power supply also depends on the terminal load, it is difficult to set the threshold value. There is also. However, according to the present invention, the voltage ratio of the output impedance _Z method of determining the presence or absence of a foreign metal substance in _ddc and a coil _{L p} voltage V of the drive power source _{(L p)} and the capacitor _{C p} voltage V _{(C p)} Reliability is improved by using a combination of the method of determining the presence or absence of a metal foreign matter based on V (L _p ) / V (C _p ).

  According to the present invention, since there are few measurement items, there is an effect that measurement errors can be reduced. Moreover, since it can determine using the general measurement parameter of a power transmission device, there exists an effect that an accurate determination can be performed by a simple method, without increasing cost. In addition, unlike the prior art, since it is possible to perform measurement at an arbitrary timing, there is an effect that it is possible to quickly determine the presence or absence of a metallic foreign object. Furthermore, since the parameter used for the determination does not have temperature characteristics, there is an effect that it is possible to perform a highly accurate determination without performing correction processing for the temperature even in a wide temperature range.

It is a figure which shows the electrical constitution of the wireless power transmission apparatus which concerns on the 1st Embodiment of this invention. It is a figure which shows typically the reduction | decrease of the magnetic flux resulting from a metal foreign material. It is a figure which shows the electrical constitution of the wireless power transmission apparatus which concerns on the modification of the 1st Embodiment of this invention. It is a figure which shows the electrical constitution of the wireless power transmission apparatus which concerns on the 2nd Embodiment of this invention. It is a figure which shows the voltage waveform of the midpoint voltage Vc which concerns on the 2nd Embodiment of this invention. It is a figure which shows the electrical constitution of the wireless power transmission apparatus which concerns on the 3rd Embodiment of this invention. It is the figure which isolate | separated the midpoint voltage Vc by the multiplexer which concerns on the 3rd Embodiment of this invention into the semicircle of a positive direction, and the semicircle of a negative direction. It is a figure which shows the electrical constitution of the wireless power transmission apparatus which concerns on the 4th Embodiment of this invention. It is a diagram showing a measurement example of a V _{L /} V _C according to the first embodiment of the present invention. It is the figure which showed the example of measurement of _{Zdcc which concerns} on the 4th Embodiment of this invention. It is the figure which showed the detection method of the metal foreign material which concerns on a prior art example.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Note that the constituent elements in the present embodiment can be appropriately replaced with existing constituent elements and the like, and various variations including combinations with other existing constituent elements are possible. Therefore, the description of the present embodiment does not limit the contents of the invention described in the claims.

<First Embodiment>
A wireless power transmission apparatus according to this embodiment will be described with reference to FIGS. 1 and 2.

  FIG. 2 shows an AC magnetic field H generated by applying an AC current i to the coil, an eddy current i (eddy) generated in the metal plate by the AC magnetic field H, and a magnetic field H (eddy) generated by the eddy current. The directional relationship is shown. As can be seen from this figure, the magnetic field H (eddy) due to the eddy current i (eddy) always occurs so as to cancel the change in the magnetic field H due to the original coil current i. For this reason, the effective magnetic field generated by the coil is reduced, and the inductance Lp of the coil is apparently reduced. Therefore, if it is possible to detect a change in the inductance Lp of the coil, it is possible to detect a metal foreign object. The present invention uses the above reduction to determine the presence or absence of a metallic foreign object on the placement surface of the device to be charged by a simple method.

<Configuration of wireless power transmission device>
As shown in FIG. 1, the wireless power transmission device 10 according to the present embodiment includes a full-bridge inverter switching unit 100, a power source 200, a DDC (DC / DC converter) 300, and gate drive circuits 400 and 500. Has been.

  The power source 200, the DDC (DC / DC converter) 300, and the full bridge inverter switching unit 100 are connected in series, and the output of the DDC (DC / DC converter) 300 whose output voltage is variable by the control signal VAR is full bridge inverter switching. It is supplied as a driving power source for the unit 100.

  The full-bridge inverter switching unit 100 includes p-channel FETs (p-FET (1), p-FET (2)) 101A and 101B, and n-channel FETs (n-FET (1), n-FET ( 2)) 102A, 102B, capacitor (Cp) 103, coil (Lp) 104, first voltage detector 105, second voltage detector 106, voltage ratio calculator 107, and determiner 108 And a threshold storage unit 109.

  The upper arm FET (p-FET (1) 101A) and the lower arm FET (n-FET (1) 102A) are connected to each other in series to form a first inverter unit, while the upper arm FET (p-FET) (2) 101B) and the lower arm FET (n-FET (2) 102B) are connected in series to form a second inverter unit, and the first inverter unit and the second inverter unit are connected to GND. It is connected.

  The full-bridge inverter switching unit 100 using these FETs is provided with two output terminals, and a primary Lp-Cp resonator is formed between the output terminals by a capacitor (Cp) 103 and a coil (Lp) 104. Has been.

The p-channel FETs (p-FET (1), p-FET (2)) 101A, 101B and the n-channel FETs (n-FET (1), n-FET (2)) 102A, 102B are: The upper arm FET (p-FET (1) 101A) and the lower arm FET (n-FET (1) 102A) are connected to the gate drive circuits 400 and 500 and are output by the gate drive circuits 400 and 500. ) And the upper arm FET (p-FET (2) 101B) and the lower arm FET (n-FET (2) 102B) are alternately turned ON / OFF, and the primary Lp-Cp resonator is driven to oscillate. . The driving method of this embodiment, a constant driving frequency, the output voltage is variable DDC, exemplifies the method for controlling the output AC magnetic field of the power transmission coil L _p.

The first voltage detector 105 detects the voltage V (C _p ) between the capacitors C _p when driving the primary Lp-Cp resonator. The second voltage detection unit 106 detects the voltage V (L _p ) between the coils L _p when driving the primary Lp-Cp resonator. The voltage ratio calculation unit 107 includes the voltage V (C _p ) between the capacitors C _p detected by the first voltage detection unit 105 and the voltage V (L _p ) between the coils L _p detected by the second voltage detection unit 106. Voltage ratio V (L _p ) / V (C _p ) is calculated. The determination unit 108 determines the presence / absence of a metallic foreign object on the surface to be charged from the calculated voltage ratio V (L _p ) / V (C _p ) and a predetermined threshold value. The threshold storage unit 109 stores and holds a predetermined threshold used for determination.

In general, the circuit, it is difficult to measure the inductance L _p of the power transmission coil directly. Therefore, in the present embodiment, a method of indirectly measuring the change in the inductance Lp of the power transmission coil from the ratio V (L _p ) / V (C _p ) between the power transmission coil L _p and the resonance capacitor C _p end voltage is used. In FIG. 1, the ratio V (L _p ) / V (C _p ) between the power transmission coil L _p connected in series and the resonance capacitor C _p end voltage is expressed by Equation 1.

Here, ω _dr is the drive angular frequency of the inverter. Further, the resonance capacitor Cp does not depend on the presence or absence of a load or a metal foreign object, and is always constant. Therefore, when driving at the inverter frequency and controlling the output AC magnetic field with the output voltage V _ddc of the _{DDC 300} , The inductance L _p of the power transmission coil is a function of the ratio V (L _p ) / V (C _p ) between the power transmission coil L _p connected in series and the resonance capacitor C _p end voltage.

That is, when the metal foreign object approaches the power transmission coil L _p , L _p decreases, and the ratio V (L _p ) / V (C _p ) between the power transmission coil L _p and the resonance capacitor C _p end voltage decreases. Therefore, when the ratio V (L _p ) / V (C _p ) between the power transmission coil L _p and the resonance capacitor C _p end voltage is significantly reduced to some extent, the presence of a metal foreign object on the placement surface of the device to be charged is estimated. be able to. Since the effective inductance L _p of the power transmission coil depends on the coupling coefficient with the secondary coil Ls, the output load, and the like, the ratio between the power transmission coil L _p and the resonance capacitor C _p end voltage for determining the presence or absence of metal foreign matter. The threshold value of V (L _p ) / V (C _p ) needs to be determined based on statistical data under various conditions.

FIG. 9 shows, for example, the ratio V (L _p ) / V (C _p ) between the power transmission coil L _p and the resonance capacitor C _p end voltage when the power received by the power receiver is in the range of 0.2 W to 5 W. It is a thing. According to this statistical data, if the threshold value of the ratio V (L _p ) / V (C _p ) between the power transmission coil L _p and the resonance capacitor C _p end voltage is set to 1.28, the placement of the device to be charged is ensured. It is possible to detect the presence or absence of metallic foreign matter on the surface.

As described above, according to the present embodiment, the ratio V (L _p ) / V (C _p ) between the power transmission coil L _p and the resonance capacitor C _p end voltage is obtained, and the degree of change is detected. Accordingly, by detecting the degree of change in the indirect power transmission coil L _p, it is possible to estimate the presence of a metal foreign object in the mounting surface of the charging device by a simple method.

<Modification of First Embodiment>
A wireless power transmission apparatus according to this modification will be described with reference to FIG.
In the first embodiment, the method of controlling the output AC magnetic field with the DDC having a variable output voltage with the drive frequency constant is described as an example. However, in this modification, the frequency of the drive signal is varied to transmit power. illustrates a method for controlling the output AC magnetic field from the coil L _p is described.

<Configuration of wireless power transmission device>
As shown in FIG. 3, the wireless power transmission device 10 according to the present embodiment includes a full bridge inverter switching unit 110, a power supply 200, and gate drive circuits 410 and 510.

  The full-bridge inverter switching unit 110 includes p-channel FETs (p-FET (1), p-FET (2)) 101A and 101B, and n-channel FETs (n-FET (1), n-FET ( 2)) 102A, 102B, capacitor (Cp) 103, coil (Lp) 104, first voltage detection unit 105, second voltage detection unit 106, voltage ratio calculation unit 117, and determination unit 118 And a threshold storage unit 119. In addition, about the component which attaches | subjects the same code | symbol as 1st Embodiment, since it has the same function, the detailed description is abbreviate | omitted.

The voltage ratio calculation unit 117 calculates V (L _p ) / (V (C _p ) * ω _{dr ′} ² ) from the detected voltage V (L _p ) between the coils L _p and voltage V (C _p ) between the capacitors C _p. Is calculated. The determination unit 118 determines the presence / absence of a metal foreign object on the surface to be charged from the calculated voltage ratio V (L _p ) / (V (C _p ) * ω _{dr ′} ² ) and a predetermined threshold value. . The threshold storage unit 119 stores and holds a predetermined threshold used for determination.

  The gate drive circuits 410 and 510 are configured to receive an upper arm FET (p-FET (1) 101A), a lower arm FET (n-FET (1) 102A), and a gate drive signal output based on the variable frequency drive signal. The upper arm FET (p-FET (2) 101B) and the lower arm FET (n-FET (2) 102B) are alternately turned ON / OFF to drive the primary Lp-Cp resonator in oscillation.

Specifically, in this case, since the drive frequency is variable, in Equation 1, the change in the inductance L _p is obtained by the function of Equation 2, and the ratio V (L of the power transmission coil L _p and the resonance capacitor C _p end voltage is obtained. By measuring _p ) / V ( _Cp ), it is possible to estimate the presence of a metal foreign object on the placement surface of the device to be charged.

  In the first embodiment and the first modified embodiment described above, the duty ratio of the drive signal is constant. However, the present invention is not limited to this, and the output power is controlled by making the duty ratio of the drive signal variable. You may do it.

<Second Embodiment>
A wireless power transmission apparatus according to this embodiment will be described with reference to FIGS. 4 and 5. In the present embodiment, when driving the primary Lp-Cp resonator acquires a voltage waveform of the midpoint voltage V _C of the primary Lp-Cp resonator, to detect the peak voltage, the power transmission coil L obtained thereby Presence of metallic foreign matter on the mounting surface of the device to be charged is estimated from the ratio of the peak value of the ratio V (L _p ) / V (C _p ) between the _p and the resonance capacitor C _p end voltage and the threshold value.

<Configuration of full bridge inverter switching unit>
As shown in FIG. 4, the full-bridge inverter switching unit 120 includes p-channel FETs (p-FET (1), p-FET (2)) 101A, 101B and n-channel FETs (n-FET (1)). , N-FET (2)) 102A, 102B, capacitor (Cp) 103, coil (Lp) 104, peak voltage detection unit 121, voltage ratio calculation unit 122, determination unit 123, and threshold storage unit 124. It consists of and. In addition, about the component which attaches | subjects the same code | symbol as 1st Embodiment, since it has the same function, the detailed description is abbreviate | omitted.

Peak voltage detector 121, when driving the primary _L p -C _p resonator monitors the midpoint voltage _{V c} between the coil _{L p} and the capacitor _{C p,} the peak value of the coil _{L p} voltage V _{(L p)} V _peak is detected. Voltage ratio calculating unit 122, the detected coil _{L p} voltage V _{(L p)} of the peak value _{V peak} and driving DC voltage _{V ddc} coil and a _{L p} voltage V _{(L p)} and the capacitor _{C p} voltage V ( calculating a voltage ratio _{V (L p) / V (} C p) and C _p). The determination unit 123 determines the presence / absence of a metal foreign object on the placement surface of the device to be charged from the calculated voltage ratio V (L _p ) / V (C _p ) and a predetermined threshold value. The threshold storage unit 124 stores and holds a predetermined threshold used for determination.

When driving the full bridge inverter switching unit 120, the waveform of the midpoint voltage V _c, as shown in FIG. 5, it varies from 1/2 period. In FIG. 4, when n-FET (1) 102A and p-FET (2) 101B are on, and n-FET (2) 102B and p-FET (1) 101A are off, the current is indicated by a solid arrow. It flows in the loop shown (here, referred to as positive direction). At this time, since the one end of the resonant capacitor _{C p} is the ground, the midpoint voltage _{V c} becomes equal to the terminal voltage V of _{C p (C p).} Conversely, when n-FET (2) 102B and p-FET (1) 101A are on and n-FET (1) 102A and p-FET (2) 101B are off, the current is in the negative direction indicated by the dotted arrow. It flows in the loop. At this time, since the one end of the power transmission coil L _p is grounded, the midpoint voltage V _c is equal to L _p of the end voltage V (L _p). As a result, the waveform of the midpoint voltage V _c of L _p -C _p is a combined waveform of V (L _p ) and V (C _p ) as shown in FIG. In other words, the step between V (L _p ) and V (C _p ) becomes the output voltage V _{ddc of the DDC} 300 at the inversion point every half cycle. Therefore, for example, if the peak value V _peak of the Vc waveform is measured using a peak hold circuit, the ratio of the peak values of V (L _p ) and V (C _p ) can be obtained from Equation 1, and this value is calculated in advance. By comparing with the determined threshold value, it is possible to estimate the presence of a metal foreign object on the placement surface of the device to be charged.

<Third Embodiment>
A wireless power transmission apparatus according to the present embodiment will be described with reference to FIGS. 6 and 7. In the present embodiment, when driving the primary Lp-Cp resonator obtains the midpoint voltage V _C of the voltage waveform of the primary Lp-Cp resonator, the acquired waveform in the waveform of each half cycle by the multiplexer After the separation, the respective waveforms are smoothed, and the ratio V (L _p ) / V (C _p ) between the power transmission coil L _p and the resonance capacitor C _p end voltage is obtained from the smoothed voltage value. The presence of the metallic foreign object on the mounting surface of the device to be charged is estimated from the ratio V (L _p ) / V (C _p ) between the L _p and the resonance capacitor C _p end voltage and the threshold value.

<Configuration of full bridge inverter switching unit>
As shown in FIG. 6, the full-bridge inverter switching unit 130 includes p-channel FETs (p-FET (1), p-FET (2)) 101A, 101B and n-channel FETs (n-FET (1)). , N-FET (2)) 102A, 102B, capacitor (Cp) 103, coil (Lp) 104, multiplexer 131, smoothing unit 132, voltage ratio calculation unit 133, determination unit 134, and threshold storage. Part 135. In addition, about the component which attaches | subjects the same code | symbol as 1st Embodiment, since it has the same function, the detailed description is abbreviate | omitted.

Multiplexer 131 is 1 when driving the primary _L p -C _p resonator, enter the midpoint voltage _{V c} between the coil _{L p} and the capacitor _{C p,} the driving frequency omega _dr, the midpoint voltage _{V c} first The / 2 cycle voltage waveform and the second 1/2 cycle voltage waveform are extracted.

The smoothing unit 132 smoothes the first ½ period voltage waveform and the second ½ period voltage waveform extracted by the multiplexer 131, and obtains the first smooth value and the second smooth value. To do. Voltage ratio calculating unit 133, and a first smoothing value and the second smoothed value, the coil _{L p} voltage V _{(L p)} and the capacitor _{C p} voltage V _{(C p)} a voltage ratio of V _{(L p} ) / V (C _p ) is calculated. The determination unit 134 determines the presence / absence of a metallic foreign object on the surface to be charged from the calculated voltage ratio V (L _p ) / V (C _p ) and a predetermined threshold value. The threshold storage unit 135 stores and holds a predetermined threshold used for determination.

Specifically, as shown in FIG. 7, the multiplexer 131 has three input terminals, and receives the midpoint voltage V _C of the primary Lp-Cp resonator from the first input terminal. For example, the gate drive signal gn (1) that is the output of the gate drive circuit 400 and the gate drive signal gn (2) that is the output of the gate drive circuit 500 are input from the three input terminals.

Then, V (L _p ) and V (C _p ) are separated at the timing of the drive signals gn (1) and gn (2) of the gate drive circuits 400 and 500. For example, when the gate drive signal gn (1)) is high and the gate drive signal gn (2) is low, the positive direction of the inverter operates and V _C output from the multiplexer 131 to the first channel is V (C _p ). On the other hand, when the gate drive signal gn (1)) is low and the gate drive signal gn (2) is high, the negative direction of the inverter operates and V _C output from the multiplexer 131 to the second channel is V ( L _p ). Accordingly, if the separated V (C _p ) and V (L _p ) are smoothed and measured by the microcomputer, the voltage ratio between the voltage V (L _p ) between the coils L _p and the voltage V (C _p ) between the capacitors C _{p is obtained.} V (L _p ) / V (C _p ) is obtained.

<Fourth Embodiment>
The wireless power transmission device according to the present embodiment will be described with reference to FIG. In this embodiment, when an eddy current loss is caused by a metal foreign object, the total load applied to the DDC 300 becomes heavier than when there is no metal foreign object. Presence of metallic foreign matter on the placement surface is estimated.

<Configuration of wireless power transmission device>
As shown in FIG. 8, the wireless power transmission device 10 according to the present embodiment includes a full bridge inverter switching unit 140, a power source 200, a DDC (DC / DC converter) 300, gate drive circuits 400 and 500, and an output. The impedance calculation unit 600, the determination unit 700, and the threshold storage unit 800 are configured.

The output impedance calculator 600 calculates the output impedance Z _ddc of the _{DDC 300} . The determination unit 700 determines the presence / absence of a metallic foreign object on the placement surface of the device to be charged based on the calculated output impedance Z _ddc of the DDC ₃₀₀ and a predetermined threshold value. The threshold storage unit 800 stores and holds a predetermined threshold used for determination.

As described above, when eddy current loss occurs due to the metal foreign object, the total load applied to the DDC 300 becomes heavier than when there is no metal foreign object, so that the output impedance Z _{ddc of the DDC 300} is significantly reduced. The output impedance Z _ddc of the DDC ₃₀₀ is calculated from the output voltage V _{ddc of the DDC 300} and the output current I _ddc using _Equation 3, and the metal foreign object on the surface to be charged is set from the calculated value and a predetermined threshold value. The presence or absence of is determined.

Note that since the output impedance Z _ddc of the _{DDC 300} also depends on the terminal load or the like, the threshold value of Z _ddc for determining the presence or absence of a metal foreign object needs to be determined based on statistical data under various conditions. For example, FIG. 10 shows statistical data when the power received by the power receiver is in the range of 1.5 W to 5 W. According to this data, if the threshold value of Z _ddc is 7.0Ω, it is possible to reliably determine the presence / absence of a metallic foreign object on the placement surface of the device to be charged.

  In addition, the method for detecting a metal foreign object in the first to fourth embodiments can achieve its effect by itself, but the method for detecting a metal foreign object in the first to third embodiments. And the detection method of the metal foreign object in the fourth embodiment can be used in combination to further improve the reliability of detection of the metal foreign object.

  The processing of the wireless power transmission apparatus is recorded on a recording medium readable by the computer system, and the program recorded on the recording medium is read into the wireless power transmission apparatus and executed, thereby executing the wireless power transmission apparatus of the present invention. Processing can be realized by software. The computer system here includes an OS and hardware such as peripheral devices.

  Further, the “computer system” includes a homepage providing environment (or display environment) if a WWW (World Wide Web) system is used. The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line.

  The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, what is called a difference file (difference program) may be sufficient.

  The embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to the embodiments, and includes designs and the like that do not depart from the gist of the present invention.

10; wireless power transmission device 100; full bridge inverter switching unit 110; full bridge inverter switching unit 101A; p-channel FET
101B; p-channel FET
102A; n-channel FET
102B; n-channel FET
103; Capacitor (Cp)
104; coil (Lp)
105; 1st voltage detection part 106; 2nd voltage detection part 107; Voltage ratio calculation part 108; Judgment part 109; Threshold storage part 117; Voltage ratio calculation part 118; Judgment part 119; Threshold storage part 121; Detection unit 122; Voltage ratio calculation unit 123; Determination unit 124; Threshold storage unit 131; Multiplexer 132; Smoothing unit 133; Voltage ratio calculation unit 134; Determination unit 135; Threshold storage unit 200; )
400; Gate drive circuit 410; Gate drive circuit 500; Gate drive circuit 510; Gate drive circuit 600; Output impedance calculation unit 700; Determination unit 800;

Claims (8)

A primary L _p -C _p resonator comprising a coil L _p and a capacitor C _p connected in series;
A driving power source for switching the DC power at a constant driving frequency ω _dr to drive the primary L _p -C _p resonator;
Voltage detection means for detecting a voltage V (L _p ) between the coils L _p and a voltage V (C _p ) between the capacitors C _p when driving the primary L _p -C _p resonator;
Voltage ratio calculation means for calculating a voltage ratio V (L _p ) / V (C _p ) from the detected voltage V (L _p ) between the coils L _p and voltage V (C _p ) between the capacitors C _p ;
Determining means for determining the presence or absence of a metallic foreign object on the placement surface of the device to be charged from the calculated voltage ratio V (L _p ) / V (C _p ) and a predetermined threshold;
A wireless power transmission device comprising: A primary L _p -C _p resonator comprising a coil L _p and a capacitor C _p connected in series;
A driving power _source for switching the DC power at the variable driving frequency ω _{dr ′} to drive the primary L _p -C _p resonator;
Voltage detection means for detecting a voltage V (L _p ) between the coils L _p and a voltage V (C _p ) between the capacitors C _p when driving the primary L _p -C _p resonator;
Voltage ratio calculation for calculating V (L _p ) / (V (C _p ) * ω _{dr ′} ² ) from the _detected voltage V (L _p ) between the coils L _p and voltage V (C _p ) between the capacitors C _p Means,
Determining means for determining the presence / absence of a metal foreign object on the surface to be charged from the calculated voltage ratio V (L _p ) / (V (C _p ) * ω _{dr ′} ² ) and a predetermined threshold;
A wireless power transmission device comprising: A primary L _p -C _p resonator comprising a coil L _p and a capacitor C _p connected in series;
A driving power source for switching the DC power (V _ddc , I _ddc ) at the driving frequency ω _dr to drive the primary L _p -C _p resonator;
When driving the primary L _p -C _p resonator, the midpoint voltage V _c between the coil L _p and the capacitor C _p is monitored, and the peak value V _peak of the voltage V (L _p ) between the coils L _p is detected. Voltage detection means;
From the detected peak value V _{peak of the} voltage V (L _p ) between the coils L _p and the drive DC voltage V _ddc , the voltage V (L _p ) between the coils L _p and the voltage V (C _p ) between the capacitors C _p Voltage ratio calculating means for calculating the ratio V (L _p ) / V (C _p );
Determining means for determining the presence or absence of a metallic foreign object on the placement surface of the device to be charged from the calculated voltage ratio V (L _p ) / V (C _p ) and a predetermined threshold;
A wireless power transmission device comprising: A primary L _p -C _p resonator comprising a coil L _p and a capacitor C _p connected in series;
A driving power source for switching the DC power at the driving frequency ω _dr to drive the primary L _p -C _p resonator;
During driving of the primary _L p -C _p resonator, enter the midpoint voltage _{V c} between the coil _{L p} and the capacitor _{C p,} the driving frequency omega _dr, the first half cycle of the midpoint voltage _{V c} A multiplexer that extracts the voltage waveform and the second half-cycle voltage waveform;
Smoothing means for smoothing the extracted first ½ period voltage waveform and the second ½ period voltage waveform, respectively, to obtain a first smooth value and a second smooth value;
From the smoothed value and the second smoothed value of the first, the coil _{L p} voltage V _{(L p)} and the capacitor _{C p} voltage V _{(C p)} a voltage ratio of _{V (L p) / V (} C p ) For calculating the voltage ratio,
Determining means for determining the presence or absence of a metallic foreign object on the placement surface of the device to be charged from the calculated voltage ratio V (L _p ) / V (C _p ) and a predetermined threshold;
A wireless power transmission device comprising: A primary L _p -C _p resonator comprising a coil L _p and a capacitor C _p connected in series;
A driving power source for switching the DC power (V _ddc , I _ddc ) at the driving frequency ω _dr to drive the primary L _p -C _p resonator;
Output impedance calculating means for calculating the output impedance Z _ddc of the drive power supply;
Determining means for determining the presence / absence of a metal foreign object on the mounting surface of the device to be charged from the calculated output impedance Z _ddc of the driving power source and a predetermined threshold;
A wireless power transmission device comprising: A primary L _p -C _p resonator comprising a coil L _p and a capacitor C _p connected in series;
A driving power source for switching the DC power (V _ddc , I _ddc ) at a constant driving frequency ω _dr to drive the primary L _p -C _p resonator;
Voltage detection means for detecting a voltage V (L _p ) between the coils L _p and a voltage V (C _p ) between the capacitors C _p when driving the primary L _p -C _p resonator;
Voltage ratio calculation means for calculating a voltage ratio V (L _p ) / V (C _p ) from the detected voltage V (L _p ) between the coils L _p and voltage V (C _p ) between the capacitors C _p ;
Output impedance calculating means for calculating the output impedance Z _ddc of the drive power supply;
The calculated voltage ratio V (L _p ) / V (C _p ) is compared with a predetermined first threshold value, and the calculated output impedance Z _ddc of the driving power supply is compared with a predetermined second threshold value. Determination means for determining the presence or absence of metallic foreign matter on the mounting surface of the device to be charged,
A wireless power transmission device comprising: A primary L _p -C _p resonator comprising a coil L _p and a capacitor C _p connected in series;
A driving power source for switching the DC power (V _ddc , I _ddc ) at the driving frequency ω _dr to drive the primary L _p -C _p resonator;
When driving the primary L _p -C _p resonator, the midpoint voltage V _c between the coil L _p and the capacitor C _p is monitored, and the peak value V _peak of the voltage V (L _p ) between the coils L _p is detected. Voltage detection means;
From the detected peak value V _{peak of the} voltage V (L _p ) between the coils L _p and the drive DC voltage V _ddc , the voltage V (L _p ) between the coils L _p and the voltage V (C _p ) between the capacitors C _p Voltage ratio calculating means for calculating the ratio V (L _p ) / V (C _p );
Output impedance calculating means for calculating the output impedance Z _ddc of the drive power supply;
The calculated voltage ratio V (L _p ) / V (C _p ) is compared with a predetermined first threshold value, and the calculated output impedance Z _ddc of the driving power supply is compared with a predetermined second threshold value. Determination means for determining the presence or absence of metallic foreign matter on the mounting surface of the device to be charged,
A wireless power transmission device comprising: A primary L _p -C _p resonator comprising a coil L _p and a capacitor C _p connected in series;
A driving power source for switching the DC power (V _ddc , I _ddc ) at the driving frequency ω _dr to drive the primary L _p -C _p resonator;
During driving of the primary _L p -C _p resonator, enter the midpoint voltage _{V c} between the coil _{L p} and the capacitor _{C p,} the driving frequency omega _dr, the first half cycle of the midpoint voltage _{V c} A multiplexer that extracts the voltage waveform and the second half-cycle voltage waveform;
Smoothing means for smoothing the extracted first ½ period voltage waveform and the second ½ period voltage waveform, respectively, to obtain a first smooth value and a second smooth value;
From the smoothed value and the second smoothed value of the first, the coil _{L p} voltage V _{(L p)} and the capacitor _{C p} voltage V _{(C p)} a voltage ratio of _{V (L p) / V (} C p ) For calculating the voltage ratio,
Output impedance calculating means for calculating the output impedance Z _ddc of the drive power supply;
The calculated voltage ratio V (L _p ) / V (C _p ) is compared with a predetermined first threshold value, and the calculated output impedance Z _ddc of the driving power supply is compared with a predetermined second threshold value. Determination means for determining the presence or absence of metallic foreign matter on the mounting surface of the device to be charged,
A wireless power transmission device comprising:

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