Patent Application
20160226311
1. Field of the Invention
This invention relates to a power transmission device, a power transmission and receiving device, a method for detecting power receiving device, a power receiving device detection program, and a semiconductor device that transmit or receive an electric power from a noncontact communication device. The present application claims priority based on Japanese Patent Application No. 2013-60646 filed in Japan on Mar. 22, 2013. The total contents of the patent application are to be incorporated by reference into the present application.
2. Description of Related Art
A noncontact communication technique using electromagnetic induction has been popularly applied to IC cards such as FeliCa (registered trademark), Mifare (registered trademark), and NFC (Near Filed Communication). In recent years, the noncontact communication technique has been also applied to a noncontact power charging (discharging) technique typified by Qi format and has been popularly used in wide ranges. In the field of the noncontact charging technique, in order to apply the noncontact communication technique to not only a mobile information terminal but also an electric automobile or the like, a technique which is called a magnetic resonance scheme and can transmit an electric power to a distant position has been actively developed. In fact, even in the electromagnetic induction scheme or a magnetic resonance scheme, since an electric power is transmitted or received by using a resonance circuit, the electromagnetic induction scheme and the magnetic resonance scheme can be equally handled.
Also in noncontact communication performed between a noncontact IC card and a reader/writer, as in noncontact charging which transmits or receives a relatively high electric power, the electric power must be transmitted from a primary side (reader/writer or power transmission device) to a secondary side (noncontact IC card or power receiving device). In this case, the primary side recognizes whether the party (IC card or power receiving device) to which an electric power should be transmitted is present on the secondary side. Furthermore, even though the other party is present on the secondary side, the primary side must recognize whether other party is a party to which an electric power should be transmitted. For example, as shown in
In this case, since the device on the primary side does not know when the device or apparatus on the secondary side enters a communication area on the primary side, the device on the primary side generates and always transmits signals (called polling signals) to detect the device or apparatus on the secondary side at predetermined intervals.
When polling is regularly performed, in a mobile phone, a smart phone, or the like operated with a battery, a power consumption increases. For this reason, it is strongly requested that a device or apparatus on the secondary side should be detected at a minimum power consumption.
Patent document 1: Japanese Patent Application Laid-Open No. 2009-033782
In order to suppress a power consumption in a polling operation, methods such as a method of elongating a polling cycle and a method of lowering an output of a transmission electric power for polling are conceived. However, when the polling cycle is elongated, a detection time becomes long. When the transmission electric power is lowered, a detection area becomes small.
When the device or apparatus on the secondary side is tried to be detected without waiting a response from the secondary side, a transmission time per polling can be shortened.
When the device or apparatus on the secondary side enters a communication area of the device on the primary side, magnetic coupling between the primary side and the secondary side occurs, a current flowing in an antenna on the primary side may decrease, or a current waveform changes. However, even though a foreign object such as a metal plate is present on the secondary side, since magnetic coupling occurs, a change in waveform on the primary side occurs. In this manner, the device on the primary side must be prevented from recognizing a party to which an electric power should not be transmitted as a “foreign object” and from transmitting the electric power to the party.
For example, in Patent document 1 discloses a technique that detects a foreign object such as a metal on the secondary side by using the characteristic of the change in current on the primary side as described above. However, in this method, the configuration of a circuit that acquires current waveforms and make a determination to detect a difference between current waveforms flowing in the antenna at frequencies between a resonance frequency on the primary side and an operation frequency in a normal operation is disadvantageously complicated. The circuit is further complicated to correct a fluctuation or a variation in resonance frequency the device or apparatus placed on the secondary side has, and the resonance frequencies are difficult to be adjusted.
Thus, it is an object of the present invention to provide a power transmission device, a power transmission and receiving device, a method for detecting power receiving device, a power receiving device detection program, and a semiconductor device which can accurately discriminate a device or apparatus placed on a secondary side from an foreign object without adding a complex circuit.
As a means to solve the above problem, a power transmission device according to an embodiment of the present invention is a power transmission device that transmits an electric power to a power receiving device in a noncontact state by using a resonance circuit. This power transmission device includes a control unit that sets a drive frequency of a signal for driving the resonance circuit, a drive unit that drives the resonance circuit at three or more drive frequencies on the basis of a setting of the control unit, and a drive waveform detecting unit that detects a drive waveform of the resonance circuit. The control unit sets the three or more drive frequencies, compares signal data at the drive frequencies detected by the drive waveform detecting unit with each other, and detects a power receiving device on the basis of the comparison result.
A power transmission and receiving device according to another embodiment of the present invention is a power transmission and receiving device that transmits an electric power to a power receiving device or another power transmission and receiving device in a noncontact state by using a resonance circuit.
The power transmission and receiving device includes a control unit that sets a drive frequency of a signal for driving a resonance circuit, a drive unit that drives the resonance circuit at three or more drive frequencies on the basis of a setting of the control unit, and a drive waveform detecting unit that detects a drive waveform of the resonance circuit. The control unit sets the three or more drive frequencies, compares signal data at the drive frequencies detected by the drive waveform detecting unit with each other, and detects a power receiving device or another power transmission and receiving device on the basis of the comparison result.
A method for detecting power receiving device according to still another embodiment of the present invention is a method for detecting power receiving device that detects, when an electric power is transmitted from a power transmission device to the power receiving device in a noncontact state by using a resonance circuit, the presence/absence of a power receiving device. In the method for detecting power receiving device, a control unit sets a drive frequency of a signal for driving a resonance circuit, a drive unit, on the basis of a setting of the control unit, drives the resonance circuit at three or more drive frequencies, and a drive waveform detecting unit detects a drive waveform of the resonance circuit. The control unit sets three or more drive frequencies, compares signal data at the drive frequencies detected by the drive waveform detecting unit with each other, and detects a power receiving device on the basis of the comparison result.
a power receiving device detection program according to still another embodiment of the present invention is a received power adjustment program for a noncontact charging power receiving device including a storage unit in which a program is stored and a control unit having a processing unit that develops and executes the stored program, and is a power receiving device detection program that, when an electric power is transmitted from a power transmission device to a power receiving device in a noncontact state by using a resonance circuit, detects the presence/absence of a power receiving device. The power receiving device detection program includes the step of setting a drive frequency of a signal for driving a resonance circuit by the control unit, the step of driving the resonance circuit at three or more drive frequencies on the basis of a setting of the control unit by a drive unit, the step of detecting a drive waveform of the resonance circuit by a drive waveform detecting unit. The control unit sets three or more drive frequencies, compares signal data at the drive frequencies detected by the drive waveform detecting unit with each other, and detects a power receiving device on the basis of the comparison result.
A semiconductor device according to still another embodiment of the present invention includes a storage unit in which a power receiving device detection program is stored.
The semiconductor device according to still another embodiment of the present invention further includes a control unit that develops and executes a received power adjustment program.
According to the present invention, since the resonance circuit is driven at the three or more drive frequencies, a difference between a drive current waveform obtained when a power receiving device is disposed and a drive current waveform obtained when a foreign object such as a metal is disposed is clear, and the power receiving device can be easily detected within a short period of time.
Modes for executing the present invention will be described below in detail with reference to the accompanying drawings. The present invention is not limited to only the following embodiments, and can be variously changed without departing from the spirit and scope of the present invention as a matter of course. The explanation will be made in the following order.
1. Configuration of power transmission device
2. Principle and operation of power transmission device
2-1. Difference between frequency characteristics of antenna currents in the presence of power receiving device and in the presence of foreign object
2-2. Detection of difference between frequency characteristics of antenna currents in weak coupling
2-3. Resonance frequency deviation on power receiving device side
2-4. Detection of difference between frequency characteristics of antenna currents when a coupling coefficient changes
2-5. Setting of detection pattern
3. Method for detecting power receiving device
4. Configuration of power transmission and receiving device
1. Configuration of Power Transmission Device
As shown in
The transmission and receiving unit 3 as shown in
More specifically, as shown in
As shown in
When the value of a control voltage is changed, a DC voltage applied across both the ends of the variable capacitor (C2) 11b, and, accordingly, the capacitance changes. The capacitance of the variable capacitor (C2) 11b, as shown in
In order to change the capacitance of the resonance capacitor to change the resonance frequency of the antenna unit 3, as shown in
The inverter unit 2 has a rectifying and smoothing circuit which receives an electric power from the commercial power supply 6 to temporarily convert the electric power into a DC, drives the primary side antenna unit 3a with, preferably, a sine wave having a drive frequency set by the control unit 5a using the converted DC. The circuit configuration of the drive unit can be arbitrarily set as a half-bridge or full-bridge configuration or the like depending on an electric power for driving the antenna unit 3a, and transistors corresponding to voltages applied or currents flowing in the antenna unit 3a may be set and combined to each other.
The waveform monitor 4 measures the current flowing in the antenna unit 3a, and, preferably holds a peak value of the current. As the measurement of the current, a voltage may be measured by a resistor inserted in series with a coil of the antenna unit 3a or may be measured by a hall element or the like. Another known means may be used. The acquired peak current value is preferably converted into a digital signal by an A/D converter, and may be stored in a storage unit 5b on the basis of an instruction of the control unit 5a. The digital signal may be temporarily stored in a storage unit included in the waveform monitor unit 4 itself. With respect to the characteristics of the resonance circuit including the antenna unit 3a obtained by the waveform monitor unit 4, the peak value of the current, an actual value, and the like can be arbitrarily set. Not only a measurement of a current value, but also acquisition of the peak value of a voltage, an actual value, or the like may be performed as a matter of course.
The control system unit 5 preferably includes the storage unit 5b in which a program expressing an operation procedure of the power transmission device 1 is written, and the control unit 5a that controls an operation of the power transmission device 1 according to the procedure in the storage unit 5b. The control unit 5a is a CPU (Central Processing Unit) or a micro-controller. The storage unit 5b may be a mask ROM mounted on, for example, a micro-controller, or may be an EPROM, an EEPROM, or the like. The storage unit 5b is not limited to these memories.
The control unit 5a configuring the control system unit 5 sets a drive frequency for driving the antenna unit 3a to the inverter unit 2 according to the program stored in the storage unit 5b. The inverter unit 2 oscillates in a sine wave having the set drive frequency to drive the antenna unit 3a. When the power receiving device 50 is in a communication area of the power transmission unit 1, a current flowing in the antenna unit 3a changes due to the presence of the resonance circuit configured by the secondary side antenna unit 52a, and the change is acquired by the waveform monitor unit 4. Alternatively, when a foreign object such as a metal is present at the position of the power receiving device 50, a peak value of the current is acquired by the waveform monitor unit 4.
In the control system unit 5, the control unit 5a changes the drive frequency according to the program stored in the storage unit 5b, and acquisition of peak values of currents in the antenna unit 3a to the changed drive frequencies is repeated predetermined times to acquire a frequency characteristics of currents flowing in the resonance circuit. The peak current values to the acquired drive frequencies are compared with each other to obtain a detection pattern. The detection pattern is compared with a detection pattern of peak current values to the presence and absence of a power receiving device set in the storage unit 5b or the like in advance to cause the control unit 5a to determine the presence and absence of the power receiving device.
2. Principle and Operation of Power Transmitting Device
A principle to determine the presence/absence of the power receiving device by the power transmission device according to an embodiment of the present invention will be described below in some cases together with the operation of the power transmission device.
2-1. Difference Between Frequency Characteristics of Antenna Currents in the Presence of Power Receiving Device and in the Presence of Foreign Object
On the other hand, as shown in
M=K·(L1×L2)0.5
When the value K increases, the coupling strength between the primary side and the secondary side becomes strong. As shown in
In this manner, when it is determined whether the frequency characteristic of a current flowing in the primary side resonance circuit is a single-peaked characteristic or a double-peaked characteristic, it can be detected whether the power receiving device is disposed on the secondary side or a metal or the like except for the power receiving device is disposed.
More specifically, in order to acquire a frequency characteristic of a current flowing in the resonance circuit, as shown in
2-2. Detection of Difference Between Frequency Characteristics of Antenna Current in Weak Coupling
As described above, a frequency characteristic of a current flowing in the antenna unit 3a configuring the primary side resonance circuit is measured to determine whether the frequency characteristic has one peak (single-peaked characteristic) or two peaks (double-peaked characteristic), so that the presence and absence of a power receiving device can be detected. However, as shown in
Resonance conditions on the primary side are changed to change resonance frequencies of resonance circuits. Frequency characteristics of currents flowing in the resonance circuits having resonance frequencies are acquired. In this manner, when the resonance circuit of the secondary side power receiving device 50 has a resonance frequency equal to the original resonance frequency f0 on the primary side, even though the coupling is weak, electric power transmission is performed at about the resonance frequency f0. A current flowing in the primary side resonance circuit is smaller than a current value obtained at another frequency.
In the frequency characteristic of the current i flowing in the resonance circuit having the resonance frequency f0, the current i (f0) comes to close to the maximum value when the frequency is f0. Thus, a magnitude relation between i1 (f0), a current i (f01) obtained when the frequency is f01, and a current i (f02) obtained when the frequency is f02 is given by:
i(f0)>i(f01),i(f02) (1)
In the frequency characteristic of the current i1 flowing in the resonance circuit having the resonance frequency f01, the current i1 (f01) comes close to the maximum value when the frequency is f01. Thus, a magnitude relation between i1 (f0), i1 (f01), and i1 (f02) is given by:
i1(f01)>i1(f01)>i1(f02) (2)
Similarly, in the frequency characteristic of the current i2 flowing in the resonance circuit having the resonance frequency f02, the current i2 (f02) comes close to the maximum value when the frequency is f02. Thus, a magnitude relation between i2 (f0), i2 (f01), and i2 (f02) is given by:
i2(f01)<i2(f0)<i2(f02) (3)
Since the circuit on the secondary side has no frequency characteristic, the maximum values of the currents in above three frequency characteristics are almost equal to each other.
i(f0)≈i1(f01)≈i2(f02) (4)
In the frequency characteristic of the current i flowing in the resonance circuit having the resonance frequency f0, the same result as that in the case in
Similarly, with respect to the frequency characteristic of the current i1 flowing in the resonance circuit having the resonance frequency f01, a magnitude relation between the current values i1 (f0), i1 (f01), and i1 (f02) at the frequencies f0, f01, and f02 respectively is the relation given by the expression (2).
Also with respect to the frequency characteristic of the current i2 flowing in the resonance circuit having the resonance frequency f02, a magnitude relation between the current values i2 (f0), i2 (f01), and i2 (f02) at the frequencies f0, f01, and f02 respectively is the relation given by the expression (3).
On the other hand, a magnitude relation between the peak values i (f0), i1 (f01), and i2 (f02) of the currents at the respective frequencies is given by:
i(f0)<i1(f01),i2(f02) (5)
Since the resonance frequency f0 of the secondary side resonance circuit is equal to the resonance frequency f0 of the primary side resonance circuit, the peak value of the current in the primary side resonance circuit decreases because electric power transmission is performed from the primary side to the secondary side at the frequency f0 to show that the peak value of the current increases when the frequency is deviated from the resonance frequency f0 on the secondary side.
As described above, three drive frequencies are set for the resonance circuits having three different resonance frequencies to acquire frequency characteristics. When the maximum values of the currents in the resonance circuits are not changed, it can be determined that a foreign object such as a metal is disposed on the secondary side without disposing the power receiving device 50 on the secondary side.
2-3. Deviation of Resonance Frequency on Power Receiving Device Side
Although a noncontact IC card may be disposed on the secondary side (power receiving device side), a noncontact IC card may be placed on an IC card or the like having a communication format different from that of the noncontact IC card, and may be frequently carried together with a metal object which shields a magnetic field. In consideration of this, the resonance frequency of the resonance circuit is set to a higher value in many cases.
As described above, when the resonance frequency of the secondary side resonance circuit is equal to the resonance frequency on the primary side, electric power transmission occurs. For this reason, when coupling between the primary side and the secondary side is strong (for example, K is 0.2 or more), the frequency characteristic of a current flowing in the primary side resonance circuit is considerably different from that obtained when a foreign object such as a simple metal is disposed. Even though the coupling between the primary side and the secondary side is weak to obtain a small coupling coefficient (for example, K is about 0.1), the resonance frequency of the primary side resonance circuit is made different from the original resonance frequency to acquire a frequency characteristic of the current, so that a difference between the frequency characteristic and the frequency characteristic obtained when the foreign object is disposed.
Furthermore, in the present invention, even though a noncontact IC card having a resonance frequency which is set to a higher value due to the above circumstances is disposed on the secondary side, a difference between the frequency characteristic and the frequency characteristic obtained when the foreign object such as a metal is disposed is generated to make it possible to achieve the detection.
The secondary side resonance frequency was set to 16 MHz, the primary side resonance frequency was set to 13.56 MHz as in the cases in
With respect to the frequency characteristic of the current i1 flowing in the resonance circuit having the resonance frequency f01, a magnitude relation between the current values i1 (f0), i1 (f01), and i1 (f02) at the frequencies f0, f01, and f02 respectively is the relation given by the above expression (2).
Also with respect to the frequency characteristic of the current i2 flowing in the resonance circuit having the resonance frequency f02, a magnitude relation between the current values i2 (f0), i2 (f01), and i2 (f02) at the frequencies f0, f01, and f02 respectively is the relation given by the expression (3).
On the other hand, a magnitude relation between the maximum values i (f0), i1 (f01), and i2 (f02) of the currents at the respective frequencies is given by:
I1(f01)>i(f0)>i2(f02) (6)
Since the frequencies f01, f0, and f02 are lower than a resonance frequency f0′ on the secondary side, it is shown that the coupling strengths between the primary side and the secondary side increase in the order of the magnitude relation given by expression (6) and the peak value of the current on the primary side tends to lower.
When the resonance frequency of the device or apparatus on the secondary side is set to a frequency relatively lower than the resonance frequency on the primary side, as in the case described above, the coupling strengths between the primary side and the secondary side decrease in the order of the magnitude relation given by expression (6). For this reason, the peak value of the current on the primary side tends to increase.
2-4. Detection of Difference Between Frequency Characteristics of Antenna Currents when Coupling Coefficient Changes
In consideration of utility forms of a noncontact communication module mounted to achieve a noncontact IC card or the functions of the noncontact IC card with a mobile phone or the like, distances between these devices or apparatuses and a power transmission device or a transmission device such as a reader/writer may change with time. In general, since coupling is often performed while a noncontact IC card or the like is brought close to the reader/writer. At this time, since the distance between the primary side and the secondary side is shortened with time, the coupling coefficient increases with time.
As shown in
In detection of a difference between frequency characteristics described in 2-1, 2-2, and the like with respect to the coupling coefficients changed as described above, an order (order of measurements) of settings of frequencies corresponding to current values to be measured must be noted.
As shown in
i(f0,K=0.1)>i(f01,K=0.2)>i(f02,K=0.4) (7)
Since a magnitude relation between i (f01, K=0.2) and i (f02, K=0.4) is given by i (f02, K=0.2)>i (f01, K=0.4) when the frequency f02 is measured first, in general, the following expression is obtained.
i(f0,K=0.1)>i(f0x,K>0.1)(x=1 or 2) (7′)
As indicated by a broken line graph and a chain line graph in
Thus, when the current value at the primary side resonance frequency f0 is measured at the last, the frequency characteristic of the current value in the primary side resonance circuit can be detected.
As shown in
2-5. Setting of Detection Pattern
By using the principle described above, a magnitude relation between frequencies of current values in the primary resonance circuit is patterned to make it possible to determine the presence and absence of a device or apparatus on the secondary side.
As described in 2-1, when a foreign object such as a metal is disposed on the secondary side, since the foreign object does not have a frequency characteristic, the pattern P5 having a flat tendency as shown in
When a power receiving device or apparatus having a resonance circuit having the resonance frequency f0 equal to the resonance frequency f0 of the primary side resonance circuit is disposed on the secondary side, the pattern P4 having a convex-downward tendency as shown in
When the number of frequencies at which current values are acquired is increased or changed in an analog manner to acquire frequency characteristics of the current values in an analog manner, more detailed pattern setting can be achieved as a matter of course.
When a coupling strength is relatively high, i.e., when the coupling coefficient K is about 0.2 or more, the patterns P4 and P5 of the two types described above are detected to make it possible to detect a power receiving device or apparatus or a foreign object. However, when the coupling strength is low, i.e., the coupling coefficient K is lower than 0.2, the system must be further devised. As described in 2-2 and 2-3 described above, the resonance frequency of the primary side resonance circuit is changed, currents flowing in the resonance circuit having different resonance frequencies must be measured and patterned. Since patterning is performed by further combining the patterns in
As described above, when combinations between the patterns P1 to P5 showing the tendencies of the frequency characteristics of the currents flowing in the resonance circuit and patterns obtained when the resonance frequencies of the primary side resonance circuit are changed are set as weak coupling detection patterns, it can be detected independently of coupling coefficients whether a power receiving device or apparatus is disposed on the secondary side.
3.3. Method for Detecting Power Receiving Device
The control unit 5a of the power transmission device 1, in step S1, sets the power transmission device 1 in an antenna detection mode. In the antenna detection mode, an electric power is not transmitted from the power transmission device 1 to the power receiving device 50 (or a foreign object such as a metal), and an operation to detect the presence and absence of the power receiving device on the secondary side is performed as described below. In a detection period for the secondary side power receiving device, a normal electric power is transmitted from the primary side when a foreign object such as a metal is present, the metal generates heat. For this reason, an antenna detection mode for performing detection on the secondary side is preferably set after the transmission of the electric power is stopped. Since the antenna detection mode which executes short-time polling, the antenna detection mode is preferably intermittently executed.
The control unit 5a, in step S2, sets the resonance frequency f0 (for example, f0=13.56 MHz) to the transmission and receiving unit 3 configuring the resonance circuit.
The control unit 5a sets a drive frequency to f01 (for example, f01=12.56 MHz) lower than the resonance frequency f0 by Δf, and acquires a current value at the frequency f01. The drive frequency is set to f02 (for example, f02=14.56 MHz) higher than the resonance frequency by Δf, and a current value at the frequency f02 is acquired. Furthermore, a current value obtained when the drive frequency is f0 is acquired. The acquired current value is preferably stored in the storage unit 5b as a detection pattern 1 in association with the drive frequency. The control unit 5a determines whether the detection pattern 1 corresponds to any one of the patterns P1 to P5 in
The control unit 5a determines, in step S4, whether the acquired pattern 1 is matched with the convex-downward pattern P4 (
The control unit 5a, when the power receiving device or apparatus cannot be detected in step S4, changes a constant of the primary side resonance circuit and changes the resonance frequency into f01. With respect to the resonance frequency f01, as in step S3, current values are acquired in units of drive frequencies, and a detection pattern 2 obtained by associating the current values with the drive frequencies is acquired. One of
Furthermore, the control unit 5a, in step S7, changes the resonance frequency of the resonance circuit into f02, as in steps S3 and S6, and acquires frequency characteristics of currents flowing in the resonance circuit having the resonance frequency f02 as current values in units of drive frequencies. A detection pattern 3 obtained by associating the current values and the drive frequencies is acquired. One of
The control unit 5a, in step S9, compares the maximum values of the current values of the detection pattern 1 to the detection pattern 3. When all the maximum values are equal to each other, the control unit 5a determines in step S10 that a foreign object is detected, and performs error processing. When all the maximum values of the current values of the detection patterns are not equal to each other, the control unit 5a determines that a power receiving device or apparatus is disposed, ends the antenna detection mode (step S11), and performs device authentication (step S12).
In steps S3, S6, and S8, on the assumption that a distant power receiving device or apparatus gradually comes close to the system, as described in 2-4, current measurement at the resonance frequencies of the resonance circuits may be performed at the last.
The flow chart described above may be stored in the storage unit 5b as a program and processed in the control unit 5a according to the steps. Furthermore, the control unit 5a and/or the storage unit 5b may be incorporated in a semiconductor device, or may be achieved with a system using a general-purpose CPU, as a matter of course.
4. Configuration of Power Transmission and Receiving Device
As another embodiment, a device which receives an electric power transmission from a noncontact charging device or a noncontact communication device (reader/writer or the like) serving as the power transmission device 1 or transmitted data, charges its own secondary battery, and operates the main body may serve as a power transmission device for anther power receiving device. It is assumed that such a device is called a power transmission and receiving device here.
As shown in
The power transmission and receiving device 50a includes a transmission and receiving unit 52 having antenna 52a electromagnetically coupled to an antenna 72a included in another power receiving device or a power transmission and receiving device 70. The power transmission and receiving device 50a includes an inverter unit 53 that converts an electric power of a secondary battery 51 included in the power transmission and receiving device 50a into an AC electric power having a predetermined drive frequency to drive the antenna 52a of the transmission and receiving unit 52. The power transmission and receiving device 50a includes a waveform monitor unit 54 that acquires a current waveform of the antenna 52a, and a control system unit 55 that sets a drive frequency for the inverter unit 53 on the basis of a current value acquired by the waveform monitor unit 54. The control system unit 55 includes a storage unit 55b in which a program expressing an operation procedure of the power transmission and receiving device 50a is written, and a control unit 55a that controls an operation of the power transmission and receiving device 50a according to the procedure in the storage unit 55b. The control unit 55a is, for example, a CPU (Central Processing Unit) or a micro-controller. The storage unit 55b may be a mask ROM mounted on, for example, a micro-controller, or may be an EPROM, an EEPROM, or the like. The storage unit 55b is not limited to these memories.
The control unit 55a sets a drive frequency for driving the antenna unit 52a to the inverter unit 53 according to the program stored in the storage unit 55b. The inverter unit 53 oscillates in a sine wave having the set drive frequency to drive the antenna unit 52a. When the other power transmission and receiving device 70 is in a communication area of the power transmission and receiving device 50, a current flowing in the antenna unit 52a changes due to the presence of the resonance circuit configured by the antenna unit 72a, and the change is acquired by the waveform monitor unit 54. Alternatively, when a foreign object such as metal plate is present at the position of the other power transmission and receiving device 70, a peak value of the current value is acquired by the waveform monitor unit 54.
The drive frequency is changed according to the program stored in the storage unit 55b, and acquisition of peak values of currents in the antenna unit 52a to the changed drive frequencies is repeated predetermined times. A pattern obtained by comparing peak current values in units of the acquired drive frequencies is compared with a pattern of peak current values which are acquired in advance with respect to the presence/absence of the other power transmission and receiving device 70 to determine the presence/absence of the other power transmission and receiving device 70 in the control unit 55a.
The above configuration is a configuration about the power transmission function of the power transmission and receiving device 50a. The power transmission and receiving device 50a further includes a rectifying unit 56 that converts a power received through the antenna 52a into a DC power, and a charging control unit 57 that performs charging control of the secondary battery 51 by using an electric power converted into a DC power by the rectifying unit 56. The received electric power electrically charges the secondary battery 51 through the charging control unit 57, and may also directly operate a device main body 60 by a charging SW 58.
As described above, in the power transmission and receiving device 50a, by using an electric power of the secondary battery 51 included in the power transmission and receiving device 50a, operates the inverter unit 53 to make it possible to detect a power receiving device or the other power transmission and receiving device 70.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013-060646 | Mar 2013 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2014/056317 | 3/11/2014 | WO | 00 |
