JP5075455B2 - Wireless power supply system - Google Patents

Wireless power supply system Download PDF

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JP5075455B2
JP5075455B2 JP2007104261A JP2007104261A JP5075455B2 JP 5075455 B2 JP5075455 B2 JP 5075455B2 JP 2007104261 A JP2007104261 A JP 2007104261A JP 2007104261 A JP2007104261 A JP 2007104261A JP 5075455 B2 JP5075455 B2 JP 5075455B2
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transmission antenna
power transmission
frequency
resonance
drive
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JP2008263710A (en
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秀治 宮原
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オリンパス株式会社
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Description

  The present invention relates to a wireless power feeding system that supplies current through a power receiving antenna by causing a current to flow through a power transmitting antenna and, for example, relates to a wireless power feeding system that wirelessly feeds a capsule endoscope from outside the body.

2. Description of the Related Art In recent years, a wireless power feeding system that draws current through a power transmission antenna and supplies power to a small medical device through the power reception antenna by a generated magnetic field has attracted attention. Such a wireless power feeding system is particularly effective when, for example, power is supplied to the capsule endoscope wirelessly from outside the body.
For example, Patent Document 1 discloses a technique for supplying electric power through a secondary coil (power receiving antenna) using a magnetic field generated by passing a current through a primary coil (power transmitting antenna) used in the wireless power feeding system. The technique disclosed in Patent Document 1 will be described with reference to FIGS.

  FIG. 10 is a configuration diagram showing a conventional example of a capsule endoscope system in the case where power is supplied from outside the body to a capsule endoscope which is a small medical device inside the body by a wireless power feeding method, and FIG. FIG. 3 is an explanatory diagram showing a state in which primary coils are arranged in each of XYZ axial directions.

  As shown in FIG. 10, the primary coils 111a, 111b, 112a, 112b, 113a, 113b are configured in a Helmholtz type. The primary coils 112a and 112b are primary coils in the X-axis direction, the primary coils 113a and 113b are primary coils in the Y-axis direction, and the primary coils 111a and 111b are primary coils in the Z-axis direction.

  A capsule endoscope 100 as a small medical device is retained in the body of a subject, and a secondary coil 101 is disposed inside the capsule endoscope 100. Electric power necessary for the operation of the capsule endoscope 100 is loaded from the primary coils 111a, 111b, 112a, 112b, 113a, and 113b (abbreviated as 111a to 113b) into the capsule endoscope 100. The capsule endoscope 100 is supplied through the secondary coil 101.

  A specific configuration of such a capsule endoscope system will be described. As shown in FIG. 10, primary coil resonance capacitors 122, 124, 126 for each primary coil of the plurality of primary coils 111 a to 113 b. Is connected. Switching circuits 121, 123, and 125 are connected to the primary coil resonance capacitors 122, 124, and 126, respectively, and a DC power source 115 is connected to the switching circuits 121, 123, and 125.

  In such a capsule endoscope system, when power is supplied to the capsule endoscope 100, high-frequency voltages from the switching circuits 121, 123, and 125 are converted into primary coils 111a to 113b and resonance capacitors 122, 124, A magnetic field parallel to the axial direction of each of the primary coils 111a to 113b constituting the series resonance circuit is generated by being applied to the 126 series circuit.

  The primary coils 111 a to 113 b are provided with energy detection circuits 128, 130, and 132, respectively, and the detection outputs of the energy detection circuits 128, 130, and 132 are supplied to the comparator 136. The output from the comparator 136 is supplied to the switches SW1, SW2, and SW3 connected between the switching circuits 121, 123, and 125 and the DC power source 115, so that the switches SW1, SW2, and SW3 are turned on and off. Is to be controlled.

  Such a conventional capsule endoscope system utilizes the fact that the current flowing through the primary coils 111a to 113b increases as the magnetic coupling between the primary coils 111a to 113b and the capsule endoscope 100 increases. The primary coil that supplies power to the mirror 100 is selected from a plurality of primary coils 111a to 113b.

  Explaining a specific selection method, the capsule endoscope system shown in FIG. 10 simultaneously drives a plurality of primary coils 111a to 113b for a certain period of time. At this time, the energy detection circuits 128, 130, and 132 provided in the plurality of primary coils 111a to 113b detect currents flowing through the primary coils 111a to 113b, respectively. In other words, the stronger the magnetic coupling between the primary coil and the capsule endoscope 100, the more current flows through the primary coil, so that a plurality of primary coils with the strongest magnetic coupling between the primary coil and the capsule endoscope 100 are provided. The primary coils 111a to 113b are selected.

  That is, the detection results from the energy detection circuits 128, 130, and 132 are supplied to the comparator 136. The comparator 136 compares the detection outputs of the energy detection circuits 128, 130, and 132, and the energy detection circuit 128, The switches SW1 to SW3 are controlled to be turned on and off so that only the primary coil corresponding to the output having the largest output of 130 and 132 is driven and the driving of the other primary coils is stopped.

By performing such control, a magnetic field is generated only from the primary coil that can always supply the maximum power (energy). As a result, the generation of the magnetic field from the primary coil having a large transmission power loss (energy loss) is stopped, and efficient power supply to the capsule endoscope 100 becomes possible. In addition, by detecting energy from each of the primary coils 111a to 113b at regular intervals, it is possible to supply power in an always efficient manner following the movement of the capsule endoscope 100 in the body. .
JP 2004-159456 A

  By the way, in the conventional wireless power feeding system as described above, considering a driving method of a normal power transmission antenna (hereinafter, a power transmission antenna including a primary coil and a resonance capacitor), the power transmission antenna is shown in FIG. When a series resonance circuit composed of a coil and a capacitor as shown in the figure is configured, the impedance of the power transmission antenna is lowest when the drive frequency of the power transmission antenna matches the resonance frequency of the series resonance circuit. Therefore, when the drive voltage of the power transmission antenna is constant, the drive current of the power transmission antenna can flow most.

  However, as is well known, the capacitor capacitance value has a temperature characteristic, and the capacitance value changes with the element temperature of the capacitor. Therefore, when the temperature of the capacitor changes, the resonance frequency of the power transmission antenna composed of the capacitor etc. changes, and even if the initial drive frequency and the resonance frequency match, the resonance frequency changes with the temperature change of the capacitor. However, the drive frequency and the resonance frequency gradually shift.

  And when a drive frequency and a resonant frequency shift | deviate, the impedance of a power transmission antenna becomes high and the drive current of a power transmission antenna becomes difficult to flow. In such a state, in order to secure a current necessary for the operation of the capsule endoscope 100, the drive voltage must be increased. Further, depending on the positional relationship between the power transmission antenna and the power reception antenna, the effective inductance L value of the coil of the primary circuit may change.

  From the above, in a conventional wireless power feeding system having a series resonance circuit, the impedance increases rapidly when the drive frequency deviates from the resonance frequency, and the drive voltage must be significantly increased even if it slightly deviates from the resonance frequency. Since a necessary current cannot be obtained, there is a problem that the power supply efficiency of the capsule endoscope 100 is significantly reduced.

  In the prior art described in Patent Document 1, there is no disclosure or suggestion about a detailed description of a driving method of a primary coil as well as specific components for solving the above problems.

  Therefore, the present invention has been made in view of the above problems, and even if a deviation occurs between the resonance frequency and the drive frequency of the power transmission antenna, control is performed so that the drive frequency is always matched with the resonance frequency. An object of the present invention is to provide a wireless power feeding system that can efficiently drive a power transmission antenna at a frequency.

The wireless power feeding system of the present invention includes a power transmission antenna having a coil and a resonance capacitor for transmitting power to a power receiving antenna side that receives power by a wireless method, and a clock signal for driving the transmission antenna. An oscillator to be generated, a drive circuit that drives the power transmission antenna based on a clock signal from the oscillator, a drive voltage source that is connected to the drive circuit and supplies a drive voltage to the power transmission antenna, and A detection unit that detects operation information of the power transmission antenna for obtaining a resonance frequency, and a resonance frequency of the power transmission antenna is determined based on a detection result by the detection unit, and the driving frequency of the power transmission antenna is set to the resonance frequency. comprising a control unit for controlling the oscillator so as matching, the said detection unit, the resonance capacitor It characterized in that it is a temperature detector for detecting the temperature.

  According to the present invention, even if a deviation occurs between the resonance frequency and the drive frequency of the power transmission antenna, control is performed so that the drive frequency always matches the resonance frequency, and the power transmission antenna is always efficiently driven at the resonance frequency. It is possible to provide a wireless power feeding system that can be performed.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
1 to 5 show a first embodiment of a wireless power feeding system according to the present invention, FIG. 1 is a block diagram showing an overall configuration of the wireless power feeding system of the first embodiment, and FIG. 2 is a block diagram of FIG. FIG. 3 is a graph showing a temperature characteristic based on the temperature and capacity of the resonance capacitor in FIG. 1, and FIG. 4 is an impedance characteristic based on the driving frequency of the power transmission antenna. FIG. 5 is a flowchart illustrating an example of control by the control unit of FIG. 1 for explaining the operation of the first embodiment.

  Each embodiment according to the present invention to be described later is applied to a capsule endoscope system including a capsule endoscope having a power receiving antenna. However, the present invention is naturally applicable to other wireless power feeding systems. Is possible.

  As shown in FIG. 1, a wireless power feeding system 1 according to a first embodiment includes a capsule endoscope 2 as a capsule-like small medical device that stays in a patient's body, and a capsule that stays in the body. The endoscope 2 is configured to have a wireless power feeding device 3 for supplying power from outside the body by a wireless power feeding method.

As is well known, the capsule endoscope 2 includes an imaging unit, an image information processing unit, an information transmission unit, a power supply unit 2A (see FIG. 1) and the like (not shown). This is an apparatus for acquiring an image of an organ or the like.
Note that the capsule endoscope 2 shown in FIG. 1 is not shown in a configuration that is not related to the components of the present invention, and a schematic configuration will be described later.

  The imaging unit of the capsule endoscope 2 includes an illumination system such as a light emitting diode, an imaging optical system that forms a subject image on a light receiving surface of the imaging element, an imaging element such as an image sensor, and drives or controls the imaging element. And an image pickup circuit system such as a circuit for doing so.

The image information processing unit takes in an electrical signal (image signal) output from the image sensor and performs predetermined signal processing.
The information transmission unit includes a modulation transmission antenna unit and a transmission antenna for transmitting the signal processed by the image information processing unit to an external display device or the like.

  The power supply unit 2A is for supplying necessary power to the imaging unit, the image information processing unit, and the information transmission unit, and a specific configuration is shown in FIG.

  As shown in FIG. 1, the power supply 2 </ b> A of the capsule endoscope 2 includes a secondary coil 21, a core 22, a resonance capacitor 23, and a rectifier circuit 24 that form a power receiving antenna.

In such a capsule endoscope 2, the secondary coil 21 and the resonance capacitor 23 are connected in parallel, and the secondary coil 21 and the resonance capacitor 23 connected in parallel have four diodes D <b> 1 to D <b> 1. It is connected to a rectifier circuit 24 consisting of D4.
The configuration of the power supply unit is an example and is not limited to this.

  With such a configuration, the alternating current induced in the secondary coil 21 is converted into direct current by the rectifier circuit 24, and the direct current is used as electrical energy in the capsule endoscope 2. The capacitance value of the resonance capacitor 23 is set so that the secondary coil 21 and the resonance capacitor 23 perform parallel resonance, as in the case of the primary coil of the power transmission antenna 4 described later. This makes it possible to extract large energy efficiently.

Next, the configuration of the wireless power feeder 3 will be described with reference to FIG.
As shown in FIG. 1, the wireless power feeding device 3 includes a power transmission antenna 4, a temperature detection unit 6 constituting a detection unit, a drive circuit 7, a drive voltage source 8, an oscillator 9, and a control unit 10 such as a controller. And is configured.

  The power transmission antenna 4 includes power transmission coils 4 a and 4 b and a resonance capacitor 5 that constitute primary coils for transmitting power to the capsule endoscope 2 by a wireless method.

The power transmission antenna 4 is an LC series resonance type power transmission antenna in which power transmission coils 4a and 4b and a resonance capacitor 5 are connected.
The power transmission antenna 4 is arranged outside the patient's body so that the capsule endoscope 2 staying in the patient's body operates normally. Specifically, the power transmission antenna 4 is configured in, for example, a Helmholtz type, and the power transmission coil 4a and the other power transmission coil 4b are arranged so as to sandwich the patient's body.

  In the present embodiment, for simplicity of explanation, a configuration having one power transmission antenna 4 will be described. Of course, even in a configuration having a plurality of power transmission antennas 4 as in the prior art of FIG. Applicable.

  A drive circuit 7 is electrically connected to the power transmission antenna 4. The drive circuit 7 drives the power transmission antenna 4 based on a clock signal from an oscillator 9 described later.

A drive voltage source 8 for supplying a drive voltage to the power transmission antenna 4 and an oscillator 9 for generating a clock signal for driving the power transmission antenna 4 are electrically connected to the drive circuit 7.

  The drive voltage source 8 and the oscillator 9 are electrically connected to a controller 10 such as a controller that can control the entire wireless power feeding system 1. The control unit 10 controls the drive voltage source 8 and the oscillator 9. As a result, the power transmission antenna 4 is driven via the drive circuit 7 by the clock signal from the oscillator 9 and the voltage output from the drive voltage source 8.

  The control unit 10 is electrically connected to a temperature detection unit 6 as a detection unit that detects operation information of the power transmission antenna 4 for obtaining the resonance frequency of the power transmission antenna 4.

  The temperature detection unit 6 is provided directly or in the vicinity of the resonance capacitor 5, detects operation information of the power transmission antenna 4, specifically the temperature of the resonance capacitor 5, and detects the detection result as the control unit. 10 is output.

  The control unit 10 determines the resonance frequency fr of the power transmission antenna 4 based on the detection result by the temperature detection unit 6, and sets the oscillator 9 so that the drive frequency of the power transmission antenna 4 matches the resonance frequency fr. Control.

  Here, in order to determine the resonance frequency fr of the power transmission antenna 4 by the control unit 10, the control unit 10 is provided with a storage unit 11 that stores temperature characteristic data of the resonance capacitor 5 in advance.

  That is, the control unit 10 determines the capacitance of the resonance capacitor 5 based on the temperature of the resonance capacitor 5 detected by the temperature detection unit 6 and the temperature characteristic data of the resonance capacitor 5 stored in the storage unit 11. The value C is obtained, and the resonance frequency fr of the power transmission antenna 4 is determined from the obtained capacitance value C of the resonance capacitor 5.

  An example of temperature characteristic data of the resonance capacitor 5 stored in advance in the storage unit 11 is shown in the graph of FIG. In FIG. 3, the horizontal axis indicates the temperature T, and the vertical axis indicates the capacitance C of the resonance capacitor.

That is, when the temperature of the resonance capacitor 5 is supplied from the temperature detection unit 6, the control unit 10 uses the temperature characteristic data of the resonance capacitor 5 as shown in FIG. Find C.
For example, when the temperature of the resonance capacitor 5 from the temperature detection unit 6 corresponds to the temperature change ΔT between the temperature T1 and the temperature T2, the capacitance value C1 to the capacitance value of the resonance capacitor 5 from the temperature characteristic data of FIG. A capacitance value change ΔC between C2 can be obtained.

The drive circuit 7 is configured to drive the power transmission antenna 4 based on the clock signal from the oscillator 9, but for the sake of simplicity, in the first embodiment, the clock signal output from the oscillator 9 is used. The power transmission antenna 4 is driven at the frequency output from the oscillator 9 without being frequency-converted by the drive circuit 7.
Accordingly, in the first embodiment, it is assumed that the oscillation frequency of the oscillator 9 (frequency of the clock signal) and the drive frequency of the power transmission antenna 4 coincide with each other. Since oscillation control is performed, it is possible to recognize the drive frequency of the power transmission antenna 4.

Next, a method for calculating the resonance frequency fr of the power transmission antenna 4 by the control unit 10 will be described with reference to FIG.
Here, assuming that the inductance component of the power transmission antenna 4 (a combination of the power transmission coil 4a and the power transmission coil 4b) is L and the capacitance component of the resonance capacitor 5 is C, the resonance frequency fr of the power transmission antenna 4 is expressed by the following equation. Determined by.

fr = 1 / 2π√LC (Formula 1)
Therefore, as described above, the control unit 10 obtains the capacitance component C (capacitance value) of the power transmission coils 4a and 4b based on the temperature characteristic data shown in FIG. The resonance frequency fr can be calculated and determined. Then, if the control unit 10 controls the oscillation frequency of the oscillator 9 to match the determined resonance frequency fr of the power transmission antenna 4, the power transmission antenna 4 can be driven at the resonance frequency fr.

  In consideration of the impedance characteristic of the power transmission antenna 4, when the resonance capacitor 5 and the power transmission coils 4a and 4b are connected in series to form an LC series resonance circuit, the impedance characteristic of the power transmission antenna 4 is shown in FIG. As shown, the impedance Ω is minimized at the resonance frequency fr.

  That is, the minimum impedance Ω means that the drive current DI is maximized when the drive voltage of the power transmission antenna 4 is constant. Therefore, if the LC series resonance circuit can drive the power transmission antenna 4 at the resonance frequency fr, a large amount of current can flow at a low driving voltage, and efficient driving is possible.

Next, the operation of the wireless power feeding system 1 having such a configuration will be described with reference to FIG.
Assume that the wireless power feeding system 1 shown in FIG. 1 is turned on and started. Then, the control unit 10 of the wireless power feeding system 1 reads and executes the program shown in FIG. 5 from a storage unit (not shown).

The control unit 10 drives the power transmitting antenna 4 via the drive circuit 7 by controlling the output voltage of the drive voltage source 8 and the clock signal from the oscillator 9.
In this case, the output voltage of the drive voltage source 8 is a voltage at which a sufficient current necessary for the operation of the capsule endoscope 2 flows through the power transmission antenna 4.

  And the control part 10 detects the temperature of the capacitor | condenser 5 for resonance of the power transmission antenna 4 by the temperature detection part 6 by the process of step S1, and takes in a detection result.

  Thereafter, the control unit 10 performs the processing of step S2 based on the temperature of the resonance capacitor 5 from the temperature detection unit 6 and the temperature characteristic data of the resonance capacitor 5 as shown in FIG. Is obtained.

  And the control part 10 calculates and determines the resonant frequency fr of the power transmission antenna 4 from said (Formula 1) using the calculated | required capacitance value C of the capacitor for resonance.

  Then, the control part 10 is controlled to set the drive frequency of the power transmission antenna 4 to the determined resonance frequency fr of the power transmission antenna 4 by the process of step S3. That is, the control unit 10 controls the oscillator 9 so that the oscillation frequency of the oscillator 9 matches the determined resonance frequency fr of the power transmission antenna 4.

  With the above operation, the frequency of the clock signal output from the oscillator 9, that is, the drive frequency of the power transmission antenna 4 can be set to the resonance frequency fr of the power transmission antenna 4. The power transmission antenna 4 is driven at the resonance frequency fr by the drive circuit 7.

  Then, the control unit 10 measures a certain time by a timer or the like (not shown) in the process of Step S4, and after the lapse of the certain time, repeats the processes of Step S1 to Step S4 again, and the temperature detection unit 6 performs resonance. The temperature of the capacitor 5 is detected, and control is performed so as to determine the resonance frequency fr of the power transmission antenna 4 based on the detected temperature. Note that the process of step S4 may be omitted if not necessary.

  As a result, the power transmission antenna 4 can be driven at the resonance frequency fr even if the capacitance value C of the resonance capacitor 5 changes due to the driving of the power transmission antenna 4 and the ambient temperature change. In addition, by detecting the temperature of the resonance capacitor 5 at a constant period or in real time, the power transmission antenna 4 is always set to the resonance frequency fr by changing the oscillation frequency fr of the oscillator 9 with respect to the temperature change of the resonance capacitor 5. It can be driven by.

  The temperature detection method of the resonance capacitor 5 has been described so that the temperature of the resonance capacitor 5 is detected by the temperature detection unit 6, but is not particularly limited, and the temperature detection of the resonance capacitor 5 is surely performed. If possible, any method can be applied to the present embodiment.

  Further, in the present embodiment, the case where the power transmission antenna 4 is configured as a Helmholtz type has been described. However, the present invention is not limited to this, and an LC series resonance type of a primary coil (power transmission coil) and a capacitor is used. If it is the power transmission antenna 4, even if the power transmission antenna 4 is single, it is applicable to this Embodiment.

Furthermore, in the present embodiment, the configuration having one power transmission antenna 4 has been described. However, the present invention is not limited to this, and of course, a plurality of power transmission antennas 4 are provided as shown in the related art of FIG. A current detection resistor, an energy detection circuit, a switching circuit, and the like corresponding to the plurality of power transmission antennas 4 may be provided, and the control unit 10 may be configured to perform the same control as the comparator 136 illustrated in FIG.
As a result, the magnetic field is generated only from the power transmission antenna 4 that always supplies the maximum power (energy), and the generation of the magnetic field from the power transmission antenna 4 having a large power transmission loss (energy loss) is stopped. An efficient power supply to the endoscope 2 is possible.

Therefore, according to the first embodiment, even if the temperature of the capacitor rises due to a change in ambient temperature or the heat generated by the resonance capacitor due to driving, the capacitance value of the capacitor changes, and a deviation occurs between the resonance frequency and the driving frequency. Control can be performed so that the drive frequency always matches the resonance frequency.
As a result, the power transmitting antenna can be efficiently driven at the resonance frequency at all times, and power can be efficiently transmitted to the power receiving antenna with a small amount of transmitted power.

(Second Embodiment)
6 to 8 show a second embodiment of the wireless power feeding system according to the present invention, FIG. 6 is a block diagram showing the overall configuration of the wireless power feeding system of the second embodiment, and FIG. FIG. 8 is a flowchart illustrating an example of control by the control unit in FIG. 6 and FIG. 8 is a flowchart illustrating a modification of the control example by the control unit in FIG. 7 for explaining the operation of the embodiment.
In FIG. 6, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. Only different portions will be described.

  As shown in FIG. 6, the wireless power feeding system 1A of the second embodiment is configured in substantially the same manner as the wireless power feeding system 1 of the first embodiment of FIG. Thus, the current detection unit 12 constituting the detection unit is provided.

  In the second embodiment, as in the first embodiment, a configuration having one power transmission antenna 4 will be described for the sake of simplification. Of course, as in the prior art of FIG. The present invention can also be applied to a configuration in which a plurality of power transmission antennas 4 are provided.

  The current detection unit 12 detects the current flowing through the power transmission antenna 4, which is operation information of the power transmission antenna 4, and outputs the detection result to the control unit 10.

  The control unit 10 controls the drive voltage source 8 to make the drive voltage of the power transmission antenna 4 constant, and then sweeps the drive frequency of the power transmission antenna 4 and displays the detection result from the current detection unit 12 during the sweep scan. Based on this, the frequency at which the drive current of the power transmission antenna 4 is maximized is detected, and control is performed so that the drive frequency of the power transmission antenna 4 matches the detected frequency.

  Here, when considering the drive frequency of the LC series resonance circuit in which the resonance capacitor 5 and the power transmission coils 4a and 4b are connected in series and the impedance characteristics of the power transmission antenna 4, as shown in FIG. When the drive frequency f is gradually changed, the drive current DI flowing at a certain frequency f becomes maximum.

Thereafter, when the frequency f is further changed, the flowing drive current DI gradually decreases. That is, the frequency at which the drive current DI is maximum is the resonance frequency fr. Accordingly, the resonance frequency fr can be found by detecting the drive frequency f that maximizes the drive current DI value while monitoring the drive current of the power transmission antenna 4 by the control unit 10.
Note that the monitoring by the control unit 10 means that sweep scanning is performed based on the detection result from the current detection unit 12. Thus, the control unit 10 can detect the drive frequency f at which the drive current DI value becomes maximum, that is, the resonance frequency fr.

  In the first embodiment, the storage unit 11 storing the temperature characteristic data of the resonance capacitor 5 is provided in the control unit 10. However, in the second embodiment, the temperature characteristic data is not necessary. Therefore, the storage unit 11 is not required. In this case, only the temperature characteristic data may be deleted while leaving the storage unit 11. Further, other necessary data may be stored in the remaining storage unit 11.

  Other configurations are the same as those in the first embodiment.

Next, the operation of the wireless power feeding system 1A having such a configuration will be described with reference to FIG.
Now, it is assumed that the wireless power feeding system 1A shown in FIG. Then, the control unit 10 of the wireless power feeding system 1A reads and executes the program shown in FIG. 7 from a storage unit (not shown).

The control unit 10 drives the power transmitting antenna 4 via the drive circuit 7 by controlling the output voltage of the drive voltage source 8 and the clock signal from the oscillator 9.
In this case, the output voltage of the drive voltage source 8 is a voltage at which a sufficient current necessary for the operation of the capsule endoscope 2 flows through the power transmission antenna 4.

  And the control part 10 detects the drive current DI of the power transmission antenna 4 by the electric current detection part 12, and takes in a detection result by the process of step S10.

  Thereafter, the control unit 10 determines whether or not the drive current DI of the resonance capacitor 5 from the current detection unit 12 is the maximum value in the process of step S11, and if it is determined that it is not the maximum value, The process proceeds to step S12, and when it is determined that the maximum value is reached, the process proceeds to step S13.

  That is, the determination process in step S11 is to find the frequency f at which the drive current DI is maximum in order to match the drive frequency of the power transmission antenna 4 with the resonance frequency fr.

  Here, for example, the control unit 10 finds the frequency f at which the drive current DI is maximized by a method as described below, and performs processing so as to match the drive frequency and the resonance frequency fr.

  The control unit 10 shifts the oscillation frequency of the oscillator 9 by Δf with respect to the frequency at the start of driving of the power transmission antenna 4 in the process of step S12, and then returns the process to step S10 so that the power transmission antenna 4 at that time The flowing drive current DI is detected using the current detection unit 12.

Then, the control unit 10 again compares the detected drive current DI with the drive current before shifting by Δf in the determination process of step S11.
In this case, if the detected drive current DI is larger than the drive current DI before the oscillation frequency f is shifted by Δf, the oscillation frequency f is further shifted by Δf, and similarly the drive current DI before the shift by Δf is Compare. Thereafter, the control unit 10 shifts the oscillation frequency f by Δf and compares the detected drive current DI with the drive current before the oscillation frequency f is shifted by Δf each time.

  Thereafter, the control unit 10 can find the frequency at which the drive current DI becomes maximum if the oscillation frequency f is shifted by Δf until the drive current DI starts to decrease as shown in FIG. Hereinafter, this method is referred to as a hill climbing method).

  Conversely, if the detected drive current DI is smaller than the drive current DI before the oscillation frequency f is shifted by Δf, the control unit 10 shifts the oscillation frequency of the oscillator 9 by −Δf and shifts by −Δf. The drive current DI before the operation is compared with the detected drive current DI.

  In this case, when the detected drive current DI is larger than the drive current DI before shifting by -Δf, the control unit 10 further shifts the oscillation frequency f by -Δf and detects the detected drive current DI. If the oscillation frequency f is shifted by −Δf until it starts to decrease as shown in FIG. 4, the frequency f at which the drive current DI becomes maximum can be found.

  As described above, the control unit 10 performs the processing from step S10 to step S12 and repeats the shift control of the oscillation frequency f of the oscillator 9 until the drive frequency f at which the drive current DI is maximized is found.

  Thus, when the drive current DI becomes the maximum, the control unit 10 shifts the process to step S13 by the determination process of step S11.

  That is, when the control unit 10 finds the frequency f at which the drive current DI is maximum, that is, the resonance frequency fr, in step S13, the control unit 10 sets the oscillation frequency of the oscillator 9 so that the drive frequency matches the resonance frequency fr. Fix it. Thus, the power transmission antenna 4 can be driven at the resonance frequency fr as in the first embodiment.

The control unit 10 according to the second embodiment may be controlled based on a program as shown in a modified example of FIG. Such a modification will be described with reference to FIG.
The flowchart by the control unit in FIG. 8 corresponds to the case where a certain time has elapsed in the second embodiment.

  That is, as shown in FIG. 8, a process for measuring a certain time (a process for measuring t = t + Δt: a process for measuring t = t + Δt: step S14) is provided after the step S13 shown in FIG. After the elapse of time, the process returns to step S10 again.

  Therefore, as shown in FIG. 8, the control unit 10 sets the drive frequency of the power transmission antenna 4 to the frequency f at which the drive current DI is maximum, and drives the power transmission antenna 4 again after a predetermined time in the process of step S14. The current DI is detected (step S10), and it is determined whether the drive current DI is maximum with respect to the drive frequency (step S11). If not, the drive current of the power transmission antenna 4 is maximized. Control is performed so as to reset the oscillation frequency of the oscillator 9 again through steps S10 to S11 and S13 via step S12.

  Thus, even if the resonance frequency fr of the power transmission antenna 4 changes by performing detection of the drive current of the power transmission antenna 4 continuously or at regular intervals by the control unit 10, the drive frequency f is surely set to the resonance frequency. It is possible to follow the fr to coincide with fr, and the power transmission antenna 4 can be driven efficiently.

  In the first embodiment, since the capacitance value C of the resonance capacitor 5 is obtained using the temperature characteristic data, the temperature characteristic of the resonance capacitor 5 being used and the control unit 10 are stored in the storage unit 11. When the held temperature characteristic data is different (for example, individual characteristic variation of the resonance capacitor 5 or the like), there is a possibility that the drive frequency and the resonance frequency fr are deviated. In the second embodiment, the power transmission antenna 4 is detected, and the oscillation frequency of the oscillator 9 is set to the frequency f at which the drive current DI is maximum. Therefore, the power transmission antenna 4 can always be driven at the resonance frequency fr. Further, the second embodiment can cope with a situation in which the inductances of the power transmission coils 4a and 4b are changed.

  In the second embodiment, the so-called hill-climbing method is used to detect the maximum value of the drive current of the power transmission antenna 4; however, the hill-climbing method is not necessarily used, and power transmission can be performed using other algorithms. It is only necessary that the drive frequency f at which the drive current of the antenna 4 is maximized can be detected.

  Therefore, according to the second embodiment, the drive current DI of the power transmission antenna 4 is detected, the frequency at which the drive current DI is maximum is found, and the power transmission antenna 4 is driven at this frequency, whereby the first Compared to the first embodiment, the drive frequency and the resonance frequency fr can be reliably matched.

  Further, unlike the first embodiment, it is not necessary to previously store the temperature characteristic data of the resonance capacitor 5 for each resonance capacitor 5 in the storage unit 11 of the control unit 10, and the drive frequency of the power transmission antenna 4 is set. The resonance frequency fr can be matched.

  Furthermore, in the second embodiment, it is obvious that not only the capacitance value C of the capacitor but also the inductance components of the power transmission coils 4a and 4b can be changed due to changes in the coil shape or the like.

(Third embodiment)
FIG. 9 shows a third embodiment of the wireless power feeding system according to the present invention, and is a flowchart showing an example of control by the control unit of FIG. 9 for explaining the operation of the third embodiment.

  In FIG. 9, the same processing contents as the processing contents of FIGS. 7 and 8 in the second embodiment are denoted by the same step S numbers, and different processing contents will be described.

  The configuration of the wireless power feeding system of the third embodiment is substantially the same as that of the wireless power feeding system 1A of the second embodiment. However, although not shown, the control unit 10 is provided with a storage unit 11 (see FIG. 1), and the storage unit 11 stores data on the optimum value of the drive current of the power transmission antenna 4 in advance. ing.

  Here, the optimum value of the drive current stored in the storage unit 11 is the current value of the power transmission antenna 4 that can supply sufficient power necessary for the capsule endoscope 2 to operate. The current value is such that the capsule endoscope 2 can operate regardless of the position of the capsule endoscope 2 in the region. The optimum value of the drive current will be described as being independent of the position and orientation of the capsule endoscope 2.

Next, the operation of the wireless power feeding system 1A having such a configuration will be described with reference to FIG.
Now, it is assumed that the wireless power feeding system 1A shown in FIG. Then, the control unit 10 of the wireless power feeding system 1A reads and executes the program shown in FIG. 9 from a storage unit (not shown).

  And the control part 10 is the process of step S10 to step S13 similarly to the said 2nd Embodiment, For example, using the hill-climbing method, resonance frequency fr which is a frequency with which the drive current DI of the power transmission antenna 4 becomes the maximum is used. Detecting and setting the drive frequency of the power transmission antenna 4 to the resonance frequency fr.

  Thereafter, the control unit 10 sets the drive frequency of the power transmission antenna 4 to the resonance frequency fr, and then fixes the drive frequency of the power transmission antenna 4 to the resonance frequency fr. As a result, the power transmission antenna 4 is driven at the resonance frequency fr.

  Next, in 3rd Embodiment, the control part 10 detects the drive current DI of the power transmission antenna 4 by the electric current detection part 12, and takes in a detection result by the process of step S20.

Thereafter, the control unit 10 compares the drive current DI of the resonance capacitor 5 from the current detection unit 12 with the optimum value data stored in the storage unit 11 in the determination process of step S21.
In this case, when it is determined that the detected drive current DI exceeds the optimum value, the control unit 10 performs control so as to lower the drive voltage of the drive voltage source 8 of the power transmission antenna 4 in the process of step S22. Conversely, if it is determined that the detected drive current DI is below the optimum value, the drive voltage DI of the power transmission antenna 4 is set to the optimum value by controlling the drive voltage of the drive voltage source 8 to be increased. Thus, the drive voltage of the drive voltage source 8 is set.

  Here, when the drive current DI of the power transmission antenna 4 is set to the optimum value, that is, when the control unit 10 determines that the detected drive current DI is equal to the optimum value, the process of step S23 is performed. Thus, the drive voltage of the power transmission antenna 4 is fixed.

  Thereafter, the control unit 10 measures a fixed time in the process of step S24 (t = t + Δt, where t is a fixed time), and returns the process to step S10 again after the fixed time has elapsed. That is, after a predetermined time has elapsed, the control unit 10 detects the drive current DI of the power transmission antenna 4 again in the process of step S10, and the drive frequency of the power transmission antenna 4 matches the resonance frequency fr in the determination process of step S11. Determine whether you are doing it.

  In this case, when the drive frequency and the resonance frequency fr are deviated, the control unit 10 resets the drive frequency to the resonance frequency fr by performing the processing from step S10 to step S13 again via step S12. To control.

  Thereafter, after setting the drive frequency to the resonance frequency fr, the control unit 10 repeats the processing from step S21 to step S22 in the same manner as described above, so that the drive current DI of the power transmission antenna 4 becomes the optimum value. And control to return to the process of step S10 via step S23 and step S24.

  As described above, by setting the drive frequency to the resonance frequency fr and further setting the drive voltage of the power transmission antenna 4 so that the drive current DI becomes an optimum value, the power transmission antenna 4 is driven with a drive power larger than necessary. It is not driven and power can be supplied to the capsule endoscope 2 more efficiently.

  Even in the case of controlling to always drive at the resonance frequency fr by the method of the first embodiment, as in the second embodiment, the current detection unit 12 is incorporated in the power transmission antenna system, and further inside the control unit 10 By storing the data of the optimum value of the drive current in the storage unit 11, it becomes possible to drive the power transmission antenna 4 with the optimum current value as in the third embodiment. In this case, the current detector 12 is used only for setting the optimum value of the drive current DI.

Therefore, according to the third embodiment, in addition to ensuring that the drive frequency of the power transmission antenna 4 matches the resonance frequency fr, the drive of the power transmission antenna 4 is set so that the drive current DI of the power transmission antenna 4 becomes an optimum value. By setting the voltage, the capsule endoscope 2 can be efficiently supplied with power without being driven with an unnecessarily large driving power.
Further, when the drive frequency and the resonance frequency fr coincide with each other, the drive current DI of the power transmission antenna 4 is significantly increased, and a large current can be prevented from flowing through the power transmission antenna 4.

  The present invention is not limited to the first to third embodiments described above, and various modifications can be made without departing from the spirit of the invention.

1 is a block diagram showing an overall configuration of a wireless power feeding system according to a first embodiment of the present invention. Explanatory drawing which shows the state which inserts the capsule endoscope of FIG. 1 from a patient's mouth. The graph which shows the temperature characteristic based on the temperature and the capacity | capacitance of the capacitor | condenser for resonance of FIG. The graph which shows the impedance and drive current characteristic based on the drive frequency of a power transmission antenna. FIG. 3 is a flowchart for explaining the operation of the first embodiment and showing a control example by the control unit of FIG. 1. The block diagram which shows the whole structure of the wireless power feeding system of 2nd Embodiment which concerns on this invention. FIG. 7 is a flowchart for explaining the operation of the second embodiment and showing a control example by the control unit of FIG. 6. The flowchart which shows the modification of the example of control by the control part shown in FIG. The flowchart which shows the example of control by the control part of FIG. 9 for demonstrating operation | movement of the wireless power supply system of 3rd Embodiment which concerns on this invention. The block diagram which shows the structure of the conventional wireless power supply system. Explanatory drawing which shows the arrangement | positioning state of the primary coil in the conventional wireless electric power feeding system.

Explanation of symbols

1, 1A ... wireless power feeding system,
2 ... capsule endoscope,
2A ... power supply,
3 ... Wireless power feeding device,
4 ... Power transmission antenna,
4a, 4b ... power transmission coil,
5 ... Resonant capacitor,
6 ... temperature detector,
7 ... Drive circuit,
8 ... Driving voltage source,
9 ... Oscillator,
10 ... control unit,
11 ... storage unit,
12 ... Current detection unit,
21 ... Secondary coil,
22 ... Core
23: Resonance capacitor,
23 ... secondary coil,
24 ... rectifier circuit,
fr: Resonance frequency.

Claims (2)

  1. A power transmission antenna having a coil and a resonance capacitor for transmitting power by a wireless system to a power receiving antenna side that receives power by a wireless system;
    An oscillator for generating a clock signal for driving the transmitting antenna;
    A drive circuit for driving the power transmission antenna based on a clock signal from the oscillator;
    A driving voltage source connected to the driving circuit for supplying a driving voltage to the power transmission antenna;
    A detection unit for detecting operation information of the power transmission antenna for obtaining a resonance frequency of the transmission antenna;
    A control unit that determines a resonance frequency of the power transmission antenna based on a detection result by the detection unit, and controls the oscillator so that a driving frequency of the power transmission antenna matches the resonance frequency;
    Equipped with,
    The wireless power feeding system according to claim 1, wherein the detection unit is a temperature detection unit that detects a temperature of the resonance capacitor .
  2. The control unit includes a storage unit that stores temperature characteristic data of the resonance capacitor, the temperature of the resonance capacitor detected by the temperature detection unit, and the resonance capacitor stored in the storage unit. Based on the temperature characteristic data, the capacitance value of the resonance capacitor is obtained, and from the obtained capacitance value of the resonance capacitor, the resonance frequency of the transmission antenna is determined, and the drive frequency of the transmission antenna is set to the determined resonance frequency. The wireless power feeding system according to claim 1, wherein the wireless power feeding system is controlled to match .
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