JP2014207764A - Non-contact power-feeding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-contact power-feeding device which, even when a coupling coefficient between a primary side coil and a secondary side coil changes, can perform power transmission between the two coils with maximum efficiency at the coupling coefficient.SOLUTION: A secondary side coil short-circuit means 23 for short-circuiting between opposite ends of a secondary side coil 21 on a power-receiving device 2 side is provided, an inductance Lat a short-circuiting time of the secondary coil 21 is measured, and a coupling coefficient k is calculated. Then, control is exerted so that a power transmission efficiency η in a non-contact power-feeding unit 3 is at maximum by appropriately selecting the duty of a power converter 25 provided in front of a load 4 in accordance with the coupling coefficient k and a resistance value Rof the load 4.

Description

  The present invention relates to an electromagnetic induction type non-contact power feeding device.

  In the conventional non-contact power feeding, the primary side winding and the secondary side winding are arranged to face each other through a spatial gap, and the primary side capacitor that resonates with the primary side winding and the secondary side winding resonate. There is a technique for providing non-contact power transmission by providing a secondary side capacitor and electromagnetically coupling between both windings using a resonance phenomenon.

  In this case, for example, in the prior art described in Patent Document 1 below, a primary side capacitor that resonates with the primary side winding is connected in series, while a secondary side capacitor that resonates with the secondary side winding. Are connected in parallel to increase power transmission efficiency.

Japanese Patent No. 4644827

  However, in the non-contact power feeding device described in Patent Document 1, for example, the distance between the primary winding and the secondary winding is changed, or both windings are displaced from each other in the winding axis direction. When the coupling state of the primary side winding and the secondary side winding changes, the value of the load that maximizes the power transmission efficiency between the two windings changes accordingly.

  In the prior art, there is no means for detecting a change in the coupling state between the two windings and performing control so as to maximize the power transmission efficiency between the two windings based on the detected value. It was. For this reason, there has been a problem that the power transmission efficiency is lowered due to a change in the coupling state of the primary side winding and the secondary side winding.

  The present invention has been made to solve the above-described problems. Even when the coupling coefficient indicating the coupling state of the primary winding and the secondary winding changes, the maximum efficiency in the coupling coefficient is achieved. An object of the present invention is to provide a non-contact power supply device capable of transmitting power.

The contactless power supply device of the present invention includes an inverter circuit that outputs high-frequency power, a contactless power supply unit that transmits and receives the high-frequency power supplied from the inverter circuit through electromagnetic induction via a spatial gap, and the contactless power supply. A rectifier circuit that converts the high-frequency power transmitted and received by the power feeding unit into DC power; and a power converter that arbitrarily changes the voltage of the DC power output from the rectifier circuit and outputs the voltage to a load. The contact power feeding unit includes a primary side winding that resonates with the primary side capacitor and transmits high frequency power supplied from the inverter circuit, and a high frequency power that resonates with the secondary side capacitor and is transmitted from the primary side winding. A secondary winding that receives the power of
Secondary-side winding short-circuiting means for short-circuiting both ends of the secondary-side winding at an arbitrary timing, driving voltage detecting means for detecting the driving voltage of the inverter circuit, and driving current for detecting the driving current of the inverter circuit A primary drive voltage and a primary drive current including a primary component having the same frequency as the drive frequency of the inverter circuit based on the drive voltage and the drive current detected by the detection means and the drive voltage detection means and the drive current detection means; Primary component extraction means for extracting the primary drive extracted by the primary component extraction means for controlling the inverter circuit and the secondary side winding short-circuit means for short-circuiting the secondary-side winding. one to calculate the voltage and the resistance value R _Lmax coupling coefficient of the based on the value of the primary drive current above the non-contact power feeding section k and the power transmission efficiency η is maximum And side control circuit, and a communication means for transmitting and receiving the information of the resistance value R _Lmax calculated by the primary-side control circuit controls the operation of the secondary winding short-circuiting means, received via the communication means And a secondary side control circuit for controlling the operation of the power converter based on the resistance value _RLmax .

  The contactless power feeding device according to the present invention detects a coupling coefficient k between the primary side winding and the secondary side winding, and based on the detected coupling coefficient k and the state of the load, the electric power between the two windings. Since the control is performed so that the transmission efficiency η is maximized, the maximum power transmission efficiency η at the coupling coefficient k is obtained according to the change of the coupling coefficient k between the primary side winding and the secondary side winding. Power transmission can be performed.

It is a circuit block diagram which shows the electric constitution of the non-contact electric power feeder in Embodiment 1 of this invention. It is a detailed equivalent circuit diagram of the non-contact electric power feeding part and load of the non-contact electric power feeder of FIG. FIG. 3 is an equivalent circuit obtained by simplifying the detailed equivalent circuit diagram of FIG. 2. In the non-contact electric power feeder in Embodiment 1 of this invention, it is a detailed equivalent circuit diagram of the non-contact electric power feeding part when a secondary side coil is short-circuited by the secondary side coil short-circuit means. It is a wave form diagram of the drive voltage and drive current which were detected by the drive voltage detection means and drive current detection means in Embodiment 1 of this invention. It is a simple circuit diagram of the step-down converter which is an example of the power converter of the non-contact electric power feeder in Embodiment 1 of this invention. It is a simple circuit diagram of the boost converter which is an example of the power converter of the non-contact electric power feeder in Embodiment 1 of this invention. It is a simple circuit diagram of the buck-boost converter which is an example of the power converter of the non-contact electric power feeder in Embodiment 1 of this invention. It is a circuit diagram of the choke input type full bridge rectifier circuit which is an example of the rectifier circuit of the non-contact electric power feeder in Embodiment 1 of this invention. It is a flowchart which shows the control content of the non-contact electric power feeder in Embodiment 1 of this invention.

Embodiment 1 FIG.
1 is a circuit block diagram showing an electrical configuration of a non-contact power feeding apparatus according to Embodiment 1 of the present invention.

The contactless power supply device according to the first embodiment includes a power transmission device 1 and a power reception device 2.
The power transmission device 1 includes a DC power supply 11, an inverter circuit 12 that converts DC power from the DC power supply 11 into high-frequency AC power, and outputs the power, a primary winding 13 to which high-frequency power is supplied from the inverter circuit 12, and A primary side capacitor 14 that resonates with the primary side winding 13 is included. In this case, a primary side capacitor 14 is connected to the primary side winding 13 in series, and the primary side winding 13 resonates with the primary side capacitor 14 to transmit power by electromagnetic induction.

  The DC power supply 11 may be one obtained by converting AC power from a two-phase or three-phase AC power supply (not shown) into DC power by a rectifier circuit (not shown). The inverter circuit 12 can be of any circuit configuration, for example, can be configured by a half bridge circuit or a full bridge circuit.

Further, the power transmission device 1 includes a drive voltage detector 15 that detects the drive voltage of the inverter circuit 12, a drive current detector 16 that detects the drive current of the inverter circuit 12, the drive voltage detected by both the detectors 15 and 16, and Based on the drive current, the primary component extraction means 17 for extracting the primary drive voltage and primary drive current including the primary component having the same frequency as the drive frequency of the inverter circuit 12, and a constant high frequency with respect to the non-contact power feeding unit 3. The operation of the inverter circuit 12 is controlled so that AC power is supplied, and is extracted by the primary component extraction means 17 when the secondary winding 21 is short-circuited by the secondary winding short-circuit means 23 described later. the primary side control circuit that calculates the primary drive voltage and the primary coupling coefficient of the non-contact power feeding section 3 based on the drive current k and power transmission efficiency η is maximum resistance R _Lmax 8, and it includes a primary-side communication means 19 for performing wireless information communication with the later-described secondary-side communication means 29.

  The drive voltage detector 15 and the drive current detector 16 may have any circuit configuration easily assumed by those skilled in the art. As the primary component extraction means 17, for example, a discrete Fourier transform circuit is applied. The drive voltage detector 15 and the drive current detector 16 correspond to the drive voltage detection means and the drive current detection means in the claims.

  On the other hand, the power receiving device 2 includes a secondary winding 21 that is opposed to the primary winding 13 via a space gap, a secondary capacitor 22 that resonates with the secondary winding 21, and a secondary winding. Secondary-side winding short-circuit means 23 composed of a relay circuit or the like that short-circuits both ends of the terminal 21 at an arbitrary timing, a rectifier circuit 24 that converts high-frequency power received by the secondary-side winding 21 into DC power, and rectification A power converter 25 that converts the DC power output from the circuit 24 into an arbitrary voltage is provided, and a load 4 that consumes the received power is connected to the output side of the power converter 25. In this case, a secondary side capacitor 22 is connected in parallel to the secondary side winding 21, and the secondary side winding 21 resonates with the secondary side capacitor 22 and electromagnetic induction with the primary side winding 13. To receive power.

  That is, when high frequency power is supplied to the primary side winding 13, an alternating magnetic field is formed around the primary side winding 13, and the alternating magnetic field links the secondary side winding 21 to the secondary side winding 21 by an electromagnetic induction phenomenon. An induced electromotive force is generated. Thereby, non-contact power transmission / reception is performed between the primary side winding 13 and the secondary side winding 21.

Furthermore, the power receiving device 2 controls the operation of the output voltage detector 26, the output current detector 27, and the secondary winding short-circuit means 23 that detect the output voltage and output current of the power converter 25, respectively, and the output voltage. Based on the output voltage and output current detected by the detector 26 and the output current detector 27, and the value of the coupling coefficient k and the resistance value _RLmax sent from the primary side communication means 19, the power converter 25 A secondary side control circuit 28 for controlling the operation and a secondary side communication means 29 for performing wireless information communication with the primary side communication means 19 are included.

  The output voltage detector 26 and the output current detector 27 correspond to the output voltage detection means and the output current detection means in the claims. The primary communication means 19 and the secondary communication means 29 correspond to the communication means in the claims.

  In addition, here, the primary side winding 13, the primary side capacitor 14, the secondary side winding 21, and the secondary side capacitor 22 that transmit and receive power in a contactless manner are collectively referred to as a non-contact power feeding unit 3 hereinafter. .

  Further, the series connection of the primary side winding 13 and the primary side capacitor 14 and the parallel connection of the secondary side winding 21 and the secondary side capacitor 22 shown in FIG. 1 are examples, and the present invention is not limited to such a connection form. The primary side capacitor 14 may be connected in parallel and the secondary side capacitor 22 may be connected in series, or each of them may be connected in series and parallel. Moreover, the primary side winding 13 and the secondary side winding 21 can also be configured by attaching ferrite or the like as an iron core (not shown) to a wire rod such as a litz wire wound in a pancake shape. In FIG. 1, the winding direction of the primary winding 13 and the secondary winding 21 is shown to have the same polarity, but the winding direction may be reversed.

  In the first embodiment, the secondary winding 21, the secondary capacitor 22, the rectifier circuit 24, the power converter 25, the secondary control circuit 28, the load 4, The secondary winding short-circuit means 23 and the secondary communication means 29 are arranged on the moving body side, and the others are arranged on the fixed side. For example, when the non-contact power feeding device according to the present invention is applied to an electric vehicle, the moving body side is an electric vehicle and the stationary side is a ground facility.

Next, the coupling coefficient k between the primary side winding 13 and the secondary side winding 21 of the non-contact power feeding unit 3, the power transmission efficiency η, and the load resistance value R _Lmax that maximizes the power transmission efficiency η The relationship will be described.

  Similar to the contents described in the prior patent document 1, the load 4 is directly connected to the non-contact power feeding unit 3 including the primary side winding 13, the primary side capacitor 14, the secondary side winding 21, and the secondary side capacitor 22. Consider the case. And when the non-contact electric power feeding part 3 and the load 4 are made into an equivalent circuit, it will become like FIG. Note that the primary side parameter is converted to the secondary side and expressed with '(dash).

In FIG. 2, r ₀ ′ is the excitation resistance (iron loss) converted to the secondary side, r ₁ ′ is the resistance of the primary side winding 13 converted to the secondary side, and r ₂ is the secondary side winding 21. X ₀ ′ is the excitation reactance converted to the secondary side, x ₁ ′ is the primary side leakage reactance converted to the secondary side, x ₂ is the secondary side leakage reactance, and x _S ′ is the secondary side The converted reactance of the primary capacitor 14, x _P is the reactance of the secondary capacitor 22, V _IN ′ is the input voltage converted to the secondary side, I _IN ′ is the input current converted to the secondary side, I ₁ ′ is the primary side current converted to the secondary side, V ₂ is the secondary side voltage, I ₂ is the secondary side current, _RL is the resistance value of the load 4, _VL is the output voltage to the load 4, I _L is an output current to the load 4.

Here, the turn ratio of the primary side winding 13 and the secondary side winding 21 is set to a = N ₁ / N ₂ , r ₀ ′ representing iron loss, the primary side winding 13 and the secondary side winding 21. Each of the resistors r ₁ ′ and r ₂ has reactance x ₀ ′ (= ω ₀ M / a = 2πf ₀ M / a at the drive frequency f ₀ of the inverter circuit 12, where M is a mutual inductance and f ₀ is a drive. Since the frequency, ω ₀ is the driving angular velocity), the primary side leakage reactance x ₁ ′, and the secondary side leakage reactance x ₂ are sufficiently small, if omitted, the simplified equivalent circuit of FIG. 3 is obtained.

In the simple equivalent circuit of FIG. 3, when the capacitance of the primary side capacitor 14 is C _S and the capacitance of the secondary side capacitor 22 is C _P , the respective capacitances C _S and C _P are determined as in the following equation (1).

At this time, the input voltage V _IN of the non-contact power feeding section 3 _'and the output voltage V _2, the non-contact input current I _IN of the power supply unit _3' when seeking the relationship between the output current I _L, the following equation (2) .

From the detailed equivalent circuit of FIG. 2 and the relationship of the above formula (2), the theoretical formula for obtaining the power transmission efficiency η of the non-contact power feeding unit 3 is the following formula (3). It can be seen that η depends on the resistance value _RL of the load 4. Here, iron loss due to r ₀ ′ is ignored.

When the above equation (3) is differentiated to obtain the resistance value R _Lmax that maximizes the power transmission efficiency η, the following equation (4) is obtained.

Here, the sharpness of resonance between the primary winding 13 and the secondary winding 21 is defined as Q ₁ and Q ₂ , respectively, and the coupling coefficient k is defined by the following equation (5).

And _{x P} of the equation (5) Equation (1) described above with reference to, Transforming b of formula (2), the following equation (6).

  Paying attention to the above equation (4) and transforming the equation within the square root of this equation (4), the following equation (7) is obtained.

  Therefore, in this equation (7), if the relationship of the following equation (8) is established, the value of 1 in the square root of the above equation (4) can be ignored. 9).

As is clear from the above equation (9), it can be seen that the resistance value R _{Lmax at} which the power transmission efficiency η is maximum depends on the value of the coupling coefficient k. Here, the case where the primary side capacitor 14 is connected in series to the primary side winding 13 and the secondary side capacitor 22 is connected in parallel to the secondary side winding 21 has been described. The resistance value R _Lmax that maximizes the power transmission efficiency η depends on the coupling coefficient k.

For example, when the primary side capacitor 14 is connected in parallel to the primary side winding 13 and the secondary side capacitor 22 is also connected in parallel to the secondary side winding 21, the above equation (9) is similarly established. . Further, when the primary side capacitor 14 is connected in parallel to the primary side winding 13 and the secondary side capacitor 22 is connected in series to the secondary side winding 21, or the primary side capacitor 14 is connected in series to the primary side winding 13. When the secondary side capacitor 22 is connected in series to the secondary side winding 21, the following equation (10) is established. In any case, it can be seen that the resistance value R _Lmax that maximizes the power transmission efficiency η depends on the coupling coefficient k.

Here, the load when the power supply side is viewed from the non-contact power feeding unit 3 is actually not only the load 4 connected to the power converter 25 but also a load such as the rectifier circuit 24 or the power converter 25. doing. Therefore, when determining the resistance value R _Lmax that maximizes the power transmission efficiency η in accordance with the coupling coefficient k, the combined load obtained by combining the load 4, the power converter 25, and the rectifier circuit 24 viewed from the non-contact power feeding unit 3. By appropriately adjusting the resistance value of the combined load in consideration of the resistance value of the power supply, it is possible to minimize the decrease in the power transmission efficiency η accompanying the change in the coupling coefficient k. Therefore, in the following, it is assumed that the resistance value R _Lmax that maximizes the power transmission efficiency η is for the combined load.

  Next, an equivalent circuit of the non-contact power feeding unit 3 when both ends of the secondary winding 21 are short-circuited by the secondary winding short-circuit means 23 is shown in FIG. The reason why the both ends of the secondary winding 21 are short-circuited is that the resistance components such as the rectifier circuit 24, the power converter 25, and the load 4 on the downstream side of the non-contact power feeding unit 3 are electrically disconnected, and the equivalent circuit of FIG. This is because the magnitude of the impedance of the inverter load shown | Z | and the value of the phase θ are obtained.

Since iron loss is very small, r ₀ ′ is ignored here. In addition, the advance primary side control circuit 18, the inductance L ₁ of the primary winding _13, resistor r _1, the number of turns N _1, assumed to be to store the respective information volume C _S of the primary side capacitor 14. Further, the secondary side control circuit 28 is assumed to be to store the respective information volume C _P of the secondary inductance L ₂ of the primary winding _21, resistor r _2, the number of turns N _2, the secondary-side capacitor 22 . Since each parameter of the power receiving device 2 can be transmitted to the primary side control circuit 18 of the power transmitting device 1 by the two communication units 19 and 29, the unknown parameter is a reactance x ₀ ′, x that varies depending on the coupling coefficient k. ₁ ', it is only _{x 2.}

If the value of the impedance | Z | and the phase θ of the inverter load shown in the equivalent circuit of FIG. 4 when the secondary winding 21 is short-circuited by the secondary winding short-circuit means 23 can be obtained. The inductance L _S when the secondary winding 21 is short-circuited from the values of | Z | and θ can be obtained by the following equation (11). However, x _S ′ is the reactance of the primary capacitor 14 converted to the secondary side, ω ₀ is the driving angular velocity (= 2πf ₀ ), and the values of these x _S ′ and ω ₀ are known.

Here, since the inductance L _O (= L ₁ ) of the primary side winding 13 is known, if the inductance L _S when the secondary side winding 21 is short-circuited is obtained by the above equation (11), the coupling is established. The coefficient k can be obtained from the following equation (12).

That is, if the magnitude | Z | and the phase θ of the inverter load impedance when the secondary winding 21 is short-circuited by the secondary winding short-circuit means 23, L _S can be obtained from the equation (11), and Since L _O (= L ₁ ) is known, the coupling coefficient k can be calculated from the equation (12). When the coupling coefficient k is determined, the resistance value R _Lmax that maximizes the power transmission efficiency η of the non-contact power feeding unit 3 can be determined from the above-described equations (9) and (10).

  Next, a method for detecting the magnitude | Z | of the inverter load impedance and the phase θ when both ends of the secondary winding 21 are short-circuited by the secondary winding short-circuit means 23 will be described.

  When the secondary-side winding 21 is short-circuited by the secondary-side winding short-circuit means 23, a control signal is output from the primary-side control circuit 18 to drive the inverter circuit 12 at a predetermined drive frequency for a short time. The drive voltage detector 15 and the drive current detector 16 detect the harmonically modulated drive voltage V and the drive current I output from the inverter circuit 12, respectively. The predetermined drive frequency when the inverter circuit 12 is driven by the control signal is a frequency that is sufficiently lower than the DC power supply 11 voltage or higher than the resonance frequency of the inverter load in order to prevent the inverter circuit 12 from being burned out. Is preferably selected.

  Next, a primary drive voltage V1 including a primary component having the same frequency as the drive frequency of the inverter circuit 12 from the drive voltage V and the drive current I detected by the detectors 15 and 16 by the primary component extraction means 17, and The primary drive current I1 is extracted.

  FIG. 5 shows an example of a waveform diagram of the drive voltage V and the drive current I detected by the drive voltage detector 15 and the drive current detector 16. In FIG. 5, the horizontal axis represents time, and the vertical axis represents drive voltage V and drive current I.

  The high-frequency modulated drive voltage V and the drive current I are generally expressed as a composite waveform including high-order frequency components that are integer multiples of the drive frequency. Therefore, the primary component extraction means 17 performs discrete Fourier transform on the drive voltage V and the drive current I shown in FIG. 5 detected by both detectors 15 and 16 using a sampling frequency that is an integral multiple of the drive frequency, for example. As a result, only the primary component of the drive voltage V and the drive current I, that is, the component having the same frequency as the drive frequency is extracted.

  In the case of FIG. 5, the primary component extraction means 17 performs the primary drive based on the drive voltage V and the drive current I in a time corresponding to a single cycle of the drive frequency of the inverter circuit 12 as shown in FIG. The voltage V1 and the primary drive current I1 are extracted. In addition, as a method and algorithm for extracting only the primary component from a signal having a plurality of higher-order frequency components in the primary component extraction means 17, for example, a drive voltage V using, for example, generally commercially available software for discrete Fourier transform , And only the primary components V1, I1 of the drive current I can be extracted.

  The drive voltage V having the same frequency as the drive frequency of the inverter circuit 12 extracted by the primary component extraction means 17 and the primary components V1, I1 of the drive current I are displayed in complex numbers as in the following equation (13). .

Here, V1 indicates a primary drive voltage that is a primary component of the drive voltage V, and I1 indicates a primary drive current that is a primary component of the drive current I. V1 _Re and I1 _Re are the real parts of V1 and I1, V1 _Im and I1 _Im are V1 and the imaginary part of I1, and j is an imaginary unit.

  The magnitude of the impedance of the inverter load | Z | and the phase θ (the phases of the primary drive voltage V1 and the primary drive current I1) when the secondary winding 21 is short-circuited by the secondary winding short-circuit means 23 are as follows: (14).

  Here, Re (Z) and Im (Z) mean the real part and the imaginary part of the impedance Z, respectively. The drive voltage V and the phase θ of the drive current I may be calculated using arcsin or arccos instead of arctan. When the phase θ is around 90 °, arctan diverges and may contain many errors. Therefore, it may be preferable to calculate the phase θ using arcsin or arccos.

Thus, if the magnitude of the impedance | Z | and the value of the phase θ of the inverter load when the secondary winding 21 is short-circuited by the secondary winding short-circuit means 23, the value of the above equation (11 ), The coupling coefficient k can be calculated from the expression (12), and when the coupling coefficient k is determined, the power transmission efficiency η of the non-contact power feeding unit 3 is maximized from the above-described expressions (9) and (10). The resistance value R _Lmax can be determined.

As described above, when the power supply side is viewed from the non-contact power feeding unit 3, in fact, not only the load 4 but also a load such as the rectifier circuit 24 and the power converter 25 is attached. In setting the maximum resistance value R _Lmax , it is necessary to appropriately adjust the resistance value of the combined load obtained by combining the rectifier circuit 24, the power converter 25, and the load 4 as viewed from the non-contact power feeding unit 3. Hereinafter, a method for appropriately adjusting the resistance value of the combined load will be described.

First, as an example of the power converter 25, a simplified circuit diagram of a step-down converter is shown in FIG. 6, a simplified circuit diagram of a boost converter is shown in FIG. 7, and a simplified circuit diagram of a buck-boost converter is shown in FIG. In these figures, V _{C_IN} is an input voltage, I _{C_IN} is an input current, V _{C_OUT} is an output voltage, I _{C_OUT} is an output current, SW is a switching element, L is an inductor, D is a diode, and C is an electric field capacitor. ing.

Here, in the step-down converter as shown in FIG. 6, the relationship between the input voltage V _{C_IN} and the output voltage V _{C_OUT} uses the forward drop voltage V _F of the diode D and the duty of the control signal for turning on / off the switching element SW. Can be expressed by the following equation (15).

  Here, if the relationship of the following equation (16) is established, the above equation (15) can be approximated to the following equation (17).

  Furthermore, recent power converters 25 have been made highly efficient, and some have realized an efficiency η of 98% or more. Therefore, the following equation (18) is satisfied ignoring the loss of the power converter 25: Assume that.

When the equation (17) is substituted into the equation (18) and _rearranged , the relationship between the input current I _{C_IN} and the output current I _{C_OUT} can be expressed by the following equation (19).

Here, when organized prompted resistor _{R C_IN} with input current _{I C_IN} the input voltage _{V C_IN,} the relationship between the output resistor _{R C_OUT} the input resistor _{R C_IN} can be expressed by the following equation (20). From this equation (20), the input resistor _{R C_IN} is the value of the above output resistance _{R C_OUT,} and it can be seen that the ratio of the input resistor _{R C_IN} output resistance _{R C_OUT} relies on Duty.

Next, in the boost converter as shown in FIG. 7, the relationship between the input voltage V _{C_IN} and the output voltage V _{C_OUT} uses the forward drop voltage V _F of the diode D and the duty of the control signal for turning on / off the switching element SW. Can be expressed by the following equation (21).

  Here, if the relationship of the following equation (22) is established, the above equation (21) can be approximated to the following equation (23).

  Further, as in the case of the step-down converter, it is assumed that the following expression (24) is established by ignoring the loss of the power converter 25.

When the equation (23) is substituted into the above equation (24) and _rearranged , the relationship between the input current I _{C_IN} and the output current I _{C_OUT} can be expressed by the following equation (25).

Here, when organized prompted resistor _{R C_IN} with input current _{I C_IN} the input voltage _{V C_IN,} the relationship between the output resistor _{R C_OUT} the input resistor _{R C_IN} can be expressed by the following equation (26). From this equation (26), it can be seen that the input resistance _{RC_IN} has a value less than or equal to the output resistance _{RC_OUT} , and the ratio of the input resistance _{RC_IN} to the output resistance _{RC_OUT} depends on the duty.

Next, in the step-up / step-down converter as shown in FIG. 8, the relationship between the input voltage V _{C_IN} and the output voltage V _{C_OUT} is that the forward drop voltage V _F of the diode D and the duty of the control signal for turning on / off the switching element SW are set. And can be expressed by the following equation (27).

  Here, if the relationship of the following equation (28) is established, the above equation (27) can be approximated to the following equation (29).

  Further, as in the case of the step-down converter or the step-up converter, it is assumed that the following expression (30) is satisfied ignoring the loss of the power converter 25.

When the equation (29) is substituted into the above equation (30) and _rearranged , the relationship between the input current I _{C_IN} and the output current I _{C_OUT} can be expressed by the following equation (31).

Here, when organized prompted resistor _{R C_IN} with input current _{I C_IN} the input voltage _{V C_IN,} the relationship between the output resistor _{R C_OUT} the input resistor _{R C_IN} can be expressed by the following equation (32). From this equation (32), _whether the input resistance _{RC_IN} is equal to or less than the output resistance _{RC_OUT} depends on the size of the duty, and the ratio of the input resistance _{RC_IN} to the output resistance _{RC_OUT} is the duty. It turns out that it depends on.

  From the above, when the step-down converter is provided as the power converter 25, the resistance value can appear to be a larger value, and when the step-up converter is provided, the resistance value can appear to be a smaller value. In addition, it can be seen that when the buck-boost converter is provided, the resistance value can be made to appear larger or smaller. In any case, since each of these resistance values depends on the duty, the change of the resistance value by the power converter 25 can be adjusted by controlling the duty.

  Next, FIG. 9 shows a choke input type full bridge rectifier circuit as an example of the rectifier circuit 24.

In choke input type full bridge rectifier circuit as shown in Figure 9, increases the inductance of the inductor L is sufficiently, if the internal resistance of the inductor L and the diode D1~D4 is sufficiently small, the relationship between the input voltage _{V R - IN} output voltage _{V R_OUT} is It can be represented by the following formula (33). Incidentally, _{I R - IN} in FIG. 9 is an input _{current, I R_OUT} the output _{current, R R - IN} is the input _{resistance, R R_OUT} output resistance, C is a field capacitor.

  Furthermore, the efficiency of the rectifier circuit 24 in recent years has been improved, and some have realized an efficiency η of 99% or more. Therefore, if the loss of the rectifier circuit 24 is ignored and the following equation (34) is established: Assume.

Here, when organized prompted resistor _{R R - IN} with the input current _{I R - IN} and the input voltage _{V R - IN,} the relationship between the output resistance _{R R_OUT} the input resistor _{R R - IN,} can be expressed by the following equation (35). From this equation (35), the ratio of the output resistance _{R R_OUT} the input resistor _{R R - IN} is understood to be a constant (= 1.23).

Thus, if the rectifier circuit 24 in front of the input side of the power converter 25 is supplied with the formula showing the relationship between the input resistor _{R R - IN} and the output resistance _{R R_OUT} power converter 25 (20), formula (26 ), In equation (32), it is necessary to consider the amount of change in the resistance value caused by the rectifier circuit 24.

So far, the operation of each component of the non-contact power feeding device has been described.
From here, according to the flowchart shown in FIG. 10, the coupling coefficient k between the primary side winding 13 and the secondary side winding 21 is detected, and the power is based on the detected coupling coefficient k and the state of the load 4. A method for maximizing the power transmission efficiency η between the windings 13 and 21 of the non-contact power feeding unit 3 by optimally controlling the converter 25 will be described. In FIG. 10, the symbol S means each processing step.

First, as a start signal, a transmission start request is sent from the secondary control circuit 28 to the primary control circuit 18 by the communication means 29 and 19. In step S1, the inductance _{L 2,} the resistance _{r 2} of the pre-secondary-side control circuit 28 two or may be stored in the primary winding 21, the number of turns _{N 2,} each of the capacitance _{C P} of the secondary-side capacitor 22 The parameter information is sent to the primary side control circuit 18 by the communication means 29 and 19.

If the primary side and the secondary side are set as a set, the primary side control circuit 18 is previously provided with the inductance L ₁ of the primary side winding 13, the resistance r ₁ , the number of turns N ₁ , and the capacitance C _{S of the} primary side capacitor 14. the combined information and the inductance L ₂ of the secondary winding _21, resistor r _2, the number of turns N _2, by storing the information of the capacity C _P of the secondary-side capacitor 22, omitting the step S1 Can do.

  In step S <b> 2, the secondary side control circuit 28 short-circuits the secondary side winding 21 by the secondary side winding short circuit means 23, and then sends a short-circuit completion signal to the primary side control circuit 18 by the communication means 29 and 19. .

In step S3, when receiving a signal indicating completion of the short circuit, the primary side control circuit 18 outputs a control signal to the inverter circuit 12 in response thereto, and drives the inverter circuit 12 for a short time. Meanwhile, the drive voltage V and the drive current I of the inverter circuit 12 are detected by the drive voltage detector 15 and the drive current detector 16. The primary component extraction means 17 extracts the primary components V1 and I1 of the drive voltage V and the drive current I, and the secondary side winding short-circuit means 23 extracts the secondary side winding 21 based on the above-described equation (14). The magnitude of the impedance | Z | and the phase θ when short-circuited are obtained.
Here, when the inverter circuit 12 is driven, the voltage of the DC power source 11 is sufficiently lowered to prevent the circuit from being burned, or it is driven by selecting a driving frequency sufficiently higher than the resonance frequency of the inverter load. desirable.

  In step S <b> 4, the primary side control circuit 18 sends a request for opening the secondary side winding 21 to the secondary side control circuit 28 by the communication means 19 and 29. In response to this, the secondary side control circuit 28 opens the secondary side winding 21 short-circuited by the secondary side winding short-circuit means 23. Then, the secondary side control circuit 28 sends a signal of completion of opening to the primary side control circuit 18 by the communication means 29 and 19.

In step S5, when the primary control circuit 18 receives the signal indicating the completion of opening, the primary side control circuit 18 uses the impedance magnitude | Z | measured in the previous step S3 and the value of the phase θ in response to the signal (11). And the coupling coefficient k is calculated based on the equation (12). Subsequently, the primary side control circuit 18 calculates a resistance value R _Lmax that maximizes the power transmission efficiency η based on the information obtained in step S1 and the coupling coefficient k based on the equations (5) and (9) _. .

In step S6, the primary side control circuit 18 sends information on the resistance value _RLmax that maximizes the power transmission efficiency η calculated in step S5 to the secondary side control circuit 28 by the communication means 19 and 29. In addition, about step S4, S5, S6, you may process in the procedure of step S5->S4-> S6 or step S5->S6-> S4.

In step S <b> 7, the primary side control circuit 18 starts transmission by sending a control signal to the inverter circuit 12, and the secondary side control circuit 28 sends a control signal to the power converter 25. Even when the resistance value _RL of the load 4 is small by starting the power transmission by starting with the output power of the inverter circuit 12 set to the minimum value and the duty of the power converter 25 set to the minimum value. The non-contact power feeding device can be activated safely.

In step S <b> 8, the secondary side control circuit 28 measures the current resistance value _RL of the load 4 from the detected values of the output voltage detector 26 and the output current detector 27.

In step S9, the secondary side control circuit 28 has information on the resistance value _RL of the load 4 detected in step S8 and information on the resistance value _RLmax that maximizes the power transmission efficiency η obtained in step S6 _. From this, the duty of the power converter 25 that can maximize the power transmission efficiency η of the non-contact power feeding unit 3 is obtained by solving the duty using the following equation (36).

Here, the numerical value 1.23 corresponds to a change in the resistance value when the rectifier circuit 24 is a choke input type full-bridge rectifier circuit 24. Further, (1 / Duty ² ) when the power converter 25 is a step-down converter corresponds to the equation (20), and (1-Duty) ² when the power converter 25 is a step-up converter corresponds to the equation (26). Further, {(1-Duty) / Duty} ^{2 in} the case of the step-up / step-down converter corresponds to the amount of change in the resistance value corresponding to the equation (32). Since R _Lmax and R _L are already known from steps S5 and S8, respectively, the duty of the power converter 25 that can maximize the power transmission efficiency η of the non-contact power feeding unit 3 is calculated using the equation (36). Can be sought.
However, when the power converter 25 is a step-down converter or a step-up converter, a solution may not be obtained. In that case, the step-down converter has a duty as close to 1 as possible and the step-up converter has a feasible value. Duty is selected to a feasible value as close to 0 as possible.

  In step S10, the secondary side control circuit 28 updates the duty of the power converter 25 to the value obtained in step S9.

As described above, the power transmission efficiency η of the non-contact power feeding unit 3 can be maximized in accordance with the coupling coefficient k. However, when the resistance value _RL of the load 4 is known, step S8 can be omitted. Further, when the resistance value _RL of the load 4 is not constant and changes over time, the power transmission efficiency η of the non-contact power feeding unit 3 is not affected by the change of the load 4 by repeating steps S8 to S10. Can be maximized.

  The present invention is not limited to the configuration of the first embodiment described above, and various modifications can be made or a part of the configuration can be omitted without departing from the spirit of the present invention. .

DESCRIPTION OF SYMBOLS 1 Power transmission device, 2 Power receiving device, 3 Non-contact electric power feeding part, 4 Load, 11 DC power supply,
12 inverter circuit, 13 primary winding, 14 primary capacitor,
15 drive voltage detector, 16 drive current detector, 17 primary component extraction means,
18 Primary side control circuit, 19 Primary side communication means, 21 Secondary side winding,
22 secondary capacitor, 23 secondary winding short-circuit means, 24 rectifier circuit,
25 power converter, 26 output voltage detector, 27 output current detector,
28 secondary side control circuit, 29 secondary side communication means, η power transmission efficiency, k coupling coefficient,
The current resistance value of the _RL load, the resistance value that maximizes the _RLmax power transmission efficiency.

Claims (5)

An inverter circuit that outputs high-frequency power; a non-contact power feeding unit that transmits and receives the high-frequency power supplied from the inverter circuit by electromagnetic induction through a spatial gap; and the high-frequency power that is transmitted and received by the non-contact power feeding unit A rectifier circuit that converts electric power to DC power; and a power converter that arbitrarily changes the voltage of the DC power output from the rectifier circuit and outputs the voltage to a load. A primary winding that resonates and transmits high-frequency power supplied from the inverter circuit, and a secondary winding that resonates with a secondary capacitor and receives high-frequency power transmitted from the primary winding. A non-contact power feeding device having
A secondary winding short-circuit means for short-circuiting both ends of the secondary winding at an arbitrary timing;
Drive voltage detection means for detecting the drive voltage of the inverter circuit;
Drive current detection means for detecting the drive current of the inverter circuit;
A primary drive voltage and primary drive current including a primary component having the same frequency as the drive frequency of the inverter circuit based on the drive voltage and drive current detected by the drive voltage detection means and the drive current detection means Component extraction means;
The inverter circuit is controlled, and the values of the primary driving voltage and the primary driving current extracted by the primary component extracting means when the secondary winding is short-circuited by the secondary winding short-circuiting means are set. A primary side control circuit that calculates a resistance value R _Lmax that maximizes the coupling coefficient k and the power transmission efficiency η of the non-contact power feeding unit based on
Communication means for transmitting and receiving information on the resistance value R _Lmax calculated by the primary side control circuit;
A secondary side control circuit for controlling the operation of the power converter based on the value of the resistance value _RLmax received through the communication means, while controlling the operation of the secondary side winding short circuit means;
Contactless power supply device with Output voltage detecting means for detecting the output voltage of the power converter;
Output current detection means for detecting the output current of the power converter;
With
The secondary side control circuit calculates the current resistance value _RL of the load connected to the power converter based on the detection outputs of the output voltage detection means and the output current detection means. The contactless power feeding device according to claim 1, wherein the operation of the power converter is controlled based on the calculated resistance value R _L and the resistance value R _Lmax received by the communication means _. . The power converter is a step-down converter, and duty when driving the step-down converter by the secondary side control circuit is R _Lmax = 1.23 × (1 / Duty ² ) × R _L (where _RL is 3. The non-contact power feeding apparatus according to claim 1, wherein the current resistance value is determined by solving for Duty. The power converter is a boost converter, and Duty when driving the boost converter by the secondary side control circuit is R _Lmax = 1.23 × (1−Duty) ² × R _L (where R _L is 3. The non-contact power feeding apparatus according to claim 1, wherein the current resistance value is determined by solving for Duty. The power converter is a step-up / step-down converter, and Duty when driving the step-up / down converter by the secondary side control circuit is R _Lmax = 1.23 × {(1-Duty) / Duty} ² × R _L The non-contact power feeding device according to claim 1 or 2, wherein R _L is determined by solving an equation of Duty for Duty, wherein _RL is a resistance value of a current load.

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