Wireless power supply inverter, control method for wireless power supply inverter, and wireless power supply device

Abstract

To suppress the deterioration of the load power factor of a composite resonant circuit connected to a wireless power supply inverter and to improve the load power factor of the composite resonant circuit.SOLUTION: The wireless power supply inverter using a composite resonant circuit having a power transmission resonant circuit and a power reception resonant circuit includes an inverter circuit to which the composite resonant circuit having the power transmission resonant circuit and the power reception resonant circuit is connected, and control means for controlling the operation of the inverter circuit. The control means operates the inverter circuit at n (where "n" is a positive integer of 2 or greater) different frequencies within a preset frequency range m times or less ("m" is a positive integer, where m≤n) for a short time. It measures the load power factor and load impedance of the composite resonant circuit during these short-duration operations. On the basis of the comparison results of the measured load power factor and load impedance against the thresholds, it selects the output frequency.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to an inverter for wireless power supply, a control method for the inverter for wireless power supply, and a wireless power supply device.

[0002] More specifically, the present invention relates to an inverter for wireless power supply that uses a composite resonance circuit having a power transmission resonance circuit and a power reception resonance circuit, a control method for the inverter for wireless power supply, and a wireless power supply device including the inverter for wireless power supply.

Background Art

[0003] Conventionally, as a wireless power supply device for supplying power to various power supply targets such as a battery mounted on an electric vehicle (EV: Electric Vehicle), for example, a wireless power supply device having a configuration shown in FIG. 1 is known.

[0004] That is, FIG. 1 shows a configuration explanatory diagram of a wireless power supply device including a fixed single-frequency inverter, which is a conventionally known inverter for wireless power supply.

[0005] The wireless power supply device 100 shown in Figure 1 comprises an AC power supply (in Figure 1, a three-phase AC power supply is shown) 102, a converter 104 connected to the AC power supply 102 that receives the AC voltage supplied from the AC power supply 102, converts it to a DC voltage, and outputs it, a conventionally known wireless power supply inverter (for convenience of explanation, this conventionally known wireless power supply inverter will be referred to as a "fixed single-frequency inverter") 106 connected to the converter 104 that receives the DC voltage output from the converter 104, converts it inversely to a high-frequency AC voltage, and outputs it, a composite resonant circuit 108 connected to the fixed single-frequency inverter 106 that transmits and receives power from the output of the fixed single-frequency inverter 106, a rectifier circuit 110 connected to the composite resonant circuit 108 that rectifies the output from the composite resonant circuit 108, and a battery 112 mounted on an EV, which is the power supply target, connected to the rectifier circuit 110 and receives power from the output of the rectifier circuit 110.

[0006] Here, the fixed single-frequency inverter 106 mentioned above refers to an inverter whose output frequency is constant, or in other words, whose output frequency is fixed at a specific single frequency.

[0007] Furthermore, the composite resonant circuit 108 is configured to include a power transmission resonant circuit (power transmission coil) 108a connected to the fixed single-frequency inverter 106 side, and a power receiving resonant circuit (power receiving coil) 108b connected to the rectifier circuit 110 side.

[0008] In the above configuration, the wireless power supply device 100 described above can supply power from the AC power supply 102 to the battery 112.

[0009] However, in the wireless power supply device 100 described above, the fixed single-frequency inverter 106, which is the inverter for wireless power supply, has a fixed output frequency of one frequency. Therefore, if the distance L between the transmitting resonant circuit 108a and the receiving resonant circuit 108b that constitute the composite resonant circuit 108 changes, that is, if the distance L between the transmitting and receiving coils changes, the coupling coefficient k determined by the distance L changes, the load power factor of the composite resonant circuit 108 deteriorates.

[0010] When the load power factor of the composite resonant circuit 108 deteriorates in this way, the output kVA of the fixed single-frequency inverter 106 increases, leading to an increase in output current, or the output loss of the fixed single-frequency inverter 106 increases. This leads to problems such as an increase in the allowable power loss of the switching elements in the inverter circuit constituting the fixed single-frequency inverter 106, an increase in output current, and an increase in output noise.

[0011] In wireless power supply for EVs, it is generally advisable to avoid changing the frequency during power supply operation, such as for noise prevention, and to operate at a fixed frequency.

[0012] Furthermore, since the prior art known to the applicant at the time of filing the patent application is not an invention related to a publicly known invention, there is no prior art document information to be included in the specification of this application. [Overview of the project] [Problems that the invention aims to solve]

[0013] The present invention has been made in view of the various problems of the prior art described above, and its objective is to provide a wireless power supply inverter that suppresses deterioration of the load power factor of a composite resonant circuit connected to a wireless power supply inverter and improves the load power factor of said composite resonant circuit, a control method for said wireless power supply inverter, and a wireless power supply device equipped with said wireless power supply inverter. [Means for solving the problem]

[0014] To achieve the above objective, the present invention provides a wireless power supply inverter for use in a wireless power supply device having a composite resonant circuit, wherein the output frequency of the wireless power supply inverter is selected based on measured values ​​of the load power factor and load impedance of the composite resonant circuit connected to the wireless power supply inverter, thereby suppressing deterioration of the load power factor of the composite resonant circuit and improving the load power factor of the composite resonant circuit.

[0015] Accordingly, according to the present invention, an output frequency is selected as the output frequency of the wireless power supply inverter that can suppress the deterioration of the load power factor of the composite resonant circuit and improve the load power factor of the composite resonant circuit. By determining the selected output frequency as the output frequency during power supply operation and performing the power supply operation, it becomes possible to suppress the deterioration of the load power factor of the composite resonant circuit and improve the load power factor of the composite resonant circuit, thereby eliminating adverse effects such as an increase in the allowable power loss of the switching elements of the inverter circuit, an increase in output current, and an increase in output noise.

[0016] In other words, the wireless power supply inverter according to the present invention is a wireless power supply inverter that uses a composite resonant circuit having a power transmission resonant circuit and a power reception resonant circuit connected together, and comprises an inverter circuit to which the composite resonant circuit having a power transmission resonant circuit and a power reception resonant circuit is connected, and a control means for controlling the operation of the inverter circuit, wherein the control means operates the inverter circuit for a short time only m times or less at n (where "n" is a positive integer of 2 or more) different frequencies within a preset frequency range, measures the load power factor and load impedance of the composite resonant circuit during the short-time operation, and selects an output frequency based on the comparison result obtained by comparing the measured load power factor and load impedance with their respective thresholds.

[0017] Furthermore, the wireless power supply inverter according to the present invention is configured to perform a short-time operation (m=1) for the first time at a frequency in the mid-range of the preset frequency range described above.

[0018] Furthermore, the wireless power supply inverter according to the present invention is configured such that, when the comparison result is that the load power factor is greater than or equal to a threshold, a frequency at which the load power factor is greater than or equal to a threshold is selected as the output frequency, and when the comparison result is that the load power factor is less than or equal to a threshold, a frequency at which the load impedance is greater than or equal to a threshold is selected as the output frequency.

[0019] Furthermore, the wireless power supply inverter according to the present invention is modified so that when switching frequencies for short periods of operation of m times or less, the output of the inverter circuit is turned off before switching frequencies.

[0020] Furthermore, the wireless power supply inverter according to the present invention is modified so that, when switching frequencies for short periods of operation of m times or less, the output of the inverter circuit is reduced without first turning off the inverter circuit, and the frequency is switched while the output of the inverter circuit is reduced.

[0021] Furthermore, the control method for a wireless power supply inverter according to the present invention is a control method for a wireless power supply inverter that uses a composite resonant circuit having a power transmission resonant circuit and a power receiving resonant circuit connected together, wherein the inverter circuit is operated for a short time only m times or less at n (where "n" is a positive integer of 2 or more) different frequencies within a preset frequency range, the load power factor and load impedance of the composite resonant circuit are measured during the short-time operation, and the output frequency is selected based on the comparison result obtained by comparing the measured load power factor and load impedance with their respective thresholds.

[0022] Furthermore, the control method for the wireless power supply inverter according to the present invention is the same as the control method for the wireless power supply inverter according to the present invention described above, but with the first operation (m=1) performed for a short time at a frequency in the frequency band near the middle of the preset frequency range.

[0023] Furthermore, the control method for a wireless power supply inverter according to the present invention is configured such that, when the comparison result is that the load power factor is greater than or equal to a threshold, a frequency at which the load power factor is greater than or equal to a threshold is selected as the output frequency, and when the comparison result is that the load power factor is less than or equal to a threshold, a frequency at which the load impedance is greater than or equal to a threshold is selected as the output frequency.

[0024] Furthermore, the control method for the wireless power supply inverter according to the present invention is modified so that when switching frequencies for short periods of operation of m times or less, the output of the inverter circuit is turned off before switching frequencies.

[0025] Also, in the control method of the wireless power supply inverter according to the present invention, when switching the frequency during the short-time operation only m times or less, the output of the inverter circuit is switched without once turning off the output of the inverter circuit, but with the output of the inverter circuit lowered.

[0026] Further, the wireless power supply device according to the present invention is a wireless power supply device including a wireless power supply inverter that uses a composite resonance circuit having a power transmission resonance circuit and a power reception resonance circuit. The wireless power supply inverter that uses a composite resonance circuit having a power transmission resonance circuit and a power reception resonance circuit is the wireless power supply inverter according to the present invention as described above.

Advantages of the Invention

[0027] Since the present invention is configured as described above, it is possible to suppress the deterioration of the load power factor of the composite resonance circuit connected to the wireless power supply inverter and to improve the load power factor of the composite resonance circuit, which is an excellent effect.

Brief Description of the Drawings

[0028] [Figure 1] FIG. 1 is a configuration explanatory diagram of a wireless power supply device including a fixed single-frequency inverter, which is a conventionally known wireless power supply inverter. [Figure 2] FIG. 2 is a configuration explanatory diagram of a wireless power supply device including a power factor improvement frequency selection inverter, which is a wireless power supply inverter according to an example of an embodiment of the present invention. [Figure 3] FIG. 3 is a configuration explanatory diagram showing an example of the configuration of the power factor improvement frequency selection inverter in FIG. 2. [Figure 4] FIG. 4 is a configuration explanatory diagram of a wireless power supply device showing an example when the control unit of the power factor improvement frequency selection inverter shown in FIG. 3 is configured by a circuit. [Figure 5]Figure 5 is a graph showing an example of the frequency characteristics of the load power factor and load impedance of a composite resonant circuit connected to the power factor correction frequency selector inverter of the wireless power supply device shown in Figure 1, and is a graph showing an example where the coupling coefficient k between the transmitting resonant circuit and the receiving resonant circuit is "0.087". [Figure 6] Figure 6 is a graph showing an example of the frequency characteristics of the load power factor and load impedance of a composite resonant circuit connected to the power factor correction frequency selector inverter of the wireless power supply device shown in Figure 1, and is a graph showing an example where the coupling coefficient k between the transmitting resonant circuit and the receiving resonant circuit is "0.145". [Figure 7] Figure 7 is a graph showing an example of the frequency characteristics of the load power factor and load impedance of a composite resonant circuit connected to the power factor correction frequency selector inverter of the wireless power supply device shown in Figure 1, and is a graph showing an example where the coupling coefficient k between the transmitting resonant circuit and the receiving resonant circuit is "0.229". [Figure 8] Figure 8 is a graph showing an example of the frequency characteristics of the load power factor and load impedance of a composite resonant circuit connected to the power factor correction frequency selector inverter of the wireless power supply device shown in Figure 1, and is a graph showing an example where the coupling coefficient k between the transmitting resonant circuit and the receiving resonant circuit is "0.3". [Figure 9] Figure 9 is a graph showing an example of the characteristics of the load power factor and load impedance of a composite resonant circuit when the wireless power transfer device shown in Figure 1 is operated at a frequency of 85 kHz. [Figure 10] Figure 10 is a diagram showing an example of a table used when selecting the output frequency during power supply operation in the wireless power supply device shown in Figure 1. [Figure 11] Figure 11 is a graph showing an example of the relationship between the load power factor and output characteristics with respect to the coupling coefficient in the wireless power transfer device shown in Figure 1. [Modes for carrying out the invention]

[0029] Hereinafter, an example of an embodiment of the wireless power supply inverter, the control method for the wireless power supply inverter, and the wireless power supply device according to the present invention will be described in detail with reference to the attached drawings.

[0030] In the following description of "Modes for Carrying Out the Invention," configurations and operations that are the same as or equivalent to those described with reference to Figure 1 will be indicated by the same reference numerals used in Figure 1, and detailed descriptions of those configurations and operations will be omitted.

[0031] (I) Description of the configuration and operation of a wireless power supply inverter and wireless power supply device according to an example of an embodiment of the present invention. Figure 2 shows an explanatory diagram of the configuration of a wireless power supply device equipped with a power factor correction frequency selector inverter, which is an inverter for wireless power supply according to an example of an embodiment of the present invention.

[0032] Furthermore, Figure 3 shows an explanatory diagram illustrating an example of the configuration of the power factor correction frequency selection inverter shown in Figure 2.

[0033] Furthermore, Figure 4 shows an explanatory diagram of the configuration of a wireless power supply device, illustrating an example of how the control unit of the power factor correction frequency selector inverter shown in Figure 3 can be configured as a circuit.

[0034] A wireless power supply device 10 according to one embodiment of the present invention differs from a conventional wireless power supply device 100 in that it is equipped with a wireless power supply inverter (for convenience of explanation, the wireless power supply inverter according to the present invention will be referred to as a "power factor correction frequency selector inverter") 12 instead of a fixed single-frequency inverter 106.

[0035] Unlike the fixed single-frequency inverter 106, this power factor correction frequency selector inverter 12 is an inverter capable of varying its output frequency. It consists of an inverter circuit 12a connected between the converter 104 and the composite resonant circuit 108 to perform inverter operation, and a control unit 12b that controls the inverter circuit 12a.

[0036] The control unit 12b, in a wireless power supply device 10 equipped with a composite resonant circuit 108 connected to a power factor correction frequency selection inverter 12, operates the inverter circuit 12a for a short period of m (where "m" is a positive integer, but "m ≤ n") times or less using n (where "n" is a positive integer of "2" or more) different output frequencies within a preset frequency range. During this short period of operation, it measures two values, the load power factor and the load impedance of the composite resonant circuit 108 connected to the power factor correction frequency selection inverter 12, and obtains these measured values. By comparing the two obtained measured values ​​with the threshold values ​​of each measured value, it selects an output frequency that improves the load power factor of the composite resonant circuit 108. The control unit 12b determines this selected output frequency as the output frequency when the power factor correction frequency selection inverter 12 performs power supply operation, and controls the inverter circuit 12a to operate at the determined output frequency to supply power to the battery 112.

[0037] Here, the pre-set frequency range mentioned above can be determined, for example, by the standard to which the wireless power supply device 10 conforms. For example, if it conforms to the SAE standard, the pre-set frequency range will be "79kHz to 90kHz".

[0038] Furthermore, the control unit 12b operates the inverter circuit 12a for a short time, but only m times or less. The number of "m times" is the number of times until an output frequency that can improve load efficiency is selected and determined. The fewer the number of "m times", the shorter the processing time can be, so it is preferable to have a small number of "m times".

[0039] Furthermore, the control unit 12b operates the inverter circuit 12a for a short time, m times or less. This "short-time operation" is not intended to supply power to the battery 112, but rather refers to the shortest time necessary to measure the two values ​​of the composite resonant circuit 108: the load power factor and the load impedance.

[0040] Furthermore, the process of comparing the two measured values ​​of the composite resonant circuit 108—the load power factor and the load impedance—with the threshold values ​​of each measured value, and selecting an output frequency that improves the load power factor of the composite resonant circuit 108, will be described in detail later.

[0041] The load power factor threshold and the load impedance threshold are arbitrary values ​​set in advance. For example, if the wireless power supply device 10 conforms to the SAE standard, the load power factor threshold can be set to "0.7", and the load impedance threshold can be set to "13Ω".

[0042] The control unit 12b described above can be constructed, for example, by a circuit configuration as shown in Figure 4.

[0043] The following explanation will describe how to construct the control unit 12b using a circuit configuration, referring to Figure 4. The numbers (1) to (7) in Figure 4 indicate the order of operation, meaning that the operation proceeds in ascending order from (1) to (7).

[0044] The control unit 12b is configured to include a DC power detection unit 122 connected to a DC power detector 14 positioned between the converter 104 and the inverter circuit 12a, an output voltage detection unit 124 connected to an output voltage detector 16, an output current detection unit 126 connected to an output current detector 18, a divider 128 connected to the output voltage detection unit 124 and the output current detection unit 126, a multiplier 130 connected to the output voltage detection unit 124 and the output current detection unit 126, a divider 132 connected to the DC power detection unit 122 and the multiplier 130, a power factor acquisition unit 134 connected to the divider 132, an impedance acquisition unit 136 connected to the divider 128, a power factor threshold comparison and determination circuit 138 connected to the power factor acquisition unit 134, an impedance threshold comparison and frequency determination circuit 140 connected to the impedance acquisition unit 136, a continuous power supply instruction unit 142, and an m-th frequency setting unit 144.

[0045] In the control unit 12b, first, the m-th frequency setting unit 144 is set to an initial value of "m=1", and the inverter circuit 12a is operated for a short time using one of the n frequencies within the pre-set frequency range as the output frequency.

[0046] The output voltage V and output current I of the inverter circuit 12a during this short-time operation are detected by the output voltage detection unit 124 and the output current detection unit 126, respectively, and the impedance Z (Z=V / I) is calculated by the divider 128.

[0047] At the same time, the output voltage V and output current I of the inverter circuit 12a are detected by the output voltage detection unit 124 and the output current detection unit 126, respectively, and the multiplier 130 performs the calculation "V × I". The DC power detection unit 122 detects the DC power P of the input stage of the inverter circuit 12a, and the division unit 132 calculates the power factor (power factor = P / (V × I)) using "V × I".

[0048] Here, the inverter output has a high-frequency distorted waveform, resulting in poor measurement accuracy. Therefore, when determining the power factor, the DC power of the input stage of the inverter circuit is generally used as the inverter output power, as inverter losses are small.

[0049] The power factor calculated by the divider 132 is acquired by the power factor acquisition unit 134 as the target for determination in the power factor threshold comparison and determination circuit 138, and is input to the power factor threshold comparison and determination circuit 138.

[0050] The operation of the power factor threshold comparison and determination circuit 138 and the impedance threshold comparison and frequency determination circuit 140 will be described in detail later, but the general outline is as follows.

[0051] Specifically, the power factor threshold comparison and determination circuit 138 determines the input power factor against the threshold, and if it is determined that the input power factor is equal to or greater than the threshold (power factor OK), the continuous power supply instruction unit 142 controls the inverter circuit 12a to operate with the frequency at which it was briefly operated as described above as the output frequency, thereby providing continuous power to the battery 112.

[0052] On the other hand, if the power factor threshold comparison and determination circuit 138 determines that the input power factor is below the threshold (power factor NG), the impedance threshold comparison and frequency determination circuit 140 performs a determination between the input impedance and the threshold.

[0053] Specifically, the impedance threshold comparison and frequency determination circuit 140 determines the input impedance against a threshold, and if it is determined that the input impedance is equal to or greater than the threshold (impedance OK), the continuous power supply instruction unit 142 controls the inverter circuit 12a to operate at the frequency at which it was briefly operated as described above, thereby providing continuous power to the battery 112.

[0054] On the other hand, in the impedance threshold comparison / frequency determination circuit 140, if it is determined that the input impedance is below the threshold (impedance NG), the m-th frequency setting unit 144 is set to "m=2", and the inverter circuit 12a is operated for a short time using one of the n frequencies in the preset frequency range, other than the frequency used when "m=1", as the output frequency. This operation is repeated by incrementing m by "1" to select n different frequencies.

[0055] (II) Description of an example of operation of a wireless power supply inverter and wireless power supply device according to an embodiment of the present invention. Figure 5 is a graph showing an example of the frequency characteristics of the load power factor and load impedance of a composite resonant circuit connected to the power factor correction frequency selector inverter of the wireless power supply device shown in Figure 1. The graph shows an example where the coupling coefficient k between the transmitting resonant circuit and the receiving resonant circuit is "0.087".

[0056] Furthermore, Figure 6 is a graph showing an example of the frequency characteristics of the load power factor and load impedance of a composite resonant circuit connected to the power factor correction frequency selector inverter of the wireless power supply device shown in Figure 1. The graph shows an example where the coupling coefficient k between the transmitting resonant circuit and the receiving resonant circuit is "0.145".

[0057] Furthermore, Figure 7 is a graph showing an example of the frequency characteristics of the load power factor and load impedance of a composite resonant circuit connected to the power factor correction frequency selector inverter of the wireless power supply device shown in Figure 1. The graph shows an example where the coupling coefficient k between the transmitting resonant circuit and the receiving resonant circuit is "0.229".

[0058] Furthermore, Figure 8 is a graph showing an example of the frequency characteristics of the load power factor and load impedance of a composite resonant circuit connected to the power factor correction frequency selector inverter of the wireless power supply device shown in Figure 1. The graph shows an example where the coupling coefficient k between the transmitting resonant circuit and the receiving resonant circuit is "0.3".

[0059] Furthermore, Figure 9 shows a graph illustrating an example of the characteristics of the load power factor and load impedance of a composite resonant circuit when the wireless power transfer device shown in Figure 1 is operated at a frequency of 85 kHz.

[0060] Furthermore, Figure 10 shows an example of a table used when selecting the output frequency during power supply operation in the wireless power supply device shown in Figure 1.

[0061] Here, the coupling coefficient k is a constant determined by the distance L, which is the clearance between the transmitting resonant circuit 108a and the receiving resonant circuit 108b that constitute the composite resonant circuit 108, that is, the clearance between the transmitting coil and the receiving coil, as described above. In the examples shown in Figures 5 to 8, the coupling coefficient is within the range used by typical EVs.

[0062] Furthermore, in Figures 5 to 8, solid lines represent the load power factor, and dashed lines represent the load impedance.

[0063] Here, as explained above with reference to Figure 4, by measuring the inverter output power P (W), the output voltage V (Vrms), and the output current I (Arms), the load impedance (Z) = V / I Load power factor=P / (V×A) This can be obtained through calculation.

[0064] Next, we will explain the processing method for determining the frequency, which is performed by the power factor threshold comparison and determination circuit 138 and the impedance threshold comparison and frequency determination circuit 140 described above.

[0065] To facilitate understanding of the present invention, in this wireless power supply device 10, the preset frequency range is set to "79kHz~90kHz", and three frequencies, "81kHz", "85kHz", and "88kHz", are set as selectable frequencies with "n=3".

[0066] First, with "m=1", the first wireless power transfer is performed for a short time at 85kHz, and the inverter output power P, output voltage V, and output current I are measured. The load power factor and load impedance Z are then calculated (see Figure 9) and compared with their respective threshold values.

[0067] In this embodiment, the load power factor threshold is set to "0.7" and the load impedance Z threshold is set to "13Ω".

[0068] Here, based on the table shown in Figure 10, you can select a frequency that improves the load power factor.

[0069] In other words, when the first wireless power transfer is performed for a short time at 85kHz with "m=1", if the load power factor in the table shown in Figure 10 is 0.7 or higher, then 85kHz is selected as the output frequency and the power transfer operation is performed.

[0070] On the other hand, when the first wireless power transfer is performed for a short time at 85kHz with "m=1", even if the load power factor is less than the threshold of 0.7, if the load impedance value is 13Ω or higher in the table shown in Figure 10, 85kHz is selected as the output frequency and the power transfer operation is performed.

[0071] If, as described above, the first wireless power transfer is performed for a short time at 85kHz with "m=1", and it is not possible to select the output frequency and perform the power transfer operation, then the second wireless power transfer is performed for a short time at 81kHz with "m=2", and the same process as described above is performed.

[0072] Furthermore, if, when "m=2" is set and a second wireless power transfer is performed at 81kHz for a short period of time, it is not possible to select the output frequency and perform the power transfer operation, then "m=3" is set and a third wireless power transfer is performed at 88kHz for a short period of time, and the same process as described above is performed.

[0073] If the above process fails to select the output frequency and perform the power supply operation, the process will terminate as an operation error.

[0074] In other words, if a load power factor above a threshold is measured during a short-term power supply to the inverter circuit 12a, the frequency used during that short-term power supply is selected as the output frequency and power supply is continued. On the other hand, if a load power factor below a threshold is measured during that short-term power supply, the output frequency is determined based on the measured value of the load impedance and power is supplied. Thus, when selecting the output frequency, the load power factor is given priority in the determination.

[0075] Furthermore, as shown in Figure 11, it is understood that even if the coupling coefficient changes, the load power factor improves and the output also improves at the selected frequency.

[0076] (III) Description of the operation and effects of a wireless power supply inverter and wireless power supply device according to an example of an embodiment of the present invention. As explained above, in the wireless power supply device 10, since the composite resonant circuit 108 is connected to the power factor correction frequency selection inverter 12, n fixed frequencies can be set within a preset frequency range, and for each of the n fixed frequencies, power can be supplied for a short period of time m times or less to measure two values, the load power factor and load impedance of the composite resonant circuit 108, and by comparing these two measured values ​​with their respective thresholds, the frequency at which the load power factor is corrected can be selected and determined as the output frequency.

[0077] In other words, by first performing short-term power supply (m times or less) without the purpose of power supply operation, and selecting a frequency that improves the load power factor as the output frequency, it becomes possible to improve the load power factor and perform actual power supply operation.

[0078] Furthermore, in operating ranges with a good load power factor, it becomes possible to reduce the output current for the same output power, thereby reducing output noise and enabling miniaturization of the inverter circuit.

[0079] (IV) Description of other embodiments and variations The embodiments described above are merely illustrative, and the present invention can be implemented in various other forms. In other words, the present invention is not limited to the embodiments described above, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention.

[0080] For example, the above-described embodiment may be modified as shown in (IV-1) to (IV-6) below.

[0081] (IV-1) In the above-described embodiment, n different fixed frequencies are set within a preset frequency range, and the device is operated for a short time of m times or less at each of the n set different fixed frequencies. When setting the above-described frequency range, it is usually set so that the frequency with a high probability of improving the load power factor is located in the frequency band near the middle of the frequency range. For example, the first short-time power supply (m=1) is performed at a frequency in the frequency band near the middle of the preset frequency range, for example, at a frequency located in the middle of the frequency range, and the load power factor and load impedance of the composite resonant circuit 108 are measured. By comparing these two measured values ​​with their respective thresholds, it becomes possible to determine the frequency that efficiently improves the load power factor as the output frequency.

[0082] (IV-2) In the embodiments described above, detailed explanations have been omitted, but when switching frequencies for short-term power supply of m times or less, the output of the inverter circuit 12a may be turned off once before switching to another frequency and operating for a short time.

[0083] (IV-3) In the embodiments described above, detailed explanations have been omitted, but when switching frequencies during short-time power supply of m times or less, the output of the inverter circuit 12a may be reduced and switched to another frequency for short-time operation without turning off the output of the inverter circuit 12a.

[0084] (IV-4) In the embodiments described above, the case in which the control unit 12b is constructed with the circuit configuration shown in Figure 4 has been explained, but of course the configuration of the control unit 12b is not limited to this, and it may be implemented with a circuit configuration other than the one shown in Figure 4.

[0085] (IV-5) In the above-described embodiment, the case in which the control unit 12b is constructed using the circuit configuration shown in Figure 4 has been explained, but the control unit 12b may also be constructed using a computer system such as a microcomputer.

[0086] (IV-6) Of course, the embodiments described above and the embodiments shown in (IV-1) to (IV-5) above may be combined as appropriate. [Industrial applicability]

[0087] The present invention can be used in a wireless power supply inverter device and a wireless power supply device, which are power supply devices to which a composite resonant circuit is connected. [Explanation of Symbols]

[0088] 10 Wireless power supply device according to the present invention 12. Wireless power supply inverter according to the present invention (power factor correction frequency selector inverter) 12A Inverter Circuit 12b Control unit (control means) 14. DC power detector 16 Output Voltage Detector 18 Output current detector 100 Conventional wireless power supply devices 102 Alternating current (AC) power supply 104 converter 106 Conventional wireless power supply inverter (fixed single-frequency inverter) 108 Complex resonant circuit 108a Power transmission resonant circuit (power transmission coil) 108b Resonant power receiving circuit (receiving coil) 110 Rectifier circuit 112 batteries 122 DC power detection unit 124 Output Voltage Detection Section 126 Output current detection section 128 Division 130 Multiplier 132 Division 134 Power factor acquisition section 136 Impedance acquisition section 138 Power Factor Threshold Comparison and Judgment Circuit 140 Impedance threshold comparison and frequency determination circuit 142 Continuous power supply instruction unit 144th time frequency setting section L is the distance between the transmitting and receiving coils. k is a coupling coefficient determined by the distance L.

Claims

1. In a wireless power supply inverter that uses a composite resonant circuit having a power transmission resonant circuit and a power reception resonant circuit connected together, An inverter circuit to which a composite resonant circuit having a power transmission resonant circuit and a power reception resonant circuit is connected, Control means for controlling the operation of the inverter circuit and It has, The control means operates the inverter circuit for a short time no more than m times (where m ≤ n) at n (where n is a positive integer of 2 or more) different frequencies within a preset frequency range, measures the load power factor and load impedance of the composite resonant circuit during the short-time operation, and selects the output frequency based on the comparison result obtained by comparing the measured load power factor and load impedance with their respective threshold values. A wireless power supply inverter, The first (m=1) short-duration operation is performed at a frequency in the mid-range of the aforementioned preset frequency range. A wireless power supply inverter characterized by the following features.

2. In the wireless power supply inverter according to claim 1, When switching frequencies for short periods of operation (m times or less), the output of the inverter circuit is temporarily turned off before switching frequencies. A wireless power supply inverter characterized by the following features.

3. In the wireless power supply inverter according to claim 1, When switching frequencies for short periods of operation (m times or less), the frequency is switched while the output of the inverter circuit is reduced, without temporarily turning off the output of the inverter circuit. A wireless power supply inverter characterized by the following features.

4. In a control method for a wireless power supply inverter that uses a composite resonant circuit having a power transmission resonant circuit and a power reception resonant circuit, The inverter circuit is operated for a short time no more than m times (where m ≤ n) at n (where n is a positive integer greater than or equal to 2) different frequencies within a predetermined frequency range. The load power factor and load impedance of the composite resonant circuit are measured during these short-time operations, and the output frequency is selected based on the comparison result obtained by comparing the measured load power factor and load impedance with their respective threshold values. A control method for a wireless power supply inverter, The first (m=1) short-duration operation is performed at a frequency in the mid-range of the aforementioned preset frequency range. A control method for a wireless power supply inverter, characterized by the following features.

5. In the control method for a wireless power supply inverter according to claim 4, When switching frequencies for short periods of operation (m times or less), the output of the inverter circuit is temporarily turned off before switching frequencies. A control method for a wireless power supply inverter, characterized by the following features.

6. In the control method for a wireless power supply inverter according to claim 4, When switching frequencies for short periods of operation (m times or less), the frequency is switched while the output of the inverter circuit is reduced, without temporarily turning off the output of the inverter circuit. A control method for a wireless power supply inverter, characterized by the following features.

7. In a wireless power supply device equipped with a wireless power supply inverter that uses a composite resonant circuit having a power transmission resonant circuit and a power reception resonant circuit connected together, A wireless power supply inverter that uses a composite resonant circuit having a power transmission resonant circuit and a power reception resonant circuit connected together is the wireless power supply inverter according to any one of claims 1, 2, or 3. A wireless power supply device characterized by the following features.

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