Drive control device for a composite resonance circuit and non-contact power supply system

Abstract

To perform control to obtain an optimum operational frequency by using information on a power transmission side only, within a shorter period of time than that in a conventional technology.SOLUTION: A composite resonance circuit driving control device according to the present invention drivingly controls a composite resonance circuit consisting of a plurality of LC resonance circuits including inductances L of electromagnetically coupled power transmission / reception coils. The composite resonance circuit driving control device includes: an inverter circuit that drives the composite resonance circuit by switching an input DC power by a prescribed operational frequency to convert the DC power to AC power; an input current detector that detects an input current in the inverter circuit; and a frequency control and driving unit that drives the inverter circuit by generating a driving signal for the inverter circuit while changing the operational frequency by using a prescribed extreme value retrieving method, and retrieves the resonance frequency of the composite resonance circuit on the basis of the detected input current, and sets the operational frequency on the basis of the retrieved resonance frequency.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a drive control device for a composite resonance circuit including a plurality of resonance circuits, and a non-contact power supply system using the drive control device for the composite resonance circuit.

Background Art

[0002] Conventionally, for example, a moving body such as an automated guided vehicle (AGV) is equipped with a rechargeable battery such as a lithium-ion battery. When charging this rechargeable battery, after moving the AGV to a charging station, the power receiving coil mounted on the AGV is electromagnetically coupled to the power transmitting coil of the charging station to perform non-contact charging in a non-contact power supply system.

[0003] In the non-contact power supply system using the non-contact power supply, extensive studies have been conducted to improve convenience and safety. In the applications used, the positional relationship between the power transmitting and receiving coils may vary, and the resulting change in magnetic characteristics is one of the factors hindering the maintenance of high power conversion (supply) efficiency. Here, due to the change in the coupling coefficient k and the inductance L caused by the change in the positional relationship between the power transmitting and receiving coils, the resonance frequency changes, so the power conversion efficiency of the circuit deteriorates due to the decrease in transmission efficiency and power factor. Therefore, it is necessary to control to an optimal operating frequency according to the change in the positional relationship between the power transmitting and receiving coils.

[0004] And, for example, in the non-contact power supply system according to Patent Document 1, a method using information on the power receiving side is used to determine the optimal operating frequency.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the method of using the information on the power receiving side to determine the optimum operating frequency, communication between the power transmitting and receiving sides is required, and there is a problem that it takes time corresponding to the communication time.

[0007] An object of the present invention is to solve the above problems and to provide a drive control device for a composite resonance circuit that can control to an optimum operating frequency in a shorter time compared to the prior art by using only the information on the power transmitting side, and a non-contact power supply system using the drive control device for the composite resonance circuit.

Means for Solving the Problems

[0008] A drive control device for a composite resonance circuit according to an aspect of the present invention is a drive control device for a composite resonance circuit configured by a plurality of LC resonance circuits including an inductance L of power transmitting and receiving coils electromagnetically coupled to each other, an inverter circuit that converts the input DC power into AC power by switching it at a predetermined operating frequency and drives the composite resonance circuit, an input current detector that detects the input current of the inverter circuit, a frequency control and drive unit that generates a drive signal for the inverter circuit while changing the operating frequency using a predetermined extreme value search method, drives the inverter circuit, searches for the resonance frequency of the composite resonance circuit based on the detected input current, and sets the operating frequency based on the searched resonance frequency.

Effects of the Invention

[0009] Therefore, according to the drive control device for a composite resonance circuit according to the present invention, it is possible to control to an optimum operating frequency in a shorter time compared to the prior art by using only the information on the power transmitting side.

Brief Description of the Drawings

[0010]

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Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments and modification examples according to the present invention will be described with reference to the drawings. Note that the same or similar components are denoted by the same reference numerals.

[0012] (Findings of the Inventor) FIG. 3 is a circuit diagram showing a basic circuit of a non-contact power feeding system. In FIG. 3, an AC power supply 30 on the power transmission side is connected to a resistor RL via a power transmission side RLC resonance circuit which is a series circuit of a resistor R1, an inductor L1, and a capacitor C1, and a power reception side RLC resonance circuit which is a series circuit of a resistor R2, an inductor L2, and a capacitor C2. Here, the inductor L1 and the inductor L2 are electromagnetically coupled with a coupling coefficient k to form a transformer TR1. In the non-contact power feeding system configured as described above, AC power from the AC power supply 30 is transmitted to the resistor RL via the power transmission side RLC resonance circuit and the power reception side RLC resonance circuit.

[0013] FIG. 4 is a graph showing an example of the frequency characteristics of the transmission efficiency and the input power factor in the non-contact power supply system of FIG. 3. As is clear from FIG. 4, the resonance frequency changes due to the change in the coupling coefficient k and the inductance L caused by the variation in the positional relationship between the power transmission and reception coils (between the inductors L1 and L2). Therefore, the power conversion efficiency of the circuit deteriorates due to the decrease in the transmission efficiency or the input power factor. Thus, it is necessary to control the optimal operating frequency (the switching frequency of the inverter circuit) according to the variation in the positional relationship between the power transmission and reception coils. To solve this problem, the following non-contact power supply system has been devised.

[0014] (Embodiment) FIG. 1 is a block diagram showing a configuration example of a non-contact power supply system according to an embodiment.

[0015] In the non-contact power supply system of FIG. 1, by detecting the input current Iin of the power transmission device 100, a frequency search is performed to optimize the operating frequency (switching frequency) of the inverter circuit 12 every time the positional relationship between the power transmission coils (between the inductors L1 and L2) changes, and a drive control device for a composite resonance circuit that maximizes the power conversion efficiency is provided. Here, the optimal operating frequency is the operating frequency at which the transmission efficiency and the input power factor are maximum and zero-voltage switching (ZVS) operation is achieved. As a result, the following specific effects are obtained in this embodiment. (1) The DC / DC converter 23 of the power reception device 200 for maximizing the transmission efficiency can be deleted. In FIG. 1, for the sake of a modification example, the DC / DC converter 23 is inserted, but in this embodiment, it may be deleted as will be described in detail later. (2) Since the efficiency can be maximized in the power transmission device 100, it is not necessary to perform impedance matching by the DC / DC converter 23 in the power reception device 200.

[0016] For example, in an AGV system, after moving the AGV to the charging station, the power receiving coil mounted on the AGV is electromagnetically coupled to the power transmitting coil of the charging station to perform contactless charging in a contactless charging system. Before the charging, an optimization process of the operating frequency including frequency search according to the present embodiment is executed.

[0017] FIG. 5 is a graph showing the characteristics of the charging current and the equivalent load resistance with respect to the charging voltage when the load is a rechargeable battery, and FIG. 6 is a graph showing an example of a charging profile when charging the rechargeable battery. Further, FIG. 7 is a graph showing the frequency characteristics of the input-output gain of the resonance tank used in the contactless power supply system. In FIG. 6, the CC charging region is a constant current charging region, and the CV charging region is a constant voltage charging region.

[0018] As is clear from FIG. 5, the load RL varies depending on the remaining amount of the rechargeable battery. As a result, as shown in FIG. 7, the output voltage and the output current, which are the output characteristics of the circuit, vary. Therefore, for example, as shown in FIG. 6, control for satisfying the charging profile of the rechargeable battery is required.

[0019] FIG. 8 is a graph showing the frequency characteristics of the phase θ of the input impedance Zin for explaining the method of frequency search by the frequency control and drive unit 17 in FIG. 1. FIG. 9A is a diagram showing the input current waveform in the L property region in FIG. 8, FIG. 9B is a diagram showing the input current waveform at the resonance frequency in FIG. 8, and FIG. 9C is a diagram showing the input current waveform in the C property region in FIG. 8.

[0020] In this embodiment, as shown in FIGS. 8 to 9C, by utilizing the fact that almost no negative current flows at the resonance frequency where the input power factor is 1 within the operating frequency range of the inverter circuit 12, the operating frequency is set to the optimal resonance frequency by determining whether the input current is a negative current or a value in its vicinity and performing a frequency search. Note that in order to cause the inverter circuit 12 to perform zero voltage switching (ZVS) operation, it is preferable to set and operate the operating frequency of the inverter circuit 12 to be about 1 kHz lower on the low frequency side from the resonance frequency of the frequency searched composite resonance circuit.

[0021] The non-contact power supply system of FIG. 1 includes a power transmission device 100 and a power reception device 200. Here, the power transmission device 100 includes a power factor correction circuit (hereinafter referred to as a PFC circuit) 11, a capacitor C30, a power transmission control unit 16 including a PFC control unit that controls the operation of the PFC circuit 11, a current detector 18, a frequency control and drive unit 17, a power transmission LC resonance circuit 13, and a wireless communication circuit 15 having an antenna 15A.

[0022] Here, the current detector 18, the inverter circuit 12, and the frequency control and drive unit 17 constitute a drive control device 50 for the composite resonance circuit including the power transmission LC resonance circuit 13 and the power reception LC resonance circuit 14 to perform drive control. Here, as will be described later with reference to FIG. 16, the composite resonance circuit preferably has a resonance frequency at which the phase difference between the current flowing through the power transmission LC resonance circuit 13 and the voltage applied to the power transmission LC resonance circuit 13 becomes 0 and the power factor is 1 within the operating frequency range of the inverter circuit 12.

[0023] On the other hand, the power reception device 200 includes a power reception LC resonance circuit 14, a rectifier circuit 22, a DC / DC converter 23, a load 24, a power reception control unit 20 that detects the voltage and current of the load 24 and controls the DC / DC converter 23, and a wireless communication circuit 25 having an antenna 25A.

[0024] Here, the power transmission device 100 and the power reception device 200 are located in the vicinity of each other for power supply such as charging. As a result, the power transmission LC resonance circuit 13 and the power reception LC resonance circuit 14 are electromagnetically coupled to form a transformer TR1, for example. Also, the wireless communication circuit 15 and the wireless communication circuit 25 perform wireless communication using antennas 15A and 25A respectively to transmit and receive necessary information data. Note that the PFC circuit 11 may be a cascade connection circuit of a rectifier circuit and a DC / DC converter, as will be described in detail later. The DC / DC converter converts the input DC voltage into a predetermined DC voltage. In the present embodiment, the power reception control unit 20 determines the completion of charging and transmits the information to the power transmission control unit 16 via the wireless communication circuits 25 and 15.

[0025] In the power transmission device 100 of FIG. 1, the PFC circuit 11 converts the input voltage Vin, which is an AC voltage from an AC power source 30 such as a commercial AC power source, into a DC voltage and performs a power factor improvement process on the input voltage using a predetermined power factor improvement method under the control of the PFC control unit in the power transmission control unit 16, and outputs the output voltage to the inverter circuit 12 via the capacitor C30 and the current detector 18. The current detector 18 detects the input current Iin and outputs an input current signal SIin having a level corresponding to (e.g., proportional to) the input current Iin to the frequency control and drive unit 17. After a frequency search process for setting the resonance frequency based on the input current signal SIin and the operating frequency is executed in the preprocessing by the frequency control and drive unit 17, the inverter circuit 12 switches the input DC voltage based on, for example, a PWM gate signal from the frequency control and drive unit 17 to convert it into a predetermined AC voltage and outputs it to the rectifier circuit 22 via the power transmission LC resonance circuit 13 and the power reception LC resonance circuit 14.

[0026] Here, the PFC control unit of the power transmission control unit 16 receives load information such as the output voltage and output current to the load 24 from the power reception control unit 20 via the wireless communication circuits 25 and 15, and based on the load information, controls the PFC circuit 11 to perform the power factor improvement process. The power transmission LC resonance circuit 13 is an LC resonance circuit composed of an inductor L1 and a capacitor C1, as illustrated in, for example, FIG. 24A. It resonates at a predetermined resonance frequency fr based on the input voltage and generates AC power including an AC voltage having the resonance frequency fr, and transmits the AC power to the power reception LC resonance circuit 14 coupled to the power transmission LC resonance circuit 13.

[0027] In the power reception device 200 of FIG. 1, the power reception LC resonance circuit 14 is an LC resonance circuit composed of an inductor L2 and a capacitor C2, as illustrated in, for example, FIG. 24A. It receives the AC power from the power transmission LC resonance circuit 13 and outputs the AC voltage of the AC power to the rectifier circuit 22. The rectifier circuit 22 rectifies the input AC voltage into a DC voltage and outputs it to the load 24. The power reception control unit 20 detects the output voltage and output current to the load 24, and transmits information including those pieces of information and the charge completion determination information to the power transmission control unit 16 via the wireless communication circuits 25 and 15.

[0028] Note that the rectifier circuit 22 may be, for example, a rectifier circuit such as a half-wave rectifier circuit, a full-wave rectifier circuit, a full-bridge rectifier circuit, a half-active rectifier circuit, a voltage-doubling rectifier circuit, or a current-doubling rectifier circuit, as will be described in detail later. Also, the rectifier circuit 22 may rectify the input AC power into DC power.

[0029] FIG. 2 is a block diagram showing a detailed configuration example of the frequency control and drive unit 17 of FIG. 1.

[0030] In FIG. 2, the frequency control and drive unit 17 includes a negative current detection circuit 40, a switching detection and determination circuit 47, a switching frequency control circuit 48, and a drive signal generation circuit 49. Here, the negative current detection circuit 40 includes a signal amplifier 41, a comparator 42, a delay circuit 43, a one-shot pulse generator (hereinafter referred to as OPG) 44, an AND gate 45, and an OPG 46. The switching detection and determination circuit 47 includes a SWDS generator 47A that generates a SWDS signal, which is a switching detection signal having a predetermined pulse width.

[0031] The input current signal SIin from the current detector 18 is input to the inverting input terminal of the comparator 42 via the signal amplifier 41. A zero voltage is input to the inverting input terminal of the comparator 42. The comparator 42 compares the input current signal SIin with the zero voltage, generates a detection signal S42 indicating whether a negative current is generated, and outputs it to the AND gate 45. Here, the detection signal S42 becomes high level when a negative current is generated, while it becomes low level when no negative current is generated. The gate signal Sgate with a predetermined width from the power transmission control unit 16 is input to the OPG 44 via the delay circuit 43 that delays for a time corresponding to the delay time by the other circuit in order to match the negative current detection timing in the AND gate 45. The OPG 44 generates a gate width signal S44, which is a pulse with a predetermined width, in response to the rising edge of the input signal, and outputs it to the AND gate 45. The AND gate 45 calculates the logical product of the two input signals, and outputs the calculated detection signal S45 to the OPG 46. The OPG 46 generates a detection signal S46, which is a pulse with a predetermined width, in response to the rising edge of the input detection signal S45, and outputs it to the switching detection and determination circuit 47.

[0032] The switching detection and determination circuit 47 determines that the operating frequency of the inverter circuit 12 is set to the resonance frequency when both the input detection signal S46 and the SWDS signal are at the low level, and outputs a determination signal to the switching frequency control circuit 48. The switching frequency control circuit 48 executes a frequency search process described later and outputs a signal indicating the switching frequency to be set to the drive signal generation circuit 49. In response to this, the drive signal generation circuit 49 generates gate control signals S1 to S4 having the specified operating frequency and applies them to the gates of the MOS transistors of the inverter circuit 12.

[0033] FIG. 10 is a timing chart of each signal showing an example of the operation of the frequency control and drive unit 17 in FIG. 1. As is clear from FIG. 10, the frequency control and drive unit 17 can generate detection signals S42, S44, S45, and S46 based on the input current signal SIin and the gate signal Sgate.

[0034] FIG. 11 is a timing chart showing the operation in which the switching detection and determination circuit in FIG. 2 detects frequency switching by comparing the detection signal S46 with the SWDS signal. In the timing charts of FIGS. 11 to 15, for the sake of illustration, the level of the SWDS signal is slightly shifted upward to clarify the difference between each detection signal S45, S46 and the SWDS signal.

[0035] The switching frequency control circuit 48 controls the operating frequency of the inverter circuit 12 to increase or decrease until it is determined to be the resonance frequency. On the other hand, as shown in 111 of FIG. 11, the previous-stage switching detection and determination circuit 47 determines that it is the resonance frequency when both the detection signal S46 and the SWDS signal become low level. Here, in order to prevent false detection, the power transmission control unit 16 may be configured to count the predetermined number of pulses of both signals, for example.

[0036] Next, the pulse width (high level period) of the detection signal S46 output by the OPG46 will be described below.

[0037] Figure 12 is a timing chart showing the temporal relationship between the detection signal S45 and the SWDS signal for explaining the setting of the pulse width (high-level period) of the detection signal S46 generated by the OPG46 in FIG. 2. Further, FIG. 13 is a timing chart showing the temporal relationship between the detection signal S46 and the SWDS signal for explaining the setting of the high-level period of the detection signal S46 generated by the OPG (OPG) 46 in FIG. 2.

[0038] As is clear from 112 in FIG. 12, generally, since the pulse width of the detection signal S45 output by the AND gate 45 is short, by providing the OPG46 at the subsequent stage, as shown in 113 in FIG. 13, misdetection of the resonance frequency is prevented including the case where the detection timing is shifted.

[0039] Therefore, the pulse width of the detection signal S46 may be (1) equal to or greater than the pulse width of the detection signal S45 of the AND gate 45 and (2) equal to or less than the period Tfsw of the switching frequency fsw of the inverter circuit 12. Thereby, when the OPG46 outputs one pulse, it is possible to hold the high-level period up to the output terminal of the detection signal S45 of the next AND gate 45 at the maximum value.

[0040] Next, the low-level period of the SWDS signal will be described below.

[0041] Figure 14 is a timing chart showing the temporal relationship (NG case) between the detection signal S46 and the SWDS signal for explaining the setting of the low-level period of the SWDS signal in FIG. 2. Further, FIG. 15 is a timing chart showing the temporal relationship (OK case) between the detection signal S46 and the SWDS signal for explaining the setting of the low-level period of the SWDS signal in FIG. 2.

[0042] The low-level period of the SWDS signal is set to be equal to or shorter than the high-level period of the detection signal S45 of the AND gate 45. The reason is that, as shown in 114 of the NG case in FIG. 14, if the low-level period of the SWDS signal is longer than the detection signal S45, during the low-level period of one pulse of the SWDS signal, the switching detection and determination circuit 47 may detect both the low level and the high level of the binary signal of the detection signal S46. In this case, the operating frequency cannot be correctly searched. On the other hand, in the OK case of FIG. 15, it shows that during the low-level period of one pulse of the SWDS signal, the switching detection and determination circuit 47 can detect either the low level or the high level of the binary signal of the detection signal S46.

[0043] FIG. 16 is a graph showing the frequency characteristics of the phase difference between the input voltage and the input current (the phase difference between the voltage applied to the power transmission LC resonance circuit 13 and the current flowing through the power transmission LC resonance circuit 13) for the method of adjustment for ensuring the margin of achieving zero-voltage switching (ZVS) after detecting the resonance frequency in the frequency control and drive unit 17 of FIG. 2. As is clear from FIG. 16, the composite resonance circuit according to the present embodiment has a resonance frequency at which the phase difference between the current flowing through the power transmission LC resonance circuit 13 and the voltage applied to the power transmission LC resonance circuit 13 becomes 0 and the power factor is 1 within the operating frequency range of the inverter circuit 12.

[0044] In the present embodiment, as described above, after the switching detection and determination circuit 47 detects the switching, the switching frequency control circuit 48 searches and adjusts the operating frequency according to the magnitude of the load, and sets the operating frequency based on the resonance frequency which is the optimal operating frequency. Here, as shown in FIG. 16, in the case of a heavy load (frequency 83.5 kHz or less), it is preferable to control the operating frequency to decrease to such an extent that the transmission efficiency or the input power factor does not decrease significantly (for example, 0.5 to 1 kHz). On the other hand, in the case of a light load (frequency 83.5 kHz or more), it is preferable to control the operating frequency to increase to such an extent that the transmission efficiency or the input power factor does not decrease significantly (for example, 0.5 to 1 kHz).

[0045] Next, a specific example of the frequency search and power supply start processing executed by the non-contact power supply system and the frequency control and drive unit 17 in FIG. 1 will be described below.

[0046] FIG. 17 is a flowchart showing the frequency search and power supply start processing executed by the non-contact power supply system in FIG. 1.

[0047] In step S1 of FIG. 17, first, the power transmission control unit 16 performs wireless communication with the power reception control unit 20 via the wireless communication circuits 15 and 25, recognizes the power reception control unit 20, and starts communication control with the power reception control unit 20. Next, in step S2, the power transmission control unit 16 instructs the frequency control and drive unit 17 to start switching the inverter circuit 12 at a predetermined initial operating frequency. In step S3, the power transmission control unit 16 activates the PFC circuit 11 and instructs the PFC circuit 11 to output a predetermined voltage to the inverter circuit 12. Then, in step S4, the power transmission control unit 16 causes the frequency control and drive unit 17 to execute a frequency search process.

[0048] Next, in step S5, it is determined whether or not the search process for the resonance frequency has been completed. If YES, the process proceeds to step S6, while if NO, the process returns to step S4. In step S6, for the operation margin of zero voltage switching (ZVS), the operating frequency of the inverter circuit 12 is adjusted. Specifically, according to the characteristics of the composite resonance circuit, the operating frequency is adjusted to be lower or higher than the resonance frequency by a predetermined frequency change amount Δf (a positive value sufficiently smaller than the operating frequency). Further, in step S7, after executing the power supply start process, the frequency search and power supply start process are terminated.

[0049] First, as an example of the frequency search process, the frequency search process by the "sweeping method" will be described below.

[0050] FIG. 18A is a graph showing the frequency characteristics of the phase θ of the input impedance Zin, which shows a frequency search method by the sweep method. FIG. 18B is a waveform diagram of the input current at the resonance frequency of FIG. 18A.

[0051] As shown in FIG. 18A, the sweep method is a technique that periodically changes the operating frequency in one direction only once, for example, and searches for the operating frequency at which no negative current flows in the input current Iin (see FIG. 18B). Since the sweep method changes the operating frequency once in one direction, it can search for the load-independent point of the resonance frequency in a shorter time than the hill-climbing method described later, but it may not be able to search accurately depending on the resolution of the operating frequency.

[0052] FIG. 19 is a flowchart showing the frequency search process by the sweep method (when starting from the lower limit of the operating frequency; subroutine of FIG. 17) executed by the frequency control and drive unit 17 of FIG. 2.

[0053] In step S11 of FIG. 19, first, an input current signal SIin indicating the input current Iin is detected. In step S12, it is determined whether Iin ≧ Iinth. If YES, the process proceeds to step S13, while if NO, the process proceeds to step S14. Here, Iinth is the input current threshold for negative current determination, and is, for example, 0 or a value near 0. Next, in step S13, it is determined whether Iin ≧ Iinth continuously for a predetermined number n times using the SWDS signal. If YES, the process proceeds to step S15, while if NO, the process proceeds to step S14. In step S14, after increasing the operating frequency (switching frequency) fsw of the inverter circuit 12 by a predetermined frequency change amount Δf, the process returns to step S11. Further, in step S15, it is determined that the current operating frequency is the resonance frequency and the resonance frequency of the complex resonance circuit has been searched, and the frequency search process is terminated, and the process returns to the original main routine.

[0054] Figure 20 is a flowchart showing the frequency search process (when starting from the upper limit of the operating frequency; subroutine in Figure 17) by the sweep method executed by the frequency control and drive unit 17 in Figure 2. The frequency search process in Figure 20 differs from the frequency search process in Figure 19 in the following points. (1) Instead of step S14, step S14A is provided. In step S14A, the operating frequency (switching frequency) fsw of the inverter circuit 12 is decreased by a predetermined frequency change amount Δf.

[0055] As described above, by executing the frequency search process by the sweep method in Figure 19 or Figure 20, the resonance frequency of the composite resonance circuit can be searched.

[0056] Next, as an example of the frequency search process, the frequency search process by the "hill climbing method" will be described below.

[0057] Figure 21A is a graph showing the frequency characteristics of the phase θ of the input impedance Zin, indicating the frequency search method by the hill climbing method. Figure 21B is a waveform diagram of the input current at the resonance frequency in Figure 21A. In the hill climbing method, as shown by SS1 to SS5 in Figure 21A, the operating frequency is changed in one direction from a preset operating frequency. When a pattern of having a negative current, not having a negative current (being the resonance frequency, refer to Figure 21B), and having a negative current is detected in the input current Iin, it is determined that the resonance frequency has been passed, and the direction of the change in the operating frequency is reversed. And each time it is reversed, the operating frequency change amount Δf is decreased by a predetermined decrement value Δfd, and this is repeated to search for the resonance frequency. Therefore, in the hill climbing method, the accuracy of the frequency search can be improved by repeating the sweep method.

[0058] Figures 22A and 22B are flowcharts showing the frequency search process by the hill climbing method (when starting from the lower limit of the operating frequency; subroutine in Figure 17) executed by the frequency control and drive unit 17 in Figure 2.

[0059] In step S20 of FIG. 22A, first, after setting the initial frequency change amount Δf0 to the frequency change amount Δf, in step S21, an input current signal SIin indicating the input current Iin is detected. In step S22, it is determined whether Iin≧Iinth. When YES, the process proceeds to step S23, while when NO, the process proceeds to step S24. Here, Iinth is the input current threshold for negative current determination, for example, 0 or a value near 0 (a positive value or a negative value). In step S23, using the SWDS signal, it is determined whether Iin≧Iinth continuously for a predetermined n times. When YES, the process proceeds to step S26, while when NO, the process proceeds to step S24. In step S24, after increasing and setting the operating frequency fsw by the frequency change amount Δf, in step S25, it is determined whether the operating frequency fsw is the upper limit of the operating frequency. When YES, the process proceeds to step S26, while when NO, the process returns to step S21.

[0060] In step S26, after increasing and setting the operating frequency fsw by the frequency change amount Δf, in step S27, the frequency change amount Δf is decreased and set by the decrement value Δfd. In step S28, it is determined whether the frequency change amount Δf<Δfth (in view of the search accuracy in the hill climbing method, whether it is a point close to the extreme value). When YES, the process proceeds to step S36 of FIG. 22B, while when NO, the process proceeds to step S29. Here, Δfth is the threshold of the frequency change amount Δf and is set to a positive value sufficiently smaller than the initial frequency change amount Δf0.

[0061] In step S29, after decreasing and setting the operating frequency fsw by the frequency change amount Δf, in step S30, an input current signal SIin indicating the input current Iin is detected. In step S31, it is determined whether Iin≧Iinth. Here, when YES, the process proceeds to step S32, while when NO, the process proceeds to step S33.

[0062] In step S32, it is determined whether Iin ≥ Iinth continuously for a predetermined number n of times using the SWDS signal. When the result is YES, the process proceeds to step S35; when the result is NO, the process proceeds to step S33. In step S33, after setting the operating frequency fsw to be decreased by the frequency change amount Δf, in step S34, it is determined whether the operating frequency fsw is at the lower limit of the operating frequency. When the result is YES, the process proceeds to step S35; when the result is NO, the process returns to step S30. In step S35, after setting the frequency change amount Δf to be decreased by the decrement value Δfd, the process returns to step S24.

[0063] In step S36 of FIG. 22B, after setting the operating frequency fsw to be decreased by the frequency change amount Δf, in step S37, an input current signal SIin indicating the input current Iin is detected. In step S38, it is determined whether Iin ≥ Iinth. Here, when the result is YES, the process proceeds to step S40; when the result is NO, the process returns to step S36. Next, in step S39, it is determined whether Iin ≥ Iinth continuously for a predetermined number n of times using the SWDS signal. When the result is YES, the process proceeds to step S40; when the result is NO, the process returns to step S36. In step S40, it is determined that the current operating frequency is the resonance frequency of the complex resonance circuit and the resonance frequency has been searched, and the frequency search process is terminated, and the process returns to the original main routine.

[0064] As described above, according to the frequency search processes of FIGS. 22A and 22B, the resonance frequency of the complex resonance circuit can be searched while changing the operating frequency using the hill - climbing method.

[0065] FIGS. 23A and 23B are flowcharts showing the frequency search process (when starting from the upper limit of the operating frequency; sub - routine of FIG. 17) by the hill - climbing method executed by the frequency control and drive unit 17 of FIG. 2. FIGS. 23A and 23 B The frequency search processes of FIGS. 23A and 23B are different from the frequency search processes of FIGS. 22A and 22B in the following points. (1) Instead of steps S24 and S26 respectively, steps S24A and S26A are provided. In steps S24A and S26A, the operating frequency fsw is set by decreasing it by the frequency change amount Δf. (2) Instead of steps S29, S33, and S36 respectively, steps S29A, S33A, and S36A are provided. In steps S29A, S33A, and S36A, the operating frequency fsw is set by increasing it by the frequency change amount Δf.

[0066] As described above, according to the frequency search process of FIGS. 23A and 23B, the resonance frequency of the composite resonance circuit can be searched while changing the operating frequency using the hill climbing method.

[0067] As described above, according to the drive control device 50 of the composite resonance circuit according to the present embodiment, even if the coupling degree k between the inductors L1 and L2 and the inductor L1 or the like change, the inverter circuit 12 can be operated at the resonance frequency with a power factor of 1. Thereby, zero voltage switching (ZVS) in the composite resonance circuit can be realized. Therefore, according to the variation in the positional relationship between the power transmission and reception coils of the composite resonance circuit, compared with the prior art, it is possible to control to the optimal operating frequency in a short time.

[0068] Also, by configuring a non-contact power supply system using the drive control device 50 of the composite resonance circuit, the DC / DC converter 23 of the power receiving device 200 for maximizing the transmission efficiency can be deleted. In FIG. 1, for the sake of a modification example, the DC / DC converter 23 is inserted, but in the present embodiment, as will be described in detail later, it may be deleted. Further, in order to maximize the efficiency in the power transmission device 100, it is not necessary to perform impedance matching by the DC / DC converter 23 in the power receiving device 200.

[0069] In the above embodiments, as a method for searching the resonance frequency of the composite resonance circuit, the sweep method or the hill climbing method is used, but the present invention is not limited to this, and various other known extreme value search methods may be used.

[0070] (Modification Example of Non-Contact Power Supply System) Fig. 1 shows a configuration example of the non-contact power supply system according to the embodiment. The present invention is not limited to this, and it may be configured as follows.

[0071] [Table 1] ―――――――――――――――――――――――――――――――― Case 1 Case 2 Case 3 Case 4 ―――――――――――――――――――――――――――――――― PFC circuit Yes / No (Note 1) No (Note 1) Yes DC / DC converter Yes Yes No (Note 2) No (Note 2) Wireless communication circuit Yes / No Yes / No Yes / No Yes / No ――――――――――――――――――――――――――――――――

[0072] (Note 1) When the PFC circuit 11 is absent, the PFC circuit 11 is replaced with a rectifier circuit. At this time, the power transmission control unit 16 does not include a PFC control unit. (Note 2) The power reception control unit 20 is unnecessary when the DC / DC converter 23 is absent and the rectifier circuit 22 is composed of only diodes and the PFC circuit 11 is absent. At this time, the wireless communication circuits 15 and 25 are unnecessary.

[0073] (Embodiment and Modification Example of Composite Resonance Circuit) Hereinafter, a configuration example of the composite resonance circuit used in the embodiment and the modification example is shown. Note that the following modification example is just an example, and calibration may be performed using various other LC resonance circuits.

[0074] Fig. 24A is a circuit diagram showing a configuration example of the composite resonance circuit according to the embodiment. In Fig. 24A, the composite resonance circuit includes a power transmission LC resonance circuit 13 including a series circuit of an inductor L1 and a capacitor C1, and a power reception LC resonance circuit 14 including a series circuit of an inductor L2 and a capacitor C2.

[0075] FIG. 24B is a circuit diagram showing a configuration example of a composite resonance circuit according to Modification Example 1. In FIG. 24B, the composite resonance circuit includes a power transmission LC resonance circuit 13 including a series circuit of an inductor L1 and a capacitor C1, and a power reception LC resonance circuit 14B including a parallel circuit of an inductor L2 and a capacitor C20.

[0076] FIG. 24C is a circuit diagram showing a configuration example of a composite resonance circuit according to Modification Example 2. In FIG. 24C, the composite resonance circuit includes a power transmission LC resonance circuit 13C including a parallel circuit of an inductor L1 and a capacitor C10, and a power reception LC resonance circuit 14B including a parallel circuit of an inductor L2 and a capacitor C20.

[0077] FIG. 24D is a circuit diagram showing a configuration example of a composite resonance circuit according to Modification Example 3. In FIG. 24D, the composite resonance circuit includes a power transmission LC resonance circuit 13C including a parallel circuit of an inductor L1 and a capacitor C10, and a power reception LC resonance circuit 14 including a series circuit of an inductor L2 and a capacitor C2.

[0078] FIG. 24E is a circuit diagram showing a configuration example of a composite resonance circuit according to Modification Example 4. In FIG. 24E, the composite resonance circuit includes a power transmission LC resonance circuit 13 including a series circuit of an inductor L1 and a capacitor C1, and a power reception LC resonance circuit 14E including a series circuit of an inductor L2 and capacitors C2 and C20.

[0079] FIG. 24F is a circuit diagram showing a configuration example of a composite resonance circuit according to Modification Example 5. In FIG. 24F, the composite resonance circuit includes a power transmission LC resonance circuit 13C including a parallel circuit of an inductor L1 and a capacitor C10, and a power reception LC resonance circuit 14E including a series circuit of an inductor L2 and capacitors C2 and C20.

[0080] FIG. 24G is a circuit diagram showing a configuration example of a composite resonance circuit according to Modification Example 6. In FIG. 24G, the composite resonance circuit includes a power transmission LC resonance circuit 13G including a series circuit of an inductor L1 and capacitors C1 and C10, and a power reception LC resonance circuit 14 including a series circuit of an inductor L2 and a capacitor C2.

[0081] FIG. 24H is a circuit diagram showing a configuration example of a composite resonance circuit according to Modification Example 7. In FIG. 24H, the composite resonance circuit includes a power transmission LC resonance circuit 13G including a series circuit of an inductor L1 and capacitors C1 and C10, and a power reception LC resonance circuit 14B including a parallel circuit of an inductor L2 and a capacitor C20.

[0082] FIG. 24I is a circuit diagram showing a configuration example of a composite resonance circuit according to Modification Example 8. In FIG. 24I, the composite resonance circuit includes a power transmission LC resonance circuit 13G including a series circuit of an inductor L1 and capacitors C1 and C10, and a power reception LC resonance circuit 14E including a series circuit of an inductor L2 and capacitors C2 and C20.

[0083] FIG. 24J is a circuit diagram showing a configuration example of a composite resonance circuit according to Modification Example 9. In FIG. 24J, the composite resonance circuit includes a power transmission LC resonance circuit 13J further including an inductor L10 in a series circuit of an inductor L1 and capacitors C1 and C10, and a power reception LC resonance circuit 14 including a series circuit of an inductor L2 and a capacitor C2.

[0084] FIG. 24K is a circuit diagram showing a configuration example of a composite resonance circuit according to Modification Example 10. In FIG. 24K, the composite resonance circuit includes a power transmission LC resonance circuit 13J further including an inductor L10 in a series circuit of an inductor L1 and capacitors C1 and C10, and a power reception LC resonance circuit 14B including a parallel circuit of an inductor L2 and a capacitor C20.

[0085] FIG. 24L is a circuit diagram showing a configuration example of a composite resonance circuit according to Modification Example 11. In FIG. 24L, the composite resonance circuit includes a power transmission LC resonance circuit 13 including a series circuit of an inductor L1 and a capacitor C1, and a power reception LC resonance circuit 14L further including an inductor L20 in a series circuit of an inductor L2 and capacitors C2 and C20.

[0086] FIG. 24M is a circuit diagram showing a configuration example of a composite resonance circuit according to Modification Example 12. In FIG. 24M, the composite resonance circuit includes a power transmission LC resonance circuit 13C including a parallel circuit of an inductor L1 and a capacitor C10, and a power reception LC resonance circuit 14L including an inductor L20 in series with a series circuit of an inductor L2 and capacitors C2 and C20.

[0087] FIG. 24N is a circuit diagram showing a configuration example of a composite resonance circuit according to Modification Example 13. In FIG. 24N, the composite resonance circuit includes a power transmission LC resonance circuit 13J including an inductor L10 in series with a series circuit of an inductor L1 and capacitors C1 and C10, and a power reception LC resonance circuit 14L including an inductor L20 in series with a series circuit of an inductor L2 and capacitors C2 and C20.

[0088] (Modification Examples of Rectifier Circuits) Hereinafter, configuration examples of rectifier circuits according to modification examples are shown. Note that the following modification examples are merely examples, and calibration may be performed using various other rectifier circuits.

[0089] FIG. 25A is a circuit diagram showing a configuration example of a rectifier circuit according to Modification Example 14. The rectifier circuit of FIG. 25A includes a rectifying diode D1 and a smoothing electrolytic capacitor C5 to form a half-wave rectifier circuit.

[0090] FIG. 25B is a circuit diagram showing a configuration example of a rectifier circuit according to Modification Example 15. The rectifier circuit of FIG. 25B includes rectifying diodes D1 and D2 and a smoothing electrolytic capacitor C5 to form a full-wave rectifier circuit.

[0091] FIG. 25C is a circuit diagram showing a configuration example of a rectifier circuit according to Modification Example 16. The rectifier circuit of FIG. 25C includes rectifying diodes D1, D2, D3, and D4 to form a full-bridge rectifier circuit.

[0092] FIG. 25D is a circuit diagram showing a configuration example of a rectifier circuit according to Modification 17. The rectifier circuit of FIG. 25D includes rectifier diodes D1, D2, MOS transistors Q1, Q2, and a smoothing electrolytic capacitor C5 to form a half-active rectifier circuit. Here, Cp1 and Cp2 are parasitic capacitors, and Dp1 and Dp2 are parasitic diodes. In this half-active rectifier circuit, the output power can be adjusted by having a short-circuit mode as is well known. Note that the configurations of the upper and lower arms may be reversed.

[0093] FIG. 25E is a circuit diagram showing a configuration example of a rectifier circuit according to Modification 18. The rectifier circuit of FIG. 25E includes MOS transistors Q1, Q2, and a smoothing electrolytic capacitor C5 to form a voltage-doubling rectifier circuit. Here, Cp1 and Cp2 are parasitic capacitors, and Dp1 and Dp2 are parasitic diodes. Note that the MOS transistors Q1 and Q2 may be replaced with diodes.

[0094] In the above embodiments and modifications, a composite resonance circuit including two LC resonance circuits electromagnetically coupled to each other is used, but the present invention is not limited to this, and a plurality of LC resonance circuits electromagnetically coupled to each other may be used.

Industrial Applicability

[0095] As described in detail above, according to the drive control device 50 of the composite resonance circuit according to the present invention, it is possible to control to the optimal operating frequency in a shorter time compared to the prior art in response to fluctuations in the positional relationship between the power transmission and reception coils of the composite resonance circuit.

[0096] Also, by configuring a non-contact power supply system using the drive control device 50 of the composite resonance circuit, the DC / DC converter 23 of the power receiving device 200 for maximizing the transmission efficiency can be deleted. Furthermore, in order to maximize the transmission efficiency on the power transmission device 100 side, it is not necessary to perform impedance matching by the DC / DC converter 23 in the power receiving device 200.

Explanation of Reference Numerals

[0097] 11 Power factor improvement circuit (PFC circuit) 12 Inverter circuit 13, 13C~13J Power transmission LC resonance circuit (LC resonance circuit) 14, 14B~14L Power reception LC resonance circuit (LC resonance circuit) 15 Wireless communication circuit 15A Antenna 16 Power transmission control unit 17 Frequency control and drive unit 18 Current detector 20 Power reception control unit 22 Rectifier circuit 23 DC / DC converter 24 Load 25 Wireless communication circuit 25A Antenna 30 AC power supply 40 Negative current detection circuit 41 Signal amplifier 42 Comparator 43 Delay circuit 44 One-shot pulse generator (OPG) 45 AND gate 46 One-shot pulse generator (OPG) 47 Switching detection and determination circuit 47A SWDS generator 48 Switching frequency control circuit 49 Drive signal generation circuit 50 Drive control device for composite resonance circuit 100 Power transmission device 200 Power reception device C1~C30 Capacitor Cp1~Cp2 Parasitic capacitor D1~D4 Rectifier diode Dp1~Dp2 Parasitic diode L1~L20 Inductor Q1~Q5 MOS transistor RL Load resistor TR1 Transformer

Claims

1. A drive control device for a composite resonance circuit configured by a plurality of LC resonance circuits including the inductance L of a power transmission and reception coil magnetically coupled to each other, the drive control device comprising: an inverter circuit that converts the input DC power into AC power and drives the composite resonance circuit by switching the input DC power at a predetermined operating frequency; an input current detector that detects the input current of the inverter circuit; a frequency control and drive unit, wherein the composite resonance circuit includes a power transmission LC resonance circuit that transmits AC power from the inverter circuit, and a power reception LC resonance circuit that is magnetically coupled to the inductance L of the power transmission LC resonance circuit and receives AC power from the power transmission LC resonance circuit, wherein the composite resonance circuit has a resonance frequency within the operating frequency range of the inverter circuit at which the phase difference between the current flowing through the power transmission LC resonance circuit and the voltage applied to the power transmission LC resonance circuit becomes 0 and the power factor is 1, wherein the frequency control and drive unit uses a predetermined extreme value search method to generate a drive signal for the inverter circuit while changing the operating frequency to drive the inverter circuit, and based on whether the detected input current is a negative current or a value in the vicinity thereof, utilizes the fact that no negative current flows at the resonance frequency, which is the point where the input power factor is 1, within the operating frequency range of the inverter circuit, to search for the resonance frequency of the composite resonance circuit and sets the operating frequency based on the searched resonance frequency; A drive control device for a composite resonance circuit comprising the above.

2. The frequency control and drive unit causes the inverter circuit to perform zero voltage switching (ZVS) operation by moving the operating frequency from the searched resonance frequency by a predetermined frequency to the lower frequency side or the higher frequency side based on the resonance characteristics of the composite resonance circuit. The drive control device for a composite resonance circuit according to Claim 1.

3. The extreme value search method is a sweep method or a hill climbing method. The drive control device for a composite resonance circuit according to Claim 1 or 2.

4. A non-contact power supply system comprising the drive control device for a composite resonance circuit according to any one of Claims 1 to 3, wherein the non-contact power supply system includes a power transmission device and a power reception device, wherein the power transmission device includes the power transmission LC resonance circuit, the input current detector, the inverter circuit, and the frequency control and drive unit, wherein the power reception device includes the power reception LC resonance circuit. Non-contact power supply system.

5. The power transmission device further is provided in front of the input current detector and includes a power factor improvement circuit that improves the power factor by shaping the waveform of the input current based on a predetermined AC voltage. The non-contact power supply system according to claim 4.

6. The power transmission device further is provided in front of the input current detector and includes a first rectifier circuit that rectifies the input AC power into a predetermined DC voltage, and a first DC / DC converter that converts the DC voltage from the first rectifier circuit into a predetermined DC voltage. The non-contact power supply system according to claim 4.

7. The power receiving device further includes a second rectifier circuit that converts the AC power from the power receiving LC resonance circuit into DC power. The non-contact power supply system according to any one of claims 4 to 6.

8. The power receiving device further includes a second DC / DC converter that converts the DC voltage from the second rectifier circuit into a predetermined DC voltage. The non-contact power supply system according to claim 7.

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