Resonant power conversion circuit and contactless power supply system

Abstract

To provide a resonance type power conversion circuit and the like that mitigate calculation costs greatly with a simple configuration.SOLUTION: A resonance type power conversion circuit comprises: a resonance circuit that includes a first LC resonance circuit and a switching element and outputs output voltage or output current to a load; a detection circuit for detecting output information that is the output voltage or output current; a calculation control unit that, on the basis of the detected output information, searches for a maximum point in the output information's characteristic with respect to operation frequencies and determines an operation frequency corresponding to the maximum point obtained by the search; and a signal generation unit that generates a drive control signal having the determined operation frequency and performs frequency control on the switching element on the basis of the drive control signal. The resonance circuit has the output information's characteristic with respect to operation frequencies that has a load independent point that corresponds to the maximum point and is independent of the load, feeds back the drive control signal including the output information to the switching element, and is driven at the load independent point by frequency control using the drive control signal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a resonant power conversion circuit and a contactless power supply system using the resonant power conversion circuit. [Background technology]

[0002] Conventionally, mobile vehicles such as automatic guided vehicles (AGVs) are equipped with rechargeable batteries such as lithium-ion batteries. To charge these batteries, the AGV is moved to a charging station, and then 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.

[0003] In the contactless power transfer system of Fig. 12, which is an example of the contactless charging system, an AC power supply 31 of voltage v11 is connected to a series resonant circuit of an inductor L11 of a primary coil of a transformer TR11, a resistor R11, and a capacitor C11. A load resistor RL is connected to a series resonant circuit of an inductor L12 of a secondary coil of the transformer TR11, a resistor R12, and a capacitor C12. The inductors L11 and L12 of the transformer TR11 are electromagnetically coupled to each other with a coupling factor k. When a current i11 flows from the AC power supply 31, a voltage v12 is applied to the load resistor RL, causing a current i12 to flow. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Mohammad Mahdi Ahmadi, et al., "A Self-Tuned Class-E Power Oscillator," IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 34, NO. 5, MAY 2019. Summary of the Invention [Problem to be solved by the invention]

[0005] However, the contactless power supply system of FIG. 12, which is an example of the contactless charging system, has the following two problems as shown in FIG.

[0006] (Issue 1) When the relative positions of the transmitting coil and receiving coil change, the inductance changes, which in turn changes the resonant frequency fr, causing the switching frequencies fsw and fr to mismatch, resulting in adverse effects such as a decrease in efficiency. This requires a mechanism to control the drive circuit of the switching element in order to match the switching frequency to the resonant frequency. Furthermore, changes in inductance change the output characteristics of the charging circuit, such as the output voltage and output current, making the circuit design and control required to meet the charging profile of the rechargeable battery more complex.

[0007] (Issue 2) The load fluctuates depending on the remaining charge of the rechargeable battery, which in turn fluctuates the output characteristics of the charging circuit, such as the output voltage and output current. This makes the circuit design and control required to meet the charging profile of the rechargeable battery complex.

[0008] Therefore, in order to solve the above two problems, it becomes necessary to add complex control and mechanisms to accompany the control, which leads to problems such as a decrease in power conversion efficiency and an increase in volume, weight, and cost.

[0009] To solve these two problems, the class E resonant inverter circuit shown in Fig. 14 has been proposed in Non-Patent Document 1. However, to solve Problem 2, the phase needs to be inverted by 180 degrees to achieve load independence, and phase control is required to invert the phase. However, there is a problem in that the calculation cost of the calculation control unit that performs this phase control becomes very high.

[0010] The object of the present invention is to provide a resonant power conversion circuit that can solve the above problems and the two problems mentioned above, and that can significantly reduce the calculation cost compared to the conventional technology, and a contactless power supply system that uses the resonant power conversion circuit. [Means for solving the problem]

[0011] A resonant power conversion circuit according to one aspect of the present invention comprises: a resonant circuit including a first LC resonant circuit and a switching element, and outputting an output voltage or an output current to a load; a detection circuit for detecting output information, which is the output voltage or the output current; a calculation control unit that searches for a maximum point or a desired voltage in the characteristics of the output information with respect to the operating frequency using a predetermined maximum point search method based on the detected output information, and determines an operating frequency corresponding to the searched maximum point or the desired voltage; a signal generating unit that generates a drive control signal having the determined operating frequency and controls the frequency of the switching element based on the drive control signal; the resonant circuit has a characteristic of output information with respect to the operating frequency, the characteristic having a load-independent point that does not depend on the load and corresponds to the maximum point or the desired voltage; The resonant circuit feeds back a drive control signal including the output information to the switching element, and drives the switching element at the load-independent point by frequency control using the drive control signal. [Effects of the Invention]

[0012] Therefore, according to the present invention, by being configured as described above, it is possible to provide a resonant power conversion circuit that can solve the above two problems and can significantly reduce the calculation cost compared to the prior art, and a contactless power supply system that uses the resonant power conversion circuit. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a circuit diagram illustrating a configuration example of a resonant power conversion circuit according to an embodiment. [Figure 2] 2 is a waveform diagram showing the relationship between a gate voltage signal Vf applied to the MOS transistor Q1 of FIG. 1 and an output voltage V0, and the phase difference θ therebetween. [Figure 3A]2 is a graph showing the results of a simulation of the resonant power conversion circuit of FIG. 1, illustrating the output voltage Vo and the phase difference θ versus the operating frequency f when the parameter L0 / L0rate=0.9. [Figure 3B] 2 is a graph showing the results of a simulation of the resonant power conversion circuit of FIG. 1, illustrating the output voltage Vo and the phase difference θ versus the operating frequency f when the parameter L0 / L0rate=1.0. [Figure 3C] 2 is a graph showing the results of a simulation of the resonant power conversion circuit of FIG. 1, illustrating the output voltage Vo and the phase difference θ versus the operating frequency f when the parameter L0 / L0rate=1.1. [Figure 4] 3C is a graph showing an example of control when frequency control is performed by the hill-climbing method in the resonant power conversion circuit of FIG. 1 in the graph of FIG. 3B. [Figure 5] 2 is a flowchart showing an operating frequency determination process executed by the control circuit 10 of FIG. [Figure 6] 6 is a graph showing an example of control in a graph of output voltage Vo versus operating frequency f when the operating frequency is determined by the operating frequency determination process of FIG. 5; [Figure 7] 2 is a flowchart showing a detailed operating frequency determination process executed by the control circuit 10 of FIG. [Figure 8] FIG. 8 is a diagram showing a graph for setting a progress width df in the progress width determination process P3 in the operating frequency determination process of FIG. 7. [Figure 9] 2 is a block diagram showing an example of the configuration of a contactless power supply system when the resonant power conversion circuit of FIG. 1 is applied to the contactless power supply system. FIG. [Figure 10A] 10 is a circuit diagram showing a configuration example of the LC resonant circuit 13 of FIG. 9. [Figure 10B] 10 is a circuit diagram showing a configuration example of an LC resonant circuit 13A according to a first modification. FIG. [Figure 10C] 10 is a circuit diagram showing a configuration example of an LC resonant circuit 13B according to a second modification. FIG. [Figure 10D] 10 is a circuit diagram showing a configuration example of an LC resonant circuit 13C according to a third modification. FIG. [Figure 10E] FIG. 11 is a circuit diagram showing a configuration example of an LC resonant circuit 13D according to a fourth modification. [Figure 10F] 13 is a circuit diagram showing a configuration example of an LC resonant circuit 13E according to a fifth modification. FIG. [Figure 11A] 10 is a circuit diagram showing a configuration example of the LC resonant circuit 14 of FIG. 9. [Figure 11B] 13 is a circuit diagram showing a configuration example of an LC resonant circuit 14A according to a sixth modification. FIG. [Figure 11C] 13 is a circuit diagram showing a configuration example of an LC resonant circuit 14B according to a seventh modification. FIG. [Figure 11D] 13 is a circuit diagram showing a configuration example of an LC resonant circuit 14C according to Modification 8. FIG. [Figure 11E] 13 is a circuit diagram showing a configuration example of an LC resonant circuit 14D according to a ninth modification. FIG. [Figure 11F] 13 is a circuit diagram showing a configuration example of an LC resonant circuit 14E according to a tenth modification. FIG. [Figure 12] FIG. 1 is a circuit diagram showing an example of a circuit of a contactless power supply system using a resonant power conversion circuit according to a conventional technique. [Figure 13] 13 is a graph showing an example of operation of the resonant power conversion circuit of FIG. 12. [Figure 14] FIG. 1 is a circuit diagram showing an example of a conventional class E resonant inverter circuit. [Figure 15] 15 is a waveform diagram showing an example of the operation of the class E resonant inverter circuit of FIG. 14. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments and modifications of the present invention will be described with reference to the drawings, in which the same or similar components are designated by the same reference numerals.

[0015] (Inventor's Knowledge) FIG. 14 is a circuit diagram showing an example of a conventional class E resonant inverter circuit, and FIG. 15 is a waveform diagram showing an example of the operation of the class E resonant inverter circuit of FIG.

[0016] In FIG. 14, the class E resonant inverter circuit 90 is configured with a DC bias circuit 31A consisting of voltage dividing resistors Rd1 and Rd2, a feedback inductor LF, and voltage dividing capacitors Cn1 and Cn2, a MOS field effect transistor (hereinafter referred to as a MOS transistor) Q1, inductors L21 and L22, capacitors C21 and C22, and a load resistor RL.

[0017] In the class E resonant inverter circuit 90 of Fig. 14, the power supply voltage VDD is applied to the drain of the MOS transistor Q21 via inductor L21, and a DC bias voltage divided by voltage-dividing resistors Rd1 and Rd2 is applied to the gate of the MOS transistor Q21. The output voltage Vo across the load resistor Ro is divided by voltage-dividing capacitors Cn1 and Cn2, and then applied as a gate signal to the gate of the MOS transistor Q1 via feedback inductor LF. The output source voltage Vs generated by the MOS transistor Q1 is output as the output voltage Vo to the load resistor RL via capacitors C1 and C2 and inductor L2. Here, the gate voltage signal Vf applied to the gate of the MOS transistor Q1 is a voltage that is phase-shifted by 140 degrees with respect to the output voltage Vo, as shown in Fig. 15.

[0018] In the class E resonant inverter circuit 90 according to Non-Patent Document 1 configured as described above, the phase of the gate voltage signal Vf can only be shifted by 140 degrees relative to the waveform of the output voltage Vo, and therefore Problem 2 cannot be solved. Therefore, there is a problem that control is required to deal with the inductance and load fluctuation of the resonant circuit.

[0019] Therefore, in the embodiments according to the present invention, a resonant power conversion circuit that can solve both problems 1 and 2 and a contactless power supply system that uses the resonant power conversion circuit will be described below.

[0020] (Embodiment) Fig. 1 is a circuit diagram showing an example of the configuration of a resonant power conversion circuit according to an embodiment. In Fig. 1, the resonant power conversion circuit according to the embodiment is configured to include a resonant circuit 1, a detection circuit 2, and a control circuit 10. Specifically, the resonant power conversion circuit is a resonant inverter circuit. The control circuit 10 includes an arithmetic and control unit 3 and a signal generating unit 4. The resonant circuit 1 includes a DC power supply 5, a smoothing inductor Lf, a MOS transistor Q1 serving as a switching element, capacitors Cs and C0, and an inductor L0, forming an LC resonant circuit.

[0021] 1, an input voltage Vin from a DC power supply 5 is applied via a smoothing inductor Lf between the drain and source of a MOS transistor Q1 operating as a switching element and to a resonant capacitor Cs. A gate voltage signal Vf (drive control signal) for driving and controlling the switching element Q1 is applied to the gate of the MOS transistor Q1 from a signal generating unit 4, and the MOS transistor Q1 is switched on or off based on the gate voltage signal Vf.

[0022] In the resonant circuit 1, the resonant capacitors Cs and C0 correspond to the power transmission side resonant capacitor in the contactless power transfer system, and the resonant inductor L0 corresponds to the self-inductance of the transformer (power transmission coil) in the contactless power transfer system.

[0023] The detection circuit 2 detects the voltage of the load resistor RL, converts it to a DC voltage, and outputs it to the calculation control unit 3. In the detection circuit 2, the voltage of the load resistor RL is divided by voltage-dividing resistors R1 and R2, the divided voltage is rectified by a rectifier diode D1, and then smoothed by a smoothing capacitor Csm to obtain an output voltage Vo, which is output to the calculation control unit 3.

[0024] 5 or 7 based on the detected output voltage Vo, using a maximum value search method such as a hill-climbing method to search for the maximum value of the output voltage Vo in the characteristics of the output voltage Vo versus the operating frequency, and determines the operating frequency corresponding to the searched maximum value of the output voltage Vo and outputs it to the signal generating unit 4. The signal generating unit 4 generates a PWM (Pulse Width Modulation) signal having the input operating frequency and applies it to the gate of the MOS transistor Q1 as a gate voltage signal Vf, thereby controlling the frequency of the resonant circuit 1 including the MOS transistor Q1 and the LC resonant circuit.

[0025] Figure 2 is a waveform diagram showing the relationship between the gate voltage signal Vf applied to the MOS transistor Q1 in Figure 1 and the output voltage V0, and the phase difference θ between them. As is clear from Figure 2, when there is a phase difference θ between the gate voltage signal Vf and the output voltage V0, the output voltage Vo is far from its maximum value.

[0026] FIG. 3A shows the simulation results of the resonant power conversion circuit of FIG. 1, where the parameter L0 / L0 rate 3B is a graph showing the output voltage Vo and the phase difference θ with respect to the operating frequency f when the parameter L0 / L0 rate 3C is a graph showing the output voltage Vo and the phase difference θ with respect to the operating frequency f when the parameter L0 / L0 rate 3A and subsequent figures show graphs illustrating the output voltage Vo and the phase difference θ with respect to the operating frequency f when Lo = 1.1. rate is the reference element value (inductance value) of the resonant inductor L0, and RL rate is the reference element value (resistance value) of the load resistor RL.

[0027] 3A to 3C show the inductance ratio L0 / L0 rate This shows that the load-independent point fluctuates when the load is changed.

[0028] As is clear from FIG. 3B, the output voltage Vo has a maximum point at the operating frequency, which is the load-independent point 101, and at this point, the phase difference θ is 0 degrees (symbol 102), making it possible to achieve load independence and zero-volt switching (ZVS).

[0029] As shown in Figure 3A, a change in inductance L0 causes the output voltage Vo to change from the load-independent point 101 to 111, the phase difference θ to 0 degrees (symbol 112), and the operating frequency to be controlled accordingly. Also, as shown in Figure 3C, a change in inductance L0 causes the output voltage Vo to change from the load-independent point 101 to 121, the phase difference θ to 0 degrees (symbol 122), and the operating frequency to be controlled accordingly.

[0030] FIG. 4 is a graph showing an example of control when frequency control is performed by the hill climbing method in the resonant power conversion circuit of FIG. 1 in the graph of FIG. 3B. As is clear from FIG. 4, when frequency control is performed by the hill climbing method when the load-independent point 101 is at the maximum point of the output voltage curve or the desired voltage, as shown in SS1 to SS5, the frequency is changed in one direction from a preset frequency, a reversal of the voltage slope is detected, the direction of frequency change is reversed, and this is repeated to search for the voltage maximum point or the desired voltage. Note that the latter case of "searching for the desired voltage" is as follows. When the load fluctuation range is widened and the load becomes light (load resistance is large), the RL / RL in FIGS. 3A to 3C rate =8, 10, it does not have a maximum point. Therefore, instead of the maximum point, the target value of control can be controlled so that the output voltage value (the resonant circuit setting that results in this point being at or near the maximum point) becomes the desired voltage, without depending on changes in the graph due to load fluctuations.

[0031] FIG. 5 is a flowchart showing the operating frequency determination process executed by the control circuit 10 of FIG.

[0032] In step S1 of FIG. 5, the output voltage Vo of the resonance circuit 1 is detected and set as the output voltage V0. Next, in step S2, it is determined whether the output voltage V0 ≥ Vt. If YES, the process proceeds to step S3; if NO, the process proceeds to step S9. In step S3, the operating frequency f is decreased by a predetermined shift frequency Δf, that is, (f - Δf) is substituted for the operating frequency f. The output voltage Vo of the resonance circuit 1 is detected, and the output voltage Vo is substituted for the voltage V1. Also, in step S 4, the operating frequency f is increased by a predetermined shift frequency Δf (returned to the original operating frequency), that is, (f + Δf) is substituted for the operating frequency f. The output voltage Vo of the resonance circuit 1 is detected, and the output voltage Vo is substituted for the voltage V2.

[0033] Next, in step S5, it is determined whether V0 < V1 and V1 > V2. If YES, the process proceeds to step S6; if NO, the process proceeds to step S7. In step S6, the operating frequency f is decreased by a predetermined shift frequency Δfd, that is, (f - Δfd) is substituted for the operating frequency f, and then the process returns to step S1. On the other hand, in step S7, it is determined whether V0 > V1 and V1 < V2. If YES, the process proceeds to step S8; if NO, the process returns to step S1. In step S8, the operating frequency f is increased by a predetermined shift frequency Δfu, that is, (f + Δfu) is substituted for the operating frequency f, and then the process returns to step S1. Further, in step S9, the operating frequency f is determined as the operating frequency at the load-independent point, and the operating frequency determination process is terminated.

[0034] Note that in the operating frequency determination process of FIG. 7, the shift frequencies Δf, Δfu, and Δfd correspond to the progress width df of FIG. 8.

[0035] FIG. 6 is a graph showing a control example in a graph of the output voltage Vo with respect to the operating frequency f when the operating frequency is determined by the operating frequency determination process of FIG. 5. As is clear from FIG. 6, it can be seen that in the characteristics of the output voltage Vo with respect to the operating frequency, the operating point reaches the load-independent point 101 via the operating point A and the operating point B.

[0036] Fig. 7 is a flowchart showing in detail the operating frequency determination process executed by the control circuit 10 of Fig. 1. When executing the operating frequency determination process of Fig. 7, the following initialization process is first executed. Note that each numerical value is an example.

[0037] <Initialization process> Boundary value of evaluation function value: EVAL_BOUNDARY←0.025 Default value of progress width: DEFAULT_DF←9.0×10 3 Default value of operating frequency: DEFAULT_F←0.943×10 6 Maximum sampling count value: SAMPLING_COUNT_MAX←2000 Maximum operating frequency: MAX_F←1.2×10 6 Minimum operating frequency: MIN_F←0.8×10 6 Target voltage: V_REF←1.44 Current value of evaluation function: evalNow←0 Preset value of evaluation function value: evalPre←1.0×10 10 Progression width: dF←DEFAULT_DF Current value of operating frequency: fNOW←DEFAULT_F Operating frequency preset value: fPre←DEFAULT_F Sampling count value: samplingCount←0

[0038] In step S11 of FIG. 7, after inputting the sample value vSample of the output voltage Vo of the resonant circuit 1, an operating frequency change interval process P1 consisting of steps S11 to S12 is executed.

[0039] The operating frequency change interval process P1 is a process that enables the operating frequency to be changed every number of times defined by the maximum value of the sampling count, SAMPLING_COUNT_MAX. In step S12, the sampling count, samplingCount, is incremented by 1, and in step S13, it is determined whether samplingCount≧SAMPLING_COUNT_MAX. If YES, the process proceeds to step S14, and if NO, the process proceeds to step S22. In step S22, the preset value fPre of the operating frequency is substituted for the current value fNow of the operating frequency, and the process proceeds to step S38.

[0040] Next, in step S14, an evaluation function value calculation process P2 is executed to calculate an evaluation function value evalNow such that the evaluation function value decreases as the sample value vSample of the detected output voltage Vo approaches the target voltage V_REF. Specifically, the current value evalNow of the evaluation function value is calculated using, for example, the following equation.

[0041] evalNow=(vSample-V_REF) 2

[0042] Next, a progress width determination process P3 consisting of steps S15 to S17 is executed.

[0043] Fig. 8 is a diagram showing a graph for setting the progress width df in the progress width determination process P3 of Fig. 7. As shown in Fig. 8, if the evaluation function value becomes smaller than the boundary value EVAL_BOUNDARY, which is a constant reference value, the progress width df is set so that the absolute value |df| of the progress width df is reduced. In step S15, it is determined whether evalNow≦EVAL_BOUNDARY, and if YES, the process proceeds to step S16, while if NO, the process proceeds to step S17. In step S16, the progress width df is calculated using, for example, the following equation, and then the process proceeds to step S13.

[0044]

number

[0045] On the other hand, in step S17, the progress width df is calculated using, for example, the following equation, and then the process proceeds to step S13.

[0046]

number

[0047] Next, an operating frequency search process P4 is executed using a hill-climbing method, consisting of steps S18 to S21. In the operating frequency search process P4, if the current evaluation is better than the previous evaluation, the search proceeds in the same direction, but if it is worse, the search direction is changed. In step S18, it is determined whether evalNow≦evalPre, and if YES, the process proceeds to step S19, whereas if NO, the process proceeds to step S20. In step S19, the progress width df is substituted for the progress width df, and then the process proceeds to step S21. On the other hand, in step S20, the progress width df is negatively converted to −df, and then the process proceeds to step S21. In step S21, the preset value fPre of the operating frequency and the progress width df are added together, and the sum is set as the current value fNow of the operating frequency, and then the process proceeds to step S31.

[0048] Next, a variable change process P5 consisting of steps S31 to S33 is executed. In step S31, the current value fNow of the operating frequency is set as the preset value fPre of the operating frequency, and in step S32, the current value evalNow of the evaluation function value is set as the preset value evalPre of the evaluation function value. Next, in step S33, the sampling count value samplingCount is reset to 0, and the process proceeds to step S34.

[0049] Next, the bandwidth limiting process P6 consisting of steps S34 to S37 is executed. In step S34, it is determined whether fNow > MAX_F. If YES, the process proceeds to step S35; if NO, the process proceeds to step S36. In step S35, the maximum operating frequency MAX_F is set as the current value fNow of the operating frequency, and the process proceeds to step S36. In step S36, it is determined whether fNow < MAX_F. If YES, the process proceeds to step S37; if NO, the process proceeds to step S38. In step S37, the minimum operating frequency MIN_F is set as the current value fNow of the operating frequency, and the process proceeds to step S38.

[0050] In step S38, it is determined that the operating frequency has been determined, and the current value fNow of the operating frequency is output as the operating frequency, and the operating frequency determination process ends.

[0051] As described above, according to the resonant power conversion circuit according to this embodiment, it is a resonant power conversion circuit including a resonant circuit 1 having an LC resonant circuit and a switching element Q1, which outputs the output voltage of the resonant circuit 1 to the load RL, and based on the output voltage, determines the operating frequency of the resonant power conversion circuit and controls the on / off of the switching element Q1 using the gate voltage signal Vf (drive control signal) at the determined operating frequency. Here, the resonant circuit 1 determines the operating frequency at which the output voltage is held at the maximum peak value. Therefore, even if the inductance or capacitance of the resonant circuit 1 changes, the resonant circuit 1 can maintain the operating frequency so that the output voltage is held at the maximum peak value, thereby maintaining its phase state and realizing load-independent characteristics and zero-voltage switching (ZVS) in the resonant circuit 1. Thereby, the above-mentioned problems 1 and ⒉ can be solved.

[0052] (Application Example) Fig. 9 is a block diagram showing an example of the configuration of a contactless power supply system when the resonant power conversion circuit of Fig. 1 is applied to the contactless power supply system. In Fig. 9, components 12 to 24 correspond to the resonant circuit 1 of Fig. 1, component 20 corresponds to the detection circuit 2 of Fig. 1, and component 17 corresponds to the control circuit 10 of Fig. 1.

[0053] 9, the contactless power supply system includes a power transmitting device 100 and a power receiving device 200. The power transmitting device 100 includes a power factor correction circuit (hereinafter referred to as PFC circuit) 11, a PFC control unit 16 that controls the operation of the PFC circuit 11, an inverter circuit 12, a power transmitting LC resonant circuit 13, an inverter control unit 17, and a wireless communication circuit 15 having an antenna 15A. The power receiving device 200 includes a power receiving LC resonant circuit 14, a rectifier circuit 22, a DC / DC converter 23, a load 24, a 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. The PFC circuit 11 improves the power factor by shaping the waveform of an input current based on a predetermined AC voltage. The inverter circuit 12 converts the input predetermined DC voltage into an AC voltage.

[0054] Here, the power transmitting device 100 and the power receiving device 200 are located near each other for power supply, for example, for charging. As a result, the power transmitting LC resonant circuit 13 and the power receiving LC resonant circuit 14 are, for example, electromagnetically coupled to form a transformer TR1. Furthermore, the wireless communication circuit 15 and the wireless communication circuit 25 transmit and receive necessary information data by performing wireless communication using antennas 15A and 25A, respectively.

[0055] The PFC circuit 11 may be a cascade-connected circuit of a rectifier circuit and a DC / DC converter. The DC / DC converter converts the input DC voltage into a predetermined DC voltage. The PFC circuit 11 or the cascade-connected circuit of a rectifier circuit and a DC / DC converter may be omitted. When the PFC circuit 11 is omitted, the PFC control unit 16 can be eliminated. When a cascade-connected circuit of a rectifier circuit and a DC / DC converter is provided instead of the PFC circuit 11, a voltage control unit that controls the DC / DC converter is provided instead of the PFC control unit 16.

[0056] Furthermore, at least one of the DC / DC converter on the power transmission side and the DC / DC converter 23 on the power reception side may be omitted, but the output voltage needs to be controlled as follows.

[0057] In the contactless power transfer system of FIG. 9, when the distance between inductors L1 and L2, which are the power transmitting and receiving coils, changes, the degree of coupling k changes. This changes the resonance characteristics, and the output voltage changes. Here, to keep the output voltage constant, it is necessary to control the voltage in the DC / DC converter on the power transmitting side and / or the power receiving side. Here, in order to control the DC / DC converter on the power transmitting side, it is necessary to transmit information about the output voltage detected by the control unit 20 on the power receiving side to the voltage control unit of the DC / DC converter on the power transmitting side via wireless communication circuit 25.15. Meanwhile, the DC / DC converter 23 on the power receiving side is configured to be controlled by the control unit 20 based on information about the output voltage detected by the control unit 20 on the power receiving side.

[0058] 1, a PFC circuit 11 converts an 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 power factor correction processing on the input voltage using a predetermined power factor correction method under the control of a PFC control unit 16, and outputs an output voltage to an inverter circuit 12. The inverter circuit 12 converts the input DC voltage into a predetermined AC voltage by switching based on, for example, a PWM gate signal from an inverter control unit 17, and outputs the AC voltage to a rectifier circuit 22 via a power transmitting LC resonant circuit 13 and a power receiving LC resonant circuit 14.

[0059] Here, the PFC control unit 16 receives load information such as the output voltage and output current to the load 24 as follows: Control unit 10A, for example, the power transmitting LC resonant circuit 13 is a resonant circuit composed of an inductor L1 and a capacitor C1, and resonates at a predetermined resonant frequency fr based on an input voltage to generate AC power including an AC voltage having the resonant frequency fr, and transmits the AC power to the power receiving LC resonant circuit 14 coupled to the power transmitting LC resonant circuit 13.

[0060] 1, the power receiving LC resonant circuit 14 is an LC resonant circuit including an inductor L2 and a capacitor C2, as shown in FIG. 11A, for example, and receives AC power from the power transmitting LC resonant circuit 13 and outputs an 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 the DC voltage to the load 24. Control unit The PFC control unit 20 detects the output voltage and output current to the load 24 and transmits load information including the detected information to the PFC control unit 16 via the wireless communication circuits 25 and 15. The inverter control unit 17 also generates, for example, a predetermined gate voltage signal Vf based on the load information to control the inverter circuit 12, thereby causing the inverter circuit 12 to operate at a predetermined operating frequency.

[0061] The rectifier circuit 22 may be, for example, a half-wave rectifier circuit, a full-wave rectifier circuit, a full-bridge rectifier circuit, a half-active rectifier circuit, a voltage doubler rectifier circuit, or a current doubler rectifier circuit.

[0062] As described above, according to the contactless power transfer system of this embodiment, by configuring it using the resonant power conversion circuit of Fig. 1, even if the inductance or capacitance of the resonant circuit 1 changes, the resonant circuit 1 can maintain the operating frequency so that it maintains the maximum value at which the output voltage is maximized, thereby maintaining the phase state and achieving load-independent characteristics that are not dependent on the load and zero-volt switching (ZVS) in the resonant circuit 1. This solves the above-mentioned problems 1 and 2, and allows power to be transmitted from the power transmitting device 100 to the power receiving device 200.

[0063] Furthermore, as described above, by applying the resonant power conversion circuit 1 according to this embodiment to the partial circuits of the inverter circuit 12, the power transmitting LC resonant circuit 13, and the power receiving LC resonant circuit 14, it is possible to reduce the DC / DC converter 23 and its control unit for controlling the output characteristics.

[0064] Hereinafter, the power transmission LC resonant circuit 13 will be referred to as the LC resonant circuit 13. 、 The power receiving LC resonant circuit 14 is referred to as the LC resonant circuit 14.

[0065] (Variations, etc.) Below, we will explain modified examples of the LC resonant circuits 13 and 14. The inductors below include self-inductance, magnetizing inductance, leakage inductance, etc., and L31, L41, and L42 indicate the use of inductors different from these. Furthermore, the following configuration examples are merely basic circuit types, and the numbers of inductors and capacitors connected in series or parallel may be changed.

[0066] Fig. 10A is a circuit diagram showing an example of the configuration of the LC resonant circuit 13 in Fig. 9. In Fig. 10A, the LC resonant circuit 13 is configured by a series circuit of an inductor L1 and a capacitor C1. Here, the LC resonant circuit 13 of the power transmitting device 100 may be configured by any one of the following LC resonant circuits 13A to 13E.

[0067] Fig. 10B is a circuit diagram showing a configuration example of an LC resonant circuit 13A according to Modification 1. In Fig. 10B, the LC resonant circuit 13A is formed of a parallel circuit of an inductor L1 and a capacitor C1.

[0068] FIG. 10C is a circuit diagram showing a configuration example of an LC resonant circuit 13B according to Modification 2. In FIG. B is composed of a series circuit of an inductor L1 and a capacitor C1, and a parallel circuit with a capacitor C31.

[0069] FIG. 10D is a circuit diagram showing a configuration example of an LC resonant circuit 13C according to Modification 3. In FIG. C is composed of a parallel circuit of an inductor L1 and a capacitor C31, and a series circuit with the capacitor C1.

[0070] 10E is a circuit diagram showing a configuration example of an LC resonant circuit 13D according to Modification 4. In FIG. 10E, the LC resonant circuit 13D includes a series circuit of an inductor L1 and a capacitor C1, Capacitor C 31 and includes an inductor L31 connected in series to the parallel circuit.

[0071] Fig. 10F is a circuit diagram showing a configuration example of an LC resonant circuit 13E according to Modification 5. In Fig. 10F, the LC resonant circuit 13E includes a series circuit of an inductor L1 and a capacitor C1, and a parallel circuit with an inductor L31, and a capacitor C32 connected in series with the series circuit.

[0072] As is clear from FIGS. 10A to 10F, the LC resonant circuits 13, 13A to 13E include at least one inductor and at least one capacitor, and each of the inductors and each of the capacitors are connected in series or in parallel.

[0073] The LC resonant circuit 14 of the power receiving device 200 in FIG. 9 may be configured as any one of the following LC resonant circuits 14A to 14E.

[0074] Fig. 11A is a circuit diagram showing an example of the configuration of the LC resonant circuit 14 of Fig. 9. In Fig. 11A, the LC resonant circuit 14 is formed by a series circuit of an inductor L2 and a capacitor C2.

[0075] Fig. 11B is a circuit diagram showing a configuration example of an LC resonant circuit 14A according to Modification 6. In Fig. 11B, the LC resonant circuit 14A is formed by a parallel circuit of an inductor L2 and a capacitor C2.

[0076] Fig. 11C is a circuit diagram showing a configuration example of an LC resonant circuit 14B according to Modification 7. In Fig. 11C, the LC resonant circuit 14B is formed by a series circuit of an inductor L2 and a capacitor C2, and a parallel circuit with a capacitor C41.

[0077] Fig. 11D is a circuit diagram showing a configuration example of an LC resonant circuit 14C according to Modification 8. In Fig. 11D, the LC resonant circuit 14C is formed by a parallel circuit of an inductor L2 and a capacitor C41, and a series circuit with a capacitor C2.

[0078] FIG. 11E is a circuit diagram showing a configuration example of an LC resonant circuit 14D according to Modification 9. E 1, the LC resonant circuit 14D includes an inductor L41 connected in series to a series circuit of an inductor L2 and a capacitor C2, and a parallel circuit of the inductor L41 and a capacitor C41.

[0079] 11F is a circuit diagram showing a configuration example of an LC resonant circuit 14E according to Modification 10. F 1, the LC resonant circuit 14E includes a series circuit of an inductor L2 and a capacitor C2, and a capacitor C42 connected to a parallel circuit with an inductor L42.

[0080] As is clear from FIGS. 11A to 11F, the LC resonant circuits 14, 14A to 14E include at least one inductor and at least one capacitor, and each of the inductors and each of the capacitors are connected in series or in parallel.

[0081] In the above embodiment, the maximum value of the output voltage Vo of the resonant circuit 1 is found using the hill climbing method, and the corresponding operating frequency is determined. However, the present invention is not limited to this, and other maximum value search methods such as the best-first search method, the optimization search method, the steepest descent method, and the conjugate gradient method may be used to find the maximum value of the output voltage Vo of the resonant circuit 1 and determine the corresponding operating frequency.

[0082] In the above embodiment, the MOS transistor Q1 is used as the switching element, but the present invention is not limited to this, and a switching element such as a bipolar transistor may also be used.

[0083] In the above embodiment, the detection circuit 2 detects the output voltage of the resonant circuit 1 and outputs it to the calculation control unit 3, but the present invention is not limited to this. The detection circuit 2 may detect output information such as the output current of the resonant circuit 1 and output it to the calculation control unit 3, and the calculation control unit 3 may control the resonant power conversion circuit including the resonant circuit 1 to determine the operating frequency based on the output information. [Industrial Applicability]

[0084] As described above in detail, the present invention can provide a resonant power conversion circuit that can solve the above two problems and can also significantly reduce calculation costs compared to conventional techniques, and a contactless power supply system that uses the resonant power conversion circuit. [Explanation of symbols]

[0085] 1 resonant circuit 2. Detection circuit 3. Calculation control unit 4. Signal Generator 5 DC power supply 10 Control circuit 11 Power factor correction circuit (PFC circuit) 12 Inverter circuit 13 Power transmission LC resonant circuit (LC resonant circuit) 14 Receiving LC resonant circuit (LC resonant circuit) 15 Wireless communication circuit 15A Antenna 16 PFC control section 17 Inverter control unit 20 Control Unit 22 Rectifier circuit 23 DC / DC converter 24 Load 25 Wireless communication circuit 25A Antenna 30 AC power supply Cs, C0 to C2, Csm capacitors D1 rectifier diode Lf,L0 inductor Q1 MOS transistor R1,R2 resistance RL load resistance TR1 transformer

Claims

1. a resonant circuit including a first LC resonant circuit and a switching element, and outputting an output voltage or an output current to a load; a detection circuit for detecting output information, which is the output voltage or the output current; a calculation control unit that uses a predetermined search method based on the detected output information to search for a desired voltage different from the voltage at the maximum point when the load becomes a light load in which the resistance value of the load is greater than the resistance value at the voltage at the maximum point in the characteristics of the output information versus the operating frequency, and determines an operating frequency corresponding to the desired voltage found; a signal generating unit that generates a drive control signal having the determined operating frequency and controls the frequency of the switching element based on the drive control signal; the resonant circuit has a characteristic of output information with respect to the operating frequency having a load-independent point that is independent of the load and corresponds to the desired voltage; the resonant circuit feeds back a drive control signal including the output information to the switching element, and drives the switching element at the load-independent point by frequency control using the drive control signal. Resonant power conversion circuit.

2. The search method is a hill-climbing method.

2. The resonant power conversion circuit according to claim 1.

3. the signal generating unit controls the frequency of the switching element by controlling the switching of the switching element based on the drive control signal, which is a PWM signal; 3. The resonant power conversion circuit according to claim 1 or 2.

4. The drive control signal is a binary signal that turns on or off the switching element.

4. The resonant power conversion circuit according to claim 3.

5. A power transmitting device including the resonant power conversion circuit according to any one of claims 1 to 4; a power receiving device; A contactless power supply system comprising: The power receiving device is a second LC resonant circuit coupled to the first LC resonant circuit and configured to receive AC power from the first LC resonant circuit; a rectifier circuit that rectifies the AC power received by the second LC resonant circuit into DC power and outputs the DC power to a predetermined load; A contactless power supply system comprising:

6. The power transmitting device further comprises: an inverter circuit provided in a preceding stage of the first LC resonant circuit, which converts a predetermined DC voltage into an AC voltage and outputs the AC voltage to the first LC resonant circuit; The contactless power supply system according to claim 5 .

7. The power receiving device further comprises: a power receiving control unit that detects output information of the power receiving device and wirelessly transmits the detected information; The power transmitting device further comprises: a power factor correction circuit provided in a stage preceding the first LC resonant circuit, for correcting a power factor by shaping a waveform of an input current based on a predetermined AC voltage; a power factor correction circuit control unit that receives the wirelessly transmitted output information by wireless and controls the operation of the power factor correction circuit based on the output information; The contactless power supply system according to claim 6 , comprising:

8. a first DC / DC converter inserted between the rectifier circuit and the load in the power receiving device, for converting an input DC voltage into a predetermined DC voltage; a second DC / DC converter provided in the power transmission device at a stage preceding the inverter circuit, the second DC / DC converter converting an input DC voltage into a predetermined DC voltage; and a voltage control unit that controls one of the first DC / DC converter and the second DC / DC converter based on an output voltage of the load when a degree of coupling k between an inductor of the first LC resonant circuit and an inductor of the second LC resonant circuit changes, so that the output voltage becomes a predetermined voltage; The contactless power supply system according to claim 6 or 7, comprising:

9. The power transmitting device further comprises: a rectifier circuit provided in a stage preceding the inverter circuit, which rectifies a predetermined AC voltage, converts it into a DC voltage, and outputs the DC voltage to the inverter circuit; The contactless power supply system according to any one of claims 6 to 8, comprising:

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