Non-contact power receiving device, non-contact power supply system, and method therefor

Abstract

At least a portion of the alternating current received by the power receiving coil (31) at a position that can be magnetically coupled to the power transmission coil (51) is supplied from a circuit (331) functioning as a current source to a load (45). At this time, electrical characteristics as a current source in the circuit are detected, and switching between a first state in which a first current is supplied from the current source to the load and a second state in which a second current smaller than the first current is supplied is performed. And feed-forward control is performed on the ratio of the first state or the second state to one cycle of the alternating current according to the detected electrical characteristics.

Description

Mutual citation of related applications

[0001] This application is based on and claims priority to Japanese Patent Application No. 2023-55505, filed on March 30, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure relates to a contactless method of receiving or supplying electricity. Background Technology

[0003] In the case of non-contact power supply, techniques for controlling the supply current are sometimes required. For example, International Publication No. WO2020 / 129178 discloses a method that converts alternating current (AC) received by magnetic field coupling into direct current (DC), and controls the current flowing through a capacitor on the output side where the DC voltage is applied, based on the current flowing through the load, thereby controlling the supply current. In this case, the period during which the current flowing through the capacitor is controlled to be zero in order to supply power at the desired current amount. Summary of the Invention

[0004] However, in the technology described in the aforementioned publication, the period when the current is zero is controlled by feedback control, therefore, the control responsiveness is sometimes insufficient. For example, when the power supplied from the power supply side increases sharply, the control on the receiving device side may be unable to cope, resulting in excessive power received or EMC deterioration during the transition. The problem is that when the power received becomes excessive, overcurrent may be generated in the battery, thus requiring additional structures to prevent these overcurrents.

[0005] This disclosure can be implemented in the following ways or in the following applications.

[0006] [1] The non-contact power receiving device of this disclosure includes: a power receiving unit, the power receiving unit including a power receiving coil and receiving alternating current through magnetic field coupling; a power supply unit, the power supply unit connected to the power receiving unit and supplying power to a load as a current source; a detection unit, the detection unit detecting the electrical characteristics of the power supply unit as the current source; a current switching unit, the current switching unit switching the power supply unit between a first state supplying a first current to the load and a second state supplying a second current smaller than the first current to the load; and a control unit, the control unit determining the ratio of the first state or the second state to the period of the alternating current based on the detected electrical characteristics, and performing feedforward control on the current switching unit based on the ratio.

[0007] [2] Furthermore, the non-contact power receiving method of this disclosure supplies at least a portion of the alternating current received by the receiving coil at a location that can couple with the magnetic field of the power supply coil from the circuit that functions as a current source to the load, detects the electrical characteristics of the circuit that functions as the current source, switches between a first state that supplies a first current from the current source to the load and a second state that supplies a second current smaller than the first current, and performs feedforward control on the ratio of the first state or the second state to one cycle of the alternating current based on the detected electrical characteristics.

[0008] [3] Furthermore, the contactless power supply method of this disclosure applies an AC voltage of a specified frequency to a power supply coil located at a position where it can couple with the magnetic field of the power receiving coil, supplies at least a portion of the AC current received by the power receiving coil at the position where it can couple with the magnetic field of the power supply coil from a circuit that functions as a current source to the load, detects the electrical characteristics of the circuit that function as the current source, switches between a first state of supplying a first current from the current source to the load and a second state of supplying a second current smaller than the first current, and performs feedforward control on the ratio of the first state or the second state to one cycle of the AC current based on the detected electrical characteristics. Attached Figure Description

[0009] The above-mentioned objects, other objects, features, and advantages of this disclosure will become clearer with reference to the accompanying drawings and the following detailed description. The accompanying drawings are described below. Figure 1 This is a schematic diagram illustrating the structure of a contactless power supply system according to an embodiment. Figure 2 This is a schematic diagram of the power supply and receiving devices that constitute a contactless power supply system. Figure 3 This is an explanatory diagram showing a structural example of multiple power supply units. Figure 4 This is an explanatory diagram showing the relationship between the operating state of the current switching unit and the state of the load current. Figure 5 This is a structural diagram showing a first embodiment of the power receiving device. Figure 6A This is an explanatory diagram showing the different turn-on times caused by the switching on and off of the current switching unit. Figure 6B It is a schematic diagram illustrating the relationship between turn-on time and output current and load current. Figure 7 This is an explanatory diagram showing the change in load current achieved through feedforward control when the current supplied increases. Figure 8AThis is a structural diagram showing an embodiment of the power receiving device used in the second embodiment. Figure 8B This is an explanatory diagram illustrating a control example where the feedforward control quantity is increased when the current increases sharply. Figure 9A This is a structural diagram showing the power receiving device used in the third embodiment. Figure 9B This is a flowchart illustrating the control process of the synchronous rectifier in the third embodiment. Figure 10 This is a structural diagram showing the power receiving device used in the fourth embodiment. Figure 11 This is a structural diagram showing the power receiving device used in the fifth embodiment. Figure 12 This is a structural diagram showing a modified example of the fifth embodiment. Figure 13 This is a structural diagram showing the power receiving device used in the sixth embodiment. Detailed Implementation

[0010] A. First implementation method: (A1) Overall structure of the contactless power supply system: Figure 1 A schematic structure of a contactless power supply system 100 including a contactless power receiving device 30 according to the first embodiment is shown. As shown, the contactless power supply system 100 consists of multiple power transmission devices 50 buried under the road surface SF and in the soil, and a contactless power receiving device 30 installed on a mobile body 20 that automatically travels on the road surface SF. The mobile body 20 includes a drive wheel 21 driven by a motor (not shown) included in a load device 45, a driven wheel 22 that supports the mobile body 20 together with the drive wheel 21 so that it can move on the road surface SF, and a receiving coil 31 disposed under the base plate of the mobile body 20. The receiving coil 31 receives the supply of alternating current by magnetic coupling with the power transmission coil 51 of the power transmission device 50 prepared on the road surface SF side, and supplies power to the load device 45. Furthermore, the power supply device 50 and the contactless power supply system 100 including the power supply device 50 are not limited to systems that supply power to the contactless power receiving device 30 of the mobile body 20. Any device and system that supplies power in a contactless manner is acceptable. The power receiving device can also be a device or system that supplies power to devices that are not mobile bodies, such as portable terminals. The mobile body 20 is not limited to traveling on outdoor roads, but also includes transport vehicles used indoors, such as in factories and hospitals. The mobile body 20 can have several wheels, or it can move using methods other than wheels, such as magnetic levitation.

[0011] In addition to being buried under the road surface SF, the power transmission device 50 can also be installed on the road surface, or on a wall or ceiling. In this case, the non-contact power receiving device 30 can be positioned at a predetermined location within the mobile body 20, corresponding to the installation location of the power transmission device 50. For example, if the power transmission device 50 is installed on a wall, the non-contact power receiving device 30 can be positioned on the side of the mobile body 20. Alternatively, the non-contact power receiving device 30 can be moved within the mobile body 20 in coordination with the installation location of the power transmission device 50, or multiple non-contact power receiving devices 30 can be prepared in advance and switched between.

[0012] In this embodiment, multiple power supply devices 50 that supply power to the non-contact power receiving device 30 of the mobile body 20 each have the same structure and are arranged along the movement path of the mobile body 20. Of course, the power supply devices 50 are not limited to the movement path of the mobile body 20, and can also be arranged two-dimensionally on the road surface SF. Each power supply device 50 is connected to a common main power line RFP. High-frequency (e.g., 85kHz) alternating current at frequency f1 is supplied from the main power supply device 60 to the main power line RFP. In this embodiment, each power supply device 50 has the same structure, but for example, power supply coils 51 of different sizes can be alternately arranged, as long as power can be supplied, the different structures are acceptable. Of course, there can also be only one power supply device 50.

[0013] The main power supply unit 60 receives a low-frequency (e.g., 60Hz) AC supply from the main power supply 65 and converts it to high-frequency AC. A known structure includes, on the side of the main power supply unit 60 receiving power from the main power supply 65, a noise filter for AC output, a PFC circuit, an inverter, and a filter. The power supplied from the main power supply 65 is converted to AC at the aforementioned frequency by the inverter and output to the main power line RFP.

[0014] Figure 2The schematic structure of the power supply device 50 and the contactless power receiving device 30 is shown. The figure shows one of the multiple power supply devices 50 supplying power to the contactless power receiving device 30 of the moving body 20. At this time, the power supply coil 51 of the power supply device 50 is magnetically coupled to the power receiving coil 31 of the contactless power receiving device 30, and an induced current (alternating current) flows through the power receiving coil 31 when power is supplied from the power supply device 50. The contactless power receiving device 30 includes a power receiving section 33, a detection section 70, a power supply section 40, a current switching section 75, and an FF control section 71, supplying the required power to the load device 45. The power receiving section 33 receives power from the power supply device 50 through the induced current generated in the power receiving coil 31. The power supply section 40 includes a circuit structure that functions as a current source, and also includes a rectifier 44 that rectifies the alternating current received by the power receiving section 33. The rectifier 44 can be a full-wave rectifier or a half-wave rectifier that utilizes a diode bridge, or a synchronous rectifier that uses a switching element in a part of the bridge and switches the switching element on or off alternately with the input AC to perform rectification.

[0015] The detection unit 70 detects the electrical characteristics of the circuit in the power unit 40 that functions as a current source. In this embodiment, it detects the current value Iout output from the circuit that functions as a current source. The structure of the circuit that functions as a current source will be described in detail later, but in terms of circuit structure, the voltage value, which is equivalent to the current value, can also be detected as an electrical characteristic. The current switching unit 75 switches between a first state that supplies a first current to the load and a second state that supplies a second current smaller than the first current to the load. The specific structure of the current switching unit 75 will be described in detail later. The FF control unit 71 controls the switching between the first and second states of the current switching unit 75. The FF control unit 71 is configured as a control device that performs feedforward control. Feedforward control is performed to make the current value Id flowing in the controlled object, here the load device 45, approach the target value I*. Generally, feedback control is performed to make the control quantity approach the target value. In feedback control, the output current value Iout on the input side, here from the power receiving unit 33, is controlled based on the difference between the target value and the control quantity. In contrast, the FF control unit 71 of this embodiment controls the current switching unit 75 based on the output current value Iout before the load current value Id of the load device 45 changes. Details of this control will be summarized later. Furthermore, the FF control unit 71 can also be implemented using a discrete circuit structure, but it is also easily implemented using arithmetic and logical operations performed by a computer executing a program stored in memory.

[0016] The structural examples of each part constituting the non-contact power receiving device 30 will be described in turn. Figure 3Examples of the structure of multiple power receiving units 33 and power supply units 40 are illustrated. In the illustrated structural examples, if the power supply unit 40 functions as a current source, a current source circuit 331 with transient characteristics, which is a transient filter, is incorporated. In structural example 1, the power receiving unit 33 consists of a power receiving coil 31 and two resonant capacitors Ct1 and Ct2 connected on both sides thereon. The current source circuit 331, which serves as a transient filter, is located at the rear end of the power receiving unit 33. The transient filter in structural example 1 includes a T-LCL type structure, which consists of a transient capacitor Cim and two sets of reactors L11, L12 and L21, L22 sandwiching the transient capacitor Cim and connected on both sides. Of course, in addition to the T-LCL type, π-CLC type or T-LCLC type transient filters can also be used.

[0017] In Structural Example 1, a current switching unit 75 is provided at the downstream end of the current source circuit 331 using a transient filter, and a rectifier 44 is connected to the output side of the current source circuit 331. In Structural Example 1, the rectifier 44 is configured as a full-wave rectifier consisting of four diodes D1 to D4 connected in a bridge configuration. The alternating current output from the current source circuit 331 is converted into DC by the rectifier 44 and supplied to the load device 45, for example, to charge the battery included in the load device 45. The current switching unit 75 is configured as a contact that short-circuits the two power lines P1 and P2 of the current source circuit 331. The contact of the current switching unit 75 is driven by the FF control unit 71.

[0018] The transient filter, which functions as a current source circuit, can be configured either as in Structure Example 1, which includes all the reactors L11 to L22 that make up the circuit, or as in Structure Example 2, which excludes the reactors L11 and L12 on the side connected to the receiving part 33. The current source circuit 332 also functions in the same way as in Structure Example 1. Furthermore, as shown in Structure Example 3, the circuit structure consisting of the power supply coil 51 and resonant capacitors Ct1 and Ct2, and the receiving coil 31 and resonant capacitors Ci1 and Ci2, can also be used as a current source circuit 333 with transient characteristics. The current source circuit 333 also functions in the same way as in Structure Examples 1 and 2.

[0019] Figure 4The diagram illustrates the state where power supplied from an AC current source, such as the current source circuit 331, is supplied as DC power to the load device 45. When the current switching unit 75 is in the off state, in the case where the power line P1 is positive due to the power supply from the current source circuit 331 (positive half-cycle), the current flows to the load device 45 as shown by the dashed line Ia. On the other hand, in the case where the power line P2 is positive due to the power supply from the current source circuit 331 (negative half-cycle), the current flows to the load device 45 as shown by the dashed line Ic. Furthermore, when the current switching unit 75 is in the on state, the power lines P1-P2 are short-circuited, and the current supplied by the current source circuit 331 flows through the current switching unit 75 as shown by the dashed lines Ib and Id, and does not flow to the rectifier 44 side. Therefore, the load device 45 is not supplied with current.

[0020] If the switching on and off of the current switching unit 75 is switched during half-cycles of the alternating current in the current source circuit 331, then as follows: Figure 4 As shown in the bottom section, a first state Pa, Pc and a second state Pb, Pd are generated in one cycle of the alternating current. In the first state Pa, Pc, power is supplied to the load device 45 via rectifier 44. In the second state Pb, Pd, no power is supplied. The power supplied to the load device 45 increases or decreases according to the proportion of the first state interval within one cycle of the alternating current. The first state interval Pa, Pc and the second state interval Pb, Pd are equivalent to the time of the first state and the time of the second state on the time axis. By controlling the proportion of the time Ton of the first state interval to one cycle Tt of the alternating current, the amount of power supplied to the load device 45, specifically the amount of current supplied to the load device 45, can be controlled.

[0021] Therefore, as Figure 5 As shown in one example, this embodiment employs the following structure: a detection unit 70 is provided to detect the output current Iout of the current source circuit 331, and an FF control unit 71 performs feedforward control on and off of the current switching unit 75 based on the output current Iout. When the output current Iout is received from the detection unit 70, the FF control unit 71 refers to the on-time ratio mapping Tmp to obtain the ratio of the on-time Ton that should be used to turn on the current switching unit 75. The ratio of the on-time Ton that should be obtained relative to the output current Iout is pre-stored in the on-time ratio mapping Tmp. Alternatively, the on-time Ton can also be obtained by using a mathematical formula or function instead of the mapping.

[0022] Figure 6AThe diagram illustrates an example of the proportion of the on-time Ton. The upper part of the diagram illustrates that one cycle Tt of the alternating current is fixed, while the proportion of time during which the current switching unit 75 is turned on varies. In this example, the case with no on-time Ton is shown as Ton = 0, and the states where the on-time Ton gradually increases from short to long are shown as Ts, Tm, and Tl. Furthermore, Figure 6B In the diagram, the ratio of the on-time Ton to the output current Iout is shown on the right axis, while the load current Id supplied to the load device 45 at this time is shown on the left axis. The on-time Ton is 0 until the output current Iout becomes the predetermined value In, and the current switching unit 75 remains off. Therefore, if the power supplied from the power supply device 50 increases, causing the output current Iout to increase, the load current Id will also increase accordingly.

[0023] If the output current Iout exceeds the specified value In, the FF control unit 71 gradually increases the on-time Ton, which is the value of the on-time ratio mapping Tmp, based on the output current Iout. Therefore, as illustrated in the previous paragraph, the on-time Ton of the current switching unit 75 increases in the order of 0→Ts→Tm→T1. As the on-time Ton increases, the current switching unit 75 turns on. Figure 4 As the intervals Pb and Pd shown in the bottom column increase, the amount of electricity output to the load device 45 via rectifier 44 decreases.

[0024] In practice, when the contactless receiving device 30 receives contactless power from the receiving device 50, due to changes in the positional relationship between the transmitting coil 51 and the receiving coil 31, the output current Iout output by the receiving unit 33 may sometimes change drastically. Let's assume a step response as an example of a drastic change in output current Iout. Figure 7 The control implemented by this embodiment is shown in the figure.

[0025] Assuming the current to be output to the load device 45 is 10A, and the output current Tout from the current source circuit 331 changes from 10A to 20A in time t, if the load current Id is used to control the on-time Ton of the current switching unit 75 in order to make the load current Id become the target current I* (here, 10A), then from the characteristics of feedback control, a considerable amount of time is required before the load current Id becomes the target current I*. If the gain of the feedback control is increased in an attempt to improve responsiveness, the control will become unstable and prone to overshoot and undershoot.

[0026] In contrast, in this embodiment, such as Figure 7As shown, if the output current Iout increases sharply from 10A, the on-time Ton is increased to a predetermined on-time Tm by referring to the on-time proportional mapping diagram Tmp. Therefore, the load current Id returns to the target current I* (10A in this case) in a short time. In this example, since the output current Iout and the on-time Ton are set as a simple proportional relationship, overshoot will occur in the output current Iout during the period from t1 to t2 after the output current Iout changes. However, the overshoot will be eliminated in a short time, and after time t2, the output current Iout converges to the target current I*. The FF control unit 71 obtains the on-time Ton by referring to the on-time proportional mapping diagram Tmp. Therefore, it can switch the control quantity (on-time Ton in this case) at high speed without performing differential calculations as in feedback control.

[0027] B. Second implementation method: Figure 8A The diagram shows a general structure of the contactless power receiving device 30B used in the contactless power supply system of the second embodiment. The contactless power receiving device 30B of the second embodiment differs from the contactless power receiving device 30 of the first embodiment in that it includes a rate limiter 73 and the on-time Ton used by the FF control unit 71 when the output current Iout increases sharply. Otherwise, it is the same as the first embodiment.

[0028] In the contactless power receiving device 30B of the second embodiment, when the FF control unit 71 calculates the on-time Ton according to the on-time ratio mapping diagram Tmp, if the output current Iout exceeds a predetermined threshold change, such as Figure 8B As shown, the on-time Ton is not set to a value that is simply proportional to the output current Iout, but is further increased. In the illustrated example, during the time period t1 to t2 immediately after the output current Iout changes sharply, the on-time Ton is temporarily increased to the on-time Tl. Then, the on-time Ton is subsequently decreased to the on-time Tm, but at this time, due to the rate limiter 73, the on-time Ton gradually decreases at a certain rate. The rate limiter 73 does not function when the on-time Ton increases, and adjusts the on-time Ton in a manner that the rate of decrease does not become less than a predetermined rate when the on-time Ton decreases.

[0029] Thus, even when the output current Tout changes drastically, overshoot of the load current Id can be suppressed. In the illustrated example, it is easy to avoid the load current Id exhibiting a temporary, sharp increase as shown by the dashed line. Moreover, when the temporarily increased on-time T1 is reduced, the reduction ratio does not become excessive, thus sufficiently suppressing overshoot. If no overshoot occurs, overcurrent will not flow to the load device 45 such as the battery, thus easily preventing a shortened battery life due to overcurrent.

[0030] C. Third implementation method: Figure 9A The structure of the contactless power receiving device 30C constituting the contactless power supply system of the third embodiment is shown. The structure of the contactless power receiving device 30C in this embodiment differs from that of the rectifier in the contactless power receiving device 30 of the first embodiment. In the third embodiment, except that the rectifier is configured as a synchronous rectifier 44C, a portion of which is used as a current switching unit 75C, everything else is the same as in the first embodiment. As shown, the synchronous rectifier 44C forms a bridge through two diodes D1 and D2 in the upper arm and two switching elements SW1 and SW2 in the lower arm. The rectifier is a synchronous rectifier 44C, and during rectification, each time the polarity of the alternating current received by the power unit 40 changes, the switching elements SW1 and SW2 are switched on and off exclusively in a matching manner. As a result, as Figure 4 As shown in the top section, the synchronous rectifier 44C functions as a full-wave rectifier and supplies power to the load device 45 in DC mode.

[0031] Furthermore, if the FF control unit 71 simultaneously turns on (conducts) the two switching elements SW1 and SW2 constituting the lower arm connected to the power line P2, then the power lines P1 and P2 will become conductive through these switching elements SW1 and SW2. In this case, the two switching elements SW1 and SW2 function as current switching units. As a result, if... Figure 4 As shown in the middle section, the switching elements SW1 and SW2 of the synchronous rectifier 44C function as current switching units and do not supply power to the load device 45. Therefore, if the two switching elements SW1 and SW2 of the synchronous rectifier 44C are simultaneously turned on during either the positive or negative half-cycle of the alternating current via the FF control unit 71, then during that period ( Figure 4 Within the middle section and interval (Pb, Pd), the current does not flow to the load device 45 side.

[0032] Figure 9BThe control processing procedure of the synchronous rectifier 44C repeatedly executed by the FF control unit 71 is shown. As shown in the figure, in the above-described processing performed at predetermined time intervals, the FF control unit 71 first determines whether the interval belongs to a given range based on the movement of the alternating current output by the power supply unit 40. Figure 4 The judgment is made on any of the intervals Pa to Pb shown in the bottom segment (step S311). If it belongs to the interval Pa, the switching element SW1 is turned off and the switching element SW2 is turned on (step S321). In this way, the current Ia of the positive half-cycle flows from the diode D1 into the load device 45 and returns to the power unit 40 via the switching element SW2.

[0033] On the other hand, based on the alternating current output by the 40th Electric Power Plant, if its range is... Figure 4 When the lowest segment of the interval Pc is shown, the switching element SW1 is turned on and the switching element SW2 is turned off (step S322). In this way, the current Ic of the negative half-cycle flows from the switching element SW2 into the load device 45 and returns to the power unit 40 via the diode D2.

[0034] Furthermore, based on the alternating current output from the 40th Research Institute of the Ministry of Electric Power, if its range is... Figure 4 If the lowest segment, Pb or Pd, is selected, both the switching elements SW1 and SW2 constituting the current switching unit 75C will be switched on (step S323). In this way, the output current of the power unit 40 is returned to the power unit 40 through the switching elements SW1 and SW2, and is not supplied to the load device 45.

[0035] In the contactless power receiving device 30C of the third embodiment described above, in addition to achieving the same effect as in the first embodiment, the rectifier 44 and the current switching unit 75C can be shared, thus simplifying the device structure. Furthermore, the switching elements SW1 and SW2 can be provided on the upper arm instead of the lower arm. The synchronous rectifier 44C can be configured using switching elements for one or more elements constituting the bridge. In the above case, in order for the synchronous rectifier 44C to function as the current switching unit 75C, it is sufficient to make both elements connected to the lower or upper arm switching elements. Of course, if only the current of half-wave needs to be reduced, then only one switching element can be used as the current switching unit.

[0036] D. Fourth Implementation Method: Figure 10The main structure of the contactless power receiving device 30D according to the fourth embodiment is shown. In other embodiments, the magnitude of the alternating current output by the power unit 40 is measured by the detection unit 70. In contrast, in the fourth embodiment, the input voltage V of the power unit 40 is measured by the voltmeter 32, and the current output flowing from the power unit 40 to the load device 45 is regulated using the measurement result. The output current Iout of the power unit 40 and the input voltage V can be calculated from each other by the reactance L and capacitor C of the current source circuit 331, which serves as a transient filter. That is, the output current Iout and the input voltage V have the following mathematical relationship (1). Iout=V / Z0……(1) Impedance Z0 is obtained based on the reactances L11 to L14 of the four reactors constituting the current source circuit 331 and the capacitance Cim of the transient capacitor Cim, and is obtained by the following mathematical formula (2). Where L = L11 + L12 = L21 + L22

[0037] Therefore, by measuring the input voltage of the power supply unit 40, the output current Iout can be easily obtained. The FF control unit 71 can then perform feedforward control on the ratio that keeps the current switching unit 75C in the on state, and easily control the output current Iout within a specified range. Alternatively, the output current Iout can be obtained and controlled using the aforementioned mathematical formula based on the input voltage V. However, if the on-time ratio mapping diagram Tmp is prepared as a table calculating the ratio of the on-time Ton to the input voltage, the AC power supplied to the load device 45 can be controlled without individual calculations. This embodiment achieves the same effect as the other embodiments described above, which goes without saying.

[0038] E. Fifth implementation method: Next, the contactless power receiving device 30E in the contactless power supply system of the fifth embodiment will be described. The contactless power receiving device 30E of this embodiment is as follows: Figure 11 The contactless power receiving device 30C of the third embodiment (see Figure 9) includes a galvanometer 46 and an FB controller 76. The galvanometer 46 detects the load current Id flowing to the load device 45, and the FB controller 76 performs feedback control. The contactless power receiving device 30E of this embodiment performs the same control as the third embodiment, but the feedback control of the FB controller 76 further reduces the steady-state deviation from the target current value in the current flowing to the load caused by the feedforward control of the FF controller 71.

[0039] Specifically, as shown in the figure, the load current Id flowing to the load device 45 is detected by the ammeter 46, and the deviation between it and the target current Id* is input to the FB control unit 76. The adjustment on-time ΔTon corresponding to this deviation is added to the output of the FF control unit 71. When the load current Id increases and is greater than the target current Id*, the adjustment on-time ΔTon, as the output of the FB control unit 76, increases, resulting in an increase in the on-time Ton of the current switching unit 75. Consequently, when the output current Iout changes, the ratio of the on-time Ton is first adjusted by the feedforward control of the FF control unit 71. When the result of the feedforward control is a deviation from the target current Id* in the load current Id, the feedback control of the FB control unit 76 adds an adjustment on-time ΔTon to adjust the load current Id towards the target current Id*.

[0040] According to the fifth embodiment described above, both high-speed control achieved by feedforward control and high-precision regulation of the target current achieved by feedback control can be simultaneously realized. Furthermore, in this embodiment, the load current Id is controlled by adjusting the on-time Ton, but it can also be done as follows... Figure 12 The off-time Toff (the time obtained by subtracting the on-time Ton from a cycle Tt) of the current switching unit is adjusted as shown in the modified example. In this contactless power receiving device 30e, the adjustment off-time ΔToff corresponding to the deviation between the load current Id and the target current Id* is added to the output of the FF control unit 71e. When the load current Id increases to be greater than the target current Id*, the adjustment off-time ΔToff, which is the output of the FB control unit 76e, is differentially calculated in a way that it decreases. As a result, when the output current Iout changes, the FF control unit 71e first performs feedforward control with reference to the off-time ratio mapping diagram Tmo, thereby adjusting the ratio of the off-time Toff. When the result of the feedforward control is that a deviation from the target current Id* occurs in the load current Id, the adjustment off-time ΔToff is additionally adjusted by the feedback control of the FB control unit 76e to adjust the load current Id toward the target current Id*.

[0041] F. Sixth Implementation Method: The contactless power receiving device 30F of the sixth embodiment, as shown below. Figure 13Similar to the fifth embodiment, in addition to the feedforward control implemented by the FF control unit 71, feedback control is also implemented by the FB control unit 76F, and the on-time Ton is adjusted so that the voltage Vd applied to the load device 45 becomes the target voltage Vd*. The voltage Vd applied to the load device 45 is detected by the voltmeter 47. In this way, by performing feedforward control on the current output to the load device 45 and feedback control on the voltage Vd, interference between the two controls can be avoided and a control system can be constructed. Of course, it also achieves the same effect as the fifth embodiment.

[0042] G. Other implementation methods: (1) As another embodiment of this disclosure, the structure of the contactless power receiving device described below can be adopted. The contactless power receiving device includes: a power receiving unit, which includes a power receiving coil and receives alternating current via magnetic field coupling; a power supply unit, which is connected to the power receiving unit and supplies power to the load as a current source; a detection unit, which detects the electrical characteristics of the power supply unit as the current source; a current switching unit, which switches the power supply unit between a first state supplying a first current to the load and a second state supplying a second current smaller than the first current to the load; and a control unit, which determines the ratio of the first state or the second state to the period of the alternating current based on the detected electrical characteristics, and performs feedforward control on the current switching unit according to the ratio. Thus, the ratio of the first state or the second state to the alternating current period can be controlled by feedforward control based on the detected electrical characteristics, thereby enabling high-speed control of the power supply to the load. In the above-described contactless power receiving device, the power supply unit serves as the current source; therefore, the current switching unit can easily switch the current supply between the first current and the second current. In addition, the feedforward control of the proportion of the first state or the second state in the AC cycle can be performed by both the positive half-wave and the negative half-wave in the full wave of the AC cycle, or by only one of them.

[0043] The second current only needs to be smaller than the first current, or it can be zero. To set the second current to a value greater than zero, the following can be done. In the first embodiment, when the contact of the current switching unit 75C is closed, the power lines P1-P2 are short-circuited. However, if a current smaller than the short-circuit current flows through a predetermined impedance to the power lines P1-P2 instead of short-circuiting, the differential current can be supplied to the load. In any case, since the range of the current supplied to the load is from the second current to the first current, the magnitudes of the first and second currents can be determined according to the control range required by the load. In the first to sixth embodiments described above, the ratio of the second state to the alternating current cycle is used as the ratio, and the on-time Ton is used as the object of feedforward control. However, for example, if the current supplied to the load increases or decreases according to the electrical characteristics of the current source, control can be performed to decrease or increase the ratio of the first state, or to increase or decrease the ratio of the second state. Both are equivalent. Furthermore, the power unit can have other states besides the first and second states. For example... The second current in the second state is not zero; in addition, there is a third state where the current is zero. The current switching unit can switch between these three states. The current switching unit only needs to be able to switch between at least the first state, which supplies a first current to the load, and the second state, which supplies a second current to the load that is smaller than the first current. It can also switch to the third state at the same time.

[0044] (2) Based on the structure described in (1) above, the power supply unit may also include a circuit with transient characteristics as the current source. This makes it easy to construct a current source. As the circuit with transient characteristics, in addition to the T-LCL type consisting of four reactors L11 to L22 and capacitor Cim exemplified in the first to sixth embodiments, π-CLC type and T-LCLC type transient filters can also be used. Furthermore, besides using a circuit with transient characteristics, a structure using an inverter, etc., can also be employed.

[0045] (3) Based on the structure of (1) or (2) above, the detection unit employs a current detection circuit that detects the electrical characteristics by means of the output current of a circuit having the transient characteristics. This allows for easy switching of the current switching unit. The output current can be either an actual value or a peak value. Of course, as long as the detected electrical characteristic of the power unit as a current source is an electrical characteristic other than the output current, it can also be any electrical characteristic, as long as it can be used to control the current flowing to the load. For example, if a circuit with transient characteristics is used as the current source, it can also be the input voltage of the power unit, which is equivalent to the output current.

[0046] (4) Based on the structures described in (1) to (3) above, the control unit prepares a correspondence between the electrical characteristics and the ratio in advance, and performs feedforward control based on the ratio determined using the detected electrical characteristics and the correspondence. Thus, the ratio of the first state to the alternating current cycle can be controlled according to the prepared correspondence and the detected electrical characteristics, making it easy to achieve control corresponding to the controlled object. It is not limited to controlling the ratio based on the difference between the controlled object and the target value, as in feedback control. Depending on the state of the controlled object, the ratio can be converted to be larger or gradually decreased, etc., to achieve various types of control.

[0047] (5) Based on the structures described in (1) to (4) above, when the electrical characteristic changes beyond a predetermined value, the control unit may increase the change in the ratio of the first state or the second state of the determined ratio by a predetermined amount. Thus, when the electrical characteristic changes significantly, the change in the ratio is increased, thereby expecting a faster response. The amount of increase can be determined experimentally beforehand or learned using the results of feedforward control. Furthermore, such large changes in electrical characteristics sometimes occur, for example, when the receiving coil of a non-contact receiving device changes from a state coupled to the magnetic field of a transmitting coil of one transmitting device to a state coupled to the magnetic field of multiple transmitting coils, or vice versa. Alternatively, they may occur when the distance between the receiving coil and the transmitting coil changes drastically due to layer differences, etc.

[0048] (6) Based on the structures described in (1) to (5) above, when the current supplied to the load increases, the control unit can adjust the change in the ratio to below a predetermined rate. In this way, the increase in current can be set to below a predetermined rate, thereby suppressing or preventing overcharging when the load is a battery or the like, or suppressing EMC deterioration.

[0049] (7) Based on the structures described in (1) to (6) above, a rectifier may also be included to rectify the output of the power unit, and power may be supplied to the load via the rectified DC power obtained by the rectifier. This is easy to implement when the load is a DC-operated device. Of course, when the load is an AC-operated device, a structure without a rectifier may be used. The rectifier may be either half-wave or full-wave rectifier. Furthermore, it may be implemented using a diode bridge or a synchronous rectifier structure.

[0050] (8) Based on the structures described in (1) to (7) above, the current switching unit can also set the second current supplied to the load to zero by short-circuiting the output line from the power supply unit. In this way, the range of current supplied to the load, i.e., the dynamic range, can be maximized. In addition, the circuit structure can be simplified.

[0051] (9) Based on the structures described in (1) to (8) above, a bridge-type synchronous rectifier that rectifies the output of the power unit may also be included. The current switching unit achieves a short circuit of the output line by simultaneously turning on two switching elements of the synchronous rectifier that are connected to one side of the power line connected to the load. In this way, a part of the rectifier structure and a part of the current switching unit structure can be shared, simplifying the circuit structure. Alternatively, in the bridge-type rectifier, only one switching element may be used, with the others constructed from diodes, and the switching element may be turned on and the output line short-circuited during only one half-wave cycle constituting the full wave.

[0052] (10) Based on the structures described in (1) to (9) above, the circuit in the power supply unit that has the transient characteristics can also be a transient filter, and the detection unit can be a voltage detection circuit that detects the input voltage of the transient filter as the electrical characteristic. In this way, since the object of detection is voltage, the structure of the detection unit can be simplified. In the transient filter, the output current and input voltage are interchangeable, and the output current can be easily obtained from the input voltage. Of course, the control unit can also directly perform the aforementioned feedforward control using the input voltage of the transient filter in the power supply unit.

[0053] (11) Based on the structures described in (1) to (10) above, it may also include: a load current detection unit that detects the load current output to the load; and a feedback control unit that performs feedback control on the stability deviation from the target current value generated in the load current due to the feedforward control. In this way, the stability deviation from the target current value generated in the load current due to the feedforward control can be reduced through feedback control. In addition, such feedback control can be performed on either the proportion of the first state or the second state that is the object of control in the feedforward control, or on the second state or the first state that is opposite to the object of the feedforward control.

[0054] (12) Based on the structures described in (1) to (11) above, the load may also include a rechargeable battery, and the contactless power receiving device may further include: an output voltage detection unit that detects the output voltage of the power unit; and a feedback control unit that uses the detected output voltage and a target voltage for charging the battery to perform feedback control on the ratio. Thus, by controlling the current supplied to the load in the feedforward control and controlling the output voltage when charging the battery as the load in the feedback control, interference between the feedforward control and the feedback control is less likely to occur.

[0055] (13) This disclosure includes a structure as a contactless power supply system. The contactless power supply system includes: a contactless power receiving device of any one of (1) to (12) above; and a power supply device, the power supply device including a power supply coil coupled to the magnetic field of the power receiving coil. Thus, control of the power supply to the load in the contactless power receiving device can be achieved at high speed, and the controllability of the contactless power supply system can be improved. In the above case, there can be one power supply device, but multiple power supply devices can also be provided, and the power supply coil of the power supply device coupled to the magnetic field of the power receiving coil of the power receiving device switches as the equipment on which the power receiving device is installed moves. The power supply coil only needs to be positioned where it can be coupled to the magnetic field of the power receiving coil; for example, when the power receiving device is installed on a moving body, it can be positioned on a road surface, ground, or wall surface.

[0056] (14) This disclosure includes a structure as a non-contact power receiving method corresponding to the structures described in (1) to (12) above. The non-contact power receiving method supplies at least a portion of the alternating current received by the receiving coil at a location capable of coupling with the magnetic field of the transmitting coil from a circuit functioning as a current source to the load. It detects the electrical characteristics of the circuit acting as the current source and switches between a first state supplying a first current to the load and a second state supplying a second current smaller than the first current. Furthermore, it performs feedforward control on the ratio of the first state or the second state to one cycle of the alternating current based on the detected electrical characteristics. Thus, by controlling the ratio of the first state or the second state to the alternating current cycle through feedforward control based on the detected electrical characteristics, control of the power supply to the load can be achieved at high speed.

[0057] (15) This disclosure includes a structure as a contactless power supply method. The contactless power supply method may also apply an alternating voltage of a predetermined frequency to a transmitting coil located at a position capable of coupling with the magnetic field of a receiving coil, supplying at least a portion of the alternating current received by the receiving coil at the position capable of coupling with the magnetic field of the transmitting coil from a circuit functioning as a current source to a load, detecting the electrical characteristics of the circuit acting as the current source, switching between a first state supplying a first current from the current source to the load and a second state supplying a second current smaller than the first current, and performing feedforward control on the ratio of the first state or the second state to one cycle of the alternating current based on the detected electrical characteristics. Thus, a contactless power supply method can be implemented that enables high-speed control of the power supply to a load receiving power in a contactless manner, achieving high controllability.

[0058] The control unit and methods described in this disclosure can also be implemented using a dedicated computer, which is provided by comprising a processor and memory, the processor being programmed to perform one or more functions embodied in the computer program. Alternatively, the control unit and methods described in this disclosure can be implemented using a dedicated computer, which is provided by comprising a processor composed of one or more dedicated hardware logic circuits. Alternatively, the control unit and methods described in this disclosure can be implemented using one or more dedicated computers, which are constituted by a combination of a processor and memory programmed to perform one or more functions and a processor composed of one or more hardware logic circuits. Furthermore, the computer program can also be stored on a computer-readable non-transitory tangible recording medium as instructions to be executed by the computer. "Computer-readable non-transitory tangible recording medium" is not limited to portable recording media such as floppy disks or CD-ROMs, but also includes internal storage devices within the computer such as various RAMs or ROMs, and external storage devices fixed to the computer such as hard disks. That is, "computer-readable non-transitory tangible recording medium" has a broad meaning that includes any recording medium capable of fixing data packets rather than making them temporary.

[0059] This disclosure is not limited to the embodiments described above, and can be implemented through various structures without departing from the above-described spirit. For example, the technical features in the embodiments corresponding to the technical features in the various methods described in the summary section can be appropriately replaced or combined to solve part or all of the above-described technical problems, or to achieve part or all of the above-described effects. Furthermore, the above-described technical features can be appropriately deleted as long as they are not described as essential structures in this specification.

Claims

1. A contactless power receiving device (30, 30B to 30E, 30e, 30F), comprising: The power receiving part (33) includes a power receiving coil (31) and receives alternating current through magnetic field coupling; The power supply unit (40) is connected to the power receiving unit and supplies power to the load as a current source (331, 332, 333); The detection unit (70) detects the electrical characteristics of the power unit as the current source; A current switching unit (75, 75C) switches the power supply unit between a first state supplying a first current to the load and a second state supplying a second current smaller than the first current to the load; and The control unit (71, 71e) determines the ratio of the first state or the second state to the cycle of the alternating current based on the detected electrical characteristics, and performs feedforward control on the current switching unit according to the ratio.

2. The non-contact power receiving device as described in claim 1, characterized in that, The power unit includes a circuit with transient characteristics to serve as the current source.

3. The non-contact power receiving device as described in claim 2, characterized in that, The detection unit is a current detection circuit that detects the electrical characteristics by means of the output current of a circuit having the transient characteristics.

4. The non-contact power receiving device as described in any one of claims 1 to 3, characterized in that, The control unit prepares the correspondence between the electrical characteristics and the ratio in advance. The feedforward control is performed based on the proportion determined using the detected electrical characteristics and the corresponding relationship.

5. The non-contact power receiving device as described in any one of claims 1 to 3, characterized in that, When the electrical characteristic changes by more than a predetermined value, the control unit increases the change in the ratio of the first state or the second state in the determined ratio by a predetermined amount.

6. The non-contact power receiving device as described in any one of claims 1 to 3, characterized in that, When the current supplied to the load is increased, the control unit adjusts the change in the ratio to below a predetermined rate.

7. The non-contact power receiving device as described in any one of claims 1 to 3, characterized in that, It includes rectifiers (44, 44C) that rectify the output of the power unit, and supplies power to the load through the rectified DC power obtained by the rectifiers.

8. The non-contact power receiving device as described in any one of claims 1 to 3, characterized in that, The current switching unit sets the second current supplied to the load to zero by short-circuiting the output lines (P1, P2) from the power unit.

9. The non-contact power receiving device as described in claim 8, characterized in that, This includes a bridge-type synchronous rectifier (44C) that rectifies the output of the power unit. The current switching unit achieves a short circuit in the output line by simultaneously turning on two switching elements (SW1, SW2) of the synchronous rectifier that are connected to one side of the power line to the load.

10. The non-contact power receiving device as described in claim 2 or 3, characterized in that, The circuit in the power department that exhibits the aforementioned transient characteristics is a transient filter. The detection unit is a voltage detection circuit (32) that detects the input voltage of the transient filter as the electrical characteristic.

11. The non-contact power receiving device as described in any one of claims 1 to 3, characterized in that, include: The load current detection unit (46) detects the load current output to the load. as well as The feedback control unit performs feedback control on the stable deviation from the target current value generated in the load current due to the feedforward control.

12. The non-contact power receiving device as described in any one of claims 1 to 3, characterized in that, The load includes a rechargeable battery. The contactless power receiving device also includes: Output voltage detection unit (47), which detects the output voltage of the power unit; and The feedback control unit (76, 76e, 76F) uses the detected output voltage and the target voltage for charging the battery to perform feedback control on the ratio.

13. A contactless power supply system (100), comprising: The non-contact power receiving device as described in any one of claims 1 to 3; as well as A power transmission device (50) includes a power transmission coil (51) coupled to the magnetic field of the receiving coil.

14. A non-contact power receiving method, At least a portion of the alternating current received by the receiving coil at a location capable of coupling with the magnetic field of the transmitting coil is supplied to the load from the circuit, which functions as a current source. The electrical characteristics of the circuit that serves as the current source are detected. The system switches between a first state, in which a first current is supplied from the current source to the load, and a second state, in which a second current smaller than the first current is supplied, and feedforward control is performed on the ratio of the first state or the second state to one cycle of the alternating current based on the detected electrical characteristics.

15. A non-contact power supply method, An alternating voltage of a specified frequency is applied to a transmitting coil located at a position capable of coupling with the magnetic field of the receiving coil. At least a portion of the alternating current received by the receiving coil at a location capable of coupling with the magnetic field of the transmitting coil is supplied to the load from the circuit, which functions as a current source. The electrical characteristics of the circuit that serves as the current source are detected. The system switches between a first state, in which a first current is supplied from the current source to the load, and a second state, in which a second current smaller than the first current is supplied, and feedforward control is performed on the ratio of the first state or the second state to one cycle of the alternating current based on the detected electrical characteristics.

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