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

Abstract

To increase the speed of control on power supply to a load.SOLUTION: At least a part of AC power received by a power reception coil 31 at a position where magnetic field coupling with a power transmission coil 51 can be achieved, is supplied from a circuit 331 functioning as a current source to a load 45. Here, an electric property of the circuit as a current source is detected, 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 that is smaller than the first current is supplied is performed, and feed-forward control of the ratio of the first or second state with respect to one cycle of AC current is performed in accordance with the detected electric property.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to contactless power reception or power supply. [Background technology]

[0002] When supplying power contactlessly, a technology for controlling the power supply current may be required. For example, Patent Document 1 discloses a method for controlling the power supply current by converting received AC power into DC power using magnetic field coupling and controlling the current flowing through a capacitor on the output side to which this DC voltage is applied, according to the current flowing through the load. In this case, the period during which the current flowing through the capacitor is zero is controlled to supply power at the desired current amount. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. WO2020 / 129178 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in Patent Document 1, the control of the period during which the current is set to zero is performed by feedback control, which can result in insufficient control response. For example, if the amount of power transmitted from the power transmitting side increases suddenly, the control on the power receiving device side cannot keep up, which can result in excessive received power or deterioration of EMC during transients. If the received power becomes excessive, there is a risk of overcurrent being generated in the battery, etc., which poses a problem of requiring additional configuration to prevent these. [Means for solving the problem]

[0005] The present disclosure can be realized in the following forms or application examples.

[0006] [1] A contactless power receiving device (30, 30B to 30E, 30e, 30F) of the present disclosure includes a power receiving unit (33) having a power receiving coil (31) and receiving AC power by magnetic field coupling, a power unit (40) connected to the power receiving unit and supplying power to a load as a current source (331, 332, 333), a detection unit (70) detecting electrical characteristics of the power unit as the current source, a current switching unit (75, 75C) switching the power unit between a first state in which a first current is supplied to the load and a second state in which a second current smaller than the first current is supplied to the load, and a control unit (71, 71e) determining a ratio of the first state or the second state with respect to a period of the AC power according to the detected electrical characteristics and feedforward controlling the current switching unit according to the ratio.

[0007] [2] Furthermore, the contactless power receiving method disclosed herein supplies at least a portion of the AC power received by a receiving coil at a position where it can be magnetically coupled with the transmitting coil to a load from a circuit that functions as a current source, detects the electrical characteristics of the circuit as a current source, 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 controls the proportion of the first state or the second state per one cycle of the AC power according to the detected electrical characteristics.

[0008] [3] Furthermore, the contactless power supply method disclosed herein applies an AC voltage of a predetermined frequency to a transmitting coil located at a position where it can be magnetically coupled with the receiving coil, supplies at least a portion of the AC power received by the receiving coil at a position where it can be magnetically coupled with the transmitting coil to a load from a circuit functioning as a current source, detects electrical characteristics of the circuit as a current source, 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 controls the proportion of the first state or the second state per one cycle of the AC power according to the detected electrical characteristics. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic configuration diagram showing a contactless power supply system according to an embodiment; [Figure 2] 1 is a schematic diagram illustrating the configuration of a power transmitting device and a power receiving device that configure a contactless power supply system. [Figure 3] FIG. 2 is an explanatory diagram showing several configuration examples of a power supply unit. [Figure 4] FIG. 4 is an explanatory diagram showing the relationship between the operating state of a current switching unit and the state of a load current. [Figure 5] FIG. 1 is a configuration diagram showing a first embodiment of a power receiving device. [Figure 6A] FIG. 10 is an explanatory diagram showing the difference in on-time depending on whether the current switching unit is on or off. [Figure 6B] FIG. 2 is a schematic diagram showing the relationship between the on-time, the output current, and the load current. [Figure 7] FIG. 10 is an explanatory diagram showing the behavior of the load current under feedforward control when the receiving current increases. [Figure 8A] FIG. 10 is a configuration diagram showing an embodiment of a power receiving device used in the second embodiment. [Figure 8B] FIG. 10 is an explanatory diagram showing an example of control in which the feedforward control amount is increased when the receiving current increases suddenly. [Figure 9A] FIG. 10 is a configuration diagram showing a power receiving device used in a third embodiment. [Figure 9B] 10 is a flowchart showing a control process of a synchronous rectifier in the third embodiment. [Figure 10] FIG. 10 is a configuration diagram showing a power receiving device used in a fourth embodiment. [Figure 11] FIG. 13 is a configuration diagram showing a power receiving device used in a fifth embodiment. [Figure 12] FIG. 13 is a configuration diagram showing a modified example of the fifth embodiment. [Figure 13] FIG. 13 is a configuration diagram showing a power receiving device used in a sixth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] A. First embodiment: (A1) Overall configuration of the wireless power transfer system: 1 shows a schematic configuration of a contactless power supply system 100 including a contactless power receiving device 30 according to a first embodiment. As shown in the figure, the contactless power supply system 100 includes a plurality of power transmission devices 50 buried in the ground beneath a road surface SF, and a contactless power receiving device 30 mounted on a mobile object 20 that moves on the road surface SF. The mobile object 20 includes driving wheels 21 driven by a motor (not shown) included in a load device 45, driven wheels 22 that support the mobile object 20 together with the driving wheels 21 so that the mobile object 20 can move on the road surface SF, and a power receiving coil 31 disposed under the floor of the mobile object 20. The power receiving coil 31 is magnetically coupled to a power transmission coil 51 of a power transmission device 50 provided on the road surface SF side to receive AC power and supply the power to the load device 45. The power transmitting device 50 and the contactless power supply system 100 including the power transmitting device 50 are not limited to those that supply power to the contactless power receiving device 30 of the mobile object 20, and the power receiving device may be a device or system that transmits or supplies power to a non-mobile object, such as a mobile terminal, as long as it is a device or system that transmits or supplies power contactlessly. The mobile object 20 is not limited to those that travel on outdoor roads, but also includes transport vehicles used indoors, such as in factories and hospitals. The mobile object 20 may have any number of wheels, and may move by means other than wheels, such as magnetic levitation.

[0011] The power transmission device 50 can be buried under the road surface SF, or can be installed on the road surface, a wall, or a ceiling. In such cases, the contactless power receiving device 30 can be placed at a predetermined position 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 contactless power receiving device 30 can be placed on the side of the mobile body 20. Furthermore, the contactless power receiving device 30 can be moved within the mobile body 20 according to the installation location of the power transmission device 50, or multiple contactless power receiving devices 30 can be prepared in advance and used by switching between them.

[0012] In this embodiment, the multiple power transmission devices 50 that supply power to the non-contact power receiving devices 30 of the mobile object 20 each have the same configuration and are arranged along the movement path of the mobile object 20. Of course, the power transmission devices 50 are not limited to being arranged along the movement path of the mobile object 20, but may also be arranged two-dimensionally on the road surface SF. Each power transmission device 50 is connected to a common main power line RFP. High-frequency AC power with a frequency f1 (e.g., 85 kHz) is supplied to the main power line RFP from a main power supply device 60. In this embodiment, each power transmission device 50 has the same configuration, but the configurations do not have to be identical as long as power transmission is possible, for example, by alternately arranging power transmission coils 51 of different sizes. Of course, there may be only one power transmission device 50.

[0013] Main power supply device 60 receives a low-frequency (e.g., 60 Hz) AC supply from main power supply 65 and converts it into high-frequency AC. Main power supply device 60 is known to have a configuration including, from the side receiving power from main power supply 65, a noise filter for AC output, a PFC circuit, an inverter, and a filter. The power supplied from main power supply 65 is converted into AC of the above frequency by the inverter and output to main power line RFP.

[0014] The schematic configuration of the power transmitting device 50 and the non-contact power receiving device 30 is shown in Fig. 2. The figure shows a state in which one of the multiple power transmitting devices 50 is transmitting power to the non-contact power receiving device 30 of the mobile object 20. At this time, the power transmitting coil 51 of the power transmitting device 50 is magnetically coupled with the power receiving coil 31 of the non-contact power receiving device 30, and when power is transmitted from the power transmitting device 50, an induced current (AC) flows in the power receiving coil 31. The non-contact power receiving device 30 includes a power receiving unit 33, a detection unit 70, a power unit 40, a current switching unit 75, and an FF control unit 71, and supplies the necessary power to the load device 45. The power receiving unit 33 receives power from the power transmitting device 50 side by the induced current generated in the power receiving coil 31. The power unit 40 includes a circuit configuration that functions as a current source and further includes a rectifier 44 that rectifies the AC power received by the power receiving unit 33. The rectifier 44 may be a full-wave rectifier using a diode bridge, a half-wave rectifier, or a synchronous rectifier that uses a switching element as part of the bridge and performs rectification by turning the switching element on and off in synchronization with the alternation of the input AC.

[0015] The detection unit 70 detects the electrical characteristics of the circuit functioning as a current source for the power unit 40. In this embodiment, it detects the current value Iout output from the circuit functioning as a current source. The configuration of the circuit functioning as a current source will be described in detail later, but due to the circuit configuration, it is also possible to detect a voltage value equivalent to the current value as the electrical characteristic. The current switching unit 75 switches between a first state in which a first current is supplied to the load and a second state in which a second current smaller than the first current is supplied to the load. The specific configuration of the current switching unit 75 will also be described in detail later. The FF control unit 71 controls the switching of the current switching unit 75 between the first state and the second state. The FF control unit 71 is configured as a control device performing feedforward control. Feedforward control controls the current value Id flowing through the controlled object, in this case the load device 45, to approach a target value I*. Generally, feedback control is used to bring a controlled variable closer to a target value. In feedback control, the output current value Iout from the input side, here the power receiving unit 33, is controlled according to the difference between the target value and the controlled variable. In contrast, the FF control unit 71 of this embodiment controls the current switching unit 75 according to the value of the output current value Iout, prior to a change in the load current value Id for the load device 45. Details of this control will be summarized later. Note that the FF control unit 71 can be realized by a discrete circuit configuration, but can also easily be realized by arithmetic and logic operations by a computer executing a program stored in memory.

[0016] Configuration examples of each component constituting the contactless power receiving device 30 will be described in order. FIG. 3 illustrates several configuration examples of the power receiving unit 33 and the power unit 40. In the illustrated configuration examples, the power unit 40 functions as a current source and incorporates a current source circuit 331 having immittance characteristics, here an immittance filter. In configuration example 1, the power receiving unit 33 includes a power receiving coil 31 and two resonant capacitors Ct1 and Ct2 connected to both sides of the power receiving coil 31. The current source circuit 331, which serves as an immittance filter, is provided downstream of the power receiving unit 33. The immittance filter in configuration example 1 has a T-LCL configuration and includes one immittance capacitor Cim and two pairs of reactors L11 and L12 and reactors L21 and L22 connected to both sides of the immittance capacitor Cim. Naturally, immittance filters other than the T-LCL type can also be used, such as π-CLC and T-LCLC types.

[0017] In configuration example 1, a current switching unit 75 is provided in the subsequent stage of a current source circuit 331 that uses an immittance filter, and a rectifier 44 is further connected to the output side of the current source circuit 331. In configuration example 1, the rectifier 44 is configured as a full-wave rectifier consisting of four bridge-connected diodes D1 to D4. The AC current output from the current source circuit 331 is converted to DC by the rectifier 44 and supplied to a load device 45 to charge, for example, a battery included in the load device 45. The current switching unit 75 is configured as a contact that short-circuits 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] An immittance filter functioning as a current source circuit may include all of the reactors L11 to L22 that make up the circuit internally, as in Configuration Example 1, or may be configured without reactors L11 and L12 on the side connected to power receiving unit 33, as in Configuration Example 2. This current source circuit 332 also functions in the same way as Configuration Example 1. Furthermore, as in Configuration Example 3, a circuit configuration consisting of power transmitting coil 51 and resonant capacitors Ct1 and Ct2, and power receiving coil 31 and resonant capacitors Ci1 and Ci2 may be used as current source circuit 333 having immittance characteristics. This current source circuit 333 also functions in the same way as Configuration Examples 1 and 2.

[0019] FIG. 4 shows how power supplied from an AC current source such as current source circuit 331 is supplied as DC to load device 45. When current switching unit 75 is off, current supply from current source circuit 331 causes current to flow to load device 45 as indicated by dashed line Ia in the figure when power line P1 is positive (positive half cycle). On the other hand, current supply from current source circuit 331 causes current to flow to load device 45 as indicated by dashed line Ic in the figure when power line P2 is positive (negative half cycle). Furthermore, when current switching unit 75 is on, power lines P1 and P2 are short-circuited, and the current supplied by current source circuit 331 flows through current switching unit 75 as indicated by dashed lines Ib and Id in the figure, but does not flow to rectifier 44. Naturally, therefore, no current is supplied to load device 45 either.

[0020] When current switching unit 75 is switched on and off within a half cycle of the alternating current of current source circuit 331, as shown in the bottom row of FIG. 4, one cycle of the alternating current is punctured by first states Pa and Pc in which power is supplied to load device 45 via rectifier 44, and second states Pb and Pd in ​​which power is not supplied. The power supplied to load device 45 increases or decreases depending on the proportion of the first state section within one cycle of the alternating current. The first state sections Pa and Pc and the second state sections Pb and Pd are equivalent to the first state time and the second state time on the time axis. By controlling the proportion of the first state section time Ton to one cycle Tt of the alternating current, the amount of power supplied to load device 45, specifically the amount of current supplied to load device 45, can be controlled.

[0021] Therefore, as shown in an example in FIG. 5, this embodiment employs a configuration in which a detection unit 70 is provided that detects the output current Iout of the current source circuit 331, and an FF control unit 71 performs feedforward control of the on / off of the current switching unit 75 based on this output current Iout. When the FF control unit 71 receives the output current Iout from the detection unit 70, it references an on-time ratio map Tmp to obtain the ratio of the on-time Ton at which the current switching unit 75 should be on. The on-time ratio map Tmp stores in advance the ratio of the on-time Ton that should be taken with respect to the output current Iout. Note that the on-time Ton may be obtained using a formula or function instead of a map.

[0022] FIG. 6A shows an example of the ratio of the on-time Ton. The upper part of the figure illustrates a case where one cycle Tt of the alternating current is constant, and the ratio of the time during which the current switching unit 75 is on varies. In this example, Ton = 0 indicates a case where there is no on-time Ton, and Ts, Tm, and Tl indicate a case where the on-time Ton gradually increases from a short state. FIG. 6B also shows the ratio of the on-time Ton to the output current Iout on the right axis, and the load current Id supplied to the load device 45 at this time on the left axis. Because the on-time Ton is 0 and the current switching unit 75 is always kept off until the output current Iout reaches a predetermined value In, the load current Id increases as the amount of power transmitted from the power transmitting device 50 increases and the output current Iout increases.

[0023] When the output current Iout exceeds the predetermined value In, the FF control unit 71 gradually increases the on-time Ton, which is the value of the on-time ratio map Tmp, based on the output current Iout. As a result, as illustrated in the upper part of the figure, the time Ton during which the current switching unit 75 is on increases from 0 to Ts to Tm to Tl. As the on-time Ton increases, the current switching unit 75 turns on, and the intervals Pb and Pd shown in the bottom row of FIG. 4 increase, and the amount of power output to the load device 45 via the rectifier 44 decreases.

[0024] When the contactless power receiving device 30 actually receives contactless power from the power transmitting device 50, the output current Iout output by the power receiving unit 33 may suddenly change due to a change in the positional relationship between the power transmitting coil 51 and the power receiving coil 31. As an example of a sudden change in the output current Iout, a step response is assumed, and control according to this embodiment is shown in FIG.

[0025] Assuming that the current value to be output to load device 45 is 10 A, and output current Iout output from current source circuit 331 changes from 10 A to 20 A at time t, if the on-time Ton of current switching unit 75 is feedback-controlled using load current Id so that load current Id becomes target current I*, 10 A in this case, due to the characteristics of feedback control, it takes a considerable amount of time for load current Id to become target current I*. If the gain of feedback control is increased in an attempt to improve responsiveness, the control becomes unstable, and overshooting and undershooting are likely to occur.

[0026] In contrast, in this embodiment, as shown in FIG. 7, when the output current Iout suddenly increases from 10 A, the on-time Ton is increased to the specified on-time Tm by referring to the on-time ratio map Tmp. As a result, the load current Id quickly returns to the target current I*, 10 A in this case. In this example, since the output current Iout and the on-time Ton are simply proportional to each other, an overshoot occurs in the output current Iout between times t1 and t2 immediately after the output current Iout changes. However, this overshoot quickly disappears, and after time t2, the output current Iout converges to the target current I*. Because the FF control unit 71 obtains the on-time Ton by referring to the on-time ratio map Tmp, there is no need to calculate a difference as in feedback control, and the control variable, in this case the on-time Ton, can be quickly switched.

[0027] B. Second embodiment: The schematic configuration of a contactless power receiving device 30B used in a contactless power supply system of the second embodiment is shown in Fig. 8A. 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 that the on-time Ton used by the FF control unit 71 when the output current Iout increases suddenly is different. The rest is the same as in the first embodiment.

[0028] In the non-contact power receiving device 30B of the second embodiment, when the output current Iout changes beyond a predetermined threshold, the FF control unit 71 calculates the on-time Ton from the on-time ratio map Tmp. Instead of simply setting the on-time Ton to a value proportional to the output current Iout, the FF control unit 71 further increments the on-time Ton, as shown in FIG. 8B . In the illustrated example, from time t1 to t2 immediately after the sudden change in the output current Iout, the on-time Ton is temporarily increased to the on-time Tl. The on-time Ton is then reduced to the on-time Tm, and the rate limiter 73 gradually reduces the on-time Ton at a constant rate. The rate limiter 73 has no effect when the on-time Ton increases, but adjusts the rate of reduction of the on-time Ton so that it does not fall below a predetermined rate.

[0029] This makes it possible to suppress overshoot of the load current Id even when the output current Iout suddenly changes. In the illustrated example, it is easy to prevent the load current Id from exhibiting a behavior in which it suddenly increases temporarily, as indicated by the dashed line. Furthermore, when the on-time Tl is reduced after being increased, the reduction rate is not made excessive, so that the occurrence of overshoot can be sufficiently suppressed. If overshoot does not occur, an overcurrent will not flow to the load device 45 such as a battery, and it is easy to prevent the life of the battery or the like from being shortened due to an overcurrent.

[0030] C. Third embodiment: FIG. 9A shows the configuration of a contactless power receiving device 30C constituting a contactless power transfer system of the third embodiment. The contactless power receiving device 30C of this embodiment differs from the contactless power receiving device 30 of the first embodiment in the configuration of the rectifier. In the third embodiment, the rectifier is configured as a synchronous rectifier 44C, and a part of the rectifier is used as a current switching unit 75C, but the other components are the same as those of the first embodiment. As shown in the figure, the synchronous rectifier 44C forms a bridge with two diodes D1 and D2 on the upper arm and two switching elements SW1 and SW2 on the lower arm. The rectifier is the synchronous rectifier 44C, and during rectification, the switching elements SW1 and SW2 are turned on and off exclusively in accordance with each alternation of the polarity of the alternating current received by the power unit 40. As a result, as shown in the top part of FIG. 4, synchronous rectifier 44C functions as a full-wave rectifier and supplies DC power to load device 45.

[0031] Furthermore, when the FF control unit 71 simultaneously turns on (conducts) the two switching elements SW1 and SW2 that constitute the lower arm connected to the power line P2, these switching elements SW1 and SW2 establish a conductive state between the power lines P1 and P2. In this case, the two switching elements SW1 and SW2 function as a current switching unit. As a result, as shown in the middle of FIG. 4, the switching elements SW1 and SW2 of the synchronous rectifier 44C function as a current switching unit, and no power is supplied to the load device 45. Therefore, if the FF control unit 71 simultaneously turns on the two switching elements SW1 and SW2 of the synchronous rectifier 44C during both the positive and negative half cycles of the alternating current (intervals Pb and Pd in ​​the middle of FIG. 4), no current flows to the load device 45 during that period.

[0032] 9B shows the control processing routine for the synchronous rectifier 44C repeatedly executed by the FF control unit 71. As shown in the figure, in this processing, which is performed at predetermined intervals, the FF control unit 71 first determines whether the section in question belongs to one of sections Pa to Pd shown at the bottom of FIG. 4, based on the behavior of the alternating current output by the power unit 40 (step S311). If the section belongs to section Pa, the FF control unit 71 turns off switching element SW1 and turns on switching element SW2 (step S321). This causes current Ia in the positive half cycle to flow from diode D1 to the load device 45 and return to the power unit 40 via switching element SW2.

[0033] On the other hand, if the behavior of the alternating current output by power unit 40 indicates that the section is section Pc shown in the bottom row of Figure 4, switching element SW1 is turned on and switching element SW2 is turned off (step S322). As a result, current Ic in the negative half cycle flows from switching element SW2 to load device 45 and returns to power unit 40 via diode D2.

[0034] 4, if the behavior of the alternating current output by power unit 40 indicates that the section is section Pb or section Pd shown in the bottom row of FIG. 4, switching elements SW1 and SW2 constituting current switching unit 75C are both turned on (step S323). In this way, the output current of power unit 40 returns to power unit 40 through switching elements SW1 and SW2 and is not supplied to load device 45.

[0035] The contactless power receiving device 30C of the third embodiment described above not only achieves the same effects as the first embodiment, but also functions as both the rectifier 44 and the current switching unit 75C, thereby simplifying the device configuration. The switching elements SW1 and SW2 may be provided in the upper arm instead of the lower arm. The synchronous rectifier 44C may have one or more elements that make up the bridge configured as switching elements. In this case, to enable the synchronous rectifier 44C to also function as the current switching unit 75C, both of the two elements connected to either the lower arm or the upper arm may be switching elements. Of course, if it is sufficient to reduce the current only during a half-wave, only one switching element may be used as the current switching unit.

[0036] D. Fourth embodiment: Fig. 10 shows the main components of the configuration of a contactless power receiving device 30D of the fourth embodiment. While in the other embodiments the magnitude of the alternating current output by the power unit 40 is measured by a detection unit 70, in the fourth embodiment the input side voltage V of the power unit 40 is measured by a voltmeter 32 and used to adjust the current output from the power unit 40 to the load device 45, which is a difference. As shown in the figure, the output current Iout and the input side voltage V of the power unit 40 can be mutually calculated using the reactance L and capacitance C of the current source circuit 331, which is an immittance filter. In other words, the output current Iout and the input voltage V are related by the following equation (1): Iout =V / Z0 … (1) The impedance Z0 is calculated from the reactances L11 to L14 of the four reactors that make up the current source circuit 331 and the capacitance Cim of the immittance capacitor Cim by the following equation (2). Z0=√(L / Cim) … (2) However, L = L11 + L12 = L21 + L22

[0037] Therefore, by measuring the input voltage of the power unit 40, it is easy to determine the output current Iout, and it is easy for the FF control unit 71 to control the output current Iout within a predetermined range by feedforward controlling the proportion of the time that the current switching unit 75C is turned on. Note that while the output current Iout may be determined and controlled from the input voltage V using the above formula, if an on-time proportion map Tmp is prepared as a table for determining the proportion of the on-time Ton relative to the input voltage, it is possible to control the AC power supplied to the load device 45 without having to perform conversions each time. Needless to say, this embodiment also provides the same effects as the other embodiments described above.

[0038] E. Fifth embodiment: Next, a contactless power receiving device 30E in a contactless power supply system of a fifth embodiment will be described. As shown in Fig. 11, the contactless power receiving device 30E of this embodiment includes an ammeter 46 that detects a load current Id flowing through a load device 45 and an FB control unit 76 that performs feedback control in addition to the device configuration of the contactless power receiving device 30C of the third embodiment (see Fig. 9). The contactless power receiving device 30E of this embodiment performs control similar to that of the third embodiment, but further reduces, through feedback control by the FB control unit 76, a steady-state deviation from a target current value that occurs in the current flowing through the load due to feedforward control by the FF control unit 71.

[0039] Specifically, as shown in the figure, the load current Id flowing through the load device 45 is detected by the ammeter 46, and the deviation between this and the target current Id* is input to the FB control unit 76, and an adjusted 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 becomes greater than the target current Id*, the adjusted on-time ΔTon output by the FB control unit 76 increases, thereby increasing the on-time Ton of the current switching unit 75C. As a result, when the output current Iout changes, the FF control unit 71 first adjusts the proportion of the on-time Ton through feedforward control. If this feedforward control causes the load current Id to deviate from the target current Id*, the FB control unit 76 adds the adjusted on-time ΔTon through feedback control in response, and the load current Id is adjusted toward the target current Id*.

[0040] According to the fifth embodiment described above, both high-speed control by feedforward control and highly accurate adjustment to the target current by feedback control can be achieved. In this embodiment, the load current Id is feedback-controlled by adjusting the on-time Ton. However, as shown in a modified example in FIG. 12, the off-time Toff of the current switching unit (the time obtained by subtracting the on-time Ton from one cycle Tt) may be adjusted. In this contactless power receiving device 30e, an adjusted 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 and becomes greater than the target current Id*, a difference is calculated so that the adjusted off-time ΔToff output by the FB control unit 76e decreases. As a result, when the output current Iout changes, the FF control unit 71e first performs feedforward control by referring to the off-time proportion map Tmo, thereby adjusting the proportion of the off-time Toff. If this feedforward control results in a deviation of the load current Id from the target current Id*, an adjusted off time ΔToff is added in response to this deviation through feedback control by the FB control unit 76e, and the load current Id is adjusted toward the target current Id*.

[0041] F. Sixth embodiment: As shown in Fig. 13, the contactless power receiving device 30F in the sixth embodiment performs feedback control by an FB control unit 76F in addition to feedforward control by an FF control unit 71, as in the fifth embodiment. However, the feedback control by the FB control unit 76F is performed to adjust the on-time Ton 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 a voltmeter 47. In this way, by feedforward controlling the current output to the load device 45 and feedback controlling the voltage Vd, it is possible to construct a control system that avoids interference between the two types of control. Naturally, the same effects as those of the fifth embodiment are also achieved.

[0042] G. Other Embodiments: (1) As another embodiment of the present disclosure, the following configuration of a contactless power receiving device can be adopted. This contactless power receiving device includes a power receiving unit including a power receiving coil and receiving AC power through magnetic field coupling; a power unit connected to the power receiving unit and serving as a current source to supply power to a load; a detection unit detecting electrical characteristics of the power unit as the current source; a current switching unit switching the power unit between a first state in which a first current is supplied to the load and a second state in which a second current smaller than the first current is supplied to the load; and a control unit determining a ratio of the first state or the second state to a cycle of the AC power according to the detected electrical characteristics and feedforward-controlling the current switching unit according to the ratio. This allows the ratio of the first state or the second state to a cycle of the AC power to be controlled by feedforward control according to the detected electrical characteristics, thereby enabling high-speed control of power supply to the load. In this contactless power receiving device, the power unit serves as a current source, so the current switching unit can easily switch the current supply between the first current and the second current. The feedforward control of the proportion of the first state or the second state in the AC cycle may be performed on both the positive half wave and the negative half wave of the full wave of the AC cycle, or on only one of them.

[0043] The second current need only be smaller than the first current, and may be zero. The second current can be made greater than zero by the following method. In the first embodiment, the power lines P1 and P2 are short-circuited when the contacts of the current switching unit 75C are turned on. However, instead of short-circuiting, a current smaller than the short-circuit current can be caused to flow between the power lines P1 and P2 via a predetermined impedance, allowing the difference in current to be supplied to the load. In either case, the range of current supplied to the load is between the second current and the first current, so the magnitudes of the first current and the second current can be determined depending on the control range required for the load. In all of the first to sixth embodiments described above, the ratio of the second state to the cycle of the AC power was set as the on-time Ton and subjected to feedforward control. However, if the current supplied to the load needs to be increased or decreased due to the electrical characteristics of the current source, for example, either the ratio of the first state or the ratio of the second state can be increased or decreased. Both are equivalent. The power unit may have other states in addition to the first and second states. For example, the second state may have a third state in which the second current is not zero, and the current switching unit may switch between these three states. The current switching unit is only required to be able to switch between at least the first state in which a first current is supplied to the load and the second state in which a second current smaller than the first current is supplied to the load, and may also switch to the third state.

[0044] (2) In the configuration of (1) above, the power unit may include a circuit having immittance characteristics as the current source. This makes it possible to easily configure a current source. As the circuit having immittance characteristics, in addition to the T-LCL type consisting of four reactors L11 to L22 and a capacitor Cim exemplified in the first to sixth embodiments, it is also possible to use a π-CLC type or T-LCLC type immittance filter. Furthermore, in addition to the circuit having immittance characteristics, it is also possible to adopt a configuration using an inverter.

[0045] (3) In the configurations (1) or (2) above, the detection unit may be a current detection circuit that detects the electrical characteristic from the output current of the circuit having the immittance characteristic. This allows for easy switching of the current switching unit. The output current may be an effective value or a peak value. Of course, what is detected may be anything other than the output current as long as it is an electrical characteristic of the power unit as a current source, and may be anything that can be used to control the current flowing to the load. For example, if a circuit having immittance characteristics is used as a current source, the input voltage of the power unit, which is equivalent to the output current, may be used.

[0046] (4) In the configurations (1) to (3) above, the control unit may prepare a correspondence relationship between the electrical characteristic and the ratio in advance, and perform the feedforward control in accordance with the ratio determined using the correspondence relationship based on the detected electrical characteristic. In this way, the ratio of the first state to the cycle of AC power can be controlled using the detected electrical characteristic in accordance with the prepared correspondence relationship, making it easy to achieve control according to the controlled object. Control of this ratio is not limited to feedback control, which controls this ratio according to the difference between the controlled object and a target value. Various types of control can be achieved, such as gradually increasing or decreasing this ratio depending on the state of the controlled object.

[0047] (5) In the configurations (1) to (4) above, the control unit may increment the change in the ratio of the first state or the second state in the determined ratio by a predetermined amount when the electrical characteristic changes beyond a predetermined value. In this way, the change in the ratio is incremented when the change in the electrical characteristic is large, thereby enabling a faster response. The increment amount may be determined experimentally in advance or may be learned using the results of feedforward control. Note that such a large change in the electrical characteristic may occur, for example, when a power receiving coil of a contactless power receiving device changes from being magnetically coupled with one power transmitting coil of a power transmitting device to being magnetically coupled with multiple power transmitting coils, or vice versa. Alternatively, it may occur when the distance between the power receiving coil and the power transmitting coil suddenly changes due to the presence of a step or the like.

[0048] (6) In the configurations (1) to (5) above, the control unit may adjust the rate of change to a predetermined rate or less when increasing the current supplied to the load. This allows the current increase to be kept at a predetermined rate or less, thereby suppressing or preventing overcharging when the load is a battery or the like, or suppressing deterioration of EMC.

[0049] (7) In the configurations (1) to (6) above, a rectifier may be provided to rectify the output of the power section, and the load may be supplied with power as DC after rectification by the rectifier. This makes it easier to accommodate a load that operates on DC. Of course, if the load is a device that operates on AC, a configuration without a rectifier is also acceptable. The rectifier may be one that performs half-wave rectification or full-wave rectification. It may also be realized by a diode bridge, or a synchronous rectifier configuration may be adopted.

[0050] (8) In the configurations (1) to (7) above, the current switching unit may set the second current supplied to the load to zero by shorting the output line from the power unit. This maximizes the dynamic range of the current supplied to the load. It also simplifies the circuit configuration.

[0051] (9) In the configurations (1) to (8) above, the power supply may include a bridge-type synchronous rectifier that rectifies the output of the power supply unit, and the current switching unit may short-circuit the output line by simultaneously turning on two switching elements of the synchronous rectifier that are connected to one of the power lines to the load. This allows the rectifier and the current switching unit to share a common configuration, simplifying the circuit configuration. Note that the bridge-type rectifier may be configured with only one switching element and the others as diodes, and the switching element may be turned on only during one half-wave period that constitutes a full wave, shorting the output line.

[0052] (10) In the configurations (1) to (9) above, the circuit having the immittance characteristic of the power section may be an immittance filter, and the detection section may be a voltage detection circuit that detects the input voltage of the immittance filter as the electrical characteristic. In this way, since the detection target is voltage, the configuration of the detection section can be simplified. In an immittance filter, the output current and the input voltage are compatible, making it easy to determine the output current from the input voltage. Of course, the control section may directly perform the above-mentioned feedforward control using the input voltage of the immittance filter of the power section.

[0053] (11) The configurations (1) to (10) above may further include a load current detection unit that detects a load current output to the load, and a feedback control unit that feedback-controls a steady-state deviation from a target current value that occurs in the load current due to the feedforward control. In this way, the steady-state deviation from a target current value that occurs in the load current due to the feedforward control can be reduced by the feedback control. Note that such feedback control may be performed on the proportion of the first state or the second state that is the control target of the feedforward control, or may be performed on the second state or the first state that is the opposite of the target of the feedforward control.

[0054] (12) In the configurations (1) to (11) above, the load may include a battery capable of charging power, and may further include an output voltage detection unit that detects the output voltage of the power unit, and a feedback control unit that feedback-controls the ratio using the detected output voltage and a target voltage for charging the battery. In this way, the feedforward control controls the current supplied to the load, and the feedback control controls the output voltage when charging the battery, which is the load, making it possible to reduce interference between the feedforward control and the feedback control.

[0055] (13) The present disclosure includes a configuration as a contactless power transfer system. The contactless power transfer system includes a contactless power receiving device according to any one of (1) to (12) above and a power transmitting device having a power transmitting coil that is magnetically coupled with the power receiving coil. This allows the contactless power receiving device to quickly control the power supply to a load, thereby improving the controllability of the contactless power transfer system. In this case, one power transmitting device may be provided, but multiple power transmitting devices may also be provided so that the power receiving coil of the power receiving device is magnetically coupled with the power transmitting coil of the power transmitting device as the device equipped with the power receiving device moves. The power transmitting coil may be located in a position where it can be magnetically coupled with the power receiving coil. For example, if the power receiving device is mounted on a moving object, it may be located on the road surface, floor, or wall.

[0056] (14) The present disclosure includes a configuration relating to a contactless power receiving method corresponding to the configurations (1) to (12) above. This contactless power receiving method supplies at least a portion of AC power received by a power receiving coil at a position where it can be magnetically coupled with a power transmitting coil from a circuit functioning as a current source to a load, detects electrical characteristics of the circuit as the current source, 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 from the current source to the load, and feedforward controls the proportion of the first state or the second state per one cycle of the AC power according to the detected electrical characteristics. In this way, the proportion of the first state or the second state per AC cycle can be controlled by feedforward control according to the detected electrical characteristics, thereby enabling high-speed control of power supply to the load.

[0057] (15) The present disclosure may include a configuration as a contactless power transfer method. This contactless power transfer method may include applying an AC voltage of a predetermined frequency to a power transmitting coil located at a position where it can be magnetically coupled with a power receiving coil, supplying at least a portion of the AC power received by the power receiving coil located at a position where it can be magnetically coupled with the power transmitting coil from a circuit functioning as a current source to a load, detecting electrical characteristics of the circuit as the current source, 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 from the current source to the load, and feedforward controlling the proportion of the first state or the second state per one cycle of the AC power according to the detected electrical characteristics. This allows for high-speed control of power supply to the load on the power receiving side, thereby achieving a contactless power transfer method with high controllability.

[0058] The control unit and method described herein may be implemented by a special-purpose computer configured with a processor and memory programmed to perform one or more functions embodied in a computer program. Alternatively, the control unit and method described herein may be implemented by a special-purpose computer configured with one or more dedicated hardware logic circuits. Alternatively, the control unit and method described herein may be implemented by one or more special-purpose computers configured with a processor and memory programmed to perform one or more functions in combination with a processor configured with one or more hardware logic circuits. Furthermore, the computer program may be stored as instructions to be executed by a computer on a computer-readable non-transitory storage medium. The term "computer-readable non-transitory storage medium" is not limited to portable storage media such as floppy disks and CD-ROMs, but also includes internal storage devices within a computer, such as various RAMs and ROMs, and external storage devices fixed to a computer, such as a hard disk. In other words, the term "computer-readable non-transitory storage medium" has a broad meaning, including any storage medium capable of non-transitoryly fixing data packets.

[0059] The present disclosure is not limited to the above-described embodiments and can be realized in various configurations without departing from the spirit thereof. For example, the technical features in the embodiments corresponding to the technical features in each aspect described in the Summary of the Invention section can be appropriately replaced or combined to solve some or all of the above-described problems or achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be appropriately deleted. [Explanation of symbols]

[0060] 20...mobile body, 21...drive wheel, 22...driven wheel, 30, 30B, 30C, 30D, 30E, 30F, 30e...contactless power receiving device, 31...receiving coil, 32...voltmeter, 33...receiving unit, 40...power unit, 44...rectifier, 44C...synchronous rectifier, 45...load device, 46...ammeter, 47...voltmeter, 50...power transmitting device, 51...transmitting coil, 60...main power supply device, 65...main power supply, 70...detection unit, 71, 71e...FF control unit, 73...rate limiter, 75, 75C...current switching unit, 76, 76F, 76e...FB control unit, 100...contactless power transfer system, 331, 332, 333...current source circuit, SW1, SW2...switching element, Tmo...off time ratio map, Tmp...on time ratio map

Claims

1. a power receiving unit (33) including a power receiving coil (31) and receiving AC power by magnetic field coupling; a power unit (40) connected to the power receiving unit and serving as a current source (331, 332, 333) to supply power to a load; a detection unit (70) for detecting the electrical characteristics of the power unit as a current source; a current switching unit (75, 75C) for switching the power unit between a first state in which a first current is supplied to the load and a second state in which a second current smaller than the first current is supplied to the load; a control unit (71, 71e) that determines a ratio of the first state or the second state with respect to a cycle of the AC power according to the detected electrical characteristic, and feedforward controls the current switching unit according to the ratio; A contactless power receiving device (30, 30B to 30E, 30e, 30F) comprising:

2. The contactless power receiving device according to claim 1 , wherein the power section includes a circuit having an immittance characteristic as the current source.

3. The contactless power receiving device according to claim 2 , wherein the detection unit is a current detection circuit that detects the electrical characteristic from an output current of a circuit having the immittance characteristic.

4. The control unit A correspondence relationship between the electrical characteristics and the ratio is prepared in advance; performing the feedforward control in accordance with the ratio determined using the correspondence relationship based on the detected electrical characteristics; The contactless power receiving device according to claim 1 .

5. 4. The contactless power receiving device according to claim 1, wherein 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 when the electrical characteristic changes beyond a predetermined value.

6. The contactless power receiving device according to claim 1 , wherein the control unit adjusts the rate of change to be equal to or less than a predetermined rate when increasing the current supplied to the load.

7. 4. The contactless power receiving device according to claim 1, further comprising a rectifier (44, 44C) that rectifies an output of the power unit, and power is supplied to the load using direct current rectified by the rectifier.

8. 4. The contactless power receiving device according to claim 1, wherein the current switching unit short-circuits output lines (P1, P2) from the power unit to set the second current supplied to the load to zero.

9. a bridge-type synchronous rectifier (44C) for rectifying the output of the power section; 9. The contactless power receiving device according to claim 8, wherein the current switching unit realizes a short circuit of the output line by simultaneously turning on two switching elements (SW1, SW2) of the synchronous rectifier connected to one of the power lines to the load.

10. the circuit having the immittance characteristic of the power section is an immittance filter; The detection unit is a voltage detection circuit (32) that detects an input voltage of the immittance filter as the electrical characteristic. The contactless power receiving device according to claim 2 or 3.

11. a load current detection unit (46) for detecting a load current output to the load; a feedback control unit that performs feedback control of a steady-state deviation from a target current value that occurs in the load current due to the feedforward control; The contactless power receiving device according to claim 1 , comprising:

12. The load includes a battery capable of charging power, and an output voltage detection unit (47) for detecting the output voltage of the power unit; a feedback control unit (76, 76e, 76F) that feedback controls the ratio using the detected output voltage and a target voltage for charging the battery; The contactless power receiving device according to claim 1 , comprising:

13. The contactless power receiving device according to any one of claims 1 to 3, a power transmission device (50) including a power transmission coil (51) that is magnetically coupled with the power receiving coil; A contactless power supply system (100) comprising:

14. At least a portion of the AC power received by the power receiving coil at a position where it can be magnetically coupled with the power transmitting coil is supplied to a load from a circuit functioning as a current source; detecting an electrical characteristic of the current source in the circuit; 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, and feedforward controlling a ratio of the first state or the second state to one cycle of the AC power according to the detected electrical characteristic; Contactless power receiving method.

15. Applying an AC voltage of a predetermined frequency to a power transmitting coil located at a position where it can be magnetically coupled with the power receiving coil; At least a portion of the AC power received by the power receiving coil at a position where it can be magnetically coupled with the power transmitting coil is supplied to a load from a circuit functioning as a current source; detecting an electrical characteristic of the current source in the circuit; 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, and feedforward controlling a ratio of the first state or the second state to one cycle of the AC power according to the detected electrical characteristic; Contactless power supply method.

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