CONTROL DEVICE, CONTROL METHOD, PROGRAM, AND NON-CONTACT POWER TRANSMISSION SYSTEM

Abstract

To provide a control device for a power reception device capable of preventing the occurrence of overshooting when suppressing reception power by PWM control in a non-contact power transmission system.SOLUTION: The control device is configured to execute a suppression process to suppress the power received by PWM control in accordance with the magnitude of the power received. The suppression process includes the steps for calculating a power increase allowance, which is the difference between received power when no suppressing is performed and the maximum value of received power for a change in duty cycle, starting the PWM control when the current reception power plus the power increase allowance exceeds the upper limit of the power received minus a predetermined margin, and increasing the duty cycle until the received power becomes equal to or less than the received power when not performing suppression when starting the PWM control.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present disclosure relates to a control device, a control method, and a program for control of a power receiving device that wirelessly receives power from a power transmitting device, and also to a contactless power transfer system that wirelessly transfers power from a power transmitting device to a power receiving device. [Background technology]

[0002] In recent years, a contactless power transfer system that transfers power from a power transmitting device to a power receiving device in a contactless manner has been proposed. In order to protect the power receiving device from an overvoltage caused by an excessively large received power, a technology for suppressing the received power by switching control has been devised.

[0003] Patent document 1 discloses a wireless power receiving device including a receiving side resonant circuit having a receiving coil that receives power wirelessly (contactlessly) from the transmitting side and a receiving side resonant capacitor connected to the receiving coil, a rectifier circuit that rectifies the power received by the receiving coil and outputs it to a load, a receiving side voltage detection unit that detects the output voltage of the rectifier circuit, a switching element connected between the output unit of the receiving side resonant circuit and the output unit of the rectifier circuit and a short circuit having a rectifier element inserted between the output unit of the receiving side resonant circuit and the switching element, and a control circuit that operates the switching element when the output voltage value detected by the receiving side voltage detection unit exceeds a preset reference voltage value. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6361818 Summary of the Invention [Problem to be solved by the invention]

[0005] It is conceivable to adopt PWM control as a switching control for suppressing the received power. PWM control has the advantage that it can be implemented with a simple configuration and can easily adjust the received power by changing the duty. However, when PWM control is adopted, when the received power is suppressed by increasing the duty, there is in principle a region (hereinafter also referred to as a "power increase region") in which the received power becomes larger with respect to the change in the duty than the received power when suppression is not performed. For this reason, when an attempt is made to suppress the received power, there is a risk that the received power will suddenly increase and exceed the rated upper limit. In turn, there is a risk that the power receiving device cannot be properly protected.

[0006] In view of the above-mentioned problems, one object of the present disclosure is to provide a technique capable of suppressing the occurrence of overshoot when suppressing received power by PWM control. [Means for solving the problem]

[0007] The first disclosure relates to a control device for a power receiving device that receives electric power from a power transmitting device in a wireless manner.

[0008] The control device according to the first disclosure is configured to execute a suppression process that suppresses the received power by PWM control according to the magnitude of the received power. The suppression process includes calculating a power increase amount that is a difference between the received power when suppression is not performed and the maximum value of the received power with respect to the change in duty, starting PWM control when the value obtained by adding the power increase amount to the current received power exceeds a value obtained by subtracting a predetermined margin from the upper limit of the received power, and increasing the duty when the PWM control is started until the received power becomes equal to or less than the received power when suppression is not performed.

[0009] The second disclosure relates to a control device having the following characteristics in addition to the control device according to the first disclosure.

[0010] The suppression process further includes, when the received power becomes greater than the received power when suppression is not performed, not reducing the duty until the value obtained by adding the current received power plus the power increase allowance falls below a value obtained by subtracting a specified margin from the upper limit of the received power, and reducing the duty to zero when the value obtained by adding the current received power plus the power increase allowance falls below a value obtained by subtracting a specified margin from the upper limit of the received power.

[0011] The third disclosure relates to a control device further having the following features in addition to the control device according to the first or second disclosure.

[0012] The control device according to the third disclosure includes a memory that stores information on the change characteristics of the received power with respect to the change in the duty. In the suppression process, calculating the power increase amount includes estimating a coupling coefficient between the power transmitting device and the power receiving device from the current received power, and calculating the power increase amount from the coupling coefficient and the change characteristics of the received power.

[0013] The fourth disclosure relates to a control device further having the following features in addition to the control device according to the third disclosure.

[0014] The control device according to the fourth disclosure is configured to further execute a process of acquiring specification information and identification information for identifying a power transmission device that is predicted to receive power, and a process of identifying a power transmission device that will receive power based on the identification information before starting power reception. The suppression process further includes calculating a change characteristic based on the specification information for the identified power transmission device.

[0015] The fifth disclosure relates to a control method for a power receiving device that receives power from a power transmitting device in a wireless manner.

[0016] The control method according to the fifth disclosure includes suppressing the received power by PWM control according to the magnitude of the received power. Also, suppressing the received power by PWM control according to the magnitude of the received power includes calculating a power increase amount that is a difference between the received power when suppression is not performed and the maximum value of the received power with respect to a change in duty, starting PWM control when the value obtained by adding the power increase amount to the current received power exceeds a value obtained by subtracting a predetermined margin from the upper limit of the received power, and increasing the duty when the PWM control is started until the received power becomes equal to or less than the received power when suppression is not performed.

[0017] The sixth disclosure relates to a control method further having the following characteristics in addition to the control method according to the fifth disclosure.

[0018] Suppressing the received power by PWM control according to the magnitude of the received power further includes, when the received power becomes greater than the received power when suppression is not performed, not reducing the duty until the value obtained by adding the current received power plus a power increase allowance falls below a value obtained by subtracting a predetermined margin from the upper limit of the received power, and reducing the duty to zero when the value obtained by adding the current received power plus a power increase allowance falls below a value obtained by subtracting a predetermined margin from the upper limit of the received power.

[0019] The seventh disclosure relates to a program for controlling a power receiving device that receives power from a power transmitting device in a wireless manner.

[0020] The program according to the seventh disclosure is configured to cause a computer to execute a suppression process that suppresses the received power by PWM control according to the magnitude of the received power. The suppression process includes calculating a power increase amount that is a difference between the received power when suppression is not performed and the maximum value of the received power with respect to a change in duty, starting PWM control when the value obtained by adding the power increase amount to the current received power exceeds a value obtained by subtracting a predetermined margin from the upper limit of the received power, and increasing the duty when the PWM control is started until the received power becomes equal to or less than the received power when suppression is not performed.

[0021] The eighth disclosure relates to a program further having the following characteristics with respect to the program according to the seventh disclosure.

[0022] The suppression process further includes, when the received power becomes greater than the received power when suppression is not performed, not reducing the duty until the value obtained by adding the current received power plus the power increase allowance falls below a value obtained by subtracting a specified margin from the upper limit of the received power, and reducing the duty to zero when the value obtained by adding the current received power plus the power increase allowance falls below a value obtained by subtracting a specified margin from the upper limit of the received power.

[0023] The ninth disclosure relates to a contactless power transfer system.

[0024] A contactless power transmission system according to a ninth disclosure includes a power receiving device, a power transmitting device that contactlessly transmits power to the power receiving device, at least one processor, and a memory coupled to the at least one processor and storing a plurality of executable instructions. Here, the plurality of executable instructions are configured to cause the at least one processor to execute a suppression process that suppresses the received power by PWM control according to the magnitude of the received power. The suppression process also includes calculating a power increase amount that is a difference between the received power when suppression is not performed and the maximum value of the received power with respect to a change in duty, starting PWM control when a value obtained by adding the power increase amount to the current received power exceeds a value obtained by subtracting a predetermined margin from the upper limit of the received power, and increasing the duty when the PWM control is started until the received power is equal to or less than the received power when suppression is not performed.

[0025] The tenth disclosure relates to a contactless power transfer system further having the following features in addition to the contactless power transfer system according to the ninth disclosure.

[0026] The suppression process further includes, when the received power becomes greater than the received power when suppression is not performed, not reducing the duty until the value obtained by adding the current received power plus the power increase allowance falls below a value obtained by subtracting a specified margin from the upper limit of the received power, and reducing the duty to zero when the value obtained by adding the current received power plus the power increase allowance falls below a value obtained by subtracting a specified margin from the upper limit of the received power. Effect of the Invention

[0027] According to the present disclosure, when the current received power plus the power increase exceeds the upper limit of the received power minus a predetermined margin, PWM control is started. Also, when PWM control is started, the duty is increased until the received power passes the region where it is equal to or lower than the received power when suppression is not performed. This makes it possible to suppress the occurrence of overshoot when starting PWM control.

[0028] Furthermore, according to the present disclosure, when the received power becomes greater than the received power when suppression is not performed, the duty is not reduced until the value obtained by adding the current received power plus the power increase amount falls below the value obtained by subtracting a predetermined margin from the upper limit of the received power. Also, when the value obtained by adding the current received power plus the power increase amount falls below the value obtained by subtracting a predetermined margin from the upper limit of the received power, the duty is reduced to zero. This makes it possible to suppress the occurrence of overshoot when attempting to end PWM control. [Brief description of the drawings]

[0029] [Figure 1] 1 is a circuit diagram showing a configuration example of a contactless power transfer system according to an embodiment of the present invention. [Diagram 2] 1 is a graph showing an example of a voltage applied to an active rectifier when PWM control is adopted as switching control. [Diagram 3] 1 is a conceptual diagram showing a case where a contactless power transfer system is applied to a charging system for charging a battery provided in a vehicle while the vehicle is traveling. [Figure 4]11 is a graph showing an example of change characteristics of received power when the duty is changed by PWM control. [Diagram 5] 4 is a conceptual diagram showing an example when the power reception control device executes a process for calculating a change characteristic of the received power in the case shown in FIG. 3. FIG. [Figure 6] 5 is a flowchart showing a process executed when the power receiving control device according to the present embodiment starts PWM control. [Figure 7] 5 is a flowchart showing a process executed by the power receiving control device according to the present embodiment while the power receiving control device is performing PWM control. [Figure 8] 6 is a graph showing an example of a suppression process performed by a power receiving control device according to the present embodiment. [Figure 9] 1 is a block diagram showing a schematic configuration of a power receiving control device according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] Hereinafter, the embodiments of the present disclosure will be described with reference to the drawings. However, when the number, quantity, amount, range, etc. of each element is mentioned in the embodiments shown below, the idea of ​​the present disclosure is not limited to the mentioned number unless it is specifically stated or the number is clearly specified in principle. Furthermore, the configurations etc. described in the embodiments shown below are not necessarily essential to the idea of ​​the present disclosure unless it is specifically stated or the number is clearly specified in principle. In addition, the same reference numerals are attached to the same or corresponding parts in each drawing, and the duplicated explanation is appropriately simplified or omitted.

[0031] 1. Contactless power transfer system This embodiment relates to a contactless power transfer system that transfers power from a power transmitting device to a power receiving device in a contactless manner. Fig. 1 is a circuit diagram showing a configuration example of the contactless power transfer system according to this embodiment. Fig. 1 shows a case where the contactless power transfer system is applied to a charging system that charges a battery 2 with power supplied by a DC power source 1. That is, the DC power source 1 supplies power to a power transmitting device 110, and the power is transmitted from the power transmitting device 110 to a power receiving device 210 in a contactless manner. Then, the battery 2 is charged with the power received by the power receiving device 210.

[0032] The DC power source 1 and the power transmitting device 110 are typically placed on the ground, a floor, a wall, or the like. The power receiving device 210 and the battery 2 are typically mounted on a mobile object to be charged, such as a mobile terminal or a vehicle. The battery 2 is typically a rechargeable secondary battery, such as a lithium ion battery or a nickel metal hydride battery.

[0033] 1, a power transmitting coil 116 included in a power transmitting device 110 and a power receiving coil 216 included in a power receiving device 210 are magnetically resonated with each other, so that power is transmitted from the power transmitting coil 116 to the power receiving coil 216. That is, power is transmitted by a magnetic field resonance method.

[0034] The power transmitting device 110 includes a smoothing capacitor 111, an inverter 112, an immittance filter 114, and a power transmitting circuit 115. Here, the inverter 112, the immittance filter 114, and the power transmitting circuit 115 are configured to be connected in cascade.

[0035] The inverter 112 converts the DC power into AC power of a predetermined frequency and outputs the AC power. The output power of the inverter 112 is supplied to the power transmission circuit 115 via the immittance filter 114.

[0036] The inverter 112 is configured with a single-phase full-bridge circuit including a switching device 113. The inverter 112 is also connected to the power transmission control device 100. The power transmission control device 100 is a control device that performs switching control of the switching device 113 based on information acquired from a detection device 120 (e.g., an ammeter or a voltmeter). This controls the frequency and magnitude of the output power of the inverter 112. In turn, the transmission power of the power transmission device 110 is controlled. In particular, the frequency of the output power of the inverter 112 is adjusted to be equal to the resonant frequency of the power transmission circuit 115. In this sense, the resonant frequency of the power transmission circuit 115 can also be called the "drive frequency." Note that the information acquired by the power transmission device 110 from the detection device 120 includes at least the output current and output voltage of the inverter 112.

[0037] The immittance filter 114 reduces electromagnetic noise in the output power of the inverter 112. The immittance filter 114 is composed of a coil and a capacitor, and functions as a low-pass filter. It also adjusts the impedance of the power transmitting device 110.

[0038] The power transmitting circuit 115 is a resonant circuit configured with a power transmitting coil 116 and a resonant capacitor 117. When power of a resonant frequency is supplied from the inverter 112 to the power transmitting circuit 115, the power transmitting coil 116 magnetically resonates with the power receiving coil 216. As a result, power is transmitted from the power transmitting coil 116 to the power receiving coil 216.

[0039] The power receiving device 210 includes a smoothing capacitor 211, an active rectifier 212, an immittance filter 214, and a power receiving circuit 215. Here, the active rectifier 212, the immittance filter 214, and the power receiving circuit 215 are each configured to be connected in cascade.

[0040] The power receiving circuit 215 is a resonant circuit configured with a power receiving coil 216 and a resonant capacitor 217. The resonant frequency of the power receiving circuit 215 is configured to be equal to the resonant frequency of the power transmitting circuit 115. The power receiving coil 216 resonates with the power transmitting coil 116 in a magnetic field, and receives the power transmitted from the power transmitting coil 116.

[0041] The immittance filter 214 reduces electromagnetic noise in the power received by the power receiving circuit 215. The immittance filter 214 is made up of a coil and a capacitor, and functions as a low-pass filter. It also adjusts the impedance of the power receiving device 210.

[0042] The active rectifier 212 converts the power received by the power receiving circuit 215 into DC power and outputs it. The output power of the active rectifier 212 is supplied to the battery 2 via the smoothing capacitor 211. In other words, the output power of the active rectifier 212 becomes the received power of the power receiving device 210.

[0043] The active rectifier 212 is configured by a single-phase full-wave rectifier circuit including a switching device 213. The active rectifier 212 is also connected to the power receiving control device 200. The power receiving control device 200 is a control device that performs switching control of the switching device 213 based on information acquired from the detection device 220. This controls the output power of the active rectifier 212 (the received power of the power receiving device 210).

[0044] More specifically, the power receiving control device 200 temporarily forms a short circuit in the active rectifier 212 by switching on and off the switching device 213. When the short circuit is formed, the output power of the active rectifier 212 is hardly supplied to the battery 2. Therefore, by temporarily forming a short circuit by switching control, it is possible to suppress the output power of the active rectifier 212 (the received power of the power receiving device 210). Since a short circuit is temporarily formed, suppression of the received power in the power receiving device 210 can also be said to mean that the power receiving device 210 is in a "short circuit mode." Hereinafter, the process in which the power receiving control device 200 suppresses the received power by switching control is referred to as a "suppression process."

[0045] The restriction process is executed for the purpose of protecting the power receiving device 210 and the battery 2 so that the received power does not exceed the upper limit determined by the ratings of the power receiving device 210 and the battery 2.

[0046] In particular, the power receiving control device 200 employs PWM control as the switching control for the suppression process. That is, the duty of the PWM control corresponds to the period during which a short circuit is formed. FIG. 2 is a graph showing an example of the voltage applied to the active rectifier 212 when PWM control is employed as the switching control. FIG. 2 shows a graph (dashed line) when the suppression process is not performed, and a graph (solid line) when the suppression process by PWM control is performed. In this way, when the suppression process by PWM control is performed, by increasing the duty, the period during which a short circuit is formed increases, and the suppression of the received power can be further strengthened.

[0047] As described above, the contactless power transfer system according to the present embodiment is configured. In the contactless power transfer system shown in Fig. 1, the power transmitting device 110 is supplied with power from a DC power source 1, but may be configured to be supplied with power from an AC power source. In this case, a converter is provided at the input stage of the power transmitting device 110, so that the system can be configured in the same way as in Fig. 1.

[0048] The contactless power transmission system according to the present embodiment may include a plurality of power transmission devices 110 or a plurality of power receiving devices 210. For example, a case where the contactless power transmission system is applied to a charging system in which a battery 2 provided in a vehicle is charged while the vehicle is traveling is considered. FIG. 3 shows an example of a case where the contactless power transmission system is applied to a charging system in which a vehicle 3 is charged while traveling. In the example shown in FIG. 3, when the vehicle 3 passes a plurality of power transmission devices 110 arranged in a line on a traveling path, the power receiving device 210 provided in the vehicle 3 receives power in a contactless manner, thereby charging the battery 2. Although two power transmission devices 110 are illustrated in FIG. 3, more power transmission devices 110 may be arranged over a longer distance. In this case, considering that a plurality of similar vehicles 3 may exist, the contactless power transmission system includes a plurality of power receiving devices 210.

[0049] Incidentally, when the power receiving control device 200 executes suppression processing by PWM control, an area (power increase area) where the received power is larger than the received power when suppression is not performed with respect to the change in duty is present in principle, because the apparent impedance of the power receiving device 210 seen from the power transmitting device 110 changes. FIG. 4 is a graph showing the change characteristics of the received power when the duty is changed for each of three cases (large (solid line), medium (dashed line), and small (dotted and dashed line)) with different coupling coefficients. As shown in FIG. 4, the change characteristics of the received power draw different curves when the coupling coefficient is different, but a power increase area 10 exists in each case. FIG. 4 also shows the power increase amount, which is the difference between the received power when the duty is zero (when suppression is not performed) and the maximum value of the received power with respect to the change in duty (shown by a circle), for each curve with different coupling coefficients.

[0050] Because the power increase region 10 exists as described above, when suppression processing is performed by PWM control, there is a risk of an overshoot occurring in which the received power increases rapidly and exceeds the upper limit. In particular, there are situations in which an overshoot may occur when PWM control is about to be started and when PWM control is about to be ended. For example, if PWM control is started and the duty is increased because the received power approaches the upper limit, the received power increases in the power increase region 10, and an overshoot may occur. Also, if the duty is reduced to zero in an attempt to end PWM control because the received power has started to decrease, there is a risk of an overshoot occurring because the suppression of the received power is excessively released in response to the decrease in the received power.

[0051] Frequent occurrence of overshoot can cause deterioration or failure of the power receiving device 210 and the battery 2. For this reason, it is necessary to suppress the occurrence of overshoot. In the contactless power transfer system according to this embodiment, the suppression process executed by the power receiving control device 200 is characterized in order to suppress the occurrence of overshoot. In particular, the power receiving control device 200 according to this embodiment is characterized in the process executed when starting PWM control and the process executed while PWM control is being performed in the suppression process. The characteristic process executed by the power receiving control device 200 according to this embodiment will be described below.

[0052] 2. Suppression processing The power reception control device 200 according to this embodiment manages in advance the change characteristic of the received power with respect to the change in duty as shown in Fig. 4 for the power transmission device 110 that receives power. The change characteristic of the received power as shown in Fig. 4 is determined from the circuit information of the power transmission device 110 and the power receiving device 210. Here, examples of the circuit information include the circuit configuration, the drive frequency, the inductance of the power transmission coil 116 and the power receiving coil 216, the resistance value, the capacitance of the capacitor, the power supply voltage, and the like. In other words, the change characteristic of the received power can be uniquely determined for the pair of the power transmission device 110 and the power receiving device 210. For example, the power reception control device 200 stores map information as shown in Fig. 4 in advance in a memory.

[0053] Incidentally, when a contactless power transmission system includes a plurality of power transmitting devices 110 or a plurality of power receiving devices 210, it is assumed that the change characteristic of the received power differs depending on the pair of the power transmitting device 110 and the power receiving device 210. For this reason, the power reception control device 200 according to the present embodiment may be further configured to execute the following process in order to acquire the change characteristic of the received power for the power transmitting device 110 that receives power.

[0054] First, the power reception control device 200 executes a process of acquiring specification information and information (identification information) for identifying the power transmission device 110 for the power transmission device 110 that is predicted to receive power. Here, the specification information includes circuit information of the power transmission device 110. The identification information is, for example, location information or area information where the power transmission device 110 is fixed, or ID information of the power transmission device 110. The power reception control device 200 manages the acquired specification information and identification information in association with each other. Note that the information may be acquired at a location where the power transmission device 110 and the power receiving device 210 are separated from each other by, for example, wide area communication or the like.

[0055] Next, the power reception control device 200 executes a process of identifying the power transmission device 110 that will receive power based on the identification information acquired before starting power reception. For example, when acquiring position information as the identification information, the power reception device 210 is located near one of the power transmission devices 110, and therefore identifies the power transmission device 110 that will receive power.

[0056] Then, the power receiving control device 200 calculates the change characteristic of the received power based on the specification information of the identified power transmitting device 110. This can be done, for example, by referring to the specification information corresponding to the identification information of the identified power transmitting device 110 and calculating from the specification information of the power transmitting device 110 and the specification information of the power receiving device 210.

[0057] FIG. 5 is a conceptual diagram showing an example of the power reception control device 200 performing the above-described process in the case shown in FIG. 3. In the example shown in FIG. 5, the power reception control device 200 performs wide-area communication with the power transmission control device 100 of the power transmission device 110 arranged in an area where the vehicle is predicted to travel (for example, predicted from the travel plan of the vehicle 3), and acquires area information including the position of the power transmission device 110 as identification information and circuit information of the power transmission device 110 arranged in the area as specification information. Here, examples of wide-area communication include LTE and 4G. Next, the power reception control device 200 travels while acquiring GPS position information at any time, and identifies the power transmission device 110 that receives power from the GPS position information and the area information. This makes it possible to acquire circuit information of the power transmission device 110 that receives power. Then, the power reception control device 200 calculates the change characteristic of the received power for the power transmission device 110 that receives power, and starts power reception.

[0058] By the power receiving control device 200 executing the processing in this manner, even when the contactless power transmission system includes multiple power transmitting devices 110 or multiple power receiving devices 210, the change characteristics of the received power for the power transmitting device 110 receiving the power can be managed in advance before the power reception begins.

[0059] 2-1.Processing to be performed when starting PWM control First, a process executed when the power receiving control device 200 according to this embodiment starts PWM control will be described. Fig. 6 is a flowchart showing a process executed when the power receiving control device 200 according to this embodiment starts PWM control. The flowchart shown in Fig. 6 is executed at a predetermined processing cycle when PWM control has not been started (restriction of received power is not being performed). In the following description, it is assumed that the power receiving control device 200 has previously managed the change characteristics of received power with respect to changes in duty for the power transmitting device 110 that receives power.

[0060] In step S100, the power receiving control device 200 acquires the current received power of the power receiving device 210. For example, the received power of the power receiving device 210 is acquired from the detection device 220. Alternatively, the power receiving control device 200 may be configured to calculate the received power from the output current and output voltage of the power receiving device 210 acquired from the detection device 220.

[0061] After step S100, the process proceeds to step S110.

[0062] In step S110, the power reception control device 200 calculates the power increase amount from the change characteristic of the received power. When the change characteristic of the received power is given by map information or the like, if the coupling coefficient between the power transmission device 110 and the power receiving device 210 is determined, the power increase amount can be calculated. Here, if attention is paid to the fact that PWM control has not yet started (duty is zero), the coupling coefficient can be estimated from the received power acquired in step S100, as shown in the example of FIG. 4. In this way, the power increase amount can be calculated from the change characteristic of the received power managed in advance by estimating the coupling coefficient from the received power acquired in step S100.

[0063] After step S110, the process proceeds to step S120.

[0064] In step S120, the power receiving control device 200 determines whether the sum of the received power acquired in step S100 and the power increase amount calculated in step S110 exceeds the upper limit of the received power minus a predetermined margin. Here, it is preferable that the predetermined margin is provided sufficiently for the observation error of the received power.

[0065] If the value obtained by adding the power increase allowance to the received power does not exceed the upper limit minus the margin (step S120; No), the power receiving control device 200 does not start PWM control in this process, and returns to step S100 to repeat the process.

[0066] If the value added with the received power exceeds the upper limit minus the margin (step S120; Yes), the power receiving control device 200 starts PWM control (step S130). Then, when the PWM control is started, the duty is increased until the received power passes through the power increase region 10 (to a region where the received power is equal to or lower than the received power when suppression is not performed) (step S140). After the process according to the flowchart shown in FIG. 6 is completed, the power receiving control device 200 performs PWM control according to the magnitude of the received power. For example, the duty of the PWM control is given by feedback control according to the magnitude of the received power.

[0067] As described above, when the power receiving control device 200 according to the present embodiment starts PWM control, it increases the duty until the received power passes the power increase region 10. As a result, after starting PWM control, it is possible to perform PWM control in a region where the received power is equal to or lower than the received power when suppression is not performed. In particular, the power receiving control device 200 according to the present embodiment starts PWM control when the value obtained by adding the current received power to the power increase amount exceeds the value obtained by subtracting a predetermined margin from the upper limit of the received power. As a result, it is possible to suppress the occurrence of overshoot while increasing the duty. In this way, according to the power receiving control device 200 according to the present embodiment, it is possible to suppress the occurrence of overshoot when starting PWM control. In addition, the power receiving control device 200 according to the present embodiment realizes a control method for the power receiving device 210 corresponding to the flowchart shown in FIG. 6. Furthermore, the control method corresponding to the flowchart shown in FIG. 6 can also be applied to a program for controlling the power receiving device 210.

[0068] 2-2.Processing to be performed during PWM control Next, a process executed by the power receiving control device 200 according to the present embodiment while the power receiving control device 200 is performing PWM control will be described. Fig. 7 is a flowchart showing a process executed by the power receiving control device 200 according to the present embodiment while the power receiving control device 200 is performing PWM control. The flowchart shown in Fig. 7 is executed at a predetermined processing cycle while the power receiving control device 200 is performing PWM control.

[0069] In step S200, the power receiving control device 200 acquires the current received power of the power receiving device 210.

[0070] After step S200, the process proceeds to step S210.

[0071] In step S210, the power receiving control device 200 judges whether the received power acquired in step S200 is greater than the received power when suppression is not performed. This can be judged from the coordinate position of the pair of the current duty value and the received power value based on the change characteristic of the received power that is managed in advance (see the power increase region 10 shown in FIG. 4).

[0072] When the received power is not larger than the received power when no restriction is performed (step S210; No), the power receiving control device 200 continues to perform PWM control (normal operation) according to the magnitude of the received power (step S220).

[0073] When the received power becomes greater than the received power without the restriction (step S210; Yes), the process proceeds to step S230.

[0074] In step S230, the power receiving control device 200 calculates the power increase amount from the change characteristic of the received power. If we focus on the point in time when the received power becomes larger than the received power when suppression is not performed, the received power is on the boundary line of the power increase region 10 in the change characteristic. Therefore, as shown in the example of Fig. 4, it is possible to estimate the coupling coefficient from the received power acquired in step S200. As a result, it is possible to calculate the power increase amount.

[0075] After step S230, the process proceeds to step S240.

[0076] In step S240, the power receiving control device 200 judges whether or not the value obtained by adding the power increase amount calculated in step S220 to the received power acquired in step S200 falls below the value obtained by subtracting a predetermined margin from the upper limit of the received power. Here, it is preferable that the predetermined margin is sufficiently provided for the observation error of the received power. In particular, it may be equivalent to the margin in the process executed when starting the PWM control.

[0077] If the value obtained by adding the power increase allowance to the received power is not below the value obtained by subtracting the margin from the upper limit (step S240; No), the power receiving control device 200 performs PWM control so as not to reduce the duty in the current process. In other words, when the flowchart shown in Fig. 7 is executed at every predetermined processing cycle, the power receiving control device 200 performs PWM control so as not to reduce the duty until the value obtained by adding the power increase allowance to the received power falls below the value obtained by subtracting the margin from the upper limit when the received power is greater than the received power without suppression.

[0078] If the value obtained by adding the power increase allowance to the received power falls below the value obtained by subtracting the margin from the upper limit (step S240; Yes), the power receiving control device 200 reduces the duty to zero and ends the PWM control. After step S260 is executed, the repeated execution of the process of the flowchart shown in Fig. 7 ends. After the PWM control is started again, the power receiving control device 200 resumes the repeated execution of the flowchart shown in Fig. 7.

[0079] As described above, when the received power becomes greater than the received power when the suppression is not performed, the power receiving control device 200 according to the present embodiment performs PWM control so as not to reduce the duty until the value obtained by adding the current received power to the power increase amount falls below the value obtained by subtracting a predetermined margin from the upper limit of the received power. In addition, when the value obtained by adding the current received power to the power increase amount falls below the value obtained by subtracting a predetermined margin from the upper limit of the received power, the duty is reduced to zero and the PWM control is terminated. This makes it possible to suppress the occurrence of overshoot while the duty is being reduced. In this way, the power receiving control device 200 according to the present embodiment makes it possible to suppress the occurrence of overshoot when attempting to terminate the PWM control. In addition, the power receiving control device 200 according to the present embodiment realizes a control method for the power receiving device 210 corresponding to the flowchart shown in FIG. 7. Furthermore, the control method corresponding to the flowchart shown in FIG. 7 can also be applied to a program for controlling the power receiving device 210.

[0080] 2-3.Example An example of the suppression process by the power receiving control device 200 according to this embodiment will be described below. Fig. 8 is a graph showing an example of the suppression process by the power receiving control device 200 according to this embodiment. Fig. 8 shows a graph of the received power of the power receiving device 210 and a graph of the duty of the PWM control by the power receiving control device 200, with the time axis corresponding to each other. Fig. 8 also shows an example in which the power receiving device 210 approaches the fixed power transmitting device 110 and then moves away from the power receiving device 110.

[0081] 8, the power receiving device 210 starts receiving power (power transmission starts) at time t0. For example, this is when the power receiving device 210 approaches above the power transmitting device 110. Between time t0 and time t1, the received power is sufficiently small compared to the upper limit, and the power receiving control device 200 does not start PWM control (duty 0).

[0082] At time t1, when the value of the received power plus the power increase exceeds the upper limit minus the margin, the power receiving control device 200 starts PWM control. Then, the duty is increased until the received power passes through the power increase region 10. In the embodiment shown in Fig. 8, the duty is increased until time t2. Here, it can be seen that the occurrence of overshoot is suppressed at the start of PWM control.

[0083] Between time t2 and time t3, the power receiving control device 200 performs PWM control according to the received power. Here, the power receiving control device 200 can perform PWM control in a region where the received power is equal to or lower than the received power when suppression is not performed. In addition, efficient received power can be achieved by PWM control without causing overshoot. Note that in the power receiving control device 200 according to this embodiment, when PWM control is started, the duty is increased until the received power exceeds the power increase region 10, so it is expected that the duty will maintain a constant value for a while after the start of PWM control (for a while after time t2).

[0084] At time t3, the received power becomes greater than the received power when no restriction is performed, so the power receiving control device 200 performs PWM control so as not to reduce the duty.

[0085] At time t4, when the value obtained by adding the power increase amount to the received power falls below the upper limit minus the margin, the power receiving control device 200 reduces the duty to zero and ends the PWM control. In the example shown in Fig. 8, the duty becomes zero at time t5. Here, it can be seen that the occurrence of overshoot is suppressed at the end of the PWM control.

[0086] 3. Configuration of the power receiving control device Hereinafter, the configuration of the power receiving control device 200 according to this embodiment will be described with reference to FIG. 9. FIG. 9 is a block diagram showing a schematic configuration of the power receiving control device 200 according to this embodiment. The power receiving control device 200 is a computer including a memory 201, a processor 205, and a communication device 206. The memory 201 is coupled to the processor 205, and stores a plurality of executable instructions 204 and data 202 required for executing processing. Here, the instructions 204 are provided by a program 203. In this sense, the memory 201 can also be called a "program memory." The data 202 stored in the memory 201 includes information on the change characteristics of the received power.

[0087] The communication device 206 is a device that transmits and receives information to and from a device external to the power reception control device 200. Examples of the communication device 206 include a device that performs wide-area communication with the power transmission control device 100 or the power transmission device 110, a GPS receiver, and the like. Examples of information received by the communication device 206 include the received power of the power receiving device 210, specification information and identification information of the power receiving device 210, GPS location information, and the like. Furthermore, map information that gives the change characteristic of the received power may be acquired via the communication device 206. The information received by the communication device 206 is stored in the memory 201 as data 202.

[0088] The instructions 204 are configured to cause the processor 205 to execute the suppression process, in particular, the process shown in Figures 6 and 7. That is, the processor 205 operates according to the instructions 204, thereby realizing the execution of the process shown in Figures 6 and 7 based on the data 202.

[0089] 4.Effects As described above, according to this embodiment, when the value obtained by adding the current received power to the power increase allowance exceeds the value obtained by subtracting a predetermined margin from the upper limit of the received power, PWM control is started. Furthermore, when the PWM control is started, the duty is increased until the received power passes the power increase region 10 (to the region where the received power is equal to or less than the received power when suppression is not performed). Furthermore, when the received power becomes greater than the received power when suppression is not performed while the PWM control is being performed, the duty is not decreased until the value obtained by adding the current received power to the power increase allowance falls below the value obtained by subtracting a predetermined margin from the upper limit of the received power. Furthermore, when the value obtained by adding the current received power to the power increase allowance falls below the value obtained by subtracting a predetermined margin from the upper limit of the received power, the duty is decreased to zero and the PWM control is terminated. This makes it possible to suppress the occurrence of overshoot in the suppression process by PWM control. In addition, it is possible to reduce the risk of deterioration and failure of the power receiving device 210 and the battery 2.

[0090] In this embodiment, the magnetic field resonance type contactless power transfer system has been described, but the present invention can also be applied to other types of contactless power transfer systems such as an electromagnetic induction type. [Explanation of symbols]

[0091] 10 Power Increase Area 100 Power transmission control device 110 Power transmission equipment 200 Power receiving control device 201 Memory 204 Instructions 205 Processor 210 Power receiving device

Claims

1. A control device for a power receiving device that wirelessly receives power from a power transmitting device, The power receiving device is configured to execute a suppression process for suppressing the received power by PWM control according to the magnitude of the received power, The suppression process includes: Calculating a power increase amount that is a difference between the received power when no suppression is performed and a maximum value of the received power with respect to a change in duty; starting the PWM control when a value obtained by adding the current received power to the power increase amount exceeds a value obtained by subtracting a predetermined margin from an upper limit of the received power; When the PWM control is started, the duty is increased to a region where the received power is equal to or less than the received power when the suppression is not performed; Includes A control device comprising:

2. The control device according to claim 1 , The suppression process includes: When the received power becomes greater than the received power when the suppression is not performed, the duty is not reduced until a value obtained by adding the current received power to the power increase amount falls below a value obtained by subtracting the margin from the upper limit. reducing the duty to zero when the current received power plus the power increase amount falls below the upper limit minus the margin; Also includes A control device comprising:

3. The control device according to claim 1 or 2, a memory for storing information on a change characteristic of the received power with respect to a change in the duty; In the suppression process, calculating the power increase amount includes estimating a coupling coefficient between the power transmitting device and the power receiving device from the current received power; calculating the power increase amount from the coupling coefficient and the change characteristic; Includes A control device comprising:

4. The control device according to claim 3, A process of acquiring specification information and identification information for identifying the power transmitting device, the power transmitting device being predicted to receive power; A process of identifying the power transmitting device that receives power based on the identification information before starting power reception; and further configured to execute: The suppression process further includes calculating the change characteristic based on the specification information about the identified power transmitting device. A control device comprising:

5. A control method for a power receiving device that wirelessly receives power from a power transmitting device, comprising: suppressing the received power by PWM control in accordance with the magnitude of the received power; The suppression of the received power by the PWM control includes: Calculating a power increase amount that is a difference between the received power when no suppression is performed and a maximum value of the received power with respect to a change in duty; starting the PWM control when a value obtained by adding the current received power to the power increase amount exceeds a value obtained by subtracting a predetermined margin from an upper limit of the received power; When the PWM control is started, the duty is increased to a region where the received power is equal to or less than the received power when the suppression is not performed; Includes A control method comprising:

6. 6. The control method according to claim 5, The suppression of the received power by the PWM control includes: When the received power becomes greater than the received power when the suppression is not performed, the duty is not reduced until a value obtained by adding the current received power to the power increase amount falls below a value obtained by subtracting the margin from the upper limit. reducing the duty to zero when the current received power plus the power increase amount falls below the upper limit minus the margin; Also includes A control method comprising:

7. A program for controlling a power receiving device that wirelessly receives power from a power transmitting device, The power receiving device is configured to cause a computer to execute a suppression process for suppressing the received power by PWM control according to the magnitude of the received power, The suppression process includes: Calculating a power increase amount that is a difference between the received power when no suppression is performed and a maximum value of the received power with respect to a change in duty; starting the PWM control when a value obtained by adding the current received power to the power increase amount exceeds a value obtained by subtracting a predetermined margin from an upper limit of the received power; When the PWM control is started, the duty is increased to a region where the received power is equal to or less than the received power when the suppression is not performed; Includes A program characterized by:

8. The program according to claim 7, The suppression process includes: When the received power becomes greater than the received power when the suppression is not performed, the duty is not reduced until a value obtained by adding the current received power to the power increase amount falls below a value obtained by subtracting the margin from the upper limit. reducing the duty to zero when the current received power plus the power increase amount falls below the upper limit minus the margin; Also includes A program characterized by:

9. A power receiving device; A power transmitting device that transmits electric power to the power receiving device in a wireless manner; At least one processor; a memory coupled to the at least one processor and storing a plurality of executable instructions; Including, The plurality of executable instructions are configured to cause the at least one processor to execute a suppression process for suppressing the received power by PWM control in accordance with a magnitude of the received power; The suppression process includes: Calculating a power increase amount that is a difference between the received power when no suppression is performed and a maximum value of the received power with respect to a change in duty; starting the PWM control when a value obtained by adding the current received power to the power increase amount exceeds a value obtained by subtracting a predetermined margin from an upper limit of the received power; When the PWM control is started, the duty is increased to a region where the received power is equal to or less than the received power when the suppression is not performed; Includes A non-contact power transmission system comprising:

10. The contactless power transfer system according to claim 9, The suppression process includes: When the received power becomes greater than the received power when the suppression is not performed, the duty is not reduced until a value obtained by adding the current received power to the power increase amount falls below a value obtained by subtracting the margin from the upper limit. reducing the duty to zero when the current received power plus the power increase amount falls below the upper limit minus the margin; Also includes A non-contact power transmission system comprising:

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