Power receiving device and method for estimating received power

Abstract

This power reception apparatus comprises: a main rectification circuit unit that rectifies received power and outputs same to a load; a sub-rectification circuit unit that is connected in parallel with a reception portion of the main rectification circuit unit; and a measurement unit that measures power from an output portion of the sub-rectification circuit unit.

Description

Technical Field

[0001] The present disclosure relates to a power receiving device and a method for estimating received power.

Background Art

[0002] Conventionally, a wireless power transmission system capable of wirelessly transmitting power has been known. In a wireless power transmission system, for example, the practical application of a system to which a microwave wireless power feeding technology for IoT (Internet of Things) is applied has also been studied.

[0003] In a power receiving device of such a wireless power transmission system, efficient operation can be achieved by observing the amount of received power in real time. Further, by feeding back information on the received power to the power transmission device, the amount of transmitted power can be maintained at a necessary and sufficient level.

[0004] As conventional methods for measuring the amount of received power, a method of directly measuring the input power and a method of directly measuring the output power of a rectifier circuit are known. For example, Patent Document 1 discloses a configuration for measuring the input power amount at a measurement point between a power receiving unit and a rectifying unit.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0008] The purpose of this disclosure is to provide a power receiving device and a power receiving power estimation method that can reduce the impact of power loss.

[0009] The power receiving device related to this disclosure is The main rectifier circuit section rectifies the received power and outputs it to the load, A sub-rectifier circuit section is connected in parallel with the power receiving section of the main rectifier circuit section, A measuring unit for measuring the power of the output section of the aforementioned sub-rectifier circuit, Equipped with 、 The input impedance of the sub-rectifier circuit is greater than the input impedance of the main rectifier circuit. .

[0010] The method for estimating received power related to this disclosure is: A main rectifier circuit that rectifies the received power and outputs it to the load, and a sub-rectifier circuit connected in parallel with the power receiving section of the main rectifier circuit. The input impedance of the sub-rectifier circuit is set to be greater than the input impedance of the main rectifier circuit. A method for estimating the power received by a power receiving device comprising the following: The power of the output section of the aforementioned sub-rectifier circuit is measured, Based on the power measurement results, the output power of the main rectifier circuit is estimated.

[0011] According to this disclosure, the impact of power loss can be reduced. [Brief explanation of the drawing]

[0012] [Figure 1] This figure shows an example configuration of a wireless power transmission system to which the power receiving device according to the embodiment of this disclosure is applied. [Figure 2] This figure shows an example of the configuration of a power receiving device. [Figure 3] This figure shows an example configuration of the main rectifier circuit and the sub-rectifier circuit. [Figure 4] It is a diagram showing the relationship between the received power and the output voltage measured in an experiment. [Figure 5] It is a flowchart showing an operation example of the estimation control in the control unit. [Figure 6] It is a diagram showing the measurement results of the rectification efficiency between a comparative example and the configuration according to the present embodiment.

Mode for Carrying Out the Invention

[0013] (Embodiment) Hereinafter, embodiments of the present disclosure will be described in detail based on the drawings. FIG. 1 is a diagram showing a configuration example of a wireless power transmission system 1 to which a power receiving device 10 according to an embodiment of the present disclosure is applied.

[0014] As shown in FIG. 1, the wireless power transmission system 1 is a system capable of wirelessly transmitting power, and may be applicable to, for example, a system related to microwave wireless power feeding technology. The wireless power transmission system 1 includes a single or a plurality of power transmission devices 2 and a single or a plurality of power receiving devices 10.

[0015] The power transmission device 2 is a device that transmits power to the power receiving device 10. Each of the power transmission devices 2 has a power transmission antenna 2A and a power transmitter 2B, and may be capable of simultaneously transmitting power to each of the plurality of power receiving devices 10.

[0016] Further, the power transmission device 2 may be arranged, for example, on the ceiling of the space where power transmission is performed, or may be arranged on a wall, a floor, or an installation object (e.g., a desk, etc.) in the space. Also, the power transmission devices 2 may be arranged at equal intervals or at random intervals. Further, the power transmission device 2 may have a fixed configuration or a configuration having a moving mechanism.

[0017] The power receiving device 10 is a device that receives the power transmitted from the power transmission device 2. Each of the power receiving devices 10 may be capable of simultaneously receiving power from the power transmission device 2.

[0018] The power receiving device 10 includes a power receiving antenna 110 and a power receiving terminal 120. In the power receiving device 10, the power transmitted from the power transmitting device 2 is received by the power receiving antenna 110 and input to the power receiving terminal 120.

[0019] As shown in FIG. 2, the power receiving terminal 120 includes a load 120A that exhibits a predetermined function. The load 120A is driven when power is supplied. The predetermined function is a function that is exhibited when power is supplied, and may be, for example, a sensor function such as temperature and humidity, acceleration, electrocardiogram, etc., a display function such as an LED or a liquid crystal, a communication function such as BLE (Bluetooth (registered trademark) Low Energy) communication, etc.

[0020] The power receiving terminal 120 is configured to convert the received power (for example, an AC voltage) into power (for example, a DC voltage) that can be supplied to the load 120A and supply it to the load 120A. The power receiving terminal 120 includes a main rectifier circuit section 121, a matching section 122, a power storage section 123, a power supply section 124, a sub-rectifier circuit section 125, and a control section 126.

[0021] As shown in FIG. 3, the main rectifier circuit section 121 is a circuit section that rectifies the received AC voltage and converts it into a DC voltage, and includes a first capacitor C1, an inductor L1, a second capacitor C2, and a rectifier circuit 121A.

[0022] The first capacitor C1 and the inductor L1 are connected in series. The first capacitor C1 is connected to a power receiving section 10A that is connected to the power receiving antenna 110 on the side not connected to the inductor L1, and the inductor L1 is connected to the rectifier circuit 121A on the side not connected to the first capacitor C1. The inductor L1 may not be provided, and in that case the circuit is short-circuited.

[0023] The second capacitor C2 is provided between the wiring between the first capacitor C1 and the inductor L1 and the ground. The second capacitor C2 may not be provided, and in that case the circuit is open.

[0024] The rectifier circuit 121A may be, for example, a voltage doubler rectifier circuit, and includes two diodes D1 and D2 connected in series, and a third capacitor C3.

[0025] Diode D1 has its anode connected to the cathode of diode D2, and its cathode is connected to the first wiring 121B. The anode of diode D2 is connected to ground. The third capacitor C3 is placed between the first wiring 121B and ground. The first wiring 121B is the output wiring of the main rectifier circuit 121.

[0026] Returning to Figure 2, the impedance matching unit 122 performs impedance matching between the main rectifier circuit 121 and the load 120A by boosting or stepping down the voltage to reduce power reception losses such as reflections. The impedance matching unit 122 is provided between the first wiring 121B and the second wiring 124A of the main rectifier circuit 121. The second wiring 124A is the input wiring to the power supply unit 124. The impedance matching unit 122 may be, for example, a DC-DC converter or a charge pump.

[0027] The energy storage unit 123 is located between the second wiring 124A, which is the output side of the matching unit 122, and ground, and stores the power (DC voltage) of the second wiring 124A. The energy storage unit 123 charges and discharges based on the received power.

[0028] For example, the energy storage unit 123 discharges power to compensate if the received power is insufficient to drive a load of 120A, and charges when the received power is sufficient to drive a load of 120A.

[0029] The power supply unit 124 is connected to the second wiring 124A and generates input power (voltage) to the load 120A based on the DC voltage from the main rectifier circuit unit 121. Specifically, the power supply unit 124 boosts or steps down the DC voltage from the main rectifier circuit unit 121 to generate a voltage that can be supplied to the load 120A.

[0030] As shown in Figure 3, the sub-rectifier circuit 125 is a circuit that rectifies the received AC voltage and converts it into a DC voltage, and is connected in parallel with the main rectifier circuit 121 to the power receiving unit 10A. The sub-rectifier circuit 125 includes a fourth capacitor C4, an inductor L2, a rectifier circuit 125A, and a resistor R. The resistor R is optional, in which case the circuit is open.

[0031] The fourth capacitor C4 is provided between the third wiring 125B, which is connected to the power receiving section 10A, and the rectifier circuit 125A. The inductor L2 is provided between the third wiring 125B and ground. The inductor L2 is optional, in which case the circuit is open.

[0032] The rectifier circuit 125A has the same configuration as the rectifier circuit 121A of the main rectifier circuit section 121, and may be, for example, a voltage doubler rectifier circuit. The rectifier circuit 125A includes diodes D3 and D4 connected in series, and a fifth capacitor C5.

[0033] Diode D3 has its anode connected to the cathode of diode D4, and its cathode connected to the fourth wiring 125C. The anode of diode D4 is connected to ground. The fifth capacitor C5 is placed between the fourth wiring 125C and ground. Resistor R is placed between the fourth wiring 125C and ground in the stage after the rectifier circuit 125A in the fourth wiring 125C. The fourth wiring 125C is the output wiring of the sub-rectifier circuit section 125.

[0034] The input impedance of the sub-rectifier circuit 125 is greater than the input impedance of the main rectifier circuit 121. The input impedance of the sub-rectifier circuit 125 is determined based on the parameters of the fourth capacitor C4, inductor L2, and resistor R, since the rectifier circuit 125A has the same configuration as the rectifier circuit 121A of the main rectifier circuit 121.

[0035] In this embodiment, since the input impedance of the sub-rectifier circuit 125 is greater than the input impedance of the main rectifier circuit 121, the power loss of the main rectifier circuit 121 can be reduced compared to a configuration in which the main rectifier circuit and the sub-rectifier circuit have equivalent input impedances.

[0036] From the viewpoint of reducing power loss in the main rectifier circuit 121, the input impedance of the sub-rectifier circuit 125 should be as large as possible and preferably greater than the input impedance of the main rectifier circuit 121. For example, it is preferable that it be 100 times or more the input impedance of the main rectifier circuit 121, and even more preferable that it be 1000 times or more. In particular, if the input impedance of the sub-rectifier circuit 125 is 1000 times or more the input impedance of the main rectifier circuit 121, the power loss in the main rectifier circuit 121 caused by the sub-rectifier circuit 125 can be reduced to a negligible level.

[0037] The sub-rectifier circuit 125 can be considered as a CR parallel circuit in the fundamental wave due to the junction capacitance of the diodes. Therefore, by determining the parameters of the inductor L2 so as to cancel out the capacitance components due to diodes D3 and D4, it is possible to set the input impedance of the sub-rectifier circuit 125 higher than the input impedance of the main rectifier circuit 121.

[0038] The parameters of inductor L2 may be set appropriately depending on whether or not the input impedance of the sub-rectifier circuit 125 is set to a certain level.

[0039] The control unit 126 includes a CPU (Central Processing Unit) 126A, a ROM (Read Only Memory) 126B, a RAM (Random Access Memory) 126C, and input / output circuits (see also Figure 2).

[0040] The control unit 126 measures the voltage (power) of the output section of the sub-rectifier circuit section 125 by monitoring the output voltage of the fourth wiring 125C, which is the output wiring of the sub-rectifier circuit section 125. The control unit 126 corresponds to the "measurement section" in this disclosure.

[0041] The control unit 126 may measure the voltage (output voltage) of the output section of the sub-rectifier circuit section 125 using, for example, an A / D converter or a comparator. The control unit 126 may estimate the amount of power received based on the measurement result of the measured voltage. The control unit 126 corresponds to the "estimation section" in this disclosure.

[0042] The control unit 126 estimates the amount of power received based on the measured voltage of the sub-rectifier circuit 125, for example, by referring to a table showing the relationship between the output voltage of the sub-rectifier circuit 125 and the power received. The table showing the relationship between the output voltage and the power received may be calculated in advance by experiments or simulations, for example, as shown in Figure 4.

[0043] Figure 4 shows the relationship between the received power and output voltage measured in the experiment. In Figure 4, the vertical axis represents the logarithmic scale value (V) of the output voltage of the sub-rectifier circuit 125, and the horizontal axis represents the received power (dBm).

[0044] Figure 4 shows the experimental results obtained by applying a predetermined frequency (e.g., 920 MHz) to the power receiving point 10A using a signal generator and monitoring the output voltage of the sub-rectifier circuit 125 using a measuring instrument (e.g., a voltmeter). The white circles in Figure 4 indicate the measured output voltage corresponding to the power received value. In this experiment, the value of resistor R was set to 100 kΩ with the intention of ensuring that the input impedance of the sub-rectifier circuit 125 was sufficiently high.

[0045] For example, within the range of received power P1 to P2 in Figure 4, it can be confirmed that the output voltage exhibits linearity on a log-log graph. For example, by using the following equation (1), a regression line (see solid line in Figure 4) between the output voltage V (V) and input power P (mW) in the range of P1 to P2 can be calculated. By using this regression line as a table showing the relationship between output voltage and received power, it becomes possible to estimate the amount of received power.

[0046] V = 0.2954 × P 0.8273 ...(1) The control unit 126 may, based on the estimated power received, transmit the estimated power received to the power transmission device 2, for example via BLE communication, control the matching ratio of the matching unit 122, control the charging and discharging of the energy storage unit 123, control the load 120A, receive data, etc.

[0047] Next, an example of the operation of the power estimation control of the control unit 126 will be described. Figure 5 is a flowchart showing an example of the operation of the estimation control in the control unit 126. The process in Figure 5 is started as appropriate, for example, when the power receiving device 10 receives power transmitted from the power transmission device 2.

[0048] As shown in Figure 5, the control unit 126 measures the output voltage of the sub-rectifier circuit unit 125 (step S101). After step S101, the control unit 126 estimates the received power based on the measurement result of the output voltage (step S102). After step S102, this control ends.

[0049] According to this embodiment configured as described above, the power of the output section of the sub-rectifier circuit section 125, which is connected in parallel with the power receiving section of the main rectifier circuit section 121, is measured.

[0050] For example, conventionally, a configuration is known in which the received input power is split at the measurement point into a rectifier side and a power measurement side to measure the input power, as described in Patent Document 1. However, in this configuration, since a high-frequency signal such as input power is directly split, elements such as dividers are used for splitting. As a result, power is distributed by the divider, and the power flowing into the rectifier decreases, leading to the problem of increased power loss in the power receiving system. In addition, in this configuration, power is consumed to operate the power measurement element, so the amount of power consumed may also increase.

[0051] Specifically, when using the elements described above, several milliwatts of power are required to drive the elements. Considering that the power that can be received by the power receiving device 10 is only about several hundred microwatts, depending on the receiving distance, this has a significant impact on power loss and power consumption.

[0052] In contrast, in this embodiment, the power of the output section of the sub-rectifier circuit section 125, which is connected in parallel with the power receiving section of the main rectifier circuit section 121, is measured. Therefore, there is no need to use a dedicated power measuring element, as described in Patent Document 1. As a result, since no power is consumed to drive the element, the impact of power loss can be significantly reduced. Furthermore, since some or all of the components constituting the sub-rectifier circuit section 125 can be common with those of the main rectifier circuit section 121, the design, procurement, and evaluation processes are further simplified.

[0053] Furthermore, since it does not consume power to operate the element, the amount of power consumed can be significantly reduced compared to a configuration having the above-mentioned element.

[0054] Furthermore, while it is possible to directly measure the output power of the rectifier section in conventional methods, this method requires the installation of a measurement circuit at the output of the rectifier section, which affects the output power of the rectifier section and consequently increases the impact of DC power loss. In addition, the measurement circuit requires the independent measurement of current and voltage to calculate power, which may complicate the circuit.

[0055] In contrast, in this embodiment, the power of the output section of the sub-rectifier circuit 125 is measured, so it does not affect the output power of the main rectifier circuit 121. As a result, the impact of power loss on the output of the main rectifier circuit 121 can be reduced.

[0056] Furthermore, since the voltage at the output of the sub-rectifier circuit 125 is measured and the received power is estimated based on that voltage, there is no need to install a complex circuit. As a result, the configuration can be simplified, which can contribute to miniaturization and cost reduction of the power receiving device 10.

[0057] Since the input impedance of the sub-rectifier circuit 125 is greater than the input impedance of the main rectifier circuit 121, the impact of power loss can be reduced compared to a configuration in which the input impedance of the sub-rectifier circuit is equal to or less than the input impedance of the main rectifier circuit.

[0058] For example, if the input impedance of the sub-rectifier circuit 125 is set to about 1000 times the input impedance of the main rectifier circuit 121, the impact of power loss can be reduced to such an extent that the presence of the sub-rectifier circuit 125 can be ignored from the perspective of the receiving antenna 110.

[0059] For example, Figure 6 shows the measurement results of the rectification efficiency for a configuration without a sub-rectifier circuit (comparative example) and the configuration according to this embodiment. The measurement results shown in Figure 6 are the results of experimental measurements of the rectification efficiency when the input power was varied for both the comparative example and this embodiment.

[0060] As shown in Figure 6, it can be confirmed that the comparative example (dashed line) and this embodiment (solid line) achieve approximately the same rectification efficiency across the entire range of input power.

[0061] Furthermore, since the sub-rectifier circuit section 125 is connected in parallel with the main rectifier circuit section 121, the configuration of the power receiving device 10 can be simplified.

[0062] Furthermore, since there is no need to use elements for branching the received power, the main rectifier circuit 121 and the sub-rectifier circuit 125 can be housed in a single IC (Integrated Circuit). As a result, the power receiving device 10 can be made smaller overall.

[0063] In the above embodiment, the output voltage of the sub-rectifier circuit 125 was measured, but the disclosure is not limited thereto, and the output current of the sub-rectifier circuit 125 may also be measured. Furthermore, when measuring the output current of the sub-rectifier circuit 125, the received power may be estimated based on the output voltage and output current.

[0064] Furthermore, although the above embodiment used a voltage doubler rectifier circuit as the rectifier circuit, this disclosure is not limited to this, and other rectifier circuits such as a bridge-type rectifier circuit or a 4x voltage doubler rectifier circuit may also be used.

[0065] Furthermore, in the above embodiment, the input impedance of the sub-rectifier circuit 125 was greater than the input impedance of the main rectifier circuit 121, but this disclosure is not limited thereto, and for example, it may be less than or equal to the input impedance of the main rectifier circuit 121. However, from the viewpoint of reducing power loss, it is preferable that the input impedance of the sub-rectifier circuit 125 is greater than the input impedance of the main rectifier circuit 121.

[0066] Furthermore, the parameters of the capacitor, inductor, resistor, and diode in the above embodiment may be set appropriately according to the specifications of the power receiving device 10, etc.

[0067] Furthermore, the embodiments described above are merely examples of how this disclosure may be implemented, and the technical scope of this disclosure should not be limited by them. In other words, this disclosure can be implemented in various ways without departing from its essence or its main features. [Industrial applicability]

[0068] The power receiving device described herein is useful as a power receiving device and a method for estimating power received, as it is capable of reducing the effects of power loss. [Explanation of symbols]

[0069] 1. Wireless Power Transmission System 2. Power transmission equipment 2A transmission antenna 2B power transmitter 10 Power receiving device 110 Receiving Antenna 120 Power Receiving Terminal 121 Main rectifier circuit section 122 Matching section 123 Energy Storage Unit 124 Power supply section 125 Sub-rectifier circuit section 126 Control Unit

Claims

1. The main rectifier circuit section rectifies the received power and outputs it to the load, A sub-rectifier circuit section is connected in parallel with the power receiving section of the main rectifier circuit section, A measuring unit for measuring the power of the output section of the aforementioned sub-rectifier circuit, Equipped with, The input impedance of the sub-rectifier circuit is greater than the input impedance of the main rectifier circuit. Power receiving device.

2. The aforementioned sub-rectifier circuit section is, A rectifier circuit having the output section, An inductor is provided between the power receiving unit and the ground, A capacitor having one end connected to the power receiving unit and the other end connected to the rectifier circuit, Having, The power receiving device according to claim 1.

3. The measuring unit measures the output voltage of the sub-rectifier circuit. The power receiving device according to claim 1 or claim 2.

4. The system includes an estimation unit that estimates the output power of the main rectifier circuit based on the measurement results of the measurement unit. A power receiving device according to any one of claims 1 to 3.

5. The aforementioned load and, A matching unit is provided between the main rectifier circuit and the load to perform impedance matching between the main rectifier circuit and the load. A power storage unit is provided at the output section of the matching unit, which charges and discharges according to the received power, A power supply unit that generates input power to the load based on the output power of the main rectifier circuit unit, The power receiving device according to claim 4.

6. A method for estimating the power received by a power receiving device, comprising: a main rectifier circuit that rectifies the received power and outputs it to a load; and a sub-rectifier circuit connected in parallel to the power receiving section of the main rectifier circuit, wherein the input impedance of the sub-rectifier circuit is set to be greater than that of the input impedance of the main rectifier circuit; The power of the output section of the aforementioned sub-rectifier circuit is measured, Based on the power measurement results, the output power of the main rectifier circuit is estimated. Method for estimating received power.

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