JP2019058035A - Power-receiving device - Google Patents

Abstract

To provide a power-receiving device which can adequately retain an input impedance of a rectification circuit at an optimum value.SOLUTION: A power-receiving coil 11 receives AC power transmitted from a transmission coil 2c for sending AC power in a non-contact manner. A bridge rectification circuit 20 rectifies the AC power received by the power-receiving coil 11 into a DC power, and supplies the DC power to a load part 3. An adjustment capacitor group 40 is connected in parallel with the bridge rectification circuit 20, and charges a DC power supplied from the bridge rectification circuit 20 to the load part 3. A switch part 50 switches the connection of the adjustment capacitor group 40 and the bridge rectification circuit 20 to ON or OFF. A detector part 70 serves to detect a voltage and a current of the DC power supplied to the load part 3. A control part 80 controls the switch part 50 based on the voltage and current detected by the detector part 70, and adjusts an amount of charging power to be charged into the adjustment capacitor group 40.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power receiving apparatus.

  Conventionally, as a power receiving device, for example, Patent Document 1 discloses a receiving coil that receives AC power, a rectifying circuit that rectifies AC power received by the receiving coil into DC power, and supplies the DC power to a load unit, A non-contact power receiving device including a variable capacitor provided between a circuit and a load unit is disclosed. This non-contact power receiving apparatus maintains the input impedance of the rectifier circuit at an optimum value by adjusting the capacitance of the variable capacitor according to the change in the impedance of the load unit.

JP 2017-112763 A

  By the way, the non-contact power receiving device described in Patent Document 1 described above uses, for example, a variable capacitor when the input impedance of the rectifier circuit is maintained at an optimum value. Examples of the variable capacitor include a variable capacitor that mechanically changes the positional relationship between the electrode plates, and a varicap (varactor) that uses a parasitic capacitance of a diode. Non-contact power receiving devices tend to increase in size for variable capacitors, and tend to reduce adjustable capacity for varicaps (varactors). There is room for further improvement.

  Therefore, the present invention has been made in view of the above, and an object thereof is to provide a power receiving apparatus that can appropriately maintain the input impedance of a rectifier circuit at an optimum value.

  In order to solve the above-described problems and achieve the object, a power receiving device according to the present invention includes a power receiving coil that receives the AC power transmitted in a contactless manner from a power transmitting coil that transmits AC power, and the power receiving coil. A rectifier circuit that rectifies the received AC power into DC power and supplies the DC power to a load unit, and is connected in parallel to the rectifier circuit, and charges the DC power supplied from the rectifier circuit to the load unit. A capacitor unit; a switch unit that switches on or off the connection between the capacitor unit and the rectifier circuit; a detection unit that detects the voltage and current of the DC power supplied to the load unit; And a control unit that controls the switch unit based on the voltage and the current and adjusts a charge amount charged in the capacitor unit.

  In the power receiving device, the rectifier circuit includes a first diode, a second diode, a third diode, and a fourth diode, and the capacitor unit includes a first capacitor and a second capacitor, The switch unit includes a first switch and a second switch, and the rectifier circuit includes the first and second diodes connected in series in the forward direction, and the third and fourth diodes in the forward direction. The first and second diodes in the forward direction and the third and fourth diodes in the forward direction are connected in parallel, and the capacitor section includes the first capacitor in parallel with the third diode. The second capacitor is connected in parallel to the fourth diode, and the switch unit includes a first switch connected to a connection point between the third diode and the load unit. The second switch is connected between a connection point of the fourth diode and the load section and the second capacitor, and the power receiving coil has one end of the power receiving coil connected to the first capacitor. Connected to a connection point of the first diode and the second diode, the other end of the power receiving coil is connected to a connection point of the third diode and the fourth diode, and the control unit is detected by the detection unit It is preferable to control the first switch and the second switch based on the applied voltage and current to adjust the charge amount charged in the first capacitor and the second capacitor.

  In the above power receiving device, it is preferable that the control unit controls the first switch and the second switch based on a load voltage applied to either the first capacitor or the second capacitor.

  In the above power receiving device, the control unit relatively increases the charge amount of the capacitor unit when the impedance of the load unit increases, and increases the charge amount of the capacitor unit when the impedance of the load unit decreases. It is preferable to relatively reduce it.

  A power receiving device according to the present invention includes a capacitor unit that is connected in parallel to a rectifier circuit and charges DC power supplied from the rectifier circuit to a load unit. And a power receiving apparatus can maintain the input impedance of a rectifier circuit to an optimal value appropriately by adjusting the charge amount charged to a capacitor part according to the change of the impedance of a load part.

FIG. 1 is a circuit diagram illustrating a configuration example of a power receiving device according to the embodiment. FIG. 2 is a diagram illustrating a relationship between the switch on / off signal and the load voltage according to the embodiment. FIG. 3 is a diagram illustrating a relationship between the impedance of the load unit and the input impedance of the rectifier circuit according to the embodiment. FIG. 4 is a flowchart illustrating an operation example of the power receiving device according to the embodiment. FIG. 5 is a circuit diagram illustrating a configuration example of the power receiving device according to the first modification of the embodiment. FIG. 6 is a sequence chart illustrating an operation example of the first and second switches according to the first modification of the embodiment. FIG. 7 is a circuit diagram illustrating a configuration example of the power receiving device according to the second modification of the embodiment. FIG. 8 is a circuit diagram illustrating a configuration example of the power receiving device according to the third modification of the embodiment.

  DESCRIPTION OF EMBODIMENTS Embodiments (embodiments) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited by the contents described in the following embodiments. The constituent elements described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the structures described below can be combined as appropriate. Various omissions, substitutions, or changes in the configuration can be made without departing from the scope of the present invention.

Embodiment
The power receiving device 1 according to the embodiment will be described. As shown in FIG. 1, the power receiving device 1 constitutes a power transmission system 100 together with the power transmitting device 2. The power transmission system 100 is applied to, for example, EV (Electric Vehicle), PHEV (Plug / Hybrid Electric Vehicle), and the like. In the power transmission system 100, for example, the power receiving device 1 is mounted on an EV, a PHEV, or the like, and the power supplied from the external power transmitting device 2 is received by the power receiving device 1 to charge the battery. Note that the power transmission system 100 may be applied not only to battery charging but also to power feeding to a portion that requires non-contact power feeding at a movable part such as a vehicle seat or a door.

  The power transmission system 100 transmits power in a non-contact manner by magnetic resonance or the like via the power transmission side resonance circuit 2b and the power reception side resonance circuit 10. For example, the power transmission system 100 transmits power by magnetic resonance in which the vibration of the magnetic field due to the alternating current flowing in the power transmission side resonance circuit 2b is transmitted to the power reception side resonance circuit 10 that resonates at the same frequency. In the present embodiment, the power transmission system 100 maintains the input impedance of the bridge rectifier circuit 20 in the power receiving device 1 at an optimum value by adjusting the charge amount of the adjustment capacitor group 40 provided in the power receiving device 1. is there.

  The power transmission device 2 is a device that transmits power without contact. The power transmission device 2 includes an AC power source 2a and a power transmission side resonance circuit 2b. The AC power source 2a is connected to the power transmission side resonance circuit 2b and supplies AC power to the power transmission side resonance circuit 2b. The power transmission side resonance circuit 2b includes a power transmission coil 2c and a resonance capacitor 2d, and the power transmission coil 2c and the resonance capacitor 2d are connected in series. In the power transmission side resonance circuit 2b, the power transmission coil 2c is provided so as to face the power reception coil 11 of the power reception device 1, and transmits power in a non-contact manner via the power transmission coil 2c by magnetic resonance or the like.

  The power receiving device 1 is a device that receives power in a non-contact manner via the power receiving resonance circuit 10. The power receiving device 1 includes a power receiving side resonance circuit 10, a bridge rectifier circuit 20 as a rectifier circuit, a fixed capacitor group 30, a regulation capacitor group 40 as a capacitor unit, a switch unit 50, a smoothing circuit 60, and a detection unit. 70 and a control unit 80.

  The power receiving side resonance circuit 10 includes a power receiving coil 11 and a resonance capacitor 12, and the power receiving coil 11 and the resonance capacitor 12 are connected in series. In the power receiving side resonance circuit 10, the power receiving coil 11 is provided to face the power transmitting coil 2 c of the power transmitting device 2, and receives power in a non-contact manner via the power receiving coil 11 by magnetic resonance or the like.

  The bridge rectifier circuit 20 is a circuit that performs full-wave rectification of AC power to DC power. The bridge rectifier circuit 20 is connected to the power reception side resonance circuit 10 and rectifies AC power received by the power reception side resonance circuit 10 into DC power. The bridge rectifier circuit 20 is connected to the load unit 3 and supplies the rectified DC power to the load unit 3 through the fixed capacitor group 30, the adjustment capacitor group 40, and the smoothing circuit 60. The bridge rectifier circuit 20 includes a first diode D1, a second diode D2, a third diode D3, and a fourth diode D4. In the bridge rectifier circuit 20, the first diode D1 and the second diode D2 are connected in series in the forward direction, and the third diode D3 and the fourth diode D4 are connected in series in the forward direction. In the bridge rectifier circuit 20, the first and second diodes D1 and D2 in the forward direction and the third and fourth diodes D3 and D4 in the forward direction are connected in parallel. In the bridge rectifier circuit 20, one end 11a of the power receiving coil 11 is connected to a connection point between the first diode D1 and the second diode D2, and the other end 11b of the power receiving coil 11 is connected to the third diode D3 and the fourth diode D4. Connected to the connection point. In the bridge rectifier circuit 20, the power supplied from the one end 11a of the power receiving coil 11 is supplied to the load unit 3 via the first diode D1. In the bridge rectifier circuit 20, the power supplied from the other end 11b of the power receiving coil 11 is supplied to the load unit 3 via the third diode D3.

  The fixed capacitor group 30 is a capacitance unit that charges and discharges electric power. The fixed capacitor group 30 is provided between the bridge rectifier circuit 20 and the adjustment capacitor group 40 and is connected to the bridge rectifier circuit 20 in parallel. The fixed capacitor group 30 charges the DC power supplied from the bridge rectifier circuit 20 to the load unit 3 and discharges the charged DC power. Fixed capacitor group 30 includes a first fixed capacitor Cfu and a second fixed capacitor Cfl. In the fixed capacitor group 30, the first fixed capacitor Cfu is connected in parallel to the third diode D3, and the second fixed capacitor Cfl is connected in parallel to the fourth diode D4. The fixed capacitor group 30 is a load that can be seen from the bridge rectifier circuit 20 by the voltage charged in the fixed capacitor group 30 during a period in which the direction of the alternating current input to the bridge rectifier circuit 20 changes and the alternating current becomes relatively small. The voltage of part 3 is canceled out. By this cancellation, the power receiving device 1 can suppress an increase in input impedance of the bridge rectifier circuit 20 as viewed from the power receiving coil 11.

  The adjustment capacitor group 40 is a capacitance unit that charges and discharges electric power. The adjustment capacitor group 40 is provided between the fixed capacitor group 30 and the smoothing circuit 60 and connected in parallel to the bridge rectifier circuit 20. The adjustment capacitor group 40 charges DC power supplied from the bridge rectifier circuit 20 to the load unit 3 and discharges the charged DC power. The adjustment capacitor group 40 includes a first adjustment capacitor Cvu and a second adjustment capacitor Cvl. In the adjustment capacitor group 40, the first adjustment capacitor Cvu is connected in parallel to the third diode D3, and the second adjustment capacitor Cvl is connected in parallel to the fourth diode D4. The adjustment capacitor group 40 has a load that can be seen from the bridge rectification circuit 20 by the voltage charged in the adjustment capacitor group 40 during a period in which the direction of the alternating current input to the bridge rectification circuit 20 changes and the alternating current becomes relatively small. The voltage of part 3 is canceled out. By this cancellation, the power receiving device 1 can suppress an increase in input impedance of the bridge rectifier circuit 20 as viewed from the power receiving coil 11. In the adjustment capacitor group 40, the charge amount is adjusted by the control unit 80 described later according to the change in the impedance of the load unit 3.

  The switch unit 50 is a circuit that switches on or off the electrical connection of the circuit. For example, the switch unit 50 switches the connection between the adjustment capacitor group 40 and the bridge rectifier circuit 20 on or off. The switch unit 50 includes a first switch Svu and a second switch Svl. The first and second switches Svu and Svl are configured by bipolar transistors, FETs (Field Effect Transistors), or the like. The first switch Svu is connected between the connection point of the third diode D3 and the load unit 3 and the first adjustment capacitor Cvu. The first switch Svu is connected to the control unit 80 and turns on the electrical connection between the first adjustment capacitor Cvu and the third diode D3 based on a switch-on signal or a switch-off signal output from the control unit 80. Or turn it off. When turned on, the first switch Svu electrically connects the first adjustment capacitor Cvu and the third diode D3. When the first switch Svu is turned off, the electrical connection between the first adjustment capacitor Cvu and the third diode D3 is released. The first switch Svu is provided with a discharging diode D5 in parallel, but the diode D5 may be omitted. The second switch Svl is connected between the connection point of the fourth diode D4 and the load unit 3 and the second adjustment capacitor Cvl. The second switch Svl is connected to the control unit 80 and turns on the electrical connection between the second adjustment capacitor Cvl and the fourth diode D4 based on the switch-on signal or the switch-off signal output from the control unit 80. Or turn it off. When the second switch Svl is turned on, the second switch capacitor Cvl and the fourth diode D4 are electrically connected. When the second switch Svl is turned off, the electrical connection between the second adjustment capacitor Cvl and the fourth diode D4 is released. The second switch Svl is provided with a discharging diode D6 in parallel, but the diode D6 may be omitted.

  The smoothing circuit 60 is a circuit that smoothes a direct current (pulsating flow) supplied to the load unit 3. The smoothing circuit 60 is provided between the adjustment capacitor group 40 and the load unit 3. The smoothing circuit 60 has a smoothing capacitor 61, and the smoothing capacitor 61 is connected to the load unit 3 in parallel. The smoothing circuit 60 smoothes the direct current (pulsating current) supplied to the load unit 3 by the smoothing capacitor 61.

  The detection unit 70 is a circuit that detects voltage and current. The detection unit 70 detects, for example, the voltage and current of DC power supplied to the load unit 3. The detection unit 70 includes a voltage detection unit 71 and a current detection unit 72. The voltage detection unit 71 is connected in parallel to the load unit 3 via an operational amplifier 73, for example. The voltage detector 71 detects a voltage based on the voltage signal differentially output by the operational amplifier 73. The voltage detection unit 71 is connected to an impedance calculation unit 81 described later, and outputs a detection voltage that is a detected voltage to the impedance calculation unit 81. The current detection unit 72 is provided between the smoothing circuit 60 and the anode side of the load unit 3, and detects a current flowing from the smoothing circuit 60 to the load unit 3. The current detection unit 72 is connected to the impedance calculation unit 81 and the impedance ratio calculation unit 83, and outputs a detected current that is a detected current to the impedance calculation unit 81 and the impedance ratio calculation unit 83.

  The control unit 80 is a circuit that controls the switch unit 50. The control unit 80 includes an electronic circuit mainly composed of a well-known microcomputer including a CPU, a ROM that constitutes a storage unit, a RAM, and an interface. For example, the control unit 80 controls the switch unit 50 based on the detection voltage and the detection current detected by the detection unit 70 to adjust the charge amount charged in the adjustment capacitor group 40. That is, the control unit 80 adjusts the amount of charge charged in the adjustment capacitor group 40 according to the change in the impedance of the load unit 3. For example, when the impedance of the load unit 3 increases, the control unit 80 increases the charge amount of the adjustment capacitor group 40 relatively, and when the impedance of the load unit 3 decreases, the control unit 80 sets the charge amount of the adjustment capacitor group 40 relatively. Reduce it. By this control, the control unit 80 can maintain the input impedance of the bridge rectifier circuit 20 at an optimum value (about 5Ω as an example) as shown in FIG. In FIG. 3, the vertical axis represents the input impedance of the bridge rectifier circuit 20, and the horizontal axis represents the impedance of the load unit 3. FIG. 3 shows the input impedance of the bridge rectifier circuit 20 according to the embodiment and the input impedance of the bridge rectifier circuit 20 according to the comparative example. A comparative example is an example which does not adjust the charge amount charged to the adjustment capacitor group 40 like embodiment. In the comparative example, as the impedance of the load unit 3 increases, the input impedance of the bridge rectifier circuit 20 also increases. The control unit 80 includes an impedance calculation unit 81, an optimum impedance setting unit 82, an impedance ratio calculation unit 83, a set capacitor capacity calculation unit 84, a maximum capacitor capacity setting unit 85, a capacitor capacity ratio calculation unit 86, and a threshold value. A voltage calculation unit 87 and first and second comparators 88 and 89 are included.

  The impedance calculation unit 81 is a circuit that calculates the impedance of the load unit 3. The impedance calculation unit 81 is connected to the voltage detection unit 71 and the current detection unit 72. The impedance calculation unit 81 calculates the impedance of the load unit 3 based on the detection voltage output from the voltage detection unit 71 and the detection current output from the current detection unit 72. The impedance calculation unit 81 is connected to the impedance ratio calculation unit 83 and outputs the calculated impedance of the load unit 3 to the impedance ratio calculation unit 83.

  The optimum impedance setting unit 82 is a circuit that sets an optimum impedance that is an optimum impedance viewed from the power receiving coil 11. The optimum impedance setting unit 82 holds the optimum impedance in advance. This optimum impedance is determined by, for example, the impedance of the power transmission coil 2c and the power reception coil 11, the coupling coefficient between the power transmission coil 2c and the power reception coil 11, or the like. The optimum impedance setting unit 82 is connected to the impedance ratio calculation unit 83 and outputs the optimum impedance to the impedance ratio calculation unit 83.

  The impedance ratio calculation unit 83 is a circuit that calculates an impedance ratio. The impedance ratio calculation unit 83 is connected to the voltage detection unit 71, the current detection unit 72, the impedance calculation unit 81, and the optimum impedance setting unit 82. The impedance ratio calculation unit 83 calculates load power that is power supplied to the load unit 3 based on the detection voltage output from the voltage detection unit 71 and the detection current output from the current detection unit 72. Further, the impedance ratio calculation unit 83 is based on the impedance of the load unit 3 output from the impedance calculation unit 81 and the optimum impedance output from the optimum impedance setting unit 82, and the ratio between the impedance of the load unit 3 and the optimum impedance. An impedance ratio which is (impedance of load unit 3 / optimal impedance) is calculated. The impedance ratio calculation unit 83 is connected to the set capacitor capacity calculation unit 84, and outputs the impedance ratio, load power, and detection voltage to the set capacitor capacity calculation unit 84.

The set capacitor capacity calculation unit 84 is a circuit that calculates the capacity of the capacitor. The setting capacitor capacity calculation unit 84 calculates a setting capacitor capacity that is the capacity of the first and second adjustment capacitors Cvu and Cvl based on, for example, the impedance ratio, the load power, and the detection voltage. The set capacitor capacity calculation unit 84 calculates the set capacitor capacity by an approximate expression using, for example, the impedance ratio, the load power, and the detection voltage as parameters. Specifically, the set capacitor capacity calculation unit 84 sets the following equation (1) when the impedance ratio is Zout / Zin, the load power is Pl, the detection voltage is Vl, and the set capacitor capacity is Cp. Calculate the capacitance of the capacitor. In Expression (1), for example, the function h (x) is a quadratic expression, the function g (x) is a quartic expression, and the function f (x) is a linear expression. The set capacitor capacity calculator 84 is connected to the capacitor capacity ratio calculator 86 and outputs the calculated set capacitor capacity to the capacitor capacity ratio calculator 86.
Cp = h (Zout / Zin, g (Vl, f (Pl))) (1)

  The maximum capacitor capacity setting unit 85 is a circuit that sets the maximum capacitor capacity. The maximum capacitor capacity setting unit 85 holds, for example, the maximum capacitor capacity of the first adjustment capacitor Cvu and the maximum capacitor capacity of the second adjustment capacitor Cvl in the adjustment capacitor group 40 in advance. The maximum capacitor capacity setting unit 85 further holds in advance the capacity of the first fixed capacitor Cfu and the capacity of the second fixed capacitor Cfl. The maximum capacitor capacity setting unit 85 is connected to the capacitor capacity ratio calculation unit 86, and the maximum capacitor capacity of the first adjustment capacitor Cvu, the maximum capacitor capacity of the second adjustment capacitor Cvl, the capacity of the first fixed capacitor Cfu, and the second The capacitance of fixed capacitor Cfl is output to capacitor capacitance ratio calculation unit 86.

  The capacitor capacity ratio calculator 86 is a circuit that calculates a capacitor capacity ratio. The capacitor capacity ratio calculation unit 86 includes, for example, the setting capacitor capacity output from the setting capacitor capacity calculation unit 84 and the maximum capacitor capacity of the first and second adjustment capacitors Cvu and Cvl output from the maximum capacitor capacity setting unit 85. Based on the capacitances of the first and second fixed capacitors Cfu and Cfl, the capacitor capacitance ratio of the first and second adjustment capacitors Cvu and Cvl is calculated. The capacitor capacity ratio calculator 86 is connected to the threshold voltage calculator 87 and outputs the calculated capacitor capacity ratio of the first and second adjustment capacitors Cvu and Cvl to the threshold voltage calculator 87.

The threshold voltage calculation unit 87 is a circuit that calculates the first threshold voltage Vth. The threshold voltage calculator 87 is connected to the capacitor capacitance ratio calculator 86 and the voltage detector 71. The capacitor capacitance ratio of the first and second adjustment capacitors Cvu and Cvl is output from the capacitor capacitance ratio calculator 86, and the voltage detector A detection voltage is output from 71. Then, the threshold voltage calculation unit 87 calculates the first threshold voltage Vth of the first and second adjustment capacitors Cvu, Cvl based on the capacitance ratio of the first and second adjustment capacitors Cvu, Cvl and the detected voltage. . Specifically, the set capacitor capacity is Cp, the maximum capacitor capacity of the first and second adjustment capacitors Cvu, Cvl is Cv, the capacity of the first and second fixed capacitors Cfu, Cfl is Cf, and the detection voltage is V And In this case, the capacitor capacitance ratio of the first and second adjustment capacitors Cvu and Cvl is (Cp−Cf) / Cv, and the target charging voltage of the first and second adjustment capacitors Cvu and Cvl is obtained by the following equation (2). V1, that is, the first threshold voltage Vth is obtained.
V1 = V × (Cp−Cf) / Cv (2)

  The threshold voltage calculation unit 87 is connected to the first and second comparators 88 and 89, outputs the first threshold voltage Vth of the first adjustment capacitor Cvu to the first comparator 88, and the first threshold voltage of the second adjustment capacitor Cvl. Vth is output to the second comparator 89.

  The first and second comparators 88 and 89 are circuits that output the result of comparing two voltages. The first comparator 88 has a first input terminal 88a connected to the threshold voltage calculator 87, a second input terminal 88b connected to the first fixed capacitor Cfu via the operational amplifier 88c, and an output terminal connected to the first switch Svu. Is done. The first comparator 88 compares the first threshold voltage Vth of the first adjustment capacitor Cvu output from the threshold voltage calculator 87 with the load voltage applied to the first adjustment capacitor Cvu (switch-on signal or switch-off). Signal) to the first switch Svu. For example, as shown in FIG. 2, when the load voltage applied to the first adjustment capacitor Cvu is equal to or higher than the first threshold voltage Vth of the first adjustment capacitor Cvu, the first comparator 88 sends a switch-off signal to the first switch Svu. Output to. For example, when the load voltage applied to the first adjustment capacitor Cvu is lower than the first threshold voltage Vth of the first adjustment capacitor Cvu, the first comparator 88 outputs a switch-on signal to the first switch Svu.

  The second comparator 89 has a first input terminal 89a connected to the threshold voltage calculator 87, a second input terminal 89b connected to the second fixed capacitor Cfl, and an output terminal connected to the second switch Svl. The second comparator 89 outputs the result of comparing the first threshold voltage Vth of the second adjustment capacitor Cvl output from the threshold voltage calculator 87 and the load voltage applied to the second adjustment capacitor Cvl to the second switch Svl. To do. For example, as shown in FIG. 2, the second comparator 89 outputs a switch-off signal to the second switch Svl when the load voltage applied to the second adjustment capacitor Cvl is equal to or higher than the first threshold voltage Vth of the second adjustment capacitor Cvl. Output to. For example, when the load voltage applied to the second adjustment capacitor Cvl is less than the first threshold voltage Vth of the second adjustment capacitor Cvl, the second comparator 89 outputs a switch-on signal to the second switch Svl.

  Next, an operation example of the power receiving device 1 will be described with reference to FIG. The power receiving device 1 detects a voltage and a current (step S1). For example, the voltage detection unit 71 detects the voltage of the DC power supplied to the load unit 3, and the current detection unit 72 detects the current of the DC power supplied to the load unit 3. Next, the power receiving device 1 calculates the impedance of the load unit 3 (step S2). For example, the impedance calculation unit 81 calculates the impedance of the load unit 3 based on the detection voltage output from the voltage detection unit 71 and the detection current output from the current detection unit 72. Next, the power receiving apparatus 1 calculates an impedance ratio (step S3). For example, the impedance ratio calculation unit 83 calculates the impedance ratio based on the impedance of the load unit 3 and the optimum impedance. Next, the power receiving device 1 calculates a set capacitor capacity (step S4). For example, the set capacitor capacity calculation unit 84 calculates the set capacitor capacity of the first and second adjustment capacitors Cvu and Cvl based on the impedance ratio, the load power, and the detection voltage. Next, the power receiving device 1 calculates a capacitor capacitance ratio (step S5). For example, the capacitor capacity ratio calculation unit 86 may perform the first and second operations based on the set capacitor capacity, the maximum capacitor capacity of the first and second adjustment capacitors Cvu and Cvl, and the capacity of the first and second fixed capacitors Cfu and Cfl. The capacitance ratio of the adjustment capacitors Cvu and Cvl is calculated. Next, the power receiving apparatus 1 calculates the first threshold voltage Vth as the threshold voltage of the first and second adjustment capacitors Cvu and Cvl (step S6). For example, the threshold voltage calculation unit 87 calculates the first threshold voltage Vth of the first and second adjustment capacitors Cvu and Cvl based on the capacitance ratio of the first and second adjustment capacitors Cvu and Cvl and the detected voltage. . Next, the power receiving device 1 sets the first threshold voltage Vth (step S7). For example, the threshold voltage calculation unit 87 outputs the first threshold voltage Vth to the first and second comparators 88 and 89. Next, the power receiving apparatus 1 determines whether or not the load voltage is equal to or higher than the first threshold voltage Vth of the first and second adjustment capacitors Cvu and Cvl (Step S8). For example, when the load voltage is equal to or higher than the first threshold voltage Vth of the first adjustment capacitor Cvu (step S8; Yes), the first comparator 88 turns off the first switch Svu (step S9) and goes to the first adjustment capacitor Cvu. Is stopped and the process is terminated (the same process is repeated from step S1 described above). Further, when the load voltage is lower than the first threshold voltage Vth of the first adjustment capacitor Cvu (step S8; No), the first comparator 88 turns on the first switch Svu (step S10), and goes to the first adjustment capacitor Cvu. The DC power is charged and the process ends.

  As described above, the power receiving device 1 according to the embodiment includes the power receiving coil 11, the bridge rectifier circuit 20, the adjustment capacitor group 40, the switch unit 50, the detection unit 70, and the control unit 80. The power receiving coil 11 receives AC power transmitted in a non-contact manner from a power transmission coil 2c that transmits AC power. The bridge rectifier circuit 20 rectifies the AC power received by the power receiving coil 11 to DC power and supplies the DC power to the load unit 3. The adjustment capacitor group 40 is connected in parallel to the bridge rectifier circuit 20 and charges DC power supplied from the bridge rectifier circuit 20 to the load unit 3. The switch unit 50 switches the connection between the adjustment capacitor group 40 and the bridge rectifier circuit 20 on or off. The detection unit 70 detects the voltage and current of the DC power supplied to the load unit 3. The control unit 80 controls the switch unit 50 based on the voltage and current detected by the detection unit 70 to adjust the charge amount charged in the adjustment capacitor group 40.

  With this configuration, the power receiving device 1 can obtain the impedance of the load unit 3 based on the voltage and current detected by the detection unit 70. The power receiving device 1 can maintain the input impedance of the bridge rectifier circuit 20 at an optimum value by adjusting the amount of charge charged in the adjustment capacitor group 40 according to the change in impedance of the load unit 3. That is, the power receiving device 1 can maintain the impedance on the load portion 3 side viewed from the power receiving coil 11 side at an optimum value. As a result, the power receiving device 1 can suppress a decrease in power transmission efficiency. The power receiving device 1 can make the capacitance of the adjustment capacitor group 40 substantially variable by adjusting the charge amount of the adjustment capacitor group 40. With this configuration, the power receiving device 1 can suppress an increase in size and manufacturing cost compared to a conventional variable capacitor, and an adjustable capacity compared to a conventional varicap (varactor). It can suppress becoming small. Thus, the power receiving device 1 can be configured simply and at low cost, and can adjust the impedance continuously over a wide range.

  In the power receiving device 1, the bridge rectifier circuit 20 includes a first diode D1, a second diode D2, a third diode D3, and a fourth diode D4. The adjustment capacitor group 40 includes a first adjustment capacitor Cvu and a second adjustment capacitor Cvl. The switch unit 50 includes a first switch Svu and a second switch Svl. In the bridge rectifier circuit 20, the first and second diodes D1 and D2 are connected in series in the forward direction, the third and fourth diodes D3 and D4 are connected in series in the forward direction, and the first and second diodes in the forward direction are connected. Second diodes D1 and D2 and forward third and fourth diodes D3 and D4 are connected in parallel. In the adjustment capacitor group 40, the first adjustment capacitor Cvu is connected in parallel to the third diode D3, and the second adjustment capacitor Cvl is connected in parallel to the fourth diode D4. In the switch unit 50, the first switch Svu is connected between the connection point of the third diode D3 and the load unit 3 and the first adjustment capacitor Cvu, and the second switch Svl is connected to the connection point of the fourth diode D4 and the load unit 3. And the second adjustment capacitor Cvl. In the power receiving coil 11, one end 11a of the power receiving coil 11 is connected to a connection point between the first diode D1 and the second diode D2, and the other end 11b of the power receiving coil 11 is connected to the third diode D3 and the fourth diode D4. Connected to the connection point. The control unit 80 controls the first switch Svu and the second switch Svl based on the voltage and current detected by the detection unit 70 and adjusts the charge amount charged in the first adjustment capacitor Cvu and the second adjustment capacitor Cvl. To do. With this configuration, the power receiving device 1 optimizes the input impedance of the bridge rectifier circuit 20 by adjusting the amount of charge charged in the first and second adjustment capacitors Cvu and Cvl according to the change in the impedance of the load unit 3. Value can be maintained.

  In the power receiving device 1, the control unit 80 relatively increases the charge amount of the adjustment capacitor group 40 when the impedance of the load unit 3 increases, and when the impedance of the load unit 3 decreases, Reduce the amount of charge relatively. With this configuration, the power receiving device 1 can maintain the input impedance of the bridge rectifier circuit 20 at an optimum value by increasing or decreasing the amount of charge charged to the adjustment capacitor group 40 according to the increase or decrease of the impedance of the load unit 3. it can.

[Modification]
Next, modified examples 1 to 3 of the embodiment will be described. In the first to third modifications, the same reference numerals are given to the same components as those in the embodiment, and the detailed description thereof is omitted. In the power receiving device 1A according to the first modification, the first comparator 88 controls the first switch Svu based on the load voltage applied to the second adjustment capacitor Cvl instead of the load voltage applied to the first adjustment capacitor Cvu. This is different from the power receiving device 1 according to the embodiment. Here, the load voltage applied to the first adjustment capacitor Cvu and the load voltage applied to the second adjustment capacitor Cvl are such that when one load voltage increases, the other load voltage decreases and one load voltage decreases. Then, it changes in contrast so that the other load voltage increases. If this symmetrically changing event is used, both the first and second switches Svu and Svl can be controlled based on one load voltage. That is, the power receiving device 1A controls the first and second switches Svu and Svl based on the load voltage applied to either the first adjustment capacitor Cvu or the second adjustment capacitor Cvl. The power receiving device 1A includes, for example, a calculator 88d that calculates a second threshold voltage Vthu for controlling the first switch Svu based on a load voltage applied to the second adjustment capacitor Cvl. The computing unit 88d obtains a second threshold voltage Vthu (see FIG. 6) by subtracting the first threshold voltage Vth output from the threshold voltage calculator 87 from the detected voltage output from the voltage detector 71. The computing unit 88d outputs the obtained second threshold voltage Vthu to the first comparator 88.

  As shown in FIG. 5, the first comparator 88 has a first input terminal 88a connected to the second fixed capacitor Cfl, a second input terminal 88b connected to the computing unit 88d, and an output terminal connected to the first switch Svu. Is done. The first comparator 88 outputs a result of comparing the second threshold voltage Vthu output from the computing unit 88d and the load voltage applied to the second adjustment capacitor Cvl to the first switch Svu. For example, as illustrated in FIG. 6, the first comparator 88 outputs a switch-on signal to the first switch Svu when the load voltage is equal to or higher than the second threshold voltage Vthu (for example, between time t4 and time t5). . For example, when the load voltage is lower than the second threshold voltage Vthu (for example, between time t1 and time t4), the first comparator 88 outputs a switch-off signal to the first switch Svu.

  As in the first embodiment, the second comparator 89 has a first input terminal 89a connected to the threshold voltage calculator 87, a second input terminal 89b connected to the second fixed capacitor Cfl, and an output terminal connected to the second switch Svl. Connected to. The second comparator 89 outputs the result of comparing the first threshold voltage Vth of the second adjustment capacitor Cvl output from the threshold voltage calculator 87 and the load voltage applied to the second adjustment capacitor Cvl to the second switch Svl. To do. For example, as illustrated in FIG. 6, the second comparator 89 outputs the switch-off signal when the load voltage is equal to or higher than the first threshold voltage Vth of the second adjustment capacitor Cvl (for example, between time t3 and time t6). 2 Output to switch Svl. For example, when the load voltage is lower than the first threshold voltage Vth of the second adjustment capacitor Cvl (for example, between time t2 and time t3), the second comparator 89 outputs a switch-on signal to the second switch Svl. .

  As described above, the power receiving device 1A according to the first modification of the embodiment includes the first and second switches Svu based on the load voltage applied to either the first adjustment capacitor Cvu or the second adjustment capacitor Cvl. Svl is controlled. With this configuration, the power receiving device 1A can omit the operational amplifier 88c necessary for detecting the load voltage applied to the first adjustment capacitor Cvu, compared with the power receiving device 1 of the embodiment. Pressure resistance, and the number of parts and manufacturing costs can be reduced.

  Next, a power receiving device 1B according to Modification 2 of the embodiment will be described. The power receiving device 1B according to the modified example 2 is different from the power receiving device 1A according to the modified example 1 in that the fixed capacitor group 30 is not included. In the power receiving device 1B according to the modified example 2, as shown in FIG. 7, the first comparator 88 includes a first input terminal 88a connected to a connection point between the third diode D3 and the fourth diode D4, and a second input terminal. 88b is connected to the computing unit 88d, and the output terminal is connected to the first switch Svu. The first comparator 88 outputs a result of comparing the second threshold voltage Vthu output from the computing unit 88d and the load voltage applied to the second adjustment capacitor Cvl to the first switch Svu. As shown in FIG. 6 described above, the first comparator 88 outputs a switch-on signal to the first switch Svu when the load voltage is equal to or higher than the second threshold voltage Vthu. For example, when the load voltage is lower than the second threshold voltage Vthu, the first comparator 88 outputs a switch-off signal to the first switch Svu.

  As described above, since the power receiving device 1B according to the second modification of the embodiment does not include the fixed capacitor group 30, the number of parts and the manufacturing cost are reduced as compared with the power receiving device 1A according to the first modification. be able to.

  Next, a power receiving device 1C according to Modification 3 of the embodiment will be described. As illustrated in FIG. 8, the power receiving device 1C according to the modification 3 is different from the power receiving device 1B according to the modification 2 in that the first adjustment capacitor Cvu, the first comparator 88, and the calculator 88d are not included. . In the power receiving device 1C according to the third modification, the second comparator 89 includes a first input terminal 89a connected to the threshold voltage calculation unit 87 and a second input terminal 89b connected to the third diode D3, as in the second modification. It is connected to the connection point with the fourth diode D4, and its output terminal is connected to the second switch Svl. The second comparator 89 outputs the result of comparing the first threshold voltage Vth of the second adjustment capacitor Cvl output from the threshold voltage calculator 87 and the load voltage applied to the second adjustment capacitor Cvl to the second switch Svl. To do. As shown in FIG. 6 described above, the second comparator 89 outputs a switch-off signal to the second switch Svl when the load voltage is equal to or higher than the first threshold voltage Vth of the second adjustment capacitor Cvl. For example, when the load voltage is lower than the first threshold voltage Vth of the second adjustment capacitor Cvl, the second comparator 89 outputs a switch-on signal to the second switch Svl.

  As described above, the power receiving device 1C according to the third modification of the embodiment does not include the first adjustment capacitor Cvu, the first comparator 88, and the arithmetic unit 88d. Therefore, the power receiving device 1B according to the second modification, etc. In comparison, the number of parts and manufacturing costs can be reduced.

  In addition, although the power receiving apparatus 1, 1A, 1B, 1C demonstrated the example applied to non-contact electric power feeding, you may apply to the apparatus of the secondary side of a DCDC converter.

1, 1A, 1B, 1C Power receiving device 2c Power transmitting coil 3 Load section 11 Power receiving coil 11a One end 11b The other end 20 Bridge rectifier circuit (rectifier circuit)
40 Adjustment capacitor group (capacitor part)
50 switch unit 70 detection unit 80 control unit Cvu first adjustment capacitor (first capacitor)
Cvl second adjustment capacitor (second capacitor)
D1 1st diode D2 2nd diode D3 3rd diode D4 4th diode Svu 1st switch Svl 2nd switch

Claims (4)

A power receiving coil that receives the AC power transmitted in a contactless manner from a power transmission coil that transmits AC power; and
A rectifier circuit that rectifies the AC power received by the power receiving coil into DC power and supplies the DC power to a load unit;
A capacitor unit connected in parallel to the rectifier circuit and charging the DC power supplied from the rectifier circuit to the load unit;
A switch unit that switches on or off the connection between the capacitor unit and the rectifier circuit;
A detection unit for detecting the voltage and current of the DC power supplied to the load unit;
A control unit for controlling the switch unit based on the voltage and the current detected by the detection unit and adjusting a charge amount charged in the capacitor unit;
A power receiving device comprising: The rectifier circuit includes a first diode, a second diode, a third diode, and a fourth diode, the capacitor unit includes a first capacitor and a second capacitor, and the switch unit includes 1 switch and 2nd switch,
In the rectifier circuit, the first and second diodes are connected in series in the forward direction, the third and fourth diodes are connected in series in the forward direction, and the first and second diodes in the forward direction and The third and fourth diodes in the forward direction are connected in parallel;
The capacitor unit has the first capacitor connected in parallel to the third diode, the second capacitor connected in parallel to the fourth diode,
In the switch unit, the first switch is connected between a connection point of the third diode and the load unit and the first capacitor, and the second switch is connected to a connection point of the fourth diode and the load unit. Connected to the second capacitor;
The power receiving coil has one end of the power receiving coil connected to a connection point between the first diode and the second diode, and the other end of the power receiving coil connected to a connection point between the third diode and the fourth diode. And
The control unit controls the first switch and the second switch based on the voltage and the current detected by the detection unit, and adjusts a charge amount charged in the first capacitor and the second capacitor. The power receiving device according to claim 1.   The power reception device according to claim 2, wherein the control unit controls the first switch and the second switch based on a load voltage applied to either the first capacitor or the second capacitor.   The control unit relatively increases the charge amount of the capacitor unit when the impedance of the load unit increases, and relatively decreases the charge amount of the capacitor unit when the impedance of the load unit decreases. The power receiving device according to claim 1.

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