JP2014060864A - Power reception apparatus and non-contact power transmission device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power reception apparatus capable of improving efficiency of a rectification unit, and a non-contact power transmission device having the power reception apparatus.SOLUTION: A non-contact power transmission device 10 comprises: a ground side apparatus 11 installed on the ground; and a vehicle side apparatus 21 mounted on a vehicle. The ground side apparatus 11 comprises a high-frequency power supply 12 and a power transmitter 13 to which high-frequency power is input from the high-frequency power supply 12. The vehicle side apparatus 21 comprises: a power receiver 23 capable of receiving high-frequency power from the power transmitter 13 in a non-contact manner; a rectifier 24 for rectifying the high-frequency power received by the power receiver 23; a DC/DC converter 25 for converting a voltage value of DC power rectified by the rectifier 24, where a load impedance Z1, which is impedance from an output end of the rectifier 24 to the vehicle battery 22, is adjusted so that efficiency of the rectifier 24 is high.

Description

  The present invention relates to a power receiving device and a non-contact power transmission apparatus.

  2. Description of the Related Art Conventionally, as a non-contact power transmission device that does not use a power cord or a power transmission cable, for example, a device using magnetic field resonance is known. For example, the non-contact power transmission device of Patent Literature 1 includes a power transmission device having an AC power source and a primary-side resonance coil to which AC power is input from the AC power source. The non-contact power transmission device includes a power receiving device having a primary side resonance coil and a secondary side resonance coil capable of magnetic field resonance. Then, AC power is transmitted from the power transmission device to the power reception device by magnetic resonance between the primary side resonance coil and the secondary side resonance coil. The AC power transmitted to the power receiving device is rectified into DC power by a rectifier provided in the power receiving device, and input to the vehicle battery. Thereby, the vehicle battery is charged.

JP 2009-106136 A

  In the non-contact power transmission apparatus as described above, improvement in transmission efficiency is required. As a parameter on which the transmission efficiency depends, for example, there is an efficiency of a rectifier. In the non-contact power transmission device, there is still room for improvement in the efficiency of the rectifier.

In addition, the situation mentioned above is not restricted to what performs non-contact power transmission by magnetic field resonance, The same is true for the one that performs non-contact power transmission by electromagnetic induction.
This invention is made | formed in view of the situation mentioned above, and aims at providing the non-contact electric power transmission apparatus provided with the power receiving apparatus which can aim at the improvement of the efficiency of a rectification | straightening part, and the power receiving apparatus.

  To achieve the above object, the invention according to claim 1 is directed to a secondary coil capable of receiving the AC power in a contactless manner from a power transmission device having a primary coil to which AC power is input, and the secondary coil. Provided between the rectifying unit and the load in a power receiving device comprising: a rectifying unit that rectifies AC power received by the side coil; and a load to which the DC power rectified by the rectifying unit is input. And an adjustment unit that adjusts an impedance from the output terminal of the rectifying unit to the load so that the efficiency of the rectifying unit is increased.

  According to this invention, the impedance from the output terminal of the rectifying unit to the load is adjusted by the adjusting unit so as to increase the efficiency of the rectifying unit. Thereby, the efficiency of a rectification | straightening part can be aimed at.

  According to a second aspect of the present invention, the adjusting unit increases an impedance from the output terminal of the rectifying unit to the load in a state where a voltage value applied to an element constituting the rectifying unit is smaller than a withstand voltage value. It is characterized by being. According to this invention, the impedance from the output terminal of the rectifier unit to the load is increased in a state where the voltage value applied to the elements constituting the rectifier unit is smaller than the withstand voltage value. As a result, the current value of the current flowing through the rectification unit is reduced within a range where an excessive voltage is not applied to the elements constituting the rectification unit, and the power consumed by the rectification unit is reduced. Therefore, it is possible to improve the efficiency of the rectification unit while suppressing malfunction of the elements constituting the rectification unit.

  According to a third aspect of the present invention, the impedance of the load varies, and the adjustment unit outputs the output of the rectification unit so that the efficiency of the rectification unit increases according to the variation of the impedance of the load. The impedance from the end to the load is adjusted. According to this invention, by adjusting the impedance from the output terminal of the rectifier unit to the load so that the efficiency of the rectifier unit becomes high according to the fluctuation of the impedance of the load, A decrease in efficiency can be suppressed.

  The invention according to claim 4 is a power transmission device having a primary side coil to which AC power is input, a secondary side coil capable of receiving the AC power in a non-contact manner from the primary side coil, and the secondary side coil. A non-contact power transmission apparatus comprising: a rectifying unit that rectifies the AC power received by the power supply unit; and a power receiving device having a load to which the DC power rectified by the rectifying unit is input. The power receiving device according to any one of 1 to 3 is provided. According to this invention, in the non-contact power transmission device, the efficiency of the rectification unit can be improved.

  According to the present invention, it is possible to improve the efficiency of the rectification unit.

The circuit diagram which shows the electric constitution of a non-contact electric power transmission apparatus.

Hereinafter, a non-contact power transmission apparatus (non-contact power transmission system) according to the present invention will be described.
As shown in FIG. 1, the non-contact power transmission apparatus 10 includes a ground side device 11 provided on the ground and a vehicle side device 21 mounted on the vehicle. The ground side device 11 corresponds to a power transmission (primary side) device, and the vehicle side device 21 corresponds to a power reception (secondary side) device.

  The ground side device 11 includes a high frequency power source 12 (AC power source) capable of outputting high frequency power (AC power) having a predetermined frequency. The high frequency power source 12 is configured to convert system power input from a system power source as infrastructure into high frequency power and output the high frequency power.

  The high-frequency power output from the high-frequency power source 12 is transmitted to the vehicle-side device 21 in a non-contact manner, and used for charging the vehicle battery 22 as a load provided in the vehicle-side device 21. Specifically, the non-contact power transmission device 10 is provided in the vehicle-side device 21 and the power transmitter 13 provided in the ground-side device 11 as a device that performs power transmission between the ground-side device 11 and the vehicle-side device 21. The power receiver 23 is provided.

  The power transmitter 13 and the power receiver 23 have the same configuration, and both are configured to be capable of magnetic field resonance. Specifically, the power transmitter 13 includes a resonance circuit including a primary coil 13a and a primary capacitor 13b connected in parallel. The power receiver 23 is composed of a resonance circuit including a secondary coil 23a and a secondary capacitor 23b connected in parallel. Both resonance frequencies are set to be the same.

  According to such a configuration, when high-frequency power is input to the power transmitter 13 (primary coil 13a), the power transmitter 13 and the power receiver 23 (secondary coil 23a) undergo magnetic field resonance. As a result, the power receiver 23 receives a part of the energy of the power transmitter 13. That is, the power receiver 23 receives high frequency power from the power transmitter 13.

  The vehicle-side device 21 is provided with a rectifier 24 as a rectifying unit that rectifies high-frequency power received by the power receiver 23. Further, the vehicle side device 21 is provided with a DC / DC converter 25 as an adjustment unit that converts the voltage value of the DC power rectified by the rectifier 24 into a different voltage value and outputs it to the vehicle battery 22. Yes. When the DC power output from the DC / DC converter 25 is input to the vehicle battery 22, the vehicle battery 22 is charged.

  Incidentally, the vehicle battery 22 is configured by connecting, for example, a plurality of battery cells, and the impedance ZL of the vehicle battery 22 varies according to the power value and the charge amount of the input DC power. That is, the vehicle battery 22 is a variable load in which the impedance ZL varies depending on the situation.

  The ground side device 11 is provided with a power supply side controller 14 that performs various controls of the ground side device 11. The power supply side controller 14 includes a power control unit 14 a that determines whether or not high frequency power is output from the high frequency power supply 12 and controls the power value of the high frequency power output from the high frequency power supply 12. The power control unit 14a is configured to be able to switch the high-frequency power output from the high-frequency power source 12 between the charging power and the pushing charging power having a power value different from the power value of the charging power. . The push-in charging power is high-frequency power set so that DC power having a power value suitable for push-in charging is input to the vehicle battery 22. Push-in charging is a charging mode that is performed so as to compensate for capacity variations of the battery cells constituting the vehicle battery 22.

  The vehicle-side device 21 is provided with a vehicle-side controller 26 configured to be able to perform wireless communication with the power supply-side controller 14. The non-contact power transmission apparatus 10 starts or ends power transmission through the exchange of information between the controllers 14 and 26.

  The vehicle-side device 21 is provided with a detection sensor 27 that detects the charge amount of the vehicle battery 22. The detection sensor 27 transmits the detection result to the vehicle-side controller 26. Thereby, the vehicle-side controller 26 can grasp the charge amount of the vehicle battery 22.

  Incidentally, the vehicle-side controller 26 transmits a notification to that effect to the power-side controller 14 when the detection sensor 27 detects that the charge amount of the vehicle battery 22 has reached a predetermined threshold amount. The power control unit 14a of the power supply side controller 14 switches the output power of the high frequency power supply 12 from the charging power to the charging power based on the reception of the notification. In other words, it can be said that the push-in charging is a charging mode performed when the charging amount of the vehicle battery 22 becomes a threshold amount.

  A measuring device 28 is provided between the rectifier 24 and the DC / DC converter 25 of the vehicle-side device 21. The measuring device 28 measures a load impedance Z1 that is an impedance from the output terminal of the rectifier 24 to the vehicle battery 22 and outputs the measurement result to the vehicle-side controller 26.

  The non-contact power transmission apparatus 10 includes a primary side impedance converter 31 provided in the ground side device 11 and a secondary side impedance converter 32 provided in the vehicle side device 21. The primary side impedance converter 31 is provided between the high frequency power supply 12 and the power transmitter 13. The primary side impedance converter 31 is comprised, for example by LC circuit, and the constant (inductance and capacitance) is comprised fixed. The secondary impedance converter 32 is provided between the power receiver 23 and the rectifier 24. The secondary side impedance converter 32 is configured by an LC circuit, for example, and the constants (inductance and capacitance) are fixed. The constant can be said to be an impedance or a conversion ratio.

Next, circuit configurations of the rectifier 24 and the DC / DC converter 25 will be described.
The rectifier 24 is configured to receive the high frequency power received by the power receiver 23, and rectifies and outputs the input high frequency power. Specifically, the rectifier 24 includes a diode bridge 41 that performs full-wave rectification of the high-frequency power and a smoothing circuit 42 that smoothes the high-frequency power (pulsating power) that has been full-wave rectified. The diode bridge 41 reverses the negative component of the high frequency power and transmits it to the smoothing circuit 42 by a plurality (two) of positive side diodes 41 a used for transmitting the positive component of the high frequency power to the smoothing circuit 42. A plurality of (two) negative diodes 41b used.

  The smoothing circuit 42 includes a choke coil 42a and two smoothing capacitors 42b and 42c. The choke coil 42 a is connected to the diode bridge 41 in series. Specifically, the choke coil 42 a has one end connected to the output end of the diode bridge 41 and the other end connected to the output end of the rectifier 24. Each of the smoothing capacitors 42b and 42c is connected in parallel to the choke coil 42a. Specifically, each of the smoothing capacitors 42b and 42c has one end connected to the choke coil 42a and the other end grounded. According to such a configuration, the pulsating power that is the output power from the diode bridge 41 is smoothed by the smoothing circuit 42, whereby the pulsating power is rectified to DC power.

  The DC / DC converter 25 is a so-called non-insulated step-down chopper, and includes a switching element 51, a diode 52, a coil 53 connected in series to the switching element 51, and a capacitor connected in parallel to the coil 53. 54.

  The switching element 51 is composed of, for example, an n-type power MOSFET. The drain of the switching element 51 is connected to the input end of the DC / DC converter 25 and the output end of the rectifier 24 via the measuring device 28. The source of the switching element 51 is connected to one end of the coil 53 and to the cathode of the diode 52. The anode of the diode 52 is grounded. The other end of the coil 53 is connected to the vehicle battery 22 via the output end of the DC / DC converter 25. One end of the capacitor 54 is connected to the other end of the coil 53, and the other end of the capacitor 54 is grounded.

  According to this configuration, when the switching element 51 is periodically switched (ON / OFF, chopping), voltage value conversion corresponding to the ON / OFF duty ratio of the switching element 51 is performed. In this case, the load impedance Z1 depends on the on / off duty ratio of the switching element 51. That is, the duty ratio defines the load impedance Z1.

  The relationship between the duty ratio and the load impedance Z 1 will be described in detail. The voltage value on the output side of the DC / DC converter 25 is the battery voltage value of the vehicle battery 22, and the battery voltage value is uniquely determined by the specifications of the vehicle battery 22. It is decided. On the other hand, both the voltage value and the current value of the DC power input to the DC / DC converter 25 vary according to the duty ratio, and as a result, the load impedance Z1, which is the ratio between the voltage value and the current value, varies. . Therefore, the duty ratio defines the load impedance Z1.

  The vehicle-side controller 26 includes a duty ratio adjustment unit 26 a that adjusts (controls) the on / off duty ratio of the switching element 51. The duty ratio adjustment unit 26 a adjusts the duty ratio by controlling the gate voltage of the switching element 51. Specifically, the duty ratio adjustment unit 26a outputs a pulse signal having a frequency higher than the frequency of the high-frequency power to the gate of the switching element 51 and performs pulse width modulation of the pulse signal, whereby the duty ratio is adjusted. Adjust. If attention is paid to the fact that the load impedance Z1 varies according to the duty ratio, it can be said that the duty ratio adjustment unit 26a adjusts the load impedance Z1 by adjusting the duty ratio.

  The duty ratio adjustment unit 26a adjusts the duty ratio so as to increase the efficiency of the rectifier 24 while considering the withstand voltage values of the elements (for example, the diodes 41a and 41b and the smoothing capacitors 42b and 42c) constituting the rectifier 24. To do. Specifically, the efficiency of the rectifier 24 increases as the value of the current flowing through the rectifier 24 (such as the positive side diode 41a or the negative side diode 41b) decreases. The current value of the current flowing through the rectifier 24 decreases as the load impedance Z1 increases. However, when the load impedance Z1 is excessively increased, the voltage value applied to each of the elements constituting the rectifier 24 may be higher than the withstand voltage value.

  On the other hand, the duty ratio adjustment unit 26a adjusts the duty ratio so that the load impedance Z1 becomes large in a state (within a range) where the voltage value applied to each element constituting the rectifier 24 is smaller than the withstand voltage value. To do.

  Further, the duty ratio adjusting unit 26a adjusts the duty ratio in accordance with the fluctuation of the impedance ZL of the vehicle battery 22. Specifically, the duty ratio adjustment unit 26a configures the rectifier 24 based on the measurement result of the measuring instrument 28 when the high-frequency power output from the high-frequency power supply 12 is switched from the charging power to the indenting charging power. The duty ratio is adjusted so that the load impedance Z1 is as large as possible in a state where the voltage value applied to each element is smaller than the withstand voltage value.

  Here, when the load impedance Z1 set as large as possible is the maximum load impedance in a state where the voltage value applied to each element constituting the rectifier 24 is smaller than the withstand voltage value, the high frequency output from the high frequency power supply 12 is obtained. Depending on the power value of the power, the maximum load impedance can vary.

  Based on the measurement result of the measuring instrument 28, the duty ratio adjustment unit 26a adjusts the duty ratio so that the load impedance Z1 approaches, preferably coincides with, the maximum load impedance.

  Note that the duty ratio at which the load impedance Z1 is the maximum load impedance in a situation where charging power is output from the high-frequency power source 12 is defined as a first specific duty ratio. Similarly, the duty ratio at which the load impedance Z1 becomes the maximum load impedance in a situation where the inrush charging power is output from the high-frequency power source 12 is set as the second specific duty ratio. Then, based on the fact that the high-frequency power output from the high-frequency power supply 12 is switched between the charging power and the push-in charging power, the duty ratio adjustment unit 26a changes the duty ratio to the first specific duty ratio and the second specific duty. It can be said that the ratio is switched to the ratio.

Next, the operation of this embodiment will be described.
The load impedance Z1 is adjusted by the DC / DC converter 25 so that the efficiency of the rectifier 24 is increased. Specifically, the on / off duty ratio of the switching element 51 is adjusted such that the load impedance Z1 is increased in a state where the voltage value applied to each element constituting the rectifier 24 is smaller than the withstand voltage value. Thereby, the efficiency of the rectifier 24 is improved.

  When the power value of the high-frequency power output from the high-frequency power source 12 varies, the duty ratio is adjusted so that the load impedance Z1 becomes the maximum load impedance in response to the variation. Thereby, even if it is a case where the electric power value of the high frequency electric power output from the high frequency power supply 12 is fluctuate | varied, the fall of the efficiency of the rectifier 24 can be suppressed, preventing the malfunctioning of each element which comprises the rectifier 24. FIG.

According to the embodiment described in detail above, the following excellent effects are obtained.
(1) A DC / DC converter that adjusts a load impedance Z1 that is an impedance from the output terminal of the rectifier 24 to the vehicle battery 22 so that the efficiency of the rectifier 24 is increased between the rectifier 24 and the vehicle battery 22. 25 was provided. Thereby, the efficiency of the rectifier 24 can be improved.

  (2) Specifically, the load impedance Z1 is increased in a state where the voltage value applied to each element constituting the rectifier 24 is smaller than the withstand voltage value. As a result, the current value of the current flowing through the rectifier 24 is reduced within a range where an excessive voltage is not applied to each element constituting the rectifier 24. Therefore, it is possible to improve the efficiency of the rectifier 24 while suppressing malfunction of each element constituting the rectifier 24.

  (3) The on / off duty ratio of the switching element 51 of the DC / DC converter 25 is adjusted. As a result, the load impedance Z1 can be adjusted without providing a high withstand voltage variable capacitor or variable inductor.

  (4) The duty ratio is adjusted in response to fluctuations in the power value of the high-frequency power output from the high-frequency power source 12. Specifically, the duty ratio was adjusted so that the load impedance Z1 becomes the maximum load impedance. Thereby, the fall of the efficiency of the rectifier 24 accompanying the fluctuation | variation of the electric power value of the high frequency electric power output from the high frequency power supply 12 can be suppressed.

In addition, you may change the said embodiment as follows.
In the embodiment, the duty ratio is adjusted so that the load impedance Z1 becomes the maximum load impedance in response to the fluctuation of the power value of the high-frequency power output from the high-frequency power source 12, but this is not limited thereto. Absent. For example, the load impedance Z1 may be constant at a specific value by adjusting the duty ratio in accordance with fluctuations in the power value of the high-frequency power output from the high-frequency power source 12. In short, what is necessary is that the efficiency of the rectifier 24 can be made higher than the configuration in which the duty ratio is not adjusted in response to fluctuations in the power value of the high-frequency power output from the high-frequency power source 12. If the efficiency of the rectifier 24 is increased, the maximum load that can vary according to the power value of the high-frequency power (charging power or push-charging power) output from the high-frequency power source 12 as the “specific value”, for example. The minimum impedance value may be used.

  In the embodiment, as the load impedance Z1 is adjusted, the on / off duty ratio of the DC / DC converter 25, specifically the switching element 51, is adopted. However, the load impedance Z1 is not limited to this as long as the load impedance Z1 can be changed. Absent.

  In the embodiment, the configuration follows the fluctuation of the power value of the high-frequency power output from the high-frequency power source 12 based on the measurement result of the measuring instrument 28, but is not limited thereto. For example, the measuring device 28 may be omitted. When there is no change in the relative position of each coil 13a, 23a, the second specific duty ratio can be grasped (calculated) in advance. Therefore, the second specific duty ratio can be stored in a predetermined memory. it can. In this case, when the high-frequency power output from the high-frequency power supply 12 is switched from the charging power to the indentation charging power, the duty ratio adjusting unit 26a refers to the memory to specify the second specific duty ratio, The duty ratio may be adjusted based on the identification result.

The circuit configuration of the rectifier 24 is not limited to that of the embodiment, and is arbitrary as long as it can be rectified. For example, a PFC circuit that performs rectification and power factor improvement may be used.
Similarly, the circuit configuration of the DC / DC converter 25 is not limited to that of the embodiment, and is arbitrary. For example, a boost type may be used.

  In the embodiment, as an opportunity to adjust the duty ratio, switching of the power value of the high-frequency power output from the high-frequency power source 12 (switching from charging power to push-in charging power) is employed, but is not limited thereto. . For example, the measuring instrument 28 periodically measures the load impedance Z1, and the duty ratio is adjusted when the measured load impedance Z1 deviates from a predetermined allowable value with respect to the maximum load impedance. It is good.

  In the embodiment, the constants of the impedance converters 31 and 32 are fixed, but are not limited to this, and may be variable. In this case, the constants of the impedance converters 31 and 32 may be variably controlled in accordance with fluctuations in the relative positions of the coils 13a and 23a. Thereby, even if it is a case where the position shift of each coil 13a and 23a has generate | occur | produced, high transmission efficiency can be maintained.

  The relative positions of the coils 13a and 23a include not only the distance between the coils 13a and 23a, but also the axial direction of the coils 13a and 23a, the manner in which the coils 13a and 23a are superposed, and the like. . For example, in a configuration in which the power transmitter 13 and the power receiver 23 are arranged in the vertical direction, the superposition mode of the coils 13a and 23a is that of the primary side coil 13a and the secondary side coil 23a when viewed from above. Misalignment is possible.

  In the configuration in which the constants of the impedance converters 31 and 32 are variable, for example, a constant resistance value (impedance) is provided between the secondary impedance converter 32 and the rectifier 24 regardless of the power value of the input power. A fixed resistance is provided. In addition, a relay for switching the connection destination of the secondary side impedance converter 32 between the fixed resistor and the rectifier 24 is provided. And when performing variable control of the constant of each impedance converter 31 and 32, the connecting point of the secondary side impedance converter 32 is made into fixed resistance.

  Incidentally, when variable control of the constants of the impedance converters 31 and 32 is performed, adjustment power having a power value smaller than that of charging power may be output from the high frequency power supply 12. In this case, the resistance value of the fixed resistor may be the same as the impedance from the input terminal of the rectifier 24 to the vehicle battery 22 when the load impedance Z1 is the maximum load impedance.

  ○ There is a specific resistance value in the real part of the impedance from the output terminal of the power receiver 23 (secondary coil 23a) to the vehicle battery 22 that provides a relatively high transmission efficiency compared to other resistance values. To do. In other words, the real part of the impedance from the output terminal of the power receiver 23 to the vehicle battery 22 has a specific resistance value (second resistance value) at which transmission efficiency is higher than a predetermined resistance value (first resistance value). Exists. Specifically, if a virtual load is provided at the input end of the power transmitter 13, the resistance value of the virtual load is Ra1, and the resistance from the power receiver 23 (specifically, the output end of the power receiver 23) to the virtual load. When the value is Rb1, the specific resistance value is √ (Ra1 × Rb1).

  Correspondingly, the secondary impedance converter 32 has an impedance from the input end of the rectifier 24 to the vehicle battery 22 so that the impedance from the output end of the power receiver 23 to the vehicle battery 22 approaches a specific resistance value. The impedance may be converted.

  In addition, the primary side impedance converter 31 calculates the impedance from the input end of the power transmitter 13 to the vehicle battery 22 in a situation where the impedance from the output end of the power receiver 23 to the vehicle battery 22 approaches a specific resistance value. Impedance conversion. For example, the primary-side impedance converter 31 is configured so that the impedance from the output terminal of the high-frequency power source 12 to the vehicle battery 22 is an impedance at which high-frequency power having a desired power value is obtained. To impedance of the vehicle battery 22 may be converted.

  Here, when the load impedance Z1 is set in consideration of the efficiency of the rectifier 24, it is assumed that the impedance from the input terminal of the rectifier 24 to the vehicle battery 22 deviates from the specific resistance value. On the other hand, by providing the secondary side impedance converter 32 as described above, the efficiency of the rectifier 24 can be improved while the impedance from the output terminal of the power receiver 23 to the vehicle battery 22 is brought close to the specific resistance value. Can be planned.

  Incidentally, when the maximum load impedance fluctuates with the fluctuation of the power value of the high frequency power output from the high frequency power supply 12, the impedance from the input terminal of the rectifier 24 to the vehicle battery 22 fluctuates with the fluctuation. Then, the impedance from the output end of the power receiver 23 to the vehicle battery 22 deviates from the specific resistance value.

  On the other hand, by variably controlling the constant (conversion ratio) of the secondary side impedance converter 32 corresponding to the fluctuation of the maximum load impedance, the impedance from the output terminal of the power receiver 23 to the vehicle battery 22 is changed. It is good also as a structure which maintains the state which approached the specific resistance value.

  If the load impedance Z1 is excessively increased in consideration of the efficiency of the rectifier 24, the difference between the impedance from the input terminal of the rectifier 24 to the vehicle battery 22 and the specific resistance value increases. Then, the conversion ratio of the secondary impedance converter 32 becomes excessively large. In this case, the conversion ratio may not be realistic or a special element may need to be used. For this reason, you may set load impedance Z1 corresponding to the difference with a specific resistance value so that the conversion ratio of the secondary side impedance converter 32 may be settled in the predetermined range.

  The primary-side impedance converter 31 is connected to the vehicle battery 22 from the input end of the power transmitter 13 so that the impedance from the output end of the high-frequency power source 12 to the vehicle battery 22 matches the output impedance of the high-frequency power source 12. Impedance conversion may be performed for the impedance up to.

  Similarly, the secondary impedance converter 32 includes a rectifier 24 so that the impedance from the output terminal of the power receiver 23 to the high-frequency power source 12 matches the impedance from the output terminal of the power receiver 23 to the vehicle battery 22. The impedance from the input terminal to the vehicle battery 22 may be impedance-converted.

  The specific configuration of each of the impedance converters 31 and 32 is arbitrary. For example, a π-type or T-type LC circuit may be used. Further, the present invention is not limited to the LC circuit, and a transformer or the like may be used.

  In the embodiment, one impedance converter is provided for each of the ground-side device 11 and the vehicle-side device 21, but the present invention is not limited to this, and two are provided for either or both of the ground-side device 11 and the vehicle-side device 21. An impedance converter may be provided one by one.

Further, either one or both of the primary side impedance converter 31 and the secondary side impedance converter 32 may be omitted.
The high frequency power supply 12 may be any of a power source, a voltage source, and a current source.

  In the embodiment, the vehicle battery 22 whose impedance ZL varies is used as the load to which the DC power rectified by the rectifier 24 is input. However, the present invention is not limited to this, and other components may be used. In this case, a load having a constant impedance regardless of the power value of the input power may be adopted as the load.

The voltage waveform of the high-frequency power output from the high-frequency power source 12 is arbitrary such as a pulse waveform or a sine wave.
○ The high frequency power supply 12 may be omitted. In this case, system power is input to the power transmitter 13.

In the embodiment, the capacitors 13b and 23b are provided, but these may be omitted. In this case, magnetic field resonance is performed using the parasitic capacitances of the coils 13a and 23a.
In the embodiment, the resonance frequency of the power transmitter 13 and the resonance frequency of the power receiver 23 are set to be the same. However, the present invention is not limited to this, and may be different within a range in which power transmission is possible.

In the embodiment, magnetic field resonance is used in order to realize non-contact power transmission. However, the present invention is not limited to this, and electromagnetic induction may be used.
In embodiment, the non-contact electric power transmission apparatus 10 was applied to the vehicle, However, It is not restricted to this, You may apply to another apparatus. For example, it may be applied to charge a battery of a mobile phone.

  The power transmitter 13 may have a configuration including a resonance circuit including a primary side coil 13a and a primary side capacitor 13b and a primary side induction coil coupled to the resonance circuit by electromagnetic induction. In this case, the resonant circuit is configured to receive high frequency power from the primary induction coil by electromagnetic induction. Similarly, the power receiver 23 includes a resonance circuit including a secondary coil 23a and a secondary capacitor 23b, and a secondary induction coil coupled to the resonance circuit by electromagnetic induction. High frequency power may be extracted from the resonance circuit of the power receiver 23 using an induction coil.

Next, the technical idea that can be grasped from the above embodiment and other examples will be described below.
(A) The rectifying unit includes a diode,
The power receiving device according to claim 1, wherein the adjustment unit increases an impedance from an output terminal of the rectification unit to the load so that a current value of a current flowing through the diode is reduced.

  (B) The adjusting unit includes a switching element that periodically switches, and adjusts an impedance from an output terminal of the rectifying unit to the load by adjusting an on / off duty ratio of the switching element. The power receiving device according to any one of claims 1 to 3 and the technical idea (A).

  DESCRIPTION OF SYMBOLS 10 ... Non-contact electric power transmission apparatus, 11 ... Ground side apparatus (power transmission apparatus), 12 ... High frequency power supply, 13a ... Primary side coil, 21 ... Vehicle side apparatus (power receiving apparatus), 22 ... Vehicle battery (load), 23a ... secondary coil, 24 ... rectifier, 25 ... DC / DC converter, 28 ... measuring instrument, 31 ... primary impedance converter, 32 ... secondary impedance converter, 41 ... diode bridge, 51 ... switching element, Z1: Load impedance.

Claims (4)

A secondary coil capable of receiving the AC power in a contactless manner from a power transmission device having a primary coil to which AC power is input;
A rectifying unit that rectifies AC power received by the secondary coil;
A load to which DC power rectified by the rectifier is input;
In the power receiving device with
The power receiving device includes an adjustment unit that is provided between the rectification unit and the load and adjusts an impedance from an output terminal of the rectification unit to the load so that the efficiency of the rectification unit is increased. machine.   The adjusting unit is configured to increase an impedance from an output terminal of the rectifying unit to the load in a state where a voltage value applied to an element constituting the rectifying unit is smaller than a withstand voltage value. The power receiving device according to claim 1. The load has a variable impedance,
The said adjustment part adjusts the impedance from the output terminal of the said rectification part to the said load so that the efficiency of the said rectification part may become high according to the fluctuation | variation of the impedance of the said load. Item 3. The power receiving device according to Item 2. A power transmission device having a primary coil to which AC power is input;
A secondary coil that can receive the AC power in a non-contact manner from the primary coil, a rectifier that rectifies the AC power received by the secondary coil, and a DC power that is rectified by the rectifier A power receiving device having an input load;
In a non-contact power transmission device comprising:
A non-contact power transmission device comprising the power receiving device according to claim 1 as the power receiving device.