JP2015109725A - Power reception equipment and non-contact power transmission device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide power reception equipment and a non-contact power transmission device capable of suppressing excessive exothermic heat in an impedance converter unit.SOLUTION: A non-contact power transmission device 10 includes: an AC power supply 12 capable of outputting AC power; a primary side coil 13a to which the AC power is input; a secondary side coil 23a capable of receiving the AC power from the primary side coil 13a in a contactless manner; and a rectifier 24 for rectifying the AC power received by the secondary side coil 23a. The non-contact power transmission device 10 further includes: a DC/DC converter 25 for converting the voltage value of DC power obtained by the rectification by the rectifier 24; and a vehicle battery 22 to which the DC power having the voltage value converted by the DC/DC converter 25 is input.

Description

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

  As a non-contact power transmission device that does not use a power cord or a power transmission cable, for example, a power transmission device having a primary coil to which AC power is input and a secondary side that can receive AC power in a non-contact manner from the primary coil What is provided with the power receiving apparatus which has a coil is known (for example, refer patent document 1). In such a non-contact power transmission device, AC power is transmitted from a power transmitting device to a power receiving device in a non-contact manner, for example, by magnetic resonance between the primary side coil and the secondary side coil.

  Moreover, the power receiving apparatus described in Patent Document 1 includes an AC / DC conversion unit that converts AC power received by the secondary coil into DC power. When the DC power converted by the AC / DC converter is input to the battery, the battery is charged.

JP 2009-106136 A

  Here, for example, an impedance conversion unit having a switching element is provided in the AC / DC conversion unit, and the input impedance of the AC / DC conversion unit can be set to a desired value by periodically turning on and off the switching element. Conceivable. In this case, it is assumed that the impedance converter generates heat. If the impedance converter generates excessive heat, there may be inconveniences such as the input impedance of the AC / DC converter deviating from a desired value.

  The objective of this invention is made | formed in view of the situation mentioned above, and is providing the power receiving apparatus and non-contact electric power transmission apparatus which can suppress the excessive heat_generation | fever of an impedance conversion part.

  The power receiving device that achieves the above object is capable of receiving the AC power in a non-contact manner from a power transmitting device having a primary coil to which AC power is input, and the AC that is input to the primary coil. A secondary coil that can receive power in a contactless manner, and an AC / DC converter that converts AC power received by the secondary coil into DC power, wherein the AC / DC converter A first impedance conversion unit that includes one switching element and performs impedance conversion by periodically turning on and off the first switching element; and a second switching element that periodically turns on and off. A second impedance converter that performs impedance conversion, and a measurement unit that measures the temperature of the first impedance converter. The dance conversion unit and the second impedance conversion unit are connected in parallel, and the temperature of the first impedance conversion unit measured by the measurement unit in a situation where the first switching element is periodically turned on and off is obtained. When the temperature exceeds a predetermined threshold temperature, the second switching element is periodically turned on and off.

  According to such a configuration, when the temperature of the first impedance converter becomes equal to or higher than the threshold temperature, the second switching element is periodically turned on / off. Thereby, since a current flows through the second impedance conversion unit, a current value flowing through the first impedance conversion unit becomes small. Accordingly, since the amount of heat generated in the first impedance conversion unit is reduced, excessive heat generation in the first impedance conversion unit can be suppressed.

  Regarding the power receiving device, the periodic switching on and off of the first switching element may be continued even when the temperature of the first impedance converter measured by the measuring unit is equal to or higher than the threshold temperature. . According to such a configuration, even when the temperature of the first impedance conversion unit is equal to or higher than the threshold temperature, the first switching element and the second impedance are continuously switched on and off because the first switching element is periodically turned on and off. Current will flow through both of the converters. As a result, the current can be distributed, and it is possible to avoid a situation in which only one of the impedance converters excessively generates heat.

  In the power receiving device, the first impedance conversion unit may include a semiconductor element, and the measurement unit may measure the temperature of the semiconductor element as the temperature of the first impedance conversion unit. According to such a configuration, it is possible to prevent the temperature of the semiconductor element from becoming a temperature at which the semiconductor element cannot operate normally by performing on / off control of the second switching element based on the temperature of the semiconductor element. The semiconductor element includes a first switching element.

  For the power receiving device, when the threshold temperature is a first threshold temperature, the first impedance measured by the measurement unit in a situation where both the first switching element and the second switching element are periodically turned on and off. When the temperature of the conversion unit becomes the second threshold temperature lower than the first threshold temperature, the periodic switching on and off of the second switching element may be stopped. According to this configuration, when the temperature of the first impedance converter is relatively low, the periodic switching on / off of the second switching element is stopped, so that the loss can be reduced by the switching loss of the second switching element. . Therefore, in a situation where the temperature of the first impedance conversion unit is relatively high, the temperature of the first impedance conversion unit is suppressed by periodically turning on and off both switching elements, while the first impedance conversion unit In a situation where the temperature is relatively low, loss can be reduced by stopping the on / off of the second switching element periodically.

  For the power receiving device, the AC / DC converter is a rectifier that rectifies AC power received by the secondary coil, and DC power that is rectified by the rectifier is input, A DC / DC converter having a first impedance converter and the second impedance converter, wherein the first impedance converter is a first chopper circuit having the first switching element, and the second impedance converter. The unit may be a second chopper circuit having the second switching element. According to such a configuration, it is possible to suppress the first chopper circuit from excessively generating heat by operating the second chopper circuit when the temperature of the first chopper circuit becomes equal to or higher than the threshold temperature.

  A non-contact power transmission device that achieves the above object includes a primary coil to which AC power is input, a secondary coil that can receive the AC power input to the primary coil in a non-contact manner, An AC / DC converter that converts AC power received by the secondary coil into DC power, and the AC / DC converter includes a first switching element, and the first switching element is periodic. A first impedance conversion unit that performs impedance conversion by turning on and off, a second impedance conversion unit that includes a second switching element, and that performs impedance conversion by periodically turning on and off the second switching element; A measurement unit that measures the temperature of the one impedance conversion unit, and the first impedance conversion unit and the second impedance conversion unit are in parallel The contactless power transmission device includes a control unit that performs on / off control of the first switching element and the second switching element, and the control unit periodically turns on and off the first switching element. The second switching element is periodically turned on and off when the temperature of the first impedance conversion unit measured by the measurement unit is equal to or higher than a predetermined threshold temperature.

  According to such a configuration, when the temperature of the first impedance converter becomes equal to or higher than the threshold temperature, the second switching element is periodically turned on / off. Thereby, since a current flows through the second impedance conversion unit, a current value flowing through the first impedance conversion unit becomes small. Accordingly, since the amount of heat generated in the first impedance conversion unit is reduced, excessive heat generation in the first impedance conversion unit can be suppressed.

  According to the present invention, excessive heat generation in the impedance converter can be suppressed.

The circuit diagram of a receiving device and a non-contact electric power transmission apparatus. The DC / DC converter and its peripheral circuit diagram. The flowchart which shows the temperature corresponding | compatible process performed with the receiving side controller. The graph which shows the temperature change of a 1st switching element.

Hereinafter, an embodiment in which a power receiving device (power receiving device) and a non-contact power transmission device (non-contact power transmission system) are applied to a vehicle will be described.
As shown in FIG. 1, the non-contact power transmission device 10 includes a power transmission device 11 (ground side device, primary side device) and a power receiving device 21 (vehicle side device, secondary side device) capable of non-contact power transmission. It has. The power transmission device 11 is provided on the ground, and the power receiving device 21 is mounted on the vehicle.

  The power transmission device 11 includes an AC power supply 12 that can output AC power having a predetermined frequency. The AC power supply 12 is configured to be able to convert the system power into AC power and output the converted AC power when the system power is input from the system power supply as the infrastructure. The AC power supply 12 is configured to be capable of outputting a plurality of types of AC power having different power values. In the present embodiment, the AC power source 12 is, for example, a voltage source.

  The AC power output from the AC power supply 12 is transmitted to the power receiving device 21 in a non-contact manner, and used for charging the vehicle battery 22 provided in the power receiving device 21. Specifically, the non-contact power transmission apparatus 10 performs power transmission between the power transmission device 11 and the power reception device 21, and includes a power transmitter 13 provided in the power transmission device 11 and a power receiver provided in the power reception device 21. 23.

  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 has a resonance circuit including a secondary coil 23a and a secondary capacitor 23b connected in parallel. The resonant frequencies of both resonant circuits are set to be the same.

  In addition, the power transmission device 11 includes power lines EL11 and EL12 that connect the AC power source 12 and the power transmitter 13 (primary coil 13a). The first power line EL11 of the power transmission device 11 connects one end of the AC power source 12 and one input end of the power transmitter 13 (one end of the primary coil 13a). The second power line EL12 of the power transmission device 11 connects the other end of the AC power source 12 and the other input end of the power transmitter 13 (the other end of the primary coil 13a). Thereby, the AC power output from the AC power supply 12 is input to the power transmitter 13.

  According to such a configuration, when AC power is input to the power transmitter 13 (primary coil 13a) in a situation where the relative position between the power transmitter 13 and the power receiver 23 is in a position where magnetic resonance can occur, The power receiver 23 (secondary coil 23a) performs magnetic field resonance. As a result, the power receiver 23 receives part of the energy from the power transmitter 13. That is, the power receiver 23 receives AC power from the power transmitter 13.

  Incidentally, the frequency of the AC power output from the AC power supply 12 is set corresponding to the resonance frequency of the power transmitter 13 and the power receiver 23 so that power transmission is possible between the power transmitter 13 and the power receiver 23. Yes. For example, the frequency of AC power is set to be the same as the resonance frequency of the power transmitter 13 and the power receiver 23. In addition, it is not restricted to this, The frequency of alternating current power and the resonant frequency of the power transmission device 13 and the power receiving device 23 may have shifted | deviated within the range which can be transmitted.

For convenience of explanation, in the following explanation, it is assumed that the power transmitter 13 and the power receiver 23 are arranged at a predetermined reference position and are not displaced.
The power receiving device 21 includes two power lines EL21 and EL22 that connect the power receiver 23 and the vehicle battery 22. The first power line EL <b> 21 of the power receiving device 21 connects one output end of the power receiver 23 (one end of the secondary coil 23 a) and one end of the vehicle battery 22. The second power line EL22 of the power receiving device 21 connects the other output end of the power receiver 23 (the other end of the secondary coil 23a) and the other end of the vehicle battery 22.

  The power receiving device 21 includes a rectifier (rectifier unit) 24 that rectifies the received power as an AC / DC conversion unit that converts AC power (hereinafter also simply referred to as received power) received by the power receiver 23 into DC power, and a rectifier 24. And a DC / DC converter 25 provided between the vehicle battery 22 and the vehicle battery 22. That is, in this embodiment, the rectifier 24 and the DC / DC converter 25 constitute an AC / DC conversion unit.

  The DC / DC converter 25 receives DC power rectified by the rectifier 24 and performs voltage value conversion of the DC power. The direct current power converted by the DC / DC converter 25 (direct current power output from the AC / DC conversion unit) is input to the vehicle battery 22, whereby the vehicle battery 22 is charged.

  The power transmission device 11 includes a power transmission side controller 14 that controls the AC power source 12 and the like. The power transmission side controller 14 controls on / off of the AC power supply 12 and controls the power value of the AC power output from the AC power supply 12.

  The power receiving device 21 includes a power receiving side controller 26 capable of wireless communication with the power transmitting side controller 14. The controllers 14 and 26 start or end power transmission through the exchange of information with each other. In the present embodiment, the power receiving side controller 26 corresponds to the control unit.

  As shown in FIG. 1, the non-contact power transmission device 10 includes a plurality of impedance converters 31 and 32 provided between the AC power supply 12 and the vehicle battery 22. Specifically, the non-contact power transmission apparatus 10 includes a primary side impedance converter 31 provided in the power transmission device 11 and a secondary side impedance converter 32 (secondary side impedance conversion unit) provided in the power receiving device 21. And. The primary side impedance converter 31 is provided between the AC power supply 12 and the power transmitter 13, and the secondary side impedance converter 32 is provided between the power receiver 23 and the rectifier 24.

  Each impedance converter 31 and 32 is comprised by LC circuit which has an inductor and a capacitor, for example. In detail, the primary side impedance converter 31 is provided with respect to the first inductors 31a and 31b provided on the two power lines EL11 and EL12 from the AC power source 12 to the power transmitter 13, and the first inductors 31a and 31b. And a first capacitor 31c provided in a subsequent stage and connected in parallel to the first inductors 31a and 31b.

  The secondary-side impedance converter 32 includes two inductors 32a and 32b provided on the two power lines EL21 and EL22 heading from the power receiver 23 to the vehicle battery 22, and upstream of the second inductors 32a and 32b. The LC circuit includes a second capacitor 32c provided and connected in parallel to the second inductors 32a and 32b.

  Incidentally, in this embodiment, the constants (impedances) of the impedance converters 31 and 32 are fixed values. The constant can be said to be a conversion ratio, inductance, or capacitance.

  Here, the present inventors have contributed to the transmission efficiency between the power transmitter 13 and the power receiver 23 by the real part of the impedance from the output end of the power receiver 23 (secondary coil 23a) to the vehicle battery 22. I found out. Specifically, it has been found that a specific resistance value Rout having relatively higher transmission efficiency than other resistance values exists in the real part of the impedance from the output terminal of the power receiver 23 to the vehicle battery 22. .

  Specifically, if a virtual load X is provided at the input end of the power transmitter 13, the resistance value of the virtual load X is Ra, and from the power receiver 23 (specifically, the output end of the power receiver 23) to the virtual load X. When the resistance value of Rb is Rb, the specific resistance value Rout is √ (Ra × Rb).

  Based on the above knowledge, the secondary impedance converter 32 has an impedance from the output end of the power receiver 23 to the vehicle battery 22 (impedance at the input end of the secondary impedance converter 32) approaches the specific resistance value Rout. The impedance from the input end of the rectifier 24 to the vehicle battery 22 is impedance-converted so as to (preferably match).

  Here, the power value of the AC power output from the AC power supply 12 depends on the impedance from the output terminal of the AC power supply 12 to the vehicle battery 22 (impedance at the input terminal of the primary side impedance converter 31).

  In such a configuration, the primary-side impedance converter 31 has an impedance from the output terminal of the power receiver 23 to the vehicle battery 22 at the specific resistance value Rout so that AC power having a desired power value is output from the AC power supply 12. Impedance conversion is performed on the impedance from the input end of the power transmitter 13 to the vehicle battery 22 in the approaching situation.

  For example, an impedance from the output terminal of the AC power supply 12 for outputting AC power of a desired power value from the AC power supply 12 to the vehicle battery 22 is set as an input impedance Zt suitable for charging. In this case, the primary-side impedance converter 31 is configured so that the impedance from the output terminal of the AC power supply 12 to the vehicle battery 22 approaches (preferably matches) the input impedance Zt suitable for the charging. Impedance conversion is performed on the impedance from the input terminal to the vehicle battery 22.

  In other words, the AC power supply 12 is configured to output AC power having a desired power value under the condition that the impedance from the output terminal of the AC power supply 12 to the vehicle battery 22 is the input impedance Zt suitable for the charging. It can be said that it is done.

Next, a detailed configuration of the DC / DC converter 25 will be described.
As shown in FIG. 2, the DC / DC converter 25 includes a first chopper circuit 41 having a first switching element Q1 and a second chopper circuit 42 having a second switching element Q2. Each of the switching elements Q1, Q2 is composed of, for example, an n-type power MOSFET. The first chopper circuit 41 corresponds to the first impedance converter, and the second chopper circuit 42 corresponds to the second impedance converter.

  The chopper circuits 41 and 42 are connected in parallel to each other. Specifically, the first power line EL21 includes a first branch line EL21a and a second branch line EL21b that are bifurcated. The first chopper circuit 41 includes a first coil L1 and a first diode D1 provided on the first branch line EL21a and connected in series to each other. The first diode D1 is connected in the forward direction. Specifically, the anode is connected to one end of the first coil L1, and the cathode is connected to one end of the vehicle battery 22 via the output end of the DC / DC converter 25. It is connected to the.

  The first switching element Q1 of the first chopper circuit 41 is connected in parallel to the first coil L1 and the first diode D1. The drain of the first switching element Q1 is connected to the connection portion of the first coil L1 and the first diode D1 in the first branch line EL21a, and the source of the first switching element Q1 is connected to the second power line EL22. .

  The second chopper circuit 42 includes a second coil L2 and a second diode D2 provided on the second branch line EL21b and connected in series to each other. The second diode D2 is connected in the forward direction. Specifically, the anode is connected to one end of the second coil L2, and the cathode is connected to one end of the vehicle battery 22 via the output end of the DC / DC converter 25. It is connected to the.

  The second switching element Q2 of the second chopper circuit 42 is connected in parallel to the second coil L2 and the second diode D2. The drain of the second switching element Q2 is connected to the connection portion of the second branch line EL21b between the second coil L2 and the second diode D2, and the source of the second switching element Q2 is connected to the second power line EL22. .

  In addition, the DC / DC converter 25 includes a first capacitor C1 provided in front of each chopper circuit 41, 42 and a second capacitor C2 provided in the subsequent stage of each chopper circuit 41, 42.

  According to this configuration, when at least one of the first switching element Q1 and the second switching element Q2 is periodically turned on / off (switching or chopping), the DC power rectified by the rectifier 24 is supplied to the vehicle battery 22. It is converted into DC power having the same voltage as the battery voltage. In this case, the conversion impedance Zq, which is the impedance from the input terminal of the DC / DC converter 25 to the vehicle battery 22, depends on the duty ratio of the switching element. Specifically, for example, when the on / off duty ratio of the switching element is small (that is, the on-time of the switching element per period is short), the conversion impedance Zq is high. That is, the DC / DC converter 25 performs impedance conversion so that the conversion impedance Zq becomes a predetermined value when at least one of the switching elements Q1 and Q2 is periodically turned on and off. The conversion impedance Zq can also be said to be the input impedance of the DC / DC converter 25.

  Incidentally, when the input power value of the DC / DC converter 25 is the same, both of the switching elements Q1, Q2 are periodically compared with the case where only the first switching element Q1 is periodically turned on / off. When turned on and off, the current value flowing through the first chopper circuit 41 decreases, and the current value flowing through the second chopper circuit 42 increases.

  Here, the vehicle battery 22 is a variable load whose impedance fluctuates according to the power value of the input DC power. For this reason, when the power value of the AC power output from the AC power supply 12 varies, the impedance of the vehicle battery 22 varies.

  On the other hand, the power receiving side controller 26 is configured to be capable of on / off control (control of gate voltage) of the switching elements Q1 and Q2. The power receiving side controller 26 then adjusts the impedance of the vehicle battery 22 so that the impedance from the input end of the DC / DC converter 25 to the vehicle battery 22 approaches (preferably matches) a constant value (specific impedance Zqt). The on / off duty ratio of at least one of the switching elements Q1, Q2 is adjusted according to the fluctuation. Note that the initial state of each of the switching elements Q1, Q2 (the state in which they are not periodically turned on / off) is the off state.

  In this configuration, the constant of the secondary side impedance converter 32 is set in correspondence with the specific impedance Zqt. Specifically, the constant of the secondary side impedance converter 32 is set so that the impedance from the output terminal of the power receiver 23 to the vehicle battery 22 becomes the specific resistance value Rout when the conversion impedance Zq is the specific impedance Zqt. Has been.

  As shown in FIG. 2, the power receiving device 21 includes a temperature sensor 43 that measures the temperature of the first chopper circuit 41. The temperature sensor 43 measures the temperature T of the first switching element Q1 as the temperature of the first chopper circuit 41 and transmits the measurement result to the power receiving side controller 26.

  The non-contact power transmission device 10 charges the vehicle battery 22 while exchanging information between the controllers 14 and 26 when the power transmitter 13 and the power receiver 23 are arranged at positions where power can be transmitted. Execute the charging process.

  In the charging process, the power transmission side controller 14 outputs AC power from the AC power source 12 until a predetermined termination condition is satisfied (for example, the charging state of the vehicle battery 22 is fully charged). The AC power supply 12 is controlled. As a result, AC power is transmitted from the power transmitter 13 to the power receiver 23, and the AC power is rectified by the rectifier 24 and input to the DC / DC converter 25.

  The power receiving side controller 26 periodically turns on and off the first switching element Q1 regardless of the temperature T of the first switching element Q1 in a situation where direct current power is input to the DC / DC converter 25, thereby converting the conversion impedance Zq. To be a specific impedance Zqt.

  In such a situation (a situation where DC power is input to the DC / DC converter 25 and the first switching element Q1 is periodically turned on / off), the power receiving side controller 26 responds to the temperature T of the first switching element Q1. Thus, a temperature response process for controlling the switching operation of the second switching element Q2 is executed. The temperature handling process is executed at a predetermined cycle in the above situation. The switching operation means that the switching element is periodically turned on / off.

  Incidentally, the situation where the DC power is input to the DC / DC converter 25 can be said to be the situation where the AC power is output from the AC power supply 12, and the AC power is received by the power receiver 23 (secondary coil 23a). It can be said that the situation is being done.

The temperature handling process will be described in detail with reference to FIG.
As shown in FIG. 3, first, in step S <b> 101, the power receiving side controller 26 grasps the temperature T of the first switching element Q <b> 1 based on the measurement result of the temperature sensor 43.

  Thereafter, in step S102, the power receiving controller 26 determines whether or not the second switching element Q2 is performing a switching operation. Specifically, the power receiving side controller 26 determines whether or not the second switching element Q2 has already been periodically turned on / off.

  If the second switching element Q2 is not in a switching operation, it means that the second chopper circuit 42 is not operating. In this case, the power receiving side controller 26 proceeds to step S103, and determines whether or not the temperature T of the first switching element Q1 grasped in step S101 is equal to or higher than a predetermined first threshold temperature Tth1.

  The first threshold temperature Tth1 may be set to, for example, an upper limit value of the temperature at which the first chopper circuit 41 normally operates or a value lower than the upper limit value by a predetermined margin. Specifically, the first threshold temperature Tth1 may be set to correspond to, for example, the operation guaranteed temperature range of the first switching element Q1, and is, for example, the same as the upper limit value of the operation guaranteed temperature range of the first switching element Q1 or It may be set to a value lower by a predetermined margin than that.

  When the temperature T of the first switching element Q1 is lower than the first threshold temperature Tth1, this process is terminated as it is. On the other hand, when the temperature T of the first switching element Q1 is equal to or higher than the first threshold temperature Tth1, it means that the temperature T of the first switching element Q1 is excessively high. In this case, in step S104, the power receiving side controller 26 starts the switching operation of the second switching element Q2. Specifically, the power receiving controller 26 controls the second switching element Q2 such that the second switching element Q2 is periodically turned on / off.

  Incidentally, the power receiving side controller 26 controls the switching elements Q1 and Q2 so that the switching modes (phase, on / off duty ratio and frequency) of the switching elements Q1 and Q2 are the same.

  Further, the duty ratio of ON / OFF of the first switching element Q1 when only the first switching element Q1 is performing switching operation, and ON / OFF of each switching element Q1, Q2 when each switching element Q1, Q2 is performing switching operation The duty ratio is set to be the same.

  When the second switching element Q2 is in a switching operation, it means that the second chopper circuit 42 has already been operated. In this case, the power receiving controller 26 makes a negative determination in step S102 and proceeds to step S105. In step S105, the power receiving side controller 26 determines whether or not the temperature T of the first switching element Q1 is equal to or lower than a second threshold temperature Tth2 that is lower than the first threshold temperature Tth1.

  When the temperature T of the first switching element Q1 is higher than the second threshold temperature Tth2, the power receiving side controller 26 ends this process as it is. In this case, the switching operation of the second switching element Q2 is continued. On the other hand, when the temperature T of the first switching element Q1 is equal to or lower than the second threshold temperature Tth2, the power receiving side controller 26 proceeds to step S106, stops the switching operation of the second switching element Q2, and ends this process. Specifically, the power receiving controller 26 performs control so that the second switching element Q2 is turned off.

  Next, the effect | action of this embodiment is demonstrated using FIG. FIG. 4 is a graph showing a time change of the temperature T of the first switching element Q1. In addition, an operating chopper circuit of the chopper circuits 41 and 42 is also shown.

  As shown in FIG. 4, when AC power is output from the AC power supply 12 at the timing t0, the first chopper circuit 41 operates. Specifically, the switching operation of the first switching element Q1 is performed. As a result, the temperature T of the first switching element Q1 rises.

  Thereafter, at the timing t1, the temperature T of the first switching element Q1 reaches the first threshold temperature Tth1. Then, the switching operation of the second switching element Q2 is started. As a result, both the first chopper circuit 41 and the second chopper circuit 42 operate. In this case, compared with the case where only the first chopper circuit 41 is operating, the value of the current flowing through the first switching element Q1 is reduced. Therefore, the amount of heat generated by the first switching element Q1 is reduced, and the temperature T of the first switching element Q1 is lowered.

  Thereafter, when the temperature T of the first switching element Q1 reaches the second threshold temperature Tth2 at the timing of t2, the operation of the second chopper circuit 42 is stopped. As a result, only the first chopper circuit 41 operates. Thereafter, when the temperature T of the first switching element Q1 reaches the first threshold temperature Tth1 again at the timing of t3, the second chopper circuit 42 operates.

  As described above, the temperature T of the first switching element Q1 is equal to or lower than the first threshold temperature Tth1 by operating or stopping the second chopper circuit 42 corresponding to the temperature T of the first switching element Q1. It is within the range.

  In other words, in the present embodiment, the DC / DC converter 25 uses the chopper circuits 41 and 42 to perform impedance conversion compared to the case where only the first chopper circuit 41 performs impedance conversion. The current value flowing through the first chopper circuit 41 is configured to be small. The DC / DC converter 25 performs impedance conversion using the first chopper circuit 41, and when the temperature T of the first switching element Q1 becomes the first threshold temperature Tth1, The second chopper circuit 42 is used to perform impedance conversion.

According to the embodiment described in detail above, the following excellent effects are obtained.
(1) The power receiving device 21 receives the AC power received by the power receiver 23 and the power receiver 23 (secondary coil 23a) capable of receiving AC power from the power transmitter 13 (primary coil 13a) in a contactless manner. A rectifier 24 and a DC / DC converter 25 are provided as an AC / DC conversion unit for converting to DC power. The DC / DC converter 25 includes a first switching element Q1, a first chopper circuit 41 that performs impedance conversion by periodically turning on and off the first switching element Q1, and a second switching element Q2. And a second chopper circuit 42 that performs impedance conversion when the two switching elements Q2 are periodically turned on and off. The chopper circuits 41 and 42 are connected in parallel. In such a configuration, the power receiving device 21 includes a temperature sensor 43 that measures the temperature T of the first switching element Q1, and when the first switching element Q1 is periodically turned on and off, the temperature T of the first switching element Q1 is When the temperature becomes equal to or higher than the first threshold temperature Tth1, the second switching element Q2 is configured to periodically turn on and off. As a result, the value of the current flowing through the first switching element Q1 is reduced by the operation of the second chopper circuit 42. Accordingly, since the amount of heat generated in the first switching element Q1 is reduced, excessive heat generation of the first switching element Q1 can be suppressed, and excessive heat generation of the first chopper circuit 41 can be suppressed.

  (2) Here, when the power value of the AC power output from the AC power source 12, that is, the power value of the AC power received by the power receiver 23 increases, the temperature T of the first switching element Q1 increases and the first The value of the current flowing through the coil L1 increases. When the value of the current flowing through the first coil L1 increases, the loss generated in the first coil L1 tends to increase. In particular, for example, in the configuration in which the first coil L1 is wound around the core, if the value of current flowing through the first coil L1 increases and magnetic saturation occurs in the core, the inductance of the first coil L1 decreases. As a result, the value of the current flowing through the first coil L1 may become excessively large, and the loss may be excessively increased. However, it is not preferable to use an element with a large rating as the first coil L1 from the viewpoints of upsizing and cost.

  In contrast, in the present embodiment, the temperature T of the first switching element Q1 becomes equal to or higher than the first threshold temperature Tth1 due to, for example, output of AC power having a relatively large power value from the AC power supply 12. In this case, the second chopper circuit 42 operates. Thereby, compared with the case where only the 1st chopper circuit 41 was operating, the current value which flows into the 1st coil L1 also becomes small. Therefore, even when AC power having a relatively large power value is output from the AC power supply 12, excessive heat generation of the first switching element Q1 can be suppressed, and excessively large loss occurs in the first coil L1. Can be suppressed.

  (3) The first chopper circuit 41 continues to operate even when the temperature T of the first switching element Q1 becomes equal to or higher than the first threshold temperature Tth1. Specifically, the periodic on / off of the first switching element Q1 is continued even when the temperature T of the first switching element Q1 is equal to or higher than the first threshold temperature Tth1. In other words, the first switching element Q1 is periodically turned on and off regardless of the temperature T of the first switching element Q1 in a situation where DC power is input to the DC / DC converter 25. As a result, current can be distributed, and only one of the chopper circuits 41 and 42 can be prevented from generating heat excessively.

  (4) The first chopper circuit 41 includes a first switching element Q1 and a first diode D1 which are n-type power MOSFETs as semiconductor elements, and the temperature sensor 43 determines the temperature T of the first switching element Q1. taking measurement. Thereby, for example, the second chopper circuit 42 can be operated so that the temperature T of the first switching element Q1 does not exceed the upper limit value of the guaranteed operating temperature range.

  (5) In a situation where each switching element Q1, Q2 is performing switching operation, when the temperature T of the first switching element Q1 becomes the second threshold temperature Tth2 lower than the first threshold temperature Tth1, The switching operation of the switching element Q2 is stopped. Thereby, when the temperature T of the first switching element Q1 is relatively low, the switching operation of the second switching element Q2 is stopped, thereby avoiding the occurrence of the switching loss of the second switching element Q2. Therefore, in a situation where the temperature T of the first switching element Q1 is relatively high, the rise of the temperature T of the first switching element Q1 is suppressed by operating both the chopper circuits 41 and 42, while the first switching element Q1 is operated. In a situation where the temperature T of the element Q1 is relatively low, the loss can be reduced by stopping the operation of the second chopper circuit.

  (6) The vehicle battery 22 is a fluctuating load whose impedance varies according to the power value of the input DC power. In addition, the power receiving device 21 is provided between the power receiver 23 and the rectifier 24, and makes the impedance from the output end of the power receiver 23 to the vehicle battery 22 close to a desired value (for example, a specific resistance value Rout). An impedance converter 32 is provided.

  In such a configuration, at least one of the first switching element Q1 and the second switching element Q2 is periodically turned on and off so that the conversion impedance Zq becomes a predetermined specific impedance Zqt. The constant of the secondary impedance converter 32 is set in correspondence with the specific impedance Zqt. Thereby, even if the input power value of the vehicle battery 22 fluctuates due to the fluctuation of the power value of the AC power output from the AC power supply 12, the impedance of the vehicle battery 22 fluctuates. The fluctuation of the conversion impedance Zq can be suppressed. Therefore, it is possible to suppress the impedance from the output terminal of the power receiver 23 to the vehicle battery 22 from deviating from the specific resistance value Rout due to the variation of the conversion impedance Zq.

In addition, you may change the said embodiment as follows.
The measurement target of the temperature sensor 43 is not limited to the first switching element Q1, and is arbitrary. For example, the measurement target may be a first diode D1 as a semiconductor element. In this case, the first threshold temperature Tth1 may be set to a value equal to or lower than the upper limit value (rated temperature) of the operation guaranteed temperature range of the first diode D1 by a predetermined margin.

  The measurement object may be both the first switching element Q1 and the first diode D1. In this case, even when either the temperature T of the first switching element Q1 or the temperature of the first diode D1 becomes equal to or higher than the first threshold temperature Tth1, the second chopper circuit 42 is operated. Good.

  Further, the threshold temperature for the switching element may be set in correspondence with the first switching element Q1, and the threshold temperature for the diode may be set in correspondence with the first diode D1. In this case, either (A) the temperature T of the first switching element Q1 is equal to or higher than the threshold temperature for the switching element, or (B) the temperature of the first diode D1 is equal to or higher than the threshold temperature for the diode. The second chopper circuit 42 may be operated when the above condition is satisfied.

  (Circle) you may employ | adopt the 1st coil L1 as a temperature measurement object. In a configuration in which a heat sink (heat radiator) is attached to the first switching element Q1, the first diode D1, or the like, the temperature of the heat sink may be measured.

  In addition, when the first chopper circuit 41 and the second chopper circuit 42 are individually packaged (unitized), the temperature of the package of the first chopper circuit 41 may be measured, or the package It is good also considering the atmospheric temperature inside as a measuring object. Furthermore, when the DC / DC converter 25 is packaged, the temperature of the package or the ambient temperature in the package of the DC / DC converter 25 may be measured. In short, the measurement unit only needs to be able to measure a location that is affected by the heat generation of the first impedance conversion unit (first chopper circuit 41).

  A configuration in which the switching operation (periodic on / off) of the first switching element Q1 stops when the temperature T of the first switching element Q1 becomes equal to or higher than the first threshold temperature Tth1 may be employed. Specifically, the first switching element Q1 may be configured to be in either the on state or the off state when the temperature T of the first switching element Q1 is equal to or higher than the first threshold temperature Tth1. Even in this case, since the second chopper circuit 42 is operating, the conversion impedance Zq can be set to the specific impedance Zqt. In consideration of the loss of the current flowing through the first switching element Q1, it is preferable that the first switching element Q1 is turned off.

  The specific configuration of each chopper circuit 41, 42 is not limited to that of the embodiment, and is arbitrary, and may be either a step-down type or a step-up type. Each chopper circuit 41, 42 may have a plurality of switching elements.

The DC / DC converter 25 has a configuration including two chopper circuits 41 and 42, but the number of chopper circuits is arbitrary. For example, three or more chopper circuits may be provided.
Each chopper circuit 41, 42 has the same configuration, but may be different.

  In embodiment, although the DC / DC converter 25 and the rectifier 24 comprised the AC / DC conversion part, it is not restricted to this. The AC / DC conversion unit converts AC power received by the power receiver 23 into DC power, and includes a first impedance conversion unit having a first switching element Q1 and a second impedance having a second switching element Q2. If it has an impedance converter, its specific configuration is arbitrary. For example, the AC / DC converter includes a switching element, and an AC chopper circuit that converts AC power received by the power receiver 23 into AC power having a desired voltage value when the switching element is periodically turned on and off. You may be comprised by the AC / AC converter which has two or more, and the rectifier 24 which rectifies | straightens the alternating current power output from the said AC / AC converter.

  The control unit that performs on / off control of the switching elements Q1, Q2 is not limited to the power receiving controller 26, and is arbitrary. For example, the power transmission side controller 14 may determine the on / off mode of the switching elements Q1 and Q2 and issue an instruction to the power reception side controller 26. In addition, a dedicated controller other than the controllers 14 and 26 may perform on / off control of the switching elements Q1 and Q2.

  The temperature T of the first switching element Q1 may slightly exceed the first threshold temperature Tth1. In short, the non-contact power transmission device 10 (or the power receiving device 21) starts the switching operation of the second switching element Q2 when the temperature T of the first switching element Q1 becomes equal to or higher than the first threshold temperature Tth1. Therefore, it is only necessary that the temperature T of the first switching element Q1 be prevented from further increasing.

  The specific circuit configuration of each impedance converter 31 and 32 is arbitrary. For example, the primary side impedance converter 31 may be an inverted L type LC circuit or the like in which the first inductor 31b is omitted, and the secondary side impedance converter 32 is an L type in which the second inductor 32b is omitted. The LC circuit or the like may be used. Moreover, each impedance converter 31 and 32 may be π type, T type, or the like.

  The constants of the impedance converters 31 and 32 may be variable values. In this case, for example, when the relative position between the power transmitter 13 and the power receiver 23 varies, the controllers 14 and 26 change the constants of the impedance converters 31 and 32 in accordance with the variation in the relative position. It is good to control. Thereby, it is possible to cope with the positional deviation between the power transmitter 13 and the power receiver 23.

  Here, when fluctuations in the relative position between the power transmitter 13 and the power receiver 23 and fluctuations in the impedance of the vehicle battery 22 occur, the constants of the impedance converters 31 and 32 can be changed to correspond to the two fluctuations. When trying to control, the variable control becomes difficult or complicated. On the other hand, even if the impedance of the vehicle battery 22 fluctuates, the impedance of the vehicle battery 22 can be controlled in the variable control of the constants of the impedance converters 31 and 32 by making the conversion impedance Zq constant. There is no need to consider fluctuations. Thereby, variable control of the constant of each impedance converter 31 and 32 can be performed suitably.

The number of primary side impedance converters provided in the power transmission device 11 and the number of secondary side impedance converters provided in the power receiving device 21 are arbitrary, and may be two or more, for example.
O At least one of the impedance converters 31 and 32 may be omitted.

The AC power supply 12 is a voltage source, but may be a power source or a current source.
In the configuration in which the AC power supply 12 is a power source, the impedance converters 31 and 32 may perform impedance matching. The secondary impedance converter 32 performs impedance conversion so that the impedance from the output terminal of the power receiver 23 to the vehicle battery 22 matches the impedance from the output terminal of the power receiver 23 to the AC power supply 12. May be. In addition, the primary side impedance converter 31 extends from the input end of the power transmitter 13 to the vehicle battery 22 so that the impedance from the output end of the AC power source 12 to the vehicle battery 22 matches the output impedance of the AC power source 12. Impedance conversion may be performed on the impedance.

  The primary impedance converter 31 converts the impedance from the input terminal of the power transmitter 13 to the vehicle battery 22 so that the power factor is improved (reactance approaches 0). Also good.

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 they may be different within a range where power transmission is possible.
The power transmitter 13 and the power receiver 23 have the same configuration, but are not limited to this, and may have different configurations.

Each capacitor 13b, 23b may be omitted. In this case, magnetic field resonance is performed using the parasitic capacitances of the coils 13a and 23a.
○ The power receiving device 21 may be mounted on any object, and may be mounted on, for example, a robot or an electric wheelchair.

  In embodiment, although the primary side coil 13a and the primary side capacitor | condenser 13b were connected in parallel, it is not restricted to this, Both may be connected in series. Similarly, the secondary coil 23a and the secondary capacitor 23b may be connected in series.

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 the embodiment, the AC power received by the power receiver 23 is used for charging the vehicle battery 22, but is not limited thereto, and may be used for other purposes, for example.

  The power transmitter 13 may include a resonance circuit including a primary side coil 13a and a primary side capacitor 13b, and a primary side coupling coil that is coupled to the resonance circuit by electromagnetic induction. Similarly, the power receiver 23 may include a resonance circuit including a secondary coil 23a and a secondary capacitor 23b, and a secondary coupling coil coupled to the resonance circuit by electromagnetic induction.

Next, a preferable example that can be grasped from the embodiment and another example will be described below.
(A) At least one of the first switching element and the second switching element is periodically turned on and off so that the input impedance of the DC / DC converter becomes a predetermined specific impedance, and the power receiving The device includes a secondary impedance converter that is provided between the secondary coil and the rectification unit and performs impedance conversion, and the constant of the secondary impedance converter corresponds to the specific impedance. The power receiving device according to claim 5, which is set.

  (B) The AC / DC converter is compared with a case where only the first switching element is periodically turned on / off under the condition that the power value input to the AC / DC converter is the same. The current value flowing through the first impedance converter is smaller when both the first switching element and the second switching element are periodically turned on and off. The power receiving device according to any one of 5 and (a).

  DESCRIPTION OF SYMBOLS 10 ... Non-contact electric power transmission apparatus, 11 ... Power transmission apparatus, 12 ... AC power supply, 13a ... Primary side coil, 21 ... Power receiving apparatus, 22 ... Vehicle battery, 23a ... Secondary side coil, 24 ... Rectifier, 25 ... DC / DC converter, 41 ... first chopper circuit (first impedance converter), 42 ... second chopper circuit (second impedance converter), 43 ... temperature sensor (measurement unit), Q1 ... first switching element, Q2 ... Second switching element, Tth1... First threshold temperature, Tth2... Second threshold temperature.

Claims (6)

In a power receiving device capable of receiving the AC power in a contactless manner from a power transmitting device having a primary side coil to which AC power is input,
A secondary coil capable of receiving the AC power input to the primary coil in a contactless manner;
An AC / DC converter that converts AC power received by the secondary coil into DC power;
With
The AC / DC converter is
A first impedance converter having a first switching element, and performing impedance conversion by periodically turning on and off the first switching element;
A second impedance converter having a second switching element, and performing impedance conversion by periodically turning on and off the second switching element;
A measurement unit for measuring the temperature of the first impedance conversion unit;
With
The first impedance converter and the second impedance converter are connected in parallel,
When the temperature of the first impedance conversion unit measured by the measurement unit is equal to or higher than a predetermined threshold temperature when the first switching device is periodically turned on and off, the cycle of the second switching device Power receiving device characterized by being turned on and off.   2. The power receiving according to claim 1, wherein the periodic on / off of the first switching element is continued even when the temperature of the first impedance conversion unit measured by the measurement unit is equal to or higher than the threshold temperature. machine. The first impedance converter has a semiconductor element,
The power receiving device according to claim 1, wherein the measurement unit measures a temperature of the semiconductor element as a temperature of the first impedance conversion unit. When the threshold temperature is a first threshold temperature,
The second threshold value in which the temperature of the first impedance conversion unit measured by the measurement unit is lower than the first threshold temperature in a situation where both the first switching element and the second switching element are periodically turned on and off. The power receiving device according to any one of claims 1 to 3, wherein when the temperature is reached, periodic on / off of the second switching element is stopped. The AC / DC converter is
A rectifying unit that rectifies AC power received by the secondary coil;
DC power rectified by the rectification unit is input, a DC / DC converter having the first impedance conversion unit and the second impedance conversion unit,
With
The first impedance converter is a first chopper circuit having the first switching element,
The power receiving device according to any one of claims 1 to 4, wherein the second impedance converter is a second chopper circuit having the second switching element. A primary coil to which AC power is input;
A secondary coil capable of receiving the AC power input to the primary coil in a contactless manner;
An AC / DC converter that converts AC power received by the secondary coil into DC power;
In a non-contact power transmission device comprising:
The AC / DC converter is
A first impedance converter having a first switching element, and performing impedance conversion by periodically turning on and off the first switching element;
A second impedance converter having a second switching element, and performing impedance conversion by periodically turning on and off the second switching element;
A measurement unit for measuring the temperature of the first impedance conversion unit;
With
The first impedance converter and the second impedance converter are connected in parallel,
The non-contact power transmission device includes a control unit that performs on / off control of the first switching element and the second switching element,
When the temperature of the first impedance conversion unit measured by the measurement unit is equal to or higher than a predetermined threshold temperature in a situation where the first switching element is periodically turned on and off, 2. A non-contact power transmission device, wherein two switching elements are periodically turned on and off.