JP2016116365A - Power reception device for non-contact power supply system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power reception device capable of suppressing an increase in the currents or voltage of a power reception device while suppressing a sharp change in the impedance of the power reception device viewed from a power transmission device side without operating a switching element at a high speed when the currents or voltage of the power reception device reaches a predetermined threshold.SOLUTION: A power reception device 13 of a non-contact power supply system 10 having a power reception coil 38 for receiving AC power to be transmitted in a non-contact state from a power transmission coil 37 by the power reception coil 38 includes: a rectifier circuit 20 having a plurality of switches SW1 to SW4; a voltage sensor 49 for detecting the output voltage of the power reception device 13; and a control part (70) for executing a rectifying operation to rectify the AC power by controlling each of the switches SW1 to SW4. The control part fixes a switching cycle under a condition that a detection value by the voltage sensor 49 exceeds a predetermined threshold, and adjusts the phases of the switches SW1 to SW4 to change the operation of the rectifier circuit from the rectifying operation to a short-circuit operation.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power receiving device of a non-contact power feeding system that performs non-contact power transmission from a power transmitting coil to a power receiving coil.

  A non-contact power feeding system that uses a power transmitting coil and a power receiving coil as a pair and transmits power from the power transmitting coil to the power receiving coil in a non-contact manner has attracted attention. The power receiving device in the non-contact power feeding system disclosed in Patent Literature 1 receives AC power transmitted from the power transmitting coil of the power transmitting device in a contactless manner by the power receiving coil. Then, the received AC power is rectified by a rectifier circuit having a plurality of switching elements connected in a full bridge type and a rectifying element connected in parallel for each switching element, and the DC power is supplied to the electric load. Is output.

  When the output voltage of the power receiving device that is output to this electrical load rises abnormally, the operation of the rectifier circuit is short-circuited to short-circuit both ends of the power receiving coil from the rectifying operation that rectifies the AC power input from the power receiving coil. By changing to operation, it is possible to suppress the output voltage of the power receiving apparatus from continuing to rise abnormally.

  Here, when the rectification operation is changed to the short-circuit operation, the output voltage of the power receiving device becomes zero after abnormal increase. For this reason, the impedance of the power receiving device as viewed from the power transmitting device side changes abruptly, a high voltage is applied to the element included in the power transmitting device, and the element included in the power transmitting device may be damaged. Therefore, in the technique described in Patent Document 1, a rapid change in the impedance of the power receiving device viewed from the power transmitting device side is suppressed by performing a voltage clamp mode in which the rectifying operation and the short circuit operation are alternately switched.

JP 2014-79107 A

  The switching frequency in the voltage clamp mode in the configuration described in Patent Document 1 is n times the switching frequency in the rectification operation (n is an integer of 2 or more). For this reason, it is necessary to use a switching element capable of high-speed operation, and there is a problem that the cost increases, and there is a problem that heat generation in the switching element increases as the switching frequency increases.

  In view of the above problems, the present invention suppresses a rapid change in the impedance of the power receiving device viewed from the power transmitting device side without causing the switching element to operate at high speed when the current or voltage of the power receiving device reaches a predetermined threshold. However, a main object is to provide a power receiving device that can suppress an increase in current or voltage of the power receiving device.

  The present invention includes a power receiving device of a non-contact power feeding system (10) having a power receiving coil (38) and receiving AC power transmitted from the power transmitting coil (37) of the power transmitting device (12) in a contactless manner. (13) A rectifier circuit having a plurality of switching elements (SW1 to SW4) connected to the power receiving coil and connected in a full bridge type, and a current in any path of the power receiving device or A detection means (49) for detecting a voltage, and a control unit (70) for controlling a switching state of the switching element and performing a rectifying operation for rectifying AC power input from the power receiving coil, The control unit fixes the switching cycle of the switching element on the condition that the detection value by the detection unit exceeds a predetermined threshold. By adjusting the phase of the switching control of the switching element, and changing the operation of the rectifier circuit to short-circuit operation for short-circuiting the both ends of the power receiving coil from the rectification operation.

  The operation of the rectifier circuit is changed from the rectification operation to the short-circuit operation by adjusting the phase (phase shift) after fixing the switching cycle. With this configuration, it is possible to suppress an increase in the current or voltage of the power receiving device without causing the switching element to operate at high speed and suppressing an abrupt change in the impedance of the power receiving device viewed from the power transmitting device side.

The electric circuit diagram showing a non-contact electric power feeding system. The timing chart showing the current voltage change at the time of a main relay interruption | blocking. The figure showing rectification operation and short circuit operation. The timing chart showing the drive signal at the time of a rectification operation | movement, the time of transition, and a short circuit operation. The figure showing the relationship between the amount of phase shifts, and the electric current which flows into a receiving coil. The figure showing the relationship between the amount of phase shifts, and the output voltage of a receiving device. The figure showing the phase shift in 1st Embodiment. The timing chart showing the current voltage change at the time of implementing the phase shift control of 1st Embodiment. The figure showing the phase shift in 2nd Embodiment. The figure showing the phase shift in 3rd Embodiment. The figure showing the phase shift in 4th Embodiment.

(First embodiment)
The contactless power supply system in the present embodiment includes a power transmission device that is supplied with power from a commercial power source and transmits power to the power receiving device in a contactless manner, and a power receiving device that receives power from the power transmission device in a contactless manner. The power receiving device is mounted on a vehicle such as an electric vehicle or a hybrid vehicle, and charges the in-vehicle battery by outputting electric power to the in-vehicle battery. Moreover, the power transmission device is provided in a parking space where the vehicle is parked.

  FIG. 1 shows a non-contact power feeding system 10 in the present embodiment. The non-contact power supply system 10 transmits the power supplied from the DC power supply 11 from the power transmission device 12 to the power reception device 13 mounted on the vehicle in a contactless manner. And the power receiving apparatus 13 outputs the transmitted electric power with respect to the vehicle-mounted battery 14, and performs charging. The DC power supply 11 is, for example, an AC / DC converter that converts AC power input from a commercial power supply into DC power and outputs the DC power.

  The power transmission device 12 includes a step-down circuit 15 that steps down power supplied from the DC power supply 11, an inverter circuit 16 that converts DC power output from the step-down circuit 15 into AC power having a predetermined frequency, and a device that receives AC power. 13 is provided with a power transmission resonance circuit 17 that outputs the power to 13. In addition, a power transmission filter circuit 18 that removes AC power other than a predetermined frequency range from the AC power input from the inverter circuit 16 and outputs the power to the power transmission resonance circuit 17 is provided.

  The power reception device 13 includes a power reception resonance circuit 19 to which power is supplied from the power transmission resonance circuit 17, a rectification circuit 20 that performs full-wave rectification on AC power supplied from the power reception resonance circuit 19, and power that is supplied from the rectification circuit 20. A booster circuit 21 that boosts the voltage to a predetermined voltage is provided. In addition, a power receiving filter circuit 22 that removes AC power other than a predetermined frequency range from the AC power input from the power receiving resonance circuit 19 and outputs the AC power to the rectifier circuit 20 is provided.

  The step-down circuit 15 is a well-known step-down chopper circuit and is connected to the DC power supply 11. The step-down circuit 15 includes a capacitor 23 for smoothing power supplied from the DC power supply 11, a reactor 24 for storing power, a capacitor 25 for smoothing output voltage, a switch 26 for adjusting the output voltage, and the switch 26 being off. A diode 27 is provided for passing a current to the reactor 24 when it is in a state. Note that the switch 26 is a MOS-FET and includes a diode component connected in antiparallel between a drain and a source.

  The inverter circuit 16 is a known full-bridge type inverter circuit, and is provided on the output side of the step-down circuit 15. The inverter circuit 16 includes switches 28 to 31, and the DC power supplied from the step-down circuit 15 is converted into AC power having a predetermined frequency when the switches 28 to 31 are alternately turned on and off (open / close controlled). . The switches 28 to 31 are MOS-FETs, each having a body diode. Further, the switches 28 to 31 may be IGBTs.

  The power transmission resonance circuit 17 is configured by connecting a power transmission capacitor 36 and a power transmission coil 37 in parallel. The power receiving resonance circuit 19 is configured by connecting a power receiving coil 38 and a power receiving capacitor 39 in parallel.

  The power transmission coil 37 and the power reception coil 38 are each sealed with a plate-shaped resin, and a power transmission pad is formed of a resin that seals the power transmission coil 37 and the power transmission coil 37, and the power reception coil 38 and the power reception coil 38 are sealed. The power receiving pad is made of resin. The power transmission pad is provided at a predetermined position on the ground surface of the parking space, and the power reception pad is provided at the bottom of the vehicle. When the vehicle is parked in the parking space, the power transmission pad and the power receiving pad are arranged facing each other in the vertical direction at a predetermined interval. Then, AC power is supplied to the power transmission coil 37 in the facing state, and the alternating magnetic flux generated by the AC power is linked to the power reception coil 38, thereby causing the power reception coil 38 to generate AC power by electromagnetic induction.

  The size of the inductive component of the power transmission coil 37 and the power reception coil 38 and the size of the capacitance component of the power transmission capacitor 36 and the power reception capacitor 39 are determined when the power transmission pad and the power reception pad are in a predetermined facing state. The power factor of 16 is set to 1 or a value close to 1.

  The rectifier circuit 20 is a well-known full-bridge type synchronous rectifier circuit, and converts AC power supplied from the power receiving resonance circuit 19 into DC. The rectifier circuit 20 includes switches SW1 to SW4, and the switches SW1 to SW4 are alternately turned on and off to convert the DC power supplied from the step-down circuit 15 into AC power having a predetermined frequency. The switches SW1 to SW4 are MOS-FETs and include body diodes.

  A smoothing capacitor 48 is provided on the output side of the rectifier circuit 20. Further, main relays 50 and 51 are respectively provided between both terminals of the smoothing capacitor 48 and the in-vehicle battery 14. The main relays 50 and 51 are turned off, so that the connection between the power receiving device 13 and the in-vehicle battery 14 is cut off. When charging the in-vehicle battery 14, the main relays 50 and 51 are in principle turned on.

  The power transmission filter circuit 18 is a bandpass filter including reactors 32 and 33 and capacitors 34 and 35, and is provided between the inverter circuit 16 and the power transmission resonance circuit 17. In the power transmission filter circuit 18, the reactor 32 and the capacitor 34, and the reactor 33 and the capacitor 35 are connected in series. A capacitor 34 is connected to one of the output terminals of the inverter circuit 16 and a capacitor 35 is connected to the other. That is, the power transmission filter circuit 18 is configured by connecting in parallel a bandpass filter composed of the reactor 32 and the capacitor 34 and a bandpass filter composed of the reactor 33 and the capacitor 35.

  The power reception filter circuit 22 is a bandpass filter including reactors 40 and 41 and capacitors 42 and 43, and is provided between the power reception resonance circuit 19 and the rectification circuit 20. In the power receiving filter circuit 22, the reactor 40 and the capacitor 42, the reactor 41 and the capacitor 43 are connected in series. And the reactor 40 is connected to one of the output terminals of the power receiving resonance circuit 19, and the reactor 41 is connected to the other. In other words, the power receiving filter circuit 22 is configured by connecting in parallel the bandpass filter composed of the reactor 40 and the capacitor 42 and the bandpass filter composed of the reactor 41 and the capacitor 43.

  The size of the inductive component of reactors 32, 33, 40, and 41 so that the resonance frequency (pass band) of each of the band-pass filters connected in parallel is the frequency of the AC power output from inverter circuit 16. And the magnitude | size of the capacitance component of capacitor | condenser 34,35,42,43 is determined. Further, in the power transmission filter circuit 18 and the power reception filter circuit 22, heat generation in the bandpass filter can be dispersed by connecting two bandpass filters in parallel.

  The power transmission device 12 includes a power transmission control unit 60 that controls the power transmission device 12, and the power reception device 13 includes a power reception control unit 70 that controls the power reception device 13. The power transmission control unit 60 controls the step-down circuit 15 and the inverter circuit 16. The power reception control unit 70 controls the rectifier circuit 20.

  Further, the vehicle is provided with an ECU 80 (Electronic Control Unit) and a charge start button (not shown). When the charging start button is pressed by the user while the vehicle is stopped, ECU 80 starts power transmission from power transmission device 12 to power reception device 13. Specifically, the ECU 80 gives commands to the control units 60 and 70 and controls on / off of the main relays 50 and 51. The control units 60 and 70 and the ECU 80 are microcomputers including a CPU that is an arithmetic unit, a RAM that is a main storage device, and the like. Further, communication between the power transmission control unit 60 and the ECU 80 is performed wirelessly, and communication between the power reception control unit 70 and the ECU 80 is performed by wire.

  Here, when an abnormality occurs in the in-vehicle battery 14 during power transmission from the power transmitting device 12 to the power receiving device 13, the ECU 80 stops charging the in-vehicle battery 14. Specifically, the ECU 80 commands the power transmission control unit 60 and the power reception control unit 70 to stop the power output by turning off the main relays 50 and 51. In this case, with the delay of the command signal from the ECU 80 to the power transmission control unit 60, power transmission from the power transmission device 12 to the power reception device 13 may be continued after the main relays 50 and 51 are turned off.

  In FIG. 2, the output voltage Vo of the power receiving device 13 when the power transmission from the power transmitting device 12 to the power receiving device 13 is continued after the main relays 50 and 51 are cut off, the output current Io of the power receiving device 13, and the power transmission current flowing through the power transmission coil 37. 11 shows the time change of the received current I2 flowing through I1 and the receiving coil 38.

  At time T1, the main relays 50 and 51 are turned off due to the abnormality of the in-vehicle battery 14. When the main relays 50 and 51 are turned off, the output current Io that is a current flowing from the power receiving device 13 into the in-vehicle battery 14 becomes zero. Thereafter, the current flows into the smoothing capacitor 48, whereby the voltage across the smoothing capacitor 48 that is the output voltage Vo of the power receiving device 13 continues to rise. For this reason, an overvoltage is applied to the rectifier circuit 20 and the smoothing capacitor 48, and the elements of the power receiving device 13 may be damaged.

  A current proportional to the differential pressure between the output voltage Vo of the power receiving device 13 and the input voltage of the power transmitting device 12 flows through the power transmitting coil 37. Therefore, when the output voltage Vo of the power receiving device 13 increases, the amplitude of the transmission current I1 continues to increase. As a result, there is a concern that an overcurrent flows through the power transmission coil 37. For this reason, there exists a possibility that the element of the power transmission apparatus 12 may be damaged.

  Therefore, the output voltage Vo of the power receiving device 13 is detected by the voltage sensor 49 (detection means), and when the detected value reaches a predetermined threshold value, the switches SW1 to SW4 are controlled so that the power receiving coil 38 applies to the in-vehicle battery 14. A configuration in which a short-circuit operation is performed in which the current path is short-circuited is considered. The “rectifying operation” and the “short circuit operation” will be described below.

  In the rectifier circuit 20, the source of the switch SW1 and the drain of the switch SW2 are connected to one end of the power receiving coil 38 via the power receiving filter circuit 22, and the switches SW1 and SW2 constitute the first leg. . The source of the switch SW3 and the drain of the switch SW4 are connected to the other end of the power receiving coil 38 via the power receiving filter circuit 22, and the switches SW3 and SW4 constitute a second leg. The switches SW1 and SW3 are upper arm switching elements, and the switches SW2 and SW4 are lower arm switching elements.

  In the rectification operation, the switch SW1 and the switch SW4 are turned on and off in synchronization, and the switch SW2 and the switch SW3 are turned on and off in synchronization. In the short-circuit operation, the switch SW1 and the switch SW3 are turned on and off in synchronization, and the switch SW2 and the switch SW4 are turned on and off in synchronization. In order to prevent the upper arm switching element and the lower arm switching element belonging to the same leg from being turned on at the same time, there is a dead time during which both switching elements are turned off when switching between the on and off states (opening and closing states). Is provided.

  3A and 3B show the direction of current flow during the rectification operation. In FIG. 3A, the switches SW1 and SW4 are turned on, and the switches SW2 and SW3 are turned off. In FIG. 3B, the switches SW1 and SW4 are turned off, and the switches SW2 and SW3 are turned on. The AC power supplied from the power receiving coil 38 by the rectifying operation is converted into DC and output.

  FIGS. 3C and 3D show the direction of current flow during the short-circuit operation. In FIG. 3C, the switches SW1 and SW3 are turned on, and the switches SW2 and SW4 are turned off. In FIG. 3D, the switches SW1 and SW3 are turned off and the switches SW2 and SW4 are turned on. The AC power supplied from the receiving coil 38 can be returned to the receiving coil 38 by the short-circuit operation.

  Here, when the rectifying operation is changed to the short-circuit operation, the impedance of the power receiving device 13 viewed from the power transmitting device 12 is rapidly decreased, and the voltage applied to the power transmitting coil 37 and the flowing current are rapidly changed. With the change in voltage and current, there is a concern that the power transmission coil 37 and the switches 28 to 31 constituting the inverter circuit 16 may be damaged.

  Therefore, in this embodiment, the switches SW1 to SW4 are switched from the rectifying operation to the short-circuiting operation by adjusting the on / off phase of the switches SW1 to SW4. More specifically, the on / off phase of the switches SW3 and SW4 constituting the second leg with respect to the switches SW1 and SW2 constituting the first leg is defined as the phase in the on / off control of the switches SW1 to SW4. In this case, when the phase in the rectification operation is 0 degree, the phase in the short-circuit operation corresponds to 180 degrees or -180 degrees. Therefore, the phase is changed from 0 degrees to 180 degrees or -180 degrees by shifting the phase in the positive or negative direction by a predetermined phase amount of less than 180 degrees every switching cycle, and switching from the rectification operation to the short-circuit operation I do.

  FIG. 4A shows a time change of the drive signals of the switches SW1 to SW4 during the rectification operation (phase 0 degree). FIG. 4B shows the time change of the drive signals of the switches SW1 to SW4 during the switching from the rectifying operation to the short-circuit operation (phase 90 degrees). FIG. 4C shows a time change of the drive signals of the switches SW1 to SW4 during the short circuit operation (phase 180 degrees). In the state of the phase of 90 degrees shown in FIG. 4B, half of the switching cycle is a rectification operation and half is a short-circuit operation.

  FIG. 5 shows the peak value of the received current I2 when the phase is shifted from 0 degree by a predetermined phase amount in one switching cycle. When the phase shift is 180 degrees (phase shift amount 180 degrees), the peak value of the received current I2 is the largest, and the peak value of the received current I2 is smaller as the shifted phase amount is smaller.

  FIG. 6 shows the amount of change (dVo / dt) per unit time of the output voltage Vo of the power receiving device 13 when the phase is shifted by a predetermined amount from 0 degree in one switching cycle, that is, the rate of increase. When the phase shift is not performed (phase shift amount 0 degree), the increase rate of the output voltage Vo is the largest, and the increase rate of the output voltage Vo becomes smaller as the phase shift amount is larger.

  That is, when the phase shift amount is increased, the amount of change in the output voltage Vo per unit time is reduced, while the peak value of the received current I2 is increased. Conversely, when the phase shift amount is reduced, the peak value of the received current I2 is reduced, while the change amount of the output voltage Vo per predetermined time is increased. Therefore, the phase shift is performed with a phase amount that allows switching from the rectification operation to the short-circuit operation before the output voltage Vo reaches a predetermined upper limit value. Here, the upper limit value of the output voltage Vo is set based on the breakdown voltage of an element such as the smoothing capacitor 48. With such a configuration, it is possible to suppress both the output voltage Vo from excessively increasing and the power receiving current I2 from excessively increasing.

  FIG. 7 is a timing chart showing the on / off phase change of the switches SW1 to SW4 in the present embodiment. In the present embodiment, the switching end time t1 for switching to the short-circuit operation is determined so that the output voltage Vo does not exceed the predetermined voltage, and the phase shift amount is linearly detected at the time when the switching end time t1 elapses after the phase shift is started. It was set as the structure which changes.

  FIG. 8A shows a timing chart when the phase shift control in this embodiment is performed, and FIG. 8B shows a timing when the phase shift control is performed from 0 degrees to 180 degrees in one control cycle. A chart is shown.

  At time T <b> 11, the main relays 50 and 51 are turned off due to the abnormality of the in-vehicle battery 14. When the main relays 50 and 51 are turned off, the output current Io that is a current flowing from the power receiving device 13 into the in-vehicle battery 14 becomes zero. Thereafter, the current flows into the smoothing capacitor 48, whereby the output voltage Vo of the power receiving device 13 increases. At time T12, the output voltage Vo reaches the threshold value, and phase shift control is performed. By performing the phase shift control, the increase of the output voltage Vo is stopped, and the peak value of the received current I2 is increased temporarily. Since the amount of phase shift in one control cycle in FIG. 8B is larger than that in FIG. 8A, the maximum value of the peak value of the received current I2 is large.

  The technique described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2014-79107) performs control to switch the phase in a range from 0 degrees to 180 degrees when the output voltage Vo reaches a predetermined value. Therefore, similarly to the timing chart shown in FIG. 8B, there is a concern that the peak value of the received current I2 increases transiently, and the elements of the power receiving device 13 are adversely affected. On the other hand, in the present embodiment, when the phase shift is performed, the peak value of the received current I2 is suppressed while suppressing the increase in the output voltage Vo by changing the phase of the switches SW1 to SW4 to 180 degrees after a predetermined time has elapsed. A sharp increase can be suppressed.

  In this embodiment, the operation of the rectifier circuit 20 is changed from the rectification operation to the short-circuit operation by adjusting the phase (phase shift) after fixing the switching cycle. With this configuration, the output voltage of the power receiving device 13 is suppressed without causing a rapid change in the impedance of the power receiving device 13 viewed from the power transmitting device 12 side without causing the switching element to operate at high speed as in the configuration described in Patent Document 1. It is possible to suppress an increase in Vo.

(Second Embodiment)
In the first embodiment, as shown in FIG. 7, the on / off phases of SW1 to SW4 are linearly changed. In the second embodiment, this is changed and the on / off phases of the switches SW1 to SW4 are changed as shown in FIG. Specifically, in the phase shift execution period, the phase is rapidly changed in the first half and gradually changed in the second half. By changing the phase in this way, the effect of suppressing the change in the output voltage Vo of the power receiving device 13 is improved.

(Third embodiment)
In the first embodiment, as shown in FIG. 7, the on / off phases of SW1 to SW4 are linearly changed. In the third embodiment, this is changed, and the on / off phases of the switches SW1 to SW4 are changed as shown in FIG. In the phase shift implementation period, the phase is gradually changed in the first half and the phase is rapidly changed in the second half. By changing the phase in this way, the effect of suppressing the increase in the peak value of the received current I2 is improved.

(Fourth embodiment)
In the first to third embodiments, the phase shift amount is continuously changed so as to be a predetermined value. In the present embodiment, this is changed. Specifically, the detected value of the output voltage Vo of the power receiving device 13 and the output of the power receiving device 13 so that the deviation between the detected value of the output voltage Vo of the power receiving device 13 and the threshold value of the output voltage Vo of the power receiving device 13 becomes small. Based on the deviation from the threshold value of the voltage Vo, the phase shift amount for each switching period is feedback-controlled.

  FIG. 11 is a timing chart showing the state of the phase when the control according to this embodiment is performed. In the state (A) indicated by the solid line, the rate of increase of the output voltage Vo of the power receiving device 13 is larger than in the state (B) indicated by the alternate long and short dash line. . By adopting such a configuration, it is possible to more suitably suppress an increase in the peak value of the received current I2 while suppressing a state where the output voltage Vo greatly exceeds the threshold value.

(Fifth embodiment)
The power reception control unit 70 according to the present embodiment fixes on / off control of the switches SW1 to SW4 after fixing the switching cycle of the switches SW1 to SW4 when the detected value of the output voltage Vo of the power reception device 13 falls below a predetermined threshold. By adjusting the phase at, the operation of the rectifier circuit 20 is changed from the short-circuit operation to the rectification operation. By performing such control, when the power receiving device 13 returns to a normal state, the operation of the rectifier circuit 20 can be returned from the short-circuit operation to the rectification operation.

  The power reception control unit 70 also sends the power reception device 13 from the power transmission device 12 to the power transmission control unit 60 on condition that the detected value of the output voltage Vo of the power reception device 13 exceeds a predetermined threshold over a predetermined time. Command to stop power transmission to By performing such control, power transmission from the power transmission device 12 to the power reception device 13 is stopped, and damage caused by applying an excessive voltage to the elements of the power reception device 13 can be suppressed.

  The power reception control unit 70 turns off the switches SW <b> 1 to SW <b> 4 and stops driving on the condition that the detected value of the output voltage Vo of the power receiving device 13 exceeds a predetermined threshold value for a predetermined time. Thus, by stopping the driving of the switches SW1 to SW4 and turning off all the switches SW1 to SW4, it is possible to suppress an excessive voltage from being applied to the elements of the power receiving device 13.

(Other embodiments)
The output voltage Vo of the power receiving device 13 is detected, and the detected value is compared with a predetermined threshold value. It is good also as a structure which changes this, detects the electric current which flows into switch SW1-SW4 of the power receiving apparatus 13, the input voltage of the rectifier circuit 20, etc., and compares the detected value and a predetermined threshold value.

  In the above embodiment, when the rectification operation is 0 degree, the short-circuit operation is 180 degrees, and the phase is advanced to switch from the rectification operation to the short-circuit operation. Instead of this configuration, when the rectification operation is set to 0 degrees, the short-circuit operation may be set to -180 degrees and the phase may be delayed to switch from the rectification operation to the short-circuit operation.

  In the power transmission resonance circuit 17, the power transmission capacitor 36 and the power transmission coil 37 are connected in parallel. However, this may be changed to be connected in series. In the power receiving resonance circuit 19, the power receiving coil 38 and the power receiving capacitor 39 are connected in parallel. However, this may be changed and may be connected in series.

  -The step-down circuit 15 may be omitted. In this case, the step-down operation can be realized by performing PWM control in the inverter circuit 16.

  DESCRIPTION OF SYMBOLS 10 ... Non-contact electric power feeding system, 12 ... Power transmission apparatus, 13 ... Power reception apparatus, 37 ... Power transmission coil, 38 ... Power reception coil, 49 ... Voltage sensor (detection means), 70 ... Power reception control part, SW1-SW4 ... Switch (switching element) ).

Claims (7)

A power receiving device (13) of a non-contact power feeding system (10) having a power receiving coil (38) and receiving AC power transmitted from the power transmitting coil (37) of the power transmitting device (12) in a contactless manner by the power receiving coil. There,
A rectifier circuit connected to the power receiving coil and having a plurality of switching elements (SW1 to SW4) connected in a full bridge type;
Detection means (49) for detecting current or voltage in any path of the power receiving device;
A control unit (70) for controlling the open / closed state of the switching elements and performing a rectifying operation for rectifying the AC power input from the power receiving coil;
With
The control unit adjusts the phase in the switching control of the switching element after fixing the switching cycle of the switching element on the condition that the detection value by the detection unit exceeds a predetermined threshold, An operation of the rectifier circuit is changed from the rectification operation to a short-circuit operation in which both ends of the power receiving coil are short-circuited.   The control unit sets the phase of the switching control of the switching element in the rectifying operation to 0 degree on the condition that the detected value exceeds the threshold value, and the phase ranges up to 180 degrees, or −180 degrees. The power receiving device according to claim 1, wherein the operation of the rectifier circuit is changed from the rectification operation to the short-circuit operation by adjusting to the range up to.   The control unit sets the switching control phase of the switching element in the rectifying operation to 0 degrees on the condition that the detected value exceeds the threshold value, and after a predetermined time elapses, the phase ranges up to 180 degrees. The power receiving device according to claim 1, wherein the operation of the rectifier circuit is changed from the rectification operation to the short-circuit operation by adjusting the range to −180 degrees.   4. The power receiving device according to claim 1, wherein the control unit adjusts a phase shift amount for each switching period so that a deviation between the detection value and the threshold value becomes small. 5. .   The controller controls the operation of the rectifier circuit by adjusting the phase in the switching control of the switching element after fixing the switching cycle of the switching element when the detected value falls below a predetermined threshold. The power receiving device according to claim 1, wherein the short-circuit operation is changed to the rectification operation.   The control unit includes means for instructing the power transmission device to suppress or stop power transmission to the power receiving device on the condition that the detection value exceeds a predetermined threshold over a predetermined time. The power receiving device according to claim 1, wherein the power receiving device is a power receiving device.   7. The control unit according to claim 1, wherein the control unit stops the driving by opening the switching element on condition that the detection value exceeds a predetermined threshold value for a predetermined time. The power receiving device according to item 1.