JP6344289B2 - Power transmission device for contactless power transmission system - Google Patents

Description

  The present invention relates to a power transmission device of a non-contact power transmission system that performs non-contact power transmission from a power transmission resonance circuit to a power reception resonance circuit.

  As a non-contact power transmission system, a system is known in which a vehicle as a power transmission target performs non-contact power transmission from the outside of the vehicle and thereby charges an in-vehicle battery. The non-contact power transmission system includes an AC power source and a power transmission coil included in the power transmission device, and a power reception coil included in the power reception device.

  The power transmission coil is installed at a predetermined position on the ground surface of the parking space, and generates alternating magnetic flux when AC is supplied from an AC power source. The power receiving coil is installed at the bottom of the vehicle, and when the vehicle is parked in the parking space, the power receiving coil is arranged facing the power transmitting coil with a space in the vertical direction, and is linked to the alternating magnetic flux generated by the power transmitting coil. AC is generated by electromagnetic induction.

  There is a concern that an overcurrent may flow through the power transmission device depending on the relative position between the power reception coil and the power transmission coil. Thus, a configuration is disclosed in which the output of the AC power supply is limited based on distance information in the vehicle height direction between the power receiving coil and the power transmitting coil (Patent Document 1).

JP 2014-121142 A

  In a so-called SS system (Series-Series), a power receiving coil is configured by connecting a power receiving coil and a power receiving capacitor in series to form a power transmission resonance circuit, and connecting a power transmission coil and a power transmission capacitor in series. As the distance between the power transmission coil and the power transmission coil increases and the coupling coefficient decreases, the current flowing through the power transmission coil and the power reception coil increases. For this reason, when the configuration disclosed in the above-mentioned patent document is applied to the SS system, when the distance between the power receiving coil and the power transmitting coil changes, overcurrent can be suppressed by stopping the output of the AC power supply, but non-contact It is difficult to continue power transmission.

  Further, for example, when the power supply target of the power receiving apparatus is a secondary battery, the voltage between the terminals of the secondary battery varies. Thus, when the voltage (load voltage) of the power supply target of the power receiving apparatus varies, the current flowing through the power transmission coil changes. In the configuration disclosed in the above-mentioned patent document, the influence of the fluctuation of the load voltage is not taken into consideration.

  The present invention has been made in view of the above problems, and continues to supply power while suppressing overcurrent when a change in the relative position between the power receiving coil and the power transmitting coil and a change in the load voltage occur. The main object is to provide a power transmission device of a possible contactless power transmission system.

  The present invention includes a semiconductor switching element (SW1 to SW4), and converts the DC power supplied from the DC power supply (11) by opening and closing the semiconductor switching element, and outputs the AC power as an AC circuit (16). ), A power transmission coil (37) and a power transmission capacitor (36) connected in series, and AC power is supplied from the inverter circuit to generate a magnetic flux in the power transmission coil, and the power reception coil is connected in series. (38) and a power transmission resonance circuit (17) that transmits power to the power reception resonance circuit (19) including the power reception capacitor (39). Provided between the inverter circuit and the power transmission resonance circuit, the impedance on the power transmission resonance circuit side viewed from the inverter circuit. And an immittance converter (18) for converting the impedance to be proportional to the admittance on the power transmission resonance circuit side, and a power transmission current estimation unit for estimating a power transmission current flowing in the power transmission resonance circuit based on an output voltage of the inverter circuit (60, 63) and an output voltage adjustment for adjusting the output voltage of the inverter circuit so that the transmission current is equal to or less than the first threshold when the estimated value by the transmission current estimation unit exceeds the first threshold. Part (60, 66, 67).

  An immittance converter is provided between the inverter circuit and the power transmission resonance circuit. The immittance converter converts the impedance on the power transmission resonance circuit side so as to be proportional to the admittance on the power transmission resonance circuit side. By this conversion, the inverter circuit and the immittance converter function as a constant current source regardless of the voltage fluctuation of the load supplied with power from the power receiving resonance circuit and the coupling coefficient between the power transmission resonance circuit and the power receiving resonance circuit. The power transmission current flowing from the immittance converter to the power transmission resonance circuit is proportional to the input voltage of the immittance converter, that is, the output voltage of the inverter circuit. For this reason, it is possible to estimate the transmission current based on the output voltage of the inverter circuit.

  Furthermore, when the estimated value of the transmission current exceeds the first threshold, the overcurrent can be suppressed by adjusting the output voltage of the inverter circuit so that the transmission current becomes the first threshold. That is, according to the present invention, when a change in the relative position between the power reception coil and the power transmission coil and a change in the load voltage occur, the power supply can be continued while suppressing the overcurrent.

The electrical block diagram of this embodiment. The figure showing the response | compatibility with the output voltage of an inverter circuit, and a duty. The figure showing the response | compatibility with the output current and input current of an inverter circuit. The functional block diagram showing the function of a power transmission control part. The flowchart showing the overcurrent determination process of this embodiment.

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

  FIG. 1 shows a non-contact power transmission system 10 in the present embodiment. The non-contact power transmission system 10 transmits the power supplied from the DC power supply 11 from the power transmission device 12 to the power receiving device 13 mounted on the vehicle in a non-contact manner. And the power receiving apparatus 13 outputs the transmitted electric power with respect to the vehicle-mounted battery 14, and performs charging. The power receiving device 13 can transmit the power supplied from the in-vehicle battery 14 to the power transmitting device 12 in a contactless manner. When power is transmitted from the power receiving device 13 to the power transmitting device 12, power is supplied from the power transmitting device 12 to a house or the like. When power is transmitted from the power receiving device 13 to the power transmitting device 12, the power receiving device 13 operates as a “power transmitting device”, and the power transmitting device 12 operates as a “power receiving device”.

  The power transmission device 12 includes an inverter circuit 16 that converts DC power supplied from the DC power supply 11 into AC power having a predetermined frequency, and a power transmission resonance circuit 17 that outputs AC power to the power receiving device 13. Here, the DC power supply 11 is an AC-DC converter that converts AC power supplied from commercial power into DC power.

  The power reception device 13 includes a power reception resonance circuit 19 to which power is supplied from the power transmission resonance circuit 17 and a rectifier circuit 20 that performs full-wave rectification on the AC power supplied from the power reception resonance circuit 19.

  The inverter circuit 16 is a well-known full bridge type inverter circuit. The inverter circuit 16 includes switches SW1 to SW4. When the switches SW1 to SW4 are alternately turned on / off (open / close controlled), the inverter circuit 16 converts the DC power supplied from the DC power supply 11 into AC power having a predetermined frequency. . Note that the switches SW1 to SW4 are IGBTs, each of which is provided with a free wheel diode.

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

  The power transmission coil 37 and the power reception coil 38 are each sealed with a flat resin together with the core. The resin that seals the power transmission coil 37, the power transmission core, and the power transmission coil 37 constitutes a power transmission pad, and the resin that seals the power reception coil 38, the power reception core, and the power reception coil 38 constitutes a power reception pad. 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 spaced apart in the vertical direction. 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 rectifier circuit 20 is a well-known full-bridge type synchronous rectifier circuit, and includes switches 44 to 47. By alternately turning on and off the switches 44 to 47, the AC power supplied from the power receiving resonance circuit 19 is changed to DC. Convert. Note that the switches 44 to 47 are MOS-FETs, each of which is provided with a free wheel diode. 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. A filter circuit including a reactor 52 and a capacitor 53 is provided between the smoothing capacitor 48 and the main relays 50 and 51.

  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 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, the ECU 80 starts power transmission from the power transmission device 12 to the 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. Communication between the power transmission control unit 60, the power reception control unit 70, and the ECU 80 is performed wirelessly, and communication between the power reception control unit 70 and the ECU 80 is performed by wire.

  In the inverter circuit 16, the source of the switch SW1 and the drain of the switch SW2 are connected to one end of the power transmission coil 37, and the switches SW1 and SW2 constitute a first leg. The source of the switch SW3 and the drain of the switch SW4 are connected to the other end of the power transmission coil 37, and the switches SW3 and SW4 constitute the second leg. The switches SW1 and SW3 are upper arm switching elements, and the switches SW2 and SW4 are lower arm switching elements.

  The inverter circuit 16 converts the DC power into AC power and outputs it when the switch SW1 and the switch SW4 are turned on and off synchronously and the switch SW2 and the switch SW3 are turned on and off synchronously. 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.

として表すことができる。ここで、Ｖｂａｔは車載バッテリ１４の端子間電圧（負荷電圧）、ｆ０はインバータ回路１６の出力周波数、ｋは結合係数、Ｌ１は一次側コイル（送電コイル３７）の自己リアクトル、Ｌ２は二次側コイル（受電コイル３８）の自己リアクトルである。 Here, in the SS-type non-contact power transmission system 10, the output current Iinv of the inverter circuit 16 is

Can be expressed as Here, Vbat is a terminal voltage (load voltage) of the in-vehicle battery 14, f0 is an output frequency of the inverter circuit 16, k is a coupling coefficient, L1 is a self-reactor of the primary side coil (power transmission coil 37), and L2 is a secondary side. This is a self-reactor of the coil (power receiving coil 38).

  That is, the output current Iinv is inversely proportional to the coupling coefficient k and directly proportional to the terminal voltage Vbat of the in-vehicle battery 14. For this reason, it is conceivable that the output current Iinv increases when the voltage between the terminals of the in-vehicle battery 14 increases or when the coupling coefficient k decreases. As the output current Iinv increases, there is a concern that an overcurrent flows through the power transmission device 12.

  Therefore, in the present embodiment, an immittance converter 18 is provided between the inverter circuit 16 and the power transmission resonance circuit 17. An immittance converter is an abbreviation for an impedance admittance converter. The immittance converter 18 converts the impedance viewed from the input end so as to be proportional to the admittance of the load connected to the output end.

  When an immittance converter 18 is provided on the output side of the inverter circuit 16 and an alternating voltage that vibrates at the resonance frequency of the immittance converter 18 is input to the immittance converter 18, the inverter circuit 16 that operates as a constant voltage source is converted into a constant current source. can do. That is, by providing the immittance converter 18, the current flowing through the power transmission resonance circuit 17 can be a constant current.

  The immittance converter 18 is a T-LCL type low-pass filter. The immittance converter 18 includes a filter coil 32 and a filter capacitor 33. Here, the inductance value of the filter coil 32 is Lf11, and the capacitance value of the filter capacitor 33 is Cf1. A part of the power transmission coil 37 is used as a filter coil of the immittance changer. That is, the inductance value of the power transmission coil 37 is the sum of the self-reactor L1 as the primary coil and the inductance value Lf12 as the filter coil. Here, Lf11 = Lf12.

Further, by making the resonance frequency of the immittance converter 18 equal to the resonance frequency of the power transmission resonance circuit 17 and the power reception resonance circuit 19, that is, the output frequency f0 of the inverter circuit 16, the inverter circuit 16 is operated as a constant current source. The power transmission from the power transmission device 12 to the power reception device 13 can be performed. That is, assuming that the output angular frequency ω0 (= 2π · f0) of the inverter circuit 16 is
ω0 · Lf11 = 1 / (ω0 · Cf1)
Thus, the inductance value Lf11 of the filter coil 32 and the capacitance value Cf1 of the filter capacitor 33 are set. That is, the product of the inductance value Lf11 of the filter coil 32 and the output angular frequency ω0 of the inverter circuit 16 is equal to the inverse of the product of the capacitance value Cf1 of the filter capacitor 33 and the output angular frequency ω0 of the inverter circuit 16. Set as follows.

When the resonance frequency is f0 and the capacitance of the filter capacitor 33 of the immittance converter 18 is Cf1, the transmission current Iim flowing from the immittance converter 18 to the power transmission resonance circuit is
Iim = 2π · f0 · Cf1 · Vinv = ω0 · Cf1 · Vinv (1)
Can be estimated as That is, the transmission current Iim can be estimated as the product of the capacitance value Cf1 of the filter capacitor 33, the output angular frequency ω0 of the inverter circuit 16, and the output voltage Vinv of the inverter circuit 16.

  In the present embodiment, the power receiving device 13 is configured such that the immittance converter 22 is provided between the power receiving resonance circuit 19 and the rectifier circuit 20. By providing the immittance converter 22 in the power receiving device 13, it is possible to suppress a decrease in transmission power even when the coupling coefficient k is decreased.

  The immittance converter 22 is a T-LCL type low-pass filter. The immittance converter 22 includes a filter coil 35 and a filter capacitor 34. Here, the inductance value of the filter coil 35 is Lf22, and the capacitance value of the filter capacitor 34 is Cf2. A part of the power receiving coil 38 is used as a filter coil of the immittance changer. That is, the inductance value of the power receiving coil 38 is the sum of the self-reactor L2 as the secondary coil and the inductance value Lf21 as the filter coil. Here, Lf21 = Lf22.

The resonance frequency of the immittance converter 22 is set equal to the resonance frequency of the power transmission resonance circuit 17 and the power reception resonance circuit 19. That is, if the inductance value of the filter coil 35 is Lf22, the capacitance of the filter capacitor 33 is Cf2, and the resonance angular frequency ω0 (= 2π · f0),
ω0 · Lf22 = 1 / (ω0 · Cf2)
Thus, the inductance value Lf22 of the filter coil 35 and the capacitance Cf2 of the filter capacitor 33 are set.

として表すことができる。ここで、ＲＬは、イミタンス変換器２２から見た整流回路２０側の抵抗成分である。 By providing the immittance converters 18 and 22 in this way, the output current Iinv of the inverter circuit 16 is

Can be expressed as Here, RL is a resistance component on the rectifier circuit 20 side viewed from the immittance converter 22.

  FIG. 2 shows the relationship between the effective value [Vrms] of the output voltage Vinv and the duty when the input voltage Vdc is a constant value. By storing the correspondence relationship illustrated in FIG. 2 as a map, the power transmission control unit 60 can calculate the output voltage Vinv based on the input voltage Vdc and the duty.

  FIG. 3 shows the relationship between the effective value [Irms] of the output current Iinv of the inverter circuit 16 and the effective value [Irms] of the input current Idc when the output voltage Vinv of the inverter circuit 16 is a constant value. By storing the correspondence relationship shown in FIG. 3 as a map, the power transmission control unit 60 can calculate the output current Iinv based on the input current Idc and the output voltage Vinv.

  FIG. 4 shows a functional block diagram of the power transmission control unit 60. The voltage detection unit 61 acquires a detection value of the input voltage Vdc of the inverter circuit 16 from the voltage sensor 40. The output voltage estimation unit 62 acquires the detected value of the input voltage Vdc from the voltage detection unit 61 and the duty from the command value setting unit 67. Then, based on the detected value of the input voltage Vdc and the duty, the output voltage Vinv is estimated using the map shown in FIG. The transmission current estimation unit 63 acquires the estimated value of the output voltage Vinv from the output voltage estimation unit 62, and estimates the transmission current Iim based on the estimated value. Here, Formula (1) is used for estimation of the transmission current Iim.

  The current detection unit 64 acquires a detection value of the input current Idc of the inverter circuit 16 from the current sensor 41. The output current estimation unit 65 acquires the detected value of the input current Idc from the current detection unit 64 and the estimated value of the output voltage Vinv from the output voltage estimation unit 62. Based on the detected value of the input current Idc and the estimated value of the output voltage Vinv, the output current Iinv is estimated using the map shown in FIG.

  The overcurrent determination unit 66 acquires the transmission current Iim from the transmission current estimation unit 63 and the estimated value of the output current Iinv from the output current estimation unit 65, respectively. Then, it is determined whether or not the estimated values of the transmission current Iim and the output current Iinv exceed the respective limiting currents Ith1, Ith2 (first and second threshold values).

  Command value setting unit 67 sets the duty of inverter circuit 16 as command value Vinv * of the output voltage of inverter circuit 16 based on the required power input from power reception control unit 70. Here, when the overcurrent determination unit 66 determines that at least one of the estimated values of the transmission current Iim and the output current Iinv exceeds the respective limit currents Ith1 and Ith2, the command value setting unit 67 The duty is set based on the estimated values of Iim and output current Iinv. That is, the overcurrent determination unit 66 and the command value setting unit 67 adjust the output voltage of the inverter circuit 16 so that the transmission current Iim is equal to or less than the limit current Ith1 when the estimated value of the transmission current Iim exceeds the limit current Ith1. It operates as an output voltage adjustment unit. The overcurrent determination unit 66 and the command value setting unit 67 adjust the output voltage of the inverter circuit 16 so that the output current Iinv is equal to or less than the limit current Ith2 when the estimated value of the output current Iinv exceeds the limit current Ith2. It operates as an output voltage adjustment unit.

  The drive circuit 68 drives the switches SW1 to SW4 of the inverter circuit 16 based on the duty set by the command value setting unit 67, thereby bringing the output voltage Vinv of the inverter circuit 16 close to the command value Vinv *.

  FIG. 5 is a flowchart showing the overcurrent determination process. The overcurrent determination process is performed by the power transmission control unit 60 at a predetermined cycle.

  In step S01, the detected values of the input voltage Vdc and the input current Idc, and the duty are acquired. In step S02, an estimated value of the output voltage Vinv is calculated based on the detected value of the input voltage Vdc and the duty. In step S03, based on the estimated value of the output voltage Vinv, the estimated value of the transmission current Iim is calculated using Equation (1). In step S04, an estimated value of the output current Iinv is calculated based on the estimated value of the output voltage Vinv and the detected value of the input current Idc.

  In step S05, the estimated value of the transmission current Iim is compared with a predetermined limit current Ith1, and the estimated value of the output current Iinv is compared with a predetermined limit current Ith2. When the estimated value of the transmission current Iim is larger than the limiting current Ith1 and the estimated value of the output current Iinv is larger than the limiting current Ith2 (S05: YES), in step S06, the excess rate EX1, of the transmission current Iim and the output current Iinv Each EX2 is calculated. Here, the ratio between the transmission current Iim and the limit current Ith1 is calculated as an excess rate EX1, and the ratio between the output current Iinv and the limit current Ith2 is calculated as an excess rate EX2 (EX1 = Iim / Ith1, EX2 = Iinv / Ith2). .

  In step S07, the excess rates EX1 and EX2 are compared. If the excess rate EX1 is greater than the excess rate EX2 (S07: YES), the command value Vinv * of the output voltage of the inverter circuit 16 is set based on the transmission current Iim so that the excess rate EX1 is 1 or less in step S08. Set and finish the process. When the excess rate EX1 is less than or equal to the excess rate EX2 (S07: NO), the command value Vinv * of the output voltage of the inverter circuit 16 is set based on the output current Iinv so that the excess rate EX2 becomes 1 or less in step S09. Set and finish the process.

  If the estimated value of the transmission current Iim is less than or equal to the limit current Ith1, or the estimated value of the output current Iinv is less than or equal to the limit current Ith2 (S05: NO), is the estimated value of the transmission current Iim greater than the limit current Ith1 in step S10? Determine whether or not. When the estimated value of the transmission current Iim is larger than the limit current Ith1 (S10: YES), in step S11, the command value Vinv * of the output voltage of the inverter circuit 16 is set so that the transmission current Iim is equal to or less than the limit current Ith1. The process is terminated.

  If the estimated value of the transmission current Iim is equal to or less than the limit current Ith1 (S10: NO), it is determined in step S12 whether the estimated value of the output current Iinv is greater than the limit current Ith2. When the estimated value of the output current Iinv is larger than the limit current Ith2 (S12: YES), in step S13, the command value Vinv * of the output voltage of the inverter circuit 16 is set so that the output current Iinv is equal to or less than the limit current Ith2. The process is terminated. When the estimated value of the output current Iinv is less than or equal to the limit current Ith2 (S12: NO), in step S14, the output voltage command value Vinv * is set so that the output power of the inverter circuit 16 becomes a predetermined value, and the process is terminated. To do.

  The effects of this embodiment will be described below.

  Regardless of the voltage fluctuation of the in-vehicle battery 14 supplied with power from the power receiving resonance circuit 19 and the coupling coefficient k between the power transmission resonance circuit 17 and the power receiving resonance circuit 19, the inverter circuit 16 and the immittance converter 18 serve as constant current sources. work. The power transmission current Iim flowing from the immittance converter 18 to the power transmission resonance circuit 17 is proportional to the input voltage of the immittance converter 18, that is, the output voltage Vinv of the inverter circuit 16. For this reason, it is possible to estimate the power transmission current Iim based on the output voltage Vinv of the inverter circuit 16.

  Furthermore, when the estimated value of the transmission current Iim exceeds the limit current Ith1, the overcurrent can be suppressed by adjusting the output voltage Vinv of the inverter circuit 16 so that the transmission current Iim becomes the limit current Ith1. Become. That is, in the configuration of the present embodiment, when a change in the relative position between the power transmission coil 37 and the power reception coil 38 and a change in the inter-terminal voltage Vbat occur, it is possible to continue power supply while suppressing overcurrent. .

  Specifically, the immittance converter 18 is a T-type third-order low-pass filter including a filter coil 32 and a filter capacitor 33. The detection value of the output voltage Vinv of the inverter circuit 16 is acquired, and the transmission current Iim is obtained using the detection value, the resonance angular frequency ω0, the inductance value Lf11 of the filter coil 32, and the capacitance value Cf1 of the filter capacitor 33. It is possible to estimate.

  More specifically, the inductance value Lf11 of the filter coil 32 and the capacitance value Cf1 of the filter capacitor 33 have a relationship of ω0 · Lf1 = 1 / (ω0 · Cf1) using the output angular frequency ω0 of the inverter circuit 16. . In this case, the transmission current Iim can be estimated as Iim = ω · Cf1 · Vinv.

  The output voltage Vinv of the inverter circuit 16 is a high-frequency alternating current and is difficult to detect. Here, since the input voltage Vdc and the output voltage Vinv of the inverter circuit 16 have a predetermined relationship, the output voltage Vinv can be estimated based on the input voltage Vdc of the inverter circuit 16. Since the input voltage Vdc of the inverter circuit 16 is direct current, it can be detected with a simple configuration. Furthermore, the output voltage of the inverter circuit 16 can be estimated based on the duty of the inverter circuit 16 in addition to the input voltage Vdc of the inverter circuit 16.

  It is conceivable that the output current Iinv and the power transmission current Iim have different amplitudes, and one of them is an overcurrent. Therefore, when at least one of the output current Iinv and the power transmission current Iim exceeds the threshold value, the larger one is suppressed below the threshold value. Here, when the output current Iinv and the transmission current Iim are both larger than the threshold, the power transmission control unit 60 as the output voltage adjustment unit, the ratio between the transmission current Iim and the limiting current Ith1, and the output current Iinv and the limiting current The output voltage Vinv is adjusted so that the larger ratio of the ratio to Ith2 is 1 or less. Thereby, both the transmission current Iim and the output current Iinv can be set to the threshold values Ith1 and Ith2 or less.

  The output current Iinv of the inverter circuit 16 is a high-frequency alternating current and is difficult to detect. Therefore, the output current Iinv is estimated based on the input voltage Vdc and the input current Idc of the inverter circuit 16. Here, the input voltage Vdc and the input current Idc of the inverter circuit 16 are DC and can be detected with a simple configuration.

  When the power receiving device 13 is mounted on a vehicle, the relative position between the power receiving device 13 and the power transmitting device 12 is likely to change. For this reason, the coupling coefficient k between the power transmission coil 37 and the power reception coil 38 is likely to change, and as a result, there is a concern that the power transmission current Iim flows excessively. In the configuration of the present embodiment, since the immittance converter 18 is used, the transmission current Iim becomes a value that does not depend on the coupling coefficient k, and the overcurrent can be suitably suppressed.

(Other embodiments)
-It is good also as a structure which abbreviate | omits the output current estimation part 65 shown in FIG. In this case, the output current Iinv of the inverter circuit 16 may be detected. And it is good to set it as the structure which an overcurrent determination part determines overcurrent based on the detected value of the output current Iinv.

  Further, the output voltage estimation unit 62 shown in FIG. 4 may be omitted. In this case, it is preferable that the output voltage Vinv of the inverter circuit 16 be detected. The transmission current estimation unit 63 may be configured to estimate the transmission current Iim based on the detected value of the output voltage Vinv and the estimated value of the output current Iinv by the output current estimation unit 65. Note that both the output current estimation unit 65 and the output voltage estimation unit 62 may be omitted.

  As the switches SW1 to SW4 that are semiconductor switching elements, MOS-FETs may be used instead of IGBTs. In this configuration, when the power receiving device 13 transmits the power supplied from the in-vehicle battery 14 to the power transmitting device 12 in a contactless manner, the power transmitting device 12 can suitably perform synchronous rectification.

  As the immittance converter, a T-CLC low-pass filter may be used instead of the T-LCL low-pass filter.

  -It is good also as a structure which abbreviate | omits the overcurrent determination of the output current Iinv.

  As the rectifier circuit of the power receiving device 13, a diode bridge may be used instead of the full bridge type synchronous rectifier circuit.

  DESCRIPTION OF SYMBOLS 10 ... Non-contact power transmission system, 11 ... DC power supply, 12 ... Power transmission apparatus, 16 ... Inverter circuit, 17 ... Power transmission resonance circuit, 18 ... Immitance converter, 19 ... Power reception resonance circuit, 36 ... Power transmission capacitor, 37 ... Power transmission coil, DESCRIPTION OF SYMBOLS 38 ... Power receiving coil, 39 ... Power receiving capacitor, 60 ... Power transmission control part, 63 ... Power transmission current estimation part, 66 ... Overcurrent determination part, 67 ... Command value setting part, SW1-SW4 ... Switch.

Claims (8)

An inverter circuit (16) that includes semiconductor switching elements (SW1 to SW4), converts the DC power supplied from the DC power supply (11) by opening and closing the semiconductor switching elements, and outputs the DC power as AC power;
A power transmission coil (37) and a power transmission capacitor (36) connected in series are provided, and when AC power is supplied from the inverter circuit, a magnetic flux is generated in the power transmission coil, and a power reception coil (38) connected in series And a power transmission resonance circuit (17) that transmits power to the power reception resonance circuit (19) including the power reception capacitor (39),
In the power transmission device (12) of the contactless power transmission system (10) comprising:
An immittance converter (18) provided between the inverter circuit and the power transmission resonance circuit, which converts an impedance on the power transmission resonance circuit side viewed from the inverter circuit so as to be proportional to an admittance on the power transmission resonance circuit side. )When,
A power transmission current estimating unit (60, 63) for estimating a power transmission current flowing in the power transmission resonance circuit based on an output voltage of the inverter circuit;
An output voltage adjustment unit (60, 66, 67) that adjusts the output voltage of the inverter circuit so that the transmission current is equal to or lower than the first threshold when the estimated value by the transmission current estimation unit exceeds the first threshold. )When,
A power transmission device comprising: The immittance converter is a T-type third-order low-pass filter including a filter coil (32, 37) and a filter capacitor (33),
The transmission current estimation unit estimates the transmission current based on an output voltage of the inverter circuit, an output frequency of the inverter circuit, an inductance value of the filter coil, and a capacitance value of the filter capacitor, The power transmission device according to claim 1. The inductance value of the filter coil and the product of the output angular frequency of the inverter circuit, the capacitance value of the filter capacitor, and the inverse of the product of the output angular frequency of the inverter circuit are equal,
The power transmission current estimation unit estimates the power transmission current as a product of a capacitance value of the filter capacitor, an output angular frequency of the inverter circuit, and an output voltage of the inverter circuit. The power transmission device described in 1. Based on the input voltage of the inverter circuit, comprising an output voltage estimation unit for estimating the output voltage of the inverter circuit,
The power transmission device according to claim 1, wherein the power transmission current estimation unit estimates the power transmission current based on an estimated value by the output voltage estimation unit.   The power transmission apparatus according to claim 4, wherein the output voltage estimation unit estimates an output voltage of the inverter circuit based on a duty of the semiconductor switching element in addition to an input voltage of the inverter circuit.   When the estimated value by the transmission current estimation unit exceeds the first threshold, or when the output current of the inverter circuit exceeds a second threshold, the output voltage adjustment unit, the transmission current and the first threshold, 6. The output voltage of the inverter circuit is adjusted so that the larger ratio of the ratio of the output current and the ratio of the output current to the second threshold value is 1 or less. The power transmission device according to claim 1.   The output current estimation unit (60, 65) for estimating an output current of the inverter circuit based on a detected value of the input voltage and input current of the inverter circuit. The power transmission device according to item.   The power transmission device according to any one of claims 1 to 7, wherein the power reception device (13) including the power reception resonance circuit is an in-vehicle power reception device mounted on a vehicle.

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