CONTACTLESS ENERGY TRANSFER FOR VEHICLES

Abstract

Inductive charging system (10), comprising: an inductive charging circuit including a switching device configured to switch between a boost converter (104) and a buck converter (102); and a controller configured to selectively actuate the switching device to switch between the boost converter (104) and the buck converter (102) based on the presence or absence of a load, characterized in that an output of the buck converter (102) includes a forward biased diode (116) for backfeed protection.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a contactless energy transfer for vehicles. BACKGROUND

[0002] Electric or hybrid electric vehicles are regularly charged to recharge their power sources. The vehicles are typically charged using a direct connection or contactless power transfer. The primary or power source side of a contactless power transfer system can generate electric and magnetic fields. Directives and regulations regulating exposure to these energy fields have been implemented.

[0003] The document US 2016 / 0 094 081 A1 describes an inductive charging system comprising an inductive charging circuit including a switching device configured to switch between a boost converter and a buck converter, and a controller configured to selectively actuate the switching device to switch between the boost converter and the buck converter based on the presence or absence of a load. SUMMARY

[0004] An inductive charging system may include an inductive charging circuit with a switching device configured to alternate between a boost converter and a buck converter. The inductive charging station or the vehicle's inductive charging system may include a regulator configured to actuate the switching device to switch between the boost converter and the buck converter based on the presence or absence of a load. The boost converter may be a boost converter. The buck converter may be a buck converter. The buck converter may have a maximum power output of 100 W. An output of the buck converter may include a forward-biased diode for backfeed protection.The regulator may further be configured to ramp an output voltage of the buck converter from a coupling voltage to a charging voltage to prevent hard switching between the boost converter and the buck converter. A charging voltage of the battery and an output voltage of the boost converter may be the same. The regulator may further be configured to ramp an output voltage of the buck converter to a battery voltage to prevent hard switching when a battery is connected to a secondary side of the inductive charging circuit. The boost converter may be a power factor correction (PFC) boost converter. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 depicts a vehicle near a charging station with a primary side; Fig. 2 depicts a primary side of a charging station or charging system of a vehicle; Fig. 3A depicts a buck converter; Fig. 3B depicts a boost converter; Fig. 4 depicts a primary side and a secondary side of an inductive charging system; and Fig. 5 is a flow diagram of an inductive charging system. DETAILED DESCRIPTION

[0005] Embodiments of the present disclosure are described herein. It should be understood, however, that the disclosed embodiments are merely examples, and other embodiments may take various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or reduced to show details of particular components. Accordingly, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.Those of ordinary skill in the art will understand that various features illustrated and described with respect to any of the figures may be combined with features illustrated in one or more other figures to produce embodiments not explicitly illustrated or described. The illustrated combinations of features provide representative embodiments for typical applications. However, various combinations and modifications of the features consistent with the teachings of this disclosure may be desirable for particular applications or implementations.

[0006] Vehicles can be powered by battery electric vehicles (BEVs) or a combination of energy sources, including battery electric vehicles. For example, hybrid electric vehicles (HEVs) are being considered, whose powertrain is powered by both a battery and an internal combustion engine. In these designs, the battery is rechargeable, and a vehicle charger provides energy to recharge the battery after it has been discharged.

[0007] An electric vehicle can be charged via an inductive charging circuit. The inductive charging circuit can include a primary side and a secondary side. The primary side refers to the circuit that connects the electrical grid to the primary coil. The secondary side refers to the circuit that connects the secondary coil to the vehicle's battery bus. The inductive charging circuit can include a switching device or set of controlled switches for alternating between a boost converter and a buck converter. The controller can be configured to selectively actuate the switching device to switch between the boost converter and the buck converter based on the presence or absence of a load. The load can be detected through data communications between the vehicle and the primary side controller.The vehicle may include a communication controller for detecting the amount of energy transferred to the secondary coil. The vehicle may send this information to the primary-side controller, which may determine coupling coefficients related to the energy supplied to the primary coil.

[0008] The boost converter may be a step-up converter. The boost converter may be a buck converter. The boost converter may provide power factor correction to achieve a desirable power factor (i.e., real power transfer). The buck converter may be a buck converter. The buck converter may also be a linear voltage converter. For example, the buck converter may include a Zener diode or voltage divider design. The buck converter may have a maximum power output of 100 watts. The step-down converter may have a lower maximum than 100 watts. The power output of the buck converter may only be rated at a level sufficient to ensure adequate coupling and energy to balance the voltage with the battery and the boost converter, as described herein.The buck converter may include a forward biased diode for backfeed protection.

[0009] Due to the nature of the primary and secondary side switches, the regulator can be designed to vary the buck converter's power and voltage output to prevent hard switching when higher-voltage devices are connected to the circuit. For example, a vehicle's battery bus may have a higher voltage than necessary to promote balancing of the primary and secondary side coils. Before closing the circuit, the buck converter can increase its power output to raise the secondary side voltage to a level similar to that of the battery bus.

[0010] With reference to Fig. 1, a vehicle charging system according to one or more embodiments is illustrated and generally designated by reference numeral 10. Inductive charging is used to provide power to a vehicle 14 from a vehicle charger 12 to recharge the battery. A charging station 16 is shown receiving the vehicle 14 to be charged by inductive charging. The vehicle 14 docks at the charging station 16, which houses the vehicle charger 12. The vehicle charger 12 can be connected to receive ordinary electrical power, such as that available in a typical home garage.

[0011] The vehicle 14 includes a secondary coil housed within an inductive charging plate 18 located underneath the vehicle 14. The vehicle's secondary inductive charging plate 18 is electrically connected to the vehicle's battery. The vehicle 14 also includes an AC / DC power converter to rectify and filter the AC power received from the vehicle charger 12 into DC power to be received by the battery. The vehicle charger 12 is located in the floor beneath the vehicle 14 and includes a primary charging coil housed within a corresponding primary inductive charging plate 20. The primary inductive charging plate 20 is generally horizontal and spaced apart from the vehicle's secondary inductive charging plate 18.The primary induction charging plate 20 can be height-adjustable to create a suitable gap to enable charging of the vehicle 14. An electrical current is supplied to the primary coil, creating an electromagnetic field around the primary induction charging plate 20. When the vehicle's secondary induction charging plate 18 is near the charged primary induction charging plate 20, it receives energy because it is within the generated electromagnetic field. Current is induced in the secondary coil and subsequently transferred to the vehicle battery, creating a charging effect. The gap between the plates allows for variation in vehicle orientation and also accommodates other eligible vehicles with different ground clearances.

[0012] In an alternative embodiment (not shown), the primary induction charging plate of the charging station is designed to be located in a generally vertical position, for example, on or near a vertical wall. The vehicle would include a corresponding secondary induction charging plate on a front or rear vertical portion, for example, as part of a front or rear bumper. The primary and secondary induction charging plates approach each other as the vehicle is driven to the charging station and parked in a designated charging position. An intentional gap, partly due to variation in the vehicle's parking position, would again be provided between the primary and secondary induction charging plates.

[0013] At this point, Fig. 2, which shows a primary side 100 of the inductive charging system. The primary side includes a rectifier 106 that converts the AC source to a time-varying unipolar signal. When a load is present, the primary system 100 is designed with switch 118 closed. Switch 118 closes the circuit to allow the buck converter 102 to be used. The buck converter reduces the power output of the inductive primary coil 114 to limit electromagnetic radiation. The buck converter may have a maximum output of approximately 50 watts. The buck converter may be a buck converter that uses the inductance to limit the rate of change of current passing through the inductor. Other linear regulation devices may also be used to step down the source voltage (e.g., shunt regulators or series regulators using a Zener diode).The step-down signal is used to power inverter 110. Inverter 110 can generate a waveform between 80.13 kHz and 90 kHz—preferably 85 kHz—which meets the requirements of the Society of Automotive Engineers. A stabilizer 112 can be included to improve power transfer efficiency. Stabilizer 112 can be single-ended or double-ended and connected in series or parallel.

[0014] The presence of a vehicle can be determined through data communications, proximity detection, or coupling coefficient measurement. Upon detection of the vehicle, a controller can selectively actuate a switching device to switch between boost converter 102 and buck converter 104. That is, the controller can turn on boost converter 104 by closing switch 120. The controller can keep switch 118 of buck converter 102 closed until the boost converter 104 circuit is closed by switch 120. Buck converter 102 can be ramped up to the operating voltage of boost converter 104. The output voltage of the boost converter can be above the peak AC line input voltage. Typically, the operating voltage of the boost converter is 400-450 volts.Although buck converter 102 does not have the capacity to power the entire load, it is capable of increasing its output voltage to match the output of boost converter 104 to ensure smooth switching. After the circuit containing boost converter 104 is closed, switch 118 of buck converter 102 can be opened. The buck converter 102 circuit includes a half-wave diode 116 to ensure that boost converter 104 does not backfeed buck converter 102 when both circuits are closed. The boost converter 104 circuit includes an energy storage capacitor to regulate the boost converter output. Switching between converters can occur without ramping and can occur upon an indication that a load is present.

[0015] At this point, Fig. 3A, in which a buck converter 102 is depicted as including a switch 150 for regulating the output current, a diode 154 for regulating the current flow, an inductor 152 for limiting the rate of change of the current using a magnetic field, and an output 156. As shown in Fig. 3B, a boost converter 104 is shown. The boost converter includes an inductor 170 for limiting the rate of change of current using a magnetic field, a switch 172 for regulating the output current, a diode 174 for regulating the flow of electrons through the circuit, and an output 176. The switches 150, 170 can be controlled by a controller to appropriately regulate the output of each converter.

[0016] At this point, Fig. 4, which depicts a primary side 100 and a secondary side 200 as discussed above. The primary side 100 and the secondary side 200 are coupled using respective inductors 114. The secondary side 200 includes a stabilizer 212, a rectifier 206, and an impedance converter 202. The buck converter 102 may be used to boost the secondary side voltage to prevent hard switching when the switch 210 is closed to connect the battery 204. For example, the buck converter 102 may be used to power the inverter 110 to boost the secondary side voltage to the battery terminal voltage or the battery electrical bus voltage.

[0017] At this point, Fig.5, which shows a flow method 300 for the contactless power transfer system. The method begins at step 302. At step 304, the buck converter is turned on to generate a low-energy inductance from the primary coil. At step 306, detection is performed, either by direct communication with the vehicle and calculation or by estimating the coupling coefficient based on a position of the vehicle. The load is aligned at step 308. At step 310, the controller may increase the buck converter energy so that the secondary bus voltage is equalized with the voltage of an unconnected battery bus to prevent arcing caused by large voltage differences between the battery bus and the secondary circuit connection. At step 312, the controller waits until the secondary circuit voltage is equalized with the battery bus voltage.The buck converter voltage can be increased by increasing the pulse width or frequency of the signal sent to the buck converter's switch. After the voltages are equalized, the regulator closes the switch to connect the secondary circuit and the battery in step 314. In step 316, the buck converter increases its own output voltage by increasing the pulse width of the switch signal. The buck converter output voltage is mapped to the boost converter's nominal output voltage. In step 318, the regulator hangs until the buck converter's voltage output equals the boost converter's voltage. Once the voltages are equalized, the boost converter's high-energy circuit is closed in step 320. Then, in step 322, the battery is charged. The method may end at 324.The method may also repeat all or part of the process to properly provide adequate power transfer when a load is present and minimal electromagnetic radiation when no load is present.

[0018] The terms used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the disclosure. As previously described, the features of various embodiments may be combined to form other embodiments of the invention that may not be expressly described or illustrated.While various embodiments may be described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, one of ordinary skill in the art will recognize that one or more features or characteristics may be compromised to achieve the desired overall system attributes, depending on the particular application and implementation. These attributes may include, but are not limited to, cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, operability, weight, manufacturability, ease of assembly, etc.As such, embodiments that are described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure and may be desirable for certain applications.

Claims

[1] Inductive charging system (10), comprising: an inductive charging circuit including a switching device configured to switch between a boost converter (104) and a buck converter (102); and a controller configured to selectively actuate the switching device to switch between the boost converter (104) and the buck converter (102) based on the presence or absence of a load, characterized by , that an output of the buck converter (102) includes a forward biased diode (116) for backfeed protection. [2] The system (10) of claim 1, wherein the boost converter (104) is a boost converter. [3] The system (10) of claim 1, wherein the buck converter (102) is a step-down converter. [4] The system (10) of claim 3, wherein the buck converter has a maximum power output of 100 W. [5] The system (10) of claim 1, wherein the regulator is further configured to ramp an output voltage of the buck converter (102) from a coupling voltage to a charging voltage to prevent hard switching between the boost converter (104) and the buck converter (102). [6] The system (10) of claim 5, wherein the charging voltage and an output voltage of the boost converter (104) are equal. [7] The system (10) of claim 1, wherein the regulator is further configured to ramp an output voltage of the buck converter (102) to a battery voltage to prevent hard switching when a battery is connected to a secondary side of the inductive charging circuit. [8] The system (10) of claim 1, wherein the boost converter (104) is a power factor correction boost converter. [9] System (10) comprising: an inductive charging circuit including a switching device configured to switch between a power converter and a power factor correction (PFC) converter; and a controller configured to operate the switching device to turn on the PFC converter and turn off the power converter in response to the presence of a load, and to operate the switching device to turn on the power converter and turn off the PFC converter in response to the absence of a load, wherein the PFC converter is a boost converter and the power converter is a buck converter with a maximum power output of 100 W, characterized by , that an output of the buck converter includes a forward-biased diode for backfeed protection. [10] The system (10) of claim 9, wherein the regulator is further configured to ramp an output voltage of the buck converter from a coupling voltage to a charging voltage to prevent hard switching between the boost converter and the buck converter.

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