Components of Wireless Charging Technology for Smart Cars and Simple Applications

A wireless charging smart car that can perform rapid short-term wireless charging was designed in this research. This car features energy-saving, fast, and efficient operation, with strong usability and potential for development. The CH32V307VCT6 microcontroller is used as the main controller for the smart car, and the CH32V203C8T6 microcontroller functions as a control chip for the wireless charging transmitting end. Combining the use of a super-capacitor group as an energy storage device along with the DRV8701 motor drive and corresponding sensors, it enables the smart car to accomplish wireless charging and automatic tracking. The wireless transmission terminal of this project employs an LCC compensation circuit method and an inverter circuit to achieve high-power wireless charging of 600W. The wireless charging receiver module receives and converts electrical energy to ultimately power the movement of the smart car.


Introduction
With the popularity of electric cars and the continuous development of technology, the development of charging facilities and their technology has had a profound impact on our way of travel.In particular, in recent years, wireless charging technology has received widespread attention and research, and its wide application has brought new opportunities for the development of the automobile industry.With the emergence of new energy vehicles and various wireless charging terminals, the importance of wireless charging technology is increasing daily.In the field of new energy vehicles, the introduction of wireless charging technology is extremely important.Wireless charging technology is also considered as an important solution for future car charging facilities.It can realize unconscious charging, smart charging, rapid charging and even charging while running.It is believed that in the near future, wireless charging technology will become more and more common.

Overall Design
The wireless charging smart car is divided into three parts: the vehicle body part, the wireless charging receiving part, and the wireless charging transmitting part.The vehicle body part consists of a car model, a servo, a pair of motors, a CH32V307VCT6 main control board, a DRV8701 driver board, a wireless charging receiver and various sensors.The wireless charging transmitter employs a full-bridge inverter circuit, which converts the DC power supply into AC power to change the direction of the current, thereby changing the magnetic field of the coil to achieve electromagnetic induction.The LCC compensation circuit method is used to reduce energy loss and improve charging efficiency.The wireless charging receiver also adopts the LCC compensation circuit method.Then, the obtained current is converted from AC to DC by a bridge rectifier circuit and charged to the super-capacitor through corresponding filtering.

Wireless Charging Receiver Design
To improve the receiving efficiency, an LCC compensation circuit is adopted as shown in the following diagram.The wireless charging receiver, as an energy receiving device, needs to convert the AC power obtained from electromagnetic induction into DC power to charge the supercapacitor group.Therefore, the choice was made to use four diodes to form a full bridge rectifier circuit, reversing the current located on the negative axis to form a simple DC current.Considering that the frequency of wireless charging is 150KHz, Schottky diodes with faster switching capabilities are used as the basis of the rectifier circuit.In order to achieve higher receiving power, it's necessary that the Schottky diode can accommodate sufficiently high current.The MBR60100CT Schottky diode can accommodate a pass-through current of 60A.To improve charging efficiency, two 100UF solid-state filter capacitors are connected in parallel in the DC current after rectification, which can turn the inverted current into a sawtooth-shaped current, thereby improving the charging efficiency.During the operation of the smart car, it is necessary to detect the remaining electric energy of the super-capacitor in real time, and a corresponding voltage detection module needs to be designed.In order to reduce the layout area and facilitate design, a resistive voltage division method is adopted to collect one-eleventh of the super-capacitor group voltage and detect it through the microcontroller's AD detection function.

Wireless Charging Transmitter Design
The basic principle of wireless charging is the use of alternating current generated magnetic fields, transmitted between two coils.We use a 6S battery as a direct current power source and need to design However, the reliability of the circuit composed solely of MOSFETs is not high, and there is a certain amount of dead time.It needs to be controlled by a driver chip to achieve a more precise switch.Therefore, a DGD0506A driver IC is used to precisely control the MOSFETs, and the single-chip microcomputer generates a PWM wave for control.During the operation of the MOSFETs, a large amount of heat is generated, and temperature is an important factor affecting the performance of the MOSFETs.Therefore, a heat dissipation device is needed.After various experiments with heat sinks, cold plates, heat fans, and small water-cooling devices, an energy-saving and efficient heat fan is finally used as the heat dissipation device.Below are the bridge inverter circuits on the left and right respectively.Similarly, using the LCC compensation circuit is as the receiver.The wireless charging environment involves high frequency, high voltage, and high current, so it is necessary to perform closed-loop power control.It requires the design of a voltage and current detection section at the power input.In the same way, the voltage detection part uses a method of voltage division, current sampling uses a precise 2mΩ alloy sampling resistor, and a TP181A1 current sensing amplifier is adopted.as shown in the following diagram.

Intelligent Vehicle Master Control Design
A CH32V307VCT6 microcontroller core board is used.Considering that the supercapacitor voltage will decrease as the electric energy decreases, and it cannot continue to supply power to the main control and drive circuits when the voltage is low, a TPS61288 boost circuit is first adopted at the power input to raise the supercapacitor voltage to 12V.Then, two TPS54331DDAR voltage regulator chips are used to output power supplies for the servo and other components.In order to reduce power supply ripple and improve supply stability, two AMS1117-3.3and one LM29405V chips are utilized to generate corresponding voltages for the microcontroller and various sensors.

DRV8701 Drive Design
The DRV8701 chip has high integration, excellent efficiency, strong flexibility, high reliability, simple design, and a wide input voltage range.It does not require a voltage regulator module, which reduces energy consumption.Therefore, this drive chip is adopted as the intelligent vehicle motor driver.The SN74HC125PWR chip is added as an isolation buffer chip to ensure the safety and reliability of the main control.Speed regulation is performed through PWM (Pulse Width Modulation).

LCC Compensation Circuit Parameter Design
The relevant parameters are designed using the following formula: The design of a wireless charging transmitter with a transmission power of 600W is desired.Through measurement, the basic impedance of the LCC (Inductive Capacitive Capacitive) is obtained as 24.8Ω.The input power supply is a 6s battery (24V).Through calculations, is found to be 2.632uH, is 427.83nf , 0 is the inductance of the coil at 32uH, and is calculated to be 38.34nf.The resonant inductance is composed of a Litz wire wound on a magnetic ring.In the actual wireless charging process, all parameters cannot fully reach the preset values, thus causing magnetic leakage and heat.In severe cases, it can lead to burning.Therefore, when choosing the specifications of components, it is necessary to reduce the impact of temperature on the components.Hence, capacitors made of NP0 material are used as resonant capacitors to minimize the impact of temperature on the capacitor value.They can also withstand high frequency changing currents, ensuring the stability and safety of the system.The LCC parameter design of the wireless charging receiving end is the same as the design parameters of the transmitting end.

Wireless Charging Transmitter Software Control Part
The software component consists of the PID power control section, power display section, and the wireless charging transmission switch section.Below are the related PID control formulas.

Conclusion
Overall, the wireless charging plan composed of the LCC (Inductive Capacitive Capacitive) compensation network circuit adopted in this paper is highly practical.The feasibility of the plan is high, it has a certain promotional value, and can find its place in the field of electric vehicles.By upgrading the related modules, higher power energy transmission can be achieved.However, there are still areas that need improvement.For example, the robustness of this wireless charging system is not sufficient.Strict control of various variables to achieve the desired effect is required.Further enhancements to improve adaptability and increase convenience are needed.

Figure 1 .
Figure 1.System Overall Structure Diagram

Figure 4 .
Figure 4. Left-side and right-side inverter circuitsTo make the system structure clearer and more concise, the following system framework diagram has been drawn.