[C-Wireless Charging Electric Car] Shaanxi Province First Prize_Topic C

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[C-Wireless Charging Electric Car] Shaanxi Province First Prize_Topic C [Copy link]

Introduction: This car can realize the functions of wireless charging and automatic start when power is off, and can drive stably on flat ground and climb steadily on slopes. This system uses coupled mutual inductance coils to transmit high-frequency sinusoidal signals through the power management chip. The receiving system uses a full-bridge circuit for full-wave rectification to power the energy storage system; the TPS63020 chip is used to stabilize the rectified DC voltage to provide a stable voltage for the subsequent circuit system, reducing the minimum driving voltage of the power system; the TLV3501 high-speed comparator is used to control As the voltage regulator of the power system, the TPS63020 chip switches the power system. In the body part of this system, the chassis material of the aircraft model plastic is used to greatly reduce the weight of the body; the hollow cup reduction motor and the two-stage gear transmission system are used to reduce the motor speed and improve the power level of the system; the rubber material is used as the wheel outer tire to increase the friction with the ground, increase the power torque, and improve the energy output efficiency. This system can efficiently charge the farad capacitor, stably travel a long distance on flat ground, and stably climb on high-angle slopes. Entry experience: This competition is the most formal and technical technology competition we have participated in since we went to college. During the competition, I made a wireless charging car system, and the work almost perfectly realized the function. I learned a lot in this writing process, not only in terms of technical improvement, but also in this period. I understood the importance of teamwork and exercised my mentality. In the past, I only learned theoretical knowledge and had almost no practical experience. The electronics competition is a competition that combines theoretical knowledge with practical knowledge. Knowledge gained from books is always shallow. This competition has greatly improved my hands-on ability and combined many previous theories with practice. It is really a valuable experience. Next year will be the biennial tournament. After this year's TI Cup, I feel that we have matured a lot. I hope that we can achieve better results in next year's tournament.

Abstract

This car can realize the functions of wireless charging and automatic start when power is off. It can run stably on flat ground and climb slopes stably. This system uses coupled mutual inductance coils to transmit high-frequency sinusoidal signals through power management chips. The receiving system uses full-bridge circuits for full-wave rectification to power the energy storage system. The TPS63020 chip is used to stabilize the rectified DC to provide a stable voltage for the subsequent circuit system, reducing the minimum driving voltage of the power system. The TLV3501 high-speed comparator is used to control the TPS63020 chip as the voltage stabilization source of the power system to switch the power system. In the body part of this system, aviation model plastic is used as the chassis material to greatly reduce the body weight; hollow cup reduction motors and two-stage gear transmission systems are used to reduce the motor speed and improve the power level of the system; rubber materials are used as wheel outer tires to increase the friction with the ground, increase the power torque, and improve the energy output efficiency. This system can efficiently charge the farad capacitor, stably travel a long distance on flat ground, and stably climb on high-angle slopes.

Keywords: Wireless charging Automatic power control DC-DC conversion Low-quality vehicle body

1. System overall framework and solution demonstration

1.1 Overall framework of the system

The system is mainly composed of a wireless power generating device, a wireless power receiving device, an energy storage module,a DC-DC voltage stabilizing device, and a trolley power system.

The overall framework of the system is shown in Figure1:

[align= center]Figure 1 System overall framework diagram

1.2 Scheme demonstration and comparison

1.2.1 Selection of wireless energy generation device

Solution 1: Wind a multi-turn coil and use a bidirectional PWM push-pull MOS tube circuit to generate an alternating magnetic field to transfer electrical energy. After testing, the self-wound coil has low energy transfer efficiency, low electromagnetic field energy flow density, and high power consumption.

Solution 2: Generate alternating current through an existing power management IC, excite an alternating magnetic field through the coil, and transfer energy. The coil uses a yarn-wrapped coil wound by a machine on the market, which has high efficiency and good effect. Therefore, we choose Solution 2.

1.2.2 Wireless power receiving device

This system uses a machine-wound coil with the same area as the transmitting coil. The coil is made of yarn-wrapped wire with good insulation and high strength.

The receiving device performs full-wave rectification through the power managementIC and the full bridge to supply power to the farad capacitor.

1.2.3 Energy Storage Module

By measuring the efficiency of the wireless charging device, we calculated the best specification of the Farad capacitor: Three 5.5V@1Fsupercapacitors. The Farad capacitors with this specification and quantity have the lowest ratio of power to mass within 1 minute under the wireless charging system, and the power effect of the car is better. Therefore, we use Farad capacitors of this specification as energy storage modules.

1.2.4DC-DC voltage stabilizing device

This system uses the TPS63020 DC-DC chip produced by TI as the voltage stabilizing IC to stabilize the voltage provided by the farad capacitor to the optimal voltage required by the car's power system.

This chip can ensure energy supply when the voltage provided by the energy storage system is lower than the voltage required by the vehicle power system, so as to release the energy in the energy storage module to the maximum extent.

1.2.5 Vehicle power system

In order to make the power system use the energy in the energy storage system to the maximum extent, we use a hollow cup reduction motor, which is light in weight, high in speed, and low in heat, and is suitable for this system.

At the same time, we use lightweight materials to modify the car, reduce the weight of the non-power system, reduce the ratio of energy consumption to weight, and thus improve efficiency.

2. Theoretical Analysis and Calculation

2.1 Overall Theoretical Analysis of the System

Based on the previous analysis, the overall framework of this system is designed as shown in the figure below:

Figure 2 Overall framework diagram

2.2 Module circuit design and parameter calculation

2.2.1 Power transmission system

In order to improve the efficiency of wireless charging, this system uses a 5V to 12V switching power supply chip to increase the voltage supplied by the voltage-stabilized current source to 12V, and then processes the output into alternating current through a wireless charging power management chip, which is transmitted to the receiving system through the coil in the form of an alternating magnetic field.

2.2.2 Power Receiving System

We use coil mutual inductance to obtain alternating current, and then use a rectifier bridge to perform full-wave rectification and voltage stabilization to obtain stable direct current.

2.2.3 TPS63020 DC-DC Buck&Boost System We use the TPS63020 chip produced by TI, which has Boost and Buck functions and can work under larger current conditions. This system uses two TPS63020 chips. Piece one: used to stabilize the current from the farad capacitor, provide a control interface to the control system through the enable pin of the chip, and provide a stable power supply to the power system.

Piece 2: Used to stabilize the current from the farad capacitor and provide a stable power supply to the control system (TLV3501 comparator).

2.2.4 TLV3501 Control System

We use the TLV3501 Rail to Rail high-speed comparator produced by TI. Compare the voltage across a diode in the charging circuit to control the enabling status of the power system.

2.2.5 Farad capacitor energy storage device

This system uses three 5.5V@1F supercapacitors. Through the TPS63020 voltage regulation system, the capacitor can collect energy with higher efficiency and can continue to work when the voltage provided is lower than the operating voltage of the power system, thereby improving the efficiency of energy release.

2.2.6 Power System

The power system consists of a 3.3V coreless motor and a reduction gear set. The coreless motor has a small mass, high speed, a large ratio of output power to mass, and is more energy-efficient. The reduction gear set can increase the power torque of the power system and provide greater power for the car.

The rest of the car is assembled by itself, simplifying the car structure, minimizing the weight and improving energy utilization while maintaining the basic functions of the car.

3. Circuit Design

3.1 Overall Circuit Design

The overall circuit design is shown in Figure 3:

Figure 3 Overall circuit design

The wireless charging power transmitter outputs a sine wave through the power management IC, and the full-wave rectifier bridge at the receiving end modulates the AC power into DC power and supplies it to the subsequent circuit. A part of it is supplied to TPS63020, and the voltage regulator chip outputs a stable voltage to supply the TLV3501 monitoring and control system. The monitoring and control system turns off the power system when charging and turns on the power system when the power is off.

3.2 Monitoring and Control System

A monitoring and control system is constructed by a low voltage drop diode and a TLV3501 high speed comparator. The comparator compares the voltage across the diode to obtain the power supply status.

When charging, the diode is turned on, the voltage at the comparator's non-inverting input is greater than the reverse input, the comparator outputs a low level, and the TPS63020 chip that supplies the power system is disabled.

When charging stops, the diode is cut off, the voltage at the comparator's non-inverting input is less than the reverse input, the comparator outputs a high level, and the TPS63020 chip that supplies the power system is enabled.

3.3TPS63020 voltage regulation system

Figure 4 TPS63020 IC Application Circuit Diagram

TPS63020 is a DC-DC chip that can operate at a lower power consumption level while taking into account high current output. Use TPS63020 chip to construct voltage regulation

By adjusting the resistors R4 and R5 connected to the FB pin of TPS63020:

According to the above formula, Vout voltage is calculated to achieve voltage stabilization.

4. Test plan and test results

4.1 Horizontal start test plan and results

4.1.1 Horizontal Test Plan

Fix the wireless charging device on a horizontal surface and place the car in the set charging position. Start the power supply, set the supply voltage to5V and the supply current to1A. After 1 minute, turn off the power supply and start the car.

After the car stops, use a long tape measure to test the distance the car has traveled.

4.1.2 Level test results

Numbers\times	1 [/td][td=64 ] 2	3	[size =3]4 [/td ][td=64] 5	6	[align= right] 7	8	[ color=#000000]average
Distance\m	49.5 [/td][td=6 4] [colo r=#000000]48.3	51.0	[color=#00 0000]50.3	49.9	50.3 [/td][td=6 4] [color=#00 0000]50.4	50.8	5 0.1

Table 1 Horizontal test results

4.2 Slope start test plan and results

4.2.1 Slope start test plan

Fix the wireless charging device on the slope, place the car in the set charging position, start the power supply, set the power supply voltage to5V and the power supply current to1 minute later, turn off the power and start the car.

After the car stops, record the number of complete climbs of 1m and the length of the last climb. At the same time, use the mobile phone APP "Compass" to obtain the slope angle.

Test at multiple angles to obtain the angle with the highest climbing distance.

Use the following formula to calculate the climbing height.

(θ is the angle between the slope and the ground, l is the driving length)

4.2.2 Slope test results

Table 2 Slope test results

4.3 Coil transfer efficiency test plan and results

4.3.1 Coil transfer efficiency test plan

The formula for coil transfer efficiency is as follows:

η = Preceive / Psend Psend can be calculated from the data generated by the linear regulated power supply Psend = Usend x Isend Preceive The voltage Ureceive output by the rectifier bridge and the current Isend output by the rectifier bridge are calculated to obtain Preceive = Ureceive X Ireceive Fix the wireless charging device on the slope, place the car in the set charging position, start the power supply, set the supply voltage to 5V and the supply current to 1A. Connect an ammeter in series at the output point of the rectifier bridge, and connect a voltmeter in parallel between the output point of the rectifier bridge and the ground. Read the voltage and current data on the linear power supply. Read the data of the voltmeter and ammeter, and get the results as shown in Table 3.

4.3.2 Coil transfer efficiency results

Numbers	1	[align =right] 2	3	4	5	6	[align=right ] 7	8	[ color=#000000]average
Usend \V	3.33	[color=#00 0000]3.32	3.31	[color=#000000 ]3.32	[a lign=center]3.31	3.32	[size =3]3.21	3.32	[color =#000000]3.31
Isend \ A	1.00	1.00[ /size]	1.00	1. 00	1.00	1.00[/color ]	1.00	1.00	1.00[/ color]
[size=3 ]Psend \ W	3.33[/ color]	3.32[ /size]	3.31	3.32[/align ]	[align=cente r]3.31	[ size=3]3.32	[size=3 ]3.21	[color =#000000]3.32	[color=#000000 ]3.31
Ureceive[/size ] \ V	12.00[/ color]	12.00[ /size]	12.00	12.00[/align ]	[align=center ]12.00	[size =3]12.00	12.00	[color= #000000]12.00	12.00
Ireceive[/size ] \ A	[color =#000000]0.14	[color=#000000 ]0.16	0.14[ /color]	[ali gn=right] 0.14	[align=right ] 0.17	[align =center]0.19	0.16	0.16[/ color]	0.16[ /size]
P[ /size]receive \ w	1.73[/ color]	1.89[ /size]	1.62	1.73[/align ]	[align=cente r]1.99	[ size=3]2.22	[size=3 ]1.89	[color =#000000]1.96	[color=#000000 ]1.89
efficiency\% [/ td][td=45] 0.52 [/td][ td=45] [colo r=#000000]0.57	[color=# 000000]0.49	0.52 [/td][ td=45] 0.60 [/td][td=45 ] 0.67	[align =right] [color=#0 00000]0.59	0.59	0.57[/size ]

Table 3 Coil transfer efficiency test table[ /size]

[font =Microsoft YaHei, "]4.3.3 Test Analysis and Conclusion

Based on the above test data, we can draw the following conclusions:[/ size]

1. This device can be charged wirelessly with high efficiency.

2. It can receive enough electricity within the specified time.[/size ]

3. The car can climb the slope stably.

To sum up, this design meets the design requirements.

5. Appendix

Attachment 1 TPS63020 Application PCB schematic diagram

倾心思梦

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