Abstract : This paper discusses several key aspects of wireless power transmission, focusing on how to achieve long-distance wireless power transmission using magnetic coupling resonance technology, and exploring the application of microprocessors in wireless power transmission control systems.
Keywords : magnetic coupling, electromagnetic resonance, wireless power transmission, microprocessor
1. Introduction: Wireless power transfer is an exciting new field offering new opportunities for manufacturers and consumers worldwide. This new field will have a major impact on market segmentation and product design, while also providing environmentally friendly and energy-efficient technologies, simplifying human interaction with infrastructure, and pioneering new approaches to device and complementary product design. As this technology reaches its peak and achieves widespread consumer adoption, engineering and design teams, wireless power transfer solution providers, manufacturers, and regulators will work closely together to ensure that current and future consumer needs are met.
2. Brief Introduction to Several Methods of Wireless Power Transmission
Currently, wireless power transmission technologies include microwave, laser, ultrasound, electromagnetic induction, and coupled resonance.
Microwave : Currently, our radio waves all use this method to transmit signals over long distances. This method can transmit signals over long distances, but it cannot wirelessly transmit high-power electrical energy.
Laser : This is an expensive, high-power wireless power transmission technology that is not suitable for practical applications;
Ultrasonic waves : Like lasers, they are mainly used in low-power detection systems;
Electromagnetic induction : This is a common method for wireless power transmission using electromagnetic induction technology. However, the leakage inductance on the primary and secondary sides is significant when the air pressure increases, which limits the transmission distance. Current research shows that this method is suitable for achieving high-power wireless power transmission within a millimeter range.
Coupled resonance : The method of wireless power transmission using electromagnetic coupling resonance technology has only recently attracted the attention of many research institutions, and has achieved high-power wireless power transmission within a meter range. We will focus on introducing this method below.
3. System Composition and Functions
3.1 System Composition
This system mainly consists of a wireless transmitting magnetic coupling resonant unit, a wireless receiving unit, a microprocessor control unit, a voltage acquisition unit, a current acquisition unit, and a host computer for monitoring and management. See Figure 1 for a detailed block diagram.
Figure 1
3.2 System Function Introduction
Wireless transmitting magnetic coupling resonant unit: This unit primarily transmits electrical energy wirelessly through magnetic field coupling. It generates resonance at different frequencies as needed. The specific resonant circuit is shown in Figure 2. In Figure 2, L1 and C14 form an LC resonant circuit, and IR2110 is a MOS transistor driver.
Figure 2
For applications requiring increased transmit power, the IR2110 can be used to drive a half-bridge resonant circuit (details will not be elaborated here).
Microprocessor control unit: It is the core of the entire wireless power transmission system. It generates high-frequency drive signals for the control system and displays the wireless power transmission status. It also processes the collected voltage/current/temperature signals and communicates with the host computer.
Voltage/Current Acquisition Unit: This unit is also crucial for ensuring stable system operation. Part of the acquisition circuitry is shown in Figure 3. This unit employs a high-precision sampling chip to acquire actual circuit parameters. The AD8210 has an input voltage range of 0-250mV, an output voltage range of DC0-4.5V, and a sampling frequency of 100kHz. This high-frequency sampling speed greatly ensures real-time data acquisition.
Figure 3
Auxiliary power supply system: In order to improve the stability of the system, the reliability of the auxiliary power supply must be ensured. The schematic diagram of the auxiliary power supply is shown in Figure 4. This circuit uses the mature UC3842 chip to provide a stable and reliable DC15V power supply to the system.
Figure 4
To improve the power factor of the entire system, a PFC circuit should be added before the system (this will not be elaborated on here). Experiments have shown that the power, efficiency, and distance of wireless power transmission are mainly related to the following factors:
A. Wireless transmitting antenna diameter: The larger the diameter, the farther the wireless transmission distance;
B. Wireless transmitting antenna wire diameter: The thicker the wire diameter, the greater the wireless transmission power;
C. Wireless transmission frequency: The higher the frequency, the farther the wireless transmission distance;
D. Wireless transmission voltage: The higher the voltage, the farther the wireless transmission distance;
E. Number of turns in the wireless transmitting coil: The more turns, the greater the power transmitted wirelessly. Based on the above experience, we used 3 turns, a wire diameter of 2.5 square millimeters, a transmission frequency of 2MHz, a transmission voltage of 600V, and an antenna diameter of 30cm to create a wireless power transmission device. It successfully lit a 200W light bulb 20cm away, as shown in Figure 5.
Figure 5
4. Program Organization Structure
Because the control algorithm is very complex, a portion of the control program will be briefly described below:
The initialization procedure is as follows:
voidMCU_init()
{
if(*(unsignedchar*far)0xFFAF!=0xFF)
{
MCGTRM=*(unsignedchar*far)0xFFAF;
MCGSC=*(unsignedchar*far)0xFFAE;
}
MCGC2=0x24;
MCGC1=0xB8;
while(!MCGSC_OSCINIT){
}
while(MCGSC_IREFST){
}
while((MCGSC&0x0C)!=0x08){
}
MCGC2=0x2C;
MCGC1=0x90;
MCGC3=0x4A;
MCGC2&=(unsignedchar)~0x08;
while(!MCGSC_PLLST){
}
while(!MCGSC_LOCK){
}
MCGC1=0x10;
while((MCGSC&0x0C)!=0x0C){}
if(SPMSC2&0x08)
{
SPMSC2|=0x04;
}
}
void TPM_init(byten)
{
(void)(TPM1C0SC==0);
TPM1C0SC=0x28;
TPM1C0VH=0;
TPM1C0VL=n; //Duty cycle
TPM1SC=0x00;
TPM1MODH=0x0;
TPM1MODL=0x51; // Period value
(void)(TPM1SC==0);
TPM1SC=0x28;
}
void ADC_init(void)
{
APCTL2=0x20; //13-channel PTB5
ADCCFG=0x24;
ADCCV=0x00U;
ADCSC2=0x00;
ADCSC1=0x2d;
}
The wireless transmission main control program uses a multi-level control method by changing the PWM duty cycle to control the wireless transmission. The duty cycle increases with the increase of system load. When there is no load, the system automatically enters the STOP mode, thereby controlling the standby current of the entire system to about 6mA.
5. Conclusion
Through research and analysis on wireless power transmission applications, this technology can be applied to mobile robots and equipment that cannot be powered by cables, and will also promote the development of electric vehicles and related industries.
References :
1. Shao Beibei's Online Development Methods for Embedded Applications of Microcontrollers [M]... Tsinghua University Press, 2005
2. Liu Shengli, Practical Technology of Modern High-Frequency Switching Power Supplies [M], Electronic Industry Press, 2001.
3. Tan Haoqiang, C Programming [M]…………………Tsinghua University Press, 1999 edition
4. Freescale 08 Series Microcontroller Development and Application Examples [M], Beihang University Press, 2009.
5. Chen Long's Research on the Application of ABB Robots and TSX57 Processors in Automobile Welding……………………………………Electrical Age 2007, 9121-124
About the author:
Chen Long, male, born in October 1977, holds a bachelor's degree and is an industrial automation engineer. He graduated from Wuhan University with a major in Electronic Engineering and is mainly engaged in the design and research of electrical automation system engineering.
