Research And Design Of High-Efficiency Elec Tric Iron Based On High-Frequency Eddycurrent Mode

Electric iron is a necessary tool in electronics production and electrical maintenance. It is used to weld electronic components and wires. With the continuous improvement and development of society, science and technology are advancing rapidly, the updating speed of electronic equipment becomes faster and faster. Integration of electronic components have become more sophisticated, thus the requirement for welding techniques have become increasingly demanding, and the performance requirements on electric iron are also rising. However, traditional electric iron adopts indirect heating. The heat transfer efficiency from heating core to soldering iron tip is low. Most of the heat is emitted into the air, so the energy wastes seriously. In addition, due to the slow speed of heating soldering iron tip, it has to wait a long time to use each time. What’s more, vulnerability rate of the soldering iron tip is higher as electric iron is in the empty burning state for a long time. Finally, the electrostatic, as leakage phenomenon is easy to occur, so if the selection of the electric iron is improper, accident is easy to occur in the process of welding. Aiming at the above problems, design of high efficiency electric iron based on eddy current mode is proposed.Firstly, in order to improve the heating efficiency and achieve rapid heating, this dissertation adopted the way of heating the soldering iron tip directly. Since the soldering iron tip is small, inductance is very small and magnetic core is easily saturated, so it is difficult to inject large power energy. Power heater based on resonant mode is designed to solve the problem. The power heater adopt half bridge series resonant inverter topology, the drive part use special half bridge driver chip SG3525 and NCP5181 with high working frequency.Secondly, as the inductance of the induction heating coil varies with the heating temperature, the resonant frequency also change, so working frequency deviates from resonant frequency in the heating process, which results in low heating efficiency. Therefore, voltage controlled oscillator (VCO) using CD40106 is designed. The VCO input control range of voltage, so the working frequency can track resonant frequency automatically, and the power also can adjust automatically. In addition, temperature control, setting and display circuit is designed.Thirdly, in order to protect the electric iron from in the state of empty burning for long time, pyro-electric infrared V-PWM converter based on integral mode is designed. The V-PWM converter can detect people working state, and power can be off automatically when people leave long time. Ultrasonic communication circuit designed tests the using state of electric iron, it can be heated rapidly when reused.Finally, in order to overcome electrostatic, leakage phenomenon, reduce electromagnetic radiation and enhance the power factor, high power factor converter with step-down function is put forward.According to the experimental results, compared with the traditional electric iron the proposed high efficiency electric iron based on eddy current mode improved the heating efficiency obviously, and heating time is shortened clearly. At the same time, reducing the electromagnetic radiation and electromagnetic harmonics, and the power factor reached more than 95%.