An APFC Converter With High EMC Based On Chaotic Spread-spectrum Technology

With the APFC technology widely used in the switching converters, the power factor of the switching converter has been greatly improved. However,the power tubes of the APFC converter working in a high-speed and cycle switching state,high rates of changes of the voltage and currentresulting in a serious EMI.The most effective way of suppressing conducted EMI is to act on the noise source. Chaotic spread-spectrum technology is such a method.It uses the wide spectrum characteristic of chaotic signals, to spread the harmonic power over a continuous spectrum, so that the circuit can have a higher electromagnetic compatibility.In this paper,we propose a new program that combined APFC technology with chaotic spread-spectrum technology. In this program, an APFC converter was designed with a high power factor and excellent EMC. This improvement can promote the power supply products to a kind of green power with excellent EMC. It’s a research has theoretical value and engineering application prospect.Firstly, based on the APFC technology, we designed a 250 W single-phase APFC converter by using average current mode and boost circuit topology. The circuit has used UC3854 as controller.Secondly, calculate the input current’s spectrum of the APFC converter which under three kinds of PWM mode, to prove the effectiveness of chaotic PWM mode theoretically. Then obtain the spectrum of the corresponding waveform by numerical and circuit simulation to verify the correctness of theoretical analysis. Thirdly, derivethe input current’s spectrum under the different chaotic spread spectrum signals, and then obtain the waveforms of the spectrum when the spread spectrum signals are Chua’s chaotic signal and tent chaotic signal by numerical and circuit simulation. Contrast the waveforms of the spectrum to discuss the relationship between the probability density function and the spreading effect of the spread spectrum signals. Finally, discuss the chaotic spread-spectrum technology’s impact on APFC converter’s electrical properties.Theoretical analysis and simulation experiments in this paper prove that the chaotic spread-spectrum technology can improve EMC of the APFC converter without changing the electrical properties of the circuit.