Liquid Crystal TV PFC Topology With Lower Output Voltage Ripple

At present, the world’s energy increasingly lack, development costs have become more and more expensive. All countries around the world are continuously working in developing the new and commutable energy. In the power supply system in this regard, proceed the AC/DC conversion from power grid is effectively. Electrical products improve the power factor or conversion efficiency to be effectively reduced energy consumption. The power factor is a very important parameter that be used to measure the power quality of the electrical equipment. Along with the global country increasingly high demand for power quality, the rapid development of technology of power factor correction. At the same time, the output voltage ripple of electronic equipment power conversion system is also very important, higher ripple will bring a lot of negative effects to the whole equipment system. The disturbance to the logical relationship of digital circuit cause the device is not working properly.An auxiliary winding with an associated capacitor is add on the single-stage power factor corrector (PFC) based on fly-back conversion to reduce the ripple on the DC output voltage. The associated capacitor takes out partial energy at every switching cycle from the fly-back conversion and releases the stored energy to the load at the valley of the rectified Line voltage. The negative effect of such an approach is that the converter does not draw a current from the AC Line at the lower voltage near zero crossing, leading to deterioration in the power factor.This thesis analyzes how an auxiliary winding affects the voltage of the associated capacitor, which in turn changes the cut-in angle of the input current and thus the power factor of the AC source. To facilitate the implementation, the fly-back converter is operated at the boundary conduction mode (BCM). A design example is given for the 24V,48W load, based on the derived equations. The laboratory circuit is built and tested to verify the computer simulations and analytical predictions. The experimental results confirm the circuit analyses on the converter performance.