Pfc Circuit Analysis And Optimization Design Of The Main Module

Modern society heavily relies on energy. With the progress of the society, the power needed for people's daily life and industry is gradually increasing. While at the same time, the growth rate of total power is not fast. So there is an urgent need to improve energy utilization. PFC circuit to improve the utilization of electricity is generated.PFC circuit can be classified as:passive and active PFC. Passive PFC is the composition of passive devices, so it is bulky, heavy, and has low power factor (0.7-0.8), which is against the light weight and high energy utilization advocated nowadays, so it is gradually eliminated; Since its development from the 20 century 90 years, active PFC has been able to reach the 0.9 power factor, and is capable for all the scope of application from small power to high power.With each country's attention of energy efficiency and the development of policy and standards for this area, the major IC companies have increased the research on the PFC circuit, and introduced many products, such as:Texas Instrument's buck typeUC3871; Siemens's buck/boost type TDA4815, TDA4818; Fairchild's Fly-back type ML4813, and so on.First, the basic principles of various PFC circuits are analyzed. Then the critical conduction mode PFC circuit used for small and medium-power is analyzed, and the basic principles and main frames of its internal modules:reference, PWM comparator, error amplifier, multiplier, zero current detection, etc., are analyzed, then the appropriate circuit structures are chosen and optimized to improve the circuit's power factor and overall performance. By using BCD technology, the main parts of the error amplifier and the multiplier modules use transistors to improve speed; the logical part uses MOS, which greatly reduces the layout area, these achieve an optimization of both speed and area. The internal reference source uses the improved bandgap reference, so multi reference voltages are achieved, which are used for protection circuit and comparator etc..The simulation uses the 1 um BCD process models of ASMC, the modules and the overall circuit are simulated, results show that this circuit works smoothly and meets the expectations.