The Design Of PFC Chip In Average Current Mode

Electrical energy, the most widely-used energy today, has become one of the methods to weigh the development of the country. However, the harmonic pollution in power systems would generate unfavorable effects on electrical energy, even system collapse and the loss would be quite difficult to estimate. Fortunately, through the Active Power Factor Correction technology (APFC), the power factor almost could be1and the efficiency of power supply would be also improved, which could solve the problem mentioned above effectively.A PFC chip for DC-DC converter is proposed in the paper. Firstly, the chip in average current mode could operate with continuous conduction mode (CCM) or discontinuous conduction mode (DCM). Furthermore, the chip with8chip pins is simple as well as small. In addition, the chip contains gain control module, current error amplifier, oscillator, PWM comparator, output module, band-gap reference module, under voltage protection module and so on.The chip could be widely used in LED lighting circuit applied with Flyback topology. Requirements of lighting circuit are as follow:50Hz、85V-270V AC input voltage,42V output voltage,6W output power and55KHz switching frequency.The chip with CMSC0.5um BCD craft is simulated. Meanwhile, the result shows that the chip presented in the paper has the advantages of high power factor, and the highest PF value can achieve97%in the whole work range. The chip can qualified the needs of high efficiency and low cost.