Design of a low EMI boost converter using bi-frequency PFM control mode

A bi-frequency PFM controlled boost DC-DC converter is designed and implemented in this paper to improve the electro-magnetic interference (EMI) and efficiency of the system in a wide load range. The spectral energy of proposed bi-frequency PFM controlled converter is distributed to more frequency points to decrease the discrete harmonic peak, achieving low EMI. A control IC for the boost converter has been fabricated in Founder Microelectronics 0.5μm CMOS process. Experimental results show that the full-load conversion efficiency is over 80%, and the converter has fine EMI characteristics.