Oscillator design based on frequency jitter technique

Concerning switching-mode power supply, voltage or current transformation for power conversion is conducted by high speed semiconductor device, while high voltage or current spike produced in the process of switching causes serious electromagnetic interference noises. Ordinary DC/DC converters work under fixed switching frequency mode, so the spectrum is discrete and the energy concentrate at the low frequency, commonly the noises caused in the process of switching need to be reduced by EMI filter. Frequency modulation technique in DC/DC converter for EMI suppression is studied in this paper and based on this theory current-controlled oscillator with periodic frequency modulation is introduced to suppress EMI noises, thus minimizing EMI filter component costs. The simulation results of oscillator output show high current control linearity and precise duty cycle.