Adaptive Convergence Method of Notch Frequency in Noise Spread Spectrum for Pulse Coding Switching DC-DC Converter

This paper proposes an adaptive convergence method for determining notch frequency in noise spread spectrum that suits pulse coding switching DC-DC converters. Our previously proposed pulse coding switching DC-DC converter does not concentrate the switching noise into specified frequency bands, and there the noise spectrum notch of the switching pulses is present in Pulse Width Coding (PWC). Notch frequency Fn is automatically set to the frequency of the received signal by adjusting the clock frequency Fck based on Fn = (N +0.5) Fck for integer N. However, the existing technology cannot automatically track the duty cycle of the control signal. Our newly proposed adaptive convergence method here can track the duty cycle of the control signal so the output noise spectrum notch accurately set at higher frequencies. The proposal adaptively follow changes in input voltage, input frequency, and output current, and generate optimal coding pulse and notch frequencies. Clock frequency Fck is automatically generated so that notch frequency Fn appears in the middle of the harmonics of Fck. Our simulations show that our adaptive convergence method is effective for EMI reduction at high notch frequencies.