Control scheme for EMI reduction via spread spectrum modulation for triangular current mode (TCM) DC/DC converters

Abstract:
A mixed signal control scheme for DC/DC converters operating with triangular current mode (TCM) is proposed, which leads to a reduction in EMI by simultaneously employing a spread spectrum modulation of the converter switching frequency and maintaining zero voltage switching (ZVS). This is achieved by combining an analog hysteretic current controller with random modulated thresholds generated by a digital voltage controller. By simultaneously changing two switching thresholds, the control scheme also mitigates low frequency oscillations of the output voltage which would be otherwise present. The operation mode is described in detail and validated by measurements on a prototype converter.