Low EMI Buck Converter with Active Current Ripple Cancellation Technique

An active current ripple cancellation (ACRC) technique is presented in this paper for achieving low-EMI buck converter. The buck converter delivers the dc output current while an ACRC circuit is in charge of generating an ac current to precisely eliminate the ripple of inductor current. Thus, the output ripple of the buck converter can be decreased significantly. A dynamic phase lock circuit and a proposed control scheme are adopted to fulfill exact ripple cancellation and guarantee the converter stability. The experimental results show that the output voltage ripple can be decreased from 200mV to 20 mV. Moreover, the effectiveness of ripple cancellation technique is independent of load current and duty cycle.