A switched noise filter circuit for DC-DC converters which use the instantaneous output voltage to establish the converter's duty ratio. The converter cycles the switching element on and off for time intervals T_on and T_off, respectively. A switching control circuit includes a filter capacitance connected between the feedback node and ground, and a comparator which compares a feedback voltage V_fb with a fixed voltage V_ref; at least one of T_on and T_off is a "modulated" interval which is terminated when V_fb crosses V_ref due to the discharge of the filter capacitance. A switched noise filter circuit applies an offset voltage to V_fb during at least one of T_on, and T_off, with the offset voltage disconnected from V_fb by the beginning of the modulated interval or shortly thereafter. When the offset voltage is properly applied, the effect of extraneous electromagnetic noise coupled into V_fb is reduced.