Multiloop feedback control apparatus for DC/DC converters with frequency-shaping band pass current control

A switched mode power converter includes a periodically switched power switch which is switched under the control of a multiple loop feedback controlling the power switch in order to supply a regulated output. The output voltage and power switch current are sensed. An error voltage is generated which is representative of the deviation of the output voltage from a regulated value. A voltage derived from the power switch current is limited in its low frequency response and is then combined with the error voltage. The low frequency response of the current loop gain is used to maintain an advantageously low output impedance for the power supply. This shaped loop gain response advantageously allows accurate adjustment of the current loop gain and reduces the system to a lower order while maintaining adequate loop stability. The low frequency response may be attained by limiting the low frequency response of the sensed current or by inserting an operational amplifier in the feedback path to limit its low frequency response.