Stability analysis of multiple-output dc-dc converters with cross and precise regulations

A multiple-output de-de converter using the cross regulation enables reduction in size, weight, and cost. However, the effect of the smoothing capacitances on the converter stability has not been discussed enough. Besides, the input circuit is usually required to be isolated from the output side, and the combination of a photo-coupler and a shunt-regulator is often used. However, these components have the phase delay and deteriorate the converter stability. This paper analyzes the stability of three kinds of multiple-output de-de converters using the cross regulation. In the analysis, the transfer function of the photo-coupler and shunt-regulator is estimated from the measured data. Finally, the relation between the stability boundaries of the converters and the smoothing capacitances is focused for the size reduction.