An integrated low power buck converter with a comparator controlled low-side switch

Here the design of an integrated buck-converter leg is presented in which the free-wheeling diode is replaced by a comparator controlled N-MOSFET. This allows eliminating the efficiency reducing voltage drop at the diode while the discontinuous conducting mode (DCM) is still applicable. For this issue, besides the control block also a fast comparator with a special offset reduction circuit is presented. A layout for a converter bridge was done and simulated which is optimized for the best efficiency at a statistically often used point of operation (3.3 V output, 27.5% duty ratio, 1 MHz, 170 mA).