Abstract: In the design of current-mode PWM DC-DC converters,the slope compensation method widely used to prevent sub-harmonic oscillation can significantly weaken the load capacity under a high duty cycle.The method presented in this paper reduces the slope compensation effect on the maximum inductor current.The inductor current can reach a high value even if the duty cycle is high.The load capacity is improved significantly.In the implementation,a novel multiplex comparator is used to realize the functions of three conventional comparators and some logic circuits.The power dissipation is as low as that of a conventional comparator.The circuit is concise and simple to implement.

Key words: DC-DC converter,  slope compensation,  loading ability,  multiplex comparator