Enhancement of System Stability Based on PWFM

In this paper, the PWFM control strategy is presented, which combines the counter-based PWM control with PFM control so as to increase pseudo 1-bit resolution under constant-frequency operation. Accordingly, system stability will be enhanced. As compared with the traditional counter-based PWM, the difference in external structure between the two is quite small, and the circuit complexity and chip area are not changed. Finally, a prototype circuit is used to verify the proposed concept.