Novel Sensorless Current Multimode Control for PSR Double-Clamp ZVS (DCZVS) Flyback Converter in DCM and CrCM

There are two drawbacks in the previous tri-mode variable-frequency peak current mode (VFPCM) control for primary side regulation (PSR) double-clamp zero voltage switching (DCZVS) flyback converter: firstly, the current-sense resistor leads to non-negligible loss at high power and instability at high frequency; secondly, the previous tri-mode control suffers from poor dynamic performance and lacks accurate small-signal model in various control modes. In this paper, a novel sensorless current quad-mode control is proposed, which eliminates the current-sense resistor by input voltage feed-forward and improve the dynamic performance by introducing hybrid mode (HYM) and seamless mode-switch. In addition, a unified small-signal model of the four control modes is derived in the paper, which explains the high dynamic performance of the introduced HYM. The proposed sensorless current quad-mode control and the unified small-signal model are validated on a 16-50V input and 28V/320W output experimental prototype. Compared with the traditional tri-mode peak current mode control, the undershoot recovery time and overshoot recovery time of the proposed control scheme are reduced from 12ms to 2.0ms and 12ms to 1.6ms, respectively.