Design of a high‐precision constant voltage flyback converter

Abstract

A small-signal model is established for the basic constant voltage (CV) flyback converter firstly. Then the phase margin and the bandwidth, which can reflect the system stability and rapidity, are deduced through transfer function. The parameters affecting the stability of the system can be obtained by the model's derivation to confirm the appropriate external capacitance value. To improve the precision of CV, the compensation of cable is implemented through the module of irrigation current, pulling down the output voltage under any load conditions to the value of it with the maximal load. The prototype for the proposed CV converter has been fabricated in an MXIC 0.8 μm L80A1 process. The minimal static power consumption measured by a test is only 40 mW. In the CV mode, the precision of the output voltage can reach the level of ±1.5%. Therefore, the proposed control chip has a promising application in low power CV AC-DC flyback converter.