Research status of parallel current sharing method for switching power supply

Current sharing technology of Dc-Dc converter is a research hotspot of modularized switching power supply. At present, there are many kinds of parallel current sharing methods for switching power supply, and each method has its advantages and disadvantages.

In the early literature on current sharing technology of switching power supply, a large part of the literature is based on the analysis and comparison of various existing parallel current sharing methods. Or only for a specific simple topology of the power supply for the parallel circuit design.

With the deepening of research on current sharing technology, some literature systematically summarizes and classifies various parallel current sharing methods from the internal principle of current sharing, and summarizes the cost, modularity, reliability and current sharing performance of current sharing methods through simulation analysis, which promotes the further development of current sharing technology.

In recent years, more and more literatures have focused on proposing new parallel current sharing methods. Such as: white main current sharing method based on voltage mode control; The white main current sharing strategy based on current mode control can design the gain bandwidth of voltage loop to be higher and improve the dynamic response of each module. These parallel current sharing methods are all improvements on the basis of the original methods, which solve some disadvantages of the original current sharing methods, but also bring some new problems. For example, the autonomous current sharing method based on voltage mode control limits the gain bandwidth of the voltage loop due to the existence of the right half plane zero of the voltage loop of the Boost converter, resulting in poor dynamic performance of each module and affecting the dynamic performance of the whole system. Although the white master current sharing method based on current mode control can design a higher gain bandwidth of voltage loop and improve the dynamic response of each module, all parallel modules in the current sharing control circuit share a voltage regulator, which reduces the reliability of the system. Moreover, the gain bandwidth of current sharing loop is limited by the narrow bandwidth of voltage loop. It is impossible for the parallel system to respond quickly to load sudden change, which affects the dynamic current sharing effect.

In comparison, the improved average current sharing method is based on the above two methods, the current sharing ring is designed inside the voltage ring, so that it is not limited by the narrow bandwidth of the voltage ring, and can better improve the dynamic current sharing effect. The method is applied to the maximum current sharing method and named as "improved maximum current sharing method".

However, most of the existing literature on paralleling multiple converters using the improved maximum current paralleling method is based on the analysis of parallel systems with simple topologies (such as Buck and Boost converters). At the same time, a set of methods combining analysis theory and concrete circuit design has not been systematically formed.