Automatic Current Balance for Multi-Phase Switching Converters with Ripple Control or Soft Switch

Abstract

This paper proposes a new multi-phase switching converter with atuotomatic current barance technique. It is well-known that the multi-phase switching converter is suitable to handle large output current with small output voltage ripple for the buck converters which use the clock pulse. This paper investigates a multi-phase controlled method for the ripple-controlled converters and the soft switching converters, that use no clock pulse; for this reason, these converters are difficult to realize multi-phase converter configurations. There are some multi-phase hysteretic controlled converters; they utilize a main clock generator or an external sub-clock pulse, which has the master-slave synchronization method. But it is difficult to respond to a frequency change of the master converter. These multi-phase converters have not considered the imbalance among phase currents caused by variations of inductors and semiconductor switches in the power stage. For the commercialized multi-phase Voltage Regulating Modules (VRMs), the inductors and the semiconductor switches are selected to adjust the balance among the phase currents. However, there is no multi-phase soft switching converter.Then we have developed the multi-phase ripple-controlled converter and the multi-phase soft switching converter with the technique of detecting 180-degree from the variable operating frequency of the main converter. Moreover, in these converters, there appears the current imbalance because of the element variations among inductors and capacitors, if some cares are not taken there. Then we have developed the automatic correction for the current imbalance by modifying the width of the Constant On Time (COT) pulse or modifying the slope of the saw-tooth signal.