COUPLED FILTER INOOC'OORS IN IIULTIPLE OUTPUT BUCK REGULATORS PROVIDE: DRAMATIC PERFORMANCE IMPROVEMmT

Introduction: When switching power supplies of the buck family (forward converter, full and half bridge, etc.) have more than one output as shown in Figure 1, separate filter inductors (L1,L2) are normally used in each output. These independent inductors hurt performance by decoupling and isolating the outputs from each other. Dynamic cross regulation is very poor and several other major problems are created because of the independent inductors. These problems are virtually eliminated if the inductors are coupled to each other by winding their separate coils on a single, common core [1].