Effect of AC inductance on a phase shifted DC-DC bridge converter

Phase shifted DC-DC converters are a well established topology for producing an isolated DC output supply. However, the conventional topology with a DC output LC filter has some practical difficulties when issues such as diode reverse recovery effects, diode voltage ratings for wide ranging input voltages, and common mode EMI caused by the switched transformer output are considered. In many applications, these difficulties can be mitigated by moving the output filter inductor to the AC side before the bridge rectifier. However, this leads to alternative constraints of increased filter series voltage drop and higher filter capacitor current ripple. This paper presents design equations and a design process to determine which of these alternative filter arrangements better suits a particular DC-DC converter application.