The Performance of a Digital Sliding Mode Controller in Mitigating Beat Frequency Oscillation in Voltage Regulator Modules

With the prevalence of digital signal processors and computers performing at high sampling rate, controlling physical plants digitally such as switched-mode power supplies becomes a breakthrough from the classical analog control. Voltage regulator modules (VRMs) is a special class of power supplies that operate at non-standard voltage values, high load currents, and fast load transients. Sometimes, VRMs suffer from beat frequency oscillation (BFO), wherein the load transient frequency is almost equal to the switching frequency. BFO produces high magnitude and low-frequency oscillations detrimental to the operation of the VRM. In this work, the concept of designing and implementing a digital fixed-frequency sliding mode controller to mitigate the BFO in VRMs is studied and evaluated extensively. Since sliding mode controllers are focused on achieving the correct coefficient values in stabilizing a system plant, digital controllers become more advantageous than analog controllers. Extensive simulations show that the digital fixed-frequency sliding mode controller is able to mitigate the high magnitude and low-frequency effects to the VRM while maintaining voltage regulation with minimal ripple and equal sharing among various converter phases of the VRM.