Digital Control of Voltage Regulators for Fast Transient Response in Computer Applications
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In this thesis, three techniques are proposed to enhance the transient performance of voltage regulators (VR) for computer applications. Voltage mode control with load line positioning and phase current balancing technique is first introduced to maximize the transient response of the VR and to balance the phase current for multiphase VR under high frequency dynamic load conditions. The VR and its control method is modeled and analyzed in depth for its targeting applications. Secondly, a predictive non-linear voltage mode control method is digitally implemented to further enhance the transient response of the VR. The proposed control method enables the VR to operate at a lower switching frequency in the 250KHz range for higher efficiency during steady state operation but to respond quickly accordingly to transient events when necessary. This control technique allows the use of simple VR topologies and can reduce the number of bulk capacitors. Thirdly, a VR with Transient Circuit and digitally implemented non-linear control is introduced to greatly enhance the transient response of the VR. The proposed control method allows the VR to operate at a lower switching frequency in the 250KHz range for higher efficiency under static load condition, but to respond even quickly with the aid of the Transient Circuit upon large load steps. This method allows the use of simple VR topologies and can potentially remove all the bulk capacitors. In the thesis, theoretical analysis, simulations, and experiments are given to describe and verify the proposed techniques.