A New Digital Adaptive Voltage Positioning Technique with Dynamically Varying Voltage and Current References

A digital adaptive voltage positioning (digital AVP) technique with fast transient response for voltage regulators (VRs) is proposed in this paper. The proposed digital control architecture operates with fixed-frequency peak current mode control. Two digital-to-analog converters (DACs) are used instead of analog-to-digital converters (ADCs), thus significantly reducing system complexity. The control law is straightforward and no compensator is involved in the control loop, which greatly reduces the computation delay. Both the voltage and current references are changed dynamically at DAC clock frequency to achieve fast transient response. Furthermore, dynamic reference step adjustment method is employed to reduce the high-speed requirement on reference updating clock without compromising steady-state performance. Nonlinear control, including operation state recognition, multimode operation, decision-making and multiturn-on/turn-off control schemes, is used to minimize the transient-assertion-to-action delay and maximize the inductor current slew rate. Steady-state analysis was performed to demonstrate the digital controller operation. Finally, a two-phase 12- to 1-V, 40-A, 250-kHz synchronous buck converter with the proposed digital controller was designed to verify the theoretical analysis by simulation and experimental results.