Continuous-Time Digital Signal Processing Based Controller for High-Frequency DC-DC Converters

This paper introduces a digital dual-mode controller for low-power high-frequency dc-dc switch-mode power supplies (SMPS) suitable for on-chip implementation. In steady state the controller behaves as a conventional digital PWM controller, and during transients it utilizes continuous-time digital signal processing to achieve very fast transient response. The continuous time DSP is triggered by a sudden change of output voltage. Then it performs a charge-balance based algorithm to achieve voltage recovery through a single on-off action of the power switch. The effectiveness of the method is demonstrated on an experimental 5 V-to- 2V, 400 kHz, 2.5 W buck converter that recovers voltage in the time equivalent to 3 PWM switching cycles, approaching converter physical limitations.