A 1-A 90% Peak Efficiency 5-36V Input Voltage Time-Based Buck Converter With Adaptive Gain Compensation and Controlled-Skip Operation

Compared with analog and digital controls, time-based control makes it possible to reduce both area occupation and power consumption, especially in converters operating at high switching frequencies. In this article, we present a time-based buck converter with a wide input voltage range for general-purpose applications. A controlled-skip operation is embedded in the proportional-integral-derivative controller to increase the light-load efficiency. To avoid large variations of the open-loop crossover frequency caused by the input voltage ranging from 5 to 36V, an adaptive compensation of the controller gain is adopted based on a novel design methodology. These solutions are verified with a prototype buck converter implemented in a 0.18-mu m bipolar-CMOS-DMOS (BCD) process, which provides an output voltage of 3.3V and a load current capability of 1 A. The measured converter peak efficiency is 90%. The efficiency is increased from 48% to 70% at 10-mA load current and 5V input voltage, when the converter operates in a controlled-skip mode. The seamless transition between the two operation regimes is guaranteed by a finite-state machine logic, without requiring a dedicated circuit. The crossover frequency varies only by a factor of 1.8 over the input voltage range and a line regulation of 0.33 mV/V is obtained.