A Wide-Input-Range Time-Based Buck Converter With Adaptive Gain and Continuous Phase Preset for Seamless PFM/PWM Transitions

In this paper, a wide-input-range buck converter with a dual time-based PWM and PFM control is presented. The time-based PWM control features novel line feedforward and adaptive gain techniques to speed up line transient response and keep the loop gain crossover frequency almost constant over the input voltage range. The same line-feedforward circuitry is also exploited to perform seamless transitions from PFM to PWM mode and boost efficiency at medium and light loads. A 1.4-A prototype converter with 5-to-32-V input and 3.3-V output voltage, fabricated in a 180-nm BCD process, shows a 3x reduction in the line transient response and a control loop bandwidth with limited dependence on the input voltage. PFM-to-PWM transitions are achieved with no output voltage variation thanks to the phase-shift preset. The PFM quiescent current including bias network, controller and drivers in no-load operation is 14μ A. The die area is 3.74 mm2, while the controller occupies 0.31 mm2.