Fast Output Voltage-Regulated PWM Buck Converter With an Adaptive Ramp Amplitude Control

Abstract

This brief presents a pulsewidth modulation buck converter with an adaptive ramp amplitude control. The proposed buck converter can improve the load transient response and the reference tracking speed. A chip was fabricated in a 0.18-μm CMOS technology. Measurement results showed that the overshoot/undershoot at the output during the load transient period was reduced by up to 57% for a 450-mA load current step and that the reference tracking speed was improved by up to 71% for a 1.5-V output voltage change. The measured maximum power conversion efficiency was 92.6% at 3-MHz switching frequency when input and output voltages are 3.3 and 2 V, respectively.

Physical insight into the factors affecting the load-transient response of a buck converter

“…The relation of the output-voltage loop gain to the load-current-transient performance in terms of loop magnitude and phase margin is discussed and demonstrated in [14][15][16]. The effect of adaptive modulator gain on the load-transient response is discussed and demonstrated in [17]. The role of the output capacitor and its equivalent resistor (ESR) in the transient performance and voltage-loop control bandwidth design are studied and discussed in [18][19][20][21][22].…”

Improved transient response of controllers by synchronizing the modulator with the load step: application to v2ic

“…It can be used with ripple-based controls and in applications with reference voltage tracking. Also, it can be used with constant on-time controls by adapting the ontime instead of synchronizing the clock (as seen in [23] and [24]). 6) Buck converters with low inductance get more benefit from CPSI C .…”

“…However, as said, this is not applicable in common ripple-based controls. In [24], the ramp is modulated with the output voltage to improve the transient response of a voltage mode control. As the output voltage changes with a limited slope, the response of the control still presents some delay.…”

A tri-mode high light-load efficiency BUCK converter for mobile phone application

“…BUCK modulator usually uses PWM [1,2] (Pulse Width Modulation) control under CCM (continuous conduction mode) state with large load current. When the circuit switches to light load current, the system is in DCM (discontinuous conduction mode) state, the efficiency of the circuit is affected by many factors such as dead time and is more sensitive than CCM.…”