Fast Transient (FT) Technique With Adaptive Phase Margin (APM) for Current Mode DC-DC Buck Converters

Abstract

This paper proposes a fast transient (FT) control with the adaptive phase margin (APM) to achieve good transient response in current-mode DC-DC buck converters at different load conditions. The overshoot/undershoot voltage and the transient recovery time are effectively reduced. The APM control can always maintain the system phase margin at an adequate value under different load conditions. That is, the compensation pole-zero pair is adapted to load current to extend the system bandwidth and get an adequate phase margin. Experimental results show the overshoot/undershoot voltage is smaller than 60 mV (3%) and transient period is smaller than 12 s as load current suddenly changes from 100 to 500 mA, or vice versa. Compared with conventional designs without any fast transient technique, the undershoot voltage and recovery time are enhanced by 45% and 85%, respectively. Index Terms-Adaptive phase margin (APM), fast transient (FT), loop bandwidth, pole-zero cancellation, stability.

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

“…The settling time of loadcurrent response is related explicitly to the location of the output-voltage-controller zeros in [12,13]. 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].…”

A Low EMI DC-DC Buck Converter with a Triangular Spread-Spectrum Mechanism

“…In general, fixed operating frequency control and variable operating frequency control are used in the switching regulator. Switching regulators with fixed operating frequency include both voltage mode control [1,2] and current control mode [3][4][5]. Fixed operating frequency control mechanisms must utilize an error amplifier and additional compensation components to stabilize the output voltage of the DC-DC buck converter.…”

A 40nm CMOS Hysteretic Buck DC-DC Converter With Digital-Controlled Power-Driving-Tracked-Duration Current Pump

“…Some of them focus on speeding up the controller stage at the expense of increased system complexity. Although the adaptive bandwidth compensation techniques [24], [25] and the capacitor multiplier techniques [26] aim to extend the compensated bandwidth, their transient responses are still limited by the OTA bandwidth through the frequency compensation in compromising overall closed-loop stability. In addition, V 2 converters are successful by introducing the feedforward path to bypass the slow error amplifier (EA) [12], [18], [27], but this approach may suffer from the subharmonic oscillation [8], [27].…”