A Fully In-Package 4-Phase Fixed-Frequency DAB Hysteretic Controlled DC-DC Converter with Enhanced Efficiency, Load Regulation and Transient Response

Multiphase DC-DC converters have been widely used to deliver more power more efficiently with smaller ripples and faster large-signal dynamic responses [1]–[5]. In terms of closed-loop voltage regulation, traditional linear PWM control has limited small-signal bandwidth, which is further compromised to ensure stability at different loading conditions with different PVT and LC variations. Non-linear control, such as hysteretic control, does not have small-signal bandwidth limitations nor stability concerns, thus can potentially achieve a faster dynamic performance. Among different topologies, current-mode hysteretic control has been adopted in 4-phase converters [2], [3]. To ensure proper operation at higher frequency, they require careful matching between the inductor current-sensing RC networks and the inductance and parasitic DC resistance (DCR) of the power inductors [2], or more complex RC sensing networks [3]. Also, the converters in [2]–[4] did not include current balancing, which could introduce unbalanced current due to mismatches in power transistors, control timing, and power inductors among different phases, and result in significant compromise in efficiency. To maintain optimum efficiency over a wide loading range, active-phase-count (APC) control has been introduced in [1], [2], [4]. In [4], APC is realized by a multi-bit ADC, which increases the design complexity and power consumption. Double-adaptive-bound (DAB) hysteretic control in [6] has demonstrated fast transient responses, however, it only works in single phase, and the operation is very sensitive to the delay of the comparator, the gate driver and other circuits in the control path, and the matching of the RC filters, especially at higher switching frequencies. Besides, due to the lack of a high-gain amplifier, output voltage DC accuracy is also compromised in hysteretic controlled switching converters, with a 40mV/1A load regulation in [2].