A 300W 1.27kW/inch3 98.0% Peak Efficiency 48V-to-12V Switch Tank Converter Controller with Integrated Multilevel Driver and Adaptive ZCS On-time Control

Nowadays, there is a growing demand for high-power DC-DC converters with an input of 48 V intermediate bus voltage [1] –[5]. The intermediate bus voltage plays a crucial role in influencing system efficiency and power density. A high-efficiency $4: 1$ switch tank converter (STC) has been introduced as a solution. Traditional discrete approaches [1], [3] involve several external components for operation, which decrease power density. Considering the acceptable heat and integration level at 300 W -to-500W output power, maximizing the integration and power density is the contribution of this paper. Conventional cascaded bootstrap strategy results in a rapid decrease in bootstrap voltage in Fig. 1, where dual-path bootstrap gate driver has been proposed and Ron of the top power switch is still limited [5]. Moreover, the resonant frequencies of two tanks are not easily equivalent in Fig. 1, increasing the difficulty of implementing ZCS in both tanks. At a 48V DC bias, there is an almost 50% decrease in capacitance for X7R compared to C0G. These inherent properties lead to resonant tank mismatch and hard turn-off behavior when utilizing the cost-effective X7R. Traditional ZCS control can only avoid the switching noise by using large $\mathrm{V}_{\text {TH}}[6]$, which introduces obvious Poff2 loss at light load and deteriorates efficiency. However, for small $V_{T H}$ detection, additional $\Delta P_{\text {loss}}$ effect caused by the offset voltage Vos from the detector will be even worse. To address the above issues, this work proposed an integrated driver with high-precision ZCS control for a high-powerdensity $4: 1$ switch tank converter.