A Pseudo Cross-Coupled Switch-Capacitor Based DC-DC Boost Converter for High Efficiency and High Power Density

In this paper, we propose a fully-integrated switch-capacitor (SC) dc-dc boost converter having high power efficiency, low output ripple, and high power density. It uses a switching scheme called nonoverlapped rotational time-interleaving (NORI) which eliminates shoot-through loss as well mitigates the adverse effect of dead times between successive charging and discharging phases which results into a small ripple. A basic cross-coupled voltage doubler has been adopted to implement the NORI scheme working over a wide range of switching frequencies. Dynamic adjustment of the frequency provides high power density as well as maintains high power efficiency over a wide load current range. The proposed converter has been fabricated in 0.18-mu m CMOS thick gate process for 3.3 to 5.5 V conversion and output ripple not more than 0.5% of the output voltage. The converter uses only 440 pF to deliver up to 25 mA at 5.3 V regulated output. The measured peak power efficiency is 89% at 20 mA for unregulated output. With mixed mode regulations, the measured efficiency of the converter including analog blocks is 83.5% at 15 mA, while the overall efficiency is 75%. Power density of the designed converter is more than 0.85 W/mm(2) considering the capacitor area.