A High-Efficiency High-Voltage-Tolerant Buck Converter With Inductor Current Emulator for Battery-Powered IoT Devices

This article proposes a high-voltage-tolerant stacked buck converter compatible with a Li-ion battery. The proposed converter utilizes a stacked power stage with only low-voltage transistors (1.5 V) to safely convert 2.8-4.2 V battery voltage to 1 V output. The converter adopts pulse frequency modulation control in the discontinuous conduction mode to reduce power losses at light load. To maximize power efficiency for a wide range of operating conditions, the converter utilizes an inductor current emulator (ICE), which adaptively controls the peak inductor current against input voltage and load variations. The proposed converter chip was fabricated in 28-nm fully depleted silicon on insulator (FDSOI) and achieved a peak efficiency of 70% at VIN = 3.6 V (nominal Li-ion voltage), VOUT = 1 V, and ILOAD = 1 μA. By optimizing the peak inductor current depending on VIN with ICE, the efficiency can be further improved up to 4.1% when VOUT = 1 V and ILOAD = 10 μA, while ensuring small efficiency variation of 5.6% over the battery voltage range. The converter efficiently regulates 1 V output from 2.8-4.2 V input at 500 nA-1 mA load with stacked 1.5 V transistors, suitable for battery-powered IoT devices.