Dual mode digital buck converter controller without current sensor

The common buck converter is used the pulse width modulation (PWM) mode under the heavy load and the pulse frequency modulation (PFM) mode under the light load to obtain the high efficiency. The control method, switching the PWM mode and the PFM mode automatically depend on the different loads, needs the current sensor to judge whether the inductor current is zero or not. The paper uses the no current sensing technology which switches the two modes automatically without the current sensor. Use the field programmable gate array (FPGA) to verify the functions and implement a buck converter which has 3∼4.2 V input voltage, 1.2 V output voltage and 86 % highest efficiency under 0.5 A output current. After the FPGA verification, the control circuit has been implemented in TSMC 1P6M 0.18 μm CMOS technology.