A New Improved V-Square-Controlled Buck Converter With Rail-to-Rail OTA-Based Current-Sensing Circuits

The converter proposed in this article is a new improved voltage-square buck converter using a rail-to-rail OTA-based current-sensing circuit. This circuit architecture used a constant on-time modulation mode and uses a rail-to-rail OTA-based inductor-current-sensing circuit to form a current feedback path. The rail-to-rail OTA-based current sensor has wide input range, so it can be directly connected to both the ends of the inductor. Then, a voltage loop is added to achieve fast transient response and reduce the output voltage ripple. Therefore, the proposed voltage-square buck converter responses to load current change immediately by two voltage and one current feedback signals. The converter is implemented with TSMC 0.35- μm CMOS 2P4M process, and the chip area is 2.24 mm.
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The input voltage range is 3-3.6 V. When the output voltage is 2.5 V and the output current is 350 mA, the circuit has the maximum efficiency of 91%. The contributions of this article are listed in the following: 1) we have proposed a new improved V
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control architecture of power converters, which combined current-mode control and voltage-mode control; 2) the proposed architecture has one current control loop and two voltage control loops, which can balance the output voltage and output current; 3) the proposed converter has the characteristics of faster transient response and lower transient voltage; 4) we designed, measured, and implemented this proposed converter; and 5) from the FOM formula, the performance of the proposed converter is found to be better than other recent works.