A Low-Noise Fast-Transient-Response Delta-Sigma-Modulation Buck Converter With Hysteresis-Voltage-Controlled Techniques

A low-noise fast-transient-response second-order delta-sigma-modulation buck converter with hysteresis-voltage-controlled techniques is proposed. With the proposed control approach, the transient time can be accelerated by roughly 60%. The rail-to-rail OTA generates a current I-Sense, which replicates the inductor current I-L with K times. As ISense flows through the capacitor C-Sense, it will be converted into VSense. Then, the hysteresis-voltage-controlled (HVC) circuit compares the two terminal voltages of hysteresis comparator to detect the overshoot and undershoot of V-Sense. Once V-Sense is detected, the output signal of HVC circuits becomes opposite to the previous state to conduct M-P and M-N previously. Besides, the 2nd-order delta-sigma-modulation (DSM) circuit plays a vital role of mitigating noise-interference and elevating noise in whole circuits. The proposed converter has been fabricated in TSMC 0.18 mu m 1P6M CMOS processes with an active area of 1.19 x 1.09mm(2). The measured results show the transient time are 3.5 mu s and 3.2 mu s, respectively, when the load current changes between 500mA and 100mA. On the basic of the measured results of fast-fourier-transform (FFT), the value of output-to-noise ratio (ONR) is 76.6dB at the sampling frequency of 10MHz. The peak conversion efficiency is 92.1% while the load current is 300mA.