Adaptive Output Current Feedforward Control in VR Applications

Physical insight into the factors affecting the load-transient response of a buck converter

“…Similar treatments can be found quite many such as [3][4]. It was observed already in late 1980's [6,7], and confirmed also later [8][9][10][11] that the application of loadcurrent feedforward would improve the load transient response significantly. The settling time of loadcurrent response is related explicitly to the location of the output-voltage-controller zeros in [12,13].…”

Research on stability of buck converter with output-current-feedforward control

“…According to equation (5) and TABLE I, the transfer function of OCFF controller in Buck converter is shown in equation (13). It can be seen that the feedforward controller is PD control and can be realized by the circuit in Fig.6, which is consist of op-amp A, resistors 1 R , 2 R , 3 R and capacitor 1 C .…”

“…This method is widely used in Buck converter and unity-feedforward scheme is applied in the peak-current-mode-controlled converter. The dynamic characterization of Buck converter with OCFF control is analyzed in detail in [1], [3], [4], [5]. But this unity-feedforward scheme in a VM-controlled Buck converter does not give desired results due to resonant behavior of the output impedance.…”

A New Digital Adaptive Voltage Positioning Technique with Dynamically Varying Voltage and Current References

“…Manuscript 4) Flexibility: Control algorithms are described in hardware description language or other program languages, hence, the design can be easily adapted to different technologies or modified in order to meet new requirements. Existing computer-aided design (CAD) tools can be used to reduce design effort, facilitate portability to new processes, thus providing very fast time-to-market [4]- [6], [9], [12]. When digital control is applied in a processor-dedicated voltage regulator (VR), the most significant technical limitation is the delay associated with the sampling process and discrete-time computation negatively impacting the dynamic performance.…”

“…The AVP feedback control will not always keep the output voltage fixed at the same level regardless of the load current, but rather will position the output voltage at different levels according to the load, a slightly lower level at heavy load and a slightly higher at light load, thus the whole voltage tolerance range can be used for the voltage overshoot or undershoot limit during the transient, resulting in fewer output capacitors [1]- [8], [12], [13]. Both of these two digital controllers presented in [4], [5] were directly translated from their analog counterparts having the same limitations-the AVP design depends on the accuracy of the dc loop gain, and it is difficult to precisely achieve desired output impedance.…”