Load transient and dynamic voltage scaling (DVS) are commonly seen in the operation of the system processor. These two functions usually encounter large output voltage transient, which is hard to be quickly settled. Charge balance control is one of the prior choices that enables the converter to operate at its optimal charge/discharge slew rate so as to achieve fast transient response.The effectiveness of the optimal performance generally requires precise knowledge of the circuit parameters for charge balance computation. However, parameter drifting due to the manufacturing process may affect the performance, which is hard to implement a power integrated circuit (IC) for wide range applications. Different from the original approaches, this paper proposes an auto-tuning charge balance control (AT-CBC) to optimize load transient response and DVS of the buck converter. The auto-tuning mechanism can save the preknowledge of the output filter and avoid complex calculation in digital control. The function of AT-CBC is validated by a field-programmable gate array (FPGA) controlled buck converter. Experimental result shows that the output voltage can be settled within 3 μs for the 750-mA load step transient. For the 0.3-V DVS transient, the output voltage can be settled within 4 μs. K E Y W O R D Sauto-tuning, charge balance control (CBC), dynamic voltage scaling (DVS), digital control, DC-DC converter

Adaptive voltage positioning (AVP) scheme is widely adopted in the high-load voltage regulation modules (VRMs) because it helps VRMs reducing almost half the number of output capacitors for the same design without using AVP. The AVP scheme is claimed to be optimal if its voltage transient behaviour is linear by tuning the current sensing parameter (R i) to match the value of the output capacitor equivalent series resistor (ESR). In this study, a progressive waveform-shaping method is proposed to automatically achieve optimal AVP for the VRMs without manually setting the optimal R i. Hence, as long as a proper ESR of the output capacitor is determined, VRM designers can use the least output capacitor numbers to obtain the optimal AVP waveform. The proposed method is especially appealing for the power integrated circuit application. The overall controller design was implemented by the Taiwan semiconductor manufacturing company (TSMC) 0.18 μm manufacturing process. In the real implementation, an AVP-based buck converter was devised to perform 5 μs linear transient in response to the 10 A/5 μs load current step at 1.2 V output voltage. Test of the circuit shows that the AVP performance is comparable to those state of the art.

Single input multiple output (SIMO) buck converter is a good solution to enhance the area efficiency of the power management unit. Because the SIMO type buck converter uses only one inductor to buffer the transferred energy for the multiple output ports, it usually suffers from severe transient cross regulation in a continuous conduction mode. Most of the well-known approaches to suppress the transient cross regulation are either to create the additional free-wheeling loop or to refine the controller loop. The control logic is usually quite specific which may not apply to the other controller types controller. A phase sequence interchange (PSI) scheme is proposed to mitigate the transient cross regulation without modifying the original control design. Compared to the other techniques, the proposed method can be easily applied, but not limited to the compensatorbased control or the non-compensator-based control in the buck converter. This study starts with the illustration of the reason why the PSI can mitigate the transient cross regulation. Detail designs are then presented to implement the proposed scheme on both the compensator type and the non-compensator type controls. Experimental results show that the suppression of the cross regulation is comparable to the other state of the arts.This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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