Auto-tuning charge balance control for improving transient response on buck converter

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.