Search

This paper introduces an accurate frequency regulation method based on a constant on-time (COT) buck regulator designed for point-of-load (POL) regulation with a fast load transient requirement and wide load range. Traditional COT regulators suffer from frequency shift due to load variations. The proposed frequency adjustment circuit helps the COT control engine to reach its target frequency of operation by adjusting the on-time pulse under varying conditions. This circuit includes a phase detector and a voltage-to-current converter block. The phase error between the target clock signal and the PWM is directly used to adjust the width of the on-time pulse. This will fine-tune the bandwidth of the frequency regulation loop, which can help to improve the transient performance of the COT as well. The fabricated chip has been tested under 20A/ $\mu \text{s}$ load transient speed with a 10A load step condition. The measured silicon performance shows that the error of the switching frequency is less than 0.16% in the 400kHz to 1MHz range during steady-state operation. [ABSTRACT FROM AUTHOR]

In this paper, hybrid dynamical systems theory is applied to the analysis and control of switched converters with Pulse-Width Modulated (PWM) inputs. The system is described by a state-space model with continuous flows and discrete jumps, without averaged equations. The modulation effects are captured in full without using time-dependent signals, by enlarging the state vector to include the PWM waveform generation process. Furthermore, the sample-and-hold mechanism associated with the sampling frequency is also taken into account with this approach. A control law is proposed based on a Lyapunov function candidate. Furthermore, convergence sets and the steady state jitter, inherent to PWM-based controllers, are analyzed estimating limit sets for the augmented state. Consequently, output chattering can be bounded. By using hybrid dynamical system theory, the control designer gains a deeper understanding of the effect of modulation in the closed-loop dynamics, avoiding the problems associated with the use averaged models. Experimental results validate the proposed method. [ABSTRACT FROM AUTHOR]

A model-based strategy for an efficient power supply control used in a wireless sensor network is presented. The strategy, based on Pulse-Skipping Modulation, regulates the current charging a battery, delivered by a photovoltaic source, resulting in an accurate current regulation and highly efficient power management. The strategy is implemented on a microcontroller unit and compensates for the microcontroller self-absorbed current. The modulation signal is generated through a full software interface, reducing the requirement for external components. Experimental validations, performed on a charger prototype by using a laboratory photovoltaic device simulator, proved that both regulation accuracy, regulation resolution and converter efficiency achieved are superior to the classic Pulse-Width Modulation. The approach results in a simple practical implementation, carries over the advantages of an up-to-date model for the photovoltaic device, and serves the auxiliary purpose of using the photovoltaic source as an instantaneous solar irradiance sensor. [ABSTRACT FROM AUTHOR]