Step-down Switching Regulator Research Articles

MEMS Switching Voltage Regulator Using a Normally-On Electret Relay

We report on a DC/DC step-down switching regulator using a microelectromechanical systems (MEMS) switch for the first time. The output voltage developed in a storage capacitor is used as a feedback control voltage for the electrostatic actuator that drives a micromechanical contact switch inserted between the rectifier and the capacitor. The switch is configured to be normally-on owing to the electrostatic potential remaining in the electret film on the electrodes. When the output voltage exceeds and the feedback control voltage cancels the built-in potential of the electret, the differential voltage acting on the actuator becomes small and the contact is opened, thereby decoupling the rectifier from the storage capacitor. When the output voltage becomes low, on the other hand, the net differential voltage becomes large and the contact is closed again, thereby reconnecting the rectifier to the capacitor and recovering the voltage. Fast repetition of this sequence maintains the DC voltage of the storage capacitor at a constant level. For demonstration, an electret film that is pre-charted to 240 V is used to regulate the output voltage in a range between 12 V and 14 V. Different from the switching regulators using transistors, the MEMS regulator does not require any bias current for operation, being suitable as a low-power voltage regulator for environmental energy harvesters. [2021-0220]

Regulation characteristics of the step-down switching regulator which operates оn a rechargeable battery

The aim of the work is to study the peculiarities of the operation of a step-down switching regulator in the case, when a battery operating in a buffer mode is connected to its output. The analysis of its regulating characteristics in the case of presence and absence of a capacitor of a large capacity at the input of the regulator was carried out. It is noted that in the presence of a battery at the output of the voltage regulator, the latter will operate in the mode of regulating the output current (battery charging current). It is shown that in order to ensure the maximum possible energy transferred from a source of electrical energy to a battery, a capacitor with a sufficiently large capacitance must be installed on the input of the switching regulator. The regulation characteristics are obtained for different values of the ratio of the battery voltage and the power source. The conditions under which the maximum possible power is transmitted from the source of electrical energy to the battery are determined. It is shown that under certain conditions, the battery charging current may exceed the short circuit current of the source of electrical energy. The conditions under which a discontinuous current mode occurs in the inductance of the regulator are determined. Taking into account the possibility of such regime, the adjustment of the obtained regulation characteristics was carried out. The regulation characteristics are based on the need to limit the loss of electrical energy in the battery. For this, the maximum permissible value of the relative internal resistance of the battery was determined. If it is necessary to limit energy losses in the power supply, the type of the obtained regulation characteristics remains unchanged. However, in this case, it will be necessary to use a limited portion of these characteristics. It was concluded that when a pulse regulator is operating on a battery, to determine its regulating characteristic, it is necessary to take into account the internal resistance of the power supply. Without taking this resistance into account, the regulating characteristic of the switching regulator are uncertain.

Design of Optimal QFT Controller and Prefilter for Buck Converter Using Metaheuristic Algorithms

A buck converter is a step-down switching regulator. Buck convertors are being widely used in industrial applications that rely on regulated output voltage under fluctuating input voltage. A buck convertor works in the following modes: (a) current-controlled or (b) voltage-controlled mode. But these convertors manifest several nonlinearites because of the switching operation. Hence, in order to generate a quality output of the convertor, the design of a controller becomes crucial. In this paper, the synthesis of a QFT-based robust controller and prefilter has been carried out for an uncertain buck converter with varying input voltage and varying load. The controller synthesis problem has been posed as an optimization problem, and metaheuristic algorithms have been used for obtaining the optimal gains for the QFT controller and prefilter. By doing this, the QFT synthesis can be carried out in a single step instead of following the sequential classical QFT process on Nichols charts and the need for the generation of templates and bounds has be eliminated. The designed 2-degree-of-freedom QFT control system offers a robust behavior and efficiently handles the parametric uncertainties. The robustness of the designed controller has been confirmed through simulation results for large input voltage and load fluctuations.