Switching Regulators Features in the Matching Mode Operation

Abstract

Currently, various types of non-traditional and renewable sources of electrical energy are widely used. If the energy carrier of such sources is free, in the process of operation it is advisable to select the maximum possible power from them, regardless of the fact that the utilization factor of the source's electrical energy in this case may be relatively low. To obtain the maximum amount of electrical energy from the source, two conditions must be met: 1) the source must be brought to the maximum power point (МPP); 2) energy from the source must be taken continuously. As you know, to bring the source into the MPP, it is necessary that the load resistance be equal to the output resistance of the source. Otherwise, the power will be taken from the source, which is less than the maximum possible. Therefore, in cases where the load resistance differs from the output resistance of the source, a matching switching regulator is turned on between the source and the load to match the output resistance of the source with the load resistance. In this case, the input impedance of the switching regulator will be the load of the source. This resistance depends on the load resistance of the regulator, as well as on the relative time of the closed (open) state of the controlled switch S of the regulator t*. Thus, by adjusting the parameter t*, it is possible to ensure the fulfillment of the condition for removing the source into the MPP at various values of the load resistance. In this case, the maximum possible power of the source will be transferred to the load, regardless of the value of its resistance. The dependence of the output parameters of the switching regulator on the parameter t* describe its regulation characteristics. Since, when operating in the maximum power transmission mode, the internal resistance of the source and the load resistance are of the same order of magnitude, when determining the regulating characteristics of the regulator, the internal resistance of the source must be taken into account. The aim of the work is to analyze the control characteristics of the regulator, which operates in the mode of transferring maximum power from the source of electrical energy to the load, as well as to determine the conditions under which it is possible and advisable to operate in this mode. These issues were analyzed using the example of the two most common switching regulator circuits - step-down and step-up regulators. It is shown in the work that, in contrast to the up-type switching regulator, in the down-type regulator, the energy from the power source is taken in discrete portions. Therefore, it can ensure the selection of maximum power from the source only in the t* = 1 mode at a certain value of the load resistance. To ensure continuous extraction of energy from the source, at the input of the switching regulator of the step-down type, it is necessary to install a capacitance of sufficient value. In this case, the circuit can provide maximum power transfer from the source at different load resistances. The paper presents the adjusting characteristics of the analyzed circuits for the case of their operation in the mode of transferring maximum power from the power source to the load, which makes it possible to determine the parameter t* at which the power source is output to the MPP. It is shown that each of the considered circuits can provide the output of the power supply to the MPP only in a certain range of variation of the load resistance of the regulator. For each regulator, an appropriate range of variation of the t* parameter is indicated, depending on whether the power source is a voltage source or a current source.