Power Switching Converters with very low power consumption and high efficiency for energy savings

Abstract

The objective of this research is the analysis of power switching converters with targets of very low power consumption and high efficiency for being used in new system for energy savings. Typically, they are implemented as Switching Mode Power Supply (SMPS) modules in different type of applications in both consumer and energy businesses . In particular have been considered power supply systems with output power in the class of low and medium power, in the range from few watts up to hundreds watts. Referring to consumer business, the main fields of application are lighting and home appliances where in the last years the international Agencies and Governments have been focused their attention to ask for reducing the continuous energy waste. Therefore, more restricted and challenging constraints have been fixed in order to reduce the energy waste and to improve the level of performances of new products, that pushed the introduction of new technologies and new design solutions. In particular in the lighting applications the improvement in LED technologies is leading to the development of LED lamps with higher light efficiency and lower power consumption. The analysis will start making a overview of the principal topologies of switching converters used to drive the LED bulbs. Advantages and disadvantages will be shown for each topology. Then the flyback topology will be analyzed and discussed in more details, since it is considered the most promising one. Finally, an alternative schematic will be proposed in order to increase the electrical performance of the whole power conversion system. On the other side in the home appliance applications there are conditions where the energy is consumed by the device when this does not work or does not perform its main functions and that happens without the final user realizing it. One condition is when the device is put in standby status. For this case the analysis of the commonly used techniques for reducing power consumption in the switching converter is discussed and a new technique for reducing power during the inactivity state of the appliance system is proposed. The proposed solution works on the feedback network, introducing a perturbation on the feedback signal: in this way the main power transistor, in the converter, is switched off and the output voltage of the converter is settled to zero. This solution allows an important reduction of the effective power consumption of the system. In order to confirm this solution an auxiliary SMPS with output power of 5 W to supply the user interface of a washing machine has been designed, and the converter topology used is a Flyback converter, compliant with the current regulations of the home appliance applications. In addition a prototype is realized and then simulations in PSpice, thermal and electrical measurements are performed in order to verify the operations of the converter in different environmental and electrical conditions. Looking at the business of energy conversion, in the design of applications of high power systems an important issue is to provide low voltages, in the range of tens of Volt, tapping from high voltage input line, which is usually in the range between hundreds of Volt to kilovolt, by means of switching power supplies. Low voltages are needed to supply the logic control circuits and the power semiconductors driving the applications. The supply system has to deal, consequently, with both wide input voltage range and electrical insulation. The evaluation of the operative conditions of a driving system for IGCT devices, used in a transmission system application with wide input voltage range, is described. The design of a 100 W supply converter is shown considering all the issues related with the series connection of power devices and the needs of insulation. Converter design, modelling and experimental results are shown together with the evaluation of the efficiency of the proposed solution.