Improving the standard of living requires ever-increasing demand for energy, particularly in electrical forms. People do not use directly electrical energy, but mainly IT and telecommunication equipment, transportation vehicles, white goods, light, mechanical work or media: these are all the tangible effects of the electrical energy.
Power electronics is the science studying the ways to convert electrical energy into the forms typically used in the daily life. A modern power conversion system consists of an energy source, an electrical load, a power electronic circuit, and control functions: the control circuits take information from source and load, determining how the switches must operate to achieve the desired conversion.
This is exactly the principle of operation of the SMPS (Switch Mode Power Supply), which uses a high frequency switch (in practice a transistor) with varying duty cycle to maintain regulated output voltage.
An AC/DC SMPS is a system consisting of three main stages, as shown in figure 1 in the case of a typical IT server application.
Fig. 1: An AC/DC SMPS system consisting of three main stage.
In each of these 3 stages the role of power or logic components based on semiconductors is fundamental: high voltage power MOSFETs, diode and controllers in the PFC and PWM/resonant stages, Low Voltage power MOSFETs or diodes in the rectification stage.
More recently the focus has been moving from a ‘‘device-driven’’ to an ‘‘applications-driven’’ scenario, in a “system engineering” approach. This transition has been mainly triggered by the fact that advanced semiconductors with suitable power ratings already exist for almost every application of wide interest, so designers show an increasing interest in a more flexible, reliable and of course efficient way to use them.
According to the new “system” approach, efficiency and power density are definitely more and more in the focus of SMPS design, especially in IT computing applications. Figure 2 shows the most popular efficiency standard followed