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How the Smart Hardware Engineer Can Easily Design Power Supplies: Mini Tutorial by Frederik Dostal ABSTRACT This mini tutorial gives an overview of the possibilities for power supply design. It will address the basic and commonly used isolated and nonisolated power supply topologies along with their advantages and disadvantages. We will also cover electromagnetic interference (EMI) and filtering considerations. This mini tutorial aims to provide a simplified under- standing and renewed appreciation for the art of power supply design. INTRODUCTION Most electronic systems require some sort of voltage conversion between the voltage of the energy supply and the voltage of the circuitry that needs to be powered. As batteries lose charge, the voltage will drop. Some DC-to-DC conversion can ensure that much more of the stored energy in the battery is used to power the circuitry. Also, for example, with a 110 V AC line, we cannot power a semiconductor such as a microcontroller directly. Since voltage con- verters, also named power supplies, are used in almost every electronic system, they have been optimized for different purposes over the years. Certainly, some of the usual targets for optimi- zation are solution size, conversion efficiency, EMI, and cost. THE SIMPLEST POWER SUPPLY: THE LDO One of the simplest forms of a power supply is the low dropout (LDO) regulator. LDOs are linear regulators as opposed to switching regulators. Lin- ear regulators put a tunable resistor between the input voltage and the output voltage, which means the output voltage is fixed independent of how the input voltage changes and which load current is running through the device. Figure 1 shows the basic principle of this simple voltage converter. For many years, a typical power converter con- sisted of a 50 Hz or 60 Hz transformer, con- nected to the power grid, with a certain windings ratio to generate a nonregulated output voltage, a few volts higher than the needed supply voltage in a system. Then, a linear regulator was used to Figure 1. A linear regulator converts one voltage into another. 4 FEBRUARY 2022 | www.eetimes.eu COVER STORY