FEATURE
POWER
TOOLS: THE FIRST STEP IN PO Tools for designing a power supply architecture are not widely
used compared to computational and simulation tools. Nevertheless, such tools play a crucial role during the development process of a
power supply system for an electrical circuit. Serving as an initial step in the power supply development process, these tools lay the foundation for creating an optimal power supply architecture. Frederik Dostal, power management expert, Analog Devices, comments
T
here are various tools available for developing a power supply, and this eases the burden of tedious work for
the developer. One of these tools is LTspice, a well-known simulation tool from Analog Devices. Used to simulate a power conversion circuit, this enables the simulation of different voltage and current waveforms to refine the circuit design and tailor it more closely to specific requirements. Calculation tools like LTpowerCAD are
also available. Unlike LTspice, LTpowerCAD is designed for calculations rather than simulations. It takes into account various specifications such as the input voltage range, the output voltage, the load current, the voltage ripple at the output, and much more, to compute and optimise the circuit. A suitable power converter IC is selected and external passive
components are suggested. Thus, a tool like LTpowerCAD is the precursor to circuit simulation with LTspice. Another critical aspect in power supply
development is defining the power supply architecture or creating a power tree. Such a complete power supply of a system usually requires more than just one power converter. Several different voltages are often required. There are different ways to do this. The differences between the architectures can be calculated and represented excellently with a power supply architecture tool such as the LTpowerPlanner from ADI. Figure 1 below shows the interface of
LTpowerPlanner with the representation of a power supply architecture using a 24V input. From this, various supply voltages and currents are generated. The different blocks can be easily
added and linked with connecting lines. Clicking on one of these blocks defines the efficiency of the respective power conversion. Once these entries have been made, the LTpowerPlanner can perform an overall calculation of the complete power conversion architecture. The architecture in Figure 1 has an overall efficiency of 91.6%. An architecture tool such as LTpowerPlanner
allows the user to compare different power conversion architectures. Figure 2 shows a solution for the same specifications as Figure 1, but with a different structure. This second solution can now be compared to the first solution. Here, a linear regulator (LDO) was used to generate the 1.2V rail from the 2.8V rail. Such a solution with a linear regulator is more cost-effective than Converter 4 in Figure 1. Another change of the solution in Figure 2 is to generate the 3.3V voltage not directly from 24V
Figure 1. A power supply architecture created with LTpowerPlanner 44 DESIGN SOLUTIONS DECEMBER/JANUARY 2025
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