Easy Guide to Switch Mode Power Supply Designs

April 15, 2021 , in Blog

One of the most basic functions of any electrical or electronic circuit is it's power supply. The ability to provide the appropriate voltage and current to your design is fundamental to its successful operation. And it is not uncommon for a single board to accommodate several different voltage levels. For example, digital circuits use 5V; however, other devices may vary significantly with supply levels that include 1.2V, 3V, 10V, 12V and 15V. Linear and switch mode power supplies provide the conversion and control necessary to drive these types of loads for PCBAs and other electronic systems; and of the two power supply designs, switch mode power supplies provide distinct advantages.

Different types of power supply switches

Various PCBA power supply switches

Switch Mode Power Supplies: Operation and Applications

Similar to linear power supplies, various types of semiconductors may be used, including diodes and transistors. However, switch mode power supplies (SMPSs) utilize these devices for switching. Output control is achieved using PWM, and these supplies are drivers for a number of applications that include the following:

Example Applications for Switch Mode Power Supplies

  • Computers
  • Mobile phone chargers
  • Telecommunications devices
  • Arc welding equipment
  • Medical test equipment

As this list illustrates, SMPSs are employed where precision is required. Not surprisingly, there are also a number of different SMPS designs, as shown in the figure below.

Types of switch mode power supplies

Different Switch Mode Power Supply design topologies

Although not exhaustive, the list above does identify the range of design options available for SMPSs, along with support circuitry that plays an important part in creating the best design for your project.

 

Optimizing the Design of a Switch Mode Power Supply

As shown above, SMPS designs may be somewhat complex depending upon your application and load requirements. Therefore, sound power supply design principles should be employed.

Guidelines for Switch Mode Power Supply Design

  • Take advantage of smaller components wherever possible

Typically, SMPS designs can utilize smaller components than linear power supplies. Designers should leverage this characteristic to the greatest extent possible while adhering to all creepage and clearance standards and DFM requirements.

  • Apply good filtering technology

A power supply’s basic function is to meet the demands for all connected loads. To do so, adequate filtering is necessary. Any variances, such as ripple, may affect the operation of the connected circuitry.

  • Ensure good thermal distribution and dissipation

Power supplies can be notorious for creating hot spots and thermal imbalance on circuit boards. Therefore, analyzing thermal behavior should be a priority. In the course of thermally analyzing your board, all necessary design modifications to improve thermal dissipation and distribution should be enacted.

  • Select appropriate materials

For the best designs, you should always evaluate your choice of material and not simply accept the software default.

  • Choose an adequate copper thickness

An important consideration that, if neglected, can lead to arcing and/or board damage, is copper thickness. Adequate ampacity is mandatory for power supply designs.

  • Perform circuit analysis simulation

It is also a good idea to simulate your board’s operation and ensure that your power distribution network (PDN) is adequately supplied.

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Switch mode power supplies are essential elements for many PCBA designs. However, it is important that good guidelines are employed to make the best use of SMPSs and protect other components and interconnected boards or other electronics. At Tempo Automation, the industry’s leading PCBA prototype and low-volume production turnkey manufacturer, we will partner with you to provide expert collaboration and support to help you create the best design.

And to help you get started on the best path, we furnish information for your DFM checks and enable you to easily view and download DRC files. If you’re an Altium Designer or Cadence Allegro user, you can simply add these files to your PCB design software. For Mentor Pads or other design packages, we furnish DRC information in other CAD formats and Excel.

If you are ready to have your design manufactured, try our quote tool to upload your CAD and BOM files. If you want more information on switch mode power supply design for manufacturability, contact us.

1Image from  Würth Elektronik at https://www.we-online.com/web/en/electronic_components/news_pbs/blog_pbcm/blog_detail-worldofelectronics_45887.php.

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