Power
Cool solutions for high density applications
AC/DC brick power supplies are a well-established and proven format, but which form factor is optimally suited to particular use cases? John Stone, Relec Electronics’ marketing director, discusses the choices available
Figure 1: Comparison of power brick standard sizes.
W
hile we look at AC/ DC power supplies on the market, the most commonly seen forms are open-frame, case
enclosure (with fan) or adapter types. Today, due to the increased demand for higher power density coupled with a drive for ever-smaller end products, brick power supplies have been introduced to the AC/ DC category.
Most AC/DC power supplies on the market today rely on some form of convection cooling. This can be either through natural means (for example, plugtop / adapter and desktop types) or through forced air (via a fan).
Origin and size definition The standard size of brick type power was announced by the Distributed-Power Open Standard Alliance (DOSA) around 2010. The Alliance defined a standard footprint size in order to make it easier for design engineers to source power supplies for their designs on the market.
Sizes range from full brick (4.6 x 2.4” / 116 x 61mm) to the smallest, 1/32 size which measures 0.75 x 0.9” (19 x 23.35mm).
From DC/DC to AC/DC
Most of the early brick power supplies were DC/DC converters between 50 to 100 Watts. They were utilised in distributed power
48 February 2023
Figure 3: Block diagram of Cincon’s PDF700 AC/DC brick module.
Components in Electronics
www.cieonline.co.uk
architectures (DPA) from 48V to 12V and 12V to lower voltage (e.g. 5V or 3.3V). As new component technologies and advanced planar transformers developed, the higher wattage could be squeezed into a smaller package, increasing the power density of each module. Initially, most power boards were designed with the bridge filter or power factor correction (PFC) discrete circuitry at the front end and connected with a DC/DC converter for the required voltage output.
When the AC/DC power brick was introduced, it reduced the number of components required on the board, therefore reducing design complexity. It means that system engineers only need to add the key components, such as fuse, EMI filter, electrolytic capacitors on to the system board with the AC/DC brick according to the technical guideline. (See Figure 2). This layout is simpler and saves more time when compared to building the entire front end circuitry on the power board.
Advantages of AC/DC power brick Using an AC/DC brick provides benefits in terms of size – it is compact – as well as offering a lower profile and reduced heat dissipation.
Compared to other types of AC/DC power supply, a brick offers a compact size and lower profile. In addition, the encapsulated package provides the protection for internal electronic components from outer dust or humidity. The glue inside the brick helps the brick power dissipate heat evenly from the
Figure 2: AC/DC power block diagram, showing related components required in a typical power supply.
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