Buyers’ guide to optimum DC/DC converter choice

Powerstax CEO, Tim Worley, suggest 10 questions worth asking to avoid the you never know approach to over specifying DC/DC converters Q: What do you want to convert?
A: How wide an input range does your DC/DC converter have to operate over? The tighter you can specify the range, the better. A 4:1 input range (say 12 to 48V) is less efficient than a 2:1 range (24 to 48V). Similarly, over-specifying output voltage or current quickly increases converter cost. Also, a good understanding of the actual load is required to ensure that voltage regulation is appropriate, as specifying tight regulation adds cost and complexity.

Q: What is the supply voltage quality?
A: Take a realistic view of how electrically clean and reliable the input voltage source is. The smaller you can make the input filter and avoiding the need for battery back-up will reduce weight and cost.

Q: How much space is available?
A: Be sure you consider the power source early in the overall system design. Leave insufficient space and you will limit choice and inevitably push up the final cost.

Q: How efficient must the converter be?
A: Efficiency costs money. Think about system losses and ensure you have considered how much (or how little) efficiency you can live with.

Q: How to get rid of the heat?
A: Heat kills electronic components and all power conversion processes generate heat. DC:DC converter location should be a prime consideration. Can it be cold face mounted for efficient convection cooling or is fan blown cooling (internal or external) to be used? It is vital to remove heat from where it is generated and reduce the heating effect on surrounding components.

Q: What connection methods are required?
A: A large number of connection techniques is available and a mix of methods may be required. Size, access, environment and reliability must be considered when choosing connections. Most commonly PCB mounting is employed for DC/DC converters but in some applications fast-on connectors or screw connections may be required.

Q: Isolated or non-isolated?
A: Does this part of the system require a safety isolated conversion or is this achieved elsewhere? Isolated converters cost more and offer reduced efficiency.

Q: What is the end products application environment?
A: Think about the environment the end product will be used in. Will it be vehicle mounted, subject to vibration, moisture or humidity, extremes of temperature etc. Correct specification of environmental requirements allow processes such as conformal coatings, vibration protection, IP rated enclosures to be designed-in and avoid unnecessary field failures.

Q: What is the end products projected life?
A: If a three-year life with no repair cycle is all that is needed its a different product to one requiring a 10-year life with 20-year support. Design and sourcing must be fit for purpose whether it be a commercial or COTS/MIL product.

Q: What colour do you want?
A: Yellow of course! If you must have another colour or special features Powerstax can help because it owns the tooling. How important is dealing direct with a designer of DC/DC converters and being assured of ownership of IP and long term supply.