Globally, there is such an array of potential input voltages that this benefit is nice to have. But it may restrict the sale of a system to countries where low-line ac input is predominant, or at least encountered on a regular basis.
Power supplies specifically groomed with high peak capabilities in mind use an overall design and architecture, OCP circuitry, energy storage characteristics, efficiency, and thermal robustness that will support high peak loads. Such units may be able to deliver up to twice their nominal power for 10 s, which is a realistic application requirement. Furthermore, this capability may extend to duty cycles that range from 35% to 50%.
One approach along these lines is to use a power supply that provides dc-output modularity. A modular design enables the user to specify several standard outputs alongside one that provides the necessary high peak current capability. In other words, you aren’t likely to need a high peak capability on every output, so look for a power system that avoids the need to pay for that (Fig. 2).
WORKING OUT THE NUMBERS Important factors to determine when selecting a power supply for a high peak application include how much power can be drawn during the non-peak duration, how much peak power can be provided, and how long the peak power can be drawn. The answers to these questions are constrained by the rated specification of the power supply.
For example, the specification of a 400-W power supply that can provide 800 W of peak power for up to 10 s at a 35% duty cycle defines the operating envelope within which your requirements must fall. Using these specifications, you can determine that the available power during the non-peak duration will be approximately 180 W. If you know your application won’t require more than 720 W at peak and for 5 s or less and the duty cycle is 25%, then you can draw about 290 W during the nonpeak duration.
Once you’re satisfied that your design requirement does not exceed the power supply’s rated specification, the systemlevel questions arise. For instance, you may need to establish how much power can be drawn during the non-peak duration if the peak is less than the power supply’s peak rating or what duty cycle can be achieved if the peak power is drawn for less than the power supply’s rated duration. The math is not complex, but you do need to account for all these system level issues to ensure trouble-free power-supply operation.
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