I am using the RDR239 reference design and need to extend the temperature operation to -37 degC- +74 degC. Would this reference design work to supply 150W for that range? If not what do you suggest?
Thank you for the question.
RDR239 is about how to design with LCS controllers for 24V middle range power in a temperature range from 0 to 40 deg. C. There is 10 deg. C. margin added during calculations with the PIXLS.
Going for higher temperature range means accommodating two main concerns - safety and components operational temperature margin to the maximum.
- Safety will include reconsider the temperature classes of the insulation materials if needed.
- To secure a temperature margin for components may require:
o Some better components selection with less temperature effect over the characteristics,
o Improve the heat-sinking or provide new (if currently not used),
o Providing airflow,
o Components re-positioning for reducing heat exposure from radiation and conduction etc.
As a first step you can run the PIXLS design spreadsheet with the new temperature design constrain. There are places in the spreadsheet were temperature is taken in to account and user’s input real measurements could be used to improve the results. ! It is better to take more accurate temperature measurements from your actual unit before consider all of the options.
Having for each component the expected max temperature,
Texpected_at_74 = T_measured_at ambient + 74 – Tambient
and the datasheet in hand the best strategy (from the listed above) for providing a temperature margin needs to be evaluated.
Eventually, when all components operational temperature is in the specified limits delivering the power is not a concern.
With the required big temperature range the rate of change has to be consider as well because of possible condensation moisture.