Tool/software: WEBENCH® Design Tools
We are pleased to announce addition of improved capacitor derating feature in WEBENCH® designs.
What is Capacitor derating?
Capacitor derating is reduction in the effective value of capacitance primarily due to DC voltage applied across the capacitor. For example, a 10uF ceramic capacitor which has a nominal capacitance of 10uF at 0V across its terminals could have 5uF (50% derated value) when a certain voltage is applied.
How does WEBENCH implement capacitor derating?
The primitive ceramic capacitor model implemented in WEBENCH used a generic derating curve to estimate the derated capacitance value for all ceramic capacitors. Now, the improved algorithm calculates the derated value using capacitor vs voltage information from manufacturer data when available. For cases where we do not have this data, we use a conservative linear approximation.
How will this impact my new WEBENCH designs?
A better estimation of this derated value will help you with more realistic estimates of performance of the power supply such as voltage ripple, stability parameters and more.
The new designs that you create in the WEBENCH Power Designer tool are already equipped with this feature. For any new designs being created, the derated value will be used for operating value calculations like bode plot, voltage ripple, etc. and other WEBENCH Power Designer features like electrical simulation and compensation designer.
You can view the total derated capacitor value for capacitors under BOM -> Select Alternate Part -> Total Derated Capacitor (After enabling Show All Columns checkbox)
How do I update my existing designs with this feature?
For existing designs, if you would like to have WEBENCH Power Designer redesign using the improved capacitor derating algorithm, please follow the following instructions below:
1. Go to the WEBENCH panel on the TI home (www.ti.com) page and click Start Design on the WEBENCH Power Designer panel. Once WEBENCH Power Designer loads, click "My Designs/Projects" in the top left corner.
2. Make a copy of the design if you like to preserve the existing design. We like to caution you that updating the existing design will overwrite any changes that you have made. So, it is a good idea to make a copy of the design before updating it.
3. To copy the design, you can click on "Copy Design" button located near lower left corner from within the design summary page. You can also click on "My Designs/Projects" button on top left corner and click "Copy Design" button under the "Action" menu for the design of your choice.
4. To open up a specific design or project, click "Open Design" located under the "Action" column on the right side of the page.
5. To update the design with the derating algorithm click on "Update" button under the "Advanced Options" menu or you can click "Change Design Inputs" and click "Submit". If "Advanced Options" menu is not available, click "Submit"
If you have any questions, feel free to let us know by submitting your questions here on e2e.
The WEBENCH® Development Team