Tool/software: WEBENCH® Design Tools
Today, WEBENCH Power Designer can help you design for positive input voltage conditions with topologies ranging from non-isolated buck, boost, and buck-boost, all the way through isolated topologies such as flyback, half-bridge LLC, and others.
Power Designer does not currently support negative input voltage designs, but here are some resources on designing such supplies:
- Negative LDOs can convert a negative DC input voltage to a higher, less negative output voltage, for example -17V input to -12V output, but are only suitable for lower output current designs. You can see TI’s negative LDO offerings here.
- For higher efficiency and output current designs, a variety of buck, boost, and flyback regulator ICs can be used in negative input voltage designs with some modifications. The following app notes and articles discuss this in detail:
- Here is an article that shows converting Negative input voltage to output voltage that is higher, Negative Input to Positive Output made SIMPLE - http://www.ti.com/lit/an/snva740/snva740.pdf
- Here is another article that shows converting negative input voltage to output voltage that is lower than the input, Practical implementation of negative-input, negative-output step-down switching converters - https://www.eetimes.com/document.asp?doc_id=1272382
How often do you design power supplies with negative input voltage? We'd love to hear your inputs on this topic.