Paul,
Thank you for your interest in TI parts. We do have a controller that can meet your needs, and it is the LM25118 buck-boost controller (http://www.ti.com/product/lm25118).
There was no mention of a need for isolation, so I have assumed you don't need it. However, since your stated input voltage can be less than or greater than your output voltage, you will need a topology that can meet such requirements, like this buck-boost. This controller will operate as a boost when Vin<Vout, and it will transition to a Buck when Vin>Vout.
Please visit the link above to access the datasheet for the device, and to start designing with the WebBench tool in which you can enter your design requirements. This tool will help you determine some parameters like an optimum Fsw.
If isolation is required, then there are a number of other topologies available, at the expense of an additional isolating transformer. The specifications of the isolating transformer will depend on the chosen topology.
At 120W, you would be near the upper limit for a flyback. While a flyback would still work, the current stresses would start to be prohibitive. 120W would best be addressed with a forward converter if indeed you do need isolation.
Thank you.
MC.
Martin,
Thanks for your advice.
Having studied the data sheet and the webench results, I feel that the 120W requirement would be stretching this topology too near to its limits although the device would be useful for future applications.
I am looking at the possibility of a LM5030-based push-pull design using a planar transformer to achieve 90% efficiency and to have satisfactory EMC performance. To meet the low end input voltage requirement, I would run the device Vcc from a 8V regulator (also used elsewhere in the circuit) as otherwise it would not start up reliably. Is this a reasonable solution or is there a more suitable device? As for the transformer, Payton may be able to provide a suitable part. Are there any other transformer manufacturers that you would suggest?
Regards,
Paul
The LM5030 is a good choice if you want to use push-pull and a transformer. It will give you the freedom to extend the power range if required.
Since we don't design or provide magnetics, I can't steer you to any specific vendors.
Hello Martin,
I am trying to use the LM25118 controller for a school project. Following the datasheet of the product I was able to get most of the values for my components. However, It is not clear to me how to get the input and output capacitors, as well as the components for the error amplifier configuration. I also wanted to simulate the design in SPICE (this is the software i am most familiar with) but I could not find a model for it.
my specs for my project:
Vin = 11V - 16 V
Vout = 12V
Iout = 8A
Also, I just used WeBench for the first time to simulate, and I does the job but I would like to know where all the values came from.Thanks you.
~LR.
Hi Luis,
Thank you for your interest in TI parts. While I can't offer any experience with that particular device, I can give you some general information on designing general devices within a non-isolated Buck switcher.
I have attached a design example paper for a device I am familiar with, the TPS40422. This paper has not yet been released so use at your own risk. This device is not equivalent to the LM25118, but designing input caps, output inductors and output caps is pretty much the same process.
Also attached are two very helpful papers which should help with loop compensation design.
I hope this helps.
6837.DRAFT TPS40422 Design Example.pdf
2311.SEM300 1984 Appendix A Error Amp and Compensation Network Design.pdf
0066.SEM300 1984 Closing the FB loop.pdf