Other Parts Discussed in Thread: LM5574
I need to design a PSU that has several output rails generated from a single 40V unregulated DC input. The output voltages are +/-19V (0.2A each) and +48V (0.01A). I need all rails to switch in sync for minimizing comb frequencies and ease filtering of the supplies (which have to be very quiet). All rails should operate in CCM. It would be very convenient if switchers can be daisy-chained for sync operation.
For +/-19V rails I've found the LM5574 to be suitable. The +19V rail design is pretty straightforward and Webench does a good job with it. The -19V rail is problematic, because Webench generates values that result in DCM operation. I tried changing inductor value, but it looks like Webench can't do that.
Here're the questions I'd like to get answers to:
1. How do I calculate inductor value for inverting buck-boost circuit that will operate in CCM?
2. Should the switchers on all rails switch together or should I employ interleaving? If interleaving is substantially quieter, what are suggested part and circuits?
3. Is there any boost converter that can be synced the same way as LM5574 and that I can use together with LM5574 in my application?
Thanks!
