| Electronics > Beginners |
| Generating 3 voltage rails, will this work ? |
| (1/5) > >> |
| BravoV:
The +15V and -15V rails are classic topology, linearly regulated to power the analog section, while the +5V rail uses an isolated DC to DC step-down switching converter to power logic parts. Will this work ? Other considerations if any ? Thanks in advance. |
| Ian.M:
It will work, but a fully regulated isolated DC-DC converter is more expensive than a simple switching (non-isolated buck) regulator run off the unregulated +V rail. If you need a *LOT* of current from the +5V rail, you may have to go with the isolated DC-DC converter to utilise the whole secondary, but as high current isolated DC-DC converters are expensive, its probably more cost-effective to simply up the mains transformer VA rating and use a simple switching regulator. |
| CJay:
I've just done pretty much exactly that to remove the need for a custom mains transformer. Using a centre tapped mains transformer to feed 7915 and 7815 regulators and 'stealing' some power from the positive rectifier to feed a buck converter (no need for isolation in my application) for a 5V rail. |
| Benta:
I've done it the "other way round". A 5 V wall-wart to power the logic, and an isolated 5 V in, +/-15 V out DC-DC module. |
| BravoV:
--- Quote from: Ian.M on June 29, 2018, 09:33:29 am ---It will work, but a fully regulated isolated DC-DC converter is more expensive than a simple switching (non-isolated buck) regulator run off the unregulated +V rail. If you need a *LOT* of current from the +5V rail, you may have to go with the isolated DC-DC converter to utilise the whole secondary, but as high current isolated DC-DC converters are expensive, its probably more cost-effective to simply up the mains transformer VA rating and use a simple switching regulator. --- End quote --- Thanks for the confirmation. :-+ Yeah, the +5V rail needs about 4 to 5 Amps while the pos & neg 15V rails only merely at sub 100mA. My situation is I already have a suitable transformer with the right size, its just its only has 3 taps includes the CT. Also coincidentally at local here there is a really cheap offering for a NOS Vicor high density DC to DC module that I think suitable for +5Volt rail. Yeah, buying a new one of this isolated DC to DC is very expensive. |
| Navigation |
| Message Index |
| Next page |