I'm designing a photodetector for moderate-quantity production (probably
1000-5000 units over its lifetime).It needs a few power supply voltages inside, like
+3.6 for the micro, < 50 mA +- 15V for the analogue stuff +50-75V for the photodiode bias.It only dissipates a few watts total, mostly from +-15.
Total BOM cost including box and board, excluding supplies, is about $220 at most. DC-DC converter modules are expensive enough that they'll add another $100 to this, which stinks.
Sooo, it looks like I can build my own DC-DC with several outputs, and post-regulate them. Not awful, but will need a custom transformer.
However, it occurs to me that I could very easily use a 12-14 VAC wall wart, and do it the old-school way with a couple of half-wave regulators and a Cockcroft-Walton tripler for pretty cheap--mostly the cost of the caps, which should be under $10 altogether in 100s.
One drawback is needing different wall warts for different markets, but that isn't a terrible problem in this instance.
Alternatively, I could use a +18V wall wart, one inverting switcher, and a charge pump / Cockroft Walton.
Suggestions? Pitfalls? Input protection advice?
Cheers
Phil Hobbs