Idea: MEMS electromechanical boost DC DC converter - works from very low voltage - Page 1
Forum section: electronics / general

author: daqq
author_rank: Super Contributor
timestamp: May 28, 2021, 07:49:21 pm
content: Hi,Thought experiment:I've been looking into DC DC converters that can start up from a low voltage. There's not that many of them and the lowest I've seen is able to start from 13mV (https://www.mdpi.com/1996-1073/13/20/5501/pdf). Now that's impressive as hell, but I was thinking if it would be possible to achieve an even lower startup voltage using a MEMS solution to provide the initial kick.Say you had a MEMS version of a conductive bimetalic strip that would act as a thermal cutoff switch - above a certain temperature it would disconnect, below it it would stay connected. This would be connected in series with a transformer (or inductor - boost topology type thingie). "Schematic" included. Once voltage is applied to the device, the switch starts to heat up - 1mV might not seem like a lot, but at microscopic scales it should be able to heat a very small volume by a LOT.Once the MEMS switch disconnects, the transformer or an inductor will get a current change and a jolt of much higher voltage will appear on the secondary, allowing the DC DC converter to start.Because this is a "mechanical" solution, it doesn't have to deal with low voltage semiconductor physics at all, so if you can create a MEMS thermal cutoff switch that disconnects itself when you apply 1mV to it, you can get a converter that starts at 1mV.Now obviously there's a lot of drawbacks, but MEMS relays exist, as do all sorts of weird and wonderful structures. So...Do you think it would work? It's just a thought experiment.

author: daqq
author_rank: Super Contributor
timestamp: May 28, 2021, 07:52:12 pm
content: Without transformer.

author: Kleinstein
author_rank: Super Contributor
timestamp: May 28, 2021, 08:49:54 pm
content: The mems relais are more like very high performance / low leakage switches, not high power. Not sure the contact rating is that great and there may be some wear from very frequent switching.At small scale transformers / inductors get worse and would need increasing freququency.

author: daqq
author_rank: Super Contributor
timestamp: May 28, 2021, 08:52:45 pm
content: Kleinstein: Thanks for the feedback. But there would only have to be a few switchings really - just to start up the converter, say, 10 per startup? Afterwards the whole MEMS block gets disconnected through the bottom bit - say a depletion mode MOSFET.And the power would not need to be high. And none of the other parts need to be MEMS at all.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 28, 2021, 09:34:34 pm
content: You may be better off looking at JFETs or DMOS. The trick is to set up a zero-bias  amplifier, with adequate transconductance to overcome load resistance and start oscillating.The available power is still extraordinarily small, at best usable to bootstrap a conventional converter, which again will still only deliver tiny outputs (fractional watt).Seebeck modules are made of numerous junctions for a reason; I'd recommend sticking with that, rather than trying to force-fit single junctions or something like that.Tim

author: amyk
author_rank: Super Contributor
timestamp: May 30, 2021, 02:19:19 am
content: I think you'd need a lot of current at that low of a voltage to get any sort of decent power output.