Ultra low power design
I am looking at a 60Hz 110V power supply desing that can provide about 0.025W (25mW) of power.
Normally you wouldn't do this with a switch mode power supply, but the absolute value of the input current can not exceed 0.4mA and the design has to be extremely small (about 20x15x10 mm).
I can't think of a different way of doing this. Does anybody know if it is possible to design a SMPS that small and/or if something like this already exists. ?
Comments
It is a non-isolated design.
Based on the spec it looks like the LNK302 would get me the closest.
I noticed that you have a design kit for the LNK304 ( RDK-138)
Where/how can I order this design kit ?
Other question, is your company working on an even more power efficient design ?
Thanks,
Robert Hulshof
Robert -
If you can give your input/output specs, I'd be happy to put a preliminary design together using our PI Expert software.
You can purchase our RDK's from our website. Here is the link:
http://www.powerint.com/en/buy-reference-design-kits#1844
RDK-138 might be a bit overkill for your design. If you have the ability to cut prototype PCB's in-hous, I would reccomend that route. Most circuit designs and PCB layouts with LinkSwitch-TN are very simple and straightforward.
In regards to your efficiency question: We're always pushing the limits of what we can do for power supply efficiency. One of the very first ideas used in the TopSwitch product line revolved around our specific MOSFET technology and then in later version, our light-load variable switching frequency features. Efficiency is always a big push for our customers, as is component count, cost, ease of design, etc. With some of our newer high-power products (the Hiper Family), we have reference designs that easily hit 97%+ efficiency all while at very high power levels.
-The Traveler
Traveler-
We can protype PCBs, so thanks for the preliminary design offer,
The Input requirements are:
Maximum current = 0.5mA (500uA) at 110V AC and 0.3mA at 220V AC
The output requirement are:
Output voltage: 3V
Output current: The goal is 10mA or more, but the minimum that the current software can handle is about 6-8mA, but this will already restrict what we can do.
Startup Time: Not specified yet but could be several seconds.
Regarding the dimension: We are still in prototype phase. My goal is to have a power supply that is 33x20x10 mm or smaller which gives us some room for ESD protection.
Robert
Robert -
From a power level standpoint, I think LinkSwitch-TN should fairly easily meet your requirements. With SMT components, the D package IC and careful layout, you might be able to squeeze everything into the space you need.
The tough part is going to be the peak input current requirements you have. At least it seems like they are peak input current values. If they're RMS input current values this will be easier to deal with.
The problem you're going to run into if your current limits are peak values will be that during the conduction time of the bridge rectifier, you can easily have a large current spike. You can mitigate this somewhat with the use of differential mode inductors. This might be part of the design that just requires some experimentation.
-The Traveler
Traveler
The current values are RMS.
Regarding the current spikes I currently do not know what the exact limits are, but I know that the first capacitor after the rectifier can be at least 470p. I haven't simulated it, but my guess is that, that would be close to what is needed in this design.
Robert
This is going to be a difficult project. You might try our LinkSwitch-TN product line if you can use a non-isolated design. If you need an isolated design I think you are going to run into some serious space constraints.
-The Traveler