Has anyone used a SR086 Inductorless Switching Regulator

[dansku]

Has anyone used a SR086 Inductorless Switching Regulator?

I just got myself a DC-DC Buck converter (http://www.ebay.com/itm/231381389930?_trksid=p2060778.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT). I was researching on some AC-DC converters to use with it and ended up looking at the SR086 Inductorless Switching Regulator (Datasheet: http://www.mouser.com/ds/2/391/SR086-30993.pdf).

I would like to know if anyone knows anything about this chip, if it works well, as it's so simple to use and has no transformer.
With this SR086 and a  LM2596 you can make a AC-DC variable power supply.

Thank you

[dansku]

Found this picture online, does it look too simple to be true? 

[ConnorGames]

Unless you really know what you are doing, it is dangerous to use a non-isolated supply like this. At the very least, they make testing whatever they are powering a nightmare, and any externally accessible electrical connections from the power supply or equipment it is powering would need to be isolated. I would strongly recommend using an off the shelf plugpack, they are cheap, safe, and readily available.

[T3sl4co1l]

They work by running at very low power factor -- probably worse than the old standby of a series dropping capacitor.  As a result, they aren't scalable, only reasonable for very small loads like night lights, monitoring/home automation stuff (PIR, X10, etc.).

Definitely not like bench supply material, or phone charging (needs isolation), or even lighting LEDs (needs too much power).

Tim

[coppice]

They work by running at very low power factor -- probably worse than the old standby of a series dropping capacitor.  As a result, they aren't scalable, only reasonable for very small loads like night lights, monitoring/home automation stuff (PIR, X10, etc.).

Definitely not like bench supply material, or phone charging (needs isolation), or even lighting LEDs (needs too much power).

Tim

They are fine for the little MCU in a typical white goods application, which I think is the main market.

[coppice]

They work by running at very low power factor -- probably worse than the old standby of a series dropping capacitor.  As a result, they aren't scalable, only reasonable for very small loads like night lights, monitoring/home automation stuff (PIR, X10, etc.).

Definitely not like bench supply material, or phone charging (needs isolation), or even lighting LEDs (needs too much power).

Tim

It was be foolhardy to develop with a power supply like this connected directly to the mains. if you use an isolation transformer during development, where is the problem? These things generally go into products which are entirely non-isolated, like fridges and washing machines.

[rob77]

interresting chip, but completely pointless for small volume production or one-off products. the savings on transformers and high voltage capacitors might be significant in huge volumes, but designing in additional safety because of no mains isolation would be much more expensive for small production volumes.

[tszaboo]

I was describing a power supply some years ago based on this principle! It is awesome that someone actually made it. I see a lot of reasons why someone would use something like this. Think of radio controlled relays, power meter, bias power for SMPS...

[mikeselectricstuff]

For this sort of application, Power Integrations' Linkswitch devices are pretty good

[Seekonk]

People have used this idea before, it just wasn't made into a chip.  We had a customer that had about 100 photo switches that used a power supply like this. Typical use for this type of product.  They were running off a single transformer at an industrial site.  Imagine all those little switches turning on at the same time.  It drove the line power nuts!  There must have been a lot of complaints. The German company redesigned the power supply  six months later.

[coppice]

For this sort of application, Power Integrations' Linkswitch devices are pretty good

Power Integrations produce a lot of variants on the theme of a very small switcher. I'm surprised they haven't included something similar to the Supertex/Microchip parts.

[coppice]

People have used this idea before, it just wasn't made into a chip.  We had a customer that had about 100 photo switches that used a power supply like this. Typical use for this type of product.  They were running off a single transformer at an industrial site.  Imagine all those little switches turning on at the same time.  It drove the line power nuts!  There must have been a lot of complaints. The German company redesigned the power supply  six months later.

Supertex have been making these things for a very long time. I think you'd need a fairly extreme case, like the one you described, for them to cause any problems. They are only for <1W applications.

[albert22]

if you use an isolation transformer during development, where is the problem?

The datasheet advices not to do that:

Line Transformer
During initial testing it is tempting to use an isolation
transformer or a variable transformer on the AC line. However the high inductance of the transformer (frequently in the mH’s) interferes with the normal operation of the SR086 and
should not be used

[dh]

For this sort of application, Power Integrations' Linkswitch devices are pretty good

This forum is a goldmine! I was really hoping there was something better than the SR086 or the LR645 out there.. Thanks Mike!

[Phoenix]

Looks quite similar to the electrophoresis power supply Dave did a tear down off a while ago ()... except for the presence of a transformer. Probably works in much the same way too.

[dh]

Yeah, that's really the point to all this extra effort... getting rid of the magnetic saves a lot of space and cost!