Shockingly piss-poor USB power supply

[amyk]

I wouldn't be surprised if the TH2267.1 was based on some other IC; there aren't that many ways to make a switcher IC and put it in an 8-pin package. Look around enough and you might find another with the same pinout and functionality.

[Zero999]

A switchmode mains supply with one transistor.... guess how well it performs...?

Apart from only being able to produce a fraction of the required power and shoddy construction I don't think there's anything wrong with using a cheap unregulated blocking oscillator fly-back converter as an SMPS. This is obviously the wrong application for it, a stable 5V supply is required for USB devices.

Did you actually count the number of turns on different windings?

You also mention about the temperature rise of the transistor and the power consumption. If the SMPS really used as much power as your meter says, the transistor would've melted long ago. I think it's just measuring the apparent power.

I thing the design is worth copying and would be a good way to power LEDs from the mains. Obviously the issue of isolation needs to be addressed, unless the LEDs are going to be in a fully insulated enclosure.

As others have mentioned another possible application is battery charging where there's another regulator. I've seen an unregulated mobile phone charger SMPs before which does have proper isolation between the mains and DC power out.

I've toyed with the idea of building a similar PSU but I wouldn't know what kind of tape to use for separating the primary and secondary. Is there a standard for this? I've dismantled apparently well-made SMPSes before and noticed they all seem to use a similar kind of yellow sticky tape between the primary and secondary.

[NiHaoMike]

Most transformers use Mylar tape for insulation.

[Zero999]

Sorry to bump an old thread but I didn't know where else to post this.

On the subject unregulated SMPSes I've found an example on the TC33167 datasheet.

It looks like parts from an electronic halogen transformer could easily be used to make this circuit which could be used as an alternative to an unregulated supply using a bulky transformer.

http://www.icwic.com/icwic/data/pdf/cd/cd057/Switching,%20DC-DC%20Regulator,%20Controller/a/85248.pdf

[ivan747]

I bet that last one was made by neither Nokia or Astec.

I have a genuine Nokia charger I don't need anymore, do you guys want me to take it apart?

[Rerouter]

also have on my hands a few old chargers of various sources and brands that i could probably give a teardown of,

[ivan747]

No need to get excited about an obscure custom part; switcher ICs are very common. One company "Power Integrations" has dozens of different product lines for flyback, forward, non-isolated, low parts count, etc. all available through Digi-Key with very good datasheets. I'm currently weighing my options for a project, it's between design my own around an IC (fun, expensive, dangerous, hooray) or buy a box of plug packs on ebay like Aurora did :-)

EDIT: two of the pictures on Jon Chandler's post on the second page have PI chips, for example

Why don't you use a Micro-USB connector for charging your project? You can supply an adapter easily or have the customer buy their own adapter like many manufacturers are doing.

[Mechatrommer]

for $7, i just got the "piss poor" Mains to USB adapter/charger and an electronic cigarette. dont turn it on, take it aparght!
edit: i believe this kind of thing is produced in humongous and distributed throughout the worldwide. for a single tiny of this, PF and harmonics noise may not be an issue, but imagine tens of thousands of households using it in harmony at the same time, i cant imagine what will happen to the power line... maybe the time has come where smps will take over the world!