Looking for help in designing circuit with lnk306

[RafPe]

Hello everyone!

I'm looking for help in choosing components and preparing protoype board with use of lnk306 chip.

What I'm looking into is following :

• Understand why choosing specific components and not just copy info like monkey
  
• Make device that will be safe to use at home (target is to use in light switching scenarios)
• Survive this project without damage to my health or life
  
• I would like to get output of around 5V to power mcu (probably Atmega88) and RFM69CW

I found pcb design that I could make use of

However I might be wrong in finding information in DS because I seems to miss information how do I set output to 5V ?

Input will be 230V AC


Looking forward for your comments


Regards
Raf

 

[TedA]

Raf,

If you can, it's helpful to provide links to information that EPF members will need to answer your questions. The person who may best be able to help you may not have time to go try to locate this information.

I'll try to help with this:

The Lnk306 is a product of Power Integrations, http://www.power.com/.

Power Integrations make many different sorts of power supply chips, many of them intended to take power from the AC line (mains). I have had good results using their devices. If you are in the US, Mouser sell these. Less than $2 for one.

General information on the Lnk306 is here:

http://ac-dc.power.com/products/linkswitch-family/linkswitch-tn/

This page includes links to much more information on using this device.

The data sheet is here:



http://ac-dc.power.com/design-support/product-documents/data-sheets/linkswitch-tn-data-sheet/



An app note is here:

http://ac-dc.power.com/design-suppo...cation-notes/an-37-linkswitch-tn-design-guide

The above links should lead you to information about choosing components and setting the DC output voltage.

Before getting too far along, you need to be sure that this part is a good choice for your application.

It is clearly intended to provide a small amount of DC power where isolation from the AC line is not needed. Your low voltage DC output is connected to the line and is not safe to mess with. Any microcontrollers or other devices connected to them will also be "hot".

Most hobby projects would be powered much more safely by a small isolated power supply, possibly a "wall wart" style.

Another consideration about the Lnk306 is that it appears to have a rather loose output voltage specification, at least when using the more basic application circuits. The regulation may not be the tightest, either. Probably it would be good enough, but we don't know much about your requirements.

Other Power Integrations parts might be better choices. Some are intended for use in transformer isolated power supplies.

To answer your question about setting the Lnk306 DC output voltage, it is set by resistors R1 and R3, as seen in the recommended PCB layout drawing in your first post.

In the circuit, C3 is charged up to about the DC output voltage while D1 is conducting, which will happen just after the power switch in the Lnk306 turns off. R1 and R3 divide the voltage on C3 to feed the FB pin.

The chip drives current pulses into the load until about 49uA of current flows into the FB pin. This will occur when the FB pin reaches around 1.65V above the C pin. Once the FB pin sees this current, the next current pulse is skipped.

See page 9 of the data sheet.

Risking looking a bit like a monkey, one could use the 12VDC / 120mA output circuit shown on page 4 of the data sheet, but reduce the value of R1, to get your 5V output. You'd want about 4160 ohms.


Ted

 

[RafPe]

Hey ,

Thanks for the detailed information. So to put maybe more detailed project clarification this device would provide current for uC teamed with RFM radio and would be sitting in my room lamps. At least that was the assumption.

Now more I read about this it seems to be less useable for this. Goal of this project would be to have small AC=>DC to provide current for uC to switch/dim high current. Reason why I didnt go with wallmart style of power units is I would like to be able even for my self to manufacture them in their small factor size.

Ted are there any other alternatives you are aware about that I could potentially use ?


Also I have used PI expert program to calculate values I need to 5V - altough I have choosen to full wave rectification which means I would need to use a bridge ?

 

[RafPe]

Really ? AC -> 7805 -> DC @5V ?

Im not expert but it does not seems to be safe to advice that to people

 

[davenn]

its really bad advice from ver chan I'm deleting his post

he obviously doesn't understand what you are doing

 

[ver chan]

its really bad advice from ver chan I'm deleting his post

he obviously doesn't understand what you are doing

thank you for honest and transparent expression of your point of view,,,,,,,,,,,,,,,,,,,,,,,,,yes i may be wrong,,,but i dont intend to make anyone to have mistakes,,,and if somebody did a mistake from a wrong advice, it can be a lesson and a good opportunity to examine HOW does it came to be wrong?????,,,,,

 

[TedA]

Raf,

It seems that we are not being very helpful to you. I feel that I don't know enough about what you are trying to do to be able to offer useful advice.

I have no idea what a light switching scenario might be, nor medium or heavy-duty switching scenarios, for that matter.

You might try telling us something about the rest of the system this power supply is intended for.

It would also be helpful to know how many you expect to buy or build, and if your purpose is to learn about power supply design, or just to get something that works.

A brief description of the test instruments you can use for design and debugging the project might also help steer us toward suggestions more useful to you.

Ted

 

[davenn]

thank you for honest and transparent expression of your point of view,,,,,,,,,,,,,,,,,,,,,,,,,yes i may be wrong,,,but i dont intend to make anyone to have mistakes,,,and if somebody did a mistake from a wrong advice, it can be a lesson and a good opportunity to examine HOW does it came to be wrong?????,,,,,

when the advice is downright dangerous and could potentially be lethal, I wont leave the post visible.... I wouldn't want some one to try it and kill themselves... just not worth the risk to leave it in public view

be careful of advice you give
that will be all on this subject OK

now back to the thread topic please

Dave

 

[RafPe]

Hey guys ,

So this is what I'm looking at :

+ I'm doing home automation for my self at my home.
+ For that I need to have 5V/3,3V available next to 230VAC. Reason for having this is I would like to have control circuits based on AVR with RFM radio modules.
+ For the reason above I'm researching an option to understand and build like 10-15 small circuits that would be controlling high voltage

the IC in question Ink306 was something I came across which would be small factor AC=>DC (altough its transformerless)

From the tools I can use I have Osciloscope from Rigol / Own etching machine to prorotype circuits / solder station and couple of evaluation kits from AVR. So potential in testing and debugging is quite good

As mentioned before - I would like to understand what I'm building - so hence the questions for guidance


If anyone can point to maybe other suggestions - I'm open for that as well


Regards
Raf

 

[ver chan]

when the advice is downright dangerous and could potentially be lethal, I wont leave the post visible.... I wouldn't want some one to try it and kill themselves... just not worth the risk to leave it in public view

be careful of advice you give
that will be all on this subject OK

OK- understood, i will be more careful next time, thanks for correction.