Multiple output regulation problem, DI152

Posted by: kemred on 07/12/2012

Dear Sir,

We have make a double (each 5V 0,6Aoutput) Total 6W SMPS. We use the similar design with respect to DI152 since we need large input voltage range. controller is opto/zener.

The problem is regulated output changes from 4,23 to 5,15 V from 1.6W load to no load, while the other ouput(unregulated) changes from 8,2V to 4,914.. In this case the un regulated output is 0.1 W. as you can see with respect to zener controller the load regulation is very poor. what can be the problem, I don't want to use regulator like TL431...

Secondly when I loaded the unregulated output to 1W,( connect 25 ohm load), the unregulated output decreases to 1.4V, the regulated output is increases by 0,1 V to 4.33. So as you can understand both line and load regulations are very poor.

So what can be the problem, as I read from forum there must not be such a big difference for correct design.

Best regards,

Comments

You can check the polarity of the transformer, change the current limit setting first. But anyway, something is wrong in your circuit. PLS upload your schematic!

thanks

You can find the schematic which is same with DI-152 in input design except bridge, I want to ask something, in this schematic how can D2 is connected to line before or after to bridge.. Since we want AC/DC input I think this connection can be made.. Do we really need D2 in this shematic, what is the purpose?

You can remove D2 and connected theconstant current circuit for BP to the DC input plus, but the power loss will be higher because of thehigher peak charge voltage of input cap.

Based on your description, your circuit suffers not only the cross regulation issue, but also some other issue. So i guess somehing wrong in your design. For the cross regulation issue, optimize transformer is the only choice. Because the dual outputs are both 5V0.6A, you can use sandwich structure for secondary and secondary, and also always wind the two output windings together.

So from your comments I understand connecting D2 anode to rectified sinusoidal waveform can be done, but I must connect D2 in order not to increase the loss..

The main problem is the two output must be 2.5kV isolated and there must be creepage between them nearly 6 mm due to my design.. So I thing winding together is not suitable for safety issues, I have to add isolated band between two winding...

Hopefully, TIW can meet your safety requirement.

Unfortunately we could not use TIW since our local manufacturer does not support TIW and says it will be too expensive using TIW... So I have to find another solution...