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how to check a pulse transformer ratings?

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htcompany

New Member
hello,
i have smps with o/p of 5.7 vdc (i/p : 230 vac). this smps is having a pulse transformer as isolation. since transformer ratings are not provided, i want to determine the ratings. i want to design my own smps circuit using pulse transformer. but at the moment i am understanding this 5.7 vdc smps. i want to purchase the pulse transformer. what ratings should i tell to elecronics shop-keeper to purchase pulse transformer ?
please kindly reply.......here , an image is also uploaded.
 

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ronsimpson

Well-Known Member
Most Helpful Member
Why?
You have a switch mode power supply.
230VAC in and 5.7VCD out.
Do you want to know how many amps you can get from the supply?

Are you designing your own supply?

It is hard to know much about the transformer because I don't know the size. What is its length width height? (not counting the pins)

The amount of power is dependent on frequency, and what mode the supply is operating in.
 

schmitt trigger

Well-Known Member
pulse transformer's have two important characteristics:

1) Its primary to secondary turns ratio
2) Its maximum primary volt-seconds.

Let me explain 2):
Assume that the transformer has a maximum spec of 50 V-μS.
If you are driving it with a 5 volt squarewave, its on period should be no larger than 10 μS, otherwise it will saturate.

If your maximum duty cycle is 50%, that means that the maximum total period will be 20 μS, or 50 Khz minimum operating frequency.

You could build a variable frequency power squarewave oscillator. Start with -let's say- 100Khz @ 5 volt, 50%. Monitor the output with a scope and slowly start lowering the frequency until you start seeing a droop in the output voltage.
 

htcompany

New Member
Why?
You have a switch mode power supply.
230VAC in and 5.7VCD out.
Do you want to know how many amps you can get from the supply?

Are you designing your own supply?

It is hard to know much about the transformer because I don't know the size. What is its length width height? (not counting the pins)

The amount of power is dependent on frequency, and what mode the supply is operating in.

i want to design my own smps circuit using pulse transformer. but at the moment i am understanding this 5.7 vdc smps. i want to purchase the pulse transformer. what ratings should i tell to elecronics shop-keeper to purchase pulse transformer ?
 

ronsimpson

Well-Known Member
Most Helpful Member
i want to design my own smps circuit using pulse transformer.
Working with a SMPS on the power line is dangerous.
There are many DC to DC SMPS that are safe.
Example: 24 volts to 5.1V. Or 24V to LED driver.
This is a better place to start.
 
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