# impedance matching problem

Discussion in 'General Electronics Chat' started by rky, Nov 16, 2009.

1. ### rky Thread Starter New Member

Nov 16, 2009
22
0
hi people,
i am e.c. student and have problem of impedance matching...
for that i have designed a transformer which converts 60 volts dc to 12 volts dc........as 5:1 ratio of transformer......
now i have two different load which have different impedance.....
one have 4ohm and another have 2 ohms........
now my circuit works with load of 4 ohms bt didnt work with load of 2 ohms
so i think there is a chance of impedance matching.....
please help me out
regards
rky

2. ### Papabravo Expert

Feb 24, 2006
11,946
2,560
Something is wrong here. Transformers don't work with DC voltages. Also the turns ratio sets the impedance ratio. The only way to have it work with different loads is to change the source impedance.

3. ### studiot AAC Fanatic!

Nov 9, 2007
5,003
521
First guess you meant AC

Then the turns ratio n = Ts /Tp = √(Rs/Rp) = √(Zs/Zp)
Where
Tp = primary turns
Ts = secondary turns
Rs = source resistance
Rp = load resistance

Alternatively you really do want a DC impedance transformer, then you will have to use a transistor or op amp and match input and output impedances.

4. ### rky Thread Starter New Member

Nov 16, 2009
22
0
thank you sir......
i know that transformer works on AC signal......
but due to my application i have to made the 60 voltage form full wawe bridge rectifier...and it is pulse transformer......
transformer has two windings....in primary side at one pin i have given that 60 voltages and on second pin at primary side pulses of 1mhz and 3mhz.....
so i will get o/p of that, pulses above 60 volts dc biasing......
but when i am trying to set 3mhz frequency......my o/p get low.....
so my circuit is working on 1mhz at load of 4ohms........but not working on 3 mhz of 2ohm.........
so plz try to solve my problem.....

Last edited: Nov 16, 2009
5. ### SgtWookie Expert

Jul 17, 2007
22,199
1,801
What are you using for a transformer core? Air?

Number of turns on primary and secondary?

Wire gauge?

6. ### Papabravo Expert

Feb 24, 2006
11,946
2,560
I cannot understand what you are describing. This does not sound like anything I've ever seen before. A schematic would help. Stop using strings of periods they have no syntactic or semantic meaning.

7. ### studiot AAC Fanatic!

Nov 9, 2007
5,003
521
Please confirm that you are trying to make a pulse transformer.

These are normally used one shot (pulse) at a time and have special design requirements.

8. ### rky Thread Starter New Member

Nov 16, 2009
22
0
just look at my attachment
here i/p signal of 1mhz and 3mhz pulses of 9volts....
now my circuit works at 1mhz bt didnt work with 3 mhz........
at 1mhz the load impedance of 4 ohms... and at 3mhz it is of 4ohms
at 1mhz i connected load impedance of 4 ohms my circuit works
bt when i connected to load impedance of 2 ohms ...........my circuit didnt work
i think it is problem of impedance matching........
plz help me out.....
thank you........
rky

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9. ### SgtWookie Expert

Jul 17, 2007
22,199
1,801
With a load of 4 Ohms, your 7805 regulator would need to output 1.25 Amperes current in order to maintain a 5v output. This is actually beyond it's design limit of 1A for constant output.

With a load of 2 Ohms, your 7805 regulator would need to output 2.5A. This is beyond even its' maximum output current.

But you haven't answered the questions about the transformers that you are using.

10. ### rky Thread Starter New Member

Nov 16, 2009
22
0
yes i want to design pulse transformer.................
and the primary winding 80 nd secondary has 16
5:1 ratio
and in my schematic i want to replace TR1 transformer............

11. ### rky Thread Starter New Member

Nov 16, 2009
22
0
anybody knows about pulse transformer????

12. ### SgtWookie Expert

Jul 17, 2007
22,199
1,801
This belongs in the Homework Help forum.

This is obviously an academic exercise.

13. ### rky Thread Starter New Member

Nov 16, 2009
22
0
no....its my project....not homework kind of thing.........

14. ### t06afre AAC Fanatic!

May 11, 2009
5,936
1,227
Are you using Mega Hz? Is your core material suited to be used at this frequencies? Just asking

15. ### rky Thread Starter New Member

Nov 16, 2009
22
0
ya....
i am doing this in 1Mhz perfectly....
bt problem coming in 3Mhz....
and i ve made 5Mhz transformer.....
so not an issue for frequency........

16. ### lmartinez Active Member

Mar 8, 2009
224
6
This sounds like a fun and complex project. When designing a switching transformer to operate at very high switching frequencies, there are many other parameters that shall be accounted for. Not knowing what your lever of expertise is in this subject matter, I would suggest that you may start by reading the following: http://focus.ti.com/lit/ml/slup126/slup126.pdf
Good luck....

17. ### rky Thread Starter New Member

Nov 16, 2009
22
0
thank you
but if you peaple want to suggest something else.... you ll most welcomed by heart......
thank you once again
rky