high turns ratio smd transformer?

Sorry, I don't have the time to go looking for you this morning - but have you considered using two transformers (secy of first connected to primary of second), instead of one?

OK, it isn't usually as efficient as a single transformer but can actually require considerably less space (volume as well as pec area) and be a lot cheaper and lighter.

could you use a current transformer backwards? the turns ratios are in the range you suggest. sammmm

Sorry, I don't know what "SMD" means and you didn't state the frequency of interest, but it sounds like your app is very low power. Have you investigated vacuum tube audio transformers? They usually match impedences from 5-10kOhms to

4-8 Ohm speaker impedances. One company may have what you need. Check as a source. Your reqmts don't sound too tough. Robert

starfire wrote:

Surface Mount Device.

Thanks for the reply.

I have considered using two transformers connected as you say. That would be a workable solution with existing devices I am aware of. Sprague-Goodman makes the GLSG family devices, one of which is a 1:17 turns ratio. I could even use two different turns ratios and match closer to the desired total ratio. I will probably go that route if I can't find a single transformer solution.

I would really like to reduce the footprint, though, as this is for a very small surface mount device (SMD) application.

Thanks again for your input.

Dave

Thanks for your suggestion.

As a matter of fact, I'm experimenting with such a device right now. I've obtained two samples of a 1:50 turns ratio transformer from Flux. Unfortunately, the primary (going from 1 to 50) is effectively a single turn, which means very high current in the primary side, unless I use a limiting resistor in line. I'm trying to drive this from a very low current oscillator and keep the overall system current low (portable application).

When I inserted a limiting resistor inline with the transformer primary, the effective voltage across the transformer primary is decreased and I only see smaller secondary voltage. The secondary voltage is larger than the power supply voltage, though, so I think this is going the right direction. The limiting resistor keeps the overall system current down, also. I'll continue some more experiments with this transformer, though. As you say, the turns ratio is in the range I was hoping for.

Thanks for your suggestion.

Dave

Thanks for your suggestion.

I will check the sources you've listed for such a device. I think an audio transformer with the correct impedance matching (effectively, turns ratio) and a large enough primary impedance would be a good solution. I should be able to drive it through my oscillator source (enabling a FET switch) and keep the overall current usage low.

Thanks again.

Dave