I have 36-75 DC input and need the following outputs
1- +-65v @70ma
2- +-15v @150ma
3- +5v @ 200ma
What is your cheapest solution idea?
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Sounds like a custom transformer with 3 secondaries, and turns ratios of 36 to 66x2 center tapped, 16x2 centertapped, and 6 volts? Chop the 36v on the primary Real Fast and have bridge rectifiers and ldo regulators on the secondaries?
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For the first output you need some kind of buck/boost converter. Complicates matters a bit.
There are not that many cheap switcher ICs that accept such high input voltages.
You can't do it efficiently without a switcher. Assume 76VDC input, linearly regulated to 5V@200mA, that's about 15W of waste heat, and about 9 for the 15V.
1 - Buck-boost
2 and 3 - Buck for 15V and an linear for 5V output.
I don't know CI for 75V, only for 60V, now you need to search, go to TI (National Semi), ST and Linear and use their search..
Transformers do not work well with DC .. (Sorry Bob - could not resist) :)
Propably a simple current controlled PWM supply. There are many application notes of similar things out there. The only hard and expensive part here is the transformer. Everything else is cheapo everyday components like the PWM controller and the MosFET.
PWM is needed here as Your supply may fall below the 65 volts specified.
You could start by reading the Data sheet of UC284x PWM controller.
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Yeah, but I said 'chop the 36V Real Fast'. Like with an h-bridge running from the 36v, outputs go to the primary.
Consider the classic flyback converter, simple to design with multiple outputs.
Oh. Sorry Bob ... What is the matter with these hands? Especially the right hand index finger seems to have a life of it's own.
I realized the thing right after poking the send button...
what about generating outputs using MC34063 for eahc output. I do not want to use a transformer!
I tried to build a 30V 1A form input then design separate regulators using MC34063 for additional outputs @ 2X times the rated current.
Do you think Am â€˜I complicating things?
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