hi,
does anyone know how to bring down 600vdc with current approximately 6.667A to 3vdc, 5mA beside using a resistor network? is there is any voltage regulator that can come down the voltage of 600vdc to 3vdc?

 

Ouch!

Well, burning the power up with resistors would mean at least 3 watts for a 15mW output. You won't find a regulator rated for anything like 600V on the input. In any case, a simple 3V regulator may need 3 mA just to idle, so efficiency gets worse. Maybe a 3V zener and a 120k resistor would work ok.

There are ways to do a far more efficient dc/dc converter, but you won't be able to make it work without a complicated bootstrapping system (there's no voltage to run the converter's logic until the converter's running).

Maybe a resistor is the best solution, but what are you trying to do? Is extremely poor regulation, no surge capability, and poor efficiency ok?

 

what in the world are you geting 600 volts from??

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I'm no electronics god, i just talk too much.

 

The DC link on an 480VAC inverter runs about 600-700VDC. I don't know if that's what he's doing, but it's not exactly rare. Now, why you would want to do that, that's a different question!

j.

 

:shock: :shock: :shock: :shock:

 

You seem to be having the same issue I'm having with high voltage DC. I'm trying to step down the voltage from 600VDC to at least 30VDC and I'm not finding an easy solution. My application has to do with solar panels that can supply up to 600VDC when arrays are strung together and I'm trying to develop a monitoring system and want to tap off of the existing voltage available in the box to power my circuit. I don't think you will find a regulator that will drop the voltage down to that level and I'm having difficulty finding a DC to DC converter that will do this without spending a boatload of money.

 

need SMPS in both cases (600-->30V & 600-->3.3V).

flyback converter.
I got a 600Vdc link converter at work and at the moment we are using a external 28V supply to supply the converter control. We want to incorporate a PSU within the converter based around a similar design we used for a 270Vdc converter... but 600V is a bit different

The plan we have is to have a crude fixed duty step-down converter to take the 600V downto something more managable (say... 300V) and then use one of our present PSU designs to control the new rail more accuratly

with the 3v3 case you will need another step-down to take 30V to 3v3

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Once a problem is realised, the rest is just details

 

why not tap it off the first battery in the bank grab 12 volts there (i am assuming it is 12 volts in series of about 50 other batteries...

grab a dc to dc converter 9 to 18 volts in, 5 volt out and put a 3.3 volt regulator ... the output will be isolated from the orginal battery via a dc-dc module ... you can 1 watt ones and the like some old ethernet card have them too incase ya try and get one in hurry!

 

This is really bad practice. It will result in the unbalancing of the charge across the battery string; though at 5ma vs 6.7A it may not be much of an issue in this case.
The OP really needs to tell us what the source of the 600V is before we can give valid advice. If it comes from a switching regulator, you could add a coil to the transformer to tap at a lower voltage, etc.

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I think you have no idea how leaky batteries are (self discharge rates can be as high as 20%per month on lead acid/gel) Besides they should not be charged in series that would be more prone to failure each battery should be charged individually. But lets do the maths.

(6700 milliamp hours(100%)- 5milliamphours) = 6695milliamp

Percentage loss on cell in terms of capacity = 6695/6700= 99.92 percent. Now considering most lead acid system rarely charge to 100% ie they cut out at 14.4v and most do not factor in temperature of cell which also affect capacity ...

So in short I think your comment is hog wash considering things like self discharge rates, losses in connections, and system will never call 100% of the battery capacity (otherwise going to be replacing alot lead acid cells) I think it can stand to lose 0.08 percent on one cell to acheive the goal !

 

No DC-DC chips accept 600v input. Maybe you can design a DC-DC circuit with high voltage MOSFET. But I prefer the resistor solution, after all the output is only 5ma.

Mike

 

Please do not answer my ideas with stupidity if you read correctly I said to tap of 12 volts from the first battery ! READ READ READ !

 

I haven't read your answer at all. I was answer the first post.I'm not interested in your idea and won't read it.

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Well if you read my post you would understand how a DC -DC could solve the problem ! Instead be ignorant as it just proves to me you know nothing !

 

Ahem.... All 12v lead acid batteries are actually 6 2V cells in series. This is what an equalization charge cycle is for.
Maybe YOU should read my posts more carefully:
Besides, the OP never mentioned batteries in this thread anyways. I stand by my original post; tapping a battery string is bad practice. Think about this scenario: what happens if the bottom battery in the string goes open or is disconnected? Voila, -588 volts where there was once 12V!!!!

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