12V to 50V converter??

[Ralph Weaver]

Before I start bugging the local analog IC reps...

Any thoughts on the best way to build a 12V (auto battery) to 50V DC-DC converter. I need at least 5A output.

Thanks.

[dleroi]

Before I start bugging the local analog IC reps...

Any thoughts on the best way to build a 12V (auto battery) to 50V DC-DC converter. I need at least 5A output.

Thanks.

Ralph,

Here are a couple of projects that could easily be modified for your needs. If nothing else, they're excellent tutorials.

http://sound.westhost.com/project89.htm

http://members.tripod.com/valveaudio/Membuatsendiri.htm

- Don

[tungym]

THANKS. But that is too much for me .

[Ralph Weaver]

Thanks, great stuff. That'll help me get started. I can work out the details.

[PDK]

Hi,

You might be able to use this DC converter (http://www.oatleyelectronics.com/kits/Notes/k168.jpg) . It is a 12 to ? (24ish V depending on resistors and transformer winding). You would need to beef up the transformer size and # of winds to suit the 5A @ 50V output. I believe the SC3525 is capable of driving several fets from the one output (2 and maybe 3? Check the datasheet) so you could parallel a few to keep the power dissipation down. Should be a good start though.

Hope it helps
Phil

Don't know how common the SC3525 is (probably easy to get) but I got some from Futurelec (http://www.futurlec.com.au/test13.jsp?category=ICOTHERS&category_title=Others&main_menu=IC&sub_menu=ICOTHERS) and I see that they are at Oatley Electronics (http://www.oatleyelectronics.com/componentsa.html) as well

[vintage1]

haha. I know what you need. A pair of different wound motors. Use the 12v one as a motor, and hook it up to the 50v wound one as a generator.

its called a rotary converter. In fact, you can put the two pairs of windings on the same armature as well.

[Miami Mike]

Over here they're called dynamotors. The used them in vehicles to power electronic equipment before transistors were invented.

[vintage1]

Over here they're called dynamotors. The used them in vehicles to power electronic equipment before transistors were invented.

..and also afterwards. They have a huge and simple advantage...the rotor intertia acts to smooth out gross dips in the input voltage. a couple of lb spinning at 30K RPM holds a lot more eneregy than a bank of similar sized capacitors..

Never heard of 'dynamotor' though. I like it.

[Ralph Weaver]

Hi,

You might be able to use this DC converter (http://www.oatleyelectronics.com/kits/Notes/k168.jpg) . It is a 12 to ? (24ish V depending on resistors and transformer winding). You would need to beef up the transformer size and # of winds to suit the 5A @ 50V output. I believe the SC3525 is capable of driving several fets from the one output (2 and maybe 3? Check the datasheet) so you could parallel a few to keep the power dissipation down. Should be a good start though.

Hope it helps
Phil

Don't know how common the SC3525 is (probably easy to get) but I got some from Futurelec (http://www.futurlec.com.au/test13.jsp?category=ICOTHERS&category_title=Others&main_menu=IC&sub_menu=ICOTHERS) and I see that they are at Oatley Electronics (http://www.oatleyelectronics.com/componentsa.html) as well

Thanks!

[bravokilo]

Ralph, hi, you probably solved your problem already but if you are not happy with the set p you have, here is another idea (delayed):

Find a UPS. They run from batteries and if lucky, on 12 volts. They produce your country's wall voltage ()110V in the U.S.). Step it down with another transformer and put diodes to get back to DC. Of course filters or even regulators.

Bravokilo :)

[Ralph Weaver]

Ralph, hi, you probably solved your problem already but if you are not happy with the set p you have, here is another idea (delayed):

Find a UPS. They run from batteries and if lucky, on 12 volts. They produce your country's wall voltage ()110V in the U.S.). Step it down with another transformer and put diodes to get back to DC. Of course filters or even regulators.

Bravokilo :)

Good idea. Could be useful even just for parts.

[David T]

Ralph, I am part way through a design for a 6 cell 5A lipo charger using an LT1680. Once working properly I may try doubling current or volts (I have 12x5Ah lipos to charge). This chip will handle your requirements if you can find ring cores to make an inductor that can handle the throughput. Let me know if you want more details.
Regards, David.
http://www.linear.com/pc/productDetail.do?navId=H0,C1,C1003,C1042,C1031,C11 15,P1597

[hermperez]

David, that chip is a very complete solution for a DC-DC converter..please post details of your design ..may be able to make a high speed charger for A123 lipos.

Ralph, I am part way through a design for a 6 cell 5A lipo charger using an LT1680. Once working properly I may try doubling current or volts (I have 12x5Ah lipos to charge). This chip will handle your requirements if you can find ring cores to make an inductor that can handle the throughput. Let me know if you want more details.
Regards, David.
http://www.linear.com/pc/productDetail.do?navId=H0,C1,C1003,C1042,C1031,C11 15,P1597

[David T]

It is an interesting chip. Its low voltage cutoff is useful to protect the source battery. I will add the design to my site and post a link here as soon as a friend has tested it thoroughly.

[Ralph Weaver]

Thanks. Looks like a nice chip. The problem that i have is that i need to be able to adjust the output from approx 1V up to 48V. Boost chargers typically will not go below the input voltage. I've been looking at flyback or sepic. might be easier to do a boost followed by a buck. We'll see...

[Ralph Weaver]

Perhaps we should split this thread up? :D
Ralph,
I haven't attempted such a project before, but this link] (http://sound.westhost.com/project89.htm) is a pretty good guide.
A uC driving a pair of FETs connected to a high frequency transformer will do the job.
Current sense resistors and a voltage divider in the output will let you regulate the voltage.
Atmel has a nice appnote on how to implement a constant-current supply using an AVR, you might want to have a look at that.

Realize though, that 48V at 5A is 240 watts, even given 90% efficiency, you are looking at ~22 amps of primary current. :)

I've seen the power supply at the link above - may be what I end up doing.

I think I've seen the AVR app note, I'll check it out again. I'm currently using Freescale uC's, but easy enough to convert.

[hermperez]

it is not easy to adjust the output voltage on that design, it is controlled by the windings ration on the transformer.

Herm


I've seen the power supply at the link above - may be what I end up doing.
.

[Ralph Weaver]

it is not easy to adjust the output voltage on that design, it is controlled by the windings ration on the transformer.
Herm

I've got a kit based on the same IC. It takes 12V in and gives up to 24V, 2A out. The exact V out is determined by a resistor divider from the Vout going to the feedback (pin 1) on the IC. A pot would make it variable from 0-24V.

The number of turns could be changed to give 48V max and the parts upgraded and heat sinks added to get more current.

[simingx]

You might not be able to get it to go to 0V as the IC (SG3525) has a minimum duty cycle.

[hermperez]

does it use a second stage voltage converter?, otherwise the output voltage would be dependent on the load.

I've got a kit based on the same IC. It takes 12V in and gives up to 24V, 2A out. The exact V out is determined by a resistor divider from the Vout going to the feedback (pin 1) on the IC. A pot would make it variable from 0-24V.

[Ralph Weaver]

does it use a second stage voltage converter?, otherwise the output voltage would be dependent on the load.

From what I can tell it's a regulator. It varies the duty cycle to maintain the reference voltage. For audio use, the real regulation occurs in the amp, so they don't care so much, but from the data sheet, it looks like it should regulate.

[mjws]

David, that chip is a very complete solution for a DC-DC converter..please post details of your design ..may be able to make a high speed charger for A123 lipos.
Heh. Man am I glad to see someone going after that goal. I'm way back on the learning curve on these circuits and electronics.

A high output high voltage dc-dc tool would be awesome. I can wrap my head around getting the power supply in order, but I would kill for a plug and play cccv controller that could do 700w or so. Even a system that could give me +- 10V from a dc input and regulate 20A or so of current. (Think Huge variable BEC on steroids). The huge benchtop supplies get pricey when you hit these levels.

Many of the simple electronics type projects seem to be based around very low power levels. Hope you guys are successful. I'll be watching and learning.

Regards,

Mike

[jermo]

nm, ac to dc ckt..
Jermo