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Old 20th June 2013, 07:58 PM   #1
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Default Current Control Using TL494

Hello good afternoon

Participate in the forum ah some time however, I read enough posts and learn a lot

Now I need some help, I'm trying to adjust a current of 0 to 50A with TL 494! would be possible? if so would like to know how to calculate this current setting to put in a half-bridge SMPS that I'm developing.
already researched on various websites however not clear how to perform this calculation.

any help will be welcome

since already appreciate the help.

Last edited by heidern; 21st June 2013 at 12:06 AM. Reason: fix the title
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Old 21st June 2013, 11:23 PM   #2
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Thread title now in English.
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Old 23rd June 2013, 01:19 AM   #3
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desculpe é por que eu não soube editar

Obrigado Cal Weldon
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Old 23rd June 2013, 01:20 AM   #4
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is sorry for what I did not know edit

Thanks Cal Weldon
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Old 23rd June 2013, 03:42 AM   #5
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Break down your requirements.

What feedback signal does the 494 need to regulate to?

How are you measuring your 0-50A?

What circuitry do you need to get the measurement of 0-50A to the feedback point of the 494?

We (anyone) needs more information.

Otherwise our suggestions will meet with: "I can't do it that way because..."

What are you starting with and what do you need exactly?

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Old 25th June 2013, 02:56 PM   #6
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I made changes to an ATX power supply, now I want to regulate the amperage her

I got this stuff on tl 494, however I do not know sure how to calculate this current control!


TL494 Smps Kontrol Entegresi Hakk?nda | Elektronik Devreler Projeler 320 Volt

Would you like help from experts SMPS!

thank you


Heidern
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Old 27th June 2013, 03:17 PM   #7
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Quote:
Originally Posted by DUG View Post
Break down your requirements.

What feedback signal does the 494 need to regulate to?

How are you measuring your 0-50A?

What circuitry do you need to get the measurement of 0-50A to the feedback point of the 494?

We (anyone) needs more information.

Otherwise our suggestions will meet with: "I can't do it that way because..."

What are you starting with and what do you need exactly?

hi im busy developing a inductor tes fixture circuit around a TL 494 the new version will have current sense control.. when you say you want current limiting then i assume you want the system to shut down if it reaches the pre-defined user threshold max = 50A

The TL 494 has 2 error amps, a dead-time control DT pin and a feedback pin, any of these can be configured to do what you need depending how you configure it. I think the IC can work in both in voltage and current mode.

In my application im using the one error amp as a current sense (wired up as a comparator with a reference and a sample taken from a 0.047ohm shunt) if the current exceeds the threshold it shuts down the chip. the other error amplifier is wired as a comparator as well only this time i use it to monitor the temperature on the heat-sink and will shut-down ic if the temperature exceeds a pre defined temperature.

my sample current is taken from a 5watt 0.047 shunt to detect up to 10amps.. and using a shunt for this dont pose to much issues regarding dissipation i assume you understand the advantages of resistor shunt vs magnetic current sense..

Anyway to sample 50 amps is simple, you can get hold of a small toroidal core and build a smalll current transformer CT, run 1 amp through a copper wire and through the core, and see what the sample voltage is, do the math and determine the maximum saturation point of the current core and add some low pass filtering with a simple RC filter. if you dont wanna go through all this effort buy one current transformers are not that expensive and prices are becoming relativity cheap nowadays.

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Old 27th June 2013, 05:11 PM   #8
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Exactly! this is what I want, when the power supply to reach 50A disconnect it, I want this current is adjustable from 0 to 50A,

you have the schematic of this regulation or how can I do this? and how can I calculate the resistors for this current?

I would make this adjustment without using current transformer!
if u can provide a schematic of how I can do this I would greatly appreciate it!

Thank you for your attention!
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Old 27th June 2013, 06:31 PM   #9
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Quote:
Originally Posted by heidern View Post
Exactly! this is what I want, when the power supply to reach 50A disconnect it, I want this current is adjustable from 0 to 50A,

you have the schematic of this regulation or how can I do this? and how can I calculate the resistors for this current?

I would make this adjustment without using current transformer!
if u can provide a schematic of how I can do this I would greatly appreciate it!

Thank you for your attention!
hi

I don't have a diagram bit its very simple wire the error amp as a comparator with and adjustable reference, with the sample taken from the current transformer and you done (its as simple as a that), there are loads of circuits that does this, some use faster comparators like LM 339 or better with faster response times some just use the built in error amps wired as a comparator the principle is what you need to understand.
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Old 27th June 2013, 06:45 PM   #10
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Ok Reactance!

I have to learn the principle of operation of TL494, hardly think about these functions, I would love to learn, do not have much experience in smps, want something even simpler than the link I posted above, so I can start learning and implement in a half bridge I have on the bench for testing.

be able to explain to me some more detail how the link, how to calculate the resistors.

again grateful
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