Author Topic: How to add soft-start feature to a PSU?  (Read 6723 times)

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Offline TheHolyHorse

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Re: How to add soft-start feature to a PSU?
« Reply #50 on: June 23, 2019, 12:33:02 pm »
Here is mine.

BTW if you're making your own symbols and footprints save them in a project specific library and include that library with the project files. RN some symbols are missing.
Sorry.I didn't save it into project specific library.What can I do.
Are you having problems with footprints.

Not the footprints only library symbols not showing up.
 
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Offline Arjunan M RTopic starter

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Re: How to add soft-start feature to a PSU?
« Reply #51 on: June 25, 2019, 12:55:28 pm »
 After looking at your  schematic it turns out that you are doing I limiting as i am doing :-//
« Last Edit: June 25, 2019, 12:56:59 pm by Arjunan M R »
 

Offline TheHolyHorse

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Re: How to add soft-start feature to a PSU?
« Reply #52 on: June 27, 2019, 05:32:42 am »
Yes
 

Offline Arjunan M RTopic starter

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Re: How to add soft-start feature to a PSU?
« Reply #53 on: June 27, 2019, 09:49:44 am »
Then what is the best way to add current limiting?

Mine is just using some mosfet as pass transistor. It's basically doing what the voltage regulator is doing internally.
:-//
 

Offline TheHolyHorse

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Re: How to add soft-start feature to a PSU?
« Reply #54 on: June 27, 2019, 09:55:42 am »
Then what is the best way to add current limiting?

Mine is just using some mosfet as pass transistor. It's basically doing what the voltage regulator is doing internally.
:-//

Oh well I just meant that I used mosfets instead of volt regs.
 

Offline exe

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Re: How to add soft-start feature to a PSU?
« Reply #55 on: June 27, 2019, 09:58:58 am »
Oh well I just meant that I used mosfets instead of volt regs.

You mean discrete regulator? :) What fet did you use and what is the voltage/current accross it? Most fets are not rated for linear operation, but if it is beefy and battle-tested then you probably can get away with it.
 

Offline TheHolyHorse

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Re: How to add soft-start feature to a PSU?
« Reply #56 on: June 27, 2019, 10:14:52 am »
Oh well I just meant that I used mosfets instead of volt regs.

You mean discrete regulator? :) What fet did you use and what is the voltage/current accross it? Most fets are not rated for linear operation, but if it is beefy and battle-tested then you probably can get away with it.
.
Yeah, I'm using FQP17P10 I think that's the name. 20 ish volts and 4A
 

Offline exe

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Re: How to add soft-start feature to a PSU?
« Reply #57 on: June 27, 2019, 01:59:18 pm »
Yeah, I'm using FQP17P10 I think that's the name. 20 ish volts and 4A

Cool, this one has SOA down to DC. That's rare nowadays :(
 

Offline TheHolyHorse

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Re: How to add soft-start feature to a PSU?
« Reply #58 on: June 27, 2019, 04:53:53 pm »
Yeah, I'm using FQP17P10 I think that's the name. 20 ish volts and 4A

Cool, this one has SOA down to DC. That's rare nowadays :(

Yeah I hope I get it working  ;D
 

Offline Arjunan M RTopic starter

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Re: How to add soft-start feature to a PSU?
« Reply #59 on: June 29, 2019, 06:31:08 am »
Here is mine.

BTW if you're making your own symbols and footprints save them in a project specific library and include that library with the project files. RN some symbols are missing.
Sorry.I didn't save it into project specific library.What can I do.
Are you having problems with footprints.

Not the footprints only library symbols not showing up.
Fixed it, try now :).
 

Offline BravoV

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Re: How to add soft-start feature to a PSU?
« Reply #60 on: June 29, 2019, 10:05:53 am »
Cool, this one has SOA down to DC. That's rare nowadays :(

Becareful, the SOA shown that its has DC chart, it is not realistic temperature as the TC at 25C, especially its not a linear mosfet.

Once crossed the 25C, you just can not interpolated that DC chart, as sometimes the max current will be reduced significantly, especially for non linear mosfets.

An example of a proper and true linear mosfet FBSOA, watch the yellow highlighted areas and compare both charts.

« Last Edit: June 29, 2019, 10:10:26 am by BravoV »
 
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Offline TheHolyHorse

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Re: How to add soft-start feature to a PSU?
« Reply #61 on: June 29, 2019, 09:51:18 pm »
Cool, this one has SOA down to DC. That's rare nowadays :(

Becareful, the SOA shown that its has DC chart, it is not realistic temperature as the TC at 25C, especially its not a linear mosfet.

Once crossed the 25C, you just can not interpolated that DC chart, as sometimes the max current will be reduced significantly, especially for non linear mosfets.

An example of a proper and true linear mosfet FBSOA, watch the yellow highlighted areas and compare both charts.



I'll have to see if it explodes ;D If it doesn't great, if it does well now I've learned something new.
 


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