Power Supply Soft Start Board (V2)

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nrg2009

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Joined 2009
TANDBERGEREN said:
But otherwise I totally agree with You. Although I always bypass them with a relay after a suitable inrush-time. Again to secure extended service-time.
Click to expand...

So effectively what you are doing is replacing R15-R18 with an NTC (CL30)?

- this has the inrush running through the CL30
- when the relay connects it shorts out the CL30

Is that safe? Is it effective and are there any benefits of replacing R15-R18 with a CL30?

I am trying to decide if I should build this SS-board for an F5Tv2 with 1000VA and 200k uF caps.

Thanks for all your contributions!
 
TonyTecson

TonyTecson

Member
Joined 2003
TANDBERGEREN said:
Just pointing at a tiny little case here Tony.

It does matter wether the thermistor is to be mounted on the primary or the secondary.
One should always mount them where the nominal current is the lowest.
This to secure the best (longest) service time for the cirquit.

But otherwise I totally agree with You. Although I always bypass them with a relay after a suitable inrush-time. Again to secure extended service-time.
Click to expand...

the ntc resistors i have seen are on the primary(mains side) of ATX psu's and connects to the mains rectifier....no relays are used to short them out...

though it can be done shorting the ntc out with a relay, i still say using fixed resistors such as that shown in the schematic is the way to go.....
 
TonyTecson

TonyTecson

Member
Joined 2003
nrg2009 said:
So effectively what you are doing is replacing R15-R18 with an NTC (CL30)?

- this has the inrush running through the CL30
- when the relay connects it shorts out the CL30

Is that safe? Is it effective and are there any benefits of replacing R15-R18 with a CL30?

I am trying to decide if I should build this SS-board for an F5Tv2 with 1000VA and 200k uF caps.

Thanks for all your contributions!
Click to expand...

resistor shorted out with a relay is strongly recommended here.....
 
RCruz

RCruz

Member
Joined 2006
Paid Member
Just built the softstart by the book, using:
C9 1uF
C10 1000uF
R15 - 18 180r 11w
G5L 24V relay
D13 24V 1w zener

I am testing the build without load and the relay actuates very fast... half a second.... How can I increase the delay ? (Higher C10 ?)

Or should I expect the circuit to work differently when connected to the power amp psu ?
 
TonyTecson

TonyTecson

Member
Joined 2003
RCruz said:
Just built the softstart by the book, using:
C9 1uF
C10 1000uF
R15 - 18 180r 11w
G5L 24V relay
D13 24V 1w zener

I am testing the build without load and the relay actuates very fast... half a second.... How can I increase the delay ? (Higher C10 ?)

Or should I expect the circuit to work differently when connected to the power amp psu ?
Click to expand...

or change C9 to 0.5ufd...
 
TonyTecson

TonyTecson

Member
Joined 2003
RCruz said:
How low can I go with C9 (I do not have any 0.5uF AC caps).

I simulated the circuit in LT spice and it seems to not be able to reach 24v on the relay if this cap is 100nF...
Click to expand...


you can series connect 2 x 1ufd caps...

remember that C9 is your current limiter, the impedance it present to the line that is....

so that the zener current and the relay coil current added together is your required current after the rectifier....

Ohm's law is pretty much at work here....:D

TBH, i'd rather put a small housekeeping traffo in there, small enough to supply a few mA at 24volts...but it's just me....:D
 
RCruz

RCruz

Member
Joined 2006
Paid Member
Tony said:
TBH, i'd rather put a small housekeeping traffo in there, small enough to supply a few mA at 24volts...but it's just me....:D
Click to expand...

Why would you use a trafo instead ? Is it safer ?
Even with a trafo I would need to experiment a bit in order to reach the desired current and time delay right ?

PS
Do you know the inductance of this type of 24v relay ?

PS: Thank you for the 200nF tip
 
RCruz

RCruz

Member
Joined 2006
Paid Member
Thank you guys.

As my limited parts stock only permited me to use a 0.5uF for C9, I increased C10 to 3300u and the operation seems reasonable... The relay closes after 2,5 sec.

From your comments I believe it is more than enough. Perfect....

PS: My build was too fast because the 24 spec relay I am using, closes once voltage reaches 13v... so I needed to increase delay a bit :)
 
Last edited:
TonyTecson

TonyTecson

Member
Joined 2003
RCruz said:
Why would you use a trafo instead ? Is it safer ?
Even with a trafo I would need to experiment a bit in order to reach the desired current and time delay right ?

PS
Do you know the inductance of this type of 24v relay ?

PS: Thank you for the 200nF tip
Click to expand...

i like the traffo approach because i make them....:D

i do not know the inductance of the relay, but the dc resistance of the relay coil is important to determine the current needed to actuate the relay...

btw, 3 secs is fine if you have a large filter bank...no need to count the seconds up to milisseconds, no need to be that accurate....
 
ByronInPortland

ByronInPortland

Member
Joined 2010
Unsure of what relay to get

The description of the relay in the build guide is a bit sparse: "24V coil relay standard 5 pin". JoJo898's suggestion is not available from my favorite supplier, so I picked one as close as is possible.

Here is what I chose: G2R-1-H-DC24 Omron Electronics | Mouser

Could someone more knowledgeable than me please check this and confirm that this will work well? I have 115VAC (USA) mains.
R15-R18 = 150R
C9 = 0.33uF,
two power supplies with 8 12,000uF caps each.

Thanks in advance for anyone's help.
 
C

coils

Member
Joined 2004
ByronInLawrence said:
The description of the relay in the build guide is a bit sparse: "24V coil relay standard 5 pin". JoJo898's suggestion is not available from my favorite supplier, so I picked one as close as is possible.

Here is what I chose: G2R-1-H-DC24 Omron Electronics | Mouser

Could someone more knowledgeable than me please check this and confirm that this will work well? I have 115VAC (USA) mains.
R15-R18 = 150R
C9 = 0.33uF,
two power supplies with 8 12,000uF caps each.

Thanks in advance for anyone's help.
Click to expand...

dont use that relay, it wont fit in the pcb. Use these

Relays | Power Relays, Over 2 Amps | DigiKey

I used these for my softstart and speaker protection circuit. There really are a lot to choose from, you just need a G5L series relay, and know your desired coil voltage, ac or dc, and single or double throw. I get the highest amp rating I can.
 
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