Soft as a Feather Pillow (SFP) SSR Soft Start Circuit GB

[ferret]

Turns out I'll have to wait till the end of the month. Other stuff has cropped up and takes priority. Plenty of stuff to keep me busy in any case. This is really a great design XRK and co. Many thanks. Fortunately all components are readily available locally, if a little more dear, but then C&E would hit me with taxes in any case.

Kevin

 

[astromo]

Just a heads up for members considering buying these pcb's from X, you might have to split your component order over both Mouser and Digikey, as Mouser has no stock of U2 and Digikey has no stock of U4 currently.

For U2, RS might work. Not sure if this part of an acceptable substitution:
TLP3906(E(O Toshiba CAD model download | Octopart

RS do some attractive shopping rates last time I checked.

 

[xrk971]

That’s the same TLP3906. Should work fine

 

[gary s]

Looking at the RS link, it seems they have a minimum purchase of 10 units.

Ordered mine from Digikey this morning and received a shipping email at lunchtime from them - great service and free delivery by UPS.

RS have free delivery at the moment as well.

 

[xrk971]

That’s nice to get free delivery to Oz. They don’t give folks in the US free delivery.

 

[gary s]

Yes X, both Mouser and Digikey offer free guaranteed delivery from their US warehouses via Fedex or UPS as long as the order totals more than $50.00 USD - which is easy. So I always make sure the value is above the limit.

Normal delivery to my door in rural NSW is 4 days by both, that is very good service indeed.

RS Online here delivers Australia wide for free no matter what the order total is, but that changes from time to time.

 

[xrk971]

The new v2.3 SFP PCB's just arrived. These have the new pads for the three NTC's.

 

[bigaudioscotto]

Looks nice X.

 

[xrk971]

All the SFP’s ordered have been sent out. I spent about 5 hrs yesterday packaging the SFP’s, RTR SSR’s, and Hakuin Yarra preamps for shipment. Man, that never gets easier.

 

[bigaudioscotto]

X thank you for all you do.
Very much appreciated.

 

[pinnocchio]

Hi X,

Since you're using SSR on the softstart, would they work like the Crydom zero crossing SSR relay? I've been having issues with the Crydom zero crossing, they caused many brands of Toroid to hum terribly with these relays and I had to remove them all from my builds.

Hopefully it is not the case with this design.

Thanks
Do

 

[xrk971]

It is not a zero crossing relay - it is similar in topology to the SSR's used on the SSR DC protection relays that I have. It acts as a very low resistance piece of wire when it is on. It doesn't modulate or add distortion to the AC sinewave. Neither I nor Vunce have experienced any issue with increased hum on the trafos when using this.

 

[pinnocchio]

Ok thanks!

 

[jhofland]

@pinnocchio,
I believe the Crydom solid state relays are SCR based so they switch on/off every half cycle. This design uses a pair of high voltage high current MOSFETs so, as X noted, it looks like a fraction of an ohm when conducting.

 

[pinnocchio]

ok, that's good news!

One thing that would be very interesting to integrate to the circuit is a momentary switch driver with LED or dual color LED support. This is very useful for integrating a front panel switch without having to run AC there. Just a thought..

Thanks
Do

 

[1883]

Green Toroid Inductor Core

What are the specs of the Toroid Inductor core and/or part number?
Thank You.

 

[xrk971]

What toroid are you talking about?

You mean this?

That’s not part of the SFP circuit. I just wrap my mains from the wall through that 2-3 turns in opposite directions for the line and the neutral as a common mode filter choke. These are eBay/Ali-Express circa 25mm ferrite donuts. No spec other than diameter. Similar to this:

https://www.diyaudio.com/forums/att...soft-start-circuit-gb-sfp-v2-1-gh-testing-jpg

Anyhow, it’s not needed for the SFP to work. I just use it to reduce RFI from the walls reaching my amp.

 

[1883]

Thank you

 

[abanico]

Works great , much thanks !

 

[xrk971]

Nice! You don’t need heatsinks on the MOSFETs. Make sure the sinks are not electrically live as that is mains voltage. I actually cover mine with shrink tube.