Speaker protect circuit using mosfets

[xrk971]

I am using these on my SSR’s. Good for 100A, 4mOhm, 80v. PG-TDSON-8. Tiny package but big current.

BSC040N08NS5ATMA1 Infineon Technologies | Mouser

 

[synonymous]

I managed to get a few hundred watts into 4 ohm speakers before they got hot.

You actually got the relay mosfets hot?

 

[nigelwright7557]

You actually got the relay mosfets hot?

Yes but they were taking a lot of amps.

 

[Mark Tillotson]

Any ideas on good SMD MOSFETS for relay usage?
Are there any single unit dual N MOSFET devices?
I would think by now that there would be an integrated device for this exact purpose.

S

My circuit build used DMT10H010LK3-13 SMT MOSFETs, Dpak, 100V, 6.5milliohm. I don't think I found any dual-MOSFETs with good enough ratings, but Dpak are small enough really, you need to get some heat out of the things at higher power levels - a heat-slug is needed.


IIRC the dual devices with heat-slugs were all asymmetric for power conversion use.

 

[synonymous]

What about these??
How is there heat generated with such low Rdson?
SQJQ910EL-T1_GE3 Vishay / Siliconix | Mouser

 

[Mark Tillotson]

What about these??
How is there heat generated with such low Rdson?
SQJQ910EL-T1_GE3 Vishay / Siliconix | Mouser

Well 100W into 4 ohms is 5A rms, which through 8.6 milliohm is 215mW, enough to get small packages distinctly warm - unless you can afford a lot of pcb area as heatsink for the drain tabs.

 

[Mark Tillotson]

And I just had another search for possible MOSFETs - over 100V seems to command a non-trivial price premium it seems, this FDMS4D0N12C was a notable performer at 120V and 3.3 milliohm, though expensive: https://uk.farnell.com/on-semiconductor/fdms4d0n12c/mosfet-n-ch-120v-114a-pqfn/dp/2895643RL


For dual MOSFETs I found 100V 13mOhm: FDMS8090, and 80V 7mOhm: NVMFD6H840NL - seem to be more symmetric dual MOSFETs than when I last looked

 

[Kuba_eM]

Accuphase uses TK160F10N1 transistors for protection in many of its new designs, RDS(ON) = 2.0 mΩ; VDS = 100 V.

 

[synonymous]

Accuphase uses TK160F10N1 transistors for protection in many of its new designs, RDS(ON) = 2.0 mΩ; VDS = 100 V.

Thanks Kuba, looks like a good device

 

[Kuba_eM]

Another small device used by Accu: TPH1R306P, RDS(ON) = 1 or 0.96 mΩ !!! (dep. on version PL or P1), but limited VDS = 60V.

 

[npdot]

Greetings. Sorry for jumping on this thread so late in the game. It's because I just had a relay-based speaker protection circuit fail in one of my diy amps (in use for years) and I am thinking about switching to a SSR. So I've been looking at using the VOM1271 with TK72E12N1's mentioned by Bonsai and others.

Any suggestions about the sensing part of the solution such as turn on delay and DC detection? Tips would be appreciated.

 

[Michael Bean]

Here is the delay relay circuit I employ:



And I've adapted Fig 1 (here: Loudspeaker Protection and Muting) for DC detection, Doug Self also published a version that is popular.

Mike

 

[npdot]

Mike, Thanks for taking time to respond.

The current circuit is Rod Elliot's P33 so I've considered using the P198 MOSFET relays as he suggests, but don't have room for 4 additional boards. And . . . something new will be more fun. BTW, the failure was my bad. I shorted something, not sure what, to 60VDC and took out a perfectly good DMM probe at the same time.

I'll check out Mr. Self's solution as well as your's.

Thanks again,
Neel

 

[synonymous]

My setup uses the Rpi but you could modify it to your needs...