Why are there no digital isolators with integrated gate drivers?

[treez]

Hello,
We are doing a 7Kw full bridge LLC converter , with 4 primary fets and 4 secondary diodes. The secondary diodes will be synchronous.
The need for solid gates drive means we will implement all 8 gate drives with two multiple output flybacks (one for the 2 primary upper switches and one for the 2 secondary upper switches).
Each gate drive supply flyback will have two outputs for the two top fets, the two bottom fets will be supplied from the “Housekeeping” rails available.
The gate drive signals will be coupled to the fet gate drivers via digital isolators.
The synchronous fets will be driven via digital isolators from the primary side, and therefore, to replicate the delays, all fets will be driven through the same digital isolators.
Do you know if its possible to buy digital isolators that include gate drivers in them? We cant find any in digikey etc. Infineon are doing it with the 1EDI series but these only isolate to 1200v, we need the full 3.5kv as per mains isolation
Ltspice Sim attached of triple output flyback

 

[FvM]

Infineon are doing it with the 1EDI series but these only isolate to 1200v, we need the full 3.5kv as per mains isolation.

Sounds like you are confusing working voltage and test voltage of opto couplers/digital isolators.

 

[treez]

thanks, the test voltage isn't stated, so I presume it doesn't make mains standards (3.5kv)?
https://www.infineon.com/dgdl/Infin...N.pdf?fileId=5546d4614755559a014790299add6112

 

[rikkitikkitavi]

thanks, the test voltage isn't stated, so I presume it doesn't make mains standards (3.5kv)?
https://www.infineon.com/dgdl/Infin...N.pdf?fileId=5546d4614755559a014790299add6112

Isnt that a nobrainer? What insulation and creepage distance do you achieve with a SO-8 chip?

 

[FvM]

Isnt that a nobrainer? What insulation and creepage distance do you achieve with a SO-8 chip?

1EDI family in compact SO8 package is in fact intended for 1200 V working voltage with basic rather than reinforced isolation, not meeting the 3750/5000 V test voltage requirements. Aparently there's no Infineon single channel driver offered with reinforced isolation, you have to refer e.g. to Avagotech drivers.

 

[Patr!ck]

Did you check the available parts from Analog Devices? Their isolated gate drivers might offer a solution.

 

[Velkarn]

take a look at optoisolated gate drivers from Avago

 

[treez]

Isnt that a nobrainer? What insulation and creepage distance do you achieve with a SO-8 chip?

I've definitely seen SO8 optocouplers straddled across an isolation barrier of an offline SMPS, many times. This is SMPS from the biggest companies around.

 

[FvM]

I've definitely seen SO8 optocouplers straddled across an isolation barrier of an offline SMPS, many times. This is SMPS from the biggest companies around.

Can work for 230V mains with reinforced isolation, depending on the applied safety standards. There are some nice compilations of relevant safety regulations for optocouplers:
Avagotech:
NVE: https://www.nve.com/Downloads/ab2.pdf
Vishay: https://www.vishay.com/docs/83743/83743.pdf