design gate drive power mosfet in class d

[yanuarbob5150]

design gate driver mosfet

i design a class d amplifier to result >80W rms power output i use power mosfet to result it. Now, i have a problem :
1. my PWM source is reference to ground in this case i must use the PWM source reference to source of mosfet, so i must isolated that ground. i use the optoisolator but frequency that i need isn't reach.
In configuration power mosfet i use halfbridge configuration and switching frequency 400kHz.
i don't have any idea how to do it. Can some suggestion for me or design simple circuit to do that??????????????????????????????

[croccodillo]

Cheapest solution:
You can use an IR2113 dual driver, with such a chip you can drive your half-bridge.
Very cheap, easily available chips: no needs for an auxiliary floating supply. You however do not have a galvanic insulation with your driving logic (but usually you don't need it).

Most flexible solution:
You can use a digital optocoupler driving a low side driver, like the 6N137 (10Mbit) optocoupler.
This optocoupler can drive any gate driver you want, like IR4420, IXDD414, etc, giving you the maximum flexibility and degree of adaption to your mosfets.
Of course you need two separate, floating power supplies (5V for optocoupler and 15V for the gate driver).

Most elegant solution:
If you want something more elegant and sofisticated, why not to use a HCPL3120, a digital optocoupler with an integrated gate driver?
Of course you need a separate, floating power supplies for the driver, and you cannot drive really big mosfet, due to the maximum peak current limit (2.5A).

Most difficult solution:
Or, again, what about a gate transformer?
You can find some useful information HERE.
To build a really good gate transformer is not so easy, so expect to fail and try for a long time.


Please also give a look at IXYS site (http://www.ixyspower.com/), they do have wonderful application notes explaining how to drive your mosfet in the best way.
Let's start with THIS , then give a look at
THIS as also THIS

[croccodillo]

By the way: is it possible to have a schematic of your amplifier, so I can give you more precise suggestion?

Ciao,
Giovanni

[croccodillo]

Just for your information: I'm currently developing, at work, a SMPS with an output power of about 1.5KW (yes, 1500W), an output voltage of about 4.5Kv (4500V), quasi resonant half bridge: the two IGBTs (IKW75N60T) are driven by a single IR2113 chip.