What modern MOSFETs for class D?

[johansen]

I should have rather entitled the thread "What modern MOSFETs for a power inverter".

yup.

btw, i am also looking for the best mosfets for use in a 4 switch 10 to 100 volt input, 22-65 volt output buck boost converter. i'm thinking 200khz but maybe as low as 60khz. 10 amps minimum per phase, surface mounted fets...

[dannyf]

You just cannot have a rationale discussion with those guys.

Worse yet, they seem to have acquired this sense of entitlement that just because they have a keyboard and internet connection, they can demand that you talk to them. They get really mad when you refuse to talk to them.

No win situation for us.

[SteveyG]

I may have a need to construct a class D amplifier whose duty it will be to deliver a 200Vp-p, continuous-level 20 kHz sine wave at 1.9kW input max.* from a single DC power supply rail of 160V. Given supply constraints it will therefore need to be a bridged design.

A switching frequency of 100 kHz will be sufficient. What model MOSFETs should I be considering? I don't think the voltage is high enough to make IGBTs worthwhile.



* With no worse than 1.5kW delivered to the load.

A 20kHz sine wave output with a 100kHz switching frequency? That seems a little low - what's the reasoning behind only 100kHz switching?

[dannyf]

what's the reasoning behind only 100kHz switching?

The FCC has not approved the license for a 10Mhz 2Kw transmitter yet,

[SeanB]

13.8MHz is a good band to transmit in then, no license required provided you keep the harmonics down.

[NiHaoMike]

What about switch at 20kHz and use resonant tanks to smooth it into a sine wave?

[GK]

What about switch at 20kHz and use resonant tanks to smooth it into a sine wave?

You would need an impractically high Q resonant circuit to handle the grossly non-linear and variable load without severe distortion. Then there is the design issue of coupling to the resonant filter(s) and the attendant problem of amplitude stabilisation.

A “signal” to switching ratio of only 5:1 isn’t really an issue here – adequate “carrier” suppression can be had with more low-pass filter poles. What makes it all impractical is the incompatibility of any practical filter with such a non-linear load.