Simple Class D amplifier power supply for guitar?

[Flyback]

Hello,
Can I do an offline (230VAC) SMPS for Class D amplifier supply with a simple "burst mode" control type, Two Transistor Forward SMPS?
ie, Vout divided down and put into a comparator.....when vout goes below regulation, the comparator trips and sends the tripped signal through a digital isolator to the primary side controller, which simply turns on the gate driver with a fixed duty cycle......as soon as the vout goes below the regulation value, the comparator again trips and the primary side controller simply turns the switching FET(s) off.......and then repeat.
Whats wrong with this?
If its EMC , then I can have a "soft start" so that every time the switching FET is turned on for a "burst", the duty cycle is steadily increased, over say 10 switching cycles, to the maximum duty cycle.
Will this be OK?
I wouldn't have PFC simply because class D amplifiers , on average, never operate above 1/8th of their maximum power.

 

[alec_t]

Perhaps burst mode would give unacceptable ripple on the resultant DC supply? Won't that feed through to the audio, even in Class D?

 

[Flyback]

I don't think so....after all, most class d guitar amps are supplied by horrible 50hz trafo psu's...and they ripple up and down like mad at 100Hz.

The comparator and digital isolator in the feedback loop ensures that what ripple there is is bounded to an acceptable amount...depending on the size of the output cap and the amount of hysteresis set on the trip comparator.

I don't think amplifiers are affected by 400mV of ripple on a 50V supply...no matter what frequency it is at.

 

[alec_t]

.... besides, guitarists love distortion/fuzz .

 

[Flyback]

This report (attached) sets out the reasoning for the selection of Burst Mode Control for a 320W Two Transistor Forward converter SMPS for supplying a Full Bridge, Class D guitar amplifier.
(Output of SMPS is 80V & 4A)
Do you agree that Burst Mode control for this power level & application actually makes sense, due to the "pulsey" nature of the load, and the load's very low average power?
Please also find attached the LTspice simulation of the 320W Burst Mode SMPS.

 

[Flyback]

By the way audiophiles may enjoy the report in the above post about a cheap and effective way to do a good smps to supply a class d guitar amplifier.
If you read it, then please give your opinion?