class d amplifier current output

[franticEB]

Hi,
i'm designing a class d amplifier with current feedback as in figure below:




with the following features:
Vbus=50V
Iout programmable from 100mA to 1Arms
Vout=35Vrms max

When the load overcomes the programmed current (i.e. 1Arms) the amplifier saturates and the sinusoidal output becomes a square wave output. For example i want to transmit on 1200 ohm a 35Vrms sinusoidal voltage even though the current feedback is not locked.

So my purpose is to mantain a maximum allowable voltage on the output.

Is it possible to obtain that feature? A second feedback is needed?

Could you help me?

Thanks.

 

[BradtheRad]

To change output amplitude, change length of PWM pulses by some percentage.

To do that, change amplitude of your control sawtooth, or your control sinewave.

The methods might involve altering gain, or an oscillator's supply voltage, or interaction between an led and light-dependent resistor, etc. There is no obvious way, but several ways to choose from, and each involves some effort.