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Multilevel PWM Generation for Class D Amplifier

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I need to generate a 3 level PWM for a Class D amplifier in full-bridge.
I've been searching about this for some time but I haven't been able to find any usefull circuit or IC to do this.
Can anyone help me with this?


Operation is not too different from a sine-PWM inverter. You start with a sawtooth wave at the input of an op amp. At the other input you apply audio. The modulating effect creates pulses of varying width.

You need two PWM generators. One applies current through the load in one direction, one applies current in the other direction.

This is a simplified simulation. Two op amps perform all roles: (a) control circuit and (b) full H-bridge.

A real circuit would have the op amps operating transistors or mosfets, of course.

Notice an op amp output provides a path to ground, during the time that op amp is idle. The same thing must be achieved in a real H-bridge.

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