TD class amplifier using a switching power amp in order to get more efficient amp
OK, I think I see what they are doing.
It is like class H described on this page:
class G and H amplifiers
The power dissipated in the output stage is determined by the current through the output stage, and the voltage across the output devices.
A class D amplifier reduces the product of voltage and current by having the output devices either low impedance, fully on, so the voltage is low, or high impedance/off so the current is low, but the full power supply voltage is across the device.
Class H or TD gets the reduced power dissipation by reducing the power supply voltage when the signal amplitude is low, and raising the power supply voltage as the signal increases, so that the output device always has say 5V across it no matter the output voltage or current.
If the power supply voltage is changed using an analog regulator design, then the entire amplifier dissipation is still high, because now the power supply is dissipating power when the output stage is not.
Lab Gruppen just took the obvious approach of using a variable regulated SMPS for the power supply in a class H design to reduce the total power dissipation, then tasked their marketing department with coming up with something clever to call it.