Class d control methods: UcD / LF

[bimbla]

The way in which analogspiceman has employed current sensing is so elegant and opens up so many other possibilities.

I understand now from Pafi and Kartino that here is is employed to initiate self oscillations.

In another thread where analogspiceman explained Leapfrog control, he also mentioned 'inherent short-circuit protection' that made me jump to current drive because current drive also has inherent short circuit protection.

But now I understand (thanks to Pafi and Kartino) that its purpose is different here.

 

[Pafi]

As i know,from analogspiceman model it sense resistive current from supply rails to get triangle to get self oscillation and voltage output to get error feedback of sonic. CMIIW.

The sum of the inflowing currents to the amp from power rails equals to the current flowing on output inductor. Measuring this is the goal of this double current mirror solution. The essential reason for inductor current feedback is ensuring control loop stability above cut frequency of output filter where phase shift of voltage signal increases rapidly. However in this circuit a mixed strategy is implemented, the phase boost of ucd is inherited also.

For self oscillation not triangle but almost sine wave is needed.

 

[Pafi]

Short circuit protection is not really achieved, only for relatively small input signal. At nominal full drive Ioutshort=Vpsu/1.5ohm. But if you increase input signal further, the output current will also increased. It is linear, no absolute limit.