Is class D amplifer? Yamaha Stagepas diagram

[harrimansat]

Hi folks,
Can anybody help me with this schematic, Yamaha says that is a D class power amplifier, is a Stagepas 500 250W+250W RMS power amplifier 4 ohms, (+46V -46V).
With only two 2SK3607 N 17amp mofests (70W mas power disipation) how it works???




Thanks
Regards

[Ammar]

https://en.wikipedia.org/wiki/Class-D_amplifier

[ovnr]

Yes, that's a class D amplifier. As for dissipation: Remember, the maximum dissipation rating refers to how much power is dissipated in the transistor - not how much flows through! And for a proper class D amp, the max dissipation figure is quite irrelevant for the maximum power output.

[dannyf]

Yes, it is class d. The first stage is a VI converter. The 2nd stage is a current transmission mechanism.

The output is filtered pmw.

Basically a power comparator. Aka ucd style.

[diyaudio]

Hi folks,
Can anybody help me with this schematic, Yamaha says that is a D class power amplifier, is a Stagepas 500 250W+250W RMS power amplifier 4 ohms, (+46V -46V).
With only two 2SK3607 N 17amp mofests (70W mas power disipation) how it works???




Thanks
Regards

This is a very good commercial amplifier to clone and diy its based on the Philips UCD self oscillating patent.

A)  Forms a simple differential output stage, the output will have a differential output swing which is identical to an op-amp with a complementary output stage. (you could replace A with a high speed op-amp with complementary outputs )
B) A simple DTR fast turn off mosfet driver, this method is a cost effective technique to drive mosfets
by taming them for slower propagation turn on (to avoid turn on mosfet cross-conductance) yet allows fast  turn-off response, turnoff is essentially grounding the gate almost instantaneously. 
C) Switching pair of N-channels, these will form a switching stage switching at the rate of least twice the audio frequency (using Nyquist Theorem)  then feeding a LC stage used to demodulate the signal to audio.       
D) Forms are simple asymmetrical current sense trip for both +/- rails, if the amplifier is driving heaving speaker loads at high output levels it will signal a trip signal and shut the amplifier down.     
E) The most complex part, a pole/zero feedback system is used to create a phase/lag with compensation, its used to create feedback loop and get the amplifier to oscillate, the carrier residual  used as a reference to create a PWM signal based on the difference between the two signals, note this system uses post feedback to obtain the carrier.

   
   

[harrimansat]

Thank you diyaudio, I really appreciate your answer.

Philips demostration board patent:

http://www.nxp.com/documents/user_manual/UM10155.pdf