2 kwts discreet class d need help

[stewin]

hi guys i have constructed and have been using this ucd amp based for quite some time . i wanted to juice it up to use multiple output like 4 pairs of irfp250 / ifrp260 or 3pairs of irf540 like in iraud 9amp with 250and 260 i wanted to do +/-72vlts at 4 to 2 ohms i dont have ociloscope or don't know how to go about one. much participation will be appreciated. stewin

[stewin]

i am using +/- 45vlts cause of irf540 voltage ratings.
i had written +/- 80vlts on the schema hoping to get my hands on a cool fet like irfb4227

[norazmi]

hmmm, to go with high power, this circuit is too complicated. u can use simple one with ir2110 and can go such as power by using right mosfet. or drive it as fullbridge. btw this circuit is discrete, did u build it stewin?

[stewin]

yes i have built it it works. and has not been disturbing me with noise issues. i like discreet because when it fails or burns i only replace one or two 2n5404 near the outputs and the outputs them selves unlike using ir2110 . i have to replace the output everytime plus the expensive ir2110 ic every time something goes wrong.

[norazmi]

agreed with IR2110 is expensive, discrete just need more work to do but you can save $$, i have few schema with discrete component and i do simu with LTspice seems work good. I think i will build it when i have time here i leave schema maybe anyone interested.

[norazmi]

hi stewin,

here is the result with LTspice, i do modification from original schematic because original one have 1.3% thd and offset is 98mvdc. so this is result for the modified one and i`ve free time today i`ll make one board for it, i wanna test it how this amp working and how stable it is.

Tested mosfet IRFP250N, with +-/- 48 vdc, output voltage +/- 32 vac 8 ampere. 4 ohm load. Dc offset only 0.004vdc.
Starting source stepping with srcstepmethod=0
Source Step = 3.0303%
Source Step = 9.84848%
Source Step = 17.4242%
Source Step = 25%
Source Step = 32.5758%
Source Step = 40.1515%
vernier = 0.375
Source Step = 50.7576%
Source Step = 62.1212%
Source Step = 73.4848%
Source Step = 84.8485%
Source Step = 96.2121%
vernier = 0.5625
Source stepping succeeded in finding the operating point.

Fourier components of V(out)
DC component:0.004799

Harmonic Frequency Fourier Normalized Phase Normalized
Number [Hz] Component Component [degree] Phase [deg]
1 1.000e+02 3.135e+01 1.000e+00 -123.45° 0.00°
2 2.000e+02 3.292e-03 1.050e-04 56.05° 179.50°
3 3.000e+02 3.236e-02 1.032e-03 -166.58° -43.13°
4 4.000e+02 2.101e-03 6.702e-05 148.97° 272.42°
5 5.000e+02 2.386e-02 7.612e-04 -61.54° 61.92°
6 6.000e+02 2.849e-04 9.087e-06 76.29° 199.74°
7 7.000e+02 1.236e-02 3.944e-04 47.00° 170.45°
8 8.000e+02 4.671e-04 1.490e-05 10.87° 134.33°
9 9.000e+02 8.908e-03 2.841e-04 157.27° 280.72°
Total Harmonic Distortion: 0.137746%


Fourier components of V(in)
DC component:-3.3813e-011

Harmonic Frequency Fourier Normalized Phase Normalized
Number [Hz] Component Component [degree] Phase [deg]
1 1.000e+02 2.000e+00 1.000e+00 -0.00° 0.00°
2 2.000e+02 1.188e-10 5.939e-11 -171.43° -171.43°
3 3.000e+02 2.156e-10 1.078e-10 163.34° 163.34°
4 4.000e+02 6.074e-11 3.037e-11 78.61° 78.61°
5 5.000e+02 1.227e-10 6.136e-11 -2.60° -2.60°
6 6.000e+02 5.527e-11 2.763e-11 113.55° 113.55°
7 7.000e+02 1.044e-10 5.218e-11 51.52° 51.52°
8 8.000e+02 2.053e-10 1.026e-10 -33.31° -33.31°
9 9.000e+02 1.105e-10 5.525e-11 -161.60° -161.60°
Total Harmonic Distortion: 0.000000%



Date: Fri Feb 24 12:19:12 2012
Total elapsed time: 1037.290 seconds.

tnom = 27
temp = 27
method = modified trap
totiter = 17672589
traniter = 17670226
tranpoints = 4732823
accept = 3348150
rejected = 1384673
matrix size = 96
fillins = 202
solver = Normal
Matrix Compiler1: 23.3 KB object code size 9.0/5.9/[2.5]
Matrix Compiler2: off [3.0]/3.6/16.1

[stewin]

wow thanks nozrami for the help . are you sure your circuit can drive irfp250 without heating . with my experience with discreet ucd R1 in your schematic needs to be of a high value or the output will heat like crazy. why haven't you include the op-amp preamp section is the gain sufficient enough? thanks for the simulation man GOD almighty bless you big time.

[stewin]

BTW nozrami does driving the irfp250 with small bjts like in my schema above q22 ,q14 ,q6 , q3 help in any way in terms of power output and t.h.d?

[norazmi]

yes R1 need to set high, its original schema, btw Stewin, im trying to build this one but not finish yet. For your schema, i`ll do some research let me see what we can do.

[norazmi]

Oo, as i can see ur schema is more better and include op -amp, i`ll try simulate it, and tell u the result