New ClassD project Starting from 0

[DjLeco]

Hi, I decided to start my new ClassD project.
It will work for bass only,20Hz-200Hz

Oscillator with 4 Mhz ceramic resonator, MC14060BCP oscillator and divider, on pin 5 exactly 100Khz.

Here is some pictures of trianglegen output, measured wth a 20 Mhz scope

On pin 5 output:




On trianglegen output:



Is this correct?

[DjLeco]

Being enthusiasmed, I forgot to mount the operational on soket

Now, on output, the signal is like this:



The schematic is that:




Any opinions?
Suggestions?

[wg_ski]

Well, so far so good... but generating a triangle wave is straightforward. What you'll see around here is mostly kits and one-chip wonder solutions because it can get hairy further down the rest of the chain. What will be really interesting is what you come up with for a dead-time generator, and how you couple the gate driver circuits from the low-level PWM signal into the bank of hexfets.

I'm looking at class D architectures for bass as well. Starting with the output H-bridge, with optically-isolated gate drive (like Crown CE4000, but I'm not doing BCA). Once I nail down how fast this thing can reliably switch, that will determine what kind of dead time and carrier frequency it can handle.

[DjLeco]

Excuse me, at output triangle gen and oscillator, is 125Khz, not 100, how I wrote and put on schematic(I was thinking at something else ...)

On LM361 outputs, I obtained those signals:

[wg_ski]

100kHz... 125kHz... what's the difference? I just figured your scope was out of calibration.....

[DjLeco]

Originally posted by wg_ski
100kHz... 125kHz... what's the difference? I just figured your scope was out of calibration.....

With 4 Mhz Crystal, you will obtain 125 Khz divided, not 100 Khz, my blame for thinking at other things whan I wrote...

Possible the scope being decalibrate...
I will check.

[DjLeco]

I'm back, it's a full bridge configuration, it works !

For 125 Khz switching, how many uH must have the output coils ?

I tried with 80uH for low side, also for Hi side too, and everything is COLD.

No coils warming up and no mosfets too, in IDLE, they rest around 35-40 celsius degrees maximum, and around 55 degrees in load, delivering 33Volts RMS on 4 ohms load, with 56 volts supply.

I will come later with some screens.

[DjLeco]

Some pictures and movies.
It works perfectly at 125Khz, I have an output , only 130 milivolts residual of 125Khz switching freq.

Supplied at +/- 30Vcc, it gives around 350Watts on 4 ohm, with more than 90% randament.
All is in studying stage, following improvements.
Is done with P and N mosfets, on output, next modification is to use only N mosfets.

Any sugestions?

Triunghi:


(links removed by mod due to their inappropriate content.)

[DjLeco]

Also, first movie, I put again, because first link was bad...

(link removed by mod for inappropriate content)

Excuse support of the site(litlle nasty),and download it.

[pieter t]

+/- 30 volts power supply??
That should give no more than about 20 V RMS, which is 100 watts / 4 0hm.
Am I missing something here?

Pieter