PLaying with ClassD again

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Hi.

Here's a small peak at my latest classD-fumblings.

I concentrated on the output-stage at first. It's build around a IR2110 and two FQB19n20L.

Here's a few pics of the output-waveforms before the filter. First a 115Vpp square and the rising/faling edge. Rise/fall-time is approx. 35nS (10%->90% of voltage-range). Looks promising.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.


Next on the to-do is the modulator-scheme. Most likely selvf-osc in some form. Any ideas? What's your favorite-scheme of the day?

Please click this link to see more info: http://kofoedmejer.squarespace.com/classd-amplifier/

Regards TroelsM
 
@Luka

Output filter was connected at the time, but the plot shows the pre-filter waveform.

The cap on the floating supply is not very big, but I will change it later. Right now its not the biggest problem.

Thanks for the help. Re-visit the tread later to see more.

Regards
 
I'm trying NOT to say that i destroyed the lowers-side Mosfet and IR2110 driver when GND at my scope-probe for a brief moment touched something (lowerside-gate perhaps?).

That's a bit embarrassing... Oh well, - it's probably not the last time I'll do that :)

The amp is re-build with better cooling and working again, so after all it was only a minor setback.

Regards TroelsM
 
Don't worry, this has happened to all us at least once or twice.

Once I blew the ground lead of a probe when I inadvertedly did a short between +415V DC and GND through the other probe in a board having a 2250uF capacitor bank. Later the alligator clip of the ground lead of another probe ended up perfectly bonded to the leg of a 2W resistor, it seems that temperature due to the short circuit was high enough to melt both metals :D
 
Hi Eva

"once or twice".. ? I've done that more times than I want to admit :)

Well now I would like to measure the currents in the output-stage and therefore I'll try to construct at simple current-probe from a two-part ferrite-core, some wire, a few passive components and a bit of coax with a bnc-plug.

Any ideas? I won't go for high accuracy, but just something that will let me see the currents. I'm guessing that linearity is more important than absolute accuracy. For switch-mode it would be nice to be able to measure from 100Khz to 100Mhz.

Regards TroelsM
 
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