new design?

star882 · 4th November 2008, 05:11 PM

http://ece-www.colorado.edu/~rwe/papers/Powercon5.pdf
Has anyone actually tried to build an amplifier based on the design in that article?

Eva · 4th November 2008, 11:14 PM

Nice paper from 1978. I wonder what have we been doing for the past 30 years, it does not look that old at all.

The main problem with this topology is its (double) boost nature that leads to poor linearity and difficult control (see page 11). Increased voltage stress on the switches for a given output power is another drawback (with respect to buck).

Current ripple is not such a bad thing, for example, post-filter feedback self-oscillating amplifiers (my favourite) rely its operation completely on it.

Gyula · 5th November 2008, 11:17 AM

Hi Eva!

You wrote:

Quote:

Current ripple is not such a bad thing

What is your opinion about my former discussion at
Pulse Width Modulation Circuits ?
I assume the triangle comparation caused sampling does transponation of the sidebands around carrier and its harmonics to the baseband (around f=0). Therefore it causes inherent distortion with feedback. Are you agree with it?

Gyula

lumanauw · 5th November 2008, 12:27 PM

In Cuk converter, energy flow is bidirectional, it can absorb power too.

Workhorse · 5th November 2008, 12:55 PM

I prefer grounded bridge Class-BD.

darkfenriz · 8th November 2008, 08:04 AM

This is very interesting, but does not really proove that Cuk converter is that better than half bridge converter (called "buck" in the article).
Still there is the problem of high value capacitors stressed to high AC current ripple as in Cuk power supply.

Adam

P.S. Also in my opinion the authors really overestimate the rule of filtering 2 decades below swithing frequency. The amp with such low LC corner frequency will not be able to deliver high power at short high frequency transients. Another words the power at 20kHz will be very low.
Correct me if I am wrong.

Eva · 8th November 2008, 10:55 AM

When output filter is made to resonte well below the desired high frequency limit, the result is both limited slew rate and maximum output above resonance. This is acceptable but only to some extent, it's not ok for some types of music.

darkfenriz · 8th November 2008, 11:25 AM

See figure 29 in the article.
They've shown 630uH/10uF
If my calculations are OK than it is 2nd order filter (-40db/dec) with border frequency of 2kHz, which results in 10 000 times power reduction at 20kHz.

Cuk is definitely a clever engineer but does not have this "audio touch"

4th November 2008, 05:11 PM	#1
star882 diyAudio Member Join Date: Mar 2007	new design? http://ece-www.colorado.edu/~rwe/papers/Powercon5.pdf Has anyone actually tried to build an amplifier based on the design in that article? __________________ "Fully on MOSFET = closed switch, Fully off MOSFET = open switch, Half on MOSFET = poor imitation of Tiffany Yep." - also applies to IGBTs!

4th November 2008, 11:14 PM	#2
Eva diyAudio Member Join Date: Oct 2003 Location: Near the sea	Nice paper from 1978. I wonder what have we been doing for the past 30 years, it does not look that old at all. The main problem with this topology is its (double) boost nature that leads to poor linearity and difficult control (see page 11). Increased voltage stress on the switches for a given output power is another drawback (with respect to buck). Current ripple is not such a bad thing, for example, post-filter feedback self-oscillating amplifiers (my favourite) rely its operation completely on it. __________________ I use to feel like the small child in The Emperor's New Clothes tale

5th November 2008, 12:55 PM	#5
Workhorse diyAudio Member Join Date: Dec 2004	I prefer grounded bridge Class-BD. __________________ It's a fruitless endeavor to try and educate a fool that rejoices in ignorance

8th November 2008, 10:55 AM	#7
Eva diyAudio Member Join Date: Oct 2003 Location: Near the sea	When output filter is made to resonte well below the desired high frequency limit, the result is both limited slew rate and maximum output above resonance. This is acceptable but only to some extent, it's not ok for some types of music. __________________ I use to feel like the small child in The Emperor's New Clothes tale

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5th November 2008, 12:27 PM	#4
lumanauw diyAudio Moderator Emeritus Join Date: Oct 2002 Location: Bandung	In Cuk converter, energy flow is bidirectional, it can absorb power too.

8th November 2008, 08:04 AM	#6
darkfenriz diyAudio Member Join Date: Jun 2004 Location: Warsaw	This is very interesting, but does not really proove that Cuk converter is that better than half bridge converter (called "buck" in the article). Still there is the problem of high value capacitors stressed to high AC current ripple as in Cuk power supply. Adam P.S. Also in my opinion the authors really overestimate the rule of filtering 2 decades below swithing frequency. The amp with such low LC corner frequency will not be able to deliver high power at short high frequency transients. Another words the power at 20kHz will be very low. Correct me if I am wrong.

8th November 2008, 11:25 AM	#8
darkfenriz diyAudio Member Join Date: Jun 2004 Location: Warsaw	See figure 29 in the article. They've shown 630uH/10uF If my calculations are OK than it is 2nd order filter (-40db/dec) with border frequency of 2kHz, which results in 10 000 times power reduction at 20kHz. Cuk is definitely a clever engineer but does not have this "audio touch"

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