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Registered Member #2922
Joined: Sun Jun 13 2010, 12:08AM
Location:
Posts: 226
I however also sum my own integrated ramp back onto the feedback
First order delta modulator :>
But, for your integrator/acumulator amplifier you need a simetrical -5v to 5v supply, no? I'm using TL3116 as comparator and TL072 as amplifiers/integrators.
I have already tryed to sum a small derivation term at the feedback, it help to get a better ripple/transient response. It acts iqual to the feed-forword capacitor, bacause this capacitor can be see as a derivator.
Now I need to make a good inductor hehe. I need to buy a inductimetter, mesure the indutance using ressonance sucks.
Registered Member #2292
Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795
Gregory wrote ...
I however also sum my own integrated ramp back onto the feedback
First order delta modulator :>
But, for your integrator/acumulator amplifier you need a simetrical -5v to 5v supply, no? I'm using TL3116 as comparator and TL072 as amplifiers/integrators.
I have already tryed to sum a small derivation term at the feedback, it help to get a better ripple/transient response. It acts iqual to the feed-forword capacitor, bacause this capacitor can be see as a derivator.
Now I need to make a good inductor hehe. I need to buy a inductimetter, mesure the indutance using ressonance sucks.
You don't need a separate opamp or a split +5 -5 supply. I use a single TL3116 and a single +5V supply.
I actually use an RC network to generate the ramp that is summed back on the feedback ramp. The trick is to have the feedback ramp be larger in amplitude that the ripple of the output so that the comparator only looks at the RC ramp and not the ripple from the output.
Registered Member #2922
Joined: Sun Jun 13 2010, 12:08AM
Location:
Posts: 226
You don't need a separate opamp or a split +5 -5 supply. I use a single TL3116 and a single +5V supply.
If you are using only a single comparator I think that he is the quantizer (feedback - reference + histeresy). How are you adding the integrated ramp with not other amp? oO You need to make the integration.
Registered Member #2919
Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652
Goodchild wrote ...
teravolt wrote ...
I don't know if any body is interested but I found this IC that I stumbled on and thought that this may be pertinent
teravolt that is an awesome little chip, it dose bang bang control a little bit differently than normal seems like it samples rather than running all the time. From my initial glance at the datasheet it looks like all timing is done internally rather than using external integration, as I said earlier this is a wonderful way to improve noise and load immunity on the switching times.
I may have to give one of these a try some time in the future.
Sadly that chip seems a tad slow; it can't do over 10 KHz, which is borderline for a QCW modulator and still audible
Gregory wrote ...
You don't need a separate opamp or a split +5 -5 supply. I use a single TL3116 and a single +5V supply.
If you are using only a single comparator I think that he is the quantizer (feedback - reference + histeresy). How are you adding the integrated ramp with not other amp? oO You need to make the integration.
Registered Member #2922
Joined: Sun Jun 13 2010, 12:08AM
Location:
Posts: 226
ohhhhh. Now I understand.. He is using the RC to integrate/acumulate. I was think that he was using the RC to generate the reference ramp with some PWM from a uC. Now all make sense.
Registered Member #2292
Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795
Gregory wrote ...
ohhhhh. Now I understand.. He is using the RC to integrate/acumulate. I was think that he was using the RC to generate the reference ramp with some PWM from a uC. Now all make sense.
Registered Member #195
Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111
hi Dr. Isotop, when I looked at the specs I think you are right that 10Khz sample rate is a bit slow. How ever for the bang bang control you probably don't need much more resolution for a ramp wave form of 5 to 20mS to filter. using a mbed for delta modulation is over kill you could probly use a adruino. cirtanly a microcontroler combined with hardware would be a awsum way to controle feedback and reduce parts count. I will probly end up using all hardware at this point for feedback.
Registered Member #2919
Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652
teravolt wrote ...
hi Dr. Isotop, when I looked at the specs I think you are right that 10Khz sample rate is a bit slow. How ever for the bang bang control you probably don't need much more resolution for a ramp wave form of 5 to 20mS to filter. using a mbed for delta modulation is over kill you could probly use a adruino. cirtanly a microcontroler combined with hardware would be a awsum way to controle feedback and reduce parts count. I will probly end up using all hardware at this point for feedback.
Hmm I suppose a 10 mS ramp corresponds to just 100 Hz, so there's 10 KHz is a reasonable switching rate. The micro doesn't really save parts, given that the comparator-with-hysteresis approach is a comparator and a few resistors. The Mbed is definitely *not* the way to go even with that approach; I used it because I happened to have one around at the time. If I do keep the software approach (which at this point looks less and less likely) I'd use this
Registered Member #2922
Joined: Sun Jun 13 2010, 12:08AM
Location:
Posts: 226
Eric
I tryed to make some simulation in LTspice with a RC integrator and I get only sheet, hehehe.
I tried a simples quantizer/comparator (amp with ramp at +input and feedback at -input) , the output of the comparator driven the switch and at the same output the RC that summing at the feedback (-input).
Registered Member #195
Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111
hi Dr. Isotop that's a nice package lots of stuff on it. it seems that arm is prity popular to. I like MBED and Arduino because there is a large base of users. when it comes to software I'm prity much a newbie but when it comes to hardware I think of myself as not to bad. micros have a lot of potential.
Gregory, I kind of have the idea but do you have a schematic
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