Question regarding Amp and bandpass filters. - Page 2 - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 16th June 2013, 04:14 PM   #11
diyAudio Member
 
Join Date: Jun 2013
Ok I follow and understand all of your math except how you came up wih the capacitor value.
Could you explain this again.

Thanks
  Reply With Quote
Old 16th June 2013, 09:32 PM   #12
gootee is offline gootee  United States
diyAudio Member
 
Join Date: Nov 2006
Location: Indiana
Blog Entries: 1
Yeah, I didn't explain that, the first time, actually.

I derived it in the thread entitled "Power Supply Reservoir Size", which was started by Nico Ras.

Knowing the maximum load current and the desired maximum peak-to-peak ripple amplitude, the minimum required reservoir capacitance can be calculated.

Since for an ideal capacitor, i = C dv/dt, we can make some assumptions and linearize in a neighborhood and say (ignoring ESR):

C = i Δt / Δv

where Δv is the desired maximum dip in the supply rail voltage when i amps are drawn for Δt seconds, and C is in Farads.

We can assume that Δt can, at worst, be the time between charging pulses, i.e. 1 / (2 fmains). And we get to pick Δv, the p-p ripple amplitude. And we can calculate the maximum load current.

Most people use the RMS current. But that isn't really good enough, because it only accounts for the possibility of a single sine wave and we should try to account for the worst case load. And that would be a DC voltage and current at the Vpk and Ipk level.

The Δv should be chosen carefully, taking into account the specified Vpk and the Vclip of the amplifier itself, to leave room for the Vripple, relative to the peak rail voltage. So

Δv = Vrail - Vclip - Vpk

I've done the algebra, and also took into account the ESR, using the approximation

ESR = 0.02 / ( C x Voltage_Rating)

and the overall equation for the minimum value of the required capacitance is

Cmin (in uF) = 1000000(Vpk/(Rload(Vrail-Vclip-Vpk)))( (1/(2 fmains)) + (0.02/Voltage_Rating) )

I just guesstimated the 22000 uF, from a spreadsheet I looked at that uses that equation. But we should check to see what the equation gives, for the 80 Watt into 8 Ohms case (assuming 60 Hz fmains):

Cmin = 1000(35.8/(8(46.2-5-35.8))) ((1/120)+(0.02/63))

Cmin = 7169 uF

That agrees with my spreadsheet, too, but it also results in over 5 Volts p-p ripple.

If we want ripple around 1.9 Volts, we get 22000 uF (and the max power without clipping also rises to about 96 Watts, with Vpk a little over 39 Volts).

BUT NOTE that if you use a 10% lower rail voltage, then 21800 uF would give you 1.73 V ripple and only 76 Watts RMS max, at the onset of clipping.

So that's why I picked 22000 uF.

You can find my Excel spreadsheet and download it from the thread I mentioned. Sorry I don't have the exact link at hand right now.

Last edited by gootee; 16th June 2013 at 09:35 PM.
  Reply With Quote
Old 20th June 2013, 04:42 AM   #13
gootee is offline gootee  United States
diyAudio Member
 
Join Date: Nov 2006
Location: Indiana
Blog Entries: 1
Links to my Power Supply solver and minimum reservoir capacitance Excel spreadsheets are in the post at:

Amp design attempt number 2 (simpler)
  Reply With Quote
Old 21st June 2013, 08:17 PM   #14
diyAudio Member
 
Join Date: Jun 2013
Default THANK YOU

Alright, Today I thought I would start to design my enclosures, but I am having a lot of trouble. I've tried various software and online calculators, but all of them have many differant paramateres for the speaker that I do not know.
I have:
1 10" MTX sub, 8 Ohm, 125RMS
2 4.75" (12cm), Panasonic, 6 Ohm, 45RMS
2 2.375' (6cm), Panasonic, 6 Ohm, 45RMS (a "supertwetter" piezoelement is attached to this tweeter which I hope to use"


How would I go about beginning to design this?

I am thinking of a ported enclosure for the sub.

I would like indidvidual boxes for each speaker.
  Reply With Quote
Old 22nd June 2013, 08:18 AM   #15
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
start a new Thread in the Speakers section
__________________
regards Andrew T.
  Reply With Quote
Old 22nd June 2013, 12:28 PM   #16
diyAudio Member
 
Join Date: Jun 2013
Alright, thank you.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Bandpass filters in audio circuit of communications receiver? SharpyWarpy Solid State 15 2nd December 2011 04:37 PM
What's this issue of ringing bandpass filters? sondek12 Multi-Way 2 18th January 2011 01:22 PM
6th order bandpass question tinitus Subwoofers 13 8th March 2009 07:01 PM
Question regarding bandpass enclosure wrankin Subwoofers 2 15th October 2008 01:30 PM
Bandpass Question jwatts Subwoofers 5 31st May 2006 02:13 AM


New To Site? Need Help?

All times are GMT. The time now is 08:11 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2