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PeeCeeBee V4 GB!

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#467
gtose said:
I am starting to size up the PSU requirements for a stereo build and, from comments here and in the main design thread, I think I have arrived at the following specs. I would appreciate for some confirmation of what I'm thinking below and that I'm not hanging my hat too much on Ohm's law where it does not apply 😱

At 35VDC into 8R, there will be 35/8 = 4.375A per channel of current at a full voltage output. This lines up with other recommendations of 150VA per channel transformer recommendations: 4.375 * 25VAC = 110VA.

Using these numbers, I am hoping to use a 300VA, 28VAC transformer in conjunction with Prasi's CRC PSU board to power a pair of PeeCeeBees. The specific transformer specs I plan on using are at: http://www.antekinc.com/content/AS-3428.pdf. This shows 26.6VAC output at a load of 10.7A, close to what I'll be targeting.

Given this, 26.6*1.414 = 37.6VDC rectified output, plus a diode voltage drop of 2*1.25V = 2.5V (using a MUR1540 as an example), gives me a total rectified voltage of 35.1VDC.

The next voltage drop would be from the resistor in the RC filter. In calculating this component's specs, I am looking at voltage drop and power rating for the resistor. At 4.375A across a 0.2R resistor, I would get a voltage drop of 4.375*0.2 or 0.875V and a required power rating of 4.375* 0.875 or about 3.8W. I could then plan on using a 5W+ resistor at 0.2R and would arrive at a final voltage (under full load) to the PeeCeeBee of 35.1-0.875 = 34.23V. I am assuming this would be sufficient for the PeeCeeBee?
Click to expand...

Sounds perfect. I have also posted a BoM+Calculation sheet in CRC thread to ease selection of components.
 
#472
prasi said:
Sounds perfect. I have also posted a BoM+Calculation sheet in CRC thread to ease selection of components.
Click to expand...

gtose said:
I am starting to size up the PSU requirements for a stereo build and, from comments here and in the main design thread, I think I have arrived at the following specs. I would appreciate for some confirmation of what I'm thinking below and that I'm not hanging my hat too much on Ohm's law where it does not apply 😱

At 35VDC into 8R, there will be 35/8 = 4.375A per channel of current at a full voltage output. This lines up with other recommendations of 150VA per channel transformer recommendations: 4.375 * 25VAC = 110VA.

Using these numbers, I am hoping to use a 300VA, 28VAC transformer in conjunction with Prasi's CRC PSU board to power a pair of PeeCeeBees. The specific transformer specs I plan on using are at: http://www.antekinc.com/content/AS-3428.pdf. This shows 26.6VAC output at a load of 10.7A, close to what I'll be targeting.

Given this, 26.6*1.414 = 37.6VDC rectified output, plus a diode voltage drop of 2*1.25V = 2.5V (using a MUR1540 as an example), gives me a total rectified voltage of 35.1VDC.

The next voltage drop would be from the resistor in the RC filter. In calculating this component's specs, I am looking at voltage drop and power rating for the resistor. At 4.375A across a 0.2R resistor, I would get a voltage drop of 4.375*0.2 or 0.875V and a required power rating of 4.375* 0.875 or about 3.8W. I could then plan on using a 5W+ resistor at 0.2R and would arrive at a final voltage (under full load) to the PeeCeeBee of 35.1-0.875 = 34.23V. I am assuming this would be sufficient for the PeeCeeBee?
Click to expand...

Hi gtose,

Shaan wrote this:

"Due to high saturation voltage of Lateral MOSFETs you are already
going to lose 5V or so from the supply under load. So having a little
higher PSU headroom is better with these devices. A basic unregulated
PSU will drop even more volts than a regulated one, that's true. So if
you want freedom from that then go with a regulated PSU (which is
always welcome)."

Is the calculation for Lateral Mosfet then right?
 
#473
CitizenKane said:
Hi gtose,

Shaan wrote this:

"Due to high saturation voltage of Lateral MOSFETs you are already
going to lose 5V or so from the supply under load. So having a little
higher PSU headroom is better with these devices. A basic unregulated
PSU will drop even more volts than a regulated one, that's true. So if
you want freedom from that then go with a regulated PSU (which is
always welcome)."

Is the calculation for Lateral Mosfet then right?
Click to expand...

Hi Joachim.

The specified power output at 35V is calculated with taking into consideration the saturation voltage. So it's safe. 🙂

P=V^2/R
V=(35-5)/1.41=21.21V (Let's say 20V)
So for an 8R load
V^2/R=400/8=50W

Please use PM for sharing quotes from email conversation which is supposed to be private, or ask for permission to post in public forum beforehand.

Thanks.
 
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