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500W, PFC, isolated, regulated PSU advice
500W, PFC, isolated, regulated PSU advice
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Old 14th January 2007, 10:44 PM   #1
theChris is offline theChris
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Join Date: Dec 2001
Location: SIUE, Illinois, USA
Default 500W, PFC, isolated, regulated PSU advice

I am looking to embark on a project of building a 500W-600W isolated and regulated power supply with PFC. The target specs are:
1.) isolated from line voltage.
2.) 50V, 10A-12A output for use with class D amplifier.
3.) +15, -15V, 500mA outputs for use with analog circuitry
4.) addition of power factor correction.
5.) regulation of the 50V line
6.) linear regulation of +-15V line (lm317,337 or such)
7.) operation from 120V, 60hz lines

I am trying to determine how best to accomplish this goal.

The most elaborate way would use a converter for PFC, a converter for isolation, and a converter for regulation. This seems overly complex.

The next design would be to implement a PFC boost stage, followed by a bridge or double ended stage that has a feedback output on the PT, thus eliminating the need for another regulation stage, but I am worried about load regulation, since the feedback line is not loaded the same as the power output.

the last design would be to use an isolated boost design, with a regulator on the secondary. From what i've found, all choices are not particularly suitable. typically the choices have high ripple current or high voltage stress.

Would it be feasible to use a PFC stage in CCM with a comercially available PFC control IC to boost voltage to 250-400V along with a double-ended forward converter to provide the conversion to 50V, as well as provide isolation and regulation? A half bridge would also seem viable at these levels.
if only it could be used for good, not evil...
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Old 15th January 2007, 03:46 AM   #2
N-Channel is offline N-Channel  United States
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Please see this thread . Lots of good ideas on control method for the PFC stage, topologies and control method for the PWM DC-DC stage.

At most., you will need 2 converters: the PFC and the PWM. You are best to run CCM -v- CrCM (Continuous -v- Critical conduction mode) at the 500-600W level. Half-bridge topology will make best use of main isolation transformer. Full-bridge will work, too, but is more complex, and is not justified until you hit the 1kW level.

For the PFC, you could also try using a constant-frequency, then synch the PFC and the PWM together to eliminate beat frequencies from forming. Anyway, take a look at the thread.


-. ---.. -..- ---
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Old 21st January 2007, 08:21 PM   #3
theChris is offline theChris
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Join Date: Dec 2001
Location: SIUE, Illinois, USA
any idea how large an inductor would need to be? i can't find any way to get 1mH with a bias current of 10A. 10A is what I get for full power output /w 85% efficiency at low line voltage of 90V.
if only it could be used for good, not evil...
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Old 2nd February 2007, 04:19 PM   #4
sachserjuris is offline sachserjuris  Brazil
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Join Date: Dec 2006
Default toroidal


If I will use 2 inches out. diameter toroidal transformer and 358VAC + TL494 PWM, etc.. How many turns I can use in primary... and switching frequency...

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