Author Topic: Wide input and output range power pre-regulator (85–265 Vac / 2.5–52.5Vdc / 5A)  (Read 4060 times)

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Offline LapTop006

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For "safety" agencies, I thought 48V was their limit? The 52V output on this project might raise a flag on its own, but the other outputs are all very low and even were they added together they are less than 48V aren't they?

50v is the nominal safety limit (at least it is where I'm familiar with), however actual float voltages on 48v systems are often about 53 volts.
 

Offline elecdonia

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This project is fascinating!
Thank you for sharing it.

I have one technical question:  Would it be possible to add an "active power-factor correction (PFC)" section at the AC mains input?

The advantage of adding active PFC is that it provides increased efficiency and reduces the peak input current taken from the AC mains source, especially during initial start-up.

There are a large number of inexpensive IC chips available for PFC circuits. In addition to the PFC IC chip, this circuit requires one power inductor, one power diode, and one power MOSFET.

Essentially the PFC is a switching regulator of the "boost" "step-up" variety which raises the instantaneous AC input voltage up to the desired voltage for the main filter capacitor energy storage device.  The PFC circuit is positioned between the AC mains bridge rectifier and the main filter capacitor energy storage device, which is typically a large capacitor, 100 to 200uF, rated at 400V.

In contrast a traditional diode bridge connected directly to a large capacitor will conduct only when the instantaneous AC input voltage is greater than the dc voltage currently stored in the main filter capacitor. These short pulses of relatively high current cause noise on the AC mains and also can "clip" the peak crest voltage of the incoming AC mains so that instead of a pure sinus shape it will resemble a clipped sine wave.

Best regards and good luck with this project!

 
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Offline prasimix

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Thanks for your suggestion. Sure that PFC could be added but that requires increasing of PCB size, although that shouldn't be a huge increase. That could be a nice next step.
In this moment what I'm going to add without changing PCB size is a on-board sub-miniature fuse (TR5). I think it should be in the module despite the fact that AC input will be externally protected and fused (e.g. using AUX PS board that is part of another ongoing project).
 
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Offline elecdonia

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Yes, the additional fuse mounted on the PC board is a terrific idea for overall safety. Highly recommended to add it to your design.
 

Offline schmitt trigger

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This project is so well done, and so thoroughly documented, that we may find a Shenzen clone one of these days.
 
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Offline jbb

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Can you find a fuse that is rated for DC breaking as well? It’d be useful for DC distribution (eg single PFC feeds many converters).
 


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