Mains transformer power supply - backend for Riden RD6012

[rlohmann]

Hi,

I have a RD6012 with a blown TO-263? buck converter (next to the wifi module cutout), on which I can't read the making anymore.



Hopefully someone has a open/working unit and could share the labeling.

UPDATE: I assume it's a XL7015 ...

Thanks,
Rene

[AJ3G]

That is in fact the Buck Converter. The XL7015’s can be had very cheap from distributors in China. I wonder how that happened?

[badgerthing]

Here is XL7015, if that's what it is: https://lcsc.com/product-detail/DC-DC-Converters_XL7015E1_C73013.html

[rlohmann]

Thanks @AJ3G @badgerthng for the confirmation.

In fact I'm also wondering what happend to the unit. (got it broken)

I've meanwhile figured out that the step-up converter (I assume SX1308) after the XL7015 was shorted to ground.
Just ordered both and hope I get the unit fixed by replacing both.

Btw, does anybody know if there is a schematic available for the RD6012 (or RD6006)?

[AJ3G]

I am not aware of one. I have looked mostly for a 6018, without much luck.

Rich

[Thermionix]

Oh, and here is photos of the current finished version that I am taking measurements from.
There will be one more PCB revision with a more adjustable fan controller and some bodges fixed.

https://imgur.com/a/f4WbrPy

I'm planning to build a linear supply for my RD6012

How are you finding the ripple?

V pp = I / ((2f) C)
V pp = 12 / ((2x50)x0.024)
24mFD gives 5 V Ripple @ 12Amps

Seems extreme

I was looking at your schematic and I believe powering the soft-start off VDC isn't recommended - the circuit won't reset quickly enough if there's a short power loss as the filtering caps will retain a charge - keeping the relay active, the relay will stay latched until <10v

I then did some reading -  https://sound-au.com/articles/soft-start.htm
 "Many fail to ensure that the circuitry resets itself quickly, so a rapid on-off-on cycle (whether by design or accident) provides protection after a brief interruption.  In general, any circuit that does not reset in under 500ms should be considered a fail.  A full reset ensures that when the power is restored (after perhaps 1/2 second or so), the ballast resistors are in circuit again, and the soft start is performed just as it would if the equipment were turned on after being turned off overnight"
 I think I'm going to build a seperate inrush controller based on Figure 6A on that page.

[Everbrave]

I have done quite a number of experiments comparing the linear back-end with a MeanWell NRD-240-48 with a specified 150mv Rippe&Noise.
The conclusion is, the final, regulated, noise & ripple at the switching freq. (not the line 50Hz) is dominated by my RD6018 itself. With the linear back-end, I gain only few mv of (less) ripple. e.g. 20mv rms @20V, 4A for the linear BE instead of 24mv rms with the MeanWell switching power supply.
I am still planning to build a larger linear back-end with a 400VA toroid Transformer to test further but the published results seem to support my observations (200-300mvpp) no matter how well you reduce the input ripple at the line freq.