LinkZero-LP Design

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Hello,

We are trying to design a standby power supply using the LinkZero-LP family.

Requirements are below

Input voltage from PFC 385VDC MAX 400VDC
Output-1 25VDC 150mA
Output-2 25VDC 150mA

I was unable to make the design in the PIEXPERT, it is only possible in the PIXIs witch is not a good option for me.
However the PIXIs is not showing the schematic, I also get many errors.

I also tried designing LNK624PG, everything looks good except the BULKY diode RMPG06, I don't know why such a low power circuit needs such a huge diode.
We are limited to space, I have seen much simpler circuits using generic diode like 1N4007 in AP3970P7-G1

Is it possible to get some valuable advice quickly here?

Thanks

Hi,

Thank you for considering Power Integrations part for your design.

PIXLS application gives you more flexibility on a low level but the schematics has to be taken from the datasheets or app. notes and adapted manually.

I have created a LinkZero-LP design in PIXLS for you for the spec provided. It could be found here:
https://piexpertonline.power.com/piexpert/design/select?share=75630324005ce3d0660bec71495382cb1f3de50bf92d82dc52263bed7f54d407

If you prefer to use PIExpert LinkSW CV is another possibility as the circuit you are already designed.

In both cases though, for 3.5W you need to employ some sort of clamping circuit with a high voltage rated, relatively quick recovery rectifier to limit the stress over the switch.

Using general purpose rectifier is problematic because the rectifier is leaking back current during the reverse recovery time. On the other end - Schottky diodes are expensive and its sharp response may cause EMI issues.
Any choice in between will most likely provide a satisfactory solution. Schottky will work excellent when EMI is under control. You can try the glass-passivated 1N4007GP also if the size is acceptable or similar performance SMD part.

The other option is to try using 900V device for example LinkSwitch TN2 with tight transformer design (low leakage) and very light clamp, meaning low current and smaller size diode. It will require some bench evaluation to optimize. Please check all possible operations condition like transient... etc.
https://ac-dc.power.com/sites/default/files/product_document/data_sheet/linkswitch-xt2_family_datasheet.pdf

Best Regards,

Hello

Thank you for your response.

I think that we will go with the LNK626, it has everything we need.

But in all generated designs we still see the RMPG06 bulky diode.

on the other hand, while looking at

(https://ac-dc.power.com/design-support/reference-designs/design-examples/rdr-201-6-w-constant-voltage-cv-adapter/)

That design looks very good to us when it comes to the size of the components etc, I also wonder why I don't get the same parts when I design that inside PIEXPERT? D1 especially.

I am attaching a design that I think we will proceed with if you don't mind taking a look at it.

The circuit is fed from PFC, what about EMI? do we need any additional EMI filtering? or you suggest using a special rectifier and EMI filter for the supply?

There will be two voltage regulators tied to those 25V outputs to regulate it down to 15V or maybe 12V.

The main idea of using this is to meet the 0.1W in standby power consumption

Please advice

TitleSize
LinkSwitch-CV_PIDesign1.pdf65.6 KB

Hi,

To you use a diode different than the recommended, please make sure that you have enough switch voltage safety margin in any possible operation condition including load transients.

I am not sure though why are planning to use linear regulators when you can design the SMPS to regulate at the desire final voltage instead. Cross regulation would not be a issue with 2 same voltages secondaries - just wound them bifilar.

If there is another season to use linear regulators from 25V to 12V, you can reduce the output voltage of the SMPS from 25V to 15V or so and achieve better efficiency.

The above comments are generic, as I am not aware of the full design spec.

The schematics looks OK but it does not provide enough information. I could look at the design file if you send it to piexpert@power.com.

Best Regards,

Hi

Thanks for the replay.

You are right about regulating one of the voltages down to 12V, but the reason for the other 25V that must go to the other regulator with (ENABLE / DISABLE) function to turn ON/OFF the main SMPS and keep the standby power under 0.3W maximum.

I don't know if you have other ideas to turn ON/OFF the main SMPS.

Then I will go with one output 12V and the other 25V as you have suggested, and I will send you the file.

Thanks!