LYT1603 based Driver flicking issue.

Posted by: manvi111 on 06/05/2017

Hello,

I have used LYT1603 IC for my 10Watt driver using RDR-464 design. It works well with 89% efficiebncy. OVP is also working well.

But It starts flickering When I place two driver nearby.

Driver Details

Power Input : 180-300 VAC (220 VAC), 50Hz , 10.3Watt Total usage, 89% Efficiency

Power Output : 48 V DC, 190 mA

Indcutor : EE16, 160Turn, 1250 mH

MUR160 Diode, 0.33E Feedback,

100uF output capacitor, 47nF +100 nF + 2.2mH Input Filter

It works well when there is no other driver nearby. But It start flicker when two same driver placed nearby. I have attached layout

When I try to shield the area with copper tape it will stops flickering. There is no issue with that.

Please Also note that. I have tried some different PCB layouts but problem still occurs.

Files

Attachment	Size
10W with Shielding.png	34.7 KB
10W.png	37.63 KB

Comments

Hi,

I am getting someone to verify this issue on RDR-464. In the meantime, I suggest that you try to move RFB away from the inductor. Try not to place RFB underneath the inductor.

Thanks for your answer.

I will try the new layout with your suggestion and get back to you.

I will move Rfb to another side of IC. (Near the copper heatsink)

We verified two RDR-464 to double-check and we did not see that issue. RFB sets the output current so it's a good place to start.

Hello,

I have tried layout as per your instruction. But Problem remains same. I have found that there is problem in MULTIFUNCTION Pin and track of same.

There is no problem with feedback track. I checked in many ways and many position and sure that MULTIFUNCTION Pin and it’s track is the problem.

I have attached below three files

Layout of driver: Changed layout according to your suggestion. Position of FB is moved. Now feedback track does not create any flickering problem.
Layout with shielded area shown: When I try to shield this area with copper tape. Flicker does not happen.
Position of driver during flickering: Driver flickering when I try to put two running driver in this position. Please also try same position in your driver and ensure that both drivers are running.

Attachment	Size
10W_2 Flickering.jpg	66.78 KB
10W_2.png	41.7 KB
10W_2 with shielding.png	31.53 KB

Still Waiting for answer..

Would you mind capturing some waveforms? I want to be clear what kind of flickering and how severe the flicker is. Please compare the output current.This will help me understand where the problem is.

What is your THD requirement? If you can accept a higher THD, then I suggest you use LYT1403.

I have attached waveform of output voltage in both conditions. (Regular and Flickring)

Let me know if any other thing required.

I cannot accept higher THD so cannot use LYT1403.

Have you tried the up side down positions of two drivers in your RDK? (As shown in recent attachment.)

Attachment	Size
Comparision of Waveforms.png	13.12 KB
Flickring WaveForm.png	9.17 KB

I think the unit is seeing a fault condition because the switching stopped for a while. I suspect it's output OVP. To confirm this, you need to lower the value of the RLOWER of the M-pin. The unit goes into OVP if the M-Pin voltage goes above 2.4V.

Hello,
Sorry for the late reply. Your URL of forum has been changed so.

I have changed RLOWER from 16.5K to 11K. (OVP increased to 94V).
But Still same flicker happens.

Reminder

hi,

Sorry for the late reply. Just came back from holiday. Have you checked other waveforms to determine what's happening? Drain current and voltage waveforms will tell if the switching actually stops. Now, I am seeing a 50 ms interval which is unusual. The fault is usually 150 ms or 1s. Did you check the BP voltage? It should not drop below 4.5V. I don't know what capacitance you used but you can increase it.