2. Each design's output current  rising 200-300mA in a few minutes. What can be do for stabilizing?

Make sure Iv and IFB currents are stable. Increasing IFB and decreasing Iv causes Iout to rise and vice versa. Layout on FB and V-pins should be as neat as possible to avoid leakage paths. Make sure C14 is not leaky.

3. No load ouput voltage is more than %50 of the desired voltage. (Desired 50V, result 75-80V) Decreasing zener voltage effecting output regulation and efficiency.

Overvoltage through bias depends on secondary to bias coupling. This coupling and ovp zener tolerance dictates your overvoltage level

4. Constant current region is very restricted. Max 7-8V. I need less than %50 max string voltage.

CC in these IC's are optimized at 150uA IFB. A good CC can be found if operating IFB on the range of 90-210uA.

 7. Can I replace the sense circuit in DER289 with ST's SEA05 or TSM1052 CV/CC secondary side controller?

Yes you can use alow drop regulator on the secondary

8. Is attached schematic CV-CC  suitable for this design?

Its good for CC and a little portion on CV. On the schematic, R12 provides the minimum current fed to FB pin. This minimum current is used so that the controller will not enter autorestart. During CV mode if the FB current falls to the minimum IFB(D7 reversed biased due to low output current/power), you will lose control of the CV and output voltage will tend to go high.

Dear Dunwell,

I tried the attched schematic. (57V-700mA) As you told; CV controlling is nearly not working and reach over 100V in no load. I have to keep no load voltage precisely a few volts above the max string voltage. Is it possible with attached schematic and LYT-4 series?

Thanks,

Dear Dunwell,

I tried the attched schematic. (57V-700mA) As you told; CV controlling is nearly not working and reach over 100V in no load. I have to keep no load voltage precisely a few volts above the max string voltage. Is it possible with attached schematic and LYT-4 series?

Thanks,

As of now, we havent released the CV mode app note for LYT-4. Your current schematic as I've said earlier will lose ontrol of the output voltage at light load and will not meet your required precise no load voltage.

We'll inform you (or keep watch on latest design example reports with CV) if the said CV mode operation for LYT4 is ready. 

Dear Dunwell,

Can I use hatched section in the schematic by replacing directly for TOPJX and Hiper LLC for tight and wide CC / CV regulation?

Regards,

Yes. Just take note that the control pin of TOPSwitch is to received the feedback current. So normally, the emitter side of the optocoupler(not the collector) is connected to it.

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