I have followed the design attached in PDF. It is from ST designsuit.
I have used MYRRA 75032 flyback transformer. (Datasheet Attached)
Optocoupler 140105146000 with CTRmin - 50%, CTRmax - 150%.
So now problem is I am not able to get continuous Vout from flyback. There is hiccups. IC shutdown after every few cycles and restarts. As shown in VCC waveform VCC capacitor is charged till ~13V. IC turns on Switches for 2mSec Vcc goes till ~20V and switching stops. Vcc voltage decays, when it goes below 7V IC turn off. When it goes below 5V Vcc capacitor starts to charge itself by internal current source. Cycle repeats.
My interpretation - Since IC restarts everytime at 13V (VCCrestart voltage). I can say IC goes into latch state while switching. But i cant find the reason for latching. Need some guidance.
Other findings.
Output is connected only to LED load. So I cant find much raise in VCS voltage. (Voltage across Current Sence)
Also VDS spikes to 510V still within limits mentioned in datasheet.
Input bus voltage is steady. No high temperature.
When Reading Comp pin: I couldn't get much idea from it.
Later updates:
I have included Vout (Flyback output It is designed for 24VDC). But Vout spikes for about 37VDC and it decays.
I think there some series problem in Vout feedback loop.
To get 24VDC Vout i have changed R18 from 18K to 22K. (Refer design PDF)
I need to find the problem and solution for it. @Peter BENSCH @Sirichai JAIPACHR @EDokm
Thanks for your concern.
Following images are:
1. VDS - Drain voltage across mosfet.
2. VDS - Drain voltage (Zoomed Out figure)
3. Output Winding Vout.
I
4. Aux Winding output:
5. VCC
6. Comp Pin
Vout (Flyback Output):
