Unexpected shutdown in TNY284DG
Hello everyone,
I made a 6W power supply with a TNY284DG, designed in Pi Expert 9. Its output is 12V, 0.5A, plus a small 5V linear regulator for a microcontroller.
The goal is to control an 1/2HP AC induction motor with two 12V relays using the microcontroller, each relay for a spin direction.
The power supply seems to works fine, it has a stable output voltage under load, and the ripple is under 50mV. But, after a while working (few minutes), the power supply always shutdown permanently until the main supply is disconnected. Sometimes it shutdown when the motor turns on, but is a little unpredictable.
When the power supply shutdown, the output voltage drops permanently to 1,22V.
The DC rectified high voltage remains stable and voltage under capacitor in BP/M pin is 5.92V.
Any ideas?
This is the power supply schematic, but I don´t use C1 (4.7uF 400V) due a mistake in PCB design:
This is a simplified connection of one relay, it has a MOV to reduce arcs:
Thank you in advance
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Is there anyone here?
Hi Alex,
Good day and thank you very much for considering TNY284DG for your application. Looking at the schematic it seems ok. Now have you tried verifying the current level on the BP pin when the unit turns off? What is the tolerance of the 0.1uF cap that is being used? In addition since you are not using C1, does it mean you are only using one cap hence C2? kindly verifiy since you might be triggering the UV protection.
After power supply shutdown, if I touch EN/UV pin with the finger, or if I touch this pin with a oscilloscope probe, the power supply turns on again, no need to unplug the AC main power.
Any help?