TNY277 EN/UV
Our design with the TNY277 has been in production for over two years and is working well. However, a customer issue has made us aware that undervoltage lockout is not working as expected. Details follow.
* AC input range for our design is 85-264V, resulting in a DC bus of 120-373V after full wave rectification.
* 4Mohm resistor installed between DC bus and EN/UV.
Based on our design, we expect undervoltage lockout to be: 22.5uA * 4Mohm = 90VDC minimum, and 27.5uA * 4Mohm = 110VDC maximum. However, this does not appear to be the case, because the power supply continues to operate well below 70VDC (50VAC). Furthermore, examination of Figure 13 in the datasheet suggests the 4Mohm resistor will result in operation below 50VDC (35VAC).
Is there a problem with the undervoltage lockout function? if not, what am I missing? Please advise.
Thanks
コメント
Hi,
EN/UV will act as a UV pin before the the switching activity starts. Once the part starts switching it will act as EN pin.
This feature will be useful during the line dropout conditions where the output voltage will be in regulation all the way down to very low input voltages unless the part enters into power limit.
One could even reduce the input capacitance with the use of ON time extension feature. I am giving here a link to one of our article.
http://powerelectronics.com/site-files/powerelectronics.com/files/archive/powerelectronics.com/704PET22.pdf
If your application needs UV turn off feature, then I would recommend you to use our INNO-EP device which has dedicated pin for input UV/OV.
You can find details regarding Inno-EP product at folowing location
https://ac-dc.power.com/products/innoswitch-family/innoswitch-ep/
Regards,
PI-NANO
I'm still waiting for a reply.