The problem with TNY284PG (ripple voltage too much)

Posted by: quanln on 08/02/2018

Hi,
I have design smps using TNY285PG and I have a proplem, the ripple voltage is too much. The attachment file below is my design.
In my schematic, I have removed some parts to reduce costs (because I use it in huge numbers). The output of TNY285 is 5VDC
Problem: The ripple voltage too much, The measure is 270mV with OSC.
Can you help me solve this problem.

Thanks
Lam Nhat Quan (Mr.)
IoT Maker Vietnam (www.iotmaker.vn)
134/82 Thanh Thai St, Dist. 10, Ho Chi Minh City, Vietnam
M: (+84) 1208131474
E: quanln@iotmaker.vn

Files

power-tinyswitch-iii-touch-sch.pdf (34.09 KB)

Comments

Hi,

Thanks for using power integrations product.
To help you in your design,

1) What is the output power of your design? 3W?
2) Is this used for microcontroller supply?

I have noticed that you only used 4.7uF on your input capacitor.

be careful you have only 150R rcd clamp resistor...that looks too low.
aLSO, ARE YOU OVERLOADING YOUR OUTPUT? (sorry about capitals)
Also, it is an on/off converter so you put up with ripple to an extent

Thanks for your reply.
In my design, the output voltage is 5V. I will use 1 LDO to convert to 3,3V (supply power for esp32).

I used 4.7K input capacitor

Hi treez

"be careful you have only 150R rcd clamp resistor...that looks too low."
-> I don't know about it, because, this design is created by Pi Expert.

Hi quanln,

We would like to know what is the output ripple measurement look like with the OSC. Can you send us the screenshot of the output voltage ripple with this OSC setting:

AC mode
Volts per div = 50mV / div
Time per div = 5ms / div and 10us / div

As I noticed from you schematic, you didn't have a secondary diode snubber. Also if possible can you also send to us the PCB layout picture? Thank you.

Best Regards,
PI-SevenofNine