Apologies in advanced as this is kind of a vague question and due to my lack knowledge in this specific sector. I'm designing a circuit using a HLK-PM01 as the power supply which is a 3W AC-DC converter (240VAC -> 5VDC). The 5V will power some relays and will also further step-down to 3.3VDC through a voltage regulator which will power a MCU. Based on the datasheet of the HLK-PM01, a varistor, capacitor and common-mode choke are recommended to add on the AC side.
I don't really have a problem with the varistor and capacitor as they have a relatively small form factor. However, the common mode choke is quite huge and takes up a large space on the PCB. My question is how important is the common-mode choke?
My second question is selecting the correct common-mode choke. I am sourcing majority of my components from lcsc.com and some from element14, RS-Online and AliExpress. As LCSC is a china store, some of their products don't have clear specifications and I'm not sure what to look for exactly. I found a few chokes but not sure if it is suitable for this application and for AC lines.
UU9.8-10mH, UU9.8Y-10mH, FL2D-Z5-103
How do you identify if the choke is AC capable? Are there any small chokes that can be used for this application? Any help is much appreciated. Thank you in advanced.
Best Answer
The limiting factor is if you need EMI suppression. There are two reasons for this:
is to pass conducted emissions regulatory testing a choke is needed to prevent conducted emissions from SMPS's
is to prevent AC mains from passing noise to your device through the line
I don't know about chokes specifically, but if you want to sell this in a product determining capability will be asking the question: will this product by subject to regulatory standards. More specifically, conducted emissions on AC mains.
For UL or IEC testing, all the components must be certified, if the components are not certified then you'll foot the bill for the testing. So the first step would be to establish where you want to sell the product, then find the regulatory standards that you need for the product.
After that look for chokes with those standards.