Voltage sensing circuit using differential and isolation amplifier

Pemendra_CastNX123

Hi everyone,

I refer to design the voltage sensing circuit using the given below link

https://www.wolfspeed.com/crd-22ad12n/

In this circuit, to sense the voltage, the isolation amplifier (ACPL-C870-500E) and amplifier (MCP6031) are used.

The isolation amplifier provides optical isolation between the power circuit and the controller which increases protection. However, voltage sensing can be possible via only differential amplifier schemes. It is cost-effective and simple.

But why :-

1. People are going with both amplifiers to sense the voltage as given below image.

2. Can we use only differential amplifier to sense the voltage as given below image for the SiC devise-based product?

3. Is any other region to use an optical isolation amplifier to sense the voltage as described in the previous statement (i.e. protection)?

Please suggest what should we use for SiC-based product development.

TBhatia

Hello, thank you for your message. A member of our technical team is looking into your questions and we will respond shortly. 

jshao

Hello,

thanks for your questions.

Q1, the circuit is recommended by the manufacture. The output from the isolator is a differential signal so it is good to use an Op amp as a buffer to interface with A/D converter.

Q2. The sensing voltage is AC voltage, if you don't have isolator, you will have common ground as your schematic, the circuit won't work. If you sense DC bus voltage, and you can share the ground with your controller, then you don't need isolator.

Q3. Yes, it is common to use isolator every region.

Best Regards,

Jianwen

Pemendra_CastNX123

Thanks,

Jianwen