EDIT 21.08.19: scroll to the bottom to read about the recent consideration on the topic.
Hi All
----disclamer----
first time posting on the blog and i am not sure this is the right section for this topic. Feel free to point me to the more appropriate section or to a post that already discusses the topic.
General / open question (Below more context is given):
Can anyone point me to documentation or suggest me some DC voltage sensing cirquit? I am working on a project where i need to measure a voltage of roughly 270V.
Design restriction:
- No microcontroller, all analog
- Low budget
- Accuracy of ~1% with the voltage between 270 and 320V
- Low power consumption
context:
I need to design a voltage sensing cirquit for a DC bus of 270V. Multiple AC motors and the respective driver are connected to the DC bus. The circuit needs to "regulate" the dc voltage by powering a "braking resistor" (P
nominal = 500W) in case that the dc voltage raises above 300V. The option that i found to be the best at the moment is the "typical application Circuit" proposed on the datasheet of the ACPL-C87 sensor with some sort of schmit trigger or comparator stage at the end to drive the Mosfet of the braking resistor (see the attachements).
My concern with this design is precision. To measure the voltage i first need a voltage divider which is already pretty inaccurate. The ACPL-C87 accepts an imput voltage of 0-2V. The variation of the DC voltage is about 10% (((300-270)/270)*100) and since Vin is proportional i have roughly 200mV to work with.
Now,to me, it sounds a bit unrealistic to have a reliable measurement in an environment with high AC Noise.
Should i not be worried? Is there a valid alternative?
if something is unclear(maybe i should delete the "if") just ask, i'll be glad to give further explanation.
Thanks!