Why are input and output grounds shorted for an isolated DC to HVDC converter module?

Thread Starter

kevivitron

Joined May 8, 2024
2
Hello and thanks in advance for any potential answers.

Background:
I am planning to use a DC to high voltage DC converter module (XP Power G40) for a electro-adhesion based project. It is a compact and isolated power supply module which takes 12V DC as maximum input and provides a proportional high voltage DC output up to 4000V. At the output I have a bleeder resistor (parallel to output), a current limiting resistor (in series), and a custom capacitor (electrodes for electro-adhesion).
Block diagram of the module:
1715179459540.png

The issue(s):
The application note by the manufacturer (AN9) recommends (among other things) essentially connecting the input and the output grounds together (for +ve output). Check image below (actually from datasheet).

1715178881679.png

But why? I can't figure out if this is a requirement for normal operation or just a suggestion. Can the module work with floating HV output? Is it actually a true earth connection for safety purposes? Can this damage my low voltage power source? What is the point of having an isolation transformer if you are going to short the isolated sides?

Well my primary question is if the short is required for normal operation or it can be avoided. But any tips regarding the design of the system around it would be highly appreciated, especially safety tips. Please let me know if any further information is required because this is literally my first post here.
Thank you for your time.
 

BobTPH

Joined Jun 5, 2013
9,300
I scanned the app note you linked and I see no such recommendation.

The only place it shows the connection is when feedback is used to regulate the output voltage.
 

Thread Starter

kevivitron

Joined May 8, 2024
2
Hello and thank you for both of the replies above. It makes sense then that it is not a compulsion to connect the input and output grounds, unless a feedback is required. But just to be sure, is this also what seems to be implied in the datasheet as well? As is in the image in my original post, which is is not actually not from the application note but the datasheet itself?
 

BobTPH

Joined Jun 5, 2013
9,300
The illustration from the datasheet is there to show you how to make the output voltage either positive or negative WRT ground. That does not mean it is required.
 
Top