Hi Readers,

I am observing an inrush current drawn an electronic control unit when it wakes up. This brings down the supply voltage to 6 V so I am trying to figure out why the electronic controller is drawing a large current when it turns on. This controller is responsible for controlling lights, dc motors, etc. This controller doesn't drive these loads unless it receives the driving commands from another controller. I couldn't see any light getting turned on or motor spinning when the controller wakes up and it still draws a large current despite that.

so what are the probable causes for this inrush current? I know they could be a myriad reasons but nice to know as many of them as I can.

 

Does this controller have capacitors in it?

 

Yes, many at different places. I assume this capacitor might be drawing a high current when it receives the power. What is the simplest method to measure the total capacitor value of the PCB board?

 

We need more information to be able to provide a useful answer to this question. How much current does the ECU draw in normal operation? How much current is the supply able to deliver, and what is the supply voltage supposed to be?
Charging internal capacitors is certainly one reason for inrush currents, in addition there is the possibility of indeterminate logic states at the first instant of power application.
Is this ECM a single unit? or is this a product line that may have developed a problem? Is the ECM suspected of being defective, or not? More information is needed to allow a useful answer to be made.