TOP249YN GX
I have been having an issue with the a TOP249 dropping out during an arc of x-ray system. I have disabled the sense pins of the device and still see it shut down during operation, and the voltage to the "Control" pin is aobve the undervoltage threshold. The device is being used in a circuit to convert 400 Vdc to +/- 12Vdc supplies, and two 15Vdc supplies one for feedback to operate the Top switch. I can not understand why the device is shutting off.
Thanks,
Dan Sherman
Comments
I am attaching a copy of the schematic
Dan
Your schematic looks good. I do not know what do you mean arc and I guess when X ray arcing, the load current is a lot higher than normal, and thus trigger auto restart.
The arc I am refering to is a x-ray tube arc in the system.
What is auto reset that is being triggered? We have disabled OV/UV and current sense pins of the Topswitch by grounding pins 2 and 3 to pin 5. The 420V input voltage does not sag during the arc event but I am seeing the chip reset.
TOP switch can sense the current limit. And auto restart could be triggered by the over current when arcing happen. If the X ray tube was powered by the topswitch power suppl, then it is very possible that auto restart triggered by over current.
What current limit is the Topswitch sensing if the pin 3 is grounded?
The Topswitch in my system is only providing power to my control board and should not be affected by an arc in the system. The 12V that drives the optocoupler to provide voltage to the control chip of the device does not dip but the Topswitch drops out.
Dan
We use a Sense Fet to measure the drain current through the TOP switch. Typical Drain current is 5.4A if the X pin resistor shorted to ground.
could you upload your schematic?
thanks