how to filter electrical fast transient??

[bene-tam]

my device fails the EN61000-4-4 test about burst/EFT

it is powered up with 110/230VAC to 12VDC adaptor.

the supplier cannot filter the transients inside their circuit, it has
asked us to do it ourself(i wonder if the input to my device is still
a small AC imposed on a large DC offset)??

how should i do the filtration with resistor/MOV/inductor/zener diode?

the 12VDC in is connected to a 12V to +-5V converter to drive the main
circuits.

the design by the ex-colleague consists of a 1n4001 for polarity
protect, a relay for "true" connection once the polarity is correct, a
fuse for limiting max current.

i surfed the web and found out that the input should be filtered
seems bead inductor would do the job, isnt it??

pls advice, thx so much

 

[Kevin McMurtrie]

my device fails the EN61000-4-4 test about burst/EFT

it is powered up with 110/230VAC to 12VDC adaptor.

the supplier cannot filter the transients inside their circuit, it has
asked us to do it ourself(i wonder if the input to my device is still
a small AC imposed on a large DC offset)??

how should i do the filtration with resistor/MOV/inductor/zener diode?

the 12VDC in is connected to a 12V to +-5V converter to drive the main
circuits.

the design by the ex-colleague consists of a 1n4001 for polarity
protect, a relay for "true" connection once the polarity is correct, a
fuse for limiting max current.

i surfed the web and found out that the input should be filtered
seems bead inductor would do the job, isnt it??

pls advice, thx so much

The wall wart and regulator should be taking care of the problem.
Perhaps you have a twitchy circuit that's picking up small RF bursts.
Something like an under-compensated amp, missing termination, floating
MOS input, ground/power feedback loop, sensitive threshold without
hysteresis, digital race condition, mismatched logic levels, etc.

Do you have a schematic?