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AMC1301: Electrical Safety Specification Progress Issue(isolation and creep distance)

CHO SR
Genius 3415 points
Part Number: AMC1301

Hi,

The customer failed the electrical safety specification test.

Specification failed :

AMC1301 is not satisfied with the isolation distance specification because the PIN spacing is less than 3mm.

AC input voltage is considered primary voltage even if voltage drops due to R28,R29,R33,R34,R35 because it is not separated primary and secondary.

Improvement measures:

Isolation AC220V input to AC_N_F and AC_R.

Added Transformers, Isolation Voltage : 3kV more than.

1) Transformer application of input AC220V and output AC40V or less.

2) Voltage drop of input AC 220V to AC40V or less using resistance to apply a transformer.

Q1. Are two methods possible as improvement measures?

Q2. Please recommend me a better way to improve it.

  • 0
    TI__Guru**** 175081 points

    Hi CHO,

    Before we get into discussion of a transformer coupled circuit, can you tell us what safety standard are you trying to meet?  From your schematic snippet, you do not show how G_HR is referenced back to AC_R which would be the typical application connection.  Pins 1-4 are usually considered as 'primary' connections while the 'secondary' connections are pins 5-8.

  • 0 in reply to Tom Hendrick
    Genius 3415 points

    Hi Tom,

    The safety standard are KS C 1511. (KS C IEC61009-1:2013 & KS C IEC 61010:2010)

    I requested additional requests to the customer as follows.

  • +1 in reply to CHO SR
    TI__Guru**** 175081 points

    Hi CHO,

    When we do Impulse Testing with the AMC1301, the voltage is applied from pins 1-4 to pins 5-8.  The isolation is between the right and left sides of the device, not from pins 1-2.  Pin 4 needs to be referenced to the high voltage.  You can do that by splitting R34 into 2 resistors (each 235 ohms) and tying them to GND1 or short (essentially) pins 3 and 4.  The 5V_HR needs to be an isolated supply that 'floats' on the high voltage rail.  This should satisfy the safety requirements.

  • 0 in reply to Tom Hendrick
    Genius 3415 points

    Hi Tom,

    Thank you for your support.

    We will take note of the advice.

    Sorry, There was confusion because there was no ac input schematic.

    The certification specification must be more than 3 mm in distance between the AC pin(2) and the DC pin(1).

    The distance between pins cannot be changed, so the AC input is isolated. (Improvement 1, 2)

    I want to know if there is any functional problem even if I change it to improvement 1 or 2.

    If there is no problem, please recommend between improvement 1 and 2.

  • 0 in reply to CHO SR
    TI__Guru**** 175081 points

    Is the issue due to the isolated 5V DC/DC?  In other words, if 5VS was used to power the AMC1301, would that satisfy the safety guys?

  • 0 in reply to Tom Hendrick
    Genius 3415 points

    Hi Tom,

    No, the gap between DC Pin and AC pin of AMC1301 is a problem.

    5VS does not satisfy the safety specifications.

    AMC1301 pin gap is a problem because the AC line is input without isolation.

    When not isolation, the safety specification has an IC pin gap of more than 3 mm.

    So the customer wants to make an isolation AC input.

    Change 1 :

    Change 2 :

  • 0 in reply to CHO SR
    TI__Guru**** 175081 points

    OK then - I'll need to look into the standards, this particular requirement is new to me.  Option 1 would be better in my opinion, just step down the AC through a transformer.  I'd still use the split resistor approach and reference everything on the AMC side to GND1.