Hi Joe:
If the 150 V DC is generated from the 3.7 V DC,
then a fault between the two circuits will cause
the 150 V DC to stop and become 3.7 V DC.
The Law of Conservation of Energy. There is no
way the 150 V can cause the 3.7 V to increase!
Therefore, there is no need to isolate the 150
V DC
In message 6.1.0.6.2.20101215231732.01cdb...@pop.randolph-telecom.com,
dated Wed, 15 Dec 2010, Joe Randolph j...@randolph-telecom.com writes:
Rich's question about what the potential current path would be has
bothered me as well. I'm not sure what sort of scenarios to test for,
but there may
Where is the loop for the current to flow!
If the person is part of that loop, there migth be some questions to answer!
I have no problems holding onto a few million volts,
tho' grounding might be a shocking experience.
If the freq is low enough to avoid being the antenna, no / little
Rich, Gary, Brian:
Thanks for your comments and questions. This is very helpful.
Just to clarify, I'm not concerned about the isolation barrier between the
high voltage circuit and the surface of the LCD screen. I'm concerned
about having to provide isolation between the high voltage circuit
Hi Joe:
What you describe is very similar to the flash tube
circuits in a digital camera.
Since you have measured the 150 V and the 300 Hz and
determined they are not limited current circuits, I
will offer comments based on these circuits being
hazardous circuits. (You did not specify the
This is a haz V, so SFC protection is required, and 2.2.3 provides the
limits.
As for back-light power sources, the models I have done were LCC - which
was easy to do because of a very hi-Z load, and as previously stated, were
buried under thick plastic. Also the units that I submitted had two
Sounds like a touch screen to me, UL is used to those. The isolation I believe
comes from the glass properties and the creepage and clearance distances
between the closest point of user contact and the Haptics voltages.
From: Bill Owsley
you could try it like an old Safety engineer from long ago used to do. Get
well grounded and grab the circuit - if he could let go... it was ok.
Note he always brought along some help.
Bill
In the event of a national emergency,
click on the following links to provide directions to your
Hello All:
I have been asked to suggest a UL/EN 60950 compliance method for a low power,
high voltage circuit that resides inside a cell phone. The circuit activates
a piezo-electric transducer that physically vibrates the LCD display at about
300 Hz in 30 mS bursts to provide the sensation of a
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