Hi,klausST.every device comes with a datasheet. Usally there you can find the relation between voltage and current.
Neither the voltage across a LED nor across a MOV is independent of current
Hi Tony.Looking at the curve slope I see A 10V rise rise from 1 to 10 mA
G1 N001 Vout TABLE {V(VG1,0)}=
+(193.5,1.E-6) (292.4,1.E-5) (356.9,1.E-4) (430.0,1.E-3)
+(473.0,1.E-2) (494.5,0.1) (516.0,1) (559.0,10) (774.0,100)
+(1290,1000) (2580,10000) (20000,5.E+5)
Oops,my mistake.So yes,I meant vertical.Hi,
these are vertical lines and mean "5 units"
Klaus
Yes but 10-1=9 using a decade log scale, pick the same plot to see my choiceHi Tony.
Isn't the curve slop(14D431R)that rise from 1mA-10mA: 60V rise (480V to 540V)?
One more thing about the U-I graphs of the varistors.
When the varistor graph is drawn as you may see at my attached photo,
Do the horizontal lines between the round numbers(marks with arrows at my photo)indicate 1 unit or 5 units?I think it indicate 5 units,but i would like to verify this.
View attachment 179152
This graph is sharper but not significantly better. My observation is the drop in voltage below 1mA due to DC test and above 1mA for impulse test 1| 10 us. Perhaps from inductive voltageHorrible diagram. Won't even try to guess about axis scaling.
A recent datasheet of your MOV is here https://www.bourns.com/docs/Product-Datasheets/MOV14D.pdf
Here's the respective V/I curve for 14D431K (topmost line). You should however consider two points.
1. As explained by KlausST, it's a limit curve, on left side minimal voltage for a specific current, not nominal.
2. Apparently the line isn't drawn very accurately, you get different slope in different document versions. Respectively I doubt that it's suited to find an exact operation point.
View attachment 179155
Generally, you are solving the nonlinear equation I*Rser + Vmov(I) = Vb. If you don't have a function for Vmov(I), you can find the operation point iteratively in the V/I diagram. You can also refer to a SPICE simulation model provided by Bourns https://www.bourns.com/engineering/MOV14D/MOV_14D431K.LIB
But it's specifying the V/I curve only very roughly in 1:10 current steps
Code:G1 N001 Vout TABLE {V(VG1,0)}= +(193.5,1.E-6) (292.4,1.E-5) (356.9,1.E-4) (430.0,1.E-3) +(473.0,1.E-2) (494.5,0.1) (516.0,1) (559.0,10) (774.0,100) +(1290,1000) (2580,10000) (20000,5.E+5)
Interpolating the table by polynomial (e.g. using MS Excel) would give you the best available fit.
The basic misunderstanding is to read the max leakage and max clamping voltage limit lines as accurate I/V characteristic specification, but they neither are nor claim to be. As KlausST stated, MOV is designed to clamp surges, not as a voltage regulator.This graph is sharper but not significantly better.
Agreed. It could act as a crude voltage reference <= 1mA but self heating and tolerances could be large but ESR will be minimized at 1mAThe basic misunderstanding is to read the max leakage and max clamping voltage limit lines as accurate I/V characteristic specification, but they neither are nor claim to be. As KlausST stated, MOV is designed to clamp surges, not as a voltage regulator.
The ESR always reduces with quadratic semi’s in rising current until the linear bulk Rs dominates . So above 1mA the test rises in R due intolerance to heat using the impulse test. You could certainly use less current and heat and the tolerances might be 10% like Zeners. Some may experiment to verify my hunch.Hi,
heating is about half a Watt per milliampere. It will heat.
I don´t see why ESR should be minimized,
I see it this way:
Leakage current is some kind of unwanted error. The manufacturer gives a maximum limit of a value that is guaranteed to be lower. How much lower depends on a lot of things. I guess even the purity of the silicon. So it may vary a lot from batch to batch. Even from part to part. I would not be surprised if I measure it to be just 1% of the given maximum value.
Klaus
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