DocID023640 Rev 2

11/14

AN4160

Primary side TVS validation through power rating

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Primary side TVS validation through power rating

In order to guarantee reliability of the primary side protection TVS, an additional verification

should be performed. Current as well as voltage across the protection device during surge

should be measured and compared against the datasheet specifications.

In order to verify the exact power to be managed by the TVS, measured voltage and current

across the TVS during differential surge are reported.

Figure 14. Measured voltage across the primary TVS during differential surge

Indeed, most of the power is already absorbed by the MOV as first-stage protection.

The residual surge left after the MOV has a peak current IPEAK around 300 A and lasts

about 1µs. The measured peak voltage VPEAK is above 32 V. Therefore, the peak power

across the TVS during the surge can be estimated as PPEAK = 32 V x 300 A = 9.6 kW.

Now that the residual surge has been defined, it can be compared with the various TVS part

number datasheets.

100 V/div

10 µs/div

C34 max = 298V

C3 min = -122 V

10 V/div

50 µs/div

C4 max = 32.1 V

C4 min = -21.4 V