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ds_mcu
ds_mcu
Visitor II
June 29, 2010
Question

hi all. please give me a hand. the questions about viper22a.

  • June 29, 2010
  • 1 reply
  • 728 views
Posted on June 29, 2010 at 13:06

 i have designed a AC-DC converter by using viper22a. the topology is fly-back. as the viper22a's datasheet say, the Vds(st) should be less than 400V. so i want to know if the viper22a may be damaged when the input AC voltage is 300V ? at that time,Vds(st) would be 424V (300*sqrt(2)). it has excessed the maximum Vds(st). what on earth does the Vds(st) mean?

      at last ,i am sorry for my poor english. please sb give me a definitive answers. thanks.

#viperplus #viperplus
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1 reply

difranco.fabrizio
difranco.fabrizio
Associate
June 29, 2010
Posted on June 29, 2010 at 16:40

Hi,

Vds(st) is the maximum DC voltage that can be sustained by the internal current generator which operates the start-up of VIPer22A. So, if the voltage on the drain pin at start-up exceeds 400V, VIPer22A cannot start properly and ST does not guarantee the device. While in switching mode the maximum breakdown voltage of VIPer22A is 730V.

In this case I suggest to use VIPer27L/H which features 800V as breakdown voltage, both at start-up and in switching mode.

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