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In the picture below, there are three TVS diodes in series (D13, D14, D15). They are placed from drain to -13V reference, which is the reference for the rectifier. The diodes are 1.5KE300A, they have a breakdown voltage of 300V, so if they are in series, the total is about 900V. My questions are:

  1. Wouldn't it be better to put the TVS diode in the output of the rectifier?

  2. Could the number of diodes be reduced? Maybe using more modern diodes? The input line to line voltage can reach 480 VAC.

I didn't design this. I'm just trying to understand it and probably make it more robust.

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    \$\begingroup\$ This question is a follow-up of Understanding this power supply design \$\endgroup\$ – Huisman Jun 28 at 20:03
  • \$\begingroup\$ Yes, it can be followed there. Sorry for creating another thread. I thought the old one was going to be very long and thus affecting the help rate. \$\endgroup\$ – Blue_Electronx Jun 28 at 20:05
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1- Wouldn't it be better to put the TVS diode in the output of the rectifier?

No. These TVS diodes are to protect M1 which is rated for a max Vds of 1000V. That's why the design has three 300V TVS diodes, so they trigger first.

2- Could the number of diodes be reduced? Maybe using more modern diodes? The input line to line voltage can reach 480 VAC. They probabaly choose three 300V TVS diodes such is 'slightly' below 1000V. Using three TVS diodes also distributes the peak pulse power dissipation.

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  • \$\begingroup\$ Is it a good idea then adding another TVS diodes in parallel with the MOV for better protection? I mean, I won't touch the three TVS diodes, I'm just adding another one after the rectifier. Or is it the MOV enough? \$\endgroup\$ – Blue_Electronx Jun 28 at 20:49

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