TVS protection for hi side IGBT in SMPS?

• TVS protection for hi side IGBT in SMPS?
  Posted by Faringdon on 15 Jan, 2022 22:43
• Hi,
  If you have a 3.6kW Half Bridge SMPS, using IXER35N120 IGBTs (fsw = 20kHz) .......then is the P6KE18CA TVS going to be good enough to protect the IGBT Gates from transient overvoltages?
  The Abs Max of the gate voltage is 20V.
  
  IXER35N120   IGBT
  https://www.mouser.es/datasheet/2/240/l518-1548005.pdf
  
  P6KE18CA   TVS
  https://www.littelfuse.com/media?resourcetype=datasheets&itemid=3ba2705e-3e6f-49cc-b247-92bd0aed9fd5&filename=littelfuse-tvs-diode-p6ke-datasheet
  
  Is it  right that we are to consider that  P6KE18CA's  TVS current goes linearly  from 1mA at 18.9V  to 24.2A at 25.2V?
  If this was the case, then at 20V, the  P6KE18CA TVS would conduct up to 4.2A
• #1 Reply
  Posted by T3sl4co1l on 15 Jan, 2022 23:58
• What transient voltages?
  
  Tim
• #2 Reply
  Posted by David Hess on 16 Jan, 2022 00:56
• Quote from: Faringdon on 15 Jan, 2022 22:43

  If you have a 3.6kW Half Bridge SMPS, using IXER35N120 IGBTs (fsw = 20kHz) .......then is the P6KE18CA TVS going to be good enough to protect the IGBT Gates from transient overvoltages?

  
  Assuming that you are driving the gate to full saturation with 15 volts, sure, the P6KE18CA will work fine.
  
• #3 Reply
  Posted by Faringdon on 16 Jan, 2022 11:41
• Quote

  What transient voltages?

  Thanks, its just the general "malaise" thats going to find its way through the IGBT stray junction capacitances and potentially blow up the gate.
  
  

  Quote

  Assuming that you are driving the gate to full saturation with 15 volts, sure, the P6KE18CA will work fine.

  Thanks, it seems amazing that this P6KE18CA can only draw 1mA with 18.9V across it, then with 20V across it it can draw 4.2A.
  
  I wonder how a zener in the same package would perform?
  
  
• #4 Reply
  Posted by David Hess on 16 Jan, 2022 14:31
• Quote from: Faringdon on 16 Jan, 2022 11:41

  Thanks, it seems amazing that this P6KE18CA can only draw 1mA with 18.9V across it, then with 20V across it it can draw 4.2A.
  
  I wonder how a zener in the same package would perform?

  
  A zener would work the same since they are essentially the same thing.
  
• #5 Reply
  Posted by T3sl4co1l on 16 Jan, 2022 18:05
• Quote from: Faringdon on 16 Jan, 2022 11:41

  Quote

  What transient voltages?

  Thanks, its just the general "malaise" thats going to find its way through the IGBT stray junction capacitances and potentially blow up the gate.
  

  
  That's why you don't take inverter designs from Jimmy Carter.  Mine simply don't do that...
  
  Such an element might be gainfully employed to protect the gate driver, such as in a modular system where the drivers are relatively expensive, and IGBT destruction can't be avoided through other means (or multiple layers of protection are desired).
  
  Tim
• #6 Reply
  Posted by jonpaul on 16 Jan, 2022 20:09
• Bonjour David: A TAZ is a large area Zener specifically rated and tested on standard pulses with defined wave shape, current etc.
  
  TAZ have specified clamp V and certain currents, but cannot dissipate long-term. The large die in a small package was developed at General Semi decades ago. Yes they are Zeners but not interchangeable!
  
  In the case of gate protection, a TAZ is not usually needed and a Zener can serve as the current is limited by the driver.
  
  Beware of the Zener shunt capacitance on the driver performance.
  
  Bon chance
  
  Jon