• State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 3 answers
  • Subscribers 41 subscribers
  • Views 985 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TIDA-00195: Snubber protection of the IGBT switch

Rajasekaran
Intellectual 945 points
Part Number: TIDA-00195

Dear sir,

In general we will use snubber capacitors for the IGBT protection while using inductive loads. But there is no snubber capacitor or any other snubber capacitor is used for the IGBT protection in TIDA-00195. 

Could you please tell me, how the IGBT switch is protected against inductive loads for the inverter?

also we are planning to use  FP75R12KT4. Do we required snubber protection for this IGBT.? Kindly confirm the same.

Thanks & regards,

Rajasekaran

  • 0
    TI__Prodigy 640 points

    Hi Rajasekaran,

    Thanks for the question. The voltage overshoot during turn-off is caused by the parasitic inductance and not the load inductance since the load current continues to flow without interruption through the free-wheeling diode. In TIDA-00195, the parasitic inductance is kept to a minimum by using IGBT module(reduces parasitic inductance between emitter/collector and switch node) with all-in-one packaging and by optimal placement and layout of the DC link capacitors. Additionally, overshoot can also be reduced by slowing down turn-off by increasing gate resistance. 

    As far as the part you have mentioned is concerned, snubber requirement will depend on system design - parasitic inductance depends on layout to a great extent. If high switching speeds are preferred, it is safer to add decoupling capacitors or R-C snubbers across IGBTs for protection.

    Regards

    Siva

  • 0 in reply to Siva Mohan
    Intellectual 945 points

    Dear sir,

    Thanks for your answer.

    We are trying to place the DC link capacitors as close as possible to the IGBT module in the PCB layout. 


    As recommended, we will add 1uF /1000V capacitor as snubber between DC + and DC - (top switch collector and bottom switch emitter terminals) of each leg. 

    Could you please suggest the procedure to calculate the RC snubber values either across the IGBT switch or leg.

    Thanking you. 


    Thanks & regards,

    Rajasekaran.

  • 0 in reply to Rajasekaran
    TI__Prodigy 640 points

    Hi,

    Energy in the capacitor is (0.5 * C * V^2). Energy in the parasitic inductance is (0.5 * Lp * Imax^2). These two should be equal wherein V in capacitor energy equation is (Vpk- Vdc), where Vpk is the maximum ringing voltage to be allowed and Vdc is the max. DC link voltage. Typically R is sized to limit the peak current during discharge(turn-on). Please note that this for a RCD snubber where diode charges the capacitor during turn-off and R discharges capacitor during turn-on. Use of snubbers reduces voltage overshoot at the cost of higher losses.

    Please refer to relevant literature for a more detailed design and analysis of snubbers.

    Regards

    Siva