ISO5851-Q1: Use gate driver DESAT method in 800V line

morgan nedelec BS

Part Number: ISO5851-Q1
Other Parts Discussed in Thread: ISO5851

Hi,

I would like to use the ISO5851-Q1 to control an IGBT on a 800V line with just a heating resistance on it.

In case of CC of the resistance, I want to use the DESAT function to open the line.

But I can't find in the datasheet the dimensioning of the DESAT funciton, in particular the Ddesat: must this one have a reverse voltage of 800V in my application ?

Thanks in advance,

M. NEDELEC

over 6 years ago

0 Xiong Li over 6 years ago

TI__Intellectual 1665 points

Hi,

A HV diode is usually used to block the high voltage to be applied to the driver IC. Please refer to Fig. 49 in the datasheet for more info. Let us know of further concerns.

With Regards,

Xiong

0 morgan nedelec BS over 6 years ago in reply to Xiong Li

Prodigy 105 points

Hi,

Thank you for your answer,

I've another concern about the gate resistor : in a discret application of the driver (ie no frequence on Finp), how to choose the Rg ? Typically 10 Ohms, as the datasheet, but can we increase the value (like 100 Ohms to lower the consumption ) ?

Thank you in advance,

Morgan

0 Xiong Li over 6 years ago in reply to morgan nedelec BS

TI__Intellectual 1665 points

Hi Morgan,

The selection of the gate resistor depends on how fast you want to switch the power transistor. The resistor value needs to be smaller if you want to switch faster and vice versa.

With Regards,

Xiong

0 morgan nedelec BS over 6 years ago in reply to Xiong Li

Prodigy 105 points

Hi Xiong,
I understand that but how can the gate resistor should be calibrated in my case where I don't have a switching frequency (or, let's say, 1Hz at max) ?

Thank you,

Morgan

0 Xiong Li over 6 years ago in reply to morgan nedelec BS

TI__Intellectual 1665 points

Hi Morgan,

You can size the gate resistor based on how fast you want the switch to be switched. For your application, I think it should be OK to use relatively smaller gate resistor to have faster response since thermal is not a concerns as the switching frequency is so low.

With Regards,

Xiong

0 morgan nedelec BS over 6 years ago in reply to Xiong Li

Prodigy 105 points

Hi Xiong,

I was more thinking about putting a greater resisance (1kOhm), in order to reduce the power comsumption, is that judicious?

I was wondering if it was recommended in my cae to use the ISO5851 in unipolar or in bipolar mode ?

Morgan

0 Xiong Li over 6 years ago in reply to morgan nedelec BS

TI__Intellectual 1665 points

Hi Morgan,

The power consumption is not much as the frequency is so low. Please refer to section of 10.2.2.9 of the datasheet for more details. Both unipolar and bipolar should work for your case. It is recommended to use Miller clamp function when unipolar power supply is used.

With Regards,
Xiong

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ISO5851-Q1: Use gate driver DESAT method in 800V line