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Gate Driver ICs Forum Discussions

User15925
Level 1
Level 1
Hi,

I have a 6EDL04N06PT connected to 6x STF10N60DM2 MOSFETS, the design is used in a BLDC Inverter. I have the PWM operating in an open loop mode and I'm using this to qualify the MOSFET switching times.
I have a resistor load from the phase to GND, which is 820R for this test. The VDC bus is 30V (although it will be used at 100V) and my VCC is 16V.
I have removed all gate resistors so there is some slight ringing.
I have 100nF of boot strap capacitor.


The diagram below shows my setup, with the scope channel colours circled.
3292.attach

The scope capture below shows the following:
D0 and D1 are the PWM 1H / PWM 1L Inputs
Yellow is the gate voltage at the Lower FET
Purple is the gate voltage at the Upper FET
Blue is the phase voltage.
White is the Upper FET Vgs (math)

3293.attach

I can clearly see that the phase voltage remains at VDC and decays through the load resistor when the High side MOSFET is switched off. There is a significant amount of energy in this system, and during the low side switch-on (yellow) the remaining energy in the phase drops to zero creating a significant transient.

I feel that the upper MOSFET is actually switched off (based on the Vgs < Vth of 4.0V) and there is no capacitance or inductance anywhere in my circuit that would cause this type of issue.


My questions are:

1. Is the gate driver actually turning the upper FET off?

2. Is there something in the bootstrap circuit that would store sufficient energy to cause this problem?

Thanks
SafetyLok
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1 Solution
Srivatsa
Moderator
Moderator 5 sign-ins 50 replies posted 25 solutions authored
Moderator
Yes, the COM pin and VSS pin can be joined together.

The 6EDL04N06PT can be used with 3 current shunt resistors.

In this case the ITRIP pin of 6EDL04N06PT can be used to detect current from one current shunt resistor only.

View solution in original post

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3 Replies
IrisLi
Employee
Welcome! First reply posted First solution authored
Employee
Please firstly try to measure the VBS voltage (between VB1 pin and VS1 pin) with a differential probe to see if this voltage is lower than UVLO level, if yes, then it trigger UVLO protection, the high side will be off.
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User15925
Level 1
Level 1
Thanks,

I have checked the VB-VS and its well above the UVLO voltage at all times.

Can you advise me if the 6EDL04N06PT is able to be used with 3 current shunt resistors? (i.e. the COM pin and VSS pin joined).

Thanks.
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Srivatsa
Moderator
Moderator 5 sign-ins 50 replies posted 25 solutions authored
Moderator
Yes, the COM pin and VSS pin can be joined together.

The 6EDL04N06PT can be used with 3 current shunt resistors.

In this case the ITRIP pin of 6EDL04N06PT can be used to detect current from one current shunt resistor only.
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