kinarfi
Well-Known Member
I did email IR about my problem, thought you all might like to read the reply,
Subject
irf3205
Discussion Thread
Response Via Email 06/25/2014 04:55 PM
Hello Jeff,
There should be current limiting resistors connected to the gate of the mosfet's always. 10-20 ohms. current from NE555 is 200mA. if a 10 ohm resistor is selected. I^2xR = .2x.2x10 = 0.4 W 10 ohm resistors can be used. Gate resistors are always important or the mosfet's can be damaged. They limit the current and also make sure there is no transient spike coupled at the gate.
Best Regards,
Kali
Applications Engineer
Technical Assistance Center
International Rectifier
THE POWER MANAGEMENT LEADER
Customer By Web Form (Jeff )06/25/2014 10:06 AM
I have 19 dead IFR3205 in my hand and I have probably thrown that many away, the markings are
IRF3205
I R P138
B9P0
Death was determined with a diode check using a Fluke multi meter and the Vgs usually read near 0 volts, as did the Vds ad Vgd, regardless of polarity
I've tried multiple gate drivers, IR2110, totems, and last try was the output of a ne555, but my IRF3205s keep dying, Last kill was, using the uploaded drawing, apply the PWM to a gear motor, 12v 185 watt, one shaft having a sensor similar to a Wheatstone bridge and the other shaft is power output. I held the output with some pliers a while turning the input shaft and watched the current from my power supply, with 2 IRF3205s in parallel, I should have over powered the supply and should not have been able to stop the gear motor, instead, at about 15 amps, one of the IRF3205s failed shorted, again!
This cause the gear motor to catch up and pass the input signal and then it reversed because it passed the input and it bounces back and forth until I can get free.
These are 110 amp FETs and shouldn't be dying at 15 amp,
One question I have is are these your product or did I get a knock off?
Can you suggest a design change suggestion or any help.
Thanks you,
Jeff
So, I'll be adding a resistor to the gate of this and all future designs, an omission that was pointed out earlier in this thread.
Subject
irf3205
Discussion Thread
Response Via Email 06/25/2014 04:55 PM
Hello Jeff,
There should be current limiting resistors connected to the gate of the mosfet's always. 10-20 ohms. current from NE555 is 200mA. if a 10 ohm resistor is selected. I^2xR = .2x.2x10 = 0.4 W 10 ohm resistors can be used. Gate resistors are always important or the mosfet's can be damaged. They limit the current and also make sure there is no transient spike coupled at the gate.
Best Regards,
Kali
Applications Engineer
Technical Assistance Center
International Rectifier
THE POWER MANAGEMENT LEADER
Customer By Web Form (Jeff )06/25/2014 10:06 AM
I have 19 dead IFR3205 in my hand and I have probably thrown that many away, the markings are
IRF3205
I R P138
B9P0
Death was determined with a diode check using a Fluke multi meter and the Vgs usually read near 0 volts, as did the Vds ad Vgd, regardless of polarity
I've tried multiple gate drivers, IR2110, totems, and last try was the output of a ne555, but my IRF3205s keep dying, Last kill was, using the uploaded drawing, apply the PWM to a gear motor, 12v 185 watt, one shaft having a sensor similar to a Wheatstone bridge and the other shaft is power output. I held the output with some pliers a while turning the input shaft and watched the current from my power supply, with 2 IRF3205s in parallel, I should have over powered the supply and should not have been able to stop the gear motor, instead, at about 15 amps, one of the IRF3205s failed shorted, again!
This cause the gear motor to catch up and pass the input signal and then it reversed because it passed the input and it bounces back and forth until I can get free.
These are 110 amp FETs and shouldn't be dying at 15 amp,
One question I have is are these your product or did I get a knock off?
Can you suggest a design change suggestion or any help.
Thanks you,
Jeff
So, I'll be adding a resistor to the gate of this and all future designs, an omission that was pointed out earlier in this thread.