Easy gate driver testing - FOD3120V, IGBT, MOSFET

Easy Gate Driver is one of the product designed by me to ease the research and development in power electronic.

It is useful for the people who just started on machine drive, power converter and power inverter.

I have decide it is the best for me to write on blog before migrate it to my website. (testing purpose and getting feedback)

My gate driver allow the changing of optocoupler which enable replacement when it is spoiled, also it has given me to try out various optocouplers in the market.

My two favourite optocouplers so far are Vishay VO3120 and Fairchild FOD3120V. The reason behind is always good performance over price ratio.

Avago Technology had wide selections of gate drive optocouplers but the price always higher than the other manufacturers in same specifications.

Below is the pictures of my gate driver, I named it Easy Gate Driver, meaning it is easy to use.

It is able to drive two independent channels of PWM which make it suitable for synchronous switching DC converter (buck converter and boost converter) or controlling two independent DC converters. Best of all, it can be cascaded to drive multiple phase / multiple level inverter.

Two type of popular power transistor are MOSFET and IGBT, so I will use these two type for testing purposes.

I had chosen three power transistor from element14, the price range is from RM5 to RM10.

First:

Second:

Third:

The optocoupler used in this testing is FOD3120V.

BTW, I really like element14 packaging when they kept the IC in small boxes. The boxes are reusable for keep small electronic components.

Results:
I am using PIC18f4553 to generate PWM. (Dual Mode)

1. No load waveform. (40kHz)

I generated two inverted PWM signal with duty cycle of 50%. 

The output signal voltage is +15V and -5V, the negative bias is added to reduce the switch off time.

2. First load testing. (IGBT, SINGLE, 1.55V, 32A, TO-247AD)

3. Second load testing. (IGBT, 600V, 34A, TO-220)

4. Third load testing. (MOSFET, N-Channel, 600V, 19.3A, TO-220FP-3)

Much to my surprise the rise time and fall time of MOSFET is much higher than IGBT. After checking the datasheet, page 5, the rise time, fall time as follow:

Turn-on delay time td(on)	11ns
Rise time tr	9ns
Turn-off delay time td(off)	71ns
Fall time tf	9ns

Way lower than my testing, but gate resistance used by INFINEON also much slower (3.4 ohm) which higher gate current to charge the gate capacitance.

Conclusion:

Gate resistance has effect on the rise time and fall time, lower gate resistance allow higher current to charge the gate capacitance, thus the rise time is much faster. 

The negative bias is added to allow the gate capacitance to discharge faster thus the fall time also much lower.

NOTE:

I may have make a mistake by mixing up the results of mosfet and igbt (very unlikely),

nevertheless, it is proven, the Easy Gate Driver able to drive MOSFET and IGBT.