Hi,
I am building a high voltage flyback driver circuit for an electrostatic sprayer concept that I am experimenting with. I successfully constructed the circuit with an IRLZ44N logic level MOSFET and was able to drive it directly with a 5v Arduino PWM output. However, inspection showed that the drain-to-source voltage can be in excess of hundreds of volts which exceeds the IRLZ44N's V_ds_max voltage of 60v.
Therefore, I decided to implement a MOSFET with a higher V_ds_max. No logic-level MOSFET's were available at the ratings I am looking at, so I decided to use a MOSFET driver.
Here's a description of my circuit to accompany the attached schematic:
- the circuit is powered by a 3.7v 18650 battery
- A TPS61040-based 12v boost converter (Adafruit) boosts the battery voltage to 12v
- The 12v is fed into the gate driver along with a couple of decoupling caps to provide local high current source
- The gate driver accepts a PWM control signal from a 3.3v GPIO on an Arduino/STM32
- The gate driver switches the MOSFET which interacts with a flyback transformer in a typical flyback driver arrangement.
I acquired a plethora of MOSFET's to test with. I found that some MOSFET's worked in the circuit and resulted in an arc, while others failed to produce an arc.
- Worked: IRLZ44N, IRFZ44N, IRF510N, IRF520N, IRF530N, IRF540N, IRF640N, IRF3205
- Did not work: SIHU2N80AE-GES, IRF840HPBF, IRF840BPBF, IRF740N, IRF840N
What I've tried:
- The MOSFET's that did not work tended to have higher V_ds_max ratings, but I didn't spot any other significant differences in the datasheet.
- I verified that the gate driver was producing a clean pulse above R_ds_on voltage for both working and not-working MOSFET's.
- I measured the current draw from the battery and noted that working MOSFET's drew about 1.6A while not-working MOSFET's drew 0.8-1A
- I scoped the MOSFET drain pin and noticed a significant difference in the output waveforms.
What characteristic am I missing that determines if a MOSFET will function as expected to drive the flyback circuit?