hi,
i'm pretty much an electronics novice
i'm trying to drive some N channel mosfets from a 3.3v arm mcu (stm32), the actual mosfets are really basically the RepRap Ramps1.4 heater mosfets.
However, based on the specs, the turn on gate source voltages is at least 4.5 volts as seen in various data sheets. Hence, to model a possible interface i made a schematic with something equivalent IRFZ44N as the N channel power mosfet. I'm skipping the logic level power mosfets that can run at 3.3v as i observed that they are expensive on ebay / aliexpress etc.
The idea here is i drive input A from the gpio pin, and R1 (100 ohm, but in reality i think it may be just a few ohms as that is the heater hotend heating cartridge) is the load.
i used a PNP transistor (Q2 2n2904 - the part number in the image is incorrect) at the gate and another NPN transistor (Q1 2n2222) to drive the NPN transistor. i did a though experiment / analysis and figure that Q1 NPN should be off at the start (assuming that the input is floating or low), that should keep Q2 PNP off, which in turns keeps Q3 the n channel power mosfet off. i've initially started with just a single NPN transistor, but the level/logic inversion is a problem as it leaves the mosfet switched on right at the start.
if i raise A to 3v (i should probably have placed a series transistor), i figure that the 3 transistors will be switched on.
do this circuit make sense or do you have any comments about this?
i'm actually also thinking about the IR2109 half bridge driver in which the parts are rather inexpensive on aliexpress
https://www.infineon.com/dgdl/ir2109.pdf?fileId=5546d462533600a4015355c7e85b1679
however, i'm not too certain about the implications if i simply leave the high side unconnected. i.e. just use the low side to drive the mosfet.
would there be any advantage using a IR2109 rather than discrete bipolar transistors as such?
the actual part i'm interfacing is the heaters section in the 2nd image attached.
i'm pretty much an electronics novice
i'm trying to drive some N channel mosfets from a 3.3v arm mcu (stm32), the actual mosfets are really basically the RepRap Ramps1.4 heater mosfets.
However, based on the specs, the turn on gate source voltages is at least 4.5 volts as seen in various data sheets. Hence, to model a possible interface i made a schematic with something equivalent IRFZ44N as the N channel power mosfet. I'm skipping the logic level power mosfets that can run at 3.3v as i observed that they are expensive on ebay / aliexpress etc.
The idea here is i drive input A from the gpio pin, and R1 (100 ohm, but in reality i think it may be just a few ohms as that is the heater hotend heating cartridge) is the load.
i used a PNP transistor (Q2 2n2904 - the part number in the image is incorrect) at the gate and another NPN transistor (Q1 2n2222) to drive the NPN transistor. i did a though experiment / analysis and figure that Q1 NPN should be off at the start (assuming that the input is floating or low), that should keep Q2 PNP off, which in turns keeps Q3 the n channel power mosfet off. i've initially started with just a single NPN transistor, but the level/logic inversion is a problem as it leaves the mosfet switched on right at the start.
if i raise A to 3v (i should probably have placed a series transistor), i figure that the 3 transistors will be switched on.
do this circuit make sense or do you have any comments about this?
i'm actually also thinking about the IR2109 half bridge driver in which the parts are rather inexpensive on aliexpress
https://www.infineon.com/dgdl/ir2109.pdf?fileId=5546d462533600a4015355c7e85b1679
however, i'm not too certain about the implications if i simply leave the high side unconnected. i.e. just use the low side to drive the mosfet.
would there be any advantage using a IR2109 rather than discrete bipolar transistors as such?
the actual part i'm interfacing is the heaters section in the 2nd image attached.