Hey guys,
Workin on a project requiring a bi-polar current flow of rediculously high pulse (~80A). A high-force solenoid actuator if you must know. Everything from the uC down to the solenoid works perfectly, but only below 14V. The coil/driver circuit resistance requires at least 19V and we're running 2x 11.1V lithium poliymer batteries for the pulse source.
Basically! our problem lies on the PMOS in the H-brigde. Set up correctly it operates exactly as expected with 1 of the 11V batteries but goes on fire with 2. Using a programmable source we've established that it heats up violently fast at ~13.9V, even with low current (1k load resistance for testing).
The MOSFET's used are the STP80PF55 series, rated at Ids max = 80A (320A pulse) and Vgs max = 16V, Vds max = 55V @Vgs=0, thus Vgate can handle up to 55V??
Our original fault was forgetting about the Vgs max rating so then implimented a simple NMOS, through a potential divider, regulation of the gate voltage on the PMOS. This works as expected giving a ratio and keeps Vgs controllable, but when the ratio is set so the voltage needs to be above 14V to trigger the PMOS threshold, it heats up insanely fast when it begins to turn ON, even though the Vgs drop still remains only 4V.
I've thrown together a basic schematic on free software I have at home so no home made libraries/simulations but I really need help, sick of burning my fingers tbh lol.
Basic schematic
The gate inputs are driven by the uC through an optically isolated source of 5V, thus the voltage at the MOS gate don't have a common ground with the Drain/Source (doesnt seem to be a problem below 14V). The variable resistor merely represents the solenoid load.
Links to MOS data sheets.
PMOS
http://www.st.com/stonline/products/literature/ds/8177/stp80pf55.pdf
NMOS
http://www.farnell.com/datasheets/52363.pdf
Pretty much ran out of ideas, hope you can help.
Gratefully,
Sev
Workin on a project requiring a bi-polar current flow of rediculously high pulse (~80A). A high-force solenoid actuator if you must know. Everything from the uC down to the solenoid works perfectly, but only below 14V. The coil/driver circuit resistance requires at least 19V and we're running 2x 11.1V lithium poliymer batteries for the pulse source.
Basically! our problem lies on the PMOS in the H-brigde. Set up correctly it operates exactly as expected with 1 of the 11V batteries but goes on fire with 2. Using a programmable source we've established that it heats up violently fast at ~13.9V, even with low current (1k load resistance for testing).
The MOSFET's used are the STP80PF55 series, rated at Ids max = 80A (320A pulse) and Vgs max = 16V, Vds max = 55V @Vgs=0, thus Vgate can handle up to 55V??
Our original fault was forgetting about the Vgs max rating so then implimented a simple NMOS, through a potential divider, regulation of the gate voltage on the PMOS. This works as expected giving a ratio and keeps Vgs controllable, but when the ratio is set so the voltage needs to be above 14V to trigger the PMOS threshold, it heats up insanely fast when it begins to turn ON, even though the Vgs drop still remains only 4V.
I've thrown together a basic schematic on free software I have at home so no home made libraries/simulations but I really need help, sick of burning my fingers tbh lol.
Basic schematic
The gate inputs are driven by the uC through an optically isolated source of 5V, thus the voltage at the MOS gate don't have a common ground with the Drain/Source (doesnt seem to be a problem below 14V). The variable resistor merely represents the solenoid load.
Links to MOS data sheets.
PMOS
http://www.st.com/stonline/products/literature/ds/8177/stp80pf55.pdf
NMOS
http://www.farnell.com/datasheets/52363.pdf
Pretty much ran out of ideas, hope you can help.
Gratefully,
Sev
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