I'm using a 24V 3-pahse BLDC motor connected with each phase connected to a low and high side FET (IRL1405). The FET driver is an IR2132 which is controlled by a 6 PWM inputs.
I'm trying to work out the value I need for the bootstrap capacitors when running the driver from 15Vdc.
I have followed the design tip (dt04-04) on the IR site and can figure out most of it. The equation is basically C=Q\V where Q is the sum of the charge required at the FET gate plus all the leakages through the bootstrap diode and stuff. V is the 'minimum voltage drop we have to guarantee when the high side FET is on'. This comprises Vcc (15V), Vf (diode fwd voltage), VGE min (minimum G-E voltage to maintain), VCE ON (CE voltage drop), such that V = Vcc - Vf - VCEon - VGEmin.
Being a low-R FET, VCE is negligible (I think), VF is 1.0V but I'm not sure what VGEMIN is. How do I determine this value? Is it an educated guess or a datasheet value? Or can I just arbitarily choose a desired value for V?
Hopefully that explains the problem sufficiently. I'm not in a position to start changing components but there's not a whole lot to explain this on the net. All the examples use IGBTs (hence the VCE value rather than VDS)
Thanks
scarey
I'm trying to work out the value I need for the bootstrap capacitors when running the driver from 15Vdc.
I have followed the design tip (dt04-04) on the IR site and can figure out most of it. The equation is basically C=Q\V where Q is the sum of the charge required at the FET gate plus all the leakages through the bootstrap diode and stuff. V is the 'minimum voltage drop we have to guarantee when the high side FET is on'. This comprises Vcc (15V), Vf (diode fwd voltage), VGE min (minimum G-E voltage to maintain), VCE ON (CE voltage drop), such that V = Vcc - Vf - VCEon - VGEmin.
Being a low-R FET, VCE is negligible (I think), VF is 1.0V but I'm not sure what VGEMIN is. How do I determine this value? Is it an educated guess or a datasheet value? Or can I just arbitarily choose a desired value for V?
Hopefully that explains the problem sufficiently. I'm not in a position to start changing components but there's not a whole lot to explain this on the net. All the examples use IGBTs (hence the VCE value rather than VDS)
Thanks
scarey