C
Chris Carlen
- Jan 1, 1970
- 0
Greetings:
I am considering to build an H-bridge around a solenoid coil with the
capability of delivering 150V at 30A for up to 500us pulses, followed by
about 40V at 20A (PWMed) for up to about 4.5 ms, with up to about 5%
duty cycle of solenoid pulses (58.5W average power, 4500W peak power).
The H-bridge would be part of a PWM constant current drive, controlling
solenoid current to be proportional to some command voltage. This is a
deisel fuel injector driver. I want to achieve about a 500us current
rise/fall time from 0-30A into a 2ohm 2mH load.
I am looking at a employing four of IRFP260N 200V 50A 0.04ohm 300W
devices. They seem beefy enough to not need to parallel devices.
The question is how to accomplish the high side drive with a 150V B+
rail? I am considering using a DC-DC converter to provide isolated 12V,
and powering a FET driver such as TC4426 with that. The input of the
FET driver would be driven by the output of a fast optocoupler powered
by the DC-DC converter as well. The input to the optocoupler is then
accessible at the ground level, and can turn my FET on and off. The
problem with this is that a bunch of circuitry (the DC-DC output
circuitry, and everything to the right of the optocoupler LED) must
swing with the output voltage. I guess there is nothing inherently
wrong with this, but it must radiate a lot of EMI as well as presenting
capacitance to the output.
Is this the right approach, or is there a better way?
I think it is impossible to use a pulse transformer in this situation,
because there are times when the solenoid must be switched on for a
solid 500us. But I haven't evaluated this option in depth yet, as I
have only recently settled upon the H-bridge approach after realizing
the factors that make a 1/2 bridge impractical, as well as a zener catch
diode approach.
But my intuition as well as a few cursory calculations suggest that any
pulse transformer capable of holding the FET on for 500us would have too
high of an inductance, and thus too high of a leakage inductance, to be
able to turn the FET on and off quickly enough.
Comments appreciated.
Good day!
--
_______________________________________________________________________
Christopher R. Carlen
Principal Laser/Optical Technologist
Sandia National Laboratories CA USA
[email protected] -- NOTE: Remove "BOGUS" from email address to reply.
I am considering to build an H-bridge around a solenoid coil with the
capability of delivering 150V at 30A for up to 500us pulses, followed by
about 40V at 20A (PWMed) for up to about 4.5 ms, with up to about 5%
duty cycle of solenoid pulses (58.5W average power, 4500W peak power).
The H-bridge would be part of a PWM constant current drive, controlling
solenoid current to be proportional to some command voltage. This is a
deisel fuel injector driver. I want to achieve about a 500us current
rise/fall time from 0-30A into a 2ohm 2mH load.
I am looking at a employing four of IRFP260N 200V 50A 0.04ohm 300W
devices. They seem beefy enough to not need to parallel devices.
The question is how to accomplish the high side drive with a 150V B+
rail? I am considering using a DC-DC converter to provide isolated 12V,
and powering a FET driver such as TC4426 with that. The input of the
FET driver would be driven by the output of a fast optocoupler powered
by the DC-DC converter as well. The input to the optocoupler is then
accessible at the ground level, and can turn my FET on and off. The
problem with this is that a bunch of circuitry (the DC-DC output
circuitry, and everything to the right of the optocoupler LED) must
swing with the output voltage. I guess there is nothing inherently
wrong with this, but it must radiate a lot of EMI as well as presenting
capacitance to the output.
Is this the right approach, or is there a better way?
I think it is impossible to use a pulse transformer in this situation,
because there are times when the solenoid must be switched on for a
solid 500us. But I haven't evaluated this option in depth yet, as I
have only recently settled upon the H-bridge approach after realizing
the factors that make a 1/2 bridge impractical, as well as a zener catch
diode approach.
But my intuition as well as a few cursory calculations suggest that any
pulse transformer capable of holding the FET on for 500us would have too
high of an inductance, and thus too high of a leakage inductance, to be
able to turn the FET on and off quickly enough.
Comments appreciated.
Good day!
--
_______________________________________________________________________
Christopher R. Carlen
Principal Laser/Optical Technologist
Sandia National Laboratories CA USA
[email protected] -- NOTE: Remove "BOGUS" from email address to reply.