Re: Why did my drive blow up?
- From: "Alex Gibson" <news@xxxxxxxx>
- Date: Sun, 5 Mar 2006 10:56:30 +1100
"BRW" <bennet@xxxxxxxxxxxxxxxxxx> wrote in message
news:1141150436.659494.57660@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
My first attempt at building a high-current H-bridge failed miserably.
I was trying to drive a pair of windshield wiper motors on a robot with
a new H-bridge that I built using discrete MOSFETs (HRF3205) with
HIP4081A drivers. I got the design from a Nuts & Volts article. One of
the MOSFETs literally exploded. I don't think it was a build problem
since my friend built a drive from the same design and tested it
completely with a small motor. Two of his MOSFETs exploded when
connected to the big motors.
The only thing I can think that would have caused this is flyback
voltages that the MOSFET zener diodes did not suppress. I thought that
the zener diodes built into the MOSFETs would protect the circuit from
flyback voltages (so did the author of the Nuts & Volts article). Maybe
these built-in diodes are only effective for small loads.
Am I right about the cause for explosion? If I need to add diodes for
flyback suppression, how should I size them? I'm building this drive to
handle 20A.
Thanks,
BRW
Didn't do my trick from a few years back ?
driving a largish motor, fine when taking the load
but when the load drove the motor
the control board (not the driver board)
started smoking and the chip I was using (8051) melted.
Feedback path was the ground link between the boards
and local chasis ground in the box I had them in.
Driver board still works.
Just waiting on some new high current h bridges from bdmicro.com
Brian hasn't got them listed on his site yet
but you can see them here
http://www.bdmicro.com/include/display_image.php?img=rx50-4_sm.jpg
and here http://www.bdmicro.com/darpa-gc/
specs are
* 5 to 24 Volts (30V absolute max)
* Current: 8 to 10 Amps no heat sinks
40 to 50 Amp w/good heat sinks
(upper end not yet determined)
* mounting holes for standard 60mm CPU-type fan for extra cooling
capacity
* header to power fan (uses motor supply voltage)
* PWM freq over 100 kHz
* adaptive non-overlapping gate drive - eliminates shoot-thru
* built-in ATO style fuse
* locked anti-phase control native, sign magnitude / synchronous
rectification possible with adapter logic board (included)
* 5 LED indicators
* solid 4-layer board w/large power and ground planes
* 2.5 x 2.6 inches
* easy to use FAST-ON blade type connectors for power
* convenient screw terminals for logic
.
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