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Old 12th January 2012, 05:58 PM   #11
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I highly suggest you powered the gates from ground and -12V for direct interfacing the IR2011.
Note that in this case -12V will be a logic zero and ground will be logic one.
What is more, take advantage of open collector output of the comparator and connect the pullup resistor to ground.
To create some dead time use RDC networks.
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Old 12th January 2012, 06:17 PM   #12
gmarsh is offline gmarsh  Canada
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^- this

Power the gate and IR2110 from ground and -12V. The IR2110 will only tolerate a few volts between signal ground and low side ground.
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Old 12th January 2012, 06:18 PM   #13
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Quote:
Originally Posted by darkfenriz View Post
I highly suggest you powered the gates from ground and -12V for direct interfacing the IR2011.
Note that in this case -12V will be a logic zero and ground will be logic one.
What is more, take advantage of open collector output of the comparator and connect the pullup resistor to ground.
To create some dead time use RDC networks.
Hi darkfenriz

I took the advice which gmarsh gave me same as yours.

VDD = 0v
VSS = -12V
Propergation Delay 100ns @ 15Vdd

Max operating supply is VDD18Vmax with reference to VSS -0.5v so im well within the safe operation range.

I'm busy evaluation the gate drive circuity and just downloaded IR2110 application notes and accompanied datasheet.
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Old 12th January 2012, 06:21 PM   #14
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Another thing is forget the IRF640 and the likes stuff.
These are planar devices, completely unsuitable for fast switching. Get modern trench-technology MOSFETs
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Old 12th January 2012, 06:30 PM   #15
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Quote:
Originally Posted by darkfenriz View Post
Another thing is forget the IRF640 and the likes stuff.
These are planar devices, completely unsuitable for fast switching. Get modern trench-technology MOSFETs
For now that's all i have on the bench its not actually a fixed output stage solution, i have a mosfet guide EVA has posted sometime ago various various devices see below.

Quote:
IRFP240 are ancient MOSFET only useful for burning watts in ancient linear amplifier designs. If you have some, they should be easy to sell to people doing class AB or A.

Some of my favourite ones for class D are:

- IRF540Z for 100V (nothing to do with other IRF540 variants)
- IRFB4321 for 150V
- IRFB4227 for 200V

This selection is aimed towards low conduction losses at the expense of higher gate drive requirements, but of course there are "lighter" ones intended for easy drive:

- IRFB4212 (100V)
- IRFB4019 (150V)
- IRFB4020 (200V)

Similar MOSFET from Fairchild are worth mentioning too, since some of them may outperform the ones from IR in certain circumstances (but others are ovbiously inferior):

- FDP3632, FDP3652, FDP3682 (100V)
- FDP2532, FDP2552, FDP2572 (150V)
- FDP2614 (200V)


Low Rds and low gate charge are 2 of the primary factors to consider. The third is VDSmax...Maximum drain to source voltage. The devices you mention are only 100V parts. A good rule of thumb is to use parts rated for Vcc + Vee + some safety factor to handle the inductive output load. So 100V parts should maybe only used with +/-33V rails. You might be able to push it a little higher, but you'll have to check what the reverse recovery spikes look like with a scope to make sure you're still saft.

If that works for you, then you'll have to look at balancing power losses from Rds in the output stage (twice as large for the STP40 device) vs. power losses and heating in your gate driver due to the much larger Qg of the STP80 device vs. the STP40 device. Keeping in mind that the gate driver is not typically mounted to a very robust heatsink compared to the output devices.

I hope this helps you out a little bit.

We have done a lot of research. The best Mosfets for Class D are those which have low gate charge, however if you are using either a driven or self oscillating type, higher Qg types will work as long as you pay attention to dead time.

IRFB4212 100v 0.058R 15nc
IRFB4019 150v 0.08R 13nc
IRFB4020 200v 0.08R 21nc
IRFB23N15D 150v 0.09R 37nc
IRF540N 100v 0.044R 71nc

FDP39N20 200v 0.066R 38nc
FDP42AN15A0 150v 0.042R 33nc
FDP3682 100v 0.036R 18nc
FDP3652 100v 0.016R 41nc

I have tried all the above. The IRF540N is the least expensive and the Fairchild FDP3652 the most. I can obtain low THD numbers with any of tghe FETS, bit of course the lower the gate charge the lower the deadtime and the coller the FETs run.

RDs on is not a huge thing as typically you are not driving the FET to its current limits.
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Old 12th January 2012, 10:11 PM   #16
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Generally the lower the Vds the better, that's the trade-off in mosfets. It is not a tough task to find a 30V or even a 55-60V device, which outperforms any of the above in every aspect aside from a fact it is rated for lower drain-source voltage.
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Old 12th January 2012, 11:10 PM   #17
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Quote:
Originally Posted by gmarsh View Post
^- this

Power the gate and IR2110 from ground and -12V. The IR2110 will only tolerate a few volts between signal ground and low side ground.
I'm only getting an output on LO pin-1of the gate driver , output H-out PIN-7 is dead ive checked both hi-in and low-inputs are signaling modulation out of phase and swinging between +100mV and -12v respectively from the XOR gates.

Any guide wiring up the gate driver ? the supply on the gate driver are 0Vss and +Vcc 0 volts.
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Old 12th January 2012, 11:32 PM   #18
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Check Vb/Vs capacitor is getting properly charged. Also you could have just plain blown the IR2110 from having it hooked up wrong earlier.
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Old 13th January 2012, 06:46 AM   #19
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Quote:
Originally Posted by gmarsh View Post
Check Vb/Vs capacitor is getting properly charged. Also you could have just plain blown the IR2110 from having it hooked up wrong earlier.
Can you please show me a diagram with the wiring of a IR2110 running with supply rails 0V and -Vcc.

Thanks.
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Old 13th January 2012, 12:54 PM   #20
gmarsh is offline gmarsh  Canada
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Won't make a diagram, but:

VSS/COM/SD = connected to -12V rail
LIN/HIN = from XOR gate
VDD, VCC = conneted to GND rail
VS = connected to junction of both FETs
VB = connected to VS through a capacitor, and connected to GND through a diode - anode to GND, cathode to VB.
LO/HO = to output FETs.
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