Tried the TC1411NCPA MOSFET driver.  Works nicer -- at a quick glimpse=20
on the scope, there isn't the major off-time as before with the=20
pull-down resistor I was using.  And it seems to be running cooler,=20
though I have to measure that for sure.  So far, all looks good.

Cheers,
-Neil.


On 10/9/2015 9:41 AM, Neil wrote:
> Joe,
>
> Going through these, thanks.  So far, yes I've calculated the off time
> will be significantly longer than the on time, so I'm looking into
> MOSFET drivers now.  I found a TC1411NCPA in a Microchip sample pack I
> got several years ago, and thinking it would be good for an experiment.
>
> Cheers,
> -Neil.
>
>
> On 10/8/2015 7:23 PM, IVP wrote:
>>> The input to the MOSFET is driven by a PNP transistor with a 1k
>>> pull-down resistor -- should I change that to a push-pull setup?
>> Hi Neil,
>>
>> An NPN will ground [discharge the internal capacitances) faster
>>   =20
>> Power MOSFET Basics: Understanding Gate Charge
>> and Using it to Assess Switching Performance
>>
>> http://www.vishay.com/docs/73217/73217.pdf
>>
>> Power MOSFET Basics
>>
>> http://www.irf.com/technical-info/appnotes/mosfet.pdf
>>
>> The advantage of using [the] gate charge [figure] is that the designer
>> can easily calculate the amount of current required from the drive
>> circuit to switch the device on in a desired length of time because
>> Q =3D CV and I =3D C dv/dt, the Q =3D Time x current. For example, a
>> device with a gate charge of 20nC can be turned on in 20usec if 1ma
>> is supplied to the gate or it can turn on in 20nsec if the gate current =
is
>> increased to 1A. These simple calculations would not have been
>> possible with [an] input capacitance value
>>
>> Joe
>>
>>
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15
>>

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