Need help switching (12VDC @ 6amps) and (110VAC @ 17.27 Amps)

[Stephen]

I'm in need of some relay or power mosfet guidance. I need to be able
to switch the following loads (on and off) using a microcontroller:

1. 6.0 amps at 15V DC.
2. A 1900W device running off of 110VAC (I'm assuming 17.27 Ampsrms or
49 amps peak-peak).

All of my experience have been with currents < 500mA! Could anyone
recommend a strategy for this? I would think that some of the power
mosfets from IRF would be suitable for #1. I don't know anything about
relays, but I'm assuming that one would be necessary for #2.

Any advice would be greatly appreciated.

Thanks
Stephen

 

[Winfield Hill]

Stephen wrote...

I'm in need of some relay or power mosfet guidance. I need to be able
to switch the following loads (on and off) using a microcontroller:

1. 6.0 amps at 15V DC.

The first question to ask is if you can use "low-side" ground
switching, or if you need "high-side" +15V switching? You can do
the former with a garden-variety logic-level power MOSFET, which
you'll no doubt get lots of advice about, but for the latter, you
may need to provide short-circuit load-fault protection. You can
use a high-side power-switch IC - there are many to choose from.
I like the Infineon PROFET series, such as the 40V 38-milliohm
BTS432, in a convenient 5-pin TO-220 case, at DigiKey, $5.50

2. A 1900W device running off of 110VAC (I'm assuming 17.27 Amps
rms or 49 amps peak-peak).

For this you should use a standard SSR module, these run from a 5V
logic-level input, are optically isolated, and use triacs, optimally
with an ac zero-crossing switching feature. When you wire up one of
these, it's a good idea to add a fuse in series with the ac line.

 

[PeteS]

For number 1, as Winfield noted, it depends on whether you can use high
or low side switching. Alternatively, you can use a charge pump to get
high side switching. If you can only use low side switching, I
particularly like the IRF7425 (rated at -12A continuous at 70C, 4.5V
Vgs, with an astounding 8.2 milliohm Rds at this drive - astounding for
a P-channel, anyway).

I concur on using a standard SSR (Vishay has lots of them) for the AC
requirement.

Cheers

PeteS