Is there a SSR like device that can switch at kHz frequencies?

Question

I'm designing an industrial control system that incorporates several peltier devices.

As I understand it, these devices are more efficient when driven with a constant voltage, vs being cycled every few seconds.

What I would like to do is drive the peltiers using PWM in the kHz range, and run the power through an inductor to limit the current ripple.

The issue is that my go-to device for high current control is an SSR like this: AD-SSR6M12-DC-200D Afaik, these will not work at kHz frequencies; and at lower frequencies the inductor becomes excessively large.

So here's what I'm wondering. Is there an industrial type device similar to a SSR that will work at kHz frequencies? Ideally I would like to keep the isolation feature as well.

I know I could build my own MOSFET circuit to accomplish this, but a reliable off the shelf device would be preferable. Does such a thing exist?

My peltiers, and the PLC outputs are all 24 volts. The peltiers draw 4.2A at 24V

Link to Peltier Assembly.

Answer 1

What you're describing is an adjustable switch-mode buck voltage supply. These exist. As a matter of fact, you're quite possibly using multiples of them to access the internet :D

And: whilst 4.2 A isn't "small" current, it's also not heavy duty, so you'll be able to design one with the online power designers that e.g. TI.com has. I don't know what your maximum operation voltage should be, but it's probably easiest to use an off-the shelf 48V supply and design a buck converter with Vin=48V, Vout=24V, Iout=5A (headroom is always nice), and then adapt the control loop to be adjustable to your needs (often, you can "hijack" a current limiting input by adding a constant voltage e.g. from a DAC to the feedback voltage).

You'll notice that you can pick topologies that are isolated; however, that's typically pretty complex. One could argue that your 48V supply should be the one that's isolated together with the control interface, and that thus you don't need isolation in your adjustable power supply.

Something that'd, in my book, work would be:

Since you want adjustability, you'd remove the connection between the Rfbt/Rfbb voltage divider and the FB pin, and replace it with an opamp adder, where you add the voltage divider voltage to a 0-0.8V voltage generated by a DAC. Since generation of reference voltages is a very PLC thing to do, chances are you've already got an isolated DAC available (you might need to use a voltage divider to adjust it to your 0-0.8 V range).