Need Help: PWM Controlled AC to DC Power Supply

Hello,

I'd like to hear some suggestions on the different options to make a DC power supply.

I have the following requirements.

Input Voltage: ~115v Wall outlet. Output Voltage: 90v 2A (Power for Motor) Output Voltage: 9v 1A (Power for Arduino USB)

Ideally, the power supply not be huge.

One option for the power supply part is to order a toroidal based premade supply.

This device will cost roughly $90-120 from Antek. The downside is that it's physically huge for what I think I need. 8.25"x5.5"x3.5"'ish

I would assume that I also have other options vs a large transformer.

So the goal is to take 115vac and turn it into 90vdc/2a.

After I get to the 90vdc output. I would like to be able to control the speed of a motor attached to it via PWM.

I have this part worked out from a arduino code point of view.

Unfortunately, selecting random components from digikey/mouser isn't my forte and I'm afraid that I might be missing some of the obvious things that someone else would see.

So, if we have the 90v dc, we need to be able to switch it on and off quickly via the PWM pin. From my other posts, this should be possible to do via mosfet. I have a litle bit of confusion on whether I should get a logic gate type mosfet that plug directly into the arduino. Or if I should get some type of mosfet driver, which appears to be like locating bigfoot.

Is this the best option.

Summary

End goal, 90vdc controlled via pwm to control the speed of a motor.

Side Goal, is to provide power for the Arduino. This can get done via a seperate wall wart style power supply. But I would like to combine if possible to provide a cleaner product.

If the the large ~$100 dollar toroid power supply is the best option. I can do it. I'm just concerned that my little cellphone charger takes 115v and turns it into ~5v. I wouldn't think that it would be as involved to take 115 and turn it into 90.

Thanks for any help.

I wouldn't think that it would be as involved to take 115 and turn it into 90.

Ah but it is. You want :-

Output Voltage: 90v 2A (Power for Motor) Output Voltage: 9v 1A (Power for Arduino USB)

So let's look at the power that supplies:- On the 90V rail = 90 * 2 = 180W On the 9V rail = 9 * 1 = 9W Total power 180 + 9 = 189 Watts

The downside is that it's physically huge for what I think I need. 8.25"x5.5"x3.5"'ish

Yes that is the sort of size you get when you want 200W power. To design this is beyond your capability, it would take you at least 5 years experience in electronic design to approach anything like this.

I would assume that I also have other options vs a large transformer.

Yes that is a much simpler prospect, just requiring a bridge rectifier and some hefty capacitors (make sure the current rating of the capacitors is big enough)

we need to be able to switch it on and off quickly via the PWM pin.

You won't do that from a logic FET most of those only have a 60v rating.

Or if I should get some type of mosfet driver, which appears to be like locating bigfoot.

That is because they are not called mosfet drivers (although some are), you just need a transistor and as it is at 90v I would also include an opto isolator. But yes you need a driver for the mosfet.

Thanks for the prompt and candid reponse.

But please don't assume that a particular solution is outside of my ability. It might be outside my current knowledge level, but I am a fast study.

Currently, I am attempting to find out more about the possible solutions and alternatives..

i.e.

Probably untrue example ahead

There are only two types of power supplies.

Linear and Switched.

Linear makes use of a transformer, bridge rectifier, and some giant caps. It is simple, but not size effective.

Switched power supplies come in the following forms.

x, y, and z.

For X, you need to take a bridge rectifier, then dump your intial output voltage(~170v) into a step down dc-dc conveter via a a really cool buck? circuit. The new voltage that comes out won't be pretty so you need to condition it via another cool curcuit filter.

Once you have your voltage where you want it, you can feed it into the mosfet and begin the pwm love.

side note I have found logic gate level mosfets that can handle the 90+ volts, but I just want to make sure that it's all that I need. I just feel that it's too simple to be true solution.

links

http://www.powerdesignersusa.com/InfoWeb/resources/pe_html/pe07_nc8.htm

Thanks in advance for any replies.

side note
I have found logic gate level mosfets that can handle the 90+ volts, but I just want to make sure that it’s all that I need. I just feel that it’s too simple to be true solution.

High power/current/voltage logic level MOSFETs are amazing components and can be a great solution for switching high power loads. However one has to be aware of the heat dissipation management requirements for any higher power MOSFET application.

All the current and voltage specs may match but if the device is not run in its SOA then it can fail dramatically in short order. Heat sinks are your friend when dealing with them.

Lefty

The thing about switching power supplies of this type of power are hard to design. Transformers with very specific windings (multiple windings, in your case), high-current inductors, a bunch of supporting ICs, and a mess of heatsinking.

I once endeavored to build one myself, and after getting half a dozen of texts on just switching power supplies from my school's engineering library, I realized that I didn't have the time to dedicate to learning an entire sub field of electronics.

You'll save yourself a lot of frustration and time if you just buy one now (you'll also avoid those pesky accidental fires). There is a reason that the robotics kids at my school scrounge up any spare PSUs they can find--anyone can make a 5V switching regulator, but a good switched-mode psu isnt something you just scrounge together.

Does anyone have a supply house for a 90v/2a switching power supply.

I can find the large linear toroidal/cap based, but i don't see any switching ones.

Most are in the 24v-48v range.

I'm not opposed to buying a solution. I just want to make sure that I know and understand all of my options.