i want to construct a half bridge driver for motor control application. The voltage range from 48-72v. Having worked with non isolated schemes before (for lower voltages), I decided now for isolation. I have thought of two ways:

1- use opto isolator on the PWM pin of the IR2184

2- use ADuM3223 half bridge driver.

An isolated dc dc converter will be used to supply the microcontroller ( inorder to protect the micro from noise and load dump .. etc and a non-isolated converter for gate driver.

adum3223 typical circuit from datasheet

if you have another aproach i would be delighted to hear it .

  • 2
    \$\begingroup\$ -1 for the sloppy and annoying writing style. Thumbing your nose at the volunteers that you seek a favor from is not a good strategy. \$\endgroup\$ – Olin Lathrop Dec 17 '15 at 17:49
  • \$\begingroup\$ I think you'd have an easier time leaving the uC on the motor side and placing your isolation boundary between your uC and whatever controls that. \$\endgroup\$ – whatsisname Dec 17 '15 at 18:11
  • \$\begingroup\$ The ADuM3223 is not an opto isolator - it's a magnetic coupler but I reckon it's a good choice so I forgive you for having to rewrite my answer (that I'd finished prior to you posting the picture). \$\endgroup\$ – Andy aka Dec 17 '15 at 18:18
  • \$\begingroup\$ We are volunteers here so don't be unappreciative of that. There's another thing and what you will find is that better formatted questions are easier to read and get more attention (whether you like that or not). \$\endgroup\$ – Andy aka Dec 17 '15 at 21:59
  • \$\begingroup\$ could you alaborate more who my post format can be changed ? is it the type of question asked or how the sentences are organized ? for next time \$\endgroup\$ – ElectronS Dec 18 '15 at 14:16

Use opto isolator on the PWM pin of the IR2184

Note that this answer was made prior to the OP showing a picture of the magnetic coupler proposed (note this is not an opto coupler despite the question explicitly stating "opto-isolated" in the title).

PWM operating frequency is going to kick you in the teeth unless you are running sub 10 kHz or you can find a really good opto-isolator that has fast rise and falls times.

A hand waving typical rise and fall time for an opto might be about 5 us and this will be into a quite low load resistance of about 100 ohm. Into 1 kohm it could rise to 20 us or more. Now, if it takes 20 us to deliver a PWM "edge" then you don't want to be switching too often or the rise/fall time inefficiences will be warming things up. So maybe 20 us represents 5% of the period of your PWM.

If you work that out you'd choose a PWM frequency of 2.5 kHz because 2.5 kHz has a period of 400 us and 5% of that is 20 us. But it's a little worse because there are two edges to consider in each PWM cycle so, you'd choose 1.25 kHz as your PWM frequency.

Regards the ADuM3223 - it is a good device and has a rise/fall time less than 100 ns!

| improve this answer | |
  • \$\begingroup\$ thank you for the reply , i will make some tests when the parts arrive and post results . \$\endgroup\$ – ElectronS Dec 18 '15 at 13:54

For other people that might be intersted in the subject , there is an IC from Silicon labs (called Si8239x) that they claim is better than both methods i have proposed.

This IC uses a CMOS Isolated technology.

here is the comparision tableIsolated Driver Technology Comparison

More details can be found in this White paper Isolators-in-Motor-Control-WP

| improve this answer | |

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.