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I am trying to find a way how to control the Voice Coil Motor (VCM) or PMSM motor with a closed current loop without the use of an H-Bridge & PWM.

Does anyone know how to make an analog closed current loop control without PWM and H-Bridge?

I heard that the closed current loop was the last from the cascade control scheme to be digitized and I'd like to compare the performances of analog versus digital one.

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  • \$\begingroup\$ If you want direct AC drive from a single polarity voltage, I think some form of h-bridge is necessary. If you have a bipolar source you could get down to two switches. If you want fully analog output without PWM you need to drive the switches as amplifiers, which will have higher losses than PWM, but would be orders of magnitude easier than a PWM drive that can drive high wattages at high fidelity to a reference signal, and that would be a very good reason for analog audio drive to survive a long time. I'm not that informed about this stuff though. \$\endgroup\$ – K H Sep 13 '18 at 5:59
  • \$\begingroup\$ How much amps and volts? \$\endgroup\$ – Marko Buršič Sep 13 '18 at 6:25
  • \$\begingroup\$ 24V and max 1.5A (SLA25-010-55-1) \$\endgroup\$ – J.Valášek Sep 13 '18 at 8:32
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You could use a simple current driver and a DAC such as this IC. If the IC doesn't source enough current you could 'break out' the block diagram an make your own current driver with opamp and mosfet. Instead of a DAC you could use a frequency generator circuit to run pure analog.

enter image description here

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  • \$\begingroup\$ Thanks, the only problem is, that I need to drive the VCM in both directions :/ \$\endgroup\$ – J.Valášek Sep 13 '18 at 0:52
  • \$\begingroup\$ Ah, you didn't mention that in your question \$\endgroup\$ – Voltage Spike Sep 13 '18 at 0:54
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enter image description here

OPA541 is the high voltage, high current opamp suited to drive your coil. It was a solution for decades back, when no high speed MCU, DSP, ADC, DAC was available.

You may have a look also at different devices:

https://www.apexanalog.com/products/mp38.html

enter image description here However, these old days are over. A H-bridge with GaN MOSFET and high frequency PWM would give better efficiency with minimal impact on performance.

It would be a nice article to have a comparison of new and old technologay.

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