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Sensorless VS Sensored BLDC motors

Discussion in 'Sensors and Actuators' started by Lord_grezington, Jul 9, 2016.

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  1. Lord_grezington

    Lord_grezington

    124
    2
    May 3, 2013
    Hello All

    Got an issue where I have a PCB that uses the Allegro A4963 IC. I am trying to displace another cheap Chinese JRC per-driver that runs sensored motor, please fin th link here http://www.njr.com/semicon/products/NJM2626.html.

    Now, running the same motor (and load) at the same supply voltage the JRC achieves around 52% more speed. (the A4963 schematic is very similar to the demo one as the PDF attached).

    I took a trace of the motor phase voltages and note that the JRC sensored driver produces a square wave where the A4963 produces a trapezoidal one. I am guessing that the voltage losses due to being trapezoidal may be the reason for my decrease in speed.

    I spoke to the Applications engineers at Allegro and all they can say is that I need to increase the supply voltage or adjust the phase advance (which I tried every value going with no luck).

    So, I was hoping one of you had seen a similar issue in the passed and willing to share their knowledge, all traces and schematics are attached (I cant find one for the Chinese driver unfortunately).

    Thanks

    PS - Before you mention that the JRC driver uses high side N-channel mosfets that are more efficient, no it doesn't, both drivers use P-channel high side fets...

    I cant seem to attached any files, anyone help me with a format? not even PDF goes through without an error...
     
    Last edited: Jul 9, 2016
  2. Sunnysky

    Sunnysky

    480
    121
    Jul 15, 2016
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