inductance load

Discussion in 'The Projects Forum' started by blind2_man, Aug 6, 2010.

  1. blind2_man

    Thread Starter Active Member

    May 12, 2008

    I am working on following project: I have a BLDC motor and I would like to try to drive in linear mode. This means that I will use n linear power amplifier on phases drive by a microcontroller.

    My problem now that I have to solve is to find a power amplifier in AB class that works with motor coils (50-60uH/ 10-50mohm). An idea will be to use the configuration shown in attached files.

    Another idea will be to use TJA7294, but would like to have first a pspice simulation first, but I was not able to find spice model for TJA7294.

    One strong requirement for the project is to be able to drive 50W motor.

    Any suggestions will be helpful.
  2. JDT

    Well-Known Member

    Feb 12, 2009
    So you want to control the current in the windings.

    Because it is an inductive load, you can do it by Pulse Width Modulation. Then, your amplifier/controller only switches and will dissipate minimum power.

    Free-wheeling diodes to allow the current in the windings to continue to flow when your switcher is off.

    By controlling the on-off ratio you can regulate the average current in the inductive windings. Your switching frequency will probably be in the range 10 - 20 kHz

    Not sure what these I.C.'s you mention actually are but basically your driver circuit will have a 3-phase "H" bridge topology. Note the reverse diodes across all 6 transistors. These are the free-wheeling diodes.
  3. blind2_man

    Thread Starter Active Member

    May 12, 2008
    @JDT the idea is not to use PWM or other digital modulated signal, I will use DAC to drive power amplifier module and the topology that I has thinking is push-poll one.