boost converter and inductive load

Discussion in 'The Projects Forum' started by kovibb, Mar 30, 2012.

  1. kovibb

    Thread Starter New Member

    Nov 3, 2011
    3
    0
    hi

    I must design boost converter from 12V to 24V for induction load. Induction load is solenoid coil (cca 20mH)+48ohm which is driven by PWM controlled current. Till now I dont have to solve similar problem like this only resistive load. What is mainly problems or traps of this design according to you? How do you fight with this? I look forward to your answers. Thank you
     
  2. DickCappels

    Moderator

    Aug 21, 2008
    2,659
    632
    If you rectify and filter the output of the boost converter with a diode and capacitor, you have a DC supply to drive your PWM circuit.

    If I failed to read your mind accurately, please post the circuit you have so far, or at least a block diagram.
     
  3. kovibb

    Thread Starter New Member

    Nov 3, 2011
    3
    0
    so i post block scheme for your requirement and thank you for quickly reply. I have forgotten there are flyback diodes connected between MOSFET sources and ground in every parallel branch. every branch have to be dopped maximum 500mA current. Rs - sense resistor, Ls - solenoid coil, Rr - restriction resistor, A - sense amplifier gain.
     
  4. wayneh

    Expert

    Sep 9, 2010
    12,151
    3,058
    Yup, the PWM circuit won't know where its DC came from and the boost converter won't be affected by whatever is going on downstream. As with a resistive load, the concern is that the load is "small" compared to the capacity of the booster and the filtering capacitor. In other words, keep ripple within tolerable limits.

    You don't specify the frequency. Are these mechanical solenoids? Don't you need to integrate the PWM current so that the solenoid is either on or off, not switching quickly? Sorry if these are stupid questions but I don't quite grasp what you're building.
     
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