Help with Induction Heater

Discussion in 'The Projects Forum' started by Nfiltr8, Apr 27, 2009.

  1. Nfiltr8

    Thread Starter New Member

    Apr 27, 2009
    I'm building (well, trying to) an induction heater for a school project. I'm having several problems with it, however, and I was wondering if any of you could help me out. :)

    The setup I'm using is a half-bridge MOSFET driven inverter, and I'm using the following components:

    2 IPW50R399CP MOSFETs
    10 .47μF / 850V Tank Capacitors
    3 .33μF / 630V Blocking Capacitors
    1 Ferrite Core Inductor (Not sure of the inductance, I can probably manipulate it significantly, though)
    1 .01μF / 100VDC Bus Capacitor
    I don't have the work coil set up yet, but again, I can probably manipulate it to whatever is required.

    The problems I'm having is understanding what exactly is the function of the MOSFETs... I understand that they provide high frequency switching, but what purpose is that if we can already establish an alternating current?

    The other thing I'm worried about is the gate-drive circuitry for the MOSFET? I have no idea about that, although I'm guessing it powers the gates on the MOSFETs with a specific voltage, causing them to switch.

    If anyone can help me with any of this, I would GREATLY appreciate it.
    Thanks in advance.
  2. thingmaker3

    Retired Moderator

    May 16, 2005
    A high frequency is required to take advantage of skin effect and avoid "current canellation." Have a gander here: Chapter 2

    The MOSFET drivers are to make sure the MOSFETs turn all the way on and all the way off rapidly. You can get monolithic drivers from several sources.
  3. Nfiltr8

    Thread Starter New Member

    Apr 27, 2009
    Would this driver be suitable for my application?

    MAX8552 High-Speed, Wide-Input, Single-Phase MOSFET Driver

    Single-Phase Synchronous Drivers
    Up to 24V (max) Input Voltage
    0.1µA (typ) Quiescent Current in Shutdown Over Temperature
    0.5Ω/1.0Ω/0.7Ω/1.3Ω ROUT Drivers
    12ns (typ) Propagation Delay
    11ns (typ) Rise/Fall Times with 3000pF Load
    Adaptive Dead Time and User-Programmable Delay Mode
    Up to 2MHz Operation with TDFN Package
    Up to 1.2MHz Operation with µMAX Package
    Enable Function
    TTL- and CMOS-Compatible Logic Inputs
    Available in a Space-Saving Thin DFN Package
  4. thingmaker3

    Retired Moderator

    May 16, 2005
    That driver will work fine, as long as the voltage across your half-bridge is not more than 24V.

    For the convenience of other members:

    MOSFET datasheet

    Driver datasheet