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5W cell phone charger design <.25" possible?

John Smeltzer
Prodigy 145 points

Starting a new 5W cell phone charger design (5V @ 1A). The trickiest requirement is the PCB assembly must be <.25" thick. So far it looks like the magnetics are the thickest component (transformer). Are there any transformer that will meet this requirement?

  • 0
    TI__Mastermind 40520 points
    Hello John,

    I recommend that you investigate the catalogs of magnetics vendors for EFD and planar cores for your application. Planar cores use the pcb to carry the windings with printed copper coils on multiple layers. However the core protrudes on both sides of the pcb and may affect the heights of the other component of your converter. EFD cores come with surface-mount coil formers (bobbins) which can be placed all on one side of the pcb.

    A quick check of the 2013 Ferroxcube ferrite handbook indicates that the EFD10/5/3 core set with standard bobbin is the shortest height in this form factor at 0.224 in. (5.7 mm) above the pcb surface. This leaves scant thickness for the pcb itself. There may be lower-height cores and/or coil formers available from other vendors, or a custom-designed bobbin may be required. I suggest to search around and contact various magnetics vendors (such as Wurth Electronics, Coilcraft, Coiltronics, Renco, Pulse Engineering, etc. to name a few) about their standard and custom design offerings and discuss your needs for this challenging packaging constraint.

    Regards,
    Ulrich