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Wireless Power Transmission help!

Discussion in 'Power Electronics' started by josej28, Apr 26, 2014.

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  1. josej28


    Apr 26, 2014
    Currently, I am doing a project to explore wireless power transmission. The system consist of basically this schematic. The objective of the project is to obtain at least 5W at load in the receiver side.I am able to receive at receiver by induction coupling method 5V but current is limited to only 100mA. My goal is to obtain at least 500mA-1.5A. I tried to add resistor in the load area for the transmitter (LOAD) and it did not work. Also tried to implement a darlinton pair and did not work.

    The MOSFET im using are FQP50N06
    Arduino UNO microcontroller
    IR2110 High SIde/ Low Side Driver.

    Some input values for system.

    Wall input is 120V @ 60Hz
    Arduino inputs to IR2110 are two PWM's of 100-250 kHz.
    Input voltage to IR2110 is 12-15V
    Input voltage for HIGH SIDE MOSFET 18-24V

    Im using UF recovery diode due to high frequency application. Right now im stuck and dont know how to proceed in order to increase current.

    Any suggestion to schematic in terms of adding, eliminating components.??
    Any strange components that should not be where it is?

    Also, sometimes circuit rectified voltage which is being supply to other components in system varies as I increase a load. For this power supply im using a power transformer from radioshack and rectify it with DKBPO4 full bridge rectifier..

    Any additional suggestions?

    I am actually working with this circuit in a breadboard so any suggestion i can rapidly check it. THANKS FOR YOUR TIME READING AND SUPPORTING..!!

    Attached Files:

    • WPT.PNG
      File size:
      56.9 KB
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    Several suggestions:

    1) couple the coils together better (e.g. move them closer together)
    2) use a higher voltage to excite the coil
    3) Remove C17
    4) Drive the primary from an H bridge controller
    5) make sure your mosfets switch fast! (what are you using to drive them?) The gate resistor seems too large.
    6) increase C4
    7) remove D12

    There's probably more.
    KrisBlueNZ likes this.
  3. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    Nov 28, 2011
    In addition to Steve's excellent answers...

    Are you intending that L1 and C2 form a series LC circuit? Or is C2 just for DC blocking to prevent saturation? If the former, have you confirmed the inductance of L1?

    How are L1 and L2 constructed?
  4. josej28


    Apr 26, 2014
    Thanks for your suggestions. I will try and let you know how it went.

    Steve, i cannot use a higher voltage to excite the coils because im trying to follow up the Qi standard with design A1. Also, in the Qi standard im using the half bridge configuration. Later on , i will be exploring the Full H bridge. To drive them im using the IR2110 high side/ low side driver and the Hi and Li inputs to this driver are being send by the Arduino Microcontroller.

    I already increased C4, and D12 i removed. IN breadboard application after D12 im connecting a battery so i was using it to prevent that load interact with rectifying circuit. I will be lowering gate resistors.

    KrisBluenZ, yes im intending that L1 and C2 form a series LC circuit because im following Qi standard configuration. C2 is primarly used for resonance coupling. Probably i should try to connected it in other way. I have not confirmed the inductance of L1.

    L1 and L2 are coils that i received from Wurth Elektronik

    Their specification are in the Capture. PNG upload file. I know that probably inductance of L1 is not nearby 24uH but I have not measure it.

    Again, thanks for your suggestions and time of reviewing this circuit.

    Attached Files:

  5. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    Nov 28, 2011
    The inductors claim a high Q, so the bandwidth of the tuned circuit formed by L1 and C2 will be quite narrow. You will probably need to adjust your drive frequency to achieve maximum power transfer to the coil. Initially you can do a one-off adjustment but in a practical circuit it might be worthwhile adjusting it continuously for optimum power transfer.
  6. josej28


    Apr 26, 2014
    Yes, yesterday i was adjusting frequency to find a suitable point for maximum power transfer and found it that for this particular coils is between 100 kHz and 125 KHz. Certainly, one of my objective not now but after i complete this phase is to include a control system so frequency can be adjusted automatically for maximum power transfer.

    KrisBlueNz, thanks for comments!!
  7. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    Nov 28, 2011
    OK, good. You can calculate the expected resonant frequency using fr = 1 / (2 pi sqrt(L C)). Does that frequency match the frequency you found, roughly? If not, it's possible that you've found a harmonic of the actual resonant frequency. If you look at the Fourier analysis of a square wave, you'll see a series of humps, and you may not have found the biggest one. You can measure the actual resonant frequency by shorting the drive (i.e. putting L and C in parallel) and "ringing" the circuit by injecting a transient and watching the decaying oscillation on an oscilloscope. If your oscilloscope has a horizontal output, you can use that to supply the transient.
  8. josej28


    Apr 26, 2014
    Yes, actually the value used for the capacitor C2 and C17 is due to resonant and I obtained those values using the equations that you suggests. Few months ago I did a not so elaborate Fourier Spectrum analysis and found that certainly the fundamental frequency is between 100 kHz to 125 kHz so i decided to use this frequency range.

    Thanks again for suggestions and comments. I will be looking to try what are you suggesting with the oscilloscope.

    Thanks again, KrisBlueNZ
  9. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    Nov 28, 2011
    OK. If you're seeing peak power transfer in the calculated frequency range, you can be pretty confident that you've found the resonant frequency, unless you think that the actual inductance could be very different from the 24 µH specified.
  10. hevans1944

    hevans1944 Hop - AC8NS

    Jun 21, 2012
    I know virtually nothing about the currently popular near-field coupling of high-frequency power, presumably to re-charge portable devices such as cell phones and tablets. I am hoping my next smartphone has this feature because the micro-USB connector/jack used to (mainly) re-charge my Samsung Galaxy 4 is always the first thing to fail from repeated insertions and removals. My wife's iPad Air has a magnetically mated charging connector, which is a step in the right direction IMO, but an inductively-coupled charging pad would be better.

    Since the primary is resonant, would it not be more efficiently driven with a sine waveform rather than a PWM square wave? A class C or class D driver of a resonant load is pretty efficient, so maybe not. Some experimentation is required.

    If you do decide to explore resonant sinusoidal excitation, the Arduino could synthesize a stepwise sinusoidal approximation, perhaps with some filtering, to drive the power FETs in a linear fashion. But first I would use an amplified sinusoidal signal generator to drive the primary coil, just to explore the transfer properties and find out if the desired goal can be reached using the coils at hand. You may need coils with a larger area, depending on coupling distance. Only after nailing down the coil driving parameters would I proceed to develop the FET driver. The Arduino would then be added last to implement closed-loop control of the power and frequency.

    To save some software overhead, the Analog Devices AD9838 integrated circuit is available to generate digitally programmed sine waves at frequencies up to 8 MHz. It features a 10-bit DAC output.

    73 de AC8NS
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