Appropriate Mosfet and Mosfet Driver

Discussion in 'Homework Help' started by Runs212, Sep 24, 2015.

  1. Runs212

    Thread Starter Member

    Mar 12, 2015
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    Operating frequency is 125Khz, I will be building a circuit that's capable of providing 5W to a load. For the (receiver) Tx, arduino (5V) will provide a pwm to a mosfet driver which should then boast the gate voltage up to 10V that will be connected to 2 n-channel mosfet. N/b the driver will provide inverted signals.
    The output will be connected to a resonance circuit which will be matched for the Rx(receiver circuit) which comprises resonance circuit, a full wave rectifier, a filter, liner regulator (to step down voltage to 5V) and finally connected to my load(Phone) Hence, Expected output is 5V and up to 1A = 5W to comfortably charge the phone.

    I have been using fqa55n25 and irf2103 mosfet and mosfet driver and have been getting up 50V peak-to-peak but very LOW current. The output current on driver i'm measuring is 80mA on the highside, and 40mA on the low side. Duty cycle is 50%. I think the descrepancy in the current maybe as a result of a 60% to 40% duty cycle from from the driver i suppose to ensure there's no overshoot. based on the Ig = Qg/ton (values from mosfet datasheet) current required to charge cap on mosfet is 1.4A current me if i'm wrong hence, 80mA wouldn't cut it.

    Lately, i realized that Gte charge, rise times and fall times should be considered when selecting mosfets. Hence, I need help figuring out a matching mosfet and it's driver. Help me consider the appropriate ic that will help generate up to 1.5A.
     
  2. cmartinez

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    A schematic would come in handy to better understand this problem
     
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  3. Runs212

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    Mar 12, 2015
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    I've attached the schematic
     
  4. cmartinez

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    Thanks, I had no problem finding the FQA55N25 datasheet, but I could not find anything on the irf2103 driver. Are you sure that's the correct part number?
     
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  5. Runs212

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    Mar 12, 2015
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    That should be irs2103
     
  6. cmartinez

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    Thanks, are you using the DIP or the SMT version?
     
  7. Runs212

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    Mar 12, 2015
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    I'm using the DIP version
     
  8. dl324

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    You're expecting to transmit power from your Arduino+driver to a passive receiver and generate 5W net??
     
  9. Runs212

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    Mar 12, 2015
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    Please refer to the schematic. I am able to generate 5V on the load but very low current. It indicates that my phone is charging but then it's not getting enough power. I am currently generating less than 1W as i'm getting about .1A through the phone.`
     
  10. cmartinez

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    Look at the Functional Block Diagram on the driver's datasheet (page 4). As you can see, LIN input is internally pulled up to Vcc by a resistor. Since you're using the 5V output from your Arduino, maybe there's a level conflict in that signal. You may need to use a transistor to interface between your Arduino and the driver's HIN and LIN inputs, since the driver is being powered by 12V, and your Arduino at less than that.
     
  11. Runs212

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    Mar 12, 2015
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    On the output of the the driver, based upon my schematic, Both HO and LO have matching output, hence at Vcc of 12V, I'm measuring approximately 11.8V. The driver actually does boost the V to whatever Vcc is
     
  12. cmartinez

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    Yeah, but wouldn't that make a conflict with your arduino's outputs? I don't see a diode in your schematic between the arduino and LIN. And even if you placed a diode, there would be a voltage drop.
    But never mind that, I've tried to use similar drivers in the past and have always ended up having headaches. My favorite way of driving a mosfet is with a floating-type power supply, such as this one.
     
  13. recklessrog

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    May 23, 2013
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    The bootstrapping diode does need to be an ultra fast device, also, you may get better performance by connecting the primary output winding directly to the source/ drains of the fets, and connect the other end to the junction of two capacitors in series across the supply rails. The two parasitic damping resistors could be lowered to around 15-22 ohms. You would also need to put something like a 10 ohm resistor in series with a 1n capacitor across the primary to limit the rate of voltage rise dv/dt so that you don't get premature turn on of the wrong fet or smoke will ensue! I have not looked up the spec of the driver i.c but you need one that allows for a small dead time between outputs so that there is no possibility of both being driven at the same time.
    I built a very powerful 2KW inverter using an IR2153D ( the D denotes it has an inbuilt bootstrap diode, It is also available without the internal diode.
     
    Last edited: Sep 24, 2015
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  14. dl324

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    That was my point. Assuming typical linear regulator efficiency; to get 8-10W of power coupled to your circuit, the transmitted power would need to be significantly higher than that.

    Are you trying to reinvent a wireless charger where you place the device on a charging pad?
     
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  15. Runs212

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    Mar 12, 2015
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    Yes, I'm building a wireless charging pad for my class project.
     
  16. cmartinez

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    Now I understand...
     
  17. Runs212

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    Mar 12, 2015
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    Continuing this conversation. Please help me compare the mosfet driver and mosfet to see if they are a good match. How does the rise/fall times matter?

    I reduced the gate resistance to 22ohms, matched the resonances on the rx and tx and getting the corresponding waveform at 17V but the current still is very low. Help me understand the important characteristics on the datasheet.
    Thanks again for all your help.
     
  18. ronv

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    @Runs212 You could change the FET for one with a lower gate charge.
    http://www.mouser.com/ds/2/196/IPA180N10N3 G_Rev2.3-94023.pdf
    Or a bigger driver:
    http://www.mouser.com/ds/2/196/IPA180N10N3 G_Rev2.3-94023.pdf

    You may not be able to get 8 volts at 1 amp with a 12 volt transmitter supply, but you should get better than .1 amp.
    You are better off with the smaller inductor and lower frequency as it better matches your load.
    For those who haven't seen your other thread.

    http://forum.allaboutcircuits.com/threads/source-current.110689/
     
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  19. cmartinez

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    Ron, you posted the same link for the driver and the mosfet.
     
  20. ronv

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