At resonance the impedance of the LC is very low so the current is quite high - So yes you need a larger supply. You might also want to add some resistance (1/2 - 1 ohm) in series with the LC at least until you can see how much current it does draw.
Add some load to the output of the receiver until the voltage drops, then measure the current.

PS.
What does your receiver circuit look like?

Attached is the schematic for the Rx.

Revisiting this, I have been having serious issues with my circuit. I realized that the gate current should be taken into consideration in my system here. Based on the above topology, I have 25Ohms resistors at the output of my drivers. The high side measures 104mA while the low side measures around 52mA at 15V Vcc. The frequency is 125KHz.

Help me understand this:
For the MOSFET, it's Qg = 140nC T(on)= 100ns. Hence, the Gate current required = Qd/Td = 1.4A.

Based on the above info, am i right to say that the mosfets wouldn't sufficient charge/turn based on my measured outputs? Hence, would replacing my mosfet be necessary? My goal is to generate at least 1A in the receiver circuit, I'm considering buying a MOSFET Driver with a peak output current of at least 1.5A.


Also, correct me if I'm wrong, i should match my rise time/fall time on the mosfet and it's driver right? How does my frequency affect the calculations. .


I have been beating this circuit for weeks and i'm not making any progress in understanding why it's not supplying a high current at the load.

 

Like ronv asked, how does your receiver look like, and what arrangement are the coils? You just might not have enough coupling to get the power through.

I have attached it.
That was the schematic i used with the frequency being around 77Khz.
I have recently changed the frequency to 125Khz.

 

How do the coils look like physically? How large, wide, thick and what shape are they? How close together and how oriented are they? A picture or photo would be helpful too.
If your transmitter works at 77khz, you need the receiver to be tuned to the same frequency.

 

How do the coils look like physically? How large, wide, thick and what shape are they? How close together and how oriented are they? A picture or photo would be helpful too.
If your transmitter works at 77khz, you need the receiver to be tuned to the same frequency.

The thinner coil for the Rx and Tx is for the Tx. Also, I can have revised my capacitors to for resonance at 125Khz.

Without connecting the L and C, I should be getting a clean square wave but I'm getting an output with a lot of noise.

 

You have them side by side? They need to be on top of each other to get anywhere.

 

Of course they're on top of each other. I placed it side by side so you could see it.

 

Maybe this http://www.wirelesspowerconsortium....ng-the-right-choice-for-your-application.html might be a good place to start researching of what has been done before, instead of just guessing.

 

My circuit is based on the qi standard. However, the qi standard doesn't explicitly state what types of ic to use. For instance, my circuitry is based on A1, qi std only provides the inverter and resonance cir, everything else has to be figured out based upon those standards; not entirely helpful.

 

The thinner coil for the Rx and Tx is for the Tx. Also, I can have revised my capacitors to for resonance at 125Khz.

Without connecting the L and C, I should be getting a clean square wave but I'm getting an output with a lot of noise.

I would stick to the lower frequency for a while as the FET losses will be lower.
A few things:
Once upon a time you said your power supply was 0.5 amps at 12 volts. 0.5 amps is to low.
Did you add the diodes across the gate resistors? Try the values I posted in the schematic. This is important for the heating.
It is very important that everything be running at the resonant frequency. The inductors and capacitors have some pretty big tolerances so you may need to "tune" both the transmit frequency and the receiver circuit for optimum.

 

The thinner coil for the Rx and Tx is for the Tx. Also, I can have revised my capacitors to for resonance at 125Khz.

Without connecting the L and C, I should be getting a clean square wave but I'm getting an output with a lot of noise.

View attachment 91929

View attachment 91928

Your photo file - capture.png was used the wrong file format, I already converted to capture.jpg from over 100kb to 17kb, the *.png was designed to save the simple graphics as horizontal and vertical lines, more complicated graphics using *.jpg is better.

 

If I could bother everyone for a few seconds. The circuit attached is the receiver getting a 5V PWM from an arduino. I just recently started using a 15V, 2A adapter to power the device. Vdd is 15V and Vcc is 12V (from a regulator). From the picture, they all share the same ground. Before using the power adapter, I had been using a power supply from my lab where Vdd and Vcc where connected to different power sources but with one common ground.
I noticed with the power adapter that it was not transferring power to the receivers unless both transmitter coils were "connected" (.ie close enough) to the receiver coils i.e when i lift Rx1 or Rx2, the system seems to turn off but when i bring it back (i.e close enough) the current increases.
I am not sure why that's happening? I'd appreciate some help figuring this out.

 

Why 2 transmitters?
What happened to:http://forum.allaboutcircuits.com/threads/source-current.110689/

 

I would stick to the lower frequency for a while as the FET losses will be lower.


.

Modern MOSFETs are pretty fast - Fairchild is one company that puts some effort into advertising just how fast.

Much of the losses in a SMPSU are in ferrites, and diodes if the voltage is too high for reasonably priced Shottky diodes.

I've seen product bulletins for SMPSU transformers that are spiral tracks on either side of the PCB with ferrites clamped on over them. These tend to be somewhere in the general direction of 1 - 2MHz.

 

Why 2 transmitters?
What happened to:http://forum.allaboutcircuits.com/threads/source-current.110689/

Haha Ronv I moved on to two! The base station I'm building has two transmitters. The system actually works flawlessly. However, it seems there's a leakage; some type of back current. I spoke to one of my professors today, he said a capacitor should be placed at the power source to make it stable. I will try this later tomorrow. Thanks for all the the assistance through the project, it was very helpful. Considering my project works, I will be graduating in Dec 18.
Thanks again everyone!

 

Modern MOSFETs are pretty fast - Fairchild is one company that puts some effort into advertising just how fast.

Much of the losses in a SMPSU are in ferrites, and diodes if the voltage is too high for reasonably priced Shottky diodes.

I've seen product bulletins for SMPSU transformers that are spiral tracks on either side of the PCB with ferrites clamped on over them. These tend to be somewhere in the general direction of 1 - 2MHz.

I've been working with 125Khz. At much lower frequencies, the power dissipation in the FET was just too high.

 

I've been working with 125Khz. At much lower frequencies, the power dissipation in the FET was just too high.

Frequency isn't the only possible cause of a MOSFET getting hot.

Some manufacturers are introducing spiral track on each side of the board chopper transformers - last time I saw a product bulletin on it, the frequencies were somewhere around the 1 - 2MHz mark.