How to make Wireless Power Charger for Ipod

Wireless Power Charger:

Step 1: Required Components

2 MOSFETS - I understand that this is a rather vague statement. You can use the IRFP250, if you want to. However, the lower the on-state resistance is, the less heat will be generated.

2 10k ohm resistors. (brown black orange) You can use 1/4 watt ones.

2 Ultrafast Diodes - They need to be above 400 volts. I used UF4007's.

2 Twelve volt zener diodes - Nothing special to say here!

1 7805 - I know I said I used a boost converter. However, a boost converter is a whole another instructable, and I can't explain how to build one in this. So, for now, we'll just use a 7805.

2 18k ohm resistors - 1/4 watt (brown - gray - orange)

2 12k ohm resistors - 1/4 watt (brown - red - orange)

USB Female Port - I scavenged mine from an old adapter PCI board we had from 2000. We didn't need it, so I figured why not?

Two sets of tank capacitors - I used 4 1 uF capacitors for mine. You can use two 2 uF capacitors instead, if you want to. You NEED to make sure they're MKP, or a better type! Polyester ones, electrolytics, anything along those lines will not work, and will overheat!

You'll also need some wire.

Step 2:    The Schematic

To build it, just follow the schematic as shown. If you're having trouble identifying the MOSFET's pins, look up the part number of the MOSFET you're using, and follow what it says on there.

For those following it to the book, the IRFP250's pin out goes like this, from left to right; Gate, Drain, and then Source.

If you mess this up, your MOSFETs will almost certainly go boom!

For the diodes, the black band on it, or the white band on the UF4007's indicates the cathode. The other end is the anode. (for simpler terms, the cathode is the pointy end of the diode symbol, where the line goes across it. The anode is the flat base of the triangle)

Mind you, this is just for the transmitter!

Also note; the higher the input voltage, the more distance you should get out of your transmitter. Remember, though, at this comes a cost; the mosfets will get warmer, and your current draw will increase!

Step 3:    Receiving...

The receiving end is less complex. Make sure you use the same capacitor value! Make sure you follow the USB pinout as I have written in the schematic.

You can try and experiment with different turns ratio's of the coils and see what kind of performances you get! This has to do with resonance, and step-up / step-down ratios.

Try adding more voltage, and see if you get more distance; another way of possibly increasing distance is to increase the resonant frequency a bit. Increasing the frequency should give you more distance, with additional current draw.

To increase the frequency, just lower the capacitor values. Personally, the lowest I'd go would be around .1 uF. Make sure when you lower the cap value, you do it for both the receiving, and the transmitting ends!

Also, remember, the idea does not have to apply only to USB. You can use it to power anything that uses around 5 volts and under. (yes, this means you can power LED's!) Or, you could build another circuit (a flyback driver, perhaps?) to drive a CCFL!

You can do a lot with 5 volts!



Step 4:  Thoughts, and Possibilities
The ZVS driver is used for a lot of things due to it's simplicity. Your laptop might be using the same oscillator format to run its backlights!

However, in this case, the reason it works is because the ZVS driver begins by oscillating at around 50 - 60 khz. We can't hear it since it's above our hearing range.

Resonance can be thought of like a Pendulum. If you hit a pendulum, it will move forward, and then back. If you hit the pendulum again, right as it starts to swing downwards, the pendulum will travel faster and higher than before. It's very much the same in electronics, just instead of speed and height, it's voltage and current!

Due to resonance, the voltage swings in the tank (between the 3 + 3 coil and the 2 uF capacitor) are much higher than what the input voltage is. Resonance helps with transmission distance, and also, as a result of how the MOSFETS turn on, they're in what's called Zero Voltage Switching, where they turn on and off when the voltage across them is zero. (meaning, they generate little/no heat due to switching losses). However, due to on-state resistance, they still make a little bit of heat.



ANYWAY, going away from the complicated bits of it, the reason it can transmit power is caused by magnetism. As the coil oscillates, it sends an alternating magnetic field through the air, which is picked up by the receiving coil (and again, due to resonance, the voltage rises upwards!) and thus, power is transmitted through air! The same basic concept is behind radio waves; though, amplifiers are needed to get the audio out of the air, and the frequency is much higher!

I made all of the pictures shown in, though, the transmitter picture is a modified version of the famous Mazzilli flyback driver.

Thanks for reading!

Posted in: Electronics