I understand the basic concept of wireless power transfer.

I wanted to make some wireless LEDs (Similar to this concept) and was trying to figure out the minimum component count I required in order to make the boards as small as possible.

I'm assuming that the inductive charging used in phones utilises some sort of full wave rectification and a voltage regulator inside the phone in order to feed a fixed voltage DC level into the battery. (Please correct me if this is wrong)

Now the circuit I was thinking is as shown below:


simulate this circuit – Schematic created using CircuitLab

So on the transmitter so I'd use a micro to create a square wave at a similar resonant frequency to the coil.

On the receiver side I'd use a single diode for some half wave rectification and a capacitor to smooth it out and use it to power the LED. I'm hoping that if I use a coil with a resonant frequency of 10-20kHz then this will be fast enough to overcome the capacitor discharging too much and will give a roughly stable DC-ish voltage.

Or can I go more simple than this and just have a resistor and an LED without worrying about any rectification? As long as the reverse voltage across the LED isn't too high during the negative half cycle.
I assume the LED would be dimmer overall as it's essentially like running an LED at 50% duty cycle with PWM but aside from that is there any other problems that might occur?

The other product on the market seems to use only 4 components from what I can see (coil, 2 caps and an LED) but can't quite figure out how it would be possible if anyone has any insights?

enter image description here

  • \$\begingroup\$ Also consider a doubler using a series capacitor and diode in inverse parallel with the LED. \$\endgroup\$ – Spehro Pefhany Oct 27 '18 at 22:36
  • 1
    \$\begingroup\$ There are really a lot of options to do this (like frequency, size, ...) and I think you are doing great so far. RFID systems have exactly the same requirements and I can say from my own experience with illuminating LEDs from an RFID system that it can be as simple as inductor+diode+LED to get good results. \$\endgroup\$ – Stefan Wyss Oct 28 '18 at 12:49

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.