# Wireless Power Transfer (is this correct)

• jaus tail
In summary, the circuit produces a high frequency oscillation signal by charging and discharging an inductor.
jaus tail
TL;DR Summary
Circuit Operation:

I couldn't find the working of this circuit so I guess it would be like:
Initially transistor is OFF, so the current flows through Base, and then when transistor is ON, the current flows through transistor Collector to Emitter, so now it flows down the transformer. Base current is reducing and then transistor turns off, so then flux falls. And then again current flows through Base, so cycle continues?

Is this correct? But if current flows through base initially, and if Emitter current is zero, so where does the base current come out from? Emitter current is Beta times collector current. Collector current is zero, so emitter current would also be zero, right?

Which figure is that from at the link? It looks wrong, and is missing some way to make the left hand side oscillate, IMO. Is it from Figure 5?

jaus tail
Oh, maybe you posted Figure 6. Still looks wrong to me, though...

jaus tail
But I drew the original circuit that I have posted in MATLAB simulink and was able to get oscillations. I had kept source voltage around 0.4V

How
berkeman said:
Which figure is that from at the link? It looks wrong, and is missing some way to make the left hand side oscillate, IMO. Is it from Figure 5?

View attachment 252164
Could you explain the working of this circuit?
I found a slightly difference circuit:

It says:
In transmitter section, the Transistor is generating high-frequency AC current across the coil and the coil is generating a magnetic field around it. As the coil is center tapped, the two sides of the coil start to charge up. One side of the coil is connected to the resistor and another side is connected to the collector terminal of NPN transistor. During the charging condition, the base resistor starts to conduct which eventually turns on the transistor. The transistor then discharges the inductor as the emitter is connected with the ground. This charging and discharging of the inductor produces a very high frequency oscillation signal which is further transmitted as a magnetic field.

Ref: https://circuitdigest.com/electronic-circuits/simple-wireless-power-transmission-circuit-diagram

In transmitter section, the Transistor is generating high-frequency AC current across the coil and the coil is generating a magnetic field around it. As the coil is center tapped, the two sides of the coil start to charge up. One side of the coil is connected to the resistor and another side is connected to the collector terminal of NPN transistor. During the charging condition, the base resistor starts to conduct which eventually turns on the transistor. The transistor then discharges the inductor as the emitter is connected with the ground. This charging and discharging of the inductor produces a very high frequency oscillation signal which is further transmitted as a magnetic field.

That explanation really makes no sense. "discharging an inductor" ?
What happens both of the 17-turns inductors are wound into a transformer. Once the transistor starts to conduct, the much large collector current will turn off the base current. Negative feedback + time delay + enough amplification will produce oscillation.

Last edited by a moderator:
jaus tail

## 1. What is Wireless Power Transfer?

Wireless Power Transfer (WPT) is the transmission of electrical energy from a power source to an electrical load without the need for physical connections such as wires or cables. It uses electromagnetic fields to transfer energy between two objects.

## 2. How does Wireless Power Transfer work?

WPT works by using electromagnetic induction, resonance, or radio frequency (RF) radiation to transfer energy wirelessly. In electromagnetic induction, a primary coil creates a magnetic field which induces a current in a secondary coil, thus transferring energy. In resonance, two coils with the same resonant frequency exchange energy through oscillating magnetic fields. In RF radiation, energy is transmitted through radio waves and received by a device equipped with a receiver antenna.

## 3. What are the benefits of Wireless Power Transfer?

Some of the benefits of WPT include convenience, as it eliminates the need for cords and cables, and enables devices to be charged or powered from a distance. It also reduces the risk of electrical shocks and eliminates the need for multiple power outlets. WPT can also be used in harsh or hazardous environments where traditional power sources may not be feasible.

## 4. What are the limitations of Wireless Power Transfer?

One of the main limitations of WPT is its efficiency. The transfer of energy wirelessly is not as efficient as using physical connections, resulting in some energy loss. The distance between the power source and the device also affects the efficiency of WPT. Additionally, WPT technology is still in its early stages and may not be widely available or compatible with all devices.

## 5. Is Wireless Power Transfer safe?

Yes, WPT is generally considered safe. The electromagnetic fields used in WPT are non-ionizing, meaning they do not have enough energy to cause harm to human tissues. However, it is important to use WPT devices according to the manufacturer's instructions and avoid prolonged exposure to the electromagnetic fields.

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