Simple Wireless Mobile Phone Charging Circuit

In this article there are two primary components to a wireless mobile phone charging circuit: a transmitter circuit and a receiver circuit.

Designing a circuit for a wireless battery charger is rather simple and easy.

Only resistors, capacitors, diodes a voltage regulator, copper coils and a transformer are needed for these circuits.

Transmitter circuit working:

Parts List:

A coil coupled to a 12V battery, powers the circuit.

Additionally, a transistor TIP35 and a capacitor C are linked to the coil.

An oscillator circuit generates alternating current AC in the transmitter coil of a wireless charger transmitter circuit.

A magnetic field is created around the coil by the AC current.

A phenomenon known as inductive coupling causes a voltage to be induced in a compatible receiver coil when it is positioned close to the transmitter coil.

In order to charge the battery in the receiving device the receiver coil rectifies the AC voltage to DC voltage.

How the inductor works:

The inductor with a center tap:

One inductor divided into two equal inductance halves by a connecting point in the middle is called a center tapped inductor.

This preserves their magnetic coupling while producing two distinct inductors electronically.

A transistor and additional parts are used in this circuit to produce a continuous oscillating AC signal.

Although there are many other kinds of transistor oscillator circuits, two popular ones that make use of a center tapped inductor are as follows:

Hartley oscillator:

The DC supply voltage is connected to the inductors center tap in a hartley oscillator.

The transistors base and collector terminals, as well as a capacitor are connected to each side of the inductor.

The feedback loop that is formed by the transistor and capacitors produces the oscillation.

In a wireless charger transmitter, how does it operate?

The circuit is powered by the DC supply voltage, the circuits current oscillates due to the transistor the feedback loop produced by the capacitors and the center tapped inductor.

The whole inductor both halves is subject to the oscillating current.

The oscillating current in one half creates an opposite voltage in the other half because of the magnetic coupling inside the inductor.

A powerful AC voltage is produced throughout the whole inductor as a result of these combined effects.

After that, the transmitter coil transmits the AC voltage creating a magnetic field surrounding it.

A Center Tapped Inductors Advantages

This makes circuit design simpler by doing away with the requirement for separate inductors.

It increase efficiency when compared to the use of two independent inductors.

It gives the transistors DC bias current a way to reach it without interfering with the AC oscillation.

Crucial Points to Remember:

An understanding of electronics and careful component selection are necessary for designing and constructing a safe and effective oscillator circuit.

The oscillation frequency which is essential for wireless chargers to work with receiving devices will depend on the particular circuit design.

Safety measures such as foreign object recognition and overheating prevention should be built into wireless charger circuits.

The location of the transmitter and receiver coils is crucial for efficient wireless charging.

This is how they ought to be arranged:

Alignment:

The coils must be axially aligned and face to face, this indicates that the coils centers should line up and their flat surfaces should be straight across from one another.

Each coils center should be intersected by a straight line these lines should run on the same axis.

Distance:

For effective charging the space between the coils is essential.

It need to be as compact as feasible without sacrificing functionality.

The ideal spacing is one or two millimeters to one centimeter.

Greater separations cause the coils to couple less strongly, which lowers the power transmission.

Area of Overlap:

Furthermore significant is the region where the coils overlap.

Better efficiency is typically correlated with a wider overlap area.

Larger transmitter coils than receiver coils are sometimes used in designs to guarantee a good overlap area even in the event of a little misalignment.

Inconsistency in alignment Tolerance:

It may not always be possible to achieve perfect alignment in some situations.

Rectangular transmitter coils are used in certain charger designs because they offer a higher misalignment tolerance than circular coils.

To provide a larger charging zone certain sophisticated systems may also use numerous transmitter coils or coils with unique shapes.

Receiver circuit working:

Parts List:

The receiver coil generates a little AC voltage by picking up the transmitter coils AC magnetic field.

Diode 1N4007 converts the coils AC voltage into a pulsing DC voltage by rectifying.

Capacitor 1000 μF evens out the diodes pulsing DC voltage.

Improved Functionality:

The 7805 Voltage Regulator is an effective tool for charging a variety of mobile phone batteries since it regulates the voltage from the capacitor to a consistent 5V output.

A significant flaw in the earlier design is fixed with the 7805 voltage regulator.

By ensuring that the phones battery receives a steady and secure 5V throughout charging, it guards against any potential harm from uncontrolled voltage swings.

This wireless charger receiver circuit design is more functional since the 7805 regulator is included.

On the other hand, it is best to utilize commercial chargers that put safety first and have extra features.

Formulas:

In order to charge a mobile phone wirelessly, the electromagnetic energy received from a transmitter coil must be converted into a useful DC voltage during the circuit design process.

Here is the general formula for such a circuit.

Calculating Output Voltage (After Rectification and Smoothing):

Using this method, one may estimate the voltage following rectification and smoothing.

V_out​ = V_peak​−V_diode​−V_dropout​

where,

• The peak AC voltage created in the receiver coil is denoted by Vpeak.
• The forward voltage drop across the diode is denoted by Vdiode.
• The dropout voltage of the LM7805 regulator is Vdropout, which is usually about 2V.

With the above components, this formula gives a basic grasp of how to construct a wireless mobile phone charging receiver circuit.

Depending on the particular needs and features of your wireless charging system, adjustments can be required.

Safety Measures:

• Wireless chargers that are sold commercially are built and tested to adhere to safety standards.
• It is not advised to build your own charger circuit unless you have a thorough grasp of electronics and safety procedures, since it can be harmful.

Conclusion:

To conclude, wireless phone charging provides an easy and cordless method of charging your gadgets.

It operates on the basis of the inductive coupling concept, which involves the cooperative effort of a transmitter and receiver circuit to transfer energy wirelessly.

The transmitter circuit uses a coil and an AC current to create an oscillating magnetic field.

This magnetic field is detected by the phones receiver circuit, which then transforms it back into DC current to charge the battery.

References:

 Simulation of wireless mobile charger circuit

Datasheet IC 7805