Analysis of the electronic circuit design of the wireless energy transfer charger

　　Main oscillator circuit:

　　NE555 is used as the waveform generation circuit. By adjusting the size of the variable resistor of 555, the frequency and duty cycle of the output square wave can be changed within a certain range. When the LC oscillation circuit changes, adjusting the size of the variable resistor can generate a waveform of the corresponding frequency, forming resonance with the LC circuit.

　　Power amplifier circuit:

　　The field effect tube is used as the power amplifier element, the power consumption is lower than that of the triode, the driving power is small, and it is easy to use. It can be driven directly by using the output of NE555.

　　Unit circuit:

　　1 The power circuit uses 24V and 5V power supplies to power the field effect tube NE555 respectively. After the transformer is used to transform the power, the 7812 and 7912 voltage regulator modules are used to generate 24V points, and then the 7805 power supply is used to generate 5V power. And it is important to note that the two power supplies share the same ground.

　　2 The signal generating circuit uses NE555 to form a signal generator with an oscillation frequency of about 500KHZ, which provides an excitation signal for the power amplifier circuit. By adjusting the size of the variable resistor of 555, the frequency and duty cycle of the output square wave can be changed within a certain range, and the required frequency can be adjusted.

　　3 Design of the receiving end charging control circuit After the electric energy is received by the coil, the high-frequency AC voltage is full-wave rectified by the IN4007 rectifier tube, filtered by a 2200uf capacitor, and then stabilized by a 3.3V Zener diode. The output DC power provides a more stable working voltage for the light bulb (battery).

　　Improvement ideas:

　　(1) When the transmission distance and coil parameters are fixed, the transmitting end needs to have a higher frequency and the transmitting coil should work in a resonant state to increase the transmission efficiency.

　　(2) One way to increase the distance is to increase the voltage of the transmitter circuit.

　　(3) This design uses IN4007 rectifier tube for rectification, and the average voltage drop of the tube is 0.8V. The conduction loss is large and it is not suitable for use in the receiving circuit. If Schottky diode is used, the tube loss can be greatly reduced, and the power utilization rate is higher.

　　(4) The copper wire diameter, coil diameter, number of turns and winding method not only determine the inductance value of the coil, but also affect its transmission efficiency.