A wireless charger circuit principle design

1 Wireless charger principle and structure

The wireless charging system mainly adopts the principle of electromagnetic induction, and energy transfer through the coil realizes energy transfer. As shown in Figure 1, when the system is working, the input terminal converts the AC mains into a DC power through the full-bridge rectifier circuit, or directly supplies the system with a 24V DC terminal. The DC power output after the power management module is converted into high frequency alternating current by the 2M active crystal oscillator to supply the primary winding. The energy is coupled through two inductor coils, and the current output from the secondary coil is converted into direct current by the conversion circuit to charge the battery.

2 .2 Transmitting circuit module

As shown in Figure 3, the main oscillator circuit uses a 2 MHz active crystal oscillator as the oscillator. The square wave of the output of the active crystal oscillator is filtered out by the second-order low-pass filter to obtain a stable sine wave output, which is output to the coil and the capacitor through a class C amplifier circuit composed of a triode 13003 and its peripheral circuits. The parallel resonant circuit radiates out. Provide energy to the receiving part.

3.2 Receive Circuit Module

The core-coupling coil of the parallel resonant circuit composed of capacitance is measured to have a wire diameter of 0.5 mm, a diameter of 7 cm, an inductance of 47 uH, and a carrier frequency of 2 MHz. According to the parallel resonance formula, the matching capacitance C is about 140. pF. Thus. The transmitting portion uses a 2 MHz active crystal oscillator to generate an energy carrier frequency close to the resonant frequency.

in conclusion

Experiments have shown that although the system can not be charged invisibly, it has been able to place multiple school appliances on the same charging platform and charge at the same time, eliminating the trouble of wiring.

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