Research On High-efficiency Wireless Charging Technology Based On Constant Current Chopper Topology

In order to eliminate the safety problems caused by the charging metal contacts and improve the flexibility of the charging system,wireless charging technology is widely used,and it has become a main development direction of the current charging technology.In recent years,with the continuous development of wireless charging technology,the power of wireless charging is continuously increasing and the volume is constantly decreasing,especially the receiving end.The receiving end is often in a small enclosed space with poor heat dissipation conditions.The charging technology puts forward a demand in terms of reducing heat generation and reducing the volume.For this demand,the current charging technology has certain deficiencies.The current wireless charging system is either a resonance type or an electromagnetic induction type.The principle is to generate voltage on the receiving coil,so that the receiving coil has voltage output capability.But in the process of charging the battery,the electric energy is required to be constant current.Therefore,most wireless chargers need to introduce additional voltage stabilization and charging management circuits at the receiving end.The heating loss and space occupation of the voltage stabilizing and charging management circuit play a leading role at the receiving end.These problems have brought great limitations to the design of wireless charging systems.In response to the requirements for simplified structure and high efficiency at the receiving end of the wireless charging system,this thesis has studied and analyzed the principles of the traditional wireless charging system and the loss model of the traditional wireless charging system and determined the main source of loss.A new charging topology that simplifies the receiving end circuit.And use this method to design a new type of wireless charging system,and build a set of 500 W wireless charging system based on the simulation parameters of the new type of charging system.The main work of this paper mainly includes:1.The traditional wireless power supply principle is studied in detail.The structure and working principle of the wireless charging system are given on the basis of the wireless power supply system.Combined with the wireless charging system given and the wireless charging system commonly used in the market,the loss model of the wireless charging system is proposed.Finally,the main sources of heat and the proportion of losses of the wireless charging system are obtained through formula derivation and parameter calculation.2.A new type of constant current chopper wireless charging system is proposed.On the basis of understanding the principle of wireless charging and determining the main source of loss,it is innovatively proposed to treat the coupler as a constant current converter.A new wireless charging system that generates constant AC power at the transmitter and only needs one-stage rectification at the receiver to directly charge the battery.3.Based on the above-mentioned new wireless charging system,the constant current chopping at the transmitting end is realized by the open loop feedback method of the comparator,the circuit model of the chopper is established,and the current expression is derived.It is obtained that the constant current effect of the transmitter is affected by the load type and size,and the conclusion is obtained through Simulink simulation:(1)The constant current chopper is only suitable for low impedance load conditions(2)The ratio of the supply voltage of the transmitter to the battery voltage is greater than 2.5.4.Through theoretical derivation of the new charging system,the current relationship between the transmitting end and the receiving end is obtained.The constant current analysis of the charging current of the receiving end is based on the constant current condition of the transmitting end proposed in the previous article.It is concluded that the higher the coupling coefficient of the coupler,the better.And under a set of parameters,it is concluded that the coupling coefficient is not less than 0.68 under the allowable receiving end current error of 5%.5.A set of wireless charging system under the condition of 500 W full load power is designed,and the system is tested.The test results show that the efficiency of the system can reach 90.37%.Compared with the traditional wireless charging system,it has an efficiency improvement of 6%.