Design Of Telecom Power Supply Based On LLC Resonant Converter

Along with the development of power industry,high efficiency,high integration and good heat dissipation switching power supply have been the mainstream of the present market demand.However,because of the internal high voltage,large current in the high power switching power supply,it results in large loss of the switch tube,the impact on the overall efficiency of the power is also very large.For keeping the power importation from bringing influence to exportation,the topological structure of power mostly adopts stage separation.Because LLC can achieve zero voltage switches in the full load,zero current side diode turn off,and can also realize the stable output voltage with the frequency narrow change,reduce the amount of loss caused by the switch tube,it becomes the preferred topology of high power development.As users have further requirements for the power supply,researchers did further selection and design on the device,this paper completed the design of 3kW high power communication power supply based on LLC resonant converter.The communication witching power supply is divided into two levels,the former is a power factor correction circuit,the other is DC chopper circuit based on the topology of LLC resonant half-bridge converter.Power factor correction circuit as a power supply plays a role of voltage boost and reducing the current harmonics,the section uses BOOST circuit topology,used the new L4981B control chip to complete the circuit power factor correction function,used the average current controls method to make the input current and voltage same frequency and phase,suppressed pollution of the current harmonics on the power grid to improve the power factor of the machine.Chopper circuit level is composed mainly of the switch tube,resonant inductance,resonant capacitance,magnetized inductance,transformer and the secondary side rectifier,adopted the fundamental analysis method to complete the parameters in the resonant circuit set;Through charging and discharging the interelectrode capacitance of switch tube,the voltage between drain and source will drop into zero before the switches opened,supressed voltage switching converter in stress,and finally realized the soft switch function;Methods using synchronous rectification of soft switch function secondary side of the transformer switch,greatly reduced the loss of the switch turn-on and turn-off.Software part of switching power supply mainly realized the closed loop control,used the PID algorithm to calculate the analog quantity,changed the driving waveform frequency,ensured the stability of the output voltage and short response time,also increased the reliability of the switching power supply.