(精品)bridgelessPFC(1208).ppt

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1、LITE ONPower Electronics Lab(Beijing)Power Conversion DivisionBridgeless PFC Vivian sunLITE ONPower Electronics Lab.(Beijing)Power Conversion BU,P&C SBGBridgeless PFCThe purpose-For higher power range,the bridge power loss is high,especially at low line condition.For example,the bridge power loss of

2、 1200W PS is about 24W.-The bridgeless PFC topology can reduce total power loss,improve efficiency and thermal performance.LITE ONPower Electronics Lab.(Beijing)Power Conversion BU,P&C SBGBridgeless PFCThe comparison of bridge and bridgeless PFCThe design process Power loss calculationDesign toolsLI

3、TE ONPower Electronics Lab.(Beijing)Power Conversion BU,P&C SBGThe comparison of bridge and bridgeless PFCTopologyPower Loss and Parts CountCurrent SensingIac SensingFloating GroundLITE ONPower Electronics Lab.(Beijing)Power Conversion BU,P&C SBGThe topology of bridge PFCLITE ONPower Electronics Lab

4、.(Beijing)Power Conversion BU,P&C SBGThe Topology of Bridgeless PFCLITE ONPower Electronics Lab.(Beijing)Power Conversion BU,P&C SBGBridgeless PFC OperationLITE ONPower Electronics Lab.(Beijing)Power Conversion BU,P&C SBGComparison of Bridge and Bridgeless PFCLITE ONPower Electronics Lab.(Beijing)Po

5、wer Conversion BU,P&C SBGCurrent SensingLITE ONPower Electronics Lab.(Beijing)Power Conversion BU,P&C SBGCurrent SensingLITE ONPower Electronics Lab.(Beijing)Power Conversion BU,P&C SBGCurrent SensingLITE ONPower Electronics Lab.(Beijing)Power Conversion BU,P&C SBGIac Sensing(bridge)LITE ONPower Ele

6、ctronics Lab.(Beijing)Power Conversion BU,P&C SBGIac Sensing(bridgeless)LITE ONPower Electronics Lab.(Beijing)Power Conversion BU,P&C SBGThe Floating Ground of Bridgeless PFCWith a coupled choke as boost inductor,no capacitor can link L and N to power GND,otherwise the choke will be shortened.So the

7、 power GND is floating with the switches on and off at a switching frequency.LITE ONPower Electronics Lab.(Beijing)Power Conversion BU,P&C SBGThe Comparison of EfficiencyLITE ONPower Electronics Lab.(Beijing)Power Conversion BU,P&C SBGDesign SpecificationsVin=90264VACVo=380VDCPo=1200WFs=100kHzPF0.98

8、(Full load&high line)Eff92%LITE ONPower Electronics Lab.(Beijing)Power Conversion BU,P&C SBGBlock DiagramLITE ONPower Electronics Lab.(Beijing)Power Conversion BU,P&C SBGBoost Inductor DesignPeak input current at low line Ipk:Duty cycle at low line D:LITE ONPower Electronics Lab.(Beijing)Power Conve

9、rsion BU,P&C SBGBoost Inductor DesignBoost inductance L:Delta I is 20%peak currentSelect L=300uH(initial inductance)LITE ONPower Electronics Lab.(Beijing)Power Conversion BU,P&C SBGBoost Inductor DesignMagnetic core:Arnold MS-185060-2 or Dongbu S184-086A Magnetic material:sendust(kool Mu)Al=86mH/100

10、0T,Bs=0.95TWe choose:N=60According design tools,the maximum magnetic force is 120 Oersteds and the flux density is 0.56T(2/3)Bs.LITE ONPower Electronics Lab.(Beijing)Power Conversion BU,P&C SBGPower Stage DesignOutput capacitor selection(holdup time 20ms)Select C out=660uF(two 330uF/450V capacitor i

11、n parallel)Main switch selection Two STW26NM60(600V/30A)in parallelBoost diode selection Low reverse current and fast reverse recovery diode shall be selected.SDT12S06 or STTH1506TTI is preferred.LITE ONPower Electronics Lab.(Beijing)Power Conversion BU,P&C SBGControl Circuit DesignUsing UCC3818 as

12、the PFC controllerVoltage Loop DesignCurrent Loop DesignCritical Point of Bridgeless PFCLITE ONPower Electronics Lab.(Beijing)Power Conversion BU,P&C SBGVoltage Loop Design 1The pole is placed at the crossover frequency,is about 1020Hz,the zero is placed at the one tenth of the crossover frequency.T

13、he power stage gain is given by:LITE ONPower Electronics Lab.(Beijing)Power Conversion BU,P&C SBGVoltage Loop Design 2Voltage loopThe voltage amplifier configuration as right:Vref=7.5,so we choose:R125=R126=R127=332k,R129=19.6kVout=(332*3+19.6)*7.5/19.6=388VThe second harmanic voltage on the output

14、capacitor is:The gain of the voltage amplifier is:LITE ONPower Electronics Lab.(Beijing)Power Conversion BU,P&C SBGVoltage Loop Design 3Voltage loop(continued)The value of Cf is determined by:The pole is place at the frequency:LITE ONPower Electronics Lab.(Beijing)Power Conversion BU,P&C SBGCurrent

15、Loop Design 1Current loopThe gain of the power stage is:The current amplifier gain is:LITE ONPower Electronics Lab.(Beijing)Power Conversion BU,P&C SBGCurrent Loop Design 2Current loop(continued)The crossover frequency is 5KHz10KHz,the zero is placed at the crossover frequency to give a phase margin

16、 of 45 degrees.And a pole is placed at one-half the switching frequency to reduce switching noise.LITE ONPower Electronics Lab.(Beijing)Power Conversion BU,P&C SBGCritical point of Bridgeless PFCDue to the floating power GND,IAC cant be achieved by rectified line voltage directly in this circuit.We

17、know IAC is|Vin|/R,so we just need have|Vin|.In this circuit,we can achieve|Vin|by filtering Vo*(1-D).D is the duty cycle of the driving signal of switches.LITE ONPower Electronics Lab.(Beijing)Power Conversion BU,P&C SBGCritical point of Bridgeless PFCThe net introduces one pole at:The pole must be

18、 located at a frequency high enough not to distort the input waveform and at the same time,low enough to filter the switching frequency.We select fp=10kHz,R1=600k,R2=7.5k,C=2200pFLITE ONPower Electronics Lab.(Beijing)Power Conversion BU,P&C SBGPower Loss CalculationBoost inductorLITE ONPower Electronics Lab.(Beijing)Power Conversion BU,P&C SBGPower Loss CalculationMain SwitchesLITE ONPower Electronics Lab.(Beijing)Power Conversion BU,P&C SBGPower Loss CalculationLITE ONPower Electronics Lab.(Beijing)Power Conversion BU,P&C SBGPower Loss CalculationBoost Diode