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  • TI 无桥PFC方案【转子tidu312.pdf】

    http://www.ti.com.cn/general/cn/docs/lit/getliterature.tsp?baseLiteratureNumber=tidu312&fileType=pdf 

     The  PFC  stage  consists  of  two boost  converters  each  operating alternately in boost mode during half of the input AC line cycle. 


      图片见:

    http://hi.baidu.com/282280072/item/69185561f030a1106895e6b7




    During one half of the line cycle one converter converts the AC line voltage to the DC 

    bus voltage, while the other converter performs thesame action during the other half of 

    the  line  cycle.  Inductor  L1,  MOSFET  switch  Q1,  current  sense  transformer  CT1  and 

    diode  D1  together form one  of  the  boost  stages  while,  L2,  Q2,  CT2  and  D2  form the 

    other  boost  stage.  A  capacitor  Cb  at  the  boost  converter  output  acts  as  an  energy 

    reservoir and provides regulated dc voltage to the PFC load denoted by RL. 

    Figure 1.1 indicates all the interface signals needed for full control of this bridgeless PFC 

    converter using a C2000 micro-controller (MCU). TheMCU controls the hardware using 

    five  feedback  signals,  two  PWM  outputs  and  one  GPIO output.  The  signals  that  are 

    sensed and fed back to the MCU include, the line and neutral voltages (Vin_L & Vin_N), 

    the  two  PFC  switch  currents  (Isw1,  Isw2),  and  the  boost  output  voltage  (Vbus).  These 

    sensed signals are used to implement the voltage and current control loops for this BL 

    PFC converter. 

    The  dc  bus  voltage  Vbus,  sensed  through  one  of  the  ADC  channels,  is  compared 

    against the reference bus voltage Vref. The resulting error signal Ev is then input the 

    voltage loop controller Gv which regulates the bus  voltage at the reference level. The 

    voltage  controller  Gv  has  the  form  of  a  two  pole  two  zero  (2P2Z)  compensator.  The 

    output of Gv, denoted by the letter A in Figure 1.1, is proportional to the amount of power 

    transfer  by  the  PFC  converter.  This  output  A  is  then  multiplied  by  three  parameters

    indicated by B, C and Km in Figure 1.1, in order toform the reference current command 

    Iref  for  the  PFC  current  control  loop.  The  signal  indicated  by  B  is  the  inverse  of  the square  of  the  RMS  input  voltage  which  enables  fast  feed-forward  control  of  the  PFC 

    system. The signal C is proportional to the rectified input voltage, which modulates the 

    voltage controller output A such that the PFC inputcurrent has the same shape of the 

    PFC input voltage. The parameter Km is called the multiplier gain which is used to adjust 

    the range of Iref corresponding to the full input voltage range of the PFC converter. The 

    output  of  the  multiplier  provides  the  reference  signal  for  control  of  average  inductor 

    current  IrefL.  However,  for  BL  PFC  system  the  current  feedback  is  from  the  PFC 

    switches  (Q1  &  Q2),  and  not  from  the  boost  inductors  (L1  &  L2).  This  means  the 

    reference signal IrefL for average inductor current control has to be converted before it is 

    used  for  PFC  switch  current  control.  In  Figure  1.1  this  is  indicated  by  the  conversion 

    block between IrefL and Iref. This reference current command Iref for the PFC current 

    control loop is then compared against the PFC switch current Ipfc sensed through two 

    ADC  channels.  The  resulting  current  error  signal  Ei is  then  input  the  current  loop 

    controller Gc which generates the PFC duty ratio command d such that the PFC switch 

    current tracks the reference current Iref. 

    In addition to implementing the voltage and currentloop controllers, C2000 MCU also 

    uses the sensed line and neutral voltage signals todetermine the polarity of the input 

    voltage (+ve & –ve half cycle) and to calculate therectified input voltage, the RMS input 

    voltage  and  the  input  line  frequency.  Based  on  the  polarity  of  the  input  voltage  the 

    C2000 controller selects the appropriate PFC switchcurrent (Isw1 or Isw2) to be used as 

    PFC current feedback Ipfc. The polarity informationis also used to set the appropriate 

    PFC switch (Q1 & Q2) to either in PWM mode (boost PFC) or in forced ON mode. All 

    these  time  critical  functions  are  implemented  in  a  fast  sampling  loop  enabled  by  the 

    C2000 Micro-controller high speed CPU, interrupts, on chip 12-bit ADC module and high 

    frequency PWM modules. A detailed description of the software algorithm is provided in 

    the following chapters.


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  • 原文地址:https://www.cnblogs.com/iable/p/4206823.html
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