lecture3 2008 postlec by ye58M2

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									                                       ECEN 5817
                                    Housekeeping update


       •    For both on-campus and CAETE students: A DVD of recorded lectures
            from Professor Erickson’s Spring ’06 class will be mailed to you
            sometime next week. These will not be available on the CAETE
            website CUAnywhere.colorado.edu
       •    For on-campus students: You will not have access to this semesters
            recorded lectures on the CAETE website
       •    For CAETE students: By popular request, scanned and e-mailed
            homework will be accepted provided the submissions meet the
            following requirements:
              • Black and white (no color, no grayscale)
              • 200 – 300 dpi
              • All problems scanned into ONE PDF file for the whole assignment
              • PDF file is easy to read, easy to open, and easy to print


Fundamentals of Power Electronics          1               Chapter 19: Resonant Conversion
                                          Chapter 19
                                    Resonant Conversion

          Introduction
          19.1     Sinusoidal analysis of resonant converters
          19.2     Examples
                    Series resonant converter
                    Parallel resonant converter
          19.3     Soft switching
                    Zero current switching
                    Zero voltage switching

          19.4     Load-dependent properties of resonant converters

          19.5 Exact characteristics of the series and parallel resonant
               converters


Fundamentals of Power Electronics            2              Chapter 19: Resonant Conversion
                             Equivalent circuit of rectifier

      Rectifier input port:
            Fundamental components of
            current and voltage are
            sinusoids that are in phase
            Hence rectifier presents a
            resistive load to tank network
            Effective resistance Re is
                                                     Rectifier equivalent circuit


             With a resistive load R, this becomes



             Loss free resistor

Fundamentals of Power Electronics            3                Chapter 19: Resonant Conversion
                           19.1.4 Solution of converter
                         voltage conversion ratio M = V/Vg




                                                     Eliminate Re:




Fundamentals of Power Electronics      4             Chapter 19: Resonant Conversion
                                    Conversion ratio M




          So we have shown that the conversion ratio of a resonant converter,
          having switch and rectifier networks as in previous slides, is equal to
          the magnitude of the tank network transfer function. This transfer
          function is evaluated with the tank loaded by the effective rectifier
          input resistance Re.




Fundamentals of Power Electronics          5                    Chapter 19: Resonant Conversion
                    19.2.2 Subharmonic modes of the SRC


                                              Example: excitation of
                                              tank by third harmonic of
                                              switching frequency
                                              Can now approximate vs(t)
                                              by its third harmonic:




                                              Result of analysis:




Fundamentals of Power Electronics   6           Chapter 19: Resonant Conversion
                              Subharmonic modes of SRC

                                            • Not often used - reduced switch
                                            utilization and decreased voltage
                                            conversion ratio
                                            • Still need to be aware their existence




Fundamentals of Power Electronics       7                     Chapter 19: Resonant Conversion
                                  19.2 Examples
                          19.2.1 Series resonant converter




Fundamentals of Power Electronics      8             Chapter 19: Resonant Conversion
                          Model: series resonant converter




Fundamentals of Power Electronics      9             Chapter 19: Resonant Conversion
                Construction of Zi – Resonant (high Q) case
                     C = 0.1 μF, L = 1 mH, Re = 10 Ω




Fundamentals of Power Electronics   10           Chapter 19: Resonant Conversion
       Construction of H = V / Vg – Resonant (high Q) case
                C = 0.1 μF, L = 1 mH, Re = 10 Ω

           Buck characteristic




Fundamentals of Power Electronics   11      Chapter 19: Resonant Conversion
                                    Construction of Zi




Fundamentals of Power Electronics         12             Chapter 19: Resonant Conversion
                                    Construction of H




                                                          Qe  R0 / Re




Fundamentals of Power Electronics        13             Chapter 19: Resonant Conversion
                            Model: series resonant converter




Fundamentals of Power Electronics       14            Chapter 19: Resonant Conversion
            Construction of Zi – Non-resonant (low Q) case
                   C = 0.1 μF, L = 1 mH, Re = 1 kΩ




Fundamentals of Power Electronics   15        Chapter 19: Resonant Conversion
            Construction of H – Non-resonant (low Q) case
                   C = 0.1 μF, L = 1 mH, Re = 1 kΩ




Fundamentals of Power Electronics   16        Chapter 19: Resonant Conversion
                   19.2.3 Parallel resonant dc-dc converter




          Differs from series resonant converter as follows:
                Different tank network
                Rectifier is driven by sinusoidal voltage, and is connected to
                inductive-input low-pass filter
          Need a new model for rectifier and filter networks

Fundamentals of Power Electronics          17                    Chapter 19: Resonant Conversion
                        Model of uncontrolled rectifier
                   with inductive filter network – input port




                                          Fundamental component of iR(t):




Fundamentals of Power Electronics    18               Chapter 19: Resonant Conversion
                       Model of uncontrolled rectifier
                 with inductive filter network – output port

                                         Output inductor volt second balance:
                                         dc voltage is equal to average
                                         rectified tank output voltage




Fundamentals of Power Electronics   19                Chapter 19: Resonant Conversion
                                    Effective resistance Re

          Again define




          In steady state, the dc output voltage V is equal to the average value
          of | vR |:




          For a resistive load, V = IR. The effective resistance Re can then be
          expressed




Fundamentals of Power Electronics           20                  Chapter 19: Resonant Conversion
           Equivalent circuit model of uncontrolled rectifier
                    with inductive filter network




             Dependent voltage source based on rectified tank voltage.
             Vs. SRC, dependent current source based on rectified tank current.
Fundamentals of Power Electronics        21                  Chapter 19: Resonant Conversion
                              Equivalent circuit model
                          Parallel resonant dc-dc converter




Fundamentals of Power Electronics      22             Chapter 19: Resonant Conversion
            2 different ways to construct transfer function H




Fundamentals of Power Electronics   23          Chapter 19: Resonant Conversion
                Construction of Zi – Resonant (high Q) case
                     C = 0.1 μF, L = 1 mH, Re = 1 kΩ




Fundamentals of Power Electronics   24           Chapter 19: Resonant Conversion
       Construction of H = V / Vg – Resonant (high Q) case
                C = 0.1 μF, L = 1 mH, Re = 1 kΩ

           Buck-boost characteristic




Fundamentals of Power Electronics      25   Chapter 19: Resonant Conversion
                                    Construction of Zo




Fundamentals of Power Electronics         26             Chapter 19: Resonant Conversion
                                    Construction of H




Fundamentals of Power Electronics        27             Chapter 19: Resonant Conversion
                           Dc conversion ratio of the PRC




         At resonance, this becomes


          • PRC can step up the voltage, provided R > R0
          • PRC can produce M approaching infinity, provided output current is
            limited to value less than Vg / R0

Fundamentals of Power Electronics       28                  Chapter 19: Resonant Conversion
       Comparison of approximate and exact characteristics

                                                   1.0


    Series resonant                                0.8

    converter

                                    M = V/Vg
                                                                                                             exact M, Q=2
                                                   0.6                                                       approx M, Q=2
                                                                                                             exact M, Q=10
                                                                                                             approx M, Q=10
       Below resonance:                            0.4
                                                                                                             exact M, Q=0.5
                                                                                                             approx M, Q=0.5

                0.5 < F < 1                        0.2


                                                   0.0
                                                         0.5   0.6       0.7           0.8   0.9      1.0
                                                                               F
                                                    1.0
       Above resonance:
                                                    0.8
                   1<F
                                          M=V/Vg




                                                                                                             exact M, Q=0.5
                                                    0.6                                                      approx M, Q=0.5
                                                                                                             exact M, Q=10
                                                                                                             approx M, Q=10
                                                    0.4
                                                                                                             exact M, Q=2
                                                                                                             approx M, Q=2
                                                    0.2


                                                    0.0
                                                          1          2             3         4         5
                                                                               F
Fundamentals of Power Electronics                         29                                     Chapter 19: Resonant Conversion
       Comparison of approximate and exact characteristics

 Exact equation:                    Parallel resonant converter
    solid lines
 Sinusoidal approximation:
   shaded lines




Fundamentals of Power Electronics     30              Chapter 19: Resonant Conversion

								
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