Fundamentals of Power Electronics 1 Chapter 19: Resonant Conversion Solution of converter voltage conversion ratio M = V/V g Eliminate R e :

Fundamentals of Power Electronics 2 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 R e.

Fundamentals of Power Electronics 3 Chapter 19: Resonant Conversion 19.2 Examples Series resonant converter

Fundamentals of Power Electronics 4 Chapter 19: Resonant Conversion Model: series resonant converter

Fundamentals of Power Electronics 5 Chapter 19: Resonant Conversion Construction of Z i

Fundamentals of Power Electronics 6 Chapter 19: Resonant Conversion Construction of H

Fundamentals of Power Electronics 7 Chapter 19: Resonant Conversion Subharmonic modes of the SRC Example: excitation of tank by third harmonic of switching frequency Can now approximate v s (t) by its third harmonic: Result of analysis:

Fundamentals of Power Electronics 8 Chapter 19: Resonant Conversion Subharmonic modes of SRC

Fundamentals of Power Electronics 9 Chapter 19: Resonant Conversion 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 10 Chapter 19: Resonant Conversion Model of uncontrolled rectifier with inductive filter network Fundamental component of i R (t) :

Fundamentals of Power Electronics 11 Chapter 19: Resonant Conversion Effective resistance R e Again define In steady state, the dc output voltage V is equal to the average value of | v R | : For a resistive load, V = IR. The effective resistance R e can then be expressed

Fundamentals of Power Electronics 12 Chapter 19: Resonant Conversion Equivalent circuit model of uncontrolled rectifier with inductive filter network

Fundamentals of Power Electronics 13 Chapter 19: Resonant Conversion Equivalent circuit model Parallel resonant dc-dc converter

Fundamentals of Power Electronics 14 Chapter 19: Resonant Conversion Construction of Z o

Fundamentals of Power Electronics 15 Chapter 19: Resonant Conversion Construction of H

Fundamentals of Power Electronics 16 Chapter 19: Resonant Conversion Dc conversion ratio of the PRC At resonance, this becomes PRC can step up the voltage, provided R > R 0 PRC can produce M approaching infinity, provided output current is limited to value less than V g / R 0