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Ch10slides - Chapter 10 Input Filter Design 10.1...

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Fundamentals of Power Electronics 1 Chapter 10: Input Filter Design Chapter 10 Input Filter Design 10.1 Introduction 10.1.1 Conducted EMI 10.1.2 The Input Filter Design Problem 10.2 Effect of an Input Filter on Converter Transfer Functions 10.2.1 Discussion 10.2.2 Impedance Inequalities 10.3 Buck Converter Example 10.3.1 Effect of Undamped Input Filter 10.3.2 Damping the Input Filter 10.4 Design of a Damped Input Filter 10.4.1 R f –C b Parallel Damping 10.4.2 –L Parallel Damping 10.4.3 Series Damping 10.4.4 Cascading Filter Sections 10.4.5 Example: Two Stage Input Filter 10.5 Summary of Key Points

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Fundamentals of Power Electronics 2 Chapter 10: Input Filter Design 10.1.1 Conducted Electromagnetic Interference (EMI) + CR + v L i i g 1 2 v g ( t ) t i g ( t ) DT s T s 0 0 0 i i Buck converter example Input current i g ( t ) is pulsating: i g ( t )= DI + 2 I k π sin k π D cos k ϖ t Σ k =1 Approximate Fourier series of i g ( t ) : High frequency current harmonics of substantial amplitude are injected back into v g ( t ) source. These harmonics can interfere with operation of nearby equipment. Regulations limit their amplitude, typically to values of 10 μA to 100 μA.
Fundamentals of Power Electronics 3 Chapter 10: Input Filter Design Addition of Low-Pass Filter + CR + v L i i g 1 2 i in L f C f Input filter v g ( t ) t i g ( t ) DT s T s 0 0 0 i in ( t ) i in ( t )= H (0) DI + H ( kj ϖ ) 2 I k π sin k π D cos k ϖ t + H ( kj ϖ ) Σ k =1 Magnitudes and phases of input current harmonics are modified by input filter transfer function H ( s ): The input filter may be required to attenuate the current harmonics by factors of 80 dB or more.

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Fundamentals of Power Electronics 4 Chapter 10: Input Filter Design Electromagnetic Compatibility Ability of the device (e.g. power supply) to: function satisfactorily in its electromagnetic environment (susceptibility or immunity aspect) without introducing intolerable electromagnetic disturbances ( emission aspect) EMC Emission Susceptibility Conducted Radiated Harmonics EMI Conducted Radiated Electrostatic Discharge
Fundamentals of Power Electronics 5 Chapter 10: Input Filter Design Conducted EMI Sample of EMC regulations that include limits on radio- frequency emissions: European Community Directive on EMC: Euro-Norm EN 55022 or 55081, earlier known as CISPR 22 National standards: VDE (German), FCC (US) v ac (t) i ac (t) + C i 2 (t) i g (t) v g (t) i(t) load + v(t) p load (t) = VI = P load Energy storage capacitor v C (t) + DC/DC converter EMI filter AC line source Regulated DC output AC/DC rectifier Spectrum analyzer Test result: spectrum of the voltage across a standard impedance in the LISN LISN “Earth” ground

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Fundamentals of Power Electronics 6 Chapter 10: Input Filter Design LISN C 1 C 1 C N C N R N R N Measurement points 50 50 AC line source Device under test 0.1 μ F 0.1 μ F L 1 L 1 R 1 R 1 1 μ F 1 μ F 50 μ H 50 μ H 5 5 LISN: “Line Impedance Stabilization Network,” or “artificial mains network” Purpose: to standardize impedance of the power source used to supply the device under test Spectrum of conducted emissions is measured across the standard impedance (50 above 150kHz) LISN example
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Ch10slides - Chapter 10 Input Filter Design 10.1...

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