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SWITCH-MODE POWER SUPPLIES AND SYSTEMS Silesian University of Technology Faculty of Automatic Control, Electronics and Computer Sciences Ryszard Siurek Ph.D., El. Eng. Lecture No 3

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Significant input parameters specified for the Power Supply input voltage range (e.g. 230V +10%,-15% or 90V – 260V wide range) input voltage range (e.g. 230V +10%,-15% or 90V – 260V wide range) input voltage type (single phase, three-phase, AC, DC or both) input voltage type (single phase, three-phase, AC, DC or both) input voltage frequency (e.g. 40Hz – 60Hz or 40Hz – 400Hz) input voltage frequency (e.g. 40Hz – 60Hz or 40Hz – 400Hz) maximum input RMS current (in worst case) maximum input RMS current (in worst case) inrush current (when switching on) – e.g. 30A (typical value) inrush current (when switching on) – e.g. 30A (typical value) IRIR t U IN I IN Input current for resistive load

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Electro-Magnetic Interference (EMI) emission Power Supply Conducted interference voltages and currents (measured in the range of 0,15 MHz to 30 MHz) Supply line Radiated electromagnetic interference field (measured in the range of 30 MHz to 1 Ghz)

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Electromagnetic noise (EMI) Conducted noise (interference) Conducted noise (interference) - noise voltage measured across 50 resistance in normalized circuit built in a so called artificial mains built in a so called artificial mains - frequency range: 150kHz - 30 MHz - frequency range: 150kHz - 30 MHz - measurement unit: dB - measurement unit: dB Z CN = 20log [dB ] Z CN - conducted noise level Z CN = 20log [dB ] Z CN - conducted noise level Radiated noise (interference) Radiated noise (interference) - measurement of electromagnetic field strenght in the air - frequency range: 30MHz - 1GHz - measurement unit: dB V/m Z RN = 20log [dB V/m) Z RN – radiated noise level Noise limits and methods of measurement are presented in EN standarts, e.g.: PN-EN55022 – Information technology equipment. Radio disturbance PN-EN55022 – Information technology equipment. Radio disturbance characteristics. Limits and methods of measurement. characteristics. Limits and methods of measurement. U N 1 V E N 1 V/m

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Power Supply under test Ro U IN Artificialmains Selective milivoltmeter measurement range: 0,15 – 30MHZ ININ ENEN Electromagnetic field spectrum analyser in the range 30MHz – 1GHz Shielded chamber EMI measurement equipment

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Typical measurement results for conducted disturbances (interference)

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Power Factor total power apparent power S [VA] = I Z 2 reactive power Q [var] = I (X - X ) 2 LC real power P [W] = I R 2 PF = cos U IN, I IN t t f = 1/T = 2 f t = 2 f t T Formulas valid for sinusoidal waveforms Power Factor U I

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U I1I1 U IN, I IN t total power (apparent) S = I 1RMS U U I2I2 Uwe, Iwe t P (real power) PF = SP total power S = I 2RMS U = P real power = I 1RMS I 2RMS PF < 1 (0,6 – 0,75) I-st harmonic of I(1) I-st harmonic of I 1 (1) t ( ) t ( ) Ks = I(1) I 1 (1) RMS I I 1RMS Form Factor PF = Ks cos PF = Ks cos

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Distorted current waveform results in: - apparent power increase (it means higher current consumption from the mains) - more current harmonics in supplying wires which may cause the distortion of normally sinusoidal voltage waveshape - increase of current flow through the neutral conductor in multi-phase power grids Formal regulations limiting harmonic content in AC supply input current for electrical and electronic appliances of output power in the range from 75W to 1000W are effective since the year Obligatory standard: EN Electromagnetic Compatibility (EMC) – Limits for harmonic current Electromagnetic Compatibility (EMC) – Limits for harmonic current emissions (equipment input current up to and including 16A per phase) emissions (equipment input current up to and including 16A per phase) Some means should be applied to improve input current shape in Power Supplies – Active Power Factor Correction (PFC) Active Power Factor Correction (PFC)

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Immunity against external electromagnetic disturbances Power Supply electrostatic discharge elctromagnetic fields fast transients - BURST (amplitude up to 4 kV) lightning on AC input conductors (surges)

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Power supply systems ~ ~ U1 U2 Un Load #1 Load #2 Load # k U IN Batteries Central Power Supply Centralized Supply System - safety - safety - functionality - functionality - reliability - reliability - cost - cost

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Load # 1 Power Supply # 1 ~ ~ ~ ~ ~ ~ U1 U2 U3 Un ~ ~ ~ ~ Batteries U IN UPS Multiple Centralized Power System - safety - safety - functionality - functionality - reliability - reliability - cost - cost Power Supply # 2 Power Supply # N Load # 2 Load # 3 Load # 4 Load # 5 Load # N Load # N+1

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Load # 1 12V - 24V U 1i U 2i Low power DC-DC converter switching regulator with auxilliary outputs U 1n U 2n U 3n ~ ~ 230V 50Hz 12V - 24V DC input Low voltage distributed power supply system Low voltage distributed power supply system (high voltage distributed power supply system) - safety - safety - functionality - functionality - reliability - reliability - cost - cost Low power DC-DC converter Load # 2 Load # N

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