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SWITCH -MODE POWER SUPPLIES AND SYSTEMS

SWITCH -MODE POWER SUPPLIES AND SYSTEMS. Lecture No 3. Silesian University of Technology Faculty of Automatic Control, Electronics and Computer Sciences Ryszard Siurek Ph.D., El. Eng. Significant input parameters specified for the Power Supply. I R. I IN.

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SWITCH -MODE POWER SUPPLIES AND SYSTEMS

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

  2. Significant input parameters specified for the Power Supply IR IIN 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 frequency (e.g. 40Hz – 60Hz or 40Hz – 400Hz) maximum input RMS current (in worst case) inrush current (when switching on) – e.g. 30A (typical value) Input current for resistive load UIN t

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

  4. Electromagnetic noise (EMI) • Conducted noise (interference) - noise voltage measured across 50W resistance in normalized circuit built in a so called „artificial mains” - frequency range: 150kHz - 30 MHz - measurement unit: dBm ZCN = 20log [dBm] ZCN - conducted noise level • Radiated noise (interference) - measurement of electromagnetic field strenght in the air - frequency range: 30MHz - 1GHz - measurement unit: dBmV/m ZRN = 20log [dBmV/m) ZRN – radiated noise level Noise limits and methods of measurement are presented in EN standarts, e.g.: PN-EN55022 – Information technology equipment. Radio disturbance characteristics. Limits and methods of measurement. UN 1mV EN 1mV/m

  5. EMI measurement equipment Shielded chamber IN UIN Power Supply under test Artificial mains Ro EN Electromagnetic field spectrum analyser in the range 30MHz – 1GHz Selective milivoltmeter measurement range: 0,15 – 30MHZ

  6. Typical measurement results for conducted disturbances (interference)

  7. Power Factor UIN, IIN U I T t f = 1/T f = 2pfDt Dt „total power” apparent power S [VA] = I Z 2 reactive power Q [var] = I (X - X ) 2 L C f PF = cos f real power P [W] = I R 2 Power Factor Formulas valid for sinusoidal waveforms

  8. UIN, IIN I1 I-st harmonic of I1(1) U I1(1)RMS I1RMS t Ks = Form Factor Dt (f) total power (apparent) S = I1RMS•U P (real power) Uwe, Iwe S P I1RMS I2RMS PF = = U t I2 PF = Ks cosf PF < 1 (0,6 – 0,75) total power S = I2RMS•U = P real power

  9. 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 2001. Obligatory standard: EN 61000-3-2 Electromagnetic Compatibility (EMC) – Limits for harmonic current 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)

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

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

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

  13. - safety - functionality - reliability - cost Low power DC-DC converter Load # 1 Low power DC-DC converter ~ 12V - 24V ~ U1i 230V 50Hz Load # 2 U2i switching regulator with auxilliary outputs 12V - 24V DC input U2n U1n Load # N U3n Low voltage distributed power supply system (high voltage distributed power supply system)

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