SWITCH-MODE%20POWER%20SUPPLIES%20AND%20SYSTEMS

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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.

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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 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)

IR
IIN
Input current for resistive load
UIN
t
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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)
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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
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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
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Typical measurement results for conducted
disturbances (interference)
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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
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I1
UIN, IIN
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
I2
t
PF Ks cosf
PF lt 1 (0,6 0,75)
total power S I2RMS U P real power
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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 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)

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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)
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Power supply systems
- safety - functionality - reliability -
cost
Central Power Supply
Load 1
Load 2

U1
UIN

U2
Un
Batteries
Load k
Centralized Supply System
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- 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 N1
Multiple Centralized Power System
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- 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)