SWITCHMODE POWER SUPPLIES AND SYSTEMS Lecture No 1

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

Program of the course Lecture No 1 - Lecture No 2 - Lecture No 3 - Lecture No 4 - Lecture No 5 - Lecture No 6 - General overview of power supplies, basic functions, static and dynamic parameters related to the output protection circuits (overcurrent, overvoltage etc. ), additional functions and indications, paralleling of power supplies, redundancy Input parameters specified for power supplies, Electomagnetic Noise emission, Power Factor, Immunity against electromagnetic disturbances, general overview of power supply systems Linear regulator in comparison to switching one, analysis of basic topology – step-down switching regulator, general equations and waveforms Analysis of step-up and flyback switching topologies, basic equations and waveforms, problem of discontinuous current (magnetic flux) flow Switching converters, pulse power transformer, analysis of single-ended forward converter, transformer reset circuits, transformer saturation

Lecture No 7 - Lecture No 8 - Lecture No 9 - Lecture No 10 Lecture No 11 - Lecture No 12 - Push-pull converter analysis, transformer operation explanation on hysteresis curve, core saturation problems, bridge an half bridge converters Single-ended flyback converter analysis, parasitic (leakage) inductance problems, multi-output power supplies Output filter components - capacitors, inductors, influence on switching regulator performance Power losses in magnetic components, skin and proximity effects Pulse transformer designing basis – flyback, forward and push pull converter, power losses in switching regulator, power losses reduction Regulated switching converters, closed feedback loop analysis

Recommended books and articles 1. Abraham I. Pressman - Switching Power Supply Design, Second Edition, Mc. Graw-Hill, New York, 1998 2. Billings K. - Switchmode Power Supply Handbook, Mc. Graw-Hill, New York, 1989 3. Texas Instrument - Power Supply Design Seminars (1996 to 2007), to view or download go to: power. ti. com (Support/Training/Seminar Materials) 4. Ferenczi O. - Zasilanie układów elektronicznych. Zasilacze impulsowe, WNT, Warszawa, 1989 5. Pałczyński B. , Stefański W. - Półprzewodnikowe układy i urządzenia techniki impulsowej, WKL, Warszawa, 1973

Basic requirements for low and medium power DC Power Supplies General configuration of the Power Supply hazardous/lethal voltage area safety low voltage area (ELV or SELV) -15% - +10% = ~ ~/ regulated voltages U 1 primary secondary circuit(s) U 2. . isolated output . Un input/line voltage AC or DC isolation barrier output DC voltages =

Essential functions performed by the typical Power Supply n n n Delivering of one or several output voltages with certain load capabilities, mostly DC voltages in the range of 3 V to 48 V Protection against electric shock – sufficient isolation of low voltage outputs from hazardous supply/line voltage Output voltage/voltages regulation against input voltage and load changes

Output voltage static (steady state) parameters Equation describing the influence of most important factors on the output voltage DUout = d. Uout x DIo + d. Uout x DUwe + d. Uout x DT d. I o d. Uwe d. T Load regulation coefficient %Uout DIo (Iomin – Iomax) Presented usually in technical data sheets Line regulation coefficient %Uout DUwe (Uwemin – Uwemax) Presented usually in technical data sheets Temperature coefficient %Uout deg Presented usually in technical data sheets (1. 1)

Ripple and noise – observed within the range of several hundreds of Hz Uwy 10 ms - 100 Hz t ms

Output voltage dynamic parameters Output voltage ripple & noise output voltage – mean value DUwyp-p basic ripple 5 10 15 switching ripple 20 25 30 Magnified output voltage waveforms observed within the range of several hundreds of k. Hz

Dynamic output voltage swing related to load current step change load current output voltage load current step change output voltage dynamic reaction output voltage static change load regulation

Start-up overshoot) Uout low load Uo heavy load t