# Switched Mode Power Conversion – EE5203

**Title :Switched Mode Power Conversion**

Power Electronics (EC3040)

**1)** Introduction

**2)** Semiconductor Devices Classification, Behavioural classification, Physical, Classification, Silicon Controlled Rectifier Symbol, terminals, and their method of connection, Static v-i curve, Features of SCR behavior when gate turn is used (a) Gate turn on conditions, pulse duration (b) latching current, Turning off an SCR — holding current — forced commutation — natural commutation, Other methods of turn-on (a) dv/dt turn-on (b) Increasing junction temperature (c) Irradiating the junction, Dynamic characteristics — turn-on transients (a) Delay time (b) Voltage fall time, Dynamic characteristics — turn-off transients, Gate characteristics, SCR ratings

**3)** Features of power processing systems Ideal waveforms of DC and AC sides, Figures of merit – DC side (a) ripple factor (b) average value, Figures of merit – AC side, (a) Harmonic factor (b) Distortion factor (c) THD (d) Power factor (e) Crest factor, Power in switching circuits, Efficiency

**4)** Simple circuits SCR with a R load, R-L load, general solution, R-L load and freewheeling diode — continuous and discontinuous conduction Modes

**5)** AC to DC conversion systems Two- pulse & three-pulse Midpoint converters- circuits and method of triggering — triggering angle — conduction angle — extinction angle, R load — average voltage — control characteristic — mains current —various figures of merit—comparison with single pulse converter—power and power factor — reactive power requirement, R-L load, infinite inductance — ac side current waveform — figures of merit — average voltage — inverter mode, Commutation analysis — overlap angle — commutation drop , Factors affecting overlap angle, inverter mode of operation, inverter limit, R-L load with finite time constant — conditions for continuous and discointinuous conduction — determining L for a particular ripple, Use of freewheeling diode, R-L-E load — L for continuous conduction in case of L-E load. Four-quadrant operation of DC machine, Single-phase bridge converter – Connection — series connection of two 2-pulse midpoint converters, R load — dc and ac performance, R-L load with infinite inductance — dc and ac performance, Commutation, Inverter mode of operation, Three-phase bridge converter – Circuit connection — series connection of two 3-pulse midpoint converters — sequence of triggering and conduction, R-load — limits of continuous and discontinuous conduction — average voltage — line current, Commutation — analysis — voltage drop, Inverter mode of operation — inverter limit

**6)** DC to DC Conversion Systems

Buck Converter – Circuit configuration, working and waveforms — voltage gain — inductor current ripple — relation between input and output currents, Discontinuous conduction mode, Estimation of output voltage ripple, L-C filters

Boost Converter- Circuit configuration, working and waveforms — voltage gain — inductor current ripple — relation between input and output currents, Estimation of

output voltage ripple, L-C filters

Buck-Boost Converter – Circuit configuration, working and waveforms — voltage gain — inductor, current ripple — relation between input and output currents, Estimation of output voltage ripple, L-C filters

Cuk Converter – Circuit configuration, working and waveforms — voltage gain — inductor current ripple — relation between input and output currents, Estimation of output voltage ripple, L-C filters, Four quadrant DC drive

**7)** DC to AC conversion systems Inverter configuration, numbering of switches, 180deg conduction with R, R- L loads — need for freewheeling — waveforms, 120deg conduction, harmonic elimination PWM, Sinusoidal PWM (a) Understanding the scheme (single phase half bridge), (b) Frequency and amplitude modulation index, (c) Bridge converters — Unipolar and Bipolar switching, (d) Three phase bridge, (e) Harmonics in the output voltage, (f) Restriction on values of mf , Programmed SHE, PWM — Calcluation of notch angles

**8)** AC to AC Conversion Systems – AC Voltage Controller Configuration and operation, R-load, R-L load — control range, Application to on-load tap changing