Line Rectification and Capacitor Input Filters For Direct-off-Line Switchmode Power SuppliesOverviewWhat is Direct-off-Line?Switchmode vs. LinearTypes of Switchmode SuppliesTypical Off-line Dual Voltage Rectifier, Filter CircuitPowerPoint PresentationCharacteristicsSlide 9DesigningSlide 11Slide 12SimulationSlide 14Slide 15CalculationsMore Design ParametersApplicationsSlide 19Line Rectification and Capacitor Input Filters For Direct-off-Line Switchmode Power SuppliesOverview•Switchmode Supplies vs. Linear Supplies•Characteristics of typical Direct-off-line Circuit for Switchmode Supplies•Characteristics of Switchmode Supplies•Simulation•Calculations•ApplicationsWhat is Direct-off-Line?•Power supply operates directly from AC line•No transformer prior to rectification and filteringSwitchmode vs. LinearSwitchmode LinearNear constant efficiency and power loadConstant current loadWide input voltage range Low costLow heat generation Low noiseHigh reliability Easy to useSmall size transformer Large bulky transformerFrequency 100/300 kHz Frequency 50/60 HzTypes of Switchmode Supplies•Flyback topology•Forward topology•Half Bridge topology•Push-Pull topology•Full-Bridge topologyTypical Off-line Dual Voltage Rectifier, Filter CircuitOff-lineAC Power LineSeries ResistanceESRDC-DC ConverterLoadCharacteristics•Voltage Operation (120Vac/240Vac)–120V operation for voltage doubler–240V operation for full-bridge rectifier•Effective Series Resistance–Source resistance – reduce peak currents 20mOhms – 600mOhms.–Inrush Limiting thermistor – used for startup–1OhmCharacteristics•Constant Power Load–Output voltage fixed under steady state conditions•Near Constant efficiency for load•Rising Current•Resistance Factor–Parameter used for calculating current loadsDesigning•Effective Input Current Ie•RMS Input Current Iin(rms)•Capacitor Current (Icap)•Peak Input Current (Ipeak)•Capacitor Size (Ce)•DC Output voltage (Vo)DesigningDesigningSimulationE1D1D2D3 D4RSCeVM1.V [V] Vload.V [V] RS.R [Ohm] t [s] 0.25k-25500.1k0.15k0.2k0 50m5m 10m15m20m25m30m35m40m+ VVM1Simplified Capacitive Input Filter w/ Single-PhaseFull/Wave Bridge Rectifer and Lumped Total EffectiveSource Resistance.Converter loadRLR := 425C := 375uAMPL := 0.240416305603426kFREQ := 5070,7%RMSVinRMSVinRMS.VAL t [s] 0.2k-202550750.1k0.13k0.15k0.18k0 10.2 0.4 0.6 0 .8VinRMS.VAL 0.169913 kR := .42MEAN VALUEVout_DCVout_DC.VAL t [s] 0.25 k-25500.1k0.15 k0.2k0 10.2 0.4 0 .6 0.8Vout_DC.VAL 0.2321 03k70,7%RMSIcap_rmsIcap_rms.VAL 2.07 848Icap_rms.VAL Ce.I [A] t [s] 30-505101520250 50m5m 10m 15m 20m 25m 30m 35m 40m70,7%RMSIeIe.VAL 2.1609 2AIpeakW+WM1SimulationIpeak.I [A] t [s] 30-505101520255m 50m10m 15m 20m 25m 30m 35m 40m 45mWM1.P [W] t [s] 4k-0.5k00.5k1k1.5k2k2.5k3k3.5k5m 50m10m 15m 20m 25m 30m 35m 40m 45mSimulationCalculations•Given parameters: Vin(rms) = 170 V• η = 0.7• Rs = 0.42 Ω•Pout = 250 W• F = 50 Hz•To find the minimum capacitance size of Ce, from Fig. 1.6.7, assume capacitance/Watt is 1.5 uF/W.•Ce = (1.5 uF)*(250 W) = 375 uF•The input power Pin can be found from the efficiency η.•Pin = Pout/η = 357 W @ 100% of load•Using Eq. #2, the effective input current Ie = 2.1 A•Using Eq. #4, the resistance factor Rsf = 150 Ω∙W•From Fig. 1.6.4 w/ 100% load, Rsf ratio yields Iin(rms)/Ie = 1.48. The input current is:•Iin(rms) = (2.1 A)*(1.48) = 3.11 A•From Fig. 1.6.5 w/ 100% load, Rsf ratio yields Icap(rms)/Ie = 1.3. The capacitor current is:•Icap(rms) = (2.1 A)*(1.3) = 2.73 A•From Fig. 1.6.6, Rsf ratio yields Ipeak/Ie = 4.6. The peak input current is:•Ipeak = (2.1 A)*(4.6) = 9.66 A•As discussed earlier in the DC Output Voltage and Regulation For Rectifier Capacitor Input Filters section, when using Fig. 1.6.7:•(2πf)*(Ce)*(RL) > 50•So the load resistance RL >= 425 Ω. I used RL at its minimum value.•From Fig. 1.6.7 w/ Pin = 357 W and Rs = 0.42 Ω, the ratio Vo(dc)/Vin(rms) = 1.34. The filter DC output voltage is: •Vo(dc) = 228 V.More Design Parameters•RMS Ripple current rating–Prevents temperature rise in capacitor•Ripple Voltage–Allows wide input voltage range for load•Voltage Rating–Component voltage limit•Holdup time–Time output remains once input is shut offApplications•Typically used in Digital Electronics–Cell Phones–PDA’s–PC’s–Laptops–CD/DVD PlayersApplications3.6 W Cell Phone Charger from Power Integration’s