Version 4.1 SHEET 1 3208 1348 WIRE -352 -64 -400 -64 WIRE -64 -64 -352 -64 WIRE 96 -64 16 -64 WIRE 112 -64 96 -64 WIRE 192 -64 112 -64 WIRE 320 -64 256 -64 WIRE 384 -64 320 -64 WIRE 432 -64 384 -64 WIRE -400 0 -400 -64 WIRE 320 0 320 -64 WIRE 432 0 432 -64 WIRE 96 16 96 -64 WIRE -128 96 -176 96 WIRE 0 96 -48 96 WIRE 48 96 0 96 WIRE 96 144 96 112 WIRE -176 208 -176 96 WIRE -400 352 -400 80 WIRE -176 352 -176 288 WIRE -176 352 -400 352 WIRE 96 352 96 224 WIRE 96 352 -176 352 WIRE 320 352 320 64 WIRE 320 352 96 352 WIRE 432 352 432 80 WIRE 432 352 320 352 WIRE -400 400 -400 352 FLAG -400 400 0 FLAG 0 96 V_gate FLAG 112 -64 V_drain FLAG 384 -64 V_out FLAG -352 -64 V_in SYMBOL ind -80 -80 M90 WINDOW 0 5 56 VBottom 2 WINDOW 3 50 51 VTop 2 SYMATTR InstName L1 SYMATTR Value 100µ SYMATTR SpiceLine Rser=1m SYMBOL nmos 48 16 R0 SYMATTR InstName M1 SYMATTR Value BSC600N25NS3 SYMBOL diode 192 -80 M90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName D1 SYMBOL cap 304 0 R0 SYMATTR InstName C1 SYMATTR Value 100µ SYMBOL res 416 -16 R0 SYMATTR InstName R_Load SYMATTR Value 10R SYMBOL voltage -400 -16 R0 SYMATTR InstName V_in SYMATTR Value 100V SYMBOL voltage -176 192 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 WINDOW 3 -120 109 Left 2 SYMATTR Value PULSE(0 10 0 10n 10n 4u 10u) SYMATTR InstName V_control SYMBOL res -32 80 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R1 SYMATTR Value 2R SYMBOL res 80 128 R0 SYMATTR InstName R_FET_Isense SYMATTR Value 1m TEXT -432 472 Left 2 !.tran 10m TEXT -408 -536 Left 2 ;click on run\nthen click on "V_gate" to plot its Voltage\nclick on the plot window, then on plot settings/add plot pane.\nthen click on "V_drain" to plot its Voltage\nZoom the time axis so you can see the individual cycles\nyou can see the FET drain getting pulled low every time it is turned on.\nclick on the plot window, then on plot settings/add plot pane.\nthen click on the inductor to plot its current.\nclick on the plot window, then on plot settings/add plot pane.\nthen click on the diode to plot its current.\nthen click on the R_FET_Isense to plot its current.\nthis shows the inductor current going either through the FET or through the diode\nclick on the plot window, then on plot settings/add plot pane.\nthen click on "V_out" to plot its Voltage. TEXT 104 -776 Left 5 ;The Boost SMPS topology. TEXT -400 -576 Left 4 ;Instructions TEXT 800 -96 Left 4 ;Uses of this topology. TEXT 808 -32 Left 2 ;As this topology has the inductor on its input side, \nthere is less high frequency noise in its input current.\nand the input current is more under control.\nFor these reasons this topology is often used to implement a \nPFC (power factor correction) input stage of a power supply,\nThe purpose of PFC is to make the input current a sine wave \nin phase with the mains input voltage, \nIf you wish to commercially sell your product in the UK you need to \nimplement PFC to get CE marking.\nYou can see an example of PFC using the boost topology to implement PFC, \nin the SMPS section of this website. TEXT 640 -520 Left 2 ;At the start of a cycle, the FET is turned on so the circuit applies the input voltage to the inductor, \nthis builds the inductor current up,\nthe FET is then turned off, so the inductor current then switches to the diode,\nthese current pulses going thru the diode, create the output voltage, \nThe output voltage will settle to a voltage above the input voltage,\nThe settled output Voltage is calculated from the voltage across the inductor averaging to zero Volts \nover a cycle, as otherwise the circuit has not settled to its steady state condition.\nYou could say that the output voltage has been boosted above the input voltage. \n \nThis simulation is the circuit in its simplest form with no control loop, \nno synchronous rectification, no input output isolation, and a DC input voltage, \nits too simple to be a practical circuit, \nbut I have deliberately kept things simple in order to explain the basic topology. TEXT 768 -560 Left 4 ;A bit more detail. TEXT -120 -704 Left 4 ;The boost topology boosts its output Voltage above its input voltage.\nStart off with the "Instructions" section to plot some waveforms, \nThen the rest of the text might make more sense.