Goals of the SeminarYou Will Learn The value of designing your own DC/DC power conversion circuits Basics of power conversion design Simulation of key thermal and electrical parameters Tradeoffs and pitfalls in DC/DC design Passive component selection for optimum results LED driver design considerations Layout optimization Agenda DC-DC Buck DesignLab 1: Design a Buck converter Lab 2: Optimize a Buck converter BreakLab 3: Investigate Thermals Vishay : Capacitors and Inductors for DC-DC Designs High Power Buck DesignLab 4: Higher Power Designs Lunch Vishay : Discrete Semiconductors Boost/Buck BoostLab 5: Buck Boost, LM3668 Break: Powering LED'sLab 6: LED WeBenchLab 7: Driving a string of LEDs Review, Questions and FeedbackLab 1 Design a Buck Converter with WeBench Power DesignerMyths and Legends DC-DC Power conversion is black magicNo, but RF design is DC-DC Design requires a special skill setMost everything is learned in a first year engineering course on circuit theory. DC-DC Design requires special toolsSpecial tools like MathCad and PSpice exist, but are not necessary, WeBench Power Designer and Excel are more than enough DC-DC Designs takes weeks to develop implement and testToday we will design modify and test a complete designBasic DC-DC Operation 2 or more Switches 1 or more Inductors 1 CapacitorHow the Buck Converter Works2 SW IOUT V1 SW I2 SW I1 SW I Duty Cycle% 35122 . 4= = =INOUTVVDNot so scary mathSelecting the InductortiL VAA=itV LAA=INOUTOUT IN OUT INVVV V D V V V ) ( ) (==MIN MAX I I i= ARipple CurrentS Ft1= AS INOUTOUT INF i VVV V L- A-=1) (S INOUTOUT INF i VVV V L- A --= ) (INOUTVVD=Not so scary math Pick the InductorInductanceInput VoltageOutput Voltage6 . ) 5 . 1 4 (. 122 . 4) 2 . 4 12 (- - --= L32 . 42 . 48 . 7 - = LuH L 10 =IN VOUT VLi AS FInductor Ripple CurrentSwitchingS INOUTOUT INF i VVV V L- A --= ) (Tradeoffs in Speed and Size You cant have it allInductanceInput VoltageOutput VoltageIN VOUT VLi AS FInductor Ripple CurrentSwitchingS INOUTOUT INF L VVV V i- --= A ) (i L VVV V FINOUTOUT INA - --= ) ( SS INOUTOUT INF i VVV V L- A --= ) (Output Capacitor SelectionInductanceInput VoltageOutput VoltageC ESL ESR OUT OUT OUT V V V VOUT A + A + A = ASLOUTINOUTL OUTF CIVESLLVVESR I VCESLESR- -A= A- = A- A = A0 8IN VOUT VLi AS FInductor Ripple CurrentSwitchingHz FAESLHVm A000 , 600 8 - --O -EfficiencyLosses Switching Losses In the IC Fixed In the Diode Depends on the Diode Conduction Losses Inductor Losses DCR Diode LossesINOUTPPAVG L I DCR - ) D I V AVG DFWD- - 1EfficiencyLosses Switching Losses In the ICINOUTPPFuture PDB LM22676LM22676Screen clipping taken: 10/12/2008, 11:29 PMLM22676 circuitBasic circuitSW1:Internal to the LM22676SW2:D7Ind:L3Cap:C32LM22676 circuitWhats all this other stuff?C27, C31: Input Capacitors Enable PinC28:Boost CapacitorR42, R41: Feedback Voltage Resistors Future Electronics Power Training BoardNational LM22676: Standard Async BuckNational LM3668: Sync Buck BoostBackground Future Electronics Power Training Board Power Input Output adjust for LM22676Background Future Electronics Power Training BoardNational LM3410: Boost Dimming capabilitiesBackground Future Electronics Power Training Board 3 Lumiled RebelsBackground Future Electronics Power Training BoardNational LM3150: Sync BuckBackground Future Electronics Power Training Board We will focus on this circuit.Background Future Electronics Power Training BoardBackground Each section of the board has its own Ground Each section of the board has test points to measure input current Each section of the board has test points to measure across the Inductor Each section of the board has a scope probe jack on the outputLab 2 Optimize a Buck converter using WeBench Power DesignerLM22676 LayoutLM22676 circuitWhere does the current go?LM22676 LayoutLM22676 LayoutLab 3 Using WeBthermPower PassivesTypes of Converters PWM Hysteretic Constant On Time Constant Off Time PFMHow the Synchronous Buck Converter Works2 SW IOUT V1 SW I Duty Cycle% 10122 . 1= = =INOUTVVD1 SW I2 SW IWhy Synchronous? Diode Losses If the Diode is on 90% of the time, a better switchyields a better efficiency ) D I V AVG DFWD- - 1Pick the InductorInductanceInput VoltageOutput VoltageS INOUTOUT INF i VVV V L- A --= ) (510 3 ) 10 4 (. 122 . 1) 2 . 1 12 (xL- - --=710 4 . 12 . 18 . 10xL - =uH L 1 =IN VOUT VLi AS FInductor Ripple CurrentSwitching FrequencyOutput Ripple Output RippleOutput Voltage OUT Vi AInductor Ripple CurrentESR I V L OUTESR - A = AESR V ESR OUT - = A 10 * 4 .ESR V ESR OUT - = A 4Output Capacitor SelectionInductanceInput VoltageOutput VoltageC ESL ESR OUT OUT OUT V V V VOUT A + A + A = ASLOUTF CIV C- -A= A0 8IN VOUT VLi AS FInductor Ripple CurrentSwitchingHz F 000 , 600 84- -LM3150 DesignFuture PDB Minimum CircuitFuture Demonstration BoardFuture PDB Minimum CircuitFuture Demonstration BoardSW1:Q4SW2:Q3/D4Ind:L1Cap:C1, C2LM3150 Current FlowFeedbackEnableBoost Diode and CapInput CapsLM3150 Current FlowSW1:Q4SW2:Q3/D4Ind:L1Cap:C1, C2LM3150 LayoutLM3150 LayoutLab 4 Lab 3: Design and Optimize a Synchronous Buck ControllerLunchPower DiscretesHow the a Boost Converter Works% 534 . 64 . 3 6=++ = =++ D OUTD IN OUTV VV V VD% 344 . 62 . 24 . 64 . 2 . 4 6= =++ = =++ D OUTD IN OUTV VV V VDOUT V2 SW I1 SW I1 SW I2 SW IIts BackSelecting the InductortiL VAA=itV LAA=D V V IN) ( =260 . 4 . 652 . 40 . = - = - = A L I iRipple CurrentS Ft1= A65 . 16 . 1 26 .53 . 3=--=- A-=SINF iD VL53 . = =++ D OUTD IN OUTV VV V VD652 .46 .3 .) 54 . 1 (3 .) 1 (= =

=

=DIIOUTLHow the Synchronous Buck Boost Converter Works As a Buck2 SW IOUT V1 SW I1 SW I2 SW IHow the Synchronous Buck Boost Converter Works As a BoostOUT V% 35122 . 4= = =++ D IND IN OUTV VV V VD3 SW I4 SW I3 SW I4 SW ILM3668 PDB CircuitLM3668 PDB CircuitSW1:Internal to the LM3668SW2:Internal to the LM3668Ind:L2Cap:C26LM3668 PDB CircuitC23:Input CapacitorPin 6:EnablePin 11:VselectPin 12:FeedbackLM3668 PDB CircuitLM3668 LayoutLM3668 LayoutLab 5 Lab 5: Buck Boost, LM3668How the Boost Converter WorksOUT V2 SW I1 SW I1 SW I2 SW ILM3410 PDBLM3410SW1:Internal to the LM3410SW2:D12Ind:L4Cap:C40LM3410LM3410LM3410Lab 6 Lab 6: WeBench LED Designer LM3410 Boost LED DriverTHANK YOU!!Layout Parasitic Inductance of bypass caps