Design of DC/DC Converters for 42V Automotive Applications J. Mark Christini, PE Senior Application Engineer, Electromechanical Products Ansoft Corporation Pittsburgh, PA
Outline Introducing the application: 42V automotive system Ansoft s tools for Power Electronics Design stages of a 42V system 1 2 3 Selection of of the system topology Selection of of components Design and simulation of of the entire system
Introducing the 42V System Automotive electrical systems will change drastically in next 10 years Demands for fuel economy and more electric power are driving cars to higher voltages Total power demand will triple in some cars from 800W today to average of 2500W and into kw range for peak demands in the future
Introducing the 42V System New equipment such as: electromechanical valve actuators, active suspensions, and drive-by-wire technology will require additional power These power requirements can be met more efficiently using higher voltages Active Suspension
Introducing the 42V System 42V automotive systems have a new DC voltage bus A dual 12-42V system will probably be needed for 10-15 years The DC/DC converter will be designed using Ansoft tools
Ansoft s Tools for Power Electronics A complete design solution! ANSOFT PEmag ANSOFT PEcad In In Progress!
Design Stages of of a 42V System 1 Selection of of the system topology 2 Selection of of components 2.1 Selection of of semiconductors 2.2 Selection of of Magnetic Components PEcad PEcad 2.3 Design and analysis of of Magnetic Components 2.3.1 Design optimization PEmag 2.3.2 Measured results 3 Design and simulation of of the entire system 3.1 3.2 Using switch level models Using simplified average models Simplorer
Design Stages of of a 42V System 1 Selection of of the system topology All three converters handle 42-12V loads (left to right) Only the bottom converter can handle 12-42V load (right to left) Number of converters chosen (three in this case) is based on a trade-off between cost and performance 3 Buck Buck Converter Converter Interleaving Interleaving Control Control Scheme Scheme
Design Stages of of a 42V System 2.1 Selection of of semiconductors Databooks Semiconductors (diodes and mosfets) must be chosen from a databook.
Design Stages of of a 42V System 2.2 Selection of of Magnetic Components ANSOFT PEcad PEcad and PEmag will be used to design/analyze the individual inductors.
2.2 Selection of of Magnetic Components PEcad Inputs: Specifications of the converter such as: voltage, current, duty cycle, and inductance PEcad Outputs: Losses, temperature, window filling
2.2 Selection of of Magnetic Components Defining the Waveform
2.2 Selection of of Magnetic Components Selecting Components in the Design Library (right mouse button) Choose all or part of libraries to be included: Libraries: AVX, Epcos, Magnetics, Micrometals, Philips, Siemens, Steward, TDK Core types: POT, RM, EE, EI. ETD, EFD, Toroidal, UU, EP Wires: solid or Litz Core material: from manufactures above
2.2 Selection of of Magnetic Components Specifying Design and Modeling Options (if needed) The user can specify many modeling options such as: gap with or without a bobbin planar or concentric consider 1D and/or 2D winding configurations max. number of parallel paths layer spacing
2.2 Selection of of Magnetic Components Exploring Results (I) Acceptable Ranges
2.2 Selection of of Magnetic Components Exploring Results (II)
2.2 Selection of of Magnetic Components Exploring Results (III)
2.2 Selection of of Magnetic Components PEmag link (I) 1. Save the Current Project 2. Select one of the Designs out of the List of Results
2.2 Selection of of Magnetic Components PEmag link (II) 3. Open PEmag/PEmag1D with the Selected Design
Design Stages of of a 42V System 1 Selection of of the system topology 2 Selection of of components 2.1 Selection of of semiconductors 2.2 Selection of of Magnetic Components PEcad PEcad 2.3 Design and analysis of of Magnetic Components 2.3.1 Design optimization PEmag 2.3.2 Measured results PEmag can further analyze the PEcad design. PEmag will automatically import the PEcad model. PEmag will analyze the resistance, inductance and capacitance of the magnetic component. PEmag will create a netlist for the magnetic component to be later used in Simplorer.
2.3 Design and analysis of of Magnetic Components Why Why a Model? PEmag Advanced Design Two examples Parallel Windings Gap Gap Effect Effect System Simulation System Simulation
2.3 Design and analysis of of Magnetic Components PEmag Input: Specifications of the Magnetic Component PEmag Output: Model of the Magnetic Component including geometry and frequency effects
2.3 Design and analysis of of Magnetic Components Parallel Windings Modeling: The Solution Short Circuit Test Secondary 1 Secondary 2 Primary Current Frequency
2.3 Design and analysis of of Magnetic Components Parallel Windings Modeling: The Solution Current @50 Hz @1 MHz
2.3 Design and analysis of of Magnetic Components Gap Effect Modeling: The Problem Flux Flux distribution Current density distribution
2.3 Design and analysis of of Magnetic Components Gap Effect Modeling: The Solution Could I increase the converter efficiency with this strategy? 1mm margin tape No margin tape
2.3 Design and analysis of of Magnetic Components Optimizing the Design. Air gap influence (II)
2.3 Design and analysis of of Magnetic Components Comparing Results (I)
2.3 Design and analysis of of Magnetic Components Comparing Results (II)
2.3 Design and analysis of of Magnetic Components Simplorer Link. Exploring the Model Netlist
Design Stages of of a 42V System 1 Selection of of the system topology 2 Selection of of components 2.1 Selection of of semiconductors 2.2 Selection of of Magnetic Components PEcad PEcad 2.3 Design and analysis of of Magnetic Components 2.3.1 Design optimization PEmag 2.3.2 Measured results
2.3.1 Design optimization DESIGN 1: 1 Wires close to gap DESIGN 2: 2 1 mm margin tape R DC = 0.28Ω R 50kHz = 5 Ω R DC = 0.32Ω R 50kHz = 1 Ω
2.3.2 Measured results DESIGN 1: 1 Wires close to gap DESIGN 2: 2 1 mm separation Efficiency = 91.7% (measured) Efficiency = 93% (measured) Power Saved 3W!!!
Design Stages of of a 42V System 1 Selection of of the system topology 2 Selection of of components 2.1 Selection of of semiconductors 2.2 Selection of of Magnetic Components PEcad PEcad 2.3 Design and analysis of of Magnetic Components 2.3.1 Design optimization PEmag 2.3.2 Measured results 3 Design and simulation of of the entire system 3.1 3.2 Using switch level models Using simplified average models Simplorer
Design Stages of of a 42V System 3 Design and simulation of of the entire system! Converter can be modeled with detailed switch level models or simplified average models for the mosfet, diode, and inductor Switch Level Simplorer Average Buck Model
Design Stages of of a 42V System 3.1 Using switch level models! PEcad and PEmag are better for switch level models! A switch level model is required for accurate loss calculation. PEcad PEcad PEmag Simplorer
3.1 Using switch level models Importing the Model Netlist into Simplorer
3.1 Using switch level models Simulation of One Converter with Simplorer: Comparison of Designs ref Type 3 Controller WP_LIN1 vout t Y t Macro21 + V VM2 ET1 Macro1 + EMWorkShop1 V EMWorkShop + A E2 Macro11 VM1 AM1 C2 R1 Model 1: no margin tape Model 2: with margin tape
3.1 Using switch level models Simulation of One Converter with Simplorer: Comparison of Designs! Two different load cases are considered to compare the two models! High load = 50A! Low load = 5A E2 Macro11 Macro1 Macro21 ref Type 3 Controller vout + V VM2 EMWorkShop + + EMWorkShop1 V VM1 AM1 A WP_LIN1 t Y t ET1 C2 R1 60.00 A I out = 50 A 50.00 40.00 30.00 20.00 10.00 I out = 5 A 0 1.800m 1.850m 1.875m 1.900m 1.925m 1.950m T 2.000m
3.1 Using switch level models Simulation of One Converter with Simplorer: Comparison of Designs! High load case = 50A! Power losses lower for case 1 (no margin tape) since DC resistance is lower I out = 50 A Power Losses = 2 W Power Losses = 3.5 W
3.1 Using switch level models Simulation of One Converter with Simplorer: Comparison of Designs! Low load case = 5A! Power losses lower for case 2 (with margin tape) since AC resistance is lower 60.00 50.00 40.00 30.00 20.00 10.00 I out = 5 A A 0 1.800m 1.850m 1.875m 1.900m 1.925m 1.950m T 2.000m Power Losses = 450 mw Power Losses = 350 mw
Design Stages of of a 42V System 3.2 Using simplified average models! Average models for switching components such as Mosfet and diodes will be provided in future release of Simplorer! PEcad and PEmag are not used for simplified average models Simplorer Average Buck Model Buck Converter Simplorer Average Buck Model Simplorer Average Buck Model
3 Design and simulation of of the entire system Simulation of Three Converters with Simplorer: Comparison of Designs Control ref! Complete switched level model with 3 converters! Converters can also be average model since there are only three multiphase converters in this example! Design details:! 42V 12V Architecture! 600W 1000W Load! High Efficiency E2 Macro11 Macro12 Macro1 Macro1 Macro21 + V VM1 + V VM2 Type 3 Controller vout C2 WP_LIN1 t Y Square_wave1 RT1 t ET1 Variable Load t Macro1 + V VM3 Macro13
3 Design and simulation of of the entire system Simulation of the System with Simplorer: Comparison of Switch level vs Average Model Results nearly same for both switch and average models Output voltage similar at start-up and at sudden load change at 1ms 18.00 15.00 Switch 12.50 10.00 7.50 5.00 2.50 0 0 0.250m 0.500m 0.750m 1.000m 1.250m 1.500m 2.000m U"C2" T 18.00 15.00 12.50 10.00 7.50 5.00 Average U"C2" 2.50 0 0 0.250m 0.500m 0.750m 1.000m 1.250m 1.500m 2.000mT
3 Design and simulation of of the entire system Simulation of the System with Simplorer: Comparison of Switch level vs Average Model Results nearly same for both switch and average models Output voltage similar at start-up and at sudden load change at 1ms However, average model is more than 10 times faster 13.00 12.50 12.00 11.50 11.00 10.50 10.00 13.00 12.50 12.00 Switch 0.900m 0.950m 0.975m 1.000m 1.025m 1.050m 1.100m Average U"C2" T U"C2" 11.50 11.00 10.50 10.00 0.900m 0.950m 0.975m 1.000m 1.025m 1.050m 1.100mT
33 Using switch level models Simulation of the System with Simplorer: Switch level information Ripple current can only be seen in a switch model Not provided with an average model 22.00 20.00 18.00 16.00 14.00 I"L2" I"L1" I"L3" 12.00 700.0u702.5u 705.0u 707.5u 710.0u 712.5u 715.0u T 717.5u720.0u 22.00 20.00 I"L2" I"L1" I"L3" AM1 18.00 16.00 14.00 12.00 700.0u702.5u 705.0u 707.5u 710.0u 712.5u 715.0u T 717.5u720.0u
Design Stages of of a 42V System 1 Selection of of the system topology 2 Selection of of components 2.1 Selection of of semiconductors 2.2 Selection of of Magnetic Components 2.3 Design of of Magnetic Components 2.3.1 Design Optimization 2.3.2 Measured Results 3 Design and simulation of of the entire system 3.1 Using simplified average models 3.2 Using switch level models
Summary Automotive electrical systems will change drastically in next 10 years For 42V DC/DC converters: PEcad can select the magnetic components PEmag can design and optimize the components Simplorer can simulate the entire system Ansoft tools offer a complete solution for start to finish design of 42V converters