Eas y- Aut omot ive Mo dul es Applic atio n N ote HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A AN 201 2 -0 9 Revision 1.3 Elect ric D rive T rain Edition Revision 1.3 Published by Infineon Technologies AG 81726 Munich, Germany © 2014 Infineon Technologies AG All Rights Reserved. LEGAL DISCLAIMER THE INFORMATION GIVEN IN THIS DOCUMENT IS GIVEN AS A HINT FOR THE IMPLEMENTATION OF THE INFINEON TECHNOLOGIES COMPONENT ONLY AND SHALL NOT BE REGARDED AS ANY DESCRIPTION OR WARRANTY OF A CERTAIN FUNCTIONALITY, CONDITION OR QUALITY OF THE INFINEON TECHNOLOGIES COMPONENT. THE RECIPIENT OF THIS DOCUMENT MUST VERIFY ANY FUNCTION DESCRIBED HEREIN IN THE REAL APPLICATION. INFINEON TECHNOLOGIES HEREBY DISCLAIMS ANY AND ALL WARRANTIES AND LIABILITIES OF ANY KIND (INCLUDING WITHOUT LIMITATION WARRANTIES OF NON-INFRINGEMENT OF INTELLECTUAL PROPERTY RIGHTS OF ANY THIRD PARTY) WITH RESPECT TO ANY AND ALL INFORMATION GIVEN IN THIS DOCUMENT. Information For further information on technology, delivery terms and conditions and prices, please contact the nearest Infineon Technologies Office (www.infineon.com). Warnings Due to technical requirements, components may contain dangerous substances. For information on the types in question, please contact the nearest Infineon Technologies Office. Infineon Technologies components may be used in life-support devices or systems only with the express written approval of Infineon Technologies, if a failure of such components can reasonably be expected to cause the failure of that life-support device or system or to affect the safety or effectiveness of that device or system. Life support devices or systems are intended to be implanted in the human body or to support and/or maintain and sustain and/or protect human life. If they fail, it is reasonable to assume that the health of the user or other persons may be endangered. Easy-Automotive Modules HV to LV DC/DC-Converter Kit Document Change History Date 01-2013 Version Author T. Reiter 1.0 S. Zeljkovic 1.1 T. Reiter T. Reiter 1.2 01-2014 1.3 07-2012 08-2012 T. Reiter Change Description Initial Version Updated Schematics to Rev2.2 Board Fixed ISAR order number. Buy online option. Updated Schematics to Rev2.3. Updated Figure 1 Update evaluation kit pictures, switching waveforms, and efficiency plot New chapter: short circuit tests We Listen to Your Comments Is there any information in this document that you feel is wrong, unclear or missing? Your feedback will help us to continuously improve the quality of this document. Please send your proposal (including a reference to this document) to: [email protected] Trademarks of Infineon Technologies AG EasyPIM™, EiceDRIVER™, HybridPACK™, OptiMOS™, TRENCHSTOP™ Application Note 3 AN2012-09 HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A Easy-Automotive Modules HV to LV DC/DC-Converter Kit Application Note 4 AN2012-09 HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A Easy-Automotive Modules HV to LV DC/DC-Converter Kit Table of Contents Page 1 1.1 1.2 Introduction ................................................................................................................................... 6 Safety Warning for Evaluation KIT .................................................................................................. 6 How to Order the Evaluation Kit ...................................................................................................... 6 2 2.1 2.2 2.3 Quick Start Guide .......................................................................................................................... 7 Mount System on a Cooling Plate ................................................................................................... 7 Connect Supplies and Load ............................................................................................................ 9 Recommended Test Setup and Equipment .................................................................................... 9 3 3.1 3.2 3.2.1 3.3 Feature Description ....................................................................................................................10 Key Features .................................................................................................................................10 Protection Features .......................................................................................................................11 Gate Driver not Ready and emergency turn-off implementation ..................................................12 Key Components BOM .................................................................................................................14 4 4.1 4.2 4.3 4.4 4.5 4.6 Function Description and Measurement Results ....................................................................15 Function Principle of Phase Shift ZVT Converter .........................................................................15 IGBT Leading Leg Transition ........................................................................................................17 IGBT Trailing Leg Transition .........................................................................................................19 Short Circuit Tests .........................................................................................................................22 Efficiency .......................................................................................................................................24 Efficiency with different Transformer Turn-Ratio (converter input voltage range adaption) .........25 5 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 5.10 5.11 Schematics ..................................................................................................................................27 Overview .......................................................................................................................................27 Gate Driver IGBT ..........................................................................................................................28 Oscillator .......................................................................................................................................29 DCL capacitor................................................................................................................................30 H-Bridge IGBT ...............................................................................................................................31 Synchronous Rectifier ...................................................................................................................32 Gate Driver Synchronous Rectifier................................................................................................33 ZVT Controller ...............................................................................................................................34 Transformer ...................................................................................................................................35 Aux Supply ....................................................................................................................................36 Assembly and Layout ....................................................................................................................37 6 References ...................................................................................................................................38 Application Note 5 AN2012-09 HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A Easy-Automotive Modules HV to LV DC/DC-Converter Kit Introduction 1 Introduction The Evaluation Kit “EASYKIT DCDC” was developed to support customers during their first steps in designing applications with the Easy Automotive H-Bridge power module. This Easy Module contains HighSpeed IGBT3 and Rapid Diode and is e.g. well suited for HV to LV DC/DC-converters in phase shift full bridge zero voltage transition (ZVT) DC/DC-converters up to 100 kHz and 3 kW. Such a phase shifted converter system is demonstrated in the Evaluation Kit and gives the customers important information about the specific characteristics of this HighSpeed IGBT Technology in this particular application. The application note contains general information about the operation of phase shift full bridge ZVT DC/DC converters, schematics as well as detailed experimental results from the Evaluation Kit. The information is intended to enable the customers to re-use and modify the Evaluation Kit design for their own specific requirements. 1.1 Safety Warning for Evaluation KIT Please read and understand the manual and the following safety warnings. The design operates with unprotected high voltages. Therefore, the Evaluation Kit may only be handled by persons with sufficient electrical engineering training and experience. The customer assumes all responsibility and liability for its correct handling and/or use of the Evaluation Kit and undertakes to indemnify and hold Infineon Technologies harmless from any third party claim in connection with or arising out of the use and/or handling of the Evaluation Kit by the customer. The Evaluation Kit is a sample to be used by the customer solely for the purpose of evaluation and testing. It is not a commercialized product and shall not be used for series production.. The Evaluation Kit is thus not intended to meet any automotive qualifications. Due to the purpose of the system, it is not subjected to the same procedures regarding Returned Material Analysis (RMA), Process Change Notification (PCN) and Product Withdraw (PWD) as regular products. See Legal Disclaimer and Warnings for further restrictions on Infineon Technologies warranty and liability. European legislation in relation to inter alia the restriction of hazardous substances (RoHS), waste from electrical and electronic equipment (WEEE), electromagnetic compatibility, as well as duties to comply with CE, FCC or UL standards do not apply to the Evaluation Kit and the Evaluation Kit may not fulfill such requirements.. 1.2 How to Order the Evaluation Kit The Evaluation Kit has Infineon Technologies Sales Product Number and can be ordered via Infineon Sales Partners. EASYKIT DCDC Order Number: SP001007734 The kit is also available in the online web shop: http://ehitex.com/Easy-Kit-DCDC_detail_451.html Figure 1 Picture of the “EASYKIT DCDC” Evaluation Kit. Application Note 6 AN2012-09 HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A Easy-Automotive Modules HV to LV DC/DC-Converter Kit Quick Start Guide 2 Quick Start Guide Before operating this Evaluation Kit two steps are necessary: 1. Mount system on a cooling plate 2. Connect aux supply, HV supply and LV load Please read the following instructions carefully in order to prevent damage on the Evaluation Kit. 2.1 Mount System on a Cooling Plate The power module can be attached directly on a cooling plate with a 50 um thick applied thermal grease (e.g. Fischer WLP). Detailed information on the mounting of the Easy Automotive Module can be found in [2]. The LV secondary side PCB area has to handle high currents up to 170 A and has to be cooled. The PCB is designed with thermal vias in the areas of the synchronous rectifier MOSFETs. A mounting on a cooling plate via a gap pad is recommended (e.g. Bergquist GapPad VO Ultra Soft 0.5mm or Kunze Ku-TCS50 0.5mm). Please take care that the pins of the connectors and capacitors do not generate a short circuit to the cooling plate. Please note that it is also required to cool the transformer windings as well as the core if the Evaluation Kit should run continuously at high load currents. Please contact Epcos/TDK for more information about mounting and cooling of the passive components. thermal grease Cooling System gap pad PCB gap pads transformer Figure 2 Recommended mounting concept of the Evaluation Kit. The module is mounted with standard thermal grease on the cooling system. The transformer core, windings as well as PCB area, where the secondary side MOSFETs are located, are connected via gap pads to the cooling system. A 3D file of a flat cooling plate according to Figure 2 can be requested from Infineon. The flat cooling plate can than be mounted easily e.g. on a water cooling system or the design files can be used as a starting point for a customer specific cooling system. For short term operation tests, it is also possible to operate the Evaluation Kit with active cooling of the power module only. The LV secondary side as well as the transformer is cooled from the intrinsic thermal capacitances only. Please take note that such an operation has certain risks as the design is not protected against any overtemperature events and thus it is only recommended for very experienced developers. The experimental results of Figure 3 with 45K delta T after running at 100A just 30s make clear that operation at high output current will be possible only for some seconds if the secondary side is cooled with free convection only! Application Note 7 AN2012-09 HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A Easy-Automotive Modules HV to LV DC/DC-Converter Kit Quick Start Guide a) Free Convection Active Cooling b) Thermal Picture c) d) e) Figure 3 Only for short term operation! Module mounted on cooling plate, passive components and secondary side PCB area in free convection (a). Illustrated window of the thermal picture (b). Thermal picture at 20°C room temperature after running 30 seconds at 50A/700W (c), 75A/1050W (d), and 100A/1.4kW output load (e). Application Note 8 AN2012-09 HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A Easy-Automotive Modules HV to LV DC/DC-Converter Kit Quick Start Guide 2.2 Connect Supplies and Load The Evaluation KIT has to be connected to a high voltage source (<350V, 20A) an auxillary supply (8..18V/1A) as well as a load (electric controlled or passive) with minimum 20V and up to 170A. Please take note that only the aux supply is reverse polarity protected up to -20V. The power terminals for the <350V DCL supply as well as the the 14V load are not protected against reverse polarity events. Thus the correct polarization according to Figure 4 is required. <350V supply (with 9:1 transformer) DCL+ DCLGND +14V load 8..18V/1A aux supply Figure 4 Supply and load connections to operate the Evaluation Kit. 2.3 Recommended Test Setup and Equipment Minimum to operate the Evaluation Kit: 400V 20A DC source 20V 1A DC source 40V >=170A DC electronic load Cooler plate, thermal grease, gap pads (see section 2.1) For investigations on the switching behavior additional: 4 channel scope (min. 100Mhz) Voltage probes (capable for measuring 650V), differential probes preferred. Rogowski current probe (e.g. CWT1) For investigations on the efficiency additional: 3 channel power analyzer OR 10mΩ 3W precision shunt 0.25mΩ precision shunt or 200A compensated current transducer 4 V-Meter with milli-volt rage Application Note 9 AN2012-09 HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A Easy-Automotive Modules HV to LV DC/DC-Converter Kit Feature Description 3 Feature Description 3.1 Key Features Full Bridge Phase Shift Converter with Synchronous Rectification (see Figure 5) 100 kHz Switching Frequency with HighSpeed IGBT3 and Rapid Diode Wide Input Voltage Range (160 V…350 V with 9:1 transformer) Output currents up to 170 A @14 V (limit of secondary side) High efficiency up to 93% incl. all aux supplies High efficiency over wide load and temp conditions e.g. >90% @160 V from 150 W to 2.3 kW Low system BOM (e.g. no resonating inductance, no active components in sec side snubber,…) EASYKIT DCDC EASY1B H-Bridge HV Supply System EPCOS Transformer 160V350V 12V Supply System Passive Current Transformer Isolation barrier 1ED Driver 1ED Driver 1ED Driver 1ED Driver Current Transfomer Controller 2ED Driver 2ED Driver Aux SMPS Figure 5 Topology of the EASYKIT DCDC Evaluation Kit. Application Note 10 AN2012-09 HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A Easy-Automotive Modules HV to LV DC/DC-Converter Kit Feature Description 3.2 Protection Features The protection features in this Evaluation KIT are very limited. This allows easier adoptions to different requirements. Please take note that testing beyond maximum rating may lead to device failures and thus is not recommended. Infineon will not take any liability for failures on the Evaluation KIT as well as damage on lab equipments. The design is not protected against: X Overtemperature (HV and LV side) X Overvoltage (HV and LV side) X Reverse energy flow (Energy transfer from LV to HV)* X Reverse polarity on power connectors X Short circuit (transformer and LV output short circuit protection is implemented) *the power stage is suitable for reverse energy transfer but the control can cause wrong PWM patterns, which can lead to failure of sync rectifier MOSFETs as well as the HighSpeed IGBT Module. Following protection features are implemented and activated: Gate Driver Undervoltage Lockout (UVLO) Gate Driver not Ready event locks all other Channels to avoid transformer saturation Overcurrent redundant in peak current mode control and emergency turn-off Aux supply short circuit and overcurrent with self restart (hiccup mode) Power transformer and LV output short circuit with self restart (hiccup mode) Application Note 11 AN2012-09 HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A Easy-Automotive Modules HV to LV DC/DC-Converter Kit Feature Description 3.2.1 Gate Driver not Ready and emergency turn-off implementation Transformer saturation is one of the most critical points in isolated DC/DC-converters. A transformer saturates at a certain B field which can be calculated with the volt-second product on the transformer divided by the effective core area and turn ratio (B=Vtrans*t/Ae*N). At Bsat the transformer saturates and causes a short circuit. Therefore, it is crucial to keep the transformer positive and negative magnetized with exact the same field strength. With this background it is now easy to understand that all gate drivers have to be turned-off immediately if one channel is not ready (e.g. in undervoltage lockout). Otherwise, if the others continue with switching operation, it will take typically only few µs until the transformer saturates and generates the next failure – a short circuit (worst case repetitive). In order to avoid such failures, it is common to implement several turn-off mechanisms in parallel. One possible concept is shown in Figure 6. Please note that only the basic concept is shown in an extract of one phase leg. An exemplarily dimensioning with all required filter elements can be seen in chapter 5. The concept is implemented with analog circuits but it can be transferred also to digital controlled converters. Phase Shift Controller Insulation IN+ IN- PWM_A PWM_B SS/EN Isense GND Drst CSS Teto 1ED nRST nRDY nFLT OUT GND1 GND2 Zeto IN+ IN- ZVTtrans 1ED CStrans nRST nRDY nFLT OUT GND1 GND2 Rsense Figure 6 Gate not ready and emergency turn-off concept. A small current sense transformer (CStrans) transfers via the sense resistor a current signal from the transformer primary current to the phase shift controller. With this signal it is possible to control the converter in peak current mode, which can avoid in general DC voltages on the transformer and saturation. But if one gate driver is not ready and thus is not able to turn-on than it is not useful to wait until the saturation happens. In this case the nRDY/nFLT output pulls all nRST inputs of the gate drivers to a low signal (all gate drivers turn-off immediately) and disables also via the diode (D rst) the controller. If all gate drivers are ready again, than the phase shift controller can start according to the programmed soft-start ramp with CSS. Due to the fact that saturation and short circuit is the major problem in such converters, an additional emergency turn-off loop is implemented. If the sensed current (Rsense) rises to excessive values (typ 150%..200% of the nominal turn-off current), than all the nRST of the gate drivers as well as the enable/softstart pin of the controller are pulled to zero immediately. This event can occur also in peak current mode controlled converters if e.g. the synchronous rectifier timing is not matching to the primary side and thus the primary side IGBTs are switching against the LV MOSFETs. After the failure is fixed, the controller can start again with the programmed soft start ramp. Application Note 12 AN2012-09 HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A Easy-Automotive Modules HV to LV DC/DC-Converter Kit Feature Description 400 40 350 35 300 30 250 25 200 20 150 15 nRST [V]; IN+ [V] 100 Vge [V] Vce [V]; IL [A] Figure 7 shows a measurement where the control of the converter was deactivated and the IN+ of the gate driver turned-on with a long single pulse (see black curve in the lower diagram). The transformer secondary side was short circuited for this experiment with a copper plate. After the gate driver and IGBT propagation delay the IGBT turn-on at approx 200ns (see low Vce voltage in black and rising Ic current in blue). At 400ns the threshold for the emergency turn-off is exceeded at about 50A. The softstart capacitor and thus the nRST Pin is discharged (see red curve). At 2000ns the IGBT is turned off. The gate driver discharges the Vge voltage and as a consequence the IGBT starts to desaturate at 2000ns. The gate driver continues to discharge the gate. In order to avoid device failure, it is important to turn-off the IGBT faster than the specified allowed short circuit time (typ. 5us). In this example the IGBT is switched off after being only 600ns in desaturation mode. This was a save turn-off event for the HighSpeed IGBT3 without the need for complex measures like soft turn-off. Please note that such events should not occur in common operating mode and not repetitive (<1000 times with 1s wait time is recommended). 10 50 5 0 6 5 4 3 2 1 0 -1 0 eto event detected 0 500 1000 1500 time [ns] 2000 2500 3000 Figure 7 Emergency turn-off measurement at transformer short circuit on secondary side. Application Note 13 AN2012-09 HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A Easy-Automotive Modules HV to LV DC/DC-Converter Kit Feature Description 3.3 Key Components BOM Part Description Manufactur er Status F4-50R07W1H3_B11A Easy 1B Automotive H-bridge with HighSpeed IGBT3 and Rapid Diode 650V Infineon In development 1ED020I12FA EiceDriver™ 2A Single Channel Gate Driver Infineon Productive IPB180N08S4-02 80V 2.2mΩ OptiMOS™ in TO263-7 Infineon In development 2ED020I12FA EiceDriver™ 2A Dual Channel Gate Driver Infineon Productive CRS Capacitor PressFIT Ceramic Ripple Vmax=450V; Ceff=10uF TDK/Epcos * T6973 3kW Phase Shift ZVT Transformer 9:1 TDK/Epcos * T7509 SMD Gate Driver Supply Transformers 1:1.1 5mm clearance/creepage TDK/Epcos * T7078 SMD Current Sense Transformer 1:100 5mm clearance/creepage TDK/Epcos * T7921-51 Output Choke 2.1uH, Isat=170A TDK/Epcos * Suppressor * For status and datasheets of the passive TDK/Epcos components please ask [email protected]. Application Note 14 AN2012-09 HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A Easy-Automotive Modules HV to LV DC/DC-Converter Kit Function Description and Measurement Results 4 Function Description and Measurement Results 4.1 Function Principle of Phase Shift ZVT Converter The phase shift ZVT converter operates at a fixed switching frequency and achieves, in an ideal operation, a lossless turn-on (zero voltage transition) due to intrinsic and optional external parasitic elements. In following only intrinsic elements are considered as it is implemented in the Evaluation Kit. How parasitic elements can help to avoid switching losses will be more understandable after a brief review of the switching states of the converter (see Figure 8). A) B) SW1 SW1 SR5 SR5 C1 Lleak Lleak Clv Chv Clv Chv SW4 SR8 C4 C) A: Energy Transfer (half cycle positive) B: Right Leg Transition (during dead time) C: Free Wheeling (half cycle) D: Left Leg Transition (during dead time) E (similar to A): Energy Transfer (half cycle negative) SW1 D2 SR5 SR6 Lleak Clv Chv SR7 SR8 F (similar to B): Right Leg Transition (during dead time) G (similar to C): Free Wheeling (half cycle) SR8 H (similar to D): Left Leg Transition (during dead time) A: Energy Transfer (half cycle positive) D) E) SW2 C1 D2 SR5 SR6 SR6 Lleak Lleak Clv Chv Clv Chv SW3 C3 SR7 SR8 SR7 Figure 8 Phase shift ZVT full-bridge DC/DC-converter topology with active H-bridge rectification. State A to H shows the current flow in half of a switching period. A) Energy Transfer (half cycle positive) The diagonal switches in the H-bridge are turned-on and energy from HV side is transferred via the transformer to the LV side. The transformer is magnetized in positive direction and the leakage inductance of the transformer (or optional an external Lres) is charged. B) Right/Leading Leg Transition (during dead time) After the energy transfer phase the right low-side switch is “hard” turned-off. The voltage across the switch is not changing immediately, as the output capacitances of the switches in the right leg clamps it. However, the parasitic capacitances of both low- and high-side switch are charged/discharged by the stored energy in the leakage inductance of the transformer. The ZVT condition is achieved if the stored energy in the leakage inductance is higher than the required energy to charge/discharge the capacitors. C) Freewheeling (half cycle) If the leakage inductance had enough stored energy the diode of the right high-side switch (D2) conducts. Otherwise, the switch (SW2) turn-on without ZVT, which is the case for light load conditions. During the freewheeling, the transformer windings on primary and secondary side are shorted. Application Note 15 AN2012-09 HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A Easy-Automotive Modules HV to LV DC/DC-Converter Kit Function Description and Measurement Results D) Left/Trailing Leg Transition (during dead time) Before entering the next energy transfer phase, the left leg transition is required. The left high-side switch is turned-off. Similar to the right leg transition, the parasitic capacitances clamps again the voltage slope. The parasitic capacitances of both switches are charged/discharged, respectively. E) Energy Transfer (half cycle positive) If the leakage inductance had enough stored energy to charge/discharge the parasitic capacitances of the left leg switches, the left low-side switch can turn-on at zero-voltage and the second half of the energy transfer phase starts (similar to state A). In this state the transformer is magnetized in the negative direction. The states F, G, H are similar to the explained states B, C, D but in reverse current direction from the point of view of the transformer. The corresponding current waveform on the primary side of the transformer (and thus leakage inductance) as well as the gate signals for the HV switches are shown in Figure 9. Each half bridge leg is driven by a quasi-complementary 50% PWM pulse pattern. In this example the right leg is phase-shifted to the left leg, which is in this topology the duty cycle command. The resulting half cycles (T/2) with this gate driving pattern can be clearly seen. The result is that the transformer, filter inductor, HV and LV capacitor is driven at two times of the switching frequency. The leakage inductance, which was required to achieve ZVT, limits the current slope when the transformer is switched from positive to negative cycle and vice versa. During this state the transformer is not transferring energy to the output. Consequently, the leakage inductance causes a “loss of duty cycle” (D Loss) at each half cycle. left leg T/2 0 SW3 SW1 SW3 SW4 right leg Gate signals Transformer Current (ILeak) T/2 Deff·T/2 Dloss·T/2 tD1 SW2 tD2 SW1 SW4 tD1 tD2 time Figure 9 Current waveform of the transformer primary side with the corresponding gate control signals of the 4 HV switches. Each half bridge leg is driven by constant 50% duty cycle. The phase shift of the right leg is here the duty cycle command for the converter energy transfer. The leakage inductance of the transformer leads to a loss of duty cycle (Dloss). The dead times are not only required to a avoid shoot through. As explained before, the parasitic capacitance has to be charged before the corresponding switch is turned-on. At “too short” dead times the converter generate hard switching conditions and will cause additional turn-on power losses. Application Note 16 AN2012-09 HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A Easy-Automotive Modules HV to LV DC/DC-Converter Kit Function Description and Measurement Results 4.2 IGBT Leading Leg Transition trail leg 0 SW3 SW1 SW3 SW4 SW2 SW1 SW4 lead leg Gate signals Transformer Current (ILeak) The IGBT leading leg transition is the transition from energy transfer into the freewheeling state. The leading leg turn-off event is indicated in Figure 10. time Measurement Trigger Point Figure 10 Leading leg turn-off transition in the converter operation cycle. DUT is SW4. The measured current and voltage waveforms of the IGBT (SW4) during this hard turn-off event are shown in Figure 11 for different input voltages and load currents. The turn-off overvoltage increases with higher currents and voltages. The tail current fall to zero within approximately 200ns and leads to very low switching losses. The approx. 70V voltage overshoot is quite low at 300V input voltage and high output load of 150A. The corresponding switching losses can be calculated with the given Eoff switching energy in the datasheet as this transition is equivalent to a standard inductive turn-off switching event. b) 400 17.5 350 15 300 250 12.5 200 10 150 7.5 100 5 50 Vce [V]; Vge [0.1V] 300 20 Ic [A] Vce [V]; Vge [0.1V] Converter Operating Point: 400 Vhv = 200V; Iout = 50A 350 2.5 0 -200 0 200 400 20 17.5 15 250 12.5 200 10 150 7.5 100 5 50 0 -400 Converter Operating Point: Vhv = 200V; Iout = 150A 2.5 0 600 Ic [A] a) 0 -400 -200 0 time [ns] 200 400 600 time [ns] c) d) Converter Operating Point: Vhv = 300V; Iout = 150A 400 350 17.5 350 17.5 300 15 300 15 250 12.5 200 10 150 7.5 100 5 50 2.5 0 -400 0 -200 0 200 time [ns] 400 600 Vce [V]; Vge [0.1V] 20 20 250 12.5 200 10 150 7.5 100 5 50 2.5 0 -400 Ic [A] Converter Operating Point: Vhv = 300V; Iout = 50A Ic [A] Vce [V]; Vge [0.1V] 400 0 -200 0 200 400 600 time [ns] Figure 11 IGBT turn-off in the leading leg transition at VHV=200V, ILV=50A (a); VHV=200V, ILV=150A (b); VHV=300V, ILV=50A (c); VHV=300V, ILV=150A (d). Application Note 17 AN2012-09 HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A Easy-Automotive Modules HV to LV DC/DC-Converter Kit Function Description and Measurement Results trail leg 0 SW3 SW1 SW3 SW4 SW2 SW1 SW4 lead leg Gate signals Transformer Current (ILeak) The leading leg turn-on event occurs within the dead time as indicated in Figure 12. time Measurement Trigger Point Figure 12 Leading leg turn-on transition in the converter operation cycle. DUT is SW2. The most interesting case is at very light load conditions in order to validate that the IGBT is switching at zero voltage conditions and therefore is without turn-on losses for leading leg. Figure 13 shows the voltage waveforms across the switch as well as the transformer primary current. It can be seen that zero voltage transition is achieved at very light output load of <30 W. The voltage Vce decreases to zero (and diode conducts) before the IGBT is turned-on (see Vge plateau voltage). As a result, the Evaluation Kit will switch in ZVT condition for the leading leg from about 1% to 100% output load. Contrary to MOSFETs, if the dead times are slightly increased, it will not have any impact on the switching efficiency as the IGBT does not reverse conduct. Due to such a zero voltage transition and conduction of the antiparallel diode, this transition is different to the specified Eon in the datasheet (datasheet is specifying hard turn-on incl. diode reverse recovery). For calculation of power losses it is recommended to neglect turn-on power losses of the leading leg completely. b) 400 1.75 350 300 1.5 300 1.5 250 1.25 250 1.25 200 1 200 1 150 0.75 100 0.5 50 0.25 Converter Operating Point: Vhv = 200V; Iout = 2A Vce [V]; Vge [0.1V] 350 0 0 -50 -0.25 -500 0 500 time [ns] 1000 Vce [V]; Vge [0.1V] 2 Ic [A] 400 2 Converter Operating Point: Vhv = 300V; Iout = 2A 1.75 150 0.75 100 0.5 50 0.25 0 Ic [A] a) 0 -50 -0.25 -500 0 500 1000 time [ns] Figure 13 IGBT turn-on in the leading leg transition at very light load conditions VHV=200V, ILV=2A (a); VHV=300V, ILV=2A (b). Zero voltage transition (ZVT) is achieved from 1% to 100% load in leading leg. This transition is lossless for the IGBT. Note: the current was measured with a Rogowski coil suitable for 600A peak; the SNR ratio is very low in this 1A measurement. Application Note 18 AN2012-09 HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A Easy-Automotive Modules HV to LV DC/DC-Converter Kit Function Description and Measurement Results 4.3 IGBT Trailing Leg Transition trail leg 0 SW3 SW1 SW3 SW4 SW1 SW2 SW4 lead leg Gate signals Transformer Current (ILeak) The IGBT trailing leg transition is the transition from freewheeling into the next energy transfer state. The trailing leg turn-off event is indicated in Figure 14. time Measurement Trigger Point Figure 14 Trailing leg turn-off transition in the converter operation cycle. DUT is SW1. Figure 15 shows the corresponding experimental results in the Evaluation Kit at different DCL voltages and converter output load currents. The IGBT is turned-off (see Vge and Ic) but the voltage is not rising to the DCL-voltage. This is because the secondary side transition is still ongoing and therefore clamping the voltage on the primary side. Compared to standard turn-off losses, as characterized in the datasheet, this transition is much more efficient as the turn-off voltage is much lower than the DCL-voltage. 150 6 100 4 50 2 0 0 -300 -200 -100 0 time [ns] 100 d) 10 200 8 150 6 100 4 50 2 0 0 -400 14 Converter Operating Point: Vhv = 300V; Iout = 50A 12 Converter Operating Point: Vhv = 200V; Iout = 150A 250 200 350 14 -300 -200 -100 0 time [ns] 100 200 350 14 Converter Operating Point: Vhv = 300V; Iout = 150A 300 250 10 250 10 200 8 200 8 150 6 150 6 100 4 100 4 50 2 50 2 0 0 0 0 -300 -200 -100 0 time [ns] 100 200 Vce [V]; Vge [0.1V] 12 -400 Ic [A] 8 350 300 Vce [V]; Vge [0.1V] 10 200 300 Vce [V]; Vge [0.1V] 12 250 -400 c) Converter Operating Point: Vhv = 200V; Iout = 50A Ic [A] Vce [V]; Vge [0.1V] 300 b) 14 -400 -300 -200 -100 0 time [ns] 12 100 Ic [A] 350 Ic [A] a) 200 Figure 15 IGBT turn-off in the trailing leg transition at VHV=200V, ILV=50A (a); VHV=200V, ILV=150A (b); VHV=300V, ILV=50A (c); VHV=300V, ILV=150A (d). The turn-off losses are reduced as the primary side transformer voltage (i.e. the voltage across the switch) is clamped by the parasitic elements in the secondary side. Application Note 19 AN2012-09 HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A Easy-Automotive Modules HV to LV DC/DC-Converter Kit Function Description and Measurement Results As the voltage clamping characteristic depends on system parameters, like secondary side stray inductance, parasitic capacitances, transformer leakage inductance, a general indication for those losses cannot be given from semiconductor manufacturers. The customer has to determine the trailing leg turn-off losses in the final setup. However, higher losses than the Eoff in standard inductive switching testbench will not occur and thus can be used as an indication of an absolute maximum value for this transition. trail leg 0 SW3 SW1 SW4 SW3 SW2 SW1 SW4 lead leg Gate signals Transformer Current (ILeak) The trailing leg turn-on event is shown in Figure 16. Ideally, the IGBT is turned-on again when the Vce voltage is zero but, as it can be seen from Figure 15, the voltage after the turn-off of the complementary switch was swinging back to zero and thus the DUT has to switch now at not ZVT conditions. time Measurement Trigger Point Figure 16 Trailing leg turn-on transition in the converter operation cycle. DUT is SW3. Figure 17 shows the measured voltage and current waveforms of the trailing leg turn-on IGBT (SW3). It can be clearly seen that the IGBT is switching the full DCL-voltage (no ZVT). But on the other hand the IGBT is always turning on when the current is zero. This is also a very efficient switching transition for the HighSpeed IGBTs because the power losses are caused only by the very low output capacitance of this technology as well as other parasitic capacitances in the setup. Furthermore, the HighSpeed IGBT3 switches relatively soft comparing to MOSFETs, which are typically applied in such applications and often lead to excessive ringing if ZVT is not achieved. Due to this efficient and smooth turn-on behavior it is recommenced not to increase the leakage inductance of the transformer, which leads just to minor improvements of the turn-on losses but increasing the turn-off losses in the trailing leg. Therefore, with respect to total system power losses an ideal ZVT transition (as always noted in literature targeting MOSFET designs) will not bring major advantages. Furthermore, no external Lres and optimized transformer leakage inductance gives the customers benefit in terms of system cost as well as effective duty cycle. Application Note 20 AN2012-09 HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A Easy-Automotive Modules HV to LV DC/DC-Converter Kit Function Description and Measurement Results 17.5 250 17.5 200 14 200 14 150 10.5 150 10.5 100 7 100 7 50 3.5 Vce [V]; Vge [0.1V] 250 0 0 200 400 time [ns] 600 350 Converter Operating Point: Vhv = 300V; Iout = 50A 21 50 3.5 0 800 0 0 d) 24.5 200 400 time [ns] 600 350 800 24.5 Converter Operating Point: Vhv = 300V; Iout = 150A 21 300 250 17.5 250 17.5 200 14 200 14 150 10.5 150 10.5 100 7 100 7 50 3.5 0 0 0 200 400 time [ns] 600 800 Vce [V]; Vge [0.1V] 300 Vce [V]; Vge [0.1V] 24.5 Converter Operating Point: Vhv = 200V; Iout = 150A 300 0 c) 350 21 Ic [A] Converter Operating Point: Vhv = 200V; Iout = 50A Ic [A] Vce [V]; Vge [0.1V] 300 b) 24.5 21 50 Ic [A] 350 Ic [A] a) 3.5 0 0 0 200 400 time [ns] 600 800 Figure 17 IGBT turn-on in the trailing leg transition at VHV=200V, ILV=50A (a); VHV=200V, ILV=150A (b); VHV=300V, ILV=50A (c); VHV=300V, ILV=150A (d). The IGBT turn-on at zero current and only the charge/discharge of the parasitic capacitance causes very low turn-on losses. Application Note 21 AN2012-09 HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A Easy-Automotive Modules HV to LV DC/DC-Converter Kit Function Description and Measurement Results 4.4 Short Circuit Tests A typical requirement in automotive DCDC converters is ruggedness against short circuits in the application. The case, where the control IC generates wrong or continues on output pulse patterns was already discussed in section 3.2.1. This chapter shows the results with a normal working control IC, gate driver and protection features, and the converter system was operated in typical short circuit conditions. Two examples of application short circuits are discussed in following: - Short circuit of the power transformer (i.e. similar to transformer saturation) - Short circuit in the wiring harness at the 12V converter output (i.e. similar to a short circuit in a load on LV power net) 500 75 450 67.5 400 60 350 52.5 300 45 250 37.5 200 30 Ic [A] Vce [V]; Vge [0.1V] Figure 18 shows the location and the IGBT current/voltage waveforms under an operation where a short circuit is applied at the transformer output. The IGBT is turned-on and the collector current Ic increases. The slope of the current is limited by the stray inductance of the transformer (about 1.2uH). After 200ns the overcurrent (short circuit) is detected and the IGBT turned-off. The maximum measured IGBT current in this design was about 50A, which is the implemented chip current of the power module and thus not critical in terms of current (also repetitive). The turn-off overvoltage at this measured 300V working voltage was about 450V. As the allowed peak voltage is specified 650V for the IGBT module, this event is also not critical. Due to the hiccup mode of the control IC the IGBT is switched repetitively (lower than 100kHz) into this application short circuit and thus the operation will be continued normally when the short circuit at the transformer is removed. Please note that the Evaluation Kit is not protected against overtemperature and thus long term operation under these conditions and insufficient cooling can damage the Evaluation Kit. 150 22.5 100 15 50 7.5 0 -400 0 -200 0 200 400 600 time [ns] 800 1000 1200 1400 Figure 18 Short circuit at transformer LV winding and measured waveform of IGBT leading leg at converter startup. The control IC is operating in hiccup mode and turn-on repetitive with lower than 100kHz the IGBTs into the short circuit. Figure 19 shows the most likely short circuit in typical applications, which is a short circuit in the cables or a load connected to the 12V output of the converter. After the short circuit occurs, the output voltage starts to decrease as the short circuit current discharges the output capacitors of the converter. The control loop detects this event first as a normal load step and thus increases the duty cycle. As the short circuit current is higher than the converter output current, the capacitors continuously discharges. After about 250us the control loop detects that despite transferring the maximum output current to the converter output node the output voltage further decreases. Thus, the converter operation is stopped and then the control try to restart the operation continuously with the hiccup mode (<< 100kHz). Application Note 22 AN2012-09 HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A Easy-Automotive Modules HV to LV DC/DC-Converter Kit Function Description and Measurement Results 350 52.5 300 45 250 37.5 200 30 150 22.5 100 15 50 7.5 0 0 -50 -7.5 -100 -15 -150 Ic [A] Vce [V]; Vge [0.1V] During this application short circuit test no critical turn-off overvoltage or high turn-off current (not higher than nominal current) was observed. 0 50 100 150 time [us] 200 250 300 -22.5 350 0 50 100 150 time [us] 200 250 300 350 600 Short Circuit Current [A] 500 400 300 200 100 0 -100 Figure 19 Short circuit at LV output cables. As the LV output voltage decreases rapidly after the short circuit occurs, the control loop starts with pulses at high phase shift (30 to 70us) than the phase shift (i.e. duty cycle) is reduced due to high currents and peak current mode control (70 to 280us) and finally at 300us the control IC stops operation into the short circuit. The highest current for the IGBT power module (leading leg half bridge) was measured <25A. Application Note 23 AN2012-09 HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A Easy-Automotive Modules HV to LV DC/DC-Converter Kit Function Description and Measurement Results 4.5 Efficiency The measured efficiency is shown in Figure 20. At light load conditions, constant losses (auxiliary power supply, core losses etc.) are dominant and cause low efficiency. Their impact on the efficiency is relatively low at higher output power. On the other hand, the resistive losses become then more dominant as these losses are proportional to the square of RMS output current The highest efficiency is reached at partial load, where the best balance of different losses relatively to the output power is achieved. The highest measured efficiency was 92.5% (at Vin = 160V and Iload = 50A). At a wide range of load currents from ~30A to full load, efficiency higher than 90% is achieved. The efficiency is very high taken into account that the power module was designed for best cost/performance ratio. For highest possible efficiency the HighSpeed IGBT should be replaced by the leading CoolMOS technology with lowest Rdson. Efficiency curves in Figure 20 are shifted to lower values when the input voltage of the converter is increased. This is caused by the lower phase shift (duty cycle) and longer freewheeling period followed by increased losses. In the design process, transformer turn ratio is determined by the maximum allowed duty cycle (minimum input voltage) and because of the wide range of input voltages, duty cycle is considerably shorter at the maximum input voltages. If the transformer turn ratio would be adapted for other input voltage range, a higher efficiency at high input voltages can be achieved. Due to the controller functionality (light load efficiency management), synchronous rectifier control is starting at load current of approximately 12 A output load. Up to this current only body diodes are conducting. 95 94 93 92 91 90 Efficiency [%] 89 88 87 86 85 84 Input Voltage 160V 200V 275V 350V 83 82 81 80 0 20 40 60 80 Output Current [A] 100 120 140 160 Figure 20 Efficiency incl. all aux power supplies at VLV=14V output voltage and 85°C cooling plate temperature under the Easy Automotive power module. Application Note 24 AN2012-09 HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A Easy-Automotive Modules HV to LV DC/DC-Converter Kit Function Description and Measurement Results 4.6 Efficiency with different Transformer Turn-Ratio (converter input voltage range adaption) The EASYKIT DCDC is a demonstrator only and thus is not optimized to customer specific application operating conditions. This section explains the relationship between different application input voltage ranges, transformer turn-ratio and efficiency. The best operating condition for a full bridge phase shift converter is achieved at a phase shift close to 180° (i.e. duty cycle 100%). In this condition the converter is operated nearly without freewheeling periods and is switching from energy transfer (diagonal switches on) to next energy transfer phase (the transitions are performed in the dead time). The phase shift full bridge converter is a buck derived topology and thus the highest voltage conversion ratio is also at phase shift 180° (duty cycle 1). As a consequence for a given input voltage range and output voltage range the transformer turn-ratio should be designed in a way that the converter is still able to transfer power from minimum HV input voltage to max required output voltage at this condition. At higher input voltages the efficiency decreases due to the lower phase shift. Therefore, in order to achieve the best performance, a final converter design should be always optimized to match the input/output voltage ranges. Table 1 notes some transformer turn-ratio suggestions for different operating ranges and explains the origin of the operation limits. Table 1 Suggested transformer turn-ratios for different operating conditions. HV input Voltage range Required LV output Suggested Transformer voltage turn-ratio (+) at min HV input 160V(*)..350V(#) / 14V 14V 9:1 250V(*)..450V(°) / 14V 14V 14:1 300V(*)..450V(°) / 14V 14V 17:1 Typ application Mild hybrid Full hybrid and EV DCDC after PFC stages (+) Equal characteristic (Ls, Bmax,…) to transformer platform family Epcos/TDK T6973. (*) limited by max duty cycle (i.e. close to 180° or 100%) (#) limited by turn-off overvoltage of LV rectifier switches and blocking voltage (80V MOSFETs in H-bridge configuration with small RC damping snubber in EASYKIT) (°) limited by voltage rating of HV capacitor Figure 21 shows the measured DCDC converter efficiency including all auxiliary supply with 9:1 and with 17:1 transformer at different input voltages. In this example just the transformer was replaced and all other parts were kept constant. Is can be clearly seen that an increasing HV input voltage leads to reduced efficiency, which is a result of reduced phase shift (duty cycle) at these higher input voltages (equivalent to lower voltage conversion ratio and thus longer freewheeling periods). With the changed transformer turn-ratio of 17:1 it is no more possible to transfer power at e.g. 200V input voltage (duty cycle > 100% is not possible). But due to the adjusted voltage conversion ratio, the operation at 300V or 350V is now closer to the ideal operation of 180° phase shift and leads to a much increased efficiency. This measurement demonstrates clearly that it is important to choose in a final system an adequate transformer turn ratio. Application Note 25 AN2012-09 HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A Easy-Automotive Modules HV to LV DC/DC-Converter Kit Function Description and Measurement Results 95 17:1 Transformer for 300V…450V* Vhv input voltage Fsw=100kHz Output Voltage 13.8V 94 Efficiency [%] 93 92 91 9:1 Transformer for 160V...350V Vhv input voltage 90 9:1 200V 300V 350V 89 88 200 400 600 800 1000 1200 Output Power [W] 1400 17:1 300V 350V 1600 1800 Figure 21 Efficiency incl. all aux power supplies. With the transformer turn ratio it is possible to optimize the converter efficiency for specific application operating requirements. Note 450V(*): higher input voltages may damage the DCL capacitor. Application Note 26 AN2012-09 HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A Easy-Automotive Modules HV to LV DC/DC-Converter Kit Schematics 5 Schematics 5.1 Overview Application Note 27 AN2012-09 HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A Easy-Automotive Modules HV to LV DC/DC-Converter Kit Schematics 5.2 Gate Driver IGBT Application Note 28 AN2012-09 HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A Easy-Automotive Modules HV to LV DC/DC-Converter Kit Schematics 5.3 Oscillator Application Note 29 AN2012-09 HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A Easy-Automotive Modules HV to LV DC/DC-Converter Kit Schematics 5.4 DCL capacitor Application Note 30 AN2012-09 HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A Easy-Automotive Modules HV to LV DC/DC-Converter Kit Schematics 5.5 H-Bridge IGBT Application Note 31 AN2012-09 HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A Easy-Automotive Modules HV to LV DC/DC-Converter Kit Schematics 5.6 Synchronous Rectifier Application Note 32 AN2012-09 HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A Easy-Automotive Modules HV to LV DC/DC-Converter Kit Schematics 5.7 Gate Driver Synchronous Rectifier Application Note 33 AN2012-09 HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A Easy-Automotive Modules HV to LV DC/DC-Converter Kit Schematics 5.8 ZVT Controller Application Note 34 AN2012-09 HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A Easy-Automotive Modules HV to LV DC/DC-Converter Kit Schematics 5.9 Transformer Application Note 35 AN2012-09 HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A Easy-Automotive Modules HV to LV DC/DC-Converter Kit Schematics 5.10 Aux Supply Application Note 36 AN2012-09 HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A Easy-Automotive Modules HV to LV DC/DC-Converter Kit Schematics 5.11 Assembly and Layout Application Note 37 AN2012-09 HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A Easy-Automotive Modules HV to LV DC/DC-Converter Kit References 6 References The referenced application notes can be found at http://www.infineon.com Direct link to the Easy Automotive site: http://www.infineon.com/autoeasy [1] Infineon Application Note AN2010-09, “Explanation of Technical Information”. [2] Infineon Application Note AN2009-01, “Easy PressFIT Assembly Instructions”. [3] Infineon Application Note AN2011-11, “Explanation for Traceability of the Easy Automotive Modules”. [4] T. Reiter, S. Zeljkovic, “Design of an Automotive 2.5kW HV to LV DC/DC-converter using HighSpeed IGBTs” EEHE Conference Electric/Electronic in Hybrid and Electric Vehicles, April 2012. [5] Zeljkovic; T. Reiter, D. Gerling, “Analysis of Rectifier Topologies for Automotive HV to LV Phase Shift ZVT DC/DC Converter” EPE-PEMC 2012. [6] S. Zeljkovic; T. Reiter, D. Gerling “Switching Behavior of IGBTs in Phase Shift Full Bridge ZVT DC/DC Converter” PCIM 2013. [7] A. Kopetz, D. Graovac, T. Reiter, “IGBT power modules update” Electric & Hybrid Vehicle Technology International, Jan 2013. Application Note 38 AN2012-09 HV to LV DC/DC-Converter Evaluation Kit with Easy Automotive Module F4-50R07W1H3_B11A w w w . i n f i n e o n . c o m Published by Infineon Technologies AG