application notes: 1 bg2 c C universal gate drive prototype board description: the bg2 c is a two channel gate drive circuit designed for use with high frequency optimized igbt modules. the bg2 c utilizes powerex vla507 or vla513 hybrid gate driver s and vla106 series dc to dc converters to provide efficient switching of modules rated up to 3 00a . the hybrid gate drivers include high speed opto - couplers with typical propagation delay times as short as 200ns for con trol signal isolation . the hybrid dc to dc converter s provide ful ly isolated control power for each driving channel . features: ? 3 a or 5a peak output current ? 2500vrms isolation for control power and signals ? standard amp mta .100 input /output c onnector s ? operates from a single 15 v dc or 24 vdc supply ? wide output volt a g e swing +15v/ - 8v ? low parts count C only 17 parts for two channels ? compact size 2.7 x 2. 4 ( 69mm x 61 mm) ordering information: bg2 c - 30 15 is a kit with a bare bg2 c board, two vla507 and two vla106 - 15242 s bg2c - 50 15 is a kit with a bare bg2c board, two vla 513 and two vla106 - 15242 s applications: bg2 c is designed for use with powerex nfh series and cm*** dus - 12f high freq uency igbt modules. ? vla 106 - 15242 dc to dc converter for operation with 15 vdc control power ? vla 106 - 24242 dc to dc converter for operation with 24 vdc control power second release : july 10, 2012 gate driver part number peak drive current (i op ) minimum r g typical application * (igbt module rating) dc/dc converter vla507 +/- 3a 3.9 up to 100a vla513 +/- 5a 2.0 up to 300a * compatible igbt module depends on voltage rating, switching frequency and selected r g . refer to powerex application notes for details. note: for high frequency applications using modules with current ratings larger than 300a the powerex vla502-01 driver is recommmended vla106-15242 for 15 vdc input vla106-24242 for 24 vdc input bg2c application guide
2 interface buffer 1 2 6 7 8 opto coupler control input 180 ? v cc v o v ee fig ur e 1: vla50 7 /vla5 13 block diagram circuit e xplanation : the bg2 c is a basic two channel gate driver designed around the recommended application circuit s for the powerex vla507 and vla5 13 hybrid igbt gate drivers in combination with eithe r vla106 - 15242 or vla106 - 24242 isolated dc to dc converter s . a functional block diagram of the vla50 7 /5 13 hybrid gate driver s is shown for reference in f igure 1. these gate drivers are optimized for use with powerex nf h series and cm**dus - 12f igbt modules . th e drivers use a high speed open collector type opto - coupler to provide 2500vrms isolation of control signals. the output stage is designed to provide high current gate drive with the appropriate on and off - state bias voltages for large igbt modules. for additional detailed information on the characteristics and operation of these gate drivers please refer to the individual device data sheets. figure 2 shows a block diagram of the vla106 - 15242 and vla106 - 24242 hybrid dc to dc converters. the se two devices are identical except that vla106 - 15242 is designed to operate from a 15 vdc input and the vla106 - 24242 is designed to operate from a 24 vdc input. these dc to dc converters use a transformer to provide 2500vrms isolation for gate drive power. the converters regulated 24vdc output is split using a resistor and zener diode to provide +15.8v and - 8.2v for the hybrid gate driver. for additional detailed information on the operation of the hybrid dc to dc converters please see the individual device d ata sheets. component selection: designation typical value description example: mfg./pn z1, z2, z3, z4 16v, 1w gate voltage surge protection 1n4745 c1, c2, c3, c4, c5 390 ? f, 35v power supply filter C electrolytic, low impe dance panasonic eeu - fc1v391s cn1, cn2** mta .100 input and gate connections amp 640457 - 6 ** recommended mating connector amp cst - 100 housing p/n 770602 - 6 with crimp contact 770666 - 2. figure 2 : vla 106 - 15242, vla106 - 24242 block diagram voltage regulator current limiter oscillator 10 11 8 3 2 1 3.3k v cc com v ee rectifier v z =8.2v 24v 9 v in + - cn1 +v l in2 +v s gnd in1 cn2 g1 e1 g2 e2 c3 c4 figure 3: bg2c schematic and component selection + c2 z1 r g z2 c1 + + vla507/vla513 1 vla106 - 15242/vla106 - 24242 2 5 8 c5 z 4 z 3 r g + + 11 8 3 1 vla106 - 15242/vla106 - 24242 vla507/vla513 1 2 5 8 1 3 8 11
3 a complete schematic and co m ponent selection guide for the bg2 c is shown in figure 3 . the board will normally be operated with two input voltage sources. a 5v logic source (+v l ) provides drive for the high speed opto - couplers inside the hybr id gate driver s . a control power supply (+v s ) provides power for the gate driver and is connected to the primary side of the dc to dc converter s at pins 8 , 9 and 10 , 11 . the + v s source is decoupled with a low impedance electrolytic capacitor c 1 . the cap acitor is connected close to the input pins of the dc to dc converter s to provide a stable , well - filtered dc source . a 390 f capacitor was selected for c 1 to provide the required ripple current and filtering assuming a maxim um driven load and a significan t distance to the main filter capacitor of the +v s supply. these capacitors will be larger than necessary if the driven load is smaller or the v s supply main filter capacitors are nearby. the dc to dc converter s pro vide isolate d gate drive power which co nsists of + 1 5 . 8 v (v cc ) at pin 3 and - 8.2 (v ee ) at pin 1 with respect to common at pin 2. the gate drive power supplies are decoupled using the low impedance elect rolytic capacitors c 2 , c 3 , c 4 , and c 5 . it is very important that these capacitors have low e nough impedance and sufficient ripple current capability to provide the required high current gate drive pulses. the 390 f low impedance cap acitors used on the bg2 c are sized to supply 5 a gate pulses at a 6 0 khz rate. if the application is operating at l ower frequency or lower peak current it may be possible to reduce the size of these capacitors. the isolated v ee and v cc supplies provided by the dc to dc converters are connected to the hybrid gate drivers at pins 6 and 8 to provide gate drive power . th e hybrid gate driver amplifies the control input signal and produces high current gate drive at pin 7 . the gate drive current is adjusted by selecting the appropriate series gate resistance (r g ). r g will normally be adjusted to provide suitable drive for the module being used considering dynamic performance, losses and switching noise . for more information on selecting r g see powerex igbt module application notes. protection against gate voltage surges is provided by z 1 , z 2 , z 3 , and z 4 . these zener dio des also help to control short circuit currents by shunti ng miller current away from the gate . interface circuit requirements : a typical interface circuit for the bg2 c is shown in f igure 4 . a single control power supply (+v s ) is connected to pin 5 of c n1 with its common at pin 6. this supply provides all of the gate drive power for both channels via the h ybrid dc to dc converter s . the current draw n from the +v s supply will v a ry from less than 1 00ma to more than 500m a depending on the switching freque ncy and size of igbt being driven. consult the hybrid gate driver application notes for details on determining the required supply current for the gate driver. the gate driver supply current can then be converted into current drawn from the +v s supply us ing the efficiency specification on the dc to dc converter data sheet. a 5v logic supply is connected at pin 1 of cn1 and shares the same common at pin 6 of cn1 as the 15v control supply. the 5v supply is directly connected to pin 2 of the hybrid gate dri ver which is internally connected to the anode of the led i n the high speed opto coupler. the control signal interface is designed for use with standard 5v cmos logic. the control input signals at pins 2 an d 3 of connector cn1 are used to turn the igbts o n and off. these signals are active low which means that the gate driver output will be high (igbt on) when they are pulled low. these control pins are connected directly to pin 1 of the hybrid gate driver which is connected internally through a 180 lim iting resistor to the cathode of the led in the high speed opto coupler (see figure 1) . when the control signal is pulled low , current flows from the 5v logic supply through the led to turn the gate drivers output on. the control pins must be pulled low with a buffer that is capable of sinking at least 1 6 ma in order to turn on the high speed opto coupler inside the hybrid gate driver . a cmos buffer that actively pulls its output high in the off state (74hc04 or similar) gnd cn1 +v l in2 fo +v s in1 cmos type buffer must sink 15ma g1 e1 g2 e2 figure 4: bg2c external wiring diagram rc filter to remove noise on fault signal rc~10us to logic level control circuits cn 2 c1 c2e1 igbt module e2
4 is recommended for maintaining go od common mode noise immunity. open collector drive that allows in1 and in2 to float will degrade common mode noise immunity and is therefore not recommended. printed circuit layout: figure 5 shows the layout of the bg2 c two channel gate driver board. the compact 2.7 x 2. 4 circuit board with only 17 components clearly demonstrates the advantage of using hybrid gate drivers and dc to dc converters. one important feature is the use of three ground plane islands for the regions of the pcb having high vo ltage differences. t wo of the islands are tied to the igbt emitter/circuit common ( pin 2 of the dc to dc converter s ) of each output channel. the third isla nd is connected to logic interface common at pin 6 of cn1. t his layout provides shielding to help p revent undesirable coupling of noise between the control side and the gate drive channels. additional information: d etailed information about the operation and electrical characteristics of the vla50 7 and vla5 13 hybrid gate drivers can be found on the in dividual device data sheets. electrical characteristics such as input voltage range, efficiency , and output voltage regulation of the vla106 - 15242 and vla106 - 24242 dc to dc converters can also be found on the individual device data sheets. i nformation ab out calculating gate drive current and selection of series gate resistors (r g ) can be found in the general igbt module and gate drive application notes. for applications using higher current igbt modules refer to the application notes for the vla50 2 - 01 hy brid gate driver and bg2a reference design. all of the se documents are available on the powerex website at www.pwrx.com . for design assistance with any of the products covered in this application note contact powerex at (724) 925 - 7272 and request application engineering . for product pricing and availability call the power line: 1 - 800 - 451 - 1415. component side s older side figure 5: bg2 c p rinted circuit board layout
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