GENERAL CONSIDERATIONS FOR IGBT AND INTELLIGENT …

1 GENERAL CONSIDERATIONS forIGBT and INTELLIGENT PowerModulesH-Series IGBT and IntelligentPower Modules are based onadvanced thirdgeneration IGBT and free-wheeldiode technologies. The generalguidelines for power circuit,snubber and thermal systemdesign are essentially the same forboth product families. This sectionwill cover these GENERAL applicationissues. The sections that follow willgive specific details for eachproduct Numbering SystemMITSUBISHI SEMICONDUCTORS POWER MODULES MOSGENERAL CONSIDERATIONS FOR IGBT AND INTELLIGENT POWER MODULESCM(1)100(2)D(4)24(6) CM100DY-24H is a 100 Ampere, 1200 Volt, Dual IGBT ModuleDevices: CM = IGBT Module PM = IPM Current Rating lC (Amperes) For IPM: H = Single D = Dual C = Six in one R = Seven in one IGBT Module: H = Single D = Dual T = Six E3 = Brake H(8)Examples.

2 Y(5)PM(1)600(2)H(3)SA (5)(8)120(7)PM600 HSA120 is a 600 Ampere, 1200 Volt, Single IPM(1)(2)(3)(4)(5)(6)(7)(8)Outline or Minor Change U = U-Series For IGBT Module: Voltage, VCES Volts (x50) For IPM: Voltage VCES Volts (x10) For IGBT Module: F = 250V Trench Gate H = Total Performance H-Series IGBT Module For IPM S = Third Generation V = V-Series Power Circuit DesignIn high power systems rapidturn-on and turn-off operationsproduce harsh dynamicconditions. The power circuit,snubbers, and gate drive must bedesigned to deal with extreme di/dtand dv/dt stresses.

3 Excessivetransient voltages can occur ifleakage inductance in the powercircuit and snubbers is notminimized. Ground loops andcapacitive coupling can causeserious noise problems. Anappropriate mechanical andelectrical layout is essential forreliable and efficient operation ofIGBT and INTELLIGENT Turn-off Surge VoltageTurn-off surge voltage is thetransient voltage that occurs whenthe current through the IGBT isinterrupted at turn-off. To examinethis, consider the inductive loadhalf-bridge circuit shown inFigure In this test circuit thetop IGBT is biased off and thebottom device is switched on andoff with a burst of pulses.

4 Eachtime the lower device is turned on,the current in the inductive load(IL) will increase. When the lowerdevice is turned off, the current inthe inductive load cannot changeinstantly. It must circulate throughthe free-wheel diode of the upperdevice. When the lower deviceturns back on, the load current willcommutate back to the lowerdevice and begin to ramp upagain. If the circuit was ideal andhad no parasitic inductance, thevoltage across the lower device(VC2E2) at turn-off would increaseuntil it reached one diode dropabove the bus voltage (VCC).

5 Theupper device s free-wheel diodewould then turn on stopping thevoltage from increasing real power circuitshave parasitic leakage Figure a lump inductance(LB) has been added to thehalf-bridge circuit to simulate theeffect of parasitic bus the lower device turns off theinductance LB resists thecommutation of the load current tothe free-wheel diode of the upperdevice. A voltage (VS) equal toLB x di/dt appears across LB inopposition to increasing current inthe bus. The polarity of this voltageis such that it adds to the DC busvoltage and appears across thelower IGBT as a surge voltage.

6 Inextreme cases, the surge voltagecan exceed the IGBT s VCES rating and cause it to fail. In areal application the parasiticinductance (LS) is distributedthroughout the power circuit but theeffect is the Free-Wheel DiodeRecovery SurgeA surge voltage similar to theturn-off surge can occur when thefree-wheel diode that the lower IGBT inFigure is off and that the loadcurrent (IL) is circulating throughthe free-wheel diode of the upperIGBT. When the lower device turnson, the current in the free-wheeldiode of the upper device (IFWD)decreases as the load currentbegins to commutate to the lowerdevice and becomes negativeduring reverse recovery of thefree-wheel diode.

7 When thefree-wheel diode recovers, thecurrent in the bus is quicklydecreased to zero. The situation issimilar to the turn-off operationdescribed in Section Theparasitic bus inductance (LB)develops a surge voltage equal toLB x di/dt in opposition to thedecreasing current. In this case,the di/dt is related to the recoverycharacteristic of the free-wheeldiode. Some fast recovery diodescan develop extremely highrecovery di/dt when they are hardrecovered by the rapid turn on ofthe lower IGBT. This condition,commonly referred to as snappy recovery, can cause very hightransient voltages.

8 Mitsubishi thirdFigure Half-Bridge Circuit with Parasitic Bus InductanceMITSUBISHI SEMICONDUCTORS POWER MODULES MOSGENERAL CONSIDERATIONS FOR IGBT AND INTELLIGENT POWER MODULES+VCC+-+-+-VSVOFFLB GATE SEMICONDUCTORS POWER MODULES MOSGENERAL CONSIDERATIONS FOR IGBT AND INTELLIGENT POWER MODULES generation H-Series IGBT modules have a new, ultra fast,soft recovery free-wheel diode thatvirtually eliminates problems withsnappy Ground LoopsGround loops are caused whengate drive or control signals sharea return current path with the maincurrent.

9 During switching, voltageis induced in power circuit leakageinductance by the high di/dt of themain current. When this happens,points in the circuit that should beat ground potential may in fact beseveral volts above ground. Thisvoltage can appear on the gates ofdevices that are supposed to bebiased off causing them to turn order to avoid this problem,careful referencing of gate driveand control circuits is required. Inapplications using large IGBT modules high di/dts make itincreasingly difficult to avoidground loop shows a circuit withpotential ground loop problems.

10 Inthis circuit the ground return for thegate drive passes through the mainpower bus. This circuit issuitable for use with low currentsix-pack devices because theyhave minimal inductance in thenegative bus and a relatively lowpower circuit di/dt. However, evenin this case a strong off-bias of-5 to -15V is recommended. [Note1] At higher operating currents,voltages induced in the bus duringswitching are likely to causeground loop noise problems in thecircuit of Figure Figure the recommendedconnection of low side driversusing a single gate drive powersupply.