57962l

8/7/2019 57962l

1/11

8/7/2019 57962l

2/11

Sep 1998

5.1 Output Current Limit

When using hybrid gate driversRG must be selected such that theoutput current rating (I OP ) is notexceeded. If R G is computed usingEquation 5.1 then I OP will not beexceeded under any condition.

Equation 5.1Conservative equation for mini-mum R G

RG(MIN) = (VCC + VEE )/IOP

Example:With V CC = 15V and-VEE = 10V R G(MIN) forM57958L will be:

RG = (15V + 10V)/5A = 5 ohms

In most applications this limit isunnecessarily conservative.Considerably lower values of R Gcan usually be used. The

expression for R G(MIN) should bemodified to include the effects ofparasitic inductance in the drivecircuit, IGBT module internalimpedance and the finite switchingspeed of the hybrid drivers outputstage. Equation 5.2 is an improvedversion of Equation 5.1 forRG(MIN).

Equation 5.2Improved equation for R G(MIN)

RG(MIN) = (VCC + VEE )/ IOP - (R G)INT -

Large IGBT modules that containparallel chips have internal gateresistors that balance the gatedrive and prevent internaloscillations. The parallelcombination of these internalresistors is R G(INT) . R G(INT)

ranges from 0.75 ohm in largeIGBT modules like CM600HA-24Hto 3.0 ohms in smaller modules likeCM150DY-12H with two parallelchips. The value of f depends onthe parasitic inductance of the gatedrive circuit and the switchingspeed of the hybrid driver. Theexact value of f is difficult todetermine. It is often desirable toestimate the minimum value of R Gthat can be used with a givenhybrid driver circuit and IGBTmodule by monitoring the peak

gate current while reducing R Guntil the rated I OP is reached. Theminimum restriction on R G oftenlimits the switching performanceand maximum usable operating fre-quency when large modulesoutside of the drivers optimumapplication range are beingdriven.Further steps to addressthis issue are provided inSection 5.10.

5.2 Power Supply RequirementsPower is usually supplied to hybridIGBT gate drivers from lowvoltage DC power supplies thatare isolated from the main DC busvoltage. Isolated power suppliesare required for high side gatedrivers because the emitterpotential of high side IGBTs isconstantly changing. Isolatedpower supplies are often desiredfor low side IGBT gate drivers in or-der to eliminate ground loop noiseproblems. The gate drive suppliesshould have an isolation voltagerating of at least two times theIGBTs V CES rating (i.e.VISO = 2400V for 1200V IGBT).In systems with several isolatedsupplies intersupply capacitancesmust be minimized in order toavoid coupling of common mode

noise. The recommended powersupply configuration for Mitsubishihybrid IGBT gate drivers is shownin Figure 5.2. Two supplies areused in order to provide the on-and off-bias for the IGBT. The rec-ommended on bias supply (V CC )voltage is +15V and the recom-mended off-bias supply voltage(VEE ) is -10V.

Normally these supplies should beregulated to 10% howeveroperation within the rangeindicated on the individual driver

data sheets is acceptable.Electrolytic or tantalum decouplingcapacitors should be connected atthe power supply input pins of thehybrid driver. These capacitorssupply the high pulse currentsrequired to drive the IGBT gate.The amount of capacitancerequired depends on the size of theIGBT module being driven. A 47 Fcapacitor is sufficient for most ap-plications.

5.2.1 Supply Current

The current that must be suppliedto the IGBT driver is the sum of twocomponents. One component isthe quiescent current required tobias the drivers internal circuits.The current is constant for fixedvalues of V CC and V EE . The sec-ond component is the current re-

47F

47F

+

+VEE

(10V)

+

+VCC

(15V)

ID

TO HYBRID DRIVER

ID

ICOM

Figure 5.2 Hybrid Driver PowerSupply

MITSUBISHI SEMICONDUCTORS POWER MODULES MOS

USING HYBRID GATE DRIVERS AND GATE DRIVE POWER SUPPLIES

8/7/2019 57962l

3/11

Sep 1998

quired to drive the IGBT gate. Thiscurrent is directly proportional tothe operating frequency and the to-tal gate charge (Q G) of the IGBTbeing driven. With small IGBTmodules and at low operating fre-quencies the quiescent current willbe the dominant component. Theamount of current that must besupplied to the hybrid driver whenVCC = 15V and V EE = -10V canbe determined from Equations 5.3and 5.4.

Equation 5.3Required supply current forM57957L and M57958L

ID = Q G x fPWM + 13mA

Equation 5.4Required supply current forM57959L and M57962L

ID = Q G x fPWM + 18mA

Where:ID = Required supply currentQG = Gate charge (See

Section 4.6.3)fPWM = Operating frequency

5.2.2 Single Supply Operation

The current drawn from V CC (ID+)is nearly equal to the current drawnfrom V EE (ID-). Only a smallamount of current flows in the com-mon connection (I COM ). In manyapplications it is desirable to oper-ate the hybrid driver from a singleisolated supply. An easy method ofaccomplishing this is to create thecommon potential using a resistorand a zener diode. In order to sizethe resistor for minimum loss wemust first determine the currentflowing in the common connection

(ICOM ). In M57957L and M57958La common connection current ofabout 2.5mA is required to bias in-ternal circuits. In M57959L andM57962L about 3.5mA flows fromthe detect pin through the IGBT tothe common connection. The cir-cuit in Figure 5.3 uses a zener sup-ply designed for about 5mA to sup-ply the common current. This cir-

cuit allows operation of Mitsubishihybrid drivers from a single isolated25 volt DC supply.

When the power supply circuitshown in Figure 5.3 is used withM57957L and M57958L therequired bias voltage at pin 5 of thehybrid driver appears after a delaycaused by the 2.7k resistor andthe 47 F capacitor. This delay maycause these drivers to generate anON output pulse during power up.In applications where the mainDC bus voltage is applied beforethe gate drive power supplies areon and stabilized the circuit in Fig-ure 5.4 should be used.

The voltage of the single supplyand the zener diode can be variedto allow use of standard supplies.For example, if a 24V DC-to-DC

Figure 5.3 Single SupplyOperation of HybridIGBT Drivers

converter is to be used then a 9Vzener diode would give +15/-9which is acceptable for all of thehybrid gate drivers. The twolimiting factors that need to beobserved if changes are made are:

(1) Voltages must be within the al-lowable range specified on thegate driver data sheet and

(2) The turn on supply should be15V+/-10% for proper IGBTperformance.

5.3 Total Power Dissipation

The hybrid IGBT driver has amaximum allowable powerdissipation that is a function of theambient temperature. WithVCC = 15V and V EE = -10V thepower dissipated in the driver canbe estimated using Equation 5.5.

Figure 5.4 Improved PowerSupply Circuit forM57957L andM57958L

47 F

47 F

+

+VD

(25V)+10V

2.7k

ID

TO HYBRID DRIVER

47F

VD(25V)

+

+

10V 10V

TO HYBRID DRIVER PIN 6

TO EMITTER OF IGBT

TO HYBRID DRIVER PIN 8

47F

+ 2.7k2.7kTO HYBRID DRIVER PIN 5



8/7/2019 57962l

4/11

Sep 1998

Equation 5.5Total power Dissipation

P D = ID x (VCC + VEE )

The power computed usingEquation 5.5 can then becompared to the derating curvesshown in Figures 5.5 through5.8 to determine the maximumallowable ambient temperature.The power computed usingEquation 5.5 includes thedissipation in the external gate

resistor (R G). This loss is outsidethe hybrid driver and can besubtracted from the result ofEquation 5.5. The dissipation inRG is difficult to estimate becauseit depends on drive circuit parasiticinductance, IGBT module typeand the hybrid drivers switchingspeed. In most applications theloss in R G can be ignored. Directuse of Equation 5 will result in aconservative design with the

included loss of R G acting as asafety margin. When operatinglarge modules at high frequenciesthe limitations on ambienttemperature may be significant.

5.4 Application Circuit forM57957L and M57958L

An internal schematic and exampleapplication circuit for the M57957Land M57958L are shown inFigures 5.9 and 5.10. Foroptimum performance parasiticinductance in the gate drive loopmust be minimized. This isaccomplished by connecting the47 F decoupling capacitors asclose as possible to the pins of thehybrid driver and by minimizing the

lead length between the drivecircuit and the IGBT. The zenersshown should be rated at about 18volts and be connected as close tothe IGBTs gate as possible. Thesezeners protect the gate duringswitching and short circuitoperation.

The gate driver has a built in185 ohm input resistor that isdesigned to provide proper drive

for the internal opto isolator whenVIN = 5V. If other input voltages aredesired an external resistor shouldbe added to maintain the properopto drive current of 16ma. Thevalue of the required external resis-tor can be computed by assumingthe forward voltage drop of theopto diode is 2V. For example:

If 15V drive is required then

Rext = (15V - 2V) 16ma - 185 = 630 .

5.5 Short-Circuit ProtectionUsing DesaturationTechniques

The M57959L and M57962L havebuilt in circuits that will protect theIGBT from short circuits bydetecting desaturation. When ashort circuit occurs a high currentwill flow in the IGBT causing its col-lector to emitter voltage to increaseto a level much higher than normal.The hybrid driver detects this con-dition and quickly turns the IGBT

off, saving it from certain destruc-tion.



8/7/2019 57962l

5/11

Sep 1998

0

1

2

5

ALLOWABLE POWER DISSIPATION (W)

0 100

3

4

AMBIENT TEMPERATURE (oC)

20 40 60 800

1

2

5


0 100

3

4

AMBIENT TEMPERATURE ( oC)

20 40 60 80

0

1

2

5


0 100

3

4


20 40 60 800

1

2

5


0 100

3

4


20 40 60 80

Figure 5.5 Derating Curve forM57957L




5.6 Operation of M57959Land M57962L

Figure 5.11 is a flow diagram show-ing the operation of the short pro-tection in M57959L and M57962L.The hybrid driver monitors the col-lector emitter voltage (V CE ) of theIGBT. Normally, when an on signalis applied to the input of the driverthe IGBT will turn on and V CE willquickly attain its low on-state valueof VCE (SAT). If a short circuit ispresent when the on signal is ap-

plied a large current will flow in theIGBT and V CE will remain high. Ashort circuit is detected by the hy-brid driver when V CE remainsgreater than the desaturation triplevel (V SC ) for longer than t TRIP af-ter the input on signal is applied.The t TRIP delay is used to avoidfalse tripping by allowing enoughtime for normal turn on of the IGBT.The hybrid driver initiates a con-trolled slow turn off and generates

a fault output signal when a shortcircuit is detected. The slow turn offhelps to control dangerous tran-sient voltages that can occur whenhigh short circuit currents are inter-rupted. The output of the driver willremain disabled and the fault signalwill remain active for t RESET after ashort circuit is detected. The inputsignal of the driver must be in its offstate in order for the fault signal tobe reset.



8/7/2019 57962l

6/11

Sep 1998

1

2

5

6

7

8

Figure 5.9 Internal Schematic Diagram of M57957L and M57958L

Figure 5.10 Application Circuit for M57957L and M57958L

8

5

6

7

1

2

VIN

RG

VCC

VEE47F

47F+

+

M57957L

M57958L

+

+

LOGICSIGNALINPUT

BUFFER

18V

Figure 5.11 Protection CircuitOperation

START

DELAYtTRIP

ISINPUT SIGNAL

ON?

IS VCEGREATER THAN

VSC

SLOW SHUTDOWNDISABLE OUTPUT

SET FAULT SIGNALWAIT t RESET

ISINPUT SIGNAL

OFF?

CLEAR FAULTSIGNAL

ENABLE OUTPUT

NO

NO

NO

NO

YES

YES

YES

YES

IS VCEGREATER THAN

VSC



8/7/2019 57962l

7/11

Sep 1998

5.7 Application Circuit forM57959L and M57962L

Figure 5.12 is a block diagram ofthe M57959L and M57962L driversshowing the logical implementationof the flow diagram in Figure 5.11.Figure 5.13 is an example applica-tion circuit for M57959L andM57962L. Parasitic inductance inthe drive circuit should be mini-mized using the techniques de-scribed for the M57957L andM57958L in Section 5.4. Pins

(3,7,9,10) are used for factory test-ing and should not be connected toany external circuit. The detect di-ode (D1) must be fast recovery(approximately 100ns) and shouldbe rated at a voltage equal to orhigher than the IGBT module beingdriven. The 20V zener DZ1 is rec-ommended in order to protect thehybrid ICs detect input from tran-sient voltages that can occur duringrecovery of the detect diode. This

zener can be eliminated if the de-tect diodes recovery remains fastand soft over its entire temperaturerange and pin 1 of the hybrid IC re-mains free of high voltage tran-sients and ringing.

The gate driver has a built in185 ohm input resistor that isdesigned to provide proper drivefor the internal opto isolator whenVIN = 5V. If other input voltages aredesired an external resistor shouldbe added to maintain the properopto drive current of 16mA. Thevalue of the required external resis-

tor can be computed by assumingthe forward voltage drop of theopto diode is 2V. For example:

If 15V drive is required then

Rext = (15V - 2V) 16ma - 185 = 630 .

5.8 Adjusting the DesaturationTrip Time (t TRIP )

The hybrid drivers built in t TRIPdelay will work for mostapplications. However when largemodules are being driven with nearmaximum gate resistance thedriver may incorrectly detect a

FAULTLATCH

DISABLE OUTPUT

AND

AND

ONESHOTtRESET

DELAYtTRIP

VCCVTRIP

VCC

COMPARE

GATE DRIVE

SHORTDETECTED

SLOWSHUTDOWN

DETECT

FAULT

GATE

INPUT

VEE

Q S Q S

R

ISOLATION

Figure 5.12 Block Diagram for M57959L

Figure 5.13 Block Diagram for M57959L

8

6

4

5

1

13

14

VIN

4.7 k

D1

RG

DZ1 30V

VCC

VEE47 F

47 F+

+

M57959L

M57962L

+

+

Sources for D1: EDI (Electronic Devices Inc.) P/N RF160AVMI (Voltage Multipliers Inc.) P/N 1N6528

Buffer

LOGICSIGNALINPUT

FAULTOUTPUT

18V



8/7/2019 57962l

8/11

Sep 1998

short circuit. The false trip occursbecause it takes longer thantTRIP for the module to reach itslow on-state voltage. In theseapplications the t TRIP delay canbe extended by connecting acapacitor from pin 2 to V CC .Figure 5.14 shows the typicalincrease in t TRIP as a function ofthe external capacitor value forM57959L and M57962L.

5.9 Operational Waveforms

Figure 5.15 is a typical waveformshowing the gate to emittervoltage during a slow shutdown forM57962L. Approximately 2.4msafter the detect input (pin 1)voltage exceeds V SC the gate toemitter voltage is slowly brought tozero in about 2ms. Figure 5.16shows the collector-emitter voltage(VCE ) and collector current (I C) foran IGBT module during a shortcircuit. This waveform shows the

effectiveness of the slow shutdownin controlling transient voltage.

5.10 Driving Large IGBTModules

In order to achieve efficient andreliable operation of high current,high voltage IGBT modules, agate driver with high pulsecurrent capability and low outputimpedance is required. Mitsubishihybrid gate drivers are designed toperform this function as standalone units in most applications.However, for optimum performancewith large modules, it may benecessary to add an output boosterstage to the hybrid gate driver.

When using the hybrid gate driversas stand alone units with IGBTmodules outside the range

specified in Table 5.1, three thingsmust be considered. First, themaximum peak output currentrating of the hybrid gate driverplaces a restriction on theminimum value of R G that can beused. For example, the minimumallowable R G for M57962L is about5 ohms (for additional informationrefer to Section 5.1). This value ishigher than the recommendedvalue for many large IGBTs. UsingRG larger than the data sheetvalue will cause an increase in

td(on) , td(off), tr and turn-onswitching losses. In high frequency(more than 5kHz) applicationsthese additional losses are usuallyunacceptable. Second, even if theadditional losses and slowerswitching times are acceptable, thedrivers allowable power dissipationmust be considered. At an ambienttemperature of 60 C, the M57962Lis permitted to dissipate amaximum of about 1.5 (for moreinformation refer to Section 5.3). Ifa CM600HA-24H is being used, thedriver will dissipate 1.5W at aswitching frequency of 14kHz. Inthis case, operation at a higher fre-quency than 14kHz will cause thedriver to overheat. Lastly, thedrivers slow shutdown becomesless effective when it is used withlarge devices. This occurs becausecurrent that flows to the gatethrough the relatively high reversetransfer capacitance (C res ) oflarge devices can not be absorbedby the driver. Its output impedanceis not low enough. The slowshutdown may become lessslow and a larger turn-off snubbercapacitor may be required. Thisthird limitation is perhaps the mostserious. In some cases, the hybriddriver may completely lose controlof the gate voltage and allow it to

Figure 5.14 AddingCapacitance toExtend t TRIP

Figure 5.15 V GE and V DETECTWaveform

Figure 5.16 Short-CircuitShutdownWaveform

0

1

2

5

DESATURATION TRIP TIME tTRIP

, (s)

0 15000

3

4

CAPACITANCE (pF)

5000

CONDITIONS:VCC = 15 V, VEE ,= -10 V, TC= 25 C

6

7

10000

M57959L

M57962L

0

CONDITIONS:VCC= 15 V, VEE = -10 V, TC= 25 CVGE : 5v/div, V DETECT : 5v/div, 1 s/div

VGE

VDETECT

0

VCE

IC

CONDITIONS:VBUS = 300V, T j= 25 CVCE : 50v/div, I C: 100A/ div, 0.5 s/div



8/7/2019 57962l

9/11

8/7/2019 57962l

10/11

Sep 1998

Table 5.2 Booster Stage Transistors

npn Transistor pnp Transistor Peak Current V CEO Manufacturer PackageMJD44H11 MJD45H11 15A 80V Motorola Surface MountD44VH10 D45VH10 20A 80V Motorola TO-220MJE15030 MJE15031 15A 150V Motorola TO-220MJE243 MJE253 8A 100V Motorola TO-2552SC4151 2SA1601 30A 40V Shindengen Isolated TO-220

Figure 5.19 Alternate Booster Stage Configuration

PIN 5 OF M57962L ORPIN 7 OF M57958L TO IGBT

GATE

RG



8/7/2019 57962l

11/11

57962l

Documents