IGBT Applications In HEV/EV - Renesas e-Learning · IGBT’s, especially the A/C compressor and power steering. Particularly for EV’s, the trend is to run these applications directly

Renesas Electronics America Inc.© 2012 Renesas Electronics America Inc. All rights reserved.

IGBT Applications In HEV/EV

© 2012 Renesas Electronics America Inc. All rights reserved.2

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Challenge: Improve efficiency of HEV/EV automobiles.

Solution:Lower inverter losses by replacing MOSFET’s with IGBT’s in high-current applications.

‘Enabling The Smart Society’


Agenda

The purposes of this presentation are: To discuss IGBT technology in general. To discuss the advances that have improved IGBT performance

and lowered costs. To discuss the definition and application of various IGBT

datasheet parameters. To discuss power losses in IGBT switching transistors. To discuss the use of IGBT transistors in HEV/EV applications.

This presentation will focus on applying IGBT transistors in 3-phase inverters for PMSM motor applications.

While the basic principles discussed in this presentation are applicable to IGBT’s used in traction motor inverters, this presentation will focus on lower power applications, which predominantly use MOSFET’s at present.


Switching Applications In HEV/EV


Switching Applications In HEV/EV

There are many applications in an HEV/EV that require switching transistors: Inverter drives for PMSM motors. Switchmode DC-DC converters and battery chargers. Control of brushed DC motors.

The move to a 48V on-board supply and technological advances in IGBT design are making IGBT’s increasingly attractive in many of these applications.

Battery ChargerA/C

Compressor

Power Steering

Cooling Fan and Pump

Fuel Pump

Traction MotorInverter

Motor/Generator

Transmission Oil Pump

Mirror AdjustSeat Adjust

Windshield Wipers

Windshield Washer

Regenerative Braking Voltage Conversion


IGBT Silicon Technology


IGBT Silicon Structure

Essentially, an IGBT is a PNP Darlington transistor in which the bipolar input transistor has been replaced with a MOSFET. An IGBT is applied like an NPN power transistor. Does not conduct in the reverse direction (a MOSFET does). Does not provide an inherent reverse diode (a MOSFET does). Conducting voltage drop is like a diode – a fixed voltage plus a voltage

that is proportional to the log of the current.– The conducting voltage drop for a MOSFET is like a resistor – a voltage that is

proportional to the current. Contains a parasitic thyristor structure that can latch “on”.

– Better control of geometries and doping levels has virtually eliminated this potential problem.

– Still need to prevent narrow gate pulses to insure full switching transitions.

Symbol

ModelStructure


IGBT Technology Advances – Field Stop

PT Technology Punch Through

E-field “punches through” drift region to buffer –shortens tail current.

Thin drift region lowers VCE(SAT).

Expensive epitaxial layer grown on p+ substrate.

NPT Technology Non-Punch Through

E-field dissipates in drift region – lengthens tail current, raises EOFF.

Thick drift region raises VCE(SAT).

Injection layer realized by ion implantation, no epitaxial layer.

FS Technology Field Stop

E-field “punches through” drift region to buffer –shortens tail current.

Thinnest drift region yields lowest VCE(SAT).

No epitaxial layer. Wafers as thin as 80µm.

Drawing sizes reflect the relative wafer thickness of the technologies


IGBT Technology Comparison


IGBT Technology Advances – Trench Gate

The IGBT saturation voltage, VCE(SAT), is a key figure of merit. One factor contributing to the IGBT saturation voltage is the MOSFET

channel voltage.– The channel voltage is directly proportional to the channel length and

inversely proportional to the channel width. By burying the gate structure in a vertical trench, the channel geometry

can be optimized to reduce the IGBT saturation voltage by as much as 0.2V – down as low as 1.35V (typ).

This increases the Gate-Emitter capacitance, CGE, by as much as a factor of 3, which in turn increases requirements on the gate drive circuit.

Planar Gate Trench Gate


Understanding An IGBT Datasheet


IGBT Datasheet Parameters

The basic voltage and current parameters hold no real surprises. The reverse collector-emitter breakdown voltage often is left off of IGBT datasheets. 15V to 30Vis typical. Thermal considerations will limit the max current to something well below the

current the ratings stated in a datasheet. VCE(SAT) is high for an NPN power transistor and low for a PNP power Darlington.



Cies = CGC + CGE with C-E shorted. Coes = CGC + CCE with G-E shorted. Cres = CGC with E grounded. Also

known as the Miller capacitance.

Qg = Total gate charge transferred during a switching transition.

Qge = Charge transferred before the gate plateau voltage is reached (CGE).

Qgc = Charge transferred as VCE

changes during switching (CGC).



tDON = turn-on delay = t3 – t1 tR = rise time = t4 – t3 tON = switch-on time = t7 – t1 tDOFF = turn-off delay = t9 – t8 tF = fall time = t10 – t9 tOFF = turn-off time = t11 – t8

EON =

ETOTAL = EON + EOFF

EOFF =



The tail current is the final decay of IC, shown to the right of the center line in this graph.

The tail current decay time is a principle component of the switching “deadtime”.

The tail current decay time adds to the effective IGBT turn-off time and increases EOFF.


IGBT Power Loss Calculations


IGBT Switching Loss

Switching Loss During each switching event, there are transition periods when

both IC and VCE are significantly non-zero. EON is the energy (in Joules) that is dissipated in the IGBT

during the turn-on transition. EOFF is the energy (in Joules) that is dissipated in the IGBT

during the turn-off transition. ETOTAL is the total energy (in Joules) that is dissipated in the

IGBT during one complete switching cycle (EON plus EOFF). The total switching loss (in Watts) is ETOTAL multiplied by the

number of switching cycles per second (PWM base frequency).


IGBT Conduction Loss

On-state current flow through an IGBT switch is a function of the PWM duty cycle and the commutation angle of the motor drive current.

The IGBT conduction loss (in Watts) is the integral of VCE(SAT) x IC

over one commutation cycle (in Joules), multiplied by the number of commutation cycles per second.

The total IGBT power loss is the sum of the switching loss and the conduction loss.

Motor Phase Current High-Side / Low-Side IGBT Conduction Loss


IGBT / MOSFET Comparison


IGBT vs MOSFET Comparisons

IGBT Applied at higher voltages

where VCESAT is less significant. Lower conduction losses at

higher currents. Higher switching losses favor

low frequency switching applications.

MOSFET Applied at lower voltages

where RDSON is very low. Lower conduction losses at

lower currents. Lower switching losses favor

high frequency switching applications.

Rule of Thumb: If the supply voltage is less than 30V, the output power is less than

250W or the switching frequency is greater than 20kHz, use a MOSFET. If the supply voltage is greater than 200V or the output power is

greater than 1kW, and the switching frequency is 20kHz or less, use an IGBT.

The lower switching losses and lower VCE(SAT) of modern IGBT’s will allow IGBT’s to displace MOSFET’s in many HEV/EV applications, especially if the 48V on-board supply is adopted.


IGBT vs MOSFET Comparisons

RJH60F7DPQ VCES = 600V, IC = 90A VCESAT @50A = 1.75V tr = 81ns, tf = 74ns VFD @20A = 2.1V trr = 90ns

RJK2061JPE VDSS = 200V, ID = +/-40A RDSON @20A = 0.075 Ohm tr = 7ns, tf = 10ns VFD @40A = 1.17V trr = 155ns

Critical IGBT Specs Critical MOSFET Specs


IGBT vs MOSFET Comparisons Description of system used for calculations

48V on-board supply. Air-conditioning compressor powered by a

2.17HP, 3-phase PMSM motor. Max cooling: 5530 BTU/hr = 0.46 ton. Max motor phase current: 56APEAK / 40ARMS. 20kHz sinusoidal PWM.

IGBT Conduction Loss = 56.0W IGBT Switching Loss

EON = 0.218mJ EOFF = 0.120mJ PSW = (EON + EOFF) * 20000 = 6.76W

Diode Conduction Loss = 16.8W Diode Switching Loss = 2.42W Total Power Loss = 81.98W

IGBT losses per half/bridge MOSFET losses per half/bridge

MOSFET Conduction Loss = 114.0W MOSFET Switching Loss

EON = 0.019mJ EOFF = 0.016mJ PSW = (EON + EOFF) * 20000 = 0.70W

Diode Conduction Loss = 2.34W Diode Switching Loss = 4.17W Total Power Loss = 121.21W


HEV/EV Applications


HEV/EV Applications

In an HEV/EV, many functions that run directly from engine power in a conventional auto must now run from battery power. Transmission oil pump (hydraulic pressure for the actuators). A/C compressor. Cooling fan (still needed for the A/C condenser coil, battery

cooling and traction drive inverter cooling). Coolant pump. Power steering.

These are higher power applications that might better use IGBT’s, especially the A/C compressor and power steering.

Particularly for EV’s, the trend is to run these applications directly from the traction drive battery. This is more efficient and the higher voltage favors the use of IGBT’s.

Traction drive inverters will always use IGBT’s. Low power body applications generally will use MOSFET’s.


HEV/EV Applications Many HEV/EV body applications are switching to PMSM motors for

improved reliability (no brushes). Such applications often can use 6-step trapezoidal commutation, in which

one phase is driven (PWM), one phase is always grounded and one phase is always open.

For IGBT switches, it truly is necessary to generate PWM signals only for the high-side switch. The low-side switch should remain off during PWM.

1 2 3 4 5 6STEP 1 STEP 2 STEP 3

STEP 4 STEP 5 STEP 6

• Digital outputs low for switch on.• Analog trace – Phase A current.


Conclusion


Conclusion

The Trench Gate and Field Stop technologies used in the newer IGBT transistors are allowing IGBT’s to displace MOSFET’s in many HEV/EV applications.

The move to a 48V on-board supply makes IGBT’s much more attractive.

When performing the system design on a new HEV/EV application, it makes sense to perform power loss calculations for both types of transistor.

In an increasing percentage of applications, it will be found that IGBT’s offer a more efficient, lower cost solution.


Questions?


Challenge: Improve efficiency of HEV/EV automobiles.

Solution:Lower inverter losses by replacing MOSFET’s with IGBT’s in high-current applications.

‘Enabling The Smart Society’

Do you agree that this solution is viable?

Renesas Electronics America Inc.© 2012 Renesas Electronics America Inc. All rights reserved.

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IGBT Applications In HEV/EV - Renesas e-Learning · IGBT’s, especially the A/C compressor and power steering. Particularly for EV’s, the trend is to run these applications directly