1. IGBT Applications In HEV/EV

2. Renesas Technology & Solution Portfolio
The wealth of technology you see here is a direct result of the fact that Renesas Electronics Corporation was formed on April 1, 2010 as a joint venture between Renesas Technology and NEC Electronics — Renesas Technology having been launched seven years ago by Hitachi, Ltd. and Mitsubishi Electric Corporation. There are four major areas where Renesas offers distinct technology advantage.
--The Microcontrollers and Microprocessors are the back bone of the new company. Renesas is the undisputed leader in this area with 31% of W/W market share.
--We do have a rich portfolio of Analog and power devices. Renesas has the #1 market share in low voltage MOSFET solutions.
--We have a rich portfolio of ASIC solution with an advanced 90nm, 65nm, 40nm and 28nm processes. The key solutions are for the Smart Grid, Integrated Power Management and Networking
--ASSP: Industry leader for USB 2.0 and USB 3.0. Solutions for the cell phone market
-- Memory: #1 in the Networking Memory market

3. Analog and Power Automotive Products
30V V in Application Optimized Processes
mΩ Protected High-side Drivers
LED Backlight LCDs
Low voltage family optimized for Qgd x Rds(on)
Separate family optimized for pure Rds(on) performance
Low RTH packaging technology
Scalable solutions for exterior lighting, relays, solenoids…
Ultra-low key-off leakage current performance
Robust protection against short-circuit conditions
Products Addressing All Major Vehicle Systems
600V Discrete Devices
Class-leading turn-off loss
High-speed, short-circuit rated, and low Vce(on) optimized
200A, 300A & 400A bare die
Crash-sensing chipset for airbag applications
Powertrain output load drivers, direct gas injection…
Battery management ICs, MOSFET gate drivers
Micro-isolator IGBT drivers for high-voltage isolation
Multi-chip Package devices for switch input and load control
We have a rich portfolio of Analog and power devices. Renesas has the #1 market share in low voltage MOSFET solutions.

4. ‘Enabling The Smart Society’
Challenge: Improve efficiency of HEV/EV automobiles. 
Solution:
Lower inverter losses by replacing MOSFET’s with IGBT’s in high-current applications.
The goal of improving HEV/EV range requires that all usage of electrical power be as efficient as possible.
A great many HEV/EV applications require the conversion of electrical energy to mechanical motion – mostly by means of a PMSM (BLDC) motor.
Also voltage level conversion – battery chargers, regenerative braking (recovered “brake” energy is low voltage – must be stepped up to traction drive battery voltage)
Virtually all such conversions employ an inverter (DC to DC or DC to AC), which use switching transistors.
Lowering losses in the inverters will improve HEV/EV range.
At high currents, IGBT’s have lower losses than MOSFET’s.

5. 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.

6. Switching Applications In HEV/EV

7. Switching Applications In HEV/EV
Windshield Wipers
Fuel Pump
Windshield Washer
Battery Charger
A/C Compressor
Traction Motor
Inverter
Cooling Fan and Pump
Seat Adjust
Motor/
Generator
Mirror Adjust
Regenerative Braking Voltage Conversion
Power Steering
Transmission Oil Pump
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.
Many applications (seat adjusters, windshield washers, etc) are – and will remain – low power, low voltage. These applications will always use MOSFET’s.
Traction motor drives will always use IGBT’s (high voltage, high current).
Several applications in an HEV/EV are candidates for using IGBT’s. Mostly, these applications presently are belt-driven from a gasoline engine. When there is no engine (EV) or the engine is shut down (HEV), these applications require electric motors. If the application uses higher voltages (greater than 12V) or has very high currents, IGBT’s make sense.

8. IGBT Silicon Technology

9. IGBT Silicon Structure
Symbol
Model
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.
Left image - An IGBT is applied like an NPN bipolar transistor.
Center image – An IGBT functions like a PNP Darlington with a MOSFET as the input transistor.
Right image - Placing a positive voltage (charge) on the base “capacitor” attracts electrons into the “p” silicon under the oxide. This forms a channel, which pulls the base down to (more or less) the emitter (collector of the PNP transistor). This forward biases the PNP base-emitter junction (the PNP emitter is the IGBT collector). The PNP transistor saturates.
The beta of the PNP is low (only 10 – 20 – 30), so significant current flows through the MOSFET channel. The beta is low because the PNP “base” region is much thicker than for a normal PNP transistor.

10. IGBT Technology Advances – Field Stop
Drawing sizes reflect the relative wafer thickness of the technologies
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.
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.
PT technology. Built by means of growing an epitaxial layer on top of a p+ substrate. Expensive. The n+ buffer helps keep the drift region thinner, which lowers conduction losses. E field may not “punch through” to the p+ substrate. Device failure.
NPT technology. Simplified construction (no p+ substrate) is less expensive. Thicker, drift region has higher conduction losses. Injection layer is achieved using direct ion implantation.
Field stop technology. The addition of the n+ buffer region allows the drift region to be more narrow, reducing conduction losses. Hybrid of the PT and NPT technologies. Renesas is working on 60um and 40um wafers. A sheet of 20lb copy paper is 100um thick.

11. IGBT Technology Comparison

12. IGBT Technology Advances – Trench Gate
Planar Gate
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.
The voltage drop across the MOSFET channel adds directly to the VCESAT voltage. The Trench gate technology is easier to control (in manufacturing) and produces a channel with low RDSON . This lowers VCESAT. It also increases the gate capacitance, which has an impact on the drive circuit.

13. Understanding An IGBT Datasheet

14. IGBT Datasheet Parameters
Most of the parameters shown here are common and well understood.
The reverse collector-emitter breakdown voltage varies greatly according to the technology used and the doping.
Some specially designed IGBT’s claim to block equal voltages in both directions, but most will block only 15V to 30V.
As a result an anti-parallel diode will be required in almost all applications.
Most newer Renesas IGBT’s are packaged with a well matched high speed diode.
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.

15. IGBT Datasheet Parameters
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).
Need to mention the miller capacitance: The capacitances are not fixed, like with a ceramic chip capacitor. They are the capacitances of a semiconductor junction. The width of the junction is a function of voltage, therefore, the capacitance is a function of voltage. The Gate-Collector voltage changes greatly as the transistor switches. Therefore CGC changes significantly. This must be considered when designing the drive circuit. (Same for a MOSFET.)
This is seen in the plateau on the charge graph.

16. IGBT Datasheet Parameters
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
The key to this slide is that the voltage and current do not transition at the same time.
The energy specs are unusual, but very important. If the IGBT (or MOSFET) does not provide energy specs, switching losses can be estimated using tr and tf, multiplied by the DC link voltage and 50% of the peak phase current.
Eon = VDCLINK * (APEAK * 0.5) * (2 * tr).
Eoff = VDCLINK * (APEAK * 0.5) * (1.2 * tf)
EOFF =

17. IGBT Datasheet Parameters
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.
The tail current is the “ramp down” in IC to the right of the center line.
Can’t switch the complimentary IGBT on until the tail current has died out. Tail current is bleeding off the charge in the drift region.

18. IGBT Power Loss Calculations

19. 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).
EON is the integral of VCE x IC from the time IC rises to 5% of the on-state value until VCE falls to 5% of the off-state value.
EOFF is the integral of VCE x IC from the time VCE rises to 5% of the off-state value until IC has fallen to 0 (end of “tail current”).
If the IGBT (or MOSFET) does not provide energy specs, switching losses can be estimated using tr and tf, multiplied by the DC link voltage and 50% of the peak phase current.
Eon = VDCLINK * (APEAK * 0.5) * (2 * tr).
Eoff = VDCLINK * (APEAK * 0.5) * (1.2 * tf)

20. IGBT Conduction Loss
Motor Phase Current
High-Side / Low-Side 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.
The conduction loss in a half bridge is split between the low-side and high-side IGBT’s.
The conduction loss is a function of both the current being carried and the length of time that the switch is on.
Integral can be calculated.
Simpler to estimate:
The conduction loss in a half bridge (both transistors) at max load is roughly equal to VCESAT multiplied by 80% of the RMS phase current.
Conduction loss = VCESAT * ARMS * 0.8.

21. IGBT / MOSFET Comparison

22. IGBT vs MOSFET Comparisons
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.
The relatively high VCESAT (compared to the on-state voltage of a MOSFET) makes IGBT’s almost unusable in 12V systems. MOSFET’s will rule.
VCESAT for an IGBT has a component that is proportional to the log of IC.
The on-state voltage of a MOSFET is proportional to the IC.
Therefore, IGBT’s have lower losses at higher currents.
RDSON for a MOSFET increases with the rated blocking voltage. Therefore, for higher voltage, higher current applications, IGBT’s will rule.

23. IGBT vs MOSFET Comparisons
Critical IGBT Specs
Critical MOSFET Specs
RJH60F7DPQ
VCES = 600V, IC = 90A
= 1.75V
tr = 81ns, tf = 74ns
= 2.1V
trr = 90ns
RJK2061JPE
VDSS = 200V, ID = +/-40A
= Ohm
tr = 7ns, tf = 10ns
= 1.17V
trr = 155ns
These two transistors are in the Renesas inventory, and meet the temperature requirements for automotive applications. But they are not necessarily fully qualified for automotive use (PPAP etc.) They are shown strictly as an example.

24. 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 losses per half/bridge
MOSFET losses per half/bridge
IGBT Conduction Loss = 56.0W
IGBT Switching Loss
EON = 0.218mJ
EOFF = 0.120mJ
PSW = (EON + EOFF) * = 6.76W
Diode Conduction Loss = 16.8W
Diode Switching Loss = 2.42W
Total Power Loss = 81.98W
MOSFET Conduction Loss = 114.0W
MOSFET Switching Loss
EON = 0.019mJ
EOFF = 0.016mJ
PSW = (EON + EOFF) * = 0.70W
Diode Conduction Loss = 2.34W
Diode Switching Loss = 4.17W
Total Power Loss = W
Power loss calculations made for both transistors using the estimation formulas. It is assumed that the MOSFET half bridge is driven with complementary signals. This increases the calculated switching losses by 50%. (Two transistors switch per cycle, but the “complementary transistor switches when the flyback diode is already conducting, so the applied voltage is quite low.)
Since the complementary MOSFET’s are conducting during the “fkyback” period, the conduction loss estimation is increased to:
Conduction loss = RDSON * ARMS * ARMS * 0.95
And the flyback diode conduction loss is estimated as:
VF * ARMS * 0.05
The IGBT flyback diode conduction loss is estimated as:
VF * ARMS * 0.2

25. HEV/EV Applications

26. 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.
Many applications that require higher power (AC, power steering, cooling fan/pump) are belt driven in a conventional auto.
This is often impractical for an HEV, since the motor frequently is shut down even when the vehicle is in motion.
An EV has no engine.
Therefore these applications must be powered by electrical energy.

27. 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.
STEP 1
STEP 2
STEP 3
STEP 4
STEP 5
STEP 6 1 2 3 4 5 6
Many low power applications make use of many BLDC motors – seat adjusters, remote mirror adjusters.
Mostly, these applications use brushed DC motors – which are less reliable than BLDC motors.
There is some movement towards replacing the brushed DC motors with BLDC motors. This requires many PWM outputs from an MCU.
However, for trapezoidal commutation, IGBT’s do not require complementary PWM signals. The low-side switches can be controlled from ordinary GPIO pins.
If trapezoidal commutation and IGBT’s are used, an MCU can drive twice as many BLDC motors with the same number of PWM timer outputs.
Digital outputs low for switch on.
Analog trace – Phase A current.

28. Conclusion

29. 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.
The latest advances in IGBT technology have improved the performance of these transistors.
If the industry moves to a 48V bus to supply the higher power applications like AC, power steering and the cooling fan/pump, IGBT’s will start to make sense in HEV’s and EV’s. Of course IGBT’s will always be used for the traction drive inverters.

30. Questions?

31. ‘Enabling The Smart Society’
Challenge: Improve efficiency of HEV/EV automobiles. 
Solution:
Lower inverter losses by replacing MOSFET’s with IGBT’s in high-current applications.
Do you agree that this solution is viable? 
The goal of improving HEV/EV range requires that all usage of electrical power be as efficient as possible.
A great many HEV/EV applications require the conversion of electrical energy to mechanical motion – mostly by means of a PMSM (BLDC) motor.
Also voltage level conversion – battery chargers, regenerative braking (recovered “brake” energy is low voltage – must be stepped up to traction drive battery voltage)
Virtually all such conversions employ an inverter (DC to DC or DC to AC), which use switching transistors.
Lowering losses in the inverters will improve HEV/EV range.
At high currents and higher voltages, IGBT’s have lower losses than MOSFET’s.