Achieving High Efficiency andEnabling Integration in EV
Powertrain Subsystems Using
C2000™ Real-Time MCUs

Manish Bhardwaj,
Systems Engineer
C2000™ Microcontrollers
Waqar Mehmood,
Product Marketing
C2000™ Microcontrollers

There are a variety of architectures and topologies used inelectric vehicle powertrain subsystems like onboard chargers(OBCs) and high-voltage to low-voltage DC/ DC converters.
Efficient control and management of the power flow inthese systems can be achieved using one or more real-time
microcontrollers (MCUs).
The electric vehicle (EV) market has been growing rapidly

At a glancesince 2010, with original equipment manufacturers

This paper discusses common control challenges ofevolution toward more pure EVs rather than hybrids

onboard chargers and high-voltage to low-voltage

is a reaction to government environmental policies

DC/DC converters, and the benefits of C2000™ real-time

mandating a transition away from internal combustion

MCUs in these subsystems.

engines.

(OEMs) announcing EV models through 2025. This

Higher-capacity battery packs, while reducing consumer

123

Totem-pole PFC and CLLLC topology
for onboard chargers

anxiety related to limited driving ranges, place increasing

A totem-pole bridgeless PFC improves efficiency
by lowering the number of power devices in
the current path, while enabling bidirectional
operation. The CLLLC isolated DC/DC converter
provides a soft-switching capability to enablea higher switching frequency and smaller
magnetics size.

the onboard charger (OBC), which not only needs toPeak current mode control forhigh-voltage to low-voltage DC/DC
converters

carbide (SiC) wide-bandgap power semiconductors has

The analog integration on a C2000 real-time
microcontroller enables peak current mode with
control loops fully in hardware.

ability to operate efficiently at much higher switching

demands on an EV’s power electronics – specificallyaccommodate higher power ratings to accommodate
higher power capacities, but must also possess higher
power density and higher efficiency to reduce weight ofthe vehicle and reduce cost per charge.
The emergence of gallium nitride (GaN) and siliconprovided an opportunity to massively shrink the size
and weight of the power electronics in EVs given theirfrequencies than silicon.
The challenge for OEMs and Tier-1s is to provide OBC

Scalable portfolio of real-time MCUs
for onboard chargers

solutions that can support multiple geographic regionswith different power-grid infrastructures. For example,

C2000 real-time MCUs offer a scalable portfolio
to address the variety of integration needs anddiscrete options in on-board charger systems.

higher power EV chargers in China need to support
connections to a three-phase power line, while EVs inthe U.S. need to connect to a single-phase power line.
OEMs want to supply variants with power ratings ranging

Achieving High Efficiency and Enabling Integration in EV Powertrain Subsystems
Using C2000™ Real-Time MCUs

2December 2020

from 3.3 kW to 22 kW typically – and as high as 44 kW in• Reduce losses by enabling soft-switching schemes

some cases.

that don’t compromise efficiency, such as critical

The most critical systems in an EV powertrain are themode operation and valley switching.
• Reduce cost by increasing analog integration toOBC that is used to charge the high-voltage battery,the high-voltage to low-voltage DC/DC converter which

reduce the number of external components in thecharges the 12-V/48-V battery, and the traction inverter

design, such as comparators and digital-to-analog

that controls the EV motor, shown in Figure 1.

converters (DACs).
The MCU should also be part of a scalable portfolio tosupport the variety of options when integrating OBCs
with the high-voltage to low-voltage DC/DC converter. In
this white paper, we will review the typical topologies
and challenges for each stage and highlight some of
the features of C2000 real-time MCUs to help you solve
those challenges.

Totem-pole PFC and CLLLC topology foronboard chargers
Figure 1. EV Powertrain System Block Diagram.

Figure 2 shows a 3.3-kW OBC with a totem-pole

Efficient control and management of the power flow

PFC stage for the OBC PFC and a capacitor-inductor-

in these systems can be achieved using one or more

inductor-inductor-capacitor (CLLLC) stage for the OBC

real-time microcontrollers (MCUs). To save mechanical

DC/DC converter. A totem-pole bridgeless PFC improves

costs and reduce the size of power electronics, one

efficiency by lowering the number of power devices in

popular trend is to integrate OBC equipment with thethe current path, while enabling bidirectional operation

high-voltage to low-voltage DC/DC converter, which can(compared to a conventional bridge-based PFC).

save as much as 10%-20% of board space. However,

Implementations of totem-pole bridgeless PFC were

this adds additional requirements for the real-time MCU,

previously limited to lower power levels only because

as it need to support more pulse-width modulators

the inherent body diode in silicon power metal-oxide(PWMs), more ADCs and allow for multicore processing

semiconductor field-effect transistors was susceptible

to manage multiple power stages.

to high reverse-recovery losses under hard switching.
With no such body diode within its structure, GaN

Further, OBCs need to support bidirectional operation

power switches such as the LMG3410R050 from Texas

for vehicle-to-grid, which result in more complex

Instruments have now made it practically feasible

topology choices that necessitate even greater care

to implement multikilowatt totem-pole bridgeless PFC

when selecting an MCU for an OBC. The MCU must

power supplies. Since GaN devices feature low output

include features that:capacitance (Coss), they can be operated at high• Reduce magnetic size and weight by enabling highfrequencies (100 to 200 kHz), which further allows using

frequency operation through high resolution control

smaller inductor and thus shrinks the size of the passiveof power converters duty cycle, frequency, deadband

components required in the totem-pole PFC converter.

and phase-shift.

During dead time, however, third-quadrant operation in
GaN switches results in additional losses that a real-time
MCU needs to optimize by regulating the dead timeAchieving High Efficiency and Enabling Integration in EV Powertrain Subsystems
Using C2000™ Real-Time MCUs

3December 2020

precisely. C2000 real-time MCU type 4 PWMs enable

the switching frequency to 1MHz and employing control

features such as high-resolution dead time, which cantechniques such as Critical Mode PFC, the power loss

regulate the deadband to 150 ps of resolution. Assavings can be as high as 10W, thus making optimization

an example, for a 100-kHz totem-pole PFC, the lossof third quadrant losses a critical feature, for whichsavings with dead-time optimization is 1 W. As theprecise and accurate control of the dead time if required.

designers reduce the inductor size further by increasing

Figure 2. OBC Power Stage with Single-phase PFC and Isolated DC/DC Stage.

Peak current mode control for high-voltage to
low-voltage DC/DC converters

and often requires external circuitry. The integrated

Looking at the OBC DC/DC stage, an isolated DC/DC

implementation of synchronous rectification without

converter such as CLLLC is a popular choice as it

external components such as DACs, comparators or

has an extended zero voltage switching (ZVS) range

logic gates. Furthermore, the Type-4 PWM allows

that provides soft-switching capability to enable higher

additional blanking windows during PWM periods andswitching frequency which enables smaller magnetic

can latch the current crossing events to add robustness

size. Further, a synchronous rectification scheme (Figureto the synchronous rectification scheme, thus adding3) can enable efficiency improvements of as muchnoise resiliency to the implementation.

comparator subsystems on C2000 MCUs enable theas 2%, but this scheme is challenging to implement

Figure 3. Active Synchronous Rectification Scheme with On-chip Resources for High-frequency Converters.

Achieving High Efficiency and Enabling Integration in EV Powertrain Subsystems
Using C2000™ Real-Time MCUs

4December 2020

Looking at the high-voltage to low-voltage DC/DCcontrol is that it can lead to system instability, as shown

converter, phase-shifted full bridge (PSFB) is a typicalin Figure 4. Slope compensation is added to the peak

topology used. Peak current-mode control eliminates

current reference point, to avoid this instability and is

the need for an expensive DC blocking capacitor. The

typically implemented in analog.

primary challenge in implementing peak current-mode

Figure 4. Peak Current-mode Control Implementation with Slope Compensation.

The advanced analog integration in the C2000 real-precharge resistors and further reduce components intime MCU comparator subsystem enables achieving thisthe powertrain.

advanced control with a digital controller. Additionally,Scalable portfolio of real-time MCUs for
onboard chargers

Type-4 PWM features such as inserting deadband whena peak current event occurs allows the digital controller
to generate complimentary PWM. This allows the change

OBCs range from 3.3 kW for plug-in hybrid EVs to 6.6 toof deadband under different line and load conditions

22 kW for EVs. Popular architectures for 3.3- to 6.6-kW

to maintain soft switching. Digital control also enables

OBCs include totem-pole PFC and CLLLC. Table 1 lists

additional functions such as precharging the traction

the different real-time MCU choices available based on

inverter bus using the high voltage to low voltage DC/DC

the system architecture, as well as integration options.

converter, which can eliminate the need for external
Minimun resource requirementsPWMs

Typical real-time MCU option

ADCsMIPS

Separate controller

Single controller forOBC, separate for
HV/LV DC/DC

3.3kW/6.6kW OBC PFC 2stage (totem-pole PFC)

570

F280025

F280049

3.3kW/6.6kW OBC
DC/DC converter(CLLLC)

8550

F280025

F280025

3kW High-voltage tolow-voltage DC/DCconverter

6540

F20025Single integratedcontroller
F2837S

Table 1. Real-time MCUs for 3.3- to 6.6-kW OBCs and High-voltage to Low-voltage DC/DC Systems.

Achieving High Efficiency and Enabling Integration in EV Powertrain Subsystems
Using C2000™ Real-Time MCUs

5December 2020

For 11kW and higher OBCs, one approach is to stackphase is more readily available, so a modular approach isthree 3.6-kW chargers (which are topology-wise similar

popular. In Europe or Asia, where three phase is moreto 3.3-kW chargers); this is referred to as the modular

readily available, a three-phase PFC can offer higher

OBC approach. It’s also possible to design additional 22-

density and lower costs, since the system requires fewer

kW chargers by stacking 11-kW chargers or increasing

power devices and switches. To address this wide range

the power rating by paralleling or by selecting differentof power levels, look for a scalable controller portfolio

field-effect transistors (FETs). Another approach to 11kW

that can not only handle advanced topology control but

uses a three-phase PFC front end with some derating foralso enable integration. The C2000 MCU portfolio (Table

single-phase operation.

3), ranging from low to mid to high end devices, enables
the system implementation options in Table 1 and Table

The approach selected by the OEM can vary based2.

on geographic region. For example, in the U.S., single

Minimun resource
requirements
PWMs

ADCs

Typical real-time MCU option
MIPS

Separate controller Single integrated controller

11kW modular OBC (PFC plus DC/DC converter)

1010120Three F280049s

F28388D

3kW high-voltage to low-voltage DC/DC converter

6540

F280025

F28388D

11kW OBC PFC stage (T-Type)

12850

F280025

11kW OBC DC/DC stage (two DC-DC converters, 5.5kW each)

168100F280049

Table 2. Real-time MCUs for 11-kW and Higher OBC and High-voltage to Low-voltage DC/DC Converter Systems.
DevicePWM

ADCMIPS

F2800251416100F280049

1421200

F28377D

2424800

F28388D

3224925

Table 3. C2000 Real-time MCU Portfolio.

In the modular approach (which stacks three single-allows for the design of a single controller for eachphase chargers to reach 11 kW), each module isphase, with a separate controller (using the F280049) ordesigned for 3.6 kW, works with a single-phase ACa single controller (such as the F28388) controlling all

input, and typically has a single-phase PFC stage andthree stages of the OBC. The F280025 can also control

a DC/DC stage (Figure 5). The high-voltage and low-

the high-voltage to low-voltage DC/DC converter, as it

voltage DC/DC converter connects to the high-voltage

provides the necessary advanced analog integration tobattery on one end and the 12-V battery on the other.

control the phase-shifted full-bridge power stage.

The existence of multiple isolation planes in the system

Achieving High Efficiency and Enabling Integration in EV Powertrain Subsystems
Using C2000™ Real-Time MCUs

6December 2020

Figure 5. 11-kW OBC with 3.6-kW Stacked Chargers and a High-voltage to Low-voltage DC/DC Converter.

If the power stage is not modular, you can control thesuch as “one-box” are gaining momentum, where theentire system using a single controller. Figure 6 shows

OBC and high-voltage to low-voltage DC/DC converter

one such example, using a T-type three-phase PFC andare housed in the same enclosure. The one-box

an interleaved dual active bridge (DAB) converter forconcept opens up additional options by using multiport

the OBC. (Table 2 listed several MCU choices for thisconverters that share the DC/ DC stage between thesystem.) The F28388D device from the C2000 real-time

OBC DC/DC stage and high-voltage to low-voltage

MCU family can control all of the power electronics inDC/DC converter.

the system. As OEMs optimize these systems, concepts

Figure 6. 11-kW OBC plus a High-voltage to Low-voltage DC/DC Converter Controlled Using the F28388D.

Figure 7. An 11-kW OBC plus High-voltage to Low-voltage DC/DC Converter Using a Multiport Scheme Controlled by the F28388D.

Achieving High Efficiency and Enabling Integration in EV Powertrain Subsystems
Using C2000™ Real-Time MCUs

7December 2020

Now that a single controller is controlling all of the• Sun, Bingyao. 2019. “Does GaN Have a Body Diode?

stages, further optimizations become possible. Figure 7– Understanding the Third Quadrant Operation ofshows the use of a multiport converter, which reduces

GaN.” Texas Instruments application report, literature

the number of switches/high-voltage FETs required byNo. SNOAA36, February 2019.

16%.

Conclusion• Texas Instruments. n.d. “Bidirectional CLLLC
Resonant Dual Active Bridge (DAB) Reference
Design for HEV/EV Onboard Charger.” Texas

As OEMs and Tier-1s push the limits of efficiency andInstruments reference design No. TIDM-02002.

power density, the need arises for real-time controllers

Accessed Oct. 26, 2020.

that are scalable and can enable advanced topologies• Texas Instruments. n.d. “Highly Efficient, 1.6-

and integration options. The device capabilities built into

kW High-Density GaN-Based 1-MHz CrM Totem-

C2000 MCUs enable system designers to achieve higher

Pole PFC Converter Reference Design.” Texas

switching frequencies while maintaining high efficiency,Instruments reference design No. TIDA-00961.

thus reducing system size and cost. The C2000 real-Accessed Oct. 26, 2020.

time MCU portfolio includes modular to fully integratedsolutions, along with reference designs and software foradvanced topologies such as CLLLC, DAB, totem-pole
PFC, Vienna rectifier, T-Type PFC and phase-shifted fullbridge (PSFB).
These tools and resources can accelerate the design and• Texas Instruments. n.d. “Peak Current ModeControlled Phase-Shifted Full-Bridge Reference
Design Using C2000 Real-Time MCU.” Texas
Instruments reference design No. TIDM-02000.
Accessed Oct. 26, 2020.
• Texas Instruments. n.d. “Three-Level, Three-Phasedevelopment of power converters for EV applications

SiC AC-to-DC Converter Reference Design.” Texas

such as OBC and high-voltage to low-voltage DC/DC

Instruments reference design No. TIDA-010039.

converters.

Accessed Oct. 26, 2020.

Additional resources• Texas Instruments. n.d. “Bidirectional, Dual Active
Bridge Reference Design for Level 3 Electric Vehicle• C2000 real-time MCUs

Charging Stations.” Texas Instruments reference• GaN power devices

design No. TIDA-010054. Accessed Oct. 26, 2020.

References• “Bidirectional Interleaved CCM Totem Pole• Texas Instruments. n.d. DigitalPower Software
Development Kit (SDK) for C2000 MCUs. Accessed
Oct. 26, 2020.

Bridgeless PFC Reference Design Using C2000™
MCU.” TIDM-1007/02008 User Guide.” Texas
Instruments user guide, literature No. TIDUD61D,
March 2020, revised October 2020.

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