here. - Auto Electronics Magazine

C O V E R S T O R Y
HYBRID VEHICLES
PROPEL
INCREASED ELECTRONICS CONTENT
12 WARD’S AUTO ELECTRONICS | OCTOBER 2004
by Randy Frank, Contributing Editor
Hybrid vehicles are expected to more than double the use of electronic
components in automobiles. This report investigates the impact of hybrid
vehicles on the powertrain as it probes architectural developments.
It also shows how it is driving the design of power components like inverters,
dc-dc converters, battery chargers, cooling systems, electric power steering
and electric A/C, along with electric clutch disengage
and regen braking, as well as other in hybrid designs.
Ahybrid powertrain that combines an internal combustion or
diesel engine with electric propulsion adds several design options
to vehicle manufacturers and several costly components to the
vehicle. From some estimates, the electrical/electronic content in the
vehicle will almost double if the vehicle is a hybrid, especially in the near
term with low volumes. The key added components of the hybrid include
an electric motor, inverter, dc-dc converter, control electronics and highvoltage
batteries. Ford has indicated that the price of the 2005 Escape
Hybrid will be $3,300 more than a comparably equipped V-6 (only)
powered Escape [1]. GM’s Silverado 42 V mild hybrids cost $1500 more [1].
FROM FUEL ECONOMY ONLY TO PERFORMANCE
Expected sales of existing U.S. hybrid vehicles in 2004 are
approximately 36,000 Honda Civics and 47,000 Toyota Prius with the
Honda Insight dropping to a mere 1,000 or so units. The addition of Ford’s
Hybrid Escape with forecast annual sales of 20,000 units (4,000 units in
2004), GM’s Silverado and Sierra models (scheduled for 2,500 units in
MY2005) and Daimler Chrysler’s diesel electric Ram pickup scheduled for
100 units will raise hybrid numbers slightly [1]. However, with sales of 16
million total cars and light trucks expected in 2004, this means hybrids are
quite a bit less than 1% of the market—but it’s a start.
Powertrain
Control
Electronic
Transmission
Future/Emerging
Loads
Electromagnetic Valves
Integrated Starter/Alternator
Electrical A/C Compressor
Electromechanical Brakes
Active Suspension
Electric Turbocharger
Power Running Boards

Power Windows, Door Locks,
Seats, Antenna
Heated Backlight
Body Electronic Systems
(Climate Control, Keyless Entry,
Digital Instrument Panel)
Electronic Power Steering
Air Bag System
Lighting
Systems
ABS Brake
System
Advanced Entertainment
Systems
OCTOBER 2004 | WARD’S AUTO ELECTRONICS
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13

C O V E R S T O R Y
In spite of record high fuel
prices in 2004, the additional
upfront cost of the fuel-efficient
hybrid would still mean a
payback period of two to three
years to offset the higher
purchase price. In contrast,
customers appear to be more
than willing to pay an additional
$895 for a Dodge Durango with
a 345 hp, 5.7-liter hemi engine
over the 230 hp,
4.7-liter engine. To further
raise the cost impact of their
purchase, drivers often trade
in a perfectly good low-mileage,
one-year-old vehicle to get the
additional performance, costing
them an additional $7000 to
$8000 in depreciation [2].
Hybrids have the potential
to provide fuel economy,
performance and reduce
emissions. Automotive power
train designers have options
depending on the type of vehicle
they want to produce. For highest
Vehicle Engine (hp) Motor (hp) Total (hp)
Curb Weight
(Lbs)
Power to Weight
(x100)
Honda Insight 55 10 65 1964 3.3
Toyota Prius 2002 70 25 95 2765 3.4
Honda Civic Hybrid 85 13 98 2732 3.6
Toyota Prius 2004 82 28 110 2890 3.8
Ford F-150 2004, 4.6L V-8, reg bed 231 — 231 4788 4.8
EPA Data for Average P/W
Extrapolated to 2004
4.9
Toyota Camry 4-cyl 2004 auto trans 157 — 157 3142 5.0
Chevy Silverado 2004, Vortec 4.8L
V-8
285 — 285 4555 6.3
Honda Accord, STD 2004 6 cyl 240 — 240 3265 7.4
Honda Accord Hybrid* 240 13 253 3415 7.4
Honda Accord, STD 2004 4 cyl 231 — 231 3109 7.4
*Assuming only 13 hp added by electric motor and additional weight of 150 pounds.
Table 1. Power-to-weight ratio for hybrid vehicles and most popular cars and trucks [3].
14 WARD’S AUTO ELECTRONICS | OCTOBER 2004
Figure 1. The power-to-weight trend for combined light car and truck sales in the
United States [4].
fuel economy, the engine and electric motor are operated at optimal
points to achieve high efficiency. The internal combustion engine (ICE)
has average efficiencies of 15% but can achieve 30% when operating
in the sweet spot. For performance, different points in the torque and
horsepower curves between the motor and engine are exploited. This
can provide more low-end torque with increased fuel economy.
The Accord hybrid that will go into production in 2005 provides an
example of the change in hybrid design. It uses the Integrated Motor
Assist (IMA) hybrid system concept from the Insight and Civic but will
provide V-6 performance with 4-cylinder economy. Honda did not
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C O V E R S T O R Y
reduce the engine size when it
added the electric motor to the
drive train. A summary of vehicles
and their performance increase
using electric motors is shown in
Table 1. Using historical values,
the Honda Insight’s 0.033 and
Toyota’s 2002 Prius at 0.034 hplb
are more like the performance of
vehicles sold in the early 1980s,
limiting the number of people
who would be interested in
purchasing such vehicles for lack
of performance. For comparison,
a 2004 Camry 6 cylinder is 0.062
and Ford F-150 5.4L V-8 is 0.061
hp/lb. When vehicles exceed
0.047 hp/lb they appeal to more
than 50% of the buyers, and those
buyers are frequently willing to pay
more money for performance, as
indicated in Figure 1 [3].
(a) (b)
Figure 2. Honda Insight mild hybrid (a) compared to the Toyota Prius full hybrid (b).
POWER ELECTRONICS IN HYBRIDS
Two common classifications for today’s hybrid are: (1) mild
and (2) full hybrid. The 166 V Honda Insight in Figure 2 (a) is a mild
hybrid because it always uses the gas engine to drive the wheels
and the electric motor provides an extra boost during acceleration.
In contrast, the Toyota Prius in Figure 2 (b) is a full hybrid with

Figure 3. Powering Ford’s Hybrid Escape Split Hybrid system and traditional 14 V loads.
the ability to use the engine alone, the electric motor alone, or a
combination of both to drive the wheels.
Like the Toyota Prius, the Ford Hybrid Escape is a full hybrid.
Another classification for hybrids is series, parallel or split hybrid
system. The Ford Escape Hybrid and Toyota Prius are both split
systems with a planetary gear that allows operation in either the
Circle 111 on Reader Service Card
parallel or series mode. As shown
in Figure 3, in the parallel path
the energy is converted and
directly transmitted to the driving
wheel through a mechanical path.
In the series mode, the energy is
converted to electrical energy by
the generator.
Ford’s Escape Hybrid
demonstrates the added system
complexity with hybrids. The
Escape Hybrid brings together:
• Transaxle from Aisin AW that
includes a 70 kW, 400 V electric
motor,
• 330 V nickel-metal hydride
battery pack from Sanyo,
• 400 V, 300 A generator,
• Regenerative brakes from
Continental Teves,
• 14 V electric power steering
from NSK,
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C O V E R S T O R Y
• 1.5 kW dc-dc converter from
TDK,
• Battery software from PI
Technology, and
• 2.3 liter, 4-cylinder Atkinson
cycle engine from Ford.
Each of these hardware
elements is controlled by software
that must work together flawlessly
to achieve 35 mpg to 40 mpg in
city driving and avoid reliability
problems [6].
As shown in Figure 3, the
inverter, traction motor and
traction generator combine
for vehicle propulsion, battery
charging and regenerative braking.
The dc-dc converter provides 14 V
power for the vehicle’s electrical/
electronic components. The
key to high efficiency and long
component life in hybrid power
electronics controlling several
kilowatts is integration and
ethylene-glycol cooling. This is
true in the Hybrid Excape, Toyota’s
Crown and Prius, Honda’s Insight
and Civic, and GM’s 42 V Silverado.
Figure 4. Dc-dc converter used in Toyota’s Crown 42 V THS-M compared to
surface-mounted TO-220 D 2 PAK commonly used in today’s 14 V vehicles [7].
Courtesy of Toyota Motor Company.
18 WARD’S AUTO ELECTRONICS | OCTOBER 2004
CONVERTING THE VOLTAGE
Toyota designed a 1.2 kW dc-dc converter for its dual-voltage
42 V Crown THS-M (Toyota Hybrid System — Mild). The layout in
Figure 4 shows some of the packaging-related problems associated with
switching higher power. Three 6.8 mm x 5.9 mm 75 V trench MOSFETs
are used in this converter. Using synchronous rectification instead of
the diode improved peak efficiency from 90.8% to 92.8% in the 20 A
range and by almost a percent at maximum current (85 A) range. Note
the multiple wire bonds used to connect to the power die and to connect
the substrate with the external connections. In contrast, the industry
standard surface-mounted D 2 PAK has a footprint of 10.2 mm x 15.4 mm
(0.4 inches x 0.6 inches) and a maximum die size of 4.3 mm x 6.9 mm
(0.170 inches x 0.270 inches). This package is used for many of the higher
power loads in today’s 14 V vehicles that are typically 100 W (average) or
less [7].
In the new Prius, two dc-dc converters are used. One boosts the
voltage from the 202 V battery to provide 500 V power for the traction
motor and generator. The other dc-dc converter reduces the voltage
from 202 V to 14 V to power traditional vehicle loads. Based on the
number of existing 14 V components, high-voltage transitions will be
common in higher-voltage vehicles.
OTHER POWER CHANGES
Since the engine is usually off in hybrid vehicles at idle and could
be off during braking, vehicle systems that rely on the engine for power
must be addressed. These systems include power steering, A/C and
braking. The answer to the engine-off situation is frequently the use
of electric power steering (EPS) or electrohydraulic power steering
(EHPS), electric A/C, and
regenerative braking. An electric
clutch is added to the system
that disengages the components
from the engine when it is shut
off. Figure 5 shows the clutch
for disconnecting the loads
normally driven by the engine in
GM’s belt alternator system (BAS)
mild hybrid. The clutch will be
electrically operated as it is in the
Toyota Crown.
In the smaller-size hybrid
vehicles, electric power steering
can be implemented with 14 V.
However, larger vehicles such
as the Chevy Silverado and GM
Sienna require higher voltage and
take advantage of the 42 V bus and
available 42 V EPS systems. Peak
current in a 14 V EPS can be as high
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C O V E R S T O R Y
Vehicle Model Year Voltage Motor Type Engine Comments
Chevrolet
Silverado/
GM Sierra
2004 42 V 14 kW ISAD 5.3 L, V-8
stop-start system and gets 12% to 15% improved fuel economy. A
variation of the Allison Hybrid Bus System offered in 2003 will be its
first full-hybrid passenger vehicle and will be used in future full-size
SUVs and pickup trucks in 2007-2008 [7].
More recently, Toyota and Ford have scrambled to find ways
to increase capacity based on higher fuel prices and higher-thanexpected
consumer interest in fuel-efficient hybrids. This is just the
beginning. We are in for an even more exciting ride.
Chevy Equinox 2006 BAS
Fuel economy improvements of about
12% and 2 110 Vac power source
Saturn Vue 2006 42 V 7 kW BAS 2 L, 4 Cyl. CVT. 12 to 15% better fuel economy
Chevrolet Malibu 2007 42 V 7 kW BAS 4 Cyl. CVT. 12 to 15% better fuel economy
Full-size
pick-up truck
(Silverado/Sierra)
SUVs
(Tahoe & Yukon)
2008 300 V
2008 300V
Table 2. GM’s recently updated (Fall 2003) hybrids plan.
as 100 A. For the same value motor
that value reduces to slightly more,
than 33 A for a 42 V supply.
EXPECT CHANGES
With the demonstrated
success of Toyota’s New Prius
and the Honda Civic and new
vehicles from Ford, GM, Daimler
Chrysler, Toyota and Honda,
car makers will soon know even
more about what sells and what
consumers want from a hybrid
vehicle. However, the amount of
technical challenges, changing
economic outlook impacting
development budgets and fuel
concerns shifting consumers’
interest from fuel-guzzling
SUVs to fuel-efficient vehicles
have already provided shifts
in product plans and launch
schedules.
In 2003, GM announced
a change in its plans for the
Saturn Vue from a full hybrid
with two motors and a transaxle
that would have achieved 50%
improved fuel economy to a lessexpensive
42 V belt alternator
starter (BAS) mild hybrid system
with a continuously variable
transmission (CVT) that is a
20 WARD’S AUTO ELECTRONICS | OCTOBER 2004
(2) 30
kW
(2) 30
kW
AHS II V-8
AHSII V-8
Allison-derived Advanced Hybrid
System II, 25 to 30% improved fuel
economy
Allison-derived Advanced Hybrid
System II, 25 to 30% improved fuel
economy
Figure 5. GM’s 42 V belt alternator system shows the additional clutch and special
consideration that must be given for A/C compressor, power steering (P/S) and water pump.
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C O V E R S T O R Y
HYBRID VEHICLES PROPEL INCREASED ELECTRONICS CONTENT
THE ELECTRONIC
GAS TANK
The hybrid vehicle needs
energy storage for the
electric portion of its
propulsion system in addition to
the gasoline or diesel fuel tank
for the engine. Long term this
could come from fuel cells, but
today batteries provide the energy
storage. The 12 V battery has gone
through various improvements
during its 50-some years as the
reigning vehicle electrical system
voltage. However, the electrical
propulsion in the hybrid requires
storage capability beyond
traditional 12 V battery technology.
Battery chemistries that are
being evaluated and developed
for hybrid vehicles include
valve-regulated lead acid
(VRLA) batteries, nickel metal
hydride (NiMH) and Lithium
ion (Li-ion) technologies. Key
concerns with these batteries in
hybrid applications are cost and
reliability. As shown in the spider
chart, VRLA technology excels
in economics, cold cranking and
recycling infrastructure because
it is an improvement on the
established lead-acid battery. In
contrast, Li-Ion technology has
the highest energy density while
NiMH has the highest specifi c
power and charge acceptance.
Today, 42 V vehicles such as
Toyota’s Crown and GM’s Silverado
22 WARD’S AUTO ELECTRONICS | OCTOBER 2004
and Sierra models use VRLA technology. Higher-voltage vehicles such as
the Toyota Prius and Ford Hybrid Escape models use Ni-MH batteries.
In Ford’s Hybrid Escape, the Sanyo battery also includes battery control
electronics.
Toyota reduced the battery voltage from 275 V in its initial Prius to
202 V for the new Prius and used a dc-dc converter to boost the voltage to
500 V. With 500 V, they use a 50 kW traction motor instead of 33 kW motor
used with power direct from the 275 V battery. The voltage conversion
A comparison of key battery characteristics for valve regulated lead acid (VRLA)
versus NiMH versus Li-Ion [8]. Background: Sanyo’s 330V sealed NiMH in the Ford
Escape has 250 D size cells in series.
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C O V E R S T O R Y
provides increased power with
lower battery voltage, placing less
stress on the high-voltage energy
source.
The replacement cost of
the battery in the Toyota Prius
has been quoted at $3,000.
With unproven history, vehicle
manufacturers are offering
warranties of eight years/100,000
miles on the initial hybrids.
Nissan displayed Li-ion
batteries at the 2003 Tokyo Motor
Show using laminated cells that
are less than half the size of rival
systems. A 25 kW battery would
have a volume of only 15 liters
compared with 45 liters using
conventional technology. The thin
cell construction also improves
cooling [7].
Supercapacitors/
ultracapacitors can relieve the
stress on the battery and provide
peak energy capability when
needed. Ultracapacitors have
been used in 42 V and fuel cell
development vehicles to cover
ABOUT THE AUTHOR
Randy Frank is a freelance writer
and president of Randy Frank
& Associates, Ltd., a technical
marketing consulting firm based in
Scottsdale, AZ. He can be reached
at rfrank68@cox.net.
24 WARD’S AUTO ELECTRONICS | OCTOBER 2004
Ultracapacitors provide additional energy storage capability for hybrids and
potentially any vehicle application where momentary peak energy is required.
Courtesy: Maxwell Technologies.
the peak energy needs in portions of the system and avoid increasing
the size of other costly components. Maxwell Technologies introduced
a standard size D Cell ultracapacitor earlier this year that is expected
to drive down the cost and ease the integration of the technology into
production vehicles. The first production use of ultracapacitors will most
likely occur on a 14 V vehicle in 2005.
REFERENCES:
1. Richard Truett, “DCX, GM Go Slow On Hybrids,” Automotive News,
July 5, 2004.
2. Mary Connelly, “People Keep Asking: ‘That Thing got a Hemi?’”
Automotive News, Feb. 16, 2004.
3. Hansen Report on Automotive Electronics, March 2004.
4. “Light-Duty Automotive Technology and Fuel Economy Trends: 1975
Through 2004,” U.S. Environmental Protection Agency, EPA420-R-04-
001, April 2004.
5. Venkateswara Anand Sankaran, “Introducing Power Electronics in
Ford Hybrid Escape Vehicle,” Power Electronics Society Newsletter,
Vol. 16, No. 3, October 2004, pp. 13-15.
6. Richard Truett and Amy Wilson, “Systems Don’t Mesh so Ford Hybrid
is Delayed,” Automotive News, Nov. 3, 2003.
7. Intertech’s “Power Management in Today’s and Future Automotive
Systems,” including the 2004 update http://www.intertechusa.com/
studies/PowerManagement/PM_Study.htm
8. Richard Johnson, “Spiral Wound Lead-Acid Batteries for 42V
Applications,” SAE 42 V Challenges Toptec, April 29-30, 2002, Troy, MI.
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