Application Note RC-Drives, RC-DF and RC-DA

R C-Dr ives, R C -Dr ives F ast an d R C -D r i ves
Autom ot i ve
R C-Dr ives IGB T for c ons u mer a nd
aut om ot i ve appl i ca ti ons
Rebec
Mitja Note
Application
About this document
Scope and purpose
This application note describes a cost-optimized discrete IGBT solution in order to address to the pricesensitive consumer drives market. Furthermore, a comparison will be made between the two technologies
RC-Drives (RC-D) and RC-Drives Fast (RC-DF) IGBTs. The RC-D device is optimized for low conduction losses
while the RC-DF device is optimized for low switching losses.
Intended audience
This document is intended for design engineers who want to improve their high voltage consumer drive
applications.
Table of contents
1
Introduction and short description of the product family .............................................................. 2
2
2.1
2.2
Static and dynamic behavior ......................................................................................................... 4
Static behavior .................................................................................................................................... 4
Dynamic behavior ............................................................................................................................... 4
3
Application ..................................................................................................................................... 7
4
4.1
4.2
4.3
In-circuit application test on 200 W motor drive board .................................................................. 9
Efficiency ............................................................................................................................................. 9
Thermal behavior .............................................................................................................................. 10
Cooling considerations ..................................................................................................................... 11
1
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RC-Drives IGBT for consumer and automotive applications
Introduction and short description of the product family
1
Introduction and short description of the product family
The RC-Drives IGBT technology was released by Infineon at the end of 2009 as a cost-optimized solution to
address the price-sensitive consumer drives market. This basic technology provides outstanding
performance in BLDC motor drives adopting block commutation–type of modulations, where one or both
IGBT in the half-bridge are left conducting for 120° of the motor electrical angle (Dae-Woong Chung et al.,
IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL. 46, No. 3, June 1999). Due to the low conduction
losses of both IGBT and integrated diode, the overall losses are drastically reduced. This type of control is
commonly found in fridge compressors: by limiting the hard switching events the dv/dt and dI/dt
commutation slopes are avoided, therefore the harmonic content injected into the motor windings (hence
the EMI) is reduced. Below we have a typical example of this type of commutation found on a 100 W
commercial fridge compressor:
High side
Figure 1
Low side
High side and low side gate signals for 120° PWM commutation switching
Another application that benefits from the low on-state losses or the RC-Drives is found in domestic aircon
systems: the ~1.5 kW BLDC compressor is driven by IGBTs switched by full sinusoidal PWM hard switching at
moderate switching frequencies of 5 to 8 kHz. Again in this case a device optimized for low conduction
losses provides an overall loss reduction.
However, the trend observed in low power drives for outdoor and indoor fans of domestic aircon systems as
well as industrial fans and pumps up to ~200 W is to increase the PWM switching frequency. The reason is
two fold: on one side the size of the output filter can be reduced by keeping the same current ripple. On the
other side, in small motor drives adopting sensor-less FOC (Field Oriented Control), where a high dynamic
control (torque and speed) of the PMSM motor is required, the higher switching frequency allows to increase
the sampling rate of current and hence the accuracy of reconstructed rotor position.
In order to meet the rising demands of the IGBTs for the low power motor drive consumer market, a new
version of the RC-Drives IGBT is developed: the IGBT and diode losses are optimized to reduce the inverter
Application Note
2
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RC-Drives IGBT for consumer and automotive applications
Introduction and short description of the product family
losses at switching frequencies of 18~30 kHz. The new family is called RC-DF, and released in the current
classes from 2.5 A to 15 A in DPAK packages.
Static and dynamic behavior of RC-D and RC Drives Automotive (RC-DA) devices are similar, therefore all
characteristics for RC-D are valid also for RC-DA devices.
Table 1
Part
Product specification for RC-D and RC-DFast
Package
type
Power
[W]
Switching
frequency
VCE
number
[V]
25°C
100°C
25°C
IKD03N60RF
DPAK
40-80
4-30 kHz
600
5
2.5
2.2
IKD04N60RF
DPAK
80-150
4-30 kHz
600
8
4
IKD06N60RF
DPAK
150-250
4-30 kHz
600
12
IKD10N60RF
DPAK
250-600
4-30 kHz
600
20
IKD15N60RF
DPAK
600-1000
4-30 kHz
600
IKU04N60R
IPAK
IKD04N60R
DPAK
80-150
DC to 5 kHz
IKU06N60R
IPAK
IKD06N60R
DPAK
150-250
IKU10N60R
IPAK
IKD10N60R
DPAK
IKU15N60R
IPAK
IKD15N60R
DPAK
Table 2
IC [A]
VCE(sat) [V]
Ets [mJ]
tSC
VF [V]
175°C
25°C
175°C
[s]
Qrr [µC]
25°C
175°C
25°C
175°C
2.3
0.09
0.14
5
2.1
2.0
0.06
0.19
2.2
2.3
0.11
0.19
5
2.1
2.0
0.09
0.26
6
2.2
2.3
0.18
0.28
5
2.1
2.0
0.16
0.34
10
2.2
2.3
0.35
0.52
5
2.1
2.0
0.27
0.62
30
15
2.2.
2.3
0.52
0.78
5
2.1
2.0
0.42
1.00
600
8
4
1.65
1.85
0.24
0.4
5
1.7
1.7
0.22
0.52
DC to 5 kHz
600
12
6
1.65
1.85
0.33
0.56
5
1.7
1.7
0.37
0.80
250-600
DC to 8 kHz
600
20
10
1.65
1.85
0.59
0.93
5
1.7
1.7
0.56
1.22
600-1000
DC to 8 kHz
600
30
15
1.65
1.85
0.9
1.25
5
1.7
1.7
0.76
1.7
VF [V]
Product specification for RC-D Automotive
Part
number
Package
type
Power
[W]
Switching
frequency
VCE
[V]
IC [A]
25°C
IKD04N60RA
DPAK
80-150
DC to 5 kHz
600
8
IKD06N60RA
DPAK
150-250
DC to 5 kHz
600
IKD10N60RA
DPAK
250-600
DC to 5 kHz
IKD15N60RA
DPAK
600-1000
DC to 8 kHz
Application Note
VCE(sat) [V]
Ets [mJ]
100°C
25°C
175°C
25°C
175°C
tSC
[s]
25°C
175°C
25°C
175°C
4
1.65
1.85
0.24
0.4
5
1.7
1.7
0.22
0.52
12
6
1.65
1.85
0.33
0.56
5
1.7
1.7
0.37
0.8
600
20
10
1.65
1.85
0.59
0.93
5
1.7
1.7
0.56
1.22
600
30
15
1.65
1.85
0.9
1.25
5
1.7
1.7
0.76
1.7
3
Qrr [µC]
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RC-Drives IGBT for consumer and automotive applications
Static and dynamic behavior
2
Static and dynamic behavior
2.1
Static behavior
Due to the optimization for fast switching, the VCE(sat) of the RC-DF is increased compared to the RC-D.
However for the target inverter applications in the range of ~100 W the RMS currents are usually limited
below 1 A and here the VCE(sat) increase is limited to ~200 mV both at 25°C and 175°C. A negative temperature
co-efficient of VCE(sat) is observed in this current range, contributing to a reduction of conduction losses in
normal operating conditions, with junction temperature Tj typically ranging from 60 to 100°C.
VCE(sat) comparison RC-D vs RC-DF
4,0
IKD04N60R-25°C
3,5
RC-D
IKD04N60RF-25°C
3,0
IKD04N60R-175°C
Ic (A)
RC-DF
IKD04N60RF-175°C
2,5
2,0
1,5
1,0
0,5
0,0
0,00
0,50
1,00
1,50
2,00
2,50
VCE(sat) (V)
Figure 2
VCE(sat) comparison of the RC-DF vs. the RC-D technology
2.2
Dynamic behavior
The RC-DF maintains the smooth switching behavior and RG controllability of the basic RC-D technology, by
providing drastically reduced turn-off losses of the IGBT. The internal diode is also optimized to reduce the
turn-on losses. The devices are characterized in a classical half-bridge test circuit with inductive load: the
low side IGBT (DUT) is commutated over the high side diode. Therefore, the diode switching improvement is
visible in the IGBT turn-on behavior (see below).
Application Note
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RC-Drives IGBT for consumer and automotive applications
Static and dynamic behavior
Figure 3
Dynamic switching behavior as a function of external RG
The turn-on and turn-off waveforms are clearly showing significantly faster switching: both the tail current
of the IGBT, the Qrr, Irrm and trr of the integrated diode are drastically reduced.
Application Note
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RC-Drives IGBT for consumer and automotive applications
Static and dynamic behavior
RC-D
RC-DF
RC-D
RC-DF
Figure 4
Dynamic switching waveforms: turn-off (top) and turn-on (bottom). Note that the current scales
are different
Application Note
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RC-Drives IGBT for consumer and automotive applications
Application
3
Application
RC-D and RC-DF devices are suitable for home appliances as shown in Figure 6, especially as the power
component of motor drive inverters. This is usually a two-level three-phase inverter driving a three-phase
induction or permanent magnet synchronous motor.
U
V
W
VAC
Figure 5
Three-phase two-level inverter
Figure 6
Commercial air-conditioning split system, showing the motor drive card housed on the back of
the BLDC fan motor
RC-DA is a device that can be used for automotive applications such as, High Intensity Discharge (HID) lamps
and piezo injection. HID lamps have two important issues, a greater starting voltage and the presence of
acoustic resonance. The first issue is resolved by using a sort of starting aid, called igniters, which ignites the
lamp. In order to avoid acoustic resonance and flickering, the designer must avoid the combination of
power fluctuation and operating frequency. The frequency used in the application is higher than 100 Hz and
Application Note
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RC-Drives IGBT for consumer and automotive applications
Application
below 1 kHz. Power fluctuation can be avoided by using square wave alternate current techniques. This
current control can be achieved by using a full bridge that converts the DC current coming from a DC/DC
converter into an AC current for the lamp.
DC Bus
Igniter
LAMP
L
Shunt
Figure 7
HID lamp output stage
Figure 8
Automotive application: piezo injection and High Intensity Discharge(HID) lights
Application Note
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RC-Drives IGBT for consumer and automotive applications
In-circuit application test on 200 W motor drive board
4
In-circuit application test on 200 W motor drive board
4.1
Efficiency
In order to verify the improvement of the RC-DF in a real application conditions, the new devices were tested
on a demo board developed by Infineon and used as test bench to simulate a real air-conditioning outdoor
fan. The board is designed for a 200 W output and consists of an input rectifier stage, inverter stage and
output filter. The IGBTs are driven by a 600 V three-phase driver IC from Infineon (6ED003L06-F), and the
modulation pattern is provided by an 8 bit Infineon microcontroller (XC-878) mounted on an external card.
No heat-sink is required, just thermal vias through the PCB. The control method is sensor-less FOC using a
single shunt-based feedback loop. The board is driving a 200 W induction motor coupled to an adjustable DC
brake, which allows controlling the output power from the inverter. The efficiency is monitored by a
Siemens power meter and case temperature is monitored by an IR camera.
Figure 9
Test set-up for the application measurements
Already at switching frequency of 10 kHz a clear efficiency improvement is observed. At the target fsw of 18
kHz the RC-DF provides 2.8% improvement at 50 W input power and 1.6% at 100 W:
Application Note
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RC-Drives IGBT for consumer and automotive applications
In-circuit application test on 200 W motor drive board
Figure 10
Inverter efficiency as a function of input power and switching frequency
4.2
Thermal behavior
The increased efficiency for the RC-DF translates in lower case temperature, as verified by thermal images
with infrared camera:
Figure 11
Inverter efficiency as a function of input power and switching frequency
The RC-DF shows outstanding thermal performance providing lower case temperature over the entire
frequency range: at the target switching frequency of 18 kHz, the case temperature is lowered by 20°C. The
temperature distribution is quite uniform, as demonstrated by detailed analysis of the thermal images:
Application Note
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RC-Drives IGBT for consumer and automotive applications
In-circuit application test on 200 W motor drive board
Figure 12
Thermal images at Pin= 50 W, fsw= 20 kHz
This translates in increased reliability and longer life expectancy for the device, especially in the harsh
thermal environments to be encountered in a real application. In the case of outdoor fan for domestic split
aircon systems, for example, the board is mounted directly on the back of the motor in a close environment
without airflow. In this case high ambient temperature up to ~60°C can be expected:
4.3
Cooling considerations
When the power range of the inverter exceeds ~200 W, along with careful PCB design (avoid placing devices
too close to each other or to the edge of the PCB), some type of cooling is required for the SMD devices. In
case of DPAK packages, top side cooling is not effective due to the relatively high thickness of the mold
compound on top of the chip and the poor heat exchange. Infineon recommends cooling from the bottom of
the chip by thermal vias through the PCB. Several methods for vias formation are adopted in the industry:
Application Note
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RC-Drives IGBT for consumer and automotive applications
In-circuit application test on 200 W motor drive board
Table 3
Commonly adopted vias concepts
Copper inlays
Production limited and quite
expensive concept. Adopted in
high efficiency converter for
SMPS applications
Copper inlays (Ruwel GmbH)
Thermal vias
Placed around the leadframe or
partially under the drain contact.
Typical vias diameter is 400 µm.
Filled with synthetic resin to
avoid solder voids at RC-Drives
leadframe due to a solder reflow
through the vias. Most common
solution in consumer drives.
Classical thermal vias with resin
Small drill holes
Holes diameter below 0.2 mm for
the thermal vias are filled during
Cu galvanic deposition to avoid
solder reflow.They can be placed
under the drain for the most
effective heat exchange.
Thin-via-concept (small drill holes)
Infineon recommends, when allowed by the process capability of PCB supplier, the small drill holes concept
for optimum power dissipation. The concept was tested successfully on several reference designs and
allowed to reach up to 1.2 kW output power utilizing RC-D devices in DPAK package.
Below an example of small drill holes vias design and related heatsink mounting with isolation foil:
Application Note
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RC-Drives IGBT for consumer and automotive applications
In-circuit application test on 200 W motor drive board
Figure 13
Example of thermal vias and heatsink mounting for RC-D and RC-DF test boards
Application Note
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RC-Drives IGBT for consumer and automotive applications
In-circuit application test on 200 W motor drive board
Revision history
Major changes since the last revision
Page or reference
Application Note
Description of change
14
Revision 1.1, 2015-08-12
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