Railway Power Applications

Railway Power Applications
Application Note 04/26/12 Rev. 1
Summary
SynQor has developed the InQor and RailQor product
lines for the industrial and transportation industries.
These ruggedized converters are specifically designed
for the harsh environments associated with such
applications. This application note addresses the
European standards EN50155 and RIA12 and how to
meet these standards using the InQor and RailQor
series of dc-dc converters
Introduction
The standards EN50155 (IEC571) and RIA12 specify the design requirements of electrical equipment
for railway rolling stock equipment applications. Included in these specifications:
•
•
•
•
•
Input Voltage Range
Surge Requirements
Power Interruption and Backup
Operational Temperature
Shock and Vibration
SynQor has two families of converters designed to meet the requirements found within these
specifications: InQor and RailQor. The InQor family offers products in a wide range of form factors,
input ranges, and output power levels to meet the requirements of almost any industrial application.
The RailQor family has been developed specifically for rail transportation requirements where low
power dissipation and no need for cooling is often desired, but at less power density than found in
InQor converters.
Operating Input Voltage Range
(Input power for rolling stock equipment may be in several voltage ranges with additional transient levels)
EN50155 (IEC571) requirements
“Electronic equipment supplied by accumulator batteries without a stabilizing device shall operate
satisfactorily for all of the values of the supply voltage within the range defined below (measured at
the input terminals of the equipment)”
• Static Input Range Definitions
- Minimum Voltage = 0.7 Vin
- Nominal Voltage = Vin
- Rated Voltage = 1.15 Vin
- Maximum Voltage = 1.25 Vin
• Transients
Voltage fluctuations between 0.6 Vin and 1.4 Vin not exceeding 0.1 second shall not cause deviation
of function.
• Surge
Voltage fluctuations between 1.25 Vin and 1.4 Vin not exceeding 1 second shall not cause damage;
equipment may not be fully functional during these fluctuations.
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Railway Power Applications
EN50155 Requirements
Nominal
Continuous Input
Input (Vin)
Transient Input
Low (0.1 s)
0.6 Vin
0.7V–1.25V
24V
72V
110V
24V – 110V
RailQor Capabilities
17V– 30V
50V– 90V
77V–137V
17V–137V
Product
Family
High (1 s)
1.4 Vin
14V– 34V
43V–101V
66V–160V
14V–160V
Continuous
Input
RQ18
RQ72
RQ1B
RQ68
9V– 36V
42V–110V
66V–160V
12V–150V
EN50155 Requirements
Nominal
Continuous Input
Input (Vin)
0.7V –1.25V
12/24V
24V
36V
48V
72V
12.6V–
16.8V–
25.2V–
33.6V–
50.4V–
110V
77V–138V
9V – 40V(1s)
42V–110V
66V – 170V(1s)
12V – 170V(1s)
InQor Capabilities
Transient Input
Low (0.1 s)
0.6 Vin
22.5V
30V
45V
60V
90V
Transient
Input
Product Family
Continuous Input Ranges
High (1 s)
1.4 Vin
10.8V
14.4V
21.6V
28.8V
43.2V
25.2V
33.6V
50.4V
67.2V
100.8V
66V
154V
IQ18
9V– 36V
IQ36
18V – 75V
IQ72
42V –110V
IQ1B
66V –160V
IQ32
9V– 75V
IQ70
34V –135V
IQ64
18V –135V
IQ68
12V –150V
IQ90
34V –160V
Table 1: Input Specifications for EN50155
Both InQor and RailQor standard product have the capability to exceed all of the voltage and
transient requirements stated in EN50155.
Surge Protection
Equipment must be protected from the surges listed in Table 2 for each of EN 50155 and RIA 12, with
varying voltage levels, durations, and source. impedances.
Direct Voltage Spikes, Line-Line and Line-Earth Coupling
EN50155
RIA 12
Voltage
Duration
Source Impedance
1800V
50µs
100Ω
8400V
0.1μs
100Ω
Voltage
800V
1500V
3000V
4000V
7000V
Duration
100μs
50μs
5μs
1μs
0.1μs
Source Impedance
5Ω
5Ω
100Ω
100Ω
100Ω
Table 2: Surge protection levels, duration and source impedance.
The preferred method of protection from such surges is to divert the
energy from the converter’s input and hold the peak voltage below the
converter’s maximum transient input voltage specification. A transient
voltage suppressor (TVS) is a good device for this purpose. It should be
connected across the converter’s input terminals to take advantage of
filtering impedances between the transient source and the converter. Any
additional filtering inductance will help reduce the current in the TVS and
limit its clamping voltage. See Z1 of Figure 1. The TVS must be selected
to suppress voltages that would otherwise surpass the input voltage
maximum of the circuitry it is protecting, while absorbing the full amount
of energy provied by the transient.
RIA 12 Surge Protection
Nominal Input
24V
36V
48V
72V
110V
3.5 Vin
84V
126V
168V
252V
385V
Table 3: Surge Voltages
RIA12 further specifies that equipment must withstand a surge voltage of 3.5 times the nominal input
voltage for 20 ms.
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Railway Power Applications
If a Transient Voltage Suppressor (TVS) is used to guard against this voltage, the approximate energy
in the TVS is given by the following equation for a typical 110V input system:
E=(
3.5 Vin – Vtvs
Rs
)
x Vtvs x t
385V – 160V )
x 160V x .02 = 3600 joules
0.2
A typical SMB package 160 V TVS can only dissipate on the order of 10 joules, making a TVS
impractical. A surge isolation circuit is required and component values will be determined by the
amplitude, duration and converter input power level. Figure 1 details such a circuit.
E=(
Figure 1: Surge isolation circuitry
VIN
VIN
R3
D5
R4
Q2
R10
R16
R5
C4
Z1
R14
R1
R2
D3
R9
C7
IN+
R11
R13
C2
R7
C1
V+
U1
OUT
Q1
R15
IN-
U2-A
D1
R6
DC/DC
IN_RTN
U2-B
R8
D2
C5
GND PAD
R12
D4
C3
IN_RTN
Transient Suppression Circuit Description
The SynQor Transient Suppression Circuit is designed to protect SynQor converters from the high
voltage surges called out in the specifications of RIA 12. The circuit acts as a quick disconnect of
the input power return line when a voltage surge of sufficient value trips a precision comparator
circuit. If sufficient bulk capacitor is included in the design, the dc-dc converter will continue to
deliver its output power during the over-voltage surge. Otherwise, the converter will shut down
and automatically restart once the surge is over. In either case, when the circuit reconnects the input
power return line, it does so in a manner that limits the inrush current drawn from the dc power
source.
The following is an outline of the operation of the transient suppression circuit shown in Figure 1.
Q1 is the disconnect switch located in the return line of the dc input power. It is rated at a voltage
above the RIA 12 surge voltage. It is chosen specifically to be able to handle the temporary high level
of dissipation that results when, after a surge event, it is gradually turned back on to limit the inrush
current drawn from the dc power source.
Q1 is driven by U1, an LM5112 gate driver. This driver has two inputs and consumes low quiescent power.
R15 and C3 slow the turn-on time of Q1 in order to limit the in-rush current that results when Q1 is
turned back on after the surge event. D4 shunts R15 for a quick turn-off time.
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Railway Power Applications
Under-Voltage Lock-Out (UVLO) and Over-Voltage Protection (OVP) are provided by the dual
comparator, TLV2702 (U2). This comparator has a quick response time to react to the 2ms surge rise
times specified in RIA 12.
UVLO and OVP share the same Vin divider ladder comprised of resistors R3, R4, R5, R14, and R7.
Multiple series resistors are used to decrease the voltage and power stresses presented to each
individual component.
C1 provides a high frequency noise filter, with a 0.6us time constant, for the sensed input voltage.
UVLO is disabled by default with an open value for R13. It is common to rely on the UVLO of the
dc-dc converter for this function. Should it be desired, UVLO can be set in the transient suppression
filter by biasing the positive input of U2 with resistors R13 and R6 in relation to the voltage sensed
at the negative input of U2. R12 provides UVLO hysteresis.
D1 is a 2.5V precision reference for the comparators. It requires 65uA minimum and is provided with
115uA minimum as the circuit is designed.
OVP is set to nominally activate 2 to 3V below the maximum input voltage allowed by the dc-dc
converter with hysteresis provided by R11.
D3 protects the comparator inputs by shunting to D1 when Vin creates a voltage greater than a diode
drop above the 2.5V reference.
The circuit is powered through depletion mode MOSFET Q2, rated at 1000V.
The voltage generated at the source of Q2 is the sum of its turn-off source-gate threshold voltage
(specified in a range of 1.5V to 5V over temperature) and the 8.2V generated by zener diode D2. This
provides power to U1 and U2 with a nominal voltage in the range of 9.7V to 13.2V.
R1 limits the current provided by Q2. The present design has a minimum current limit of 1.5mA and
maximum of 6.7mA, depending on the source-gate threshold voltage of Q2.
TVS Z1 is used at the input of the circuit to handle the 800V and 1500V transients specified in EN
50155 and RIA 12. It should be rated above the 3.5(Vin) transient voltage specified by RIA 12 to
prevent damage by this transient.
The 3000V, 4000V, and 7000V short (and low energy) transients specified in RIA 12 can be handled by
a 10uF or greater bulk electrolytic capacitor at the output of the transient suppression circuit. The
dc-dc converter requires an electrolytic capacitor across its input anyway, and it is this capacitor that
is represented by C5 in the schematic.
There is a maximum permissible value for the capacitance of C5 due to the need to limit the dissipation
in Q1 when it is gradually turned back on. If more capacitance than this value is needed to keep the
dc-dc converters running during the surge event, then an additional electrolytic bulk capacitor, C4,
should be added. Diode D5 allows this capacitor to provide energy to the dc-dc converter during
the surge event, but keeps it from needing to be instantly recharged when the surge event is over.
Instead, the recharging of C4 occurs slowly through resistor R16.
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Railway Power Applications
Circuit Application Notes
Once disconnected from the input via the transient suppression circuit, the downstream dc-dc
converter will rely on the bulk capacitance at its input for energy. RIA 12 specifies that a system
shutdown is not considered a failure if an auto-recovery occurs and operational performance is
not seriously affected. If sufficient bulk capacitance is not provided to power the dc-dc converter
throughout the surge event, the converter will shut down when its input voltage drops below its
UVLO threshold. The converter will then automatically restart, after its specified startup inhibit delay,
once the transient suppression circuit turns Q1 back on and a connection is re-established to the
power source.
To size C4 to run the converter during the 20ms over-voltage surge specified in RIA 12, one must first
calculate the energy required.
E=Pin x 20ms
Where Pin is the input power to the converter.
Then the value of the capacitance is chosen so that it’s beginning voltage, Vstart, does not discharge
to an ending voltage, Vend, that would trigger the UVLO of the dc-dc converter.
C4 + C5= 2xE
(V start 2 - V end 2 )
As mentioned above, there is a limit to how large C5 can be. Its maximum value is limited by the
power dissipation capabilities (safe-operating-area) of Q1. See SynQor application note “Input
System Instability” for notes on selecting an appropriate stabilizing capacitor. If more total bulk
capacitance is required for energy storage, it needs to be provided by C4 with the connections shown
in the schematic. If greater bulk capacitance is needed for filtering, the power handling capabilities
of Q1 should again be considered.
The charging resistor, R16, should be selected to slowly charge C4, but fast enough so that C4 is fully
charged within 10s to meet the maximum surge repetition rate specified in RIA 12. It should also be
rated for enough power to handle the charging requirement. In our example circuit, R16 is 15K to
charge a 330uF capacitor in 5s and is rated for 2W of dissipation for a nominal 110Vin application
discharging down to 66V during the 20ms 385V surge.
It is important to be mindful of the dissipation occurring in Q1 as the circuit re-enables after an input
voltage surge event. When Q1 reconnects the input voltage to the input of the converter, it must
now dissipate the energy associated with delivering current to the running dc-dc converter (if it is
still running) and the energy associated with recharging the bulk electrolytic capacitance, C5. The Q1
specified in Table 4 for the transient suppression circuit will work well over the nominal input range
as specified by EN50155 and be able to handle a maximum value for C5, as listed in Table 4, while
delivering 60W of power to the input of the dc-dc converter. If a different component is chosen, care
must be taken to make sure the Safe Operating Area (SOA) curve for the substituted transistor can
handle the conditions required to charge C5 and provide power to the dc-dc converter.
Component
R7
Q1
C4
C5
RQ1B
RQ72
6.04K
IPB50R199
330μF
47μF
9.53K
IPB50R199
820μF
100μF
RQ18
28.7K
IPB200N153
8200μF
100μF
Table 4: Components
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Table 4 lists the variable components for each
of the RailQor input voltage families. Figure 2
shows an example of the circuit functioning for
a RIA 12 style surge in a 72Vin nominal system
when powering a downstream IQ72150QTC
InQor dc-dc converter at 50W.
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Railway Power Applications
Appendix A at the end of this application note
details a full Bill-Of-Materials for the transient
suppression circuit. These are the components
used during testing at SynQor and may be
changed to accommodate each particular design
as required. SynQor applications support is
happy to assist in any design.
Figure 2: Waveforms for suppression of 252V transient in 72Vin system.
Trace 1 – Vin (50V/div), Trace 2 – Vout (50V/div), Trace 3 – Output of
IQ72150QTC (5V/div)
Power Interruption and Backup Interruption
EN50155 (IEC571) requirements
Interruptions of up to 10 ms may occur on input voltage
Class S2: 10 ms interruptions shall not cause any equipment failure.
The bulk capacitance circuitry of Figure 1, comprised of C4, D5, and R16 can serve as a hold-up
mechanism to prevent any disruption of the power supply during power interruptions. Values should
be chosen based on desired duration of hold-up and recharge time. Consult SynQor support for
assistance.
Supply Change Over
From EN50155
Equipment supplied with power alternatively from an accumulator battery and a stabilized source
shall operate satisfactorily as follows:
• Class C1: at 0.6 Vin during 100 ms (without interruptions)
• Class C2: during a supply break of 30 ms
Class C1 is met within the operating input voltage range of the InQor/RailQor series as described
above in the Operating Input Voltage Range section.
To meet the requirements of Class C2, the capacitance at the output of the transient circuit would
have to be increased so the converter has at least minimum voltage at the end of the line break
transient to maintain its output. This can be achieved with the circuitry in Figure 1 comprised of C4,
D5, and R16 with the correct sizing of components. For higher power levels, this may be prohibitive.
Contact SynQor support for assistance.
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Railway Power Applications
Operational Temperature
EN50155 (IEC571) requirements
Electronic equipment shall be designed and manufactured to meet the full performance specification
requirement for the selected temperature categories as stated in Table 5.
EN50155 Requirements Ambient Temperature
Operating Temperature
Classes
External Ambient
Temperature
Internal Cubicle
Temperature
Internal Cubicle Overtemperature
Air Temperature Around
PCB
T1
T2
T3
TX
-25 to +40ºC
-40 to +35ºC
-25 to +45ºC
-40 to +50ºC
-25 to +55ºC
-40 to +55ºC
-25 to +70ºC
-40 to +70ºC
+15ºC
+15ºC
+15ºC
+15ºC
-25 to +70ºC
-40 to +70ºC
-25 to +85ºC
-40 to +85ºC
Table 5: Ambient Temperature
The specified operating temperature of the InQor products is -40 to +100ºC case temperature. In
addition, these products can be directly mounted to a chassis for improved cooling.
The RailQor family of products is designed to operate at ambient temperatures of -40 to +100ºC as
well. Furthermore, RailQor converters operate without derating to temperatures of +85C without
cooling, and may be advantageous in ‘closed box’ designs where the chassis cannot be used as a
heat sink and no airflow is provided. Often, forced-air cooling is avoided due to reliability concerns
related to fans. Due to the static nature of such an environment, it is permissible to operate RailQor
converters at baseplate temperatures up to 125ºC. See RailQor product datasheets for further
information.
Shock and Vibration
Per EN50155 the equipment shall be able to withstand, without deterioration or malfunction,
vibrations and shocks that occur in service.
•
•
•
•
•
Frequency Range: 5 to 150 Hz
Cross-over Frequency: 8.2 Hz
Displacement Amplitude: 7.5 mm
Acceleration Amplitude: 20 m/s2
Semi-sinusoidal Shock: 50 m/s2 for 50 ms
InQor and RailQor products are filled with a permanently elastic thermally conductive encapsulant
that enables the device to survive rigorous shock and vibration conditions by mechanically bonding
all components to the case through the encapsulant. This provides the mechanical strength to meet
the requirements, however, care must be taken in PCB design and/or wiring to ensure that external
stresses to the converter do not damage the modules’ pins.
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Railway Power Applications
Appendix A
Example Bill-of-Materials for Transient Suppression Circuit
Ref
Des
Value
Q2 1000V
U1
U2
D1
2.5V
D2
8.2V
D3
75V
D4
75V
D5
400V
R1
750
R2
15.0K
R3
100K
R4
100K
R5
100K
R6
10.0K
R8
8.25K
R9
33.2K
R10 1.00K
R11 1.00M
R12 OPEN
R13 OPEN
R14
100K
R15 16.5K
R16
15K
C1
100pF
C2 0.47uF
C3
1.0uF
C7 1000pF
Z1
430V
Tolerance
0.10%
1%
1%
0.1%
0.1%
0.1%
0.1%
1%
1%
1%
1%
1%
0.1%
0.1%
1%
1%
5%
10%
10%
5%
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Description
Package
Vendor
Depletion Mode FET
7A MOSFET Driver
Dual Power Comparator
Precision Shunt Reference
Zener Diode
Low Leakage Diode
Low Leakage Diode
Super-Fast Rectifier
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor, 2W
Capacitor, C0G, 100V
Capacitor, X7R, 50V
Capacitor, X7R, 50V
Capacitor, C0G, 100V
TVS
D PAK
LLP-6
MSOP-8
SOT-23
SOD-323
SOD-523
SOD-523
PowerDI-123
0603
0603
0603
0603
0603
0603
0603
0603
0603
0603
0603
0603
0603
0603
IXYS
National Semiconductor
Texas Instruments
National Semiconductor
ON Semiconductor
NXP/Philips
NXP/Philips
Diodes, Inc.
Yageo
Yageo
Panasonic
Panasonic
Panasonic
Panasonic
Yageo
Yageo
Yageo
Yageo
IXTY01N100D
LM5112
TLV2702
LM4050AEM3X-2.5
MM3Z8V2ST1G
BAS716
BAS716
DFLU1400-7
RC0603FR-07750RL
RC0603FR-0715K0
ERA-3AEB104V
ERA-3AEB104V
ERA-3AEB104V
ERA-3YEB103V
RC0603FR-078K25
RC0603FR-0733K2
RC0603FR-071K00
RC0603FR-071M00
Panasonic
Yageo
ERA-3AEB104V
RC0603FR-0716K5
0603
0805
0805
0603
TDK
Murata
TDK
TDK
Panasonic
C1608C0G2A101J
GRM40X7R474K050AL
C2012X7R1E105KT
C1608C0G2A102J
ERZV20D431
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