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Bourns® Model SRP Series Inductors used in automotive start-stop applications
Switch Main
Start-stop powertrain architecture is becoming widespread due to the calculated savings of 10 % in CO2 emissions as well as the fuel efficiency that can be achieved using this technology. Typically, the battery voltage in an internal combustion engine (ICE)
car drops to as low as 7 V during engine switch on. Such a low voltage may cause the onboard electronics to malfunction. A start-stop vehicles’ engine is continuously shutting down when the car is stopped and restarting when the car starts to move.
Switch Main
battery 12V
+ -
Reserve battery
+ -
battery 12V
+ -
Reserve battery
+ -
ΔVout = ESR (Iout/((1-D))+∆IL/2)
Infotainment circuits, clusters, etc.
Where Iout = Output current, ΔIL is the ripple in the inductor current, D is the duty cycle and ESR is the output capacitor’s equivalent series resistance.
SRP Series
Automotive Inductor L1
Vin
+ -
Infotainment circuits, clusters, etc.
A start-stop system uses reserve batteries isolated by a switch from the rest of the car. When the ICE turns off, the switch connects the reserve battery through a boost converter to power the onboard electronics. The output capacitor and switching inductor on the converter are essential to ensuring smooth output voltages with low ripple voltages and low electromagnetic interference (EMI). The overall ripple voltage is a function of the ripple current in the inductor as well as the equivalent series resistance (ESR) of the capacitor. The ripple voltage can be calculated using the following formula:
SRP Series
Automotive Inductor L1
Vin
+ -
+ -
Switch
D1 D
Vout + C1
Low ESR capacitor
+ -
Switch
D1 D
Vout + C1
Low ESR capacitor
Power inductors designed for automotive start-stop applications are rated to high temperature automotive conditions and are packaged in high current SMD shielded housings. Currently the average car dissipates 3.2 KW of electrical power; this is predicted to increase to 20 KW by the year 2020. The start-stop converters must be scalable in their current carrying capabilities.
Several of the Bourns® Model SRP series of high current flat wire SMD inductors meet all of these criteria with a broad range of inductance values for high frequency, high current boost converters. They are approved for automotive applications; an operating temperature of 150 °
C makes them suitable for powertrain converters. For more information visit
avnet-abacus.eu/bourns
15 focus magazine - issue 14
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