Abstract:
Numerous design challenges have been encountered due to electrical transients in the circuits
and subsystems available in automobiles. These challenges became prominent, especially
during the transition from traditional fuel-based automobiles to Hybrids, PHEVs (Plug-in
hybrid electric vehicles) and BEVs (Battery EV). Traditional auxiliary operations such as air
conditioning and heating directly from the HV battery, while keeping the galvanic isolation of
high-voltage (HV) and low-voltage (auxiliary) regions in the automotive supply system, are
examples of the associated design challenges encountered. Moreover, EM coupling and
transient vulnerability issues affect the sensitivity of deliberate sophisticated solid-state control
circuits like DC-DC converters. Furthermore, the transient nature of the loads beyond the
acceptable power quality standards will impart severe stresses on the auxiliary system. In
battery-supported automobiles, the DC-DC converter with an onboard 200-800 V high voltage
battery generates and caters 12 VDC (or 48 VDC) to power up auxiliary elements such as
headlights, other lights, wipers, winkers, etc. Thus, measurements and analysis have been
carried out to identify the risk levels of such transients for vehicular control, in preference to
the DC-DC converters which connect the HV battery and auxiliary side. The aforementioned
transient measurements were carried out covering a fleet of late-model hybrid and PHEV
automobiles using a Tektronix P6015A High Voltage Probe and a PicoScope 3206A
Oscilloscope with 200 MHz resolution. There were 354 transients observed in this study and
amplitudes of the voltage transients were recorded up to 45.20 V. The rise time of the transients
were recorded within the range of 0.3 – 50 μs and respective burst durations were up to 0.5 ms.
The recorded transient amplitudes exceed the rated 13.8 V output value of the commercially
available DC-DC converters. These findings will be an eye-opener to the current market of
electric vehicles. Thus, it is suggested that manufacturers should improve the respective
withstand capabilities against the transients generated in electromechanical segments in EVs.
