Riding Out Automotive Transients : Architecting Front End Power Conversion Stage for Automotive Off-Battery Loads

With rapidly expanding electronic content in latest generation of cars, there is an ever increasing need for power conversion from the car battery rail. The 12-V battery rail is subject to a variety of transients. This presents a unique challenge in terms of the power architecture for off-battery systems. This presentation introduces the different types of transients that occur in automotive battery rails, the causes of those transients, and the standards and specifications defining the test conditions for those transients.

The presentation demonstrates the different power architectures for power conversion and protection circuits to ride out the transients and minimize the interruption to the loads. It compares the advantages and trade-offs associated with buck-boost, boost, and pre-boost approaches for surviving cold-cranks and load dump. The different approaches for reverse battery protection are presented and the advantages of smart diode compared to alternate methods.

What you will learn: This presentation equips the designer with a deeper understanding of automotive transients and the approaches to tackle these transients while architecting the power conversion stage.

1. Automotive transients introduction

This video presents a short overview of automotive frond-end and the transients tackled by the frond-end power conversion stage connected to an automotive battery rail.

# Title Duration
1.1 Automotive transients introduction
In this video, we will provide an overview of the main 12-V automotive battery rail transients that are handled by the power stage design.
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2. Automotive transients explained

This section presents a high level overview of automotive board net and the describes the conditions that the the tests simulate. These include:

  • Reverse polarity
  • Jump start
  • Load sump
  • Starting profile
  • Superimposed ac
# Title Duration
2.1 Automotive transients explained
In this section we discuss the actual conditions that the conducted immunity tests cover.
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3. Architecting the dc-dc stage for automotive transients

This section presents an approach to architecting the dc-dc conversion stage to handle the transients on automotive battery rail. Following topologies are covered:

  • Buck-boost
  • Always-on boost + buck
  • On-demand boost + buck
  • Buck + post boost

Pro/cons of the different approaches are also discussed.

# Title Duration
3.1 Architecting the DC-DC stage for automotive transients
This section presents the different ways of architecting the dc-dc stage for automotive frond end.
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4. Reverse battery protection

This section presents the different methods of protecting the electronic loads connected to the automotive battery rail in the event of accidental reverse battery connection. The methods covered include:

  • Schottky diode
  • PFET + discretes
  • Smart diode + NFET
# Title Duration
4.1 Automotive reverse polarity protection
In this video we will review the reverse battery protection stage of the automotive frond-end power stage.
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5. Riding out automotive transients using buck-boost dc-dc stage

This section presents the buck-boost dc-dc converter as an effective and efficient solution for the wide vin automotive battery rail. The advantages compared to pre-boost and two stage solutions are presented. Also contains an overview of buck-boost converter and controller offerings convering various current and power levels.

# Title Duration
5.1 Riding out automotive transients using buck-boost
In this section we look will look at the buck-boost dc-dc topology for automotive front-end power conversion.
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