Automotive Front-End Buck-Boost Regulator Actively Filters Voltage Disturbances

by Timothy Hegarty, Texas Instruments, Phoenix, Ariz., How2Power Today, Jan 16 2017

Focus:
In most vehicles, a centralized passive circuit protection network consisting of a low-pass LC filter and TVS diode is used as a first line of defense for transient disturbance rejection. Automotive electronics located downstream from the protection network are then rated to survive up to a 40-V transient without damage. However, the cutoff frequency required of the LC filter to attenuate disturbances at low frequencies requires bulky passive components. This article details a more-compact, active filter implementation using a four-switch synchronous buck-boost dc-dc regulator (TI’s LM5175) with high PSRR. This cost-effective solution also provides battery voltage regulation and rejection of voltage transients. Article discusses advantages of the four-switch buck-boost versus other buck-boost topologies; optimizing PSRR performance for alternator-induced sinusoidal ripple voltage; and experimental results. A handy table at the beginning lists automotive industry standards governing electrical transients and fault conditions.

What you’ll learn:

• How to implement transient protection in automotive electrical systems using a four-switch buck- boost
• How to replace bulky LC filtering in automotive electrical systems with more compact active filtering and voltage regulation

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