Dynamic Envelope Tracking in a power supply for the automotive market

March 08, 2016 // By Steve Taranovich
During a visit with Intersil recently, I met with Niall Lyne, Product Line Director for Automotive and Ed Kohler, Marketing Manager for Automotive-Grade Power Solutions. Once in a while, I see a glimpse of ingenuity in a design that I had never seen before which pleasantly surprises me. It was at this meeting that I experienced such an innovation.

The Problem to be solved: How to efficiently and effectively handle any and all available automotive voltages of 24V/36V and 48V (usually more the high end cars) in automotive power systems in a single design.


The Intersil solution: The ISL78227 and the ISL78229 (with PMBus). These two 55V two-phase synchronous boost controllers with integrated high-side and low-side MOSFET drivers are a robust solution with the unique use of Dynamic Envelope Tracking (Intersil claims to be the first in the industry and I have not seen anything else like this). More on this later.


Operating from a 12V battery supply, these devices boost the 12V battery supply to output voltages of 24V, 36V or 48V for premium 200W to 800W trunk [boot] audio amplifiers, start-stop systems, and headlamp LED strings.


These devices enable a modular design for systems requiring power and thermal scalability. They support wide input and output ranges of 5V to 55V and deliver greater than 95% efficiency to reduce power loss and improve upon heat dissipation. The architecture interleaves two controllers for a four-phase application which in turn doubles the output power and reduces input/output ripple. This will enable designers to use smaller capacitors to save board space and lower their bill of materials cost.


Since the automotive environment is a harsh one, there are numerous protection features to keep the ICs operating under just about any condition. Intersil designers have implemented a soft-on function which ensures smooth transition from discontinuous-conduction mode (DCM) to continuous-conduction mode (CCM) after completing a soft-start. This keeps the power supply safe under all start-up conditions. The CCM operates at 1 MHz, single phase which is above the AM radio band and will not interfere with reception.


Envelope Tracking

I am very familiar with the technique of Envelope Tracking in base station and handset Power Amplifiers. The Intersil designers realised that by tracking the input and changing the