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TI’s New Isolated Gate Driver Aims to Boost Efficiency in EV Powertrains

October 16, 2020 by Antonio Anzaldua Jr.

The new isolated gate driver for high-powered SiC and GaN power devices is said to reduce PCB space, eliminate external components, and increase power efficiency in EVs.

A vehicle’s powertrain gives a driver the feeling of raw horsepower. Because the powertrain houses the main components that generate power, the architecture requires highly-efficient power devices made of SiC and GaN materials

For instance, using SiC MOSFETs provides the powertrain system with a high thermal conductivity attribute that allows for the system to operate at high temperatures over standard silicon. Also, using GaN MOSFETs in DC/DC converters reduces capacitor and magnetics while maintaining high switching capabilities.

Powertrains experience a high volume of noise and vibration, which means capacitive isolation is the preferred method to cope with these design challenges. Capacitive isolation is implemented through isolated gate drivers that are able to handle high data rates and mitigate excess noise throughout the system.

 

Isolated Gate Drivers in Automotive Powertrains

Isolated gate drivers work well for wide bandgap solutions because they handle high voltage applications and fast switching functionalities from 100 kilohertz to megahertz. And thanks to these gate drivers, designers are able to reduce the system’s cost, weight, and PCB footprint by eliminating external components such as pulse transformers and discrete isolators.

 

TI’s isolated gate driver evaluation module

TI’s isolated gate driver evaluation module is able to provide powertrain diagnostics to designers to design for minimal faults within the system. Image used courtesy of Texas Instruments

 

TI has introduced an isolated gate driver to drive high-powered silicon carbide and gallium-nitride power devices. The company claims that this device reduces PCB space, eliminates external components, and increases power efficiency in electric vehicle (EV) systems.

 

On- and Off-Board Charging Subsystems

The electronic system within HEVs and EVs is split into two main parts in terms of power supply and storage: on- and off-board charging subsystems.

Off-board charging handles high kilowatts and requires an elegant battery management system. For the onboard charging stations, this subsystem handles the lower kilowatt power transfer and can add significant weight to the vehicle.

This is where isolated gate drivers are essential.

 

TI Releases New Isolated Gate Drivers

By reducing footprint, weight, and external discrete components, the UCC5870-Q1 isolated gate driver is able to provide functional safety diagnostics, help the powertrain system, and maximize the power density by 50%, according to TI.

 

Block diagram of the UCC5870-Q1

Block diagram of the UCC5870-Q1. Image used courtesy of Texas Instruments
 

The company says this model of drivers is able to convert pulse-width modulation signals from the microcontroller into gate pulses for the power switches to turn on and off.

 

Design to Cost: The Demand for Cost-Friendly EVs

In order to get more consumers switched over to renewable energy-fueled vehicles, affordability needs to be upfront. Manufacturers are looking for new devices that can help engineers design low-cost systems in order to present an affordable vehicle. 

TI’s recent release was joined by another manufacturer, Silicon Labs, which recently launched its own isolated gate drivers aimed at automotive applications. The Si823Hx/825xx family is a set of gate drivers very similar to TI’s model in regards to providing fast switching, high noise immunity, and low latency (low delays prior to data transfer).

 

Si8252x

Application of the Si8252x configured as a HS/LS driver. Image used courtesy of Silicon Labs
 

The difference is the power it can handle. Silicon Labs’ isolated gate driver offers a 4 A sink/source output while TI’s model delivers 15 A output, which ultimately defines the control of the direct current flow in a load. Another difference between isolated drivers is the fact that Silicon Labs’ solution is geared toward silicon-based solutions, not SiC or GaN MOSFETs.

If the isolated gate drivers have a propagation delay higher than 150ns and sink/source output lower than 15A, then the Silicon Labs drivers might be a good option for motor control, lighting control, solar, and industrial inversion systems. For HEV/EV applications, the TI UCC5870-Q1 allows engineers to design simple, lightweight systems.

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