58 the need to reduce EMI and achieve higher efficiency. Selecting isolated components that are designed to meet all of these needs at IC level helps to facilitate a seamless transition to fully reinforced compliance at system level. Battery management system The need for current isolation is highlighted by a distributed BMS with multiple packs of cells, each with a remote BMS control unit. In this configuration, measurements on cells within the battery modules are made by the remote BMS units and reported over a series connection to the BMS master controller. Current measurement for the full stack is made using a shunt resistor at the bottom of the stack and an isolated current amplifier. The BMS controller can calculate the voltage of the full stack by adding the voltages of the modules, but a redundant safety-check, isolated-voltage measurement of the full stack can be made using a resistor divider and isolatedvoltage sense amp, such as the Si893x. The entire system can be monitored and controlled via an automotive bus, such as CAN, which is isolated with a digital isolator. Gate driver The gate driver is a common example of galvanic isolation, separating the control signals sent to high-power transistors from the high voltage. This isolation can be handled by layers of silicon oxide in the chip or by coupled wires in a package. Innovations in the isolated gate driver can help vehicle performance. By varying the gate-drive strength in steps between 20 A and 5 A in real time, designers can improve system efficiency with a gate driver by as much as 2% by minimising SiC switching power losses. This can result in up to seven more miles of EV driving range per battery charge. For an EV user who charges their vehicle three times per week, that could mean more than 1,000 additional miles per year. The isolated SPI programmability, and integrated monitoring and protection features in a device such as the UCC5880-Q1 from TI can reduce design complexity, as well as external component costs. Engineers can further reduce components and quickly prototype a more efficient traction inverter system using a reference design with SiC high-voltage transistors. This customisable, tested design includes the UCC5880-Q1, a bias-supply power module, real-time control MCUs and high-precision sensing. “Designers of high-voltage applications like traction inverters face a unique set of challenges to optimise system efficiency and reliability in a small space,” says Wenjia Liu, product line manager for high-power drivers at TI. “Not only does this new, isolated gate driver help enable engineers to maximise driving range, but it also integrates safety features to reduce external components and design complexity. It can be easily paired with other high-voltage power-conversion products, such as our UCC14141-Q1 isolated bias supply module, to improve power density and help engineers reach the highest levels of traction inverter performance.” Inductive isolation The development of hybrid and EVs means the voltage range for batteries has risen to 400 V or even 800 V. Devices with an integrated, highvoltage switch and internal isolation enable compact power-supply design for these new vehicles, and provide significant benefits. Inductive isolation within the package eliminates the need for an optocoupler (also known as optical isolators) as there is a high-voltage switch, a primary side controller and a secondary side controller. The isolation greatly reduces component count and increases performance uniformity across production. These benefits simplify design and can increase reliability. With the move to high-voltage systems, ensuring an electrical fault will not cause shock, harm or injury to the end-user is critical. Power Integrations has developed a method of evaluating package safety isolation, where an artificially induced catastrophic failure of the power switch is used to cause package damage in the vicinity of the high-voltage switch. Post-failure isolation tests demonstrate that the integrity of the isolation barrier within the semiconductor device is maintained, says Thomas Anthony Capobianco at Power Integrations. Safety standards apply to both system designs and integrated circuits. Specific standards are also used for qualifying automotive products. The UL Standard for Safety for Optical Isolators, UL 1577, covers Deep insight | Isolation technologies January/February 2025 | E-Mobility Engineering Low to high galvanic isolation (Image courtesy of Texas Instruments)
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