Electric vehicle safety often means keeping drivers and passengers safe from electric shock hazards as charges traverse from batteries to the power train, lights and other components.
It’s a concern the industry takes seriously especially as high voltage vehicles proliferate and unwanted electromagnetic interference poses potential safety problems.
“EMI is increasingly a challenge with the proliferation of EV cars,” said Jeff Morroni, manager of power, isolation and motors at Kilby Labs, Texas Instruments' corporate research and development group. TI has a heavy emphasis in this area, he told reporters on a recent call. The auto industry is pushing for greater power density and high voltage in EVs to push more power into more areas of a vehicle.
Engineers speak of isolating power sources and power consuming devices from other parts of a vehicle, including the occupants. “Isolation is crucial because high voltage is critical,” Morroni added. As traction inverters move power from a 400 volt to 800 volt battery stack to alternating power that drives multi-phase motors and the vehicle’s drive train “we need to ensure the high voltages don’t make it to the chassis to prevent shock….You have to have a function to check that isolation.”
That function relies on semiconductors that “make sure there’s no damage to the isolation barrier,” Morroni said. “For that isolation check function we need something to withstand [conditions] with ultra high reliability across a wide temperature range.”
TI has been developing isolation technologies in integrated circuits for high voltage systems for two decades, he said. To make EVs safer, the company announced on Tuesday a new portfolio of sold-state relays to boost reliability. The company claimed its new relays are the smallest on the market to reduce the cost of powertrain and 800-volt battery management systems for vehicle manufacturers.
In addition, the new solid-state relays offer improvements over electromechanical relays. The solid-state relays can disconnect and connect loads with a single isolation barrier in less than 400 nanoseconds, TI claimed, which compares to milliseconds for electromechanical relays.
TI shared a graphic rendering of its new relays showing a greenish gold isolation barrier that depicts TI’s proprietary implementation of a silicon dioxide isolation barrier grown on wafers to create high quality isolation in the relays. In addition to the silicon dioxide, TI uses a thin polymer material and other materials in the relays.
The TI relays integrate power and sign transfer in a single chip while dropping out three components from their design to reduce the size and therefore cost.
The relays are tagged as the TPSI3050-Q1 and TPSI2140-Q1, with prices starting at $1.99 in 1,000-unit quantities. Evaluation modules are $49 each for the automotive load switch driver with reinforced isolation and the 1400-volt, 50 milliAmp isolated switch.
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