Toshiba Shrinks Automotive Photorelay for High-Voltage Battery Systems

As electric vehicles become more advanced, the electronics inside their battery packs are under increasing pressure. Relays that once only had to switch modest voltages are now expected to handle kilovolt levels, all while fitting into tighter spaces and meeting tougher safety rules. Toshiba’s new TLX9161T photorelay is built with that challenge in mind, combining high breakdown voltage with a smaller footprint to suit next-generation battery systems.

Compact Package, Built for High Voltage

The TLX9161T arrives in Toshiba’s SO12L-T package, offering a 1500V withstand rating and sub-millisecond switching. Those figures make it a good match for monitoring and protection tasks in battery management and fuel-cell systems, where solid-state devices are steadily replacing mechanical relays.

Compared with its predecessor, the TLX9160T, the new device trims about a quarter of the package size. Importantly, it keeps the same pin pitch and layout, so existing PCB designs can be reused. For engineers already working with crowded battery modules, that means more freedom to save space without redesign headaches.

Isolation and Low Power Draw

Inside, the relay uses an infrared LED driving a photo-MOSFET. This optical coupling provides a strong electrical barrier between the control and switch sides, rated up to 5000Vrms. In practice, that isolation helps systems ride out the wide voltage swings seen in stacked EV batteries.

Power consumption is also kept in check. A trigger current of just 3mA reduces demand on the control circuitry, while the off-state current is only 100nA. When inactive, the device barely sips power, a useful trait in automotive systems where standby drain is closely watched.

Safety by Design

Safety standards in automotive design leave little margin. Here, the TLX9161T uses a resin with a Comparative Tracking Index above 600, placing it in the highest insulation category under IEC60664-1. Creepage and clearance are maintained at 8mm or greater, ensuring reliable separation even at elevated voltages. The relay is also rated across –40°C to +125°C and carries AEC-Q101 Grade 1 qualification, so it’s ready for the harshest automotive environments.

Why It Matters

EVs are steadily pushing toward higher voltages and greater integration, and every component in the system has to keep pace. Relays may be simple in function, but they play a central role in safety and reliability. By combining 1500V withstand capability with a smaller footprint and proven automotive compliance, Toshiba’s TLX9161T gives engineers a practical option for building compact, efficient, and dependable battery systems.

Learn more and read the original announcement here.