New Photorelay Built for 400-V Automotive Battery Systems

Electric vehicles (EVs) and hybrid EVs (HEVs) continue to grow in popularity amid calls to reduce vehicle CO₂ emissions in efforts to slow global warming. But to achieve wider adoption of EVs, improved charge times and a longer cruising range are essential. Both require more efficient operation of battery systems. On that front, battery-management systems (BMS) realize efficient system operation by monitoring the battery charge status.

A BMS that must handle high voltages typically includes electrically insulated photorelays. These semiconductor relays, which consist of an LED optically coupled to a MOSFET, are used mainly as replacements for signal relays. Having no movable contacts, photorelays are known to have better long-term reliability than mechanical relays.

What is a Photorelay?

In photorelays, the primary (control) side and the secondary (switch) side are electrically isolated. Switches connected directly to the AC line and switches between equipment that differ in ground potential can be controlled through insulating barriers. The insulation between the battery and the vehicle body is essential for the safe use of high-voltage batteries.

Photorelays commonly used in battery systems must have a withstand voltage of approximately twice the system voltage. Given this, an output withstand voltage of over 800 V is necessary for a 400-V system.

Addressing that issue, Toshiba Electronic Devices & Storage Corp.’s new TLX9152M is an automotive photorelay with an output withstand voltage of 900 V (min) that. The photorelay is claimed to be highly suitable for application in 400-V automotive systems.

The TLX9152M comprises an infrared emitting diode optically coupled to a photo-MOSFET in a SO16L-T package, which is widely used in various high-voltage photorelays like Toshiba's TLX9160T with an output voltage of 1500 V. Use of this package facilitates common circuit board pattern design. The coupler incorporates a high-voltage MOSFET between output terminals, making it suitable for battery-related control applications.

TLX9160T Photorelay Features

• Output withstand voltage: V_OFF = 900 V (minimum)
• Normally open (1-Form-A) element
• Avalanche current rating: I_AV = 0.6 mA
• High isolation voltage: 5000 V rms (minimum)
• AEC-Q101-compliant
• Conforms to IEC 60664-1 international standard

Volume shipments are immediately available.