Photocoupler enables carmakers to replace mechanical relays for high-voltage isolation

Toshiba Electronics Europe GmbH has announced a new automotive-compliant photorelay designed for 400V battery-related control systems. The TLX9152M features a minimum output withstand voltage (VOFF) of 900V to support applications such as battery and fuel-cell control, as well as BMS in EV where it can be employed in circuits to monitor voltages, monitor for mechanical relays sticking and to detect ground faults.

The device consists of an IR emitting diode optically coupled to a photo-MOSFET. Its fast reaction (TON/TOFF) time of 1ms (max) is a critical decisive specification for design engineers. The trigger current is 3mA (max), which reduces system energy consumption. Moreover, the off-state current (IOFF) of this device is 100nA (max) at ambient temperature, meaning that it draws minimal power while inactive. The IR LED has a 20mA (max) forward current (IF), while its photodetection element has a 50mA on-state current (ION).

For a 400V automotive battery system, the test voltage for the withstand voltage test (Hi-Pot test) in the set is 1800V, and the same output withstand voltage as the test voltage can be attained by using two of the products. Also, the device is housed in a SO16L-T package (the company’s package code 11-10N1A), widely employed for high-voltage photorelays. Its existing product, the TLX9160T, housed in the same package, provides an output withstand voltage of 1500V in 800V battery systems when the test voltage is set at 2600V. Therefore, this combination permits a 400V and 800V battery system to share the board.

The device is supplied in an SO16L-T package, a modified version of the SO16L featuring only 12 pins. It has a space-saving 10.3mm x 10mm x 2.45mm form factor that helps ease system integration. When employed in 1kV systems, this normally-open (1-Form-A) device exhibits 5mm creepage and clearance distances on its output side, ensuring that effective isolation is maintained. The device can operate across a wide temperature range from -40C to +125C and is fully qualified according to the AEC-Q101 standard for automotive applications.