Rohm Develops Zero Cross Detection IC for White Goods
Standby power 0.01W, delay error less than ±50µs
Capable of driving 5V MCU, with voltage clamp function


As the era of home IoT arrives, communication functions such as Wi-Fi are being installed in white goods.

To maintain communication connection, constant power is required. Home appliance manufacturers want to reduce the standby power of their appliances to around 0.5W, but the standby power of the motor and power supply has already been significantly improved, so another method was needed.

ROHM announced on the 14th that it has developed the 'BM1ZxxxFJ series' of zero cross detection ICs for white goods that can detect zero cross without a photocoupler.

Most white goods require a circuit to detect the zero cross point, or 0V point, of the AC waveform for motor and MCU control.

Existing zero cross detection circuits typically use photocouplers, and their power consumption accounts for about half of the total standby power of the application. Photocouplers also have concerns about failure, such as performance degradation due to aging of luminous intensity.

The BM1ZxxxFJ series enables zero cross detection without a photocoupler, reducing the standby power of the zero cross detection circuit to 0.01 W when always on. The delay time error that occurs depending on the AC voltage when the application is running is reduced to ±50 µs or less.

The BM1ZxxxFJ series with a withstand voltage of 600 V can drive MCUs with a maximum rating of 5 V. It also features a voltage clamp function that prevents the input voltage from exceeding 4.8 V to protect the MCU when the input voltage is high.

We have a lineup that can support each circuit (normal/voltage multiplication) and waveform (pulse/edge) used in existing zero cross detection circuits, so no software change is required even if existing products are replaced with the new series.

ROHM has been selling a zero cross detection IC evaluation board (BM1Z002FJ-EVK-00x) with a power supply installed through Chip 1 Stop and Corestaff since June.