Zero cross detection ICs for home appliances

01-10-2020 | ROHM Semiconductor | Semiconductors

ROHM Semiconductor’s BM1ZxxxFJ integrated zero cross detection IC series is optimised for home appliances such as vacuum cleaners, washing machines, and air conditioners.


Many appliances need a zero cross detection circuit for detecting the 0V point (zero cross point) of the AC waveform to deliver efficient control of both motors and MCUs. Nevertheless, in terms of power consumption, conventional zero cross detection circuits employ a photocoupler that accounts for almost half of the standby power of the entire system.


In response, the company created the first integrated zero cross detection solution for power supplies in the home appliance sector. The integrated zero cross detection IC gives designers a turn-key zero cross detector with no requirement for a complex design employing discrete components. Further, this integrated solution does not utilise a photo-coupler typically employed in other solutions, and, therefore, it further decreases standby current consumption and increases long-term reliability.


The series reduces standby power consumption of the zero cross circuit to only 0.01W while constantly powering the system. Also, the error in delay time (which changes depending on the AC voltage) that exists with conventional photocoupler-equipped zero cross detection circuits is limited to ±50µs or less. This provides for the efficient drive of motors – even with the different AC supply voltages utilised in various countries and regions – as well as MCUs. At the same time, eradicating the requirement for a photocoupler contributes to better application reliability by decreasing risks related to age-based degradation.


Both pulse and edge waveforms employed in-home appliance specifications are supported by the series, removing the necessity for software changes when replacing conventional zero cross detection circuits. The company provides six models to ensure compatibility with a wide range of home appliances.






An integrated zero cross detection IC development board is offered that combines a power supply for driving the company's integrated zero cross detection IC, enabling device evaluation. This evaluation board is intended to simplify the decision-making process for designers when evaluating replacement of existing circuits utilising a photocoupler.

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