Zero-cross detection IC optimized for appliance power supplies

ROHM announces the availability of BM1ZxxxFJ, an integrated zero cross detection IC series, optimized for home appliances such as vacuum cleaners, washing machines, and air conditioners.

The rising demand for smart appliances and IoT applications has added communication functionality (i.e. Wi-Fi) to home appliances. As it is necessary for such devices to always be ON to maintain communication, manufacturers are required to reduce standby power consumption even more to around 0.5W. This calls for lower standby power consumption by the motor and power supply blocks along with innovative new technologies.

Many appliances require a zero cross detection circuit for detecting the 0V point (zero cross point) of the AC waveform in order to provide efficient control of both motors and MCUs. However, in terms of power consumption, conventional zero cross detection circuits utilize a photocoupler that accounts for nearly half of the standby power of the entire system.

In response, ROHM developed the first integrated zero cross detection solution for power supplies in the home appliance sector. The integrated zero cross detection IC provides designers a turn-key zero cross detector without the need for a complex design using discrete components. Additionally, this integrated solution does not use a photo-coupler typically used in other solutions, and, therefore, it further reduces standby current consumption and increases long-term reliability. Not surprisingly, this feature has been well identified by appliances manufactures and already considered in the qualification phase.

The BM1ZxxxFJ series reduces standby power consumption of the zero cross circuit to just 0.01W while continuously powering the system. What’s more, the error in delay time (which varies depending on the AC voltage) that exists with conventional photocoupler-equipped zero cross detection circuits is limited to ±50µs or less. This allows for the efficient drive of motors – even with the different AC supply voltages used in various countries and regions – as well as MCUs (which is difficult to achieve using conventional zero cross detection circuits). At the same time, eliminating the need for a photocoupler contributes to greater application reliability by reducing risks related to age-based degradation.

Key Features

Developing a zero cross detection circuit without a photocoupler contributes to improved reliability and reduced power consumption in a variety of applications, including home appliances.

1. Breakthrough photocoupler-less zero cross detection circuit design minimizes application standby power consumption

Conventional zero cross detection circuits commonly utilize a photocoupler and transistor that accounts for nearly half of the standby power consumption of the entire application. This time, after analyzing hundreds of power supply patterns in different environments, ROHM was able to achieve an IC capable of detecting the zero cross without a photocoupler.

Along with reducing the number of parts, the new design delivers a standby power consumption close to zero (0.01W). And in motor applications it is possible to further decrease component count along with standby power consumption by eliminating the motor input voltage detection circuit.

2. Contributes to improved reliability and efficiency in home appliances in a variety of countries and regions

Using a photocoupler involves risks that include performance degradation due to the deterioration in luminous intensity over time. Eliminating the photocoupler not only reduces this failure risk but also limits the delay time error, which can vary depending on the AC voltage, to ±50μs or less. This makes it possible to efficiently drive motors even with the different supply voltages (100-230V) used in various countries – as well as MCUs, which is difficult or impossible to achieve using conventional zero cross detection circuits.

3. Easily replace conventional zero cross detection circuits

ROHM’s new series supports the waveforms (pulse/edge) and circuit topologies (standard rectification/double rectification) utilized in conventional zero cross detection circuits, allowing users to easily replace standard zero cross detection circuits equipped with a photocoupler without requiring software changes.

4. Integrated voltage clamp function protects the downstream MCU

The BM1ZxxxFJ series is compatible with input voltages up to 600V and performs voltage division to the output below the maximum rated voltage of MCU and drive standard MCUs up to 5V. A voltage clamp function is also included that ensures the input voltage does not exceed 4.8V, protecting the MCU even when abnormal voltages are generated in high voltage drive applications such as air conditioners.

Pricing: From 0.98USD/sample (excluding tax)