The Industry’s First Integrated Zero Cross Detection ICs

Sept 23rd, 2020

Contributes to minimizing standby power and improving reliability in home appliances

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

BM1ZxxxFJ Series

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.

Advantages of the BM1ZxxxFJ Series (Motor Application)

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.

Application Circuit Example: Washing Machine

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 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.

Availability: Now

Pricing: From 0.98USD/sample (excluding tax)

Application Examples

Home appliances equipped with motors such as air conditioners, washing machines, and vacuum cleaners

New Integrated Zero Cross Detection ICs Minimize Standby Power Consumption in Home Appliances

The BM1ZxxxFJ series supports both pulse and edge waveforms used in home appliance specifications, eliminating the need for software changes when replacing conventional zero cross detection circuits. 6 models are offered to ensure compatibility with a wide range of home appliances.

Part No.Delay TimeDC Motor Voltage MonitorCompatible CircuitsOutput Waveform*Withstand VoltageOperating Temp RangePackage
BM1Z001FJ NEW+300µs to +500µsNoneStandard rectification
Double rectification
Pulse600V-40ºC to +105ºCSOP-J7S
(4.9 x 6.00 x 1.65) [mm]
BM1Z002FJ NEWAdjustable via external resistor (-500µs, -200µs, 0µs, +200µsStandard rectification
BM1Z101FJ NEW+300µs to +500µsIncludedStandard rectification
Double rectification
(8.65 x 6.00 x 1.62) [mm]
BM1Z102FJ NEWAdjustable via external resistor (-500µs, -200µs, 0µs, +200µsStandard rectification

Supports Two Output Waveforms Depending on Specifications

Pulse Waveforms | Edge Waveforms

Evaluation Board

An integrated zero cross detection IC development board is available that integrates a power supply for driving ROHM’s integrated zero cross detection IC, facilitating device evaluation. This evaluation board is designed to simplify the decision-making process for designers when considering replacement of existing circuits using a photocoupler.

Sales Launch Date: Available Now
Online Distributors: Digi-Key, Mouser
Support Page:
(A user’s manual for the evaluation board is also available)

Evaluation Board Lineup

Eval Board Part NumberOnboard ProductFunctional Overview
BM1Z002FJ-EVK-001BM1Z002FJAC zero cross detection circuit (non-isolated)
BM1Z002FJ-EVK-002BM1Z002FJAC zero cross detection circuit (isolated)
BM1Z102FJ-EVK-001BM1Z102FJAC zero cross detection circuit + DC voltage monitor (non-siolated)


Zero Cross Point
A zero cross detection circuit is needed in home appliances that supply power from an AC outlet to detect the zero cross point (which is the 0V point of the AC waveform) in order to efficiently control both motors and MCUs. As a result, improving zero cross detection accuracy allows for even more efficient motor and MCU control. And when the motor is stopped, pulse control provides greater circuit safety by reliably stopping the voltage at 0V.

Zero Cross Point