ROHM, a leading global semiconductor manufacturer, has introduced the step-down DC/DC converter BD9227F, specifically designed for DC fan motor power supplies in refrigerators. This innovative IC is tailored to meet the growing demand for efficiency, miniaturization, and intelligent control in modern electronics.
The BD9227F is the first power supply IC in the industry capable of adjusting the output voltage of a DC fan motor based on the duty cycle of the PWM signal generated by an MCU. Unlike traditional discrete component setups, this IC enables precise control, high-frequency operation, and circuit optimization through advanced analog design. As a result, large inductors and output capacitors can be significantly reduced in size, cutting the component footprint by approximately 75% compared to conventional designs. Additionally, the power conversion efficiency increases by 19% at an output current of 300 mA, making it ideal for applications requiring both performance and compactness.
Mass production of the BD9227F began in October 2016, with a monthly output of 100,000 units. The sample price is 500 yen per unit (excluding tax). The manufacturing process involves ROHM Hamamatsu Co., Ltd. in Hamamatsu City, Japan, for the initial stages, and ROHM Electronics Philippines, Inc. in the Philippines for later processes.
In recent years, the electronics industry has been driven by three key trends: intelligence, miniaturization, and high efficiency. With nearly 50% of global electricity consumption used for motor-driven systems, there's a growing need for more efficient, compact, and intelligent motor solutions. The BD9227F aligns perfectly with these demands, offering a powerful and space-saving alternative to traditional DC fan motor power supplies.

Previously, DC fan motor power supplies in appliances like refrigerators relied on discrete components, which limited precision control and required bulky inductors and capacitors. This often led to larger board footprints and lower efficiency. The BD9227F overcomes these challenges by integrating advanced control features into a single IC, enabling high-frequency operation and significant space savings.

1. High-Precision Motor Speed Control
Traditional discrete structures often struggle with linear control of motor speed due to non-linear relationships between PWM duty cycles and output voltages. The BD9227F addresses this by linearly regulating the output voltage based on the PWM signal from the MCU, ensuring accurate and stable motor speed control.

2. 75% Reduction in Component Footprint
One of the main limitations of discrete components is their inability to support high PWM frequencies, resulting in the need for large inductors and capacitors. The BD9227F operates at 1 MHz, allowing for smaller peripheral components and a 75% reduction in overall footprint, making it ideal for space-constrained designs.

3. High Efficiency Across Full Load Range
Compared to conventional structures, the BD9227F delivers higher efficiency across all load conditions. At 300 mA, it improves power conversion efficiency by approximately 19%, with even greater gains at higher loads. This makes it an excellent choice for energy-conscious applications.
4. 100% Duty Cycle Output
By incorporating a high-side PMOS transistor, the BD9227F can generate a 100% duty cycle output, which is challenging to achieve with standard ICs. This feature enhances control flexibility and performance in various operating conditions.

*1) PWM (Pulse Width Modulation), Duty (Duty Cycle)
PWM is a technique used to regulate output voltage by varying the on-time and off-time within each cycle. The duty cycle represents the proportion of time the signal is on during one cycle. A higher duty cycle results in a higher output voltage.
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