ROHM developed a DC/DC converter "BD9227F" that realizes DC fan motor speed control. ICized the conventional discrete structure.

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ROHM, the world's leading semiconductor manufacturer, has developed the step-down DC/DC converter " BD9227F ", which is the most suitable DC fan motor power supply for refrigerators.

The " BD9227F " is the industry's first power supply IC that can control the output voltage of the DC fan motor based on the Duty*1 of the PWM signal generated by the MCU. Compared with the conventional discrete component structure, it not only realizes high-precision control, but also realizes high-frequency driving and circuit optimization of 1MHz by using the analog circuit design technology of the IC. As a result, peripheral components such as large coils and output capacitors can be miniaturized, and the occupied area of ​​components is reduced by about 75% compared with the conventional structure, and the power conversion efficiency is increased by 19% (at an output current of 300 mA), so that the device equipped with the DC fan motor is used. Achieve high precision and miniaturization, contributing to improved power conversion efficiency.

This product has been mass-produced in October 2016 with a monthly production capacity of 100,000 units (sample price 500 yen / piece: excluding tax). The production base of the previous process is ROHM Hamamatsu Co., Ltd. (Hamamatsu City, Japan), and the later process is ROHM Electronics Philippines, Inc. (Philippines).

In recent years, "intelligence", "miniaturization", and "high efficiency" have become the three major issues in the electronics industry, and the corresponding market demand is also growing. In addition, according to the survey, nearly 50% of the global electricity demand is used for motor drive. . Therefore, in order to design the product and protect the environment, it is required to realize a more intelligent, compact and efficient motor drive.

Up to now, the power supply of the DC fan motor mounted in appliances such as refrigerators is mostly a discrete component structure, which makes it difficult to perform high-precision control and high-frequency drive, and requires a large coil and an output capacitor. Components, which lead to difficult areas such as large footprints.

1. Linear control through output voltage

High precision of motor speed

When the conventional discrete structure is used, the output voltage is not linear with respect to the duty of the pulse input to the PWM terminal, so it is difficult to accurately control the rotational speed of the motor.

" BD9227F " linearly controls the output voltage according to the Duty of the PWM signal generated by the MCU, thereby achieving high-precision control of the DC fan motor speed.

2. Parts area reduced by 75%

A major problem with the discrete structure in the past is that it is difficult to increase the frequency of the PWM signal input by the MCU, and the peripheral components require large coils and output capacitors, resulting in a large footprint.

The "BD9227F" realizes high-frequency driving at an operating frequency of 1 MHz by frequency control in the IC, and miniaturizes peripheral components such as large coils and output capacitors, resulting in a 75% reduction in footprint.

3. High efficiency in the full load field

Compared with the discrete structure, the "BD9227F" achieves high efficiency in the full load field. For example, at a load of 300 mA, the power conversion efficiency can be increased by about 19%. The gap is greater at high loads.

4. Can generate 100% Duty

By mounting a high-side PMOS, it is possible to generate an output voltage of 100% Duty that is difficult to achieve with an IC.

*1) PWM (Pulse Width Modulation), Duty (Duty Cycle)

The PWM is a method of controlling the output voltage by repeatedly switching the ON time and the OFF time in one cycle. Duty is equivalent to the ON time ratio of one cycle of PWM. The higher the ratio, the higher the output voltage.