New Industry Products

High-Efficiency AC-DC Converter IC with Integrated PFC Control Function

January 21, 2014 by Jeff Shepard

ROHM Semiconductor has announced the development of a high-efficiency ac-dc converter that integrates PFC (Power Factor Correction) and QR (Quasi-Resonant) controllers into a single package, making it suited for 100W-class equipment such as TVs and industrial power supplies. The BM1C001F is the first to incorporate an ON/OFF setting function and new PFC output control method within the PFC controller. This improves efficiency during light loads and significantly reduces standby power. Power supplies utilizing this IC are ensured compliance with Energy Star 6.0, the latest international energy standard.

In addition, the 2-controller-in-one design reduces the number of external parts, contributing to power supply miniaturization. In recent years, in the face of mounting power supply shortages comes a need for greater efficiency to improve energy savings in electronic devices of all types. But in order to control harmonics in equipment over 75W, which can be harmful to other devices, a PFC controller is required, which may have a negative effect on efficiency.

Also, to reduce design and evaluation loads while enabling easy repair, power supply adapters are currently progressing in 100W-class equipment such as large LCD TVs. However, conventional solutions combine an ac-dc converter with built-in QR controller with a separate PFC circuit, which can present problems regarding board space and power supply size. In response, ROHM was the first to integrate a special function that allows for flexible ON/OFF setting of the PFC controller. This improves conversion efficiency during light loads while reducing standby power consumption.

In addition, a new proprietary PFC output control method is included in the PFC controller for boost converter operation, significantly increasing efficiency - particularly in 100Vac systems. For example, integrating this IC in a 100W class power supply will result in 89% efficiency at 100Vac and 89.5% efficiency at 230Vac, clearing the latest Energy Star standard (6.0) stipulating at least 88% efficiency. Also, layout optimization makes it possible to integrate the PFC and QR controllers in a single package, reducing parts count by 20% compared with conventional solutions.

According to Rohm, this is industry’s first PFC controller ON/OFF setting function improves conversion efficiency at light loads and reduces standby power consumption. It monitors the load power on the secondary side and switches the PFC controller ON/OFF, including in the load region where PFC is not required (below 75W), improving power supply conversion efficiency. And using this IC in 100W class power supplies results in a standby power of less than 85mW at 100Vac and 190mW at 230Vac, clearing the latest Energy Star standard (6.0) requiring 210mW or less.

The new proprietary PFC output control method ensures high efficiency worldwide. Although the input ac voltage will vary depending on country/region, conventional PFC ICs provide a constant output voltage, possibly resulting in higher switching loss. In response, ROHM developed a new PFC control method that delivers an output voltage optimized to the input AC voltage. This can improve conversion efficiency in 100W-class power supplies by 1-2% compared to fixed PFC output solutions in 100Vac systems.

With QR and PFC controllers integrated into a single package, the number of external parts significantly reduced. The single-package design with internal PFC and QR controllers eliminates a number of components in the common design sections, reducing parts count by 20% compared with conventional configuration utilizing an external PFC circuit.