STMicroelectronics L4984D Current-Mode PFC Controller
STMicroelectronics L4984D Current-Mode PFC Controller operates with line-modulated fixed-off-time (LM-FOT) control. A proprietary LM-FOT modulator allows fixed-frequency operation for boost PFC converters as long as they are operated in CCM (continuous conduction mode). The chip comes in a 10-pin SO package and offers a low-cost solution for CCM-operated boost PFC pre-regulators in EN61000-3-2 and JEIDA-MITI compliant applications in a power range that spans from a few hundred W to 1KW and above. The highly linear multiplier includes a special circuit that is able to reduce the crossover distortion of the AC input current and allows wide-range maintenance operation with a reasonably low THD, even over a large load range.
The output voltage is controlled utilizing a voltage-mode error amplifier and an accurate (1% at Tj = +25°C) internal voltage reference. Loop stability is optimized by the voltage feedforward function (1/V2 correction), which in this IC uses a proprietary technique that also significantly improves line transient response in the case of mains drops and surges (“bi-directional”). The device features low consumption and includes a disable function suitable for IC remote on/off. These features allow use in applications that also comply with the latest energy-saving requirements (Blue Angel, ENERGY STAR®, Energy 2000, etc.).
In addition to overvoltage protection able to keep the output voltage under control during transient conditions, the IC from STMicroelectronics is also provided with protection against feedback loop failures or erroneous settings. Other onboard protection functions allow brownout conditions and boost inductor saturation to be safely handled. Soft-start limits peak current and extends off-time to prevent flux runaway in the initial cycles. The totem pole output stage, capable of 600mA source and 800mA sink current, is suitable for big MOSFETs or IGBT drives.
Features
- Line-modulated fixed-off-time (LM-FOT) control of CCM-operated PFC pre-regulators
- Proprietary LM-FOT modulator for nearly fixed-frequency operation
- Proprietary multiplier design for minimum THD of AC input current
- Fast “bi-directional” input voltage feedforward (1/V2 correction)
- Accurate adjustable output overvoltage protection
- Protection against feedback loop failure (latched shutdown)
- Inductor saturation protection
- AC brownout detection
- Digital leading-edge blanking on current sense
- Soft-start
- 1% (at Tj = +25°C) internal reference voltage
- -600/+800mA totem pole gate driver with active pull-down during UVLO and voltage clamp
- SSOP10 package
Applications
- PFC Pre-Regulators
- IEC61000-3-2 and JEIDA-MITI compliant SMPS over 1KW
- Desktop PC, server, webserver
Block Diagram
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