IN Brief:
- L4983 targets continuous-conduction-mode boost PFC stages from several hundred watts to several kilowatts.
- L4983A operates at 65kHz, while L4983B raises the switching frequency to 130kHz.
- ST’s 350W evaluation design provides a regulated 400VDC output and reaches 97.4% peak efficiency.
STMicroelectronics has brought its L4983 family of continuous-conduction-mode power-factor-correction controllers into volume production, targeting switched-mode power supplies from several hundred watts to several kilowatts with two fixed switching-frequency options and an integrated protection set.
The controller is intended for boost PFC pre-regulators used at the front end of AC-powered equipment, where input current has to be shaped while a regulated high-voltage DC bus is generated for the downstream converter. ST identifies industrial and medical power supplies, servers, PCs, high-power lighting, and other equipment subject to harmonic-current requirements among the applications.
L4983 uses peak-current-mode control alongside ST’s proprietary multiplier emulator, which is intended to minimise input-current distortion across continuous and discontinuous conduction conditions. The architecture reduces the amount of external circuitry needed around the PFC control loop, although the final converter still depends heavily on the selected power switch, boost diode, current-sense network, magnetics, PCB layout, and compensation.
Two variants give designers different switching-frequency trade-offs. L4983A operates at 65kHz, while L4983B runs at 130kHz. Raising switching frequency can reduce the size of magnetic and filtering components, but generally increases switching loss and makes parasitic behaviour, thermal management, and layout more demanding.
The controller’s formal product documentation specifies a totem-pole output stage capable of sourcing 0.7A and sinking 1.5A, allowing it to drive external MOSFETs or IGBTs used in higher-power PFC stages. That figure supersedes a conflicting current rating published in ST’s same-day community announcement and is the value carried into the final package.
Protection functions include output overvoltage protection, overcurrent protection, feedback-loop failure detection, boost-inductor saturation protection, inrush-current monitoring, and soft start. Low-consumption and disable modes are included for designs expected to meet tighter standby and light-load efficiency requirements.
The choice of continuous-conduction operation reflects the intended power range. Keeping current flowing through the boost inductor throughout each switching cycle reduces peak-current stress compared with discontinuous approaches and is widely used in higher-power front ends, but it increases the importance of current-loop stability and predictable switching behaviour across input-voltage and load changes.
ST has also produced the EVL4983-350W demonstration board around the 65kHz variant. The board accepts a 90V to 264V AC input and provides a regulated 400VDC output at up to 350W, with the company specifying peak efficiency of 97.4%. Full-load total harmonic distortion is stated below 6%, rising to below 10% down to 15% load.
The evaluation platform gives the controller specification a more useful system reference. A front-end PFC stage has to meet harmonic limits while also controlling conducted emissions, thermal dissipation, transient behaviour, and conversion loss. Those constraints become progressively more significant as power rises because even small efficiency penalties translate into additional heat that has to be removed from the supply.
ST positions the controller for designs expected to comply with standards including EN 61000-3-2 and JEITA-MITI requirements. Compliance remains a property of the complete power supply rather than the controller itself, leaving magnetics, filtering, switching components, enclosure design, and PCB implementation to determine the final result.
The two L4983 variants are available in SO-8 packages and are listed by ST as active products in volume production. The development gives designers another CCM control option for established boost-PFC architectures, with the practical comparison likely to centre on achievable THD, efficiency, component count, and thermal performance at the intended power rating.
