STMicroelectronics has announced a power-factor correction controller for the front-end of ac-dc PSUs from 600W to 6kW.

STNRGPF02-PFC-controller

Called STNRGPF02, it implements a two-channel interleaved boost topology as well as in-rush current limiting.

Operation is fixed-frequency continuous-conduction mode (CCM) with average current-mode control.

“A blend of analogue and digital control combines a hardware analogue PI [proportional-integral] compensator in the inner current loop and a digital PI controller in the outer voltage loop, ensuring fast response,” according to ST. “Cascaded control for the voltage and current loops regulates the output voltage by acting on the total average inductor current.”

The digital part is configured using the company’s eDesignSuite tool after typing in the desired specifications. The tool also picks external components and generates a schematic, bill of materials and binary object code ready to download via the IC’s serial communication port – in operation, the same serial port allows monitoring of PFC parameters.

“System integration is greater than digital solutions that require a separate DSP or microcontroller,” claimed ST.

In-rush current limiting is through an external resistor (not shown) in series with the necessary external input bridge rectifier. The chip includes means to control an external electromechanical relay or semiconductor switch to short this resistor once turn-on is complete.

A related chip, STNRGPF12, includes a more sophisticated in-rush controller that works in conjunction with a pair of thyristors in a modified input bridge, steadily altering their firing angle until power-up is complete.

Both controllers support programmable phase shedding in the boost converter, load feed-forward and burst mode to maximise efficiency at different loads.

Built-in protection include thermal, over-current and over-voltage. Fault and OK status indicators are provided.

Packaging is TSSOP38.

An evaluation board for the STNRGPF02 is available (STEVAL-IPFC02V1) that combines analogue cycle-by-cycle current regulation with digital control.

Applications are foreseen with industrial motors, air conditioners, domestic appliance, commercial appliances, cellular base-stations, telecom infrastructure, data centre equipment and uninterruptible power supplies (UPSs).