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STMicroelectronics reveals flexible synchronous rectifier for efficient silicon or GaN converters

Helps simplify operation and save energy in industrial power supplies, portable-device chargers, and AC/DC adapters

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STMicroelectronics’ SRK1004 synchronous-rectifier controller eases the design and enhances the efficiency of converters built with silicon or GaN transistors, including industrial power supplies, portable-device chargers, and AC/DC adapters.


Capable of withstanding up to 190V at its sense input, the SRK1004 can be connected in a high-side or low-side configuration. Four variants let users avoid complex calculations by optimizing their design through device selection alone, selecting gate-drive voltage between 5.5V or 9V, with logic-level MOSFETs, standard MOSFETs, or GaN transistors. Suitable for noncomplementary active clamp, resonant, and quasi-resonant (QR) flyback topologies, the SRK1004 introduces a next-generation turn-off algorithm that simplifies operation and saves energy.


The features of this controller enable converters to provide a high output power rating within compact dimensions. The operating frequency can be up to 500kHz, allowing the use of small magnetic components as well as maximizing the benefits of wide-bandgap technology when using GaN transistors. The controller is fabricated in ST’s silicon-on-insulator (SOI) process, which ensures robust performance while permitting a tiny 2mm x 2mm DFN-6L package.


By operating with a supply voltage from 4V to 36V, the SRK1004 can be powered from a variety of standard industrial bus voltages. The wide input-voltage range also provides flexibility to adjust the step-down ratio for optimum efficiency. Also, with fast-acting short-circuit detection built-in, the controller helps build rugged and reliable equipment.


Of the four variants introduced, the SRK1004A and SRK1004B are configured for 5.5V gate-drive voltage and can be used with logic-level MOSFETs or GaN transistors. The SRK1004C and SRK1004D for 9V gate-drive voltage are suited to MOSFETs designed for standard gate-drive signals.


All variants of the SRK1004x synchronous rectification controllers are in production now and available from $0.45 for orders of 1000 units. The evaluation boards, EVLSRK1004A, EVLSRK1004B, EVLSRK1004C, and EVLSRK1004D, are also available to accelerate evaluation and design start with each type, at the budgetary price of $50.00.


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