The STMicroelectronics SRK1001 secondary-side synchronous-rectification controller introduces adaptive features that cut bill-of-materials costs, minimize circuit size, and simplify the design of power adapters, chargers, USB Power Delivery outlets, and lighting power supplies based on flyback topologies.
Designed for fast turn-on with minimum delay, and introducing innovative adaptive turn-off logic, the SRK1001 maximizes synchronous-rectification MOSFET conduction time for optimum efficiency with minimal switching losses. Unlike other controllers in the market, the SRK1001’s advanced design requires no external compensation circuitry to eliminate parasitic-inductance effects.
The SRK1001 also ensures superior converter efficiency at light loads, where synchronous rectification is no longer beneficial. The device automatically enters low-consumption mode when the MOSFET conduction period reaches the programmed minimum on time or when burst-mode operation of the primary controller is detected. The quiescent current in this mode is just 160 µA.
Versatility is another strength of the SRK1001, allowing use in quasi-resonant (QR) converters and mixed continuous/discontinuous current mode (CCM/DCM) fixed-frequency operation at up to 300 kHz. Robustness is assured, with programmable blanking time after both turn-on and turn-off to prevent noise from inducing spurious behavior.
Suitable for applications with output voltage up to 24 V, and capable of maintaining regulation down to 2 V output in CCM, the SRK1001 has a wide supply-voltage range of 4.5 V to 32 V. The output can sink up to 1 A and source up to 0.6 A to control the gate of the external N-channel synchronous-rectification MOSFET.
A dedicated Disable/Synchronization pin is provided to turn off the synchronous MOSFET and remotely trigger low-consumption mode, or to synchronize MOSFET turn-off during CCM operation. There is also drain-voltage sensing input capable of monitoring the external MOSFET drain-source voltage up to 185 V.
The SRK1001 is in production now, packaged as an 8-pin SO8 device, from $0.33 for orders of 1000 pieces.
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| SRK1001 adaptive synchronous rectification controller for flyback converter demonstration board with SR MOSFET. |
