Synchronous-rectification controller reduces power adapter circuit size
Features to reduce the bill of materials cost, minimise the size of the circuit and simplify the design of power adapters, chargers, USB Power Delivery outlets are included in the SRK1001 secondary side synchronous-rectification controller.
The device from STMicroelectronics can also be used in lighting power supplies based on flyback topologies.
It is designed for fast turn-on with minimum delay and adaptive turn-off logic. The SRK1001 is claimed to maximise synchronous-rectification MOSFET conduction time for minimal switching losses. According to STMicroelectronics, unlike other controllers in the market, the SRK1001’s design requires no external compensation circuitry to eliminate parasitic-inductance effects.
The synchronous-rectification controller 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 microA.
The SRK1001 is versatile, allowing its use in quasi-resonant (QR) converters and mixed continuous/discontinuous current mode (CCM/DCM) fixed-frequency operation at up to 300kHz. It is also robust, with programmable blanking time after both turn-on and turn-off to prevent noise from inducing spurious behaviour.
It can be used for applications with output voltage up to 24V and is capable of maintaining regulation down to 2V output in CCM. It has a wide supply-voltage range of 4.5 to 32V. The output can sink up to 1.0A and source up to 0.6A to control the gate of the external n-channel synchronous-rectification MOSFET.
A dedicated disable/synchronisation pin can be used to turn off the synchronous MOSFET and remotely trigger low-consumption mode, or to synchronise MOSFET turn-off during CCM operation. There is also drain-voltage sensing input capable of monitoring the external MOSFET drain-source voltage up to 185V.
The SRK1001 is in production now and available in an eight-pin SO8 package.
