Tuesday, April 23, 2024

High Efficiency Synchronous Rectification Controllers

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  • The new device launch by STMicroelectronics also enables low power consumption and effective power management
  • Offers affordable and smaller-footprint for battery chargers and USB power outlets

STMicroelectronics has introduced the SRK1000A and the SRK1000B secondary-side synchronous-rectification (SR) controllers for flyback converters, which feature high efficiency and low power consumption. At the same time, it also offers a new, more affordable and smaller-footprint option for battery chargers, quick chargers, adaptors and USB power-delivery outlets.

These devices have been designed for fast turn-on and turn-off with minimum delay. They maximise synchronous-rectification MOSFET conduction time and minimise the effects of parasitic inductance in the circuit without the need to add external components, thus leading to greatly improved system efficiency and a reduced bill of materials.

Faster blanking time

The SRK1000A and SRK1000B are both able to manage a wide range of flyback controllers including quasi-resonant (QR) and mixed CCM/DCM fixed frequency operation up to 300kHz. Both devices allow programmable blanking time after turn-on (TON), via resistor selection, to prevent noise from inducing spurious behaviour. The SRK1000A has a 2μs fixed blanking time and the SRK1000B has 3μs fixed blanking time, both after turn-off (TOFF).

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Effective power management

The devices offer an efficient low power mode at light load and enter a low-consumption sleep mode when synchronous rectification is no longer beneficial. This is managed either by detecting primary-side controller burst-mode operation or when the SR MOSFET conduction becomes lower than the programmed minimum TON. The device quiescent current in this low consumption mode is only 160μA.

Suitable for applications with output voltage up to 19V and capable of maintaining regulation down to 2V output in CCM, the SRK1000A and SRK1000B have a wide supply-voltage range of 4.5V to 32V, with a drain-source voltage rating of 100V. The output can sink up to 1A and source up to 0.6A to control the gate of the external N-channel synchronous-rectification MOSFET.

The SRK1000A are SRK1000B are both available in a 2.9mm x 2.8mm 6-pin SOT23-6L package.


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