SRK1000 Synchronous Rectification Controller

By STMicroelectronics 148

SRK1000 Synchronous Rectification Controller

STMicroelectronics' SRK1000 controller is intended for secondary side synchronous rectification (SR) in flyback converters, suitable for operation in QR and mixed CCM/DCM fixed frequency circuits. It provides a high-current gate-drive output capable of driving N-channel MOSFETs.

The control scheme of this IC is such that the SR MOSFET is switched on as soon as current starts flowing through its body diode, and it is then switched off as current approaches zero. The fast turn-on with minimum delay and the innovative adaptive turn-off logic allow maximizing the conduction time of the SR MOSFET and eliminate the effect of parasitic inductance in the circuit.

The SRK1000 features a programmable blanking time after turn-on, and a fixed minimum blanking time after turn-off is also available.

The device enters low consumption mode when it detects primary controller burst-mode operation, or when the SR MOSFET conduction becomes lower than the minimum time programmed. In this way, converter efficiency improves at light load where synchronous rectification is no longer beneficial.

After the converter restarts switching or the IC detects that the current conduction in the rectifiers has increased 20% above the minimum time programmed value, the IC exits low-consumption mode and resumes switching operation.


  • Fast turn-on with minimum delay and innovative adaptive turn-off logic
  • Operates in QR and mixed CCM/DCM fixed frequency operation
  • CC regulation down to 2 V output
  • Programmable min TON (blanking time after turn-on) and fixed min TOFF (blanking time after turn-off)
  • Automatic sleep mode
  • Innovative adaptive turn-off logic


  • High efficiency with SR MOSFET conduction maximized
  • Robust design and extreme flexibility to manage all operation conditions
  • Guarantee SR MOSFET switching with very low output voltage
  • Higher flexibility with respect to different application requirements
  • Very low quiescent current in low consumption mode (160 µA)
  • Minimal BOM, no additional circuit needed for stray inductance compensation