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STMicroelectronics SRK1001 Adaptive Synchronous Flyback Controller for Power Simplification

May 24, 2020 by Misha Khan

Keeping in view the increasing demand for simplified circuit designs for engineers, STMicroelectronics has launched an adaptive synchronous flyback controller, IC SRK1001 and it is based on secondary-side synchronous rectification.

It is specially designed with adaptive features that reduce circuit size and simplify the design of lighting power supplies, chargers, power adapters, and USB Power Delivery outlets.


Design and Construction

Packaged as an 8-pin SO8 device, the SRK1001 flyback controller is designed for side synchronous rectification (SR) found in flyback converters.

Being operated in QR and mixed CCM/DCM fixed frequency operation up to 300 kHz, this new adaptive synchronous SRK1001 controller is suitably designed for engineers. 

It is designed with minimum delay for fast turn-on-and-off logic. The controller is embedded with a MOSFET which enables conduction with minimal switching losses. Engineers would not need an external compensation circuitry with SRK1001 controller for mitigating parasitic-inductance effects. This is due to the controller not requiring external circuitry. 


SRK1001 Flyback Controller

A product image of the SRK1001 flyback controller demonstration board. Image Credit: STMicroelectronics.


Features and Specifications

Programmable blanking time after turn on and turn off is featured with the SRK1001 controller. This helps the controller prevent noise that comes from inducing spurious behavior.

This controller is designed to ensure efficiency at light loads. At this point, synchronous rectification is of no benefit. When either the MOSFET conduction period reaches the programmed minimum on time or there is the detection of burst mode operation of the primary controller, the SRK1001 controller goes into its low consumption mode automatically.

A quiescent current of 160µA is present during the low consumption mode. It is supported by CC regulation operation down to 2V output. The controller is operating at a wide VCC voltage range of 3.7 V to 32 V. The DIS pin is used for low consumption mode entry. 


Engineering Applications

Engineers can operate this device in applications of both fixed frequency (FF) and quasi-resonant (QR). The board for the controller is suitable for QR applications. Engineers looking for using the board in FF applications, they require a 100 pF capacitor that needs to be added.

The blanking is fixed by 120 kΩ resistor present on the TON pin. SRK1001 synchronous Flyback controller is used in AC/DC adaptors, battery chargers, quick chargers, industrial SMPS, and USB power delivery (profile 4). 

Therefore, the SRK1001 controller helps reduce circuit complexities and used for power simplification. The adaptive features of this controller reduce the size of the circuit and for easier design efforts. 

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