LD9174T2PWM+QR Multi-mode Controller with Primary Side Regulation

In order to enhance the efficiency performance, the LD9174T2 integrates the multi-mode PWM controller, which consists of Quasi-Resonant (QR) PWM control for light load condition and Continue Conduction Mode (CCM) for heavy load condition. Moreover, the QR controller gains the system performance, but also brings the worse EMI capability, especially at boundary mode in heavy load. While the frequency swapping function of LD9174T2 can reduce the EMI emission of SMPS and helps the power circuit designers to simply deal with EMI filter and saves several component and developing time.

The LD9174T2 is implemented in SOP-8/DIP-8 package, and includes the comprehensive protection function, such as Over Load Protection (OLP), Over Voltage Protection (OVP), Secondary Diode Short Protection (SDSP) and internal Over Temperature Protection (OTP). Furthermore, the programmable brown-in/out protection is built-in.



  • PSR CCM+QR Multi-Mode Control.
  • Frequency Swapping for better EMI performance
  • Low Startup Current (<1.9mA)
  • Built-in load regulation compensation
  • 75 kHz PWM switching frequency at Low Line
  • Current mode control with cycle-by-cycle current limit
  • UVLO (Under Voltage Lock Out)
  • Bulk Over Voltage Protection
  • LEB (Leading-Edge Blanking) on CS pin
  • VCC & FB OVP (Over Voltage Protection)
  • SDSP (Secondary Diode Short Protection)
  • Adjustable Brown in/out on FB pin.
  • Low line ripple compensation on FB pin
  • Internal OTP (Over Temperature Protection)


  • Networking power supply
  • Lower Power AC/DC Adaptor