PowerZeroTM Multi-Mode Flyback Controller


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The RT7789B series is an enhanced high-efficiency multi-mode PWM flyback controller, incorporating Richtek's proprietary PowerZeroTM and SmartJitterTM technology. The innovative PowerZeroTM technology, featuring an integrated HV device, provides an excellent green power solution, while the SmartJitterTM technology can reduce EMI emissions of a switch-mode power supply in green mode as well as eliminate the output ripple due to frequency jittering. In addition, the RT7789B series features a multi-mode control scheme, operating from the continuous-conduction mode (CCM) to the discontinuous-conduction mode (DCM) with valley switching, to achieve high efficiency and optimal performance.

The RT7789B is a current-mode PWM controller for flyback converters, integrated with comprehensive and programmable protection features, which include brown-in/brown-out protection, VDD over-voltage protection (VDD OVP), output over-voltage and under-voltage protection (Output OVP and UVP), secondary rectifier short-circuit protection (SRSP), and external over-temperature protection (External OTP). For the constant output power regulation, a resistor connected to CS pin can be used to achieve an accurate line compensation across the universal input voltage range. With these features, the RT7789B enables one to accomplish a cost-effective and compact design for a wide range of AC-DC conversion applications.


  • Switching AC-DC Adapter
  • NB Adapter
  • Printer Adapter
Key Spec.
Status Active
Feedback Regulation Mode SSR
Switching Frequency_Normal (kHz) 65
Switching Frequency_Peak (kHz) 130
Peak load Application Yes
HV Start-up Yes(w/i X-CAP discharge)
CCM/Valley Multi-mode Yes
Programmable Burst/Green-mode No
Brown-in/out Yes (AC Side)
External OTP Yes
UVLO ON (V) 18
UVLO OFF (V) 6.5
VDD OVP (V) 34.5
Features Current Mode Control;Cycle-by-Cycle Current Limit;OCP;OVP;SCP;UVP
Package Type SOP-8
  • Proprietary PowerZeroTM Technology
    ► Integrating a 700V Start-up Device
    ► Brown-In/Brown-Out Protection
  • Proprietary SmartJitterTM Technology
    ► Reducing EMI Emissions of SMPS
    ► Eliminating Frequency-Jittering-Induced Output Ripple
  • Operating in Continuous-Conduction Mode (CCM), Discontinuous-Conduction Mode (DCM), and DCM with Valley Switching
  • Accurate Over-Current Protection (OCP)
  • Programmable Line Compensation
  • Programmable Output OVP and UVP
  • Programmable External OTP
  • Driver Capability : 300mA/-300mA
  • High Noise Immunity
  • RoHS Compliant and Halogen Free