**LT3791EFE-1#TRPBF: A High-Performance Isolated Flyback Controller with Power Factor Correction**

In the realm of power electronics, achieving high efficiency, robust isolation, and a near-unity power factor is a significant challenge, especially for AC/DC converter applications. The **LT3791EFE-1#TRPBF** from Analog Devices stands out as a premier solution, integrating a sophisticated isolated flyback controller with active power factor correction (PFC) into a single, compact package. This device is engineered to meet the demanding requirements of modern power supplies, ranging from industrial equipment to LED lighting systems.

At its core, the LT3791EFE-1 is a **current-mode switching controller** that operates in a critical conduction mode (CrM). This mode of operation is pivotal for achieving high power factor and high efficiency across a wide load range. By controlling the flyback MOSFET to ensure the inductor current discharges to zero on every switching cycle (valley switching), it minimizes switching losses and reduces electromagnetic interference (EMI), a common hurdle in power supply design.

A key feature of this IC is its **ability to generate a stable, isolated output without the need for a third transformer winding or an opto-coupler**. It accomplishes this through its unique isolated feedback mechanism, which samples the output voltage directly from the primary-side flyback waveform during the MOSFET off-time. This innovative approach, known as **primary-side regulation (PSR)**, significantly enhances system reliability by eliminating components that are traditionally failure-prone. This makes the design both more robust and simpler.

The integrated power factor correction circuitry is another major advantage. The controller forces the input current to track the input voltage sinusoid, ensuring a **power factor often exceeding 0.97**. This is crucial for complying with international energy standards (like EN61000-3-2) and for maximizing the real power drawn from the mains, reducing losses in the distribution system.

Furthermore, the device offers comprehensive protection features, bolstering the resilience of the end application. It includes **programmable overvoltage protection (OVP), undervoltage lockout (UVLO), and open-loop fault detection**. These safeguards ensure the system operates within safe boundaries, protecting both the power supply itself and the load it serves.

Housed in a thermally enhanced 16-Lead TSSOP exposed-pad package (FE), the **LT3791EFE-1#TRPBF** ensures excellent thermal performance, which is vital for maintaining reliability in high-power-density designs. Its wide input voltage range and flexibility in output voltage configuration make it an exceptionally versatile choice for designers.

**ICGOODFIND**: The LT3791EFE-1#TRPBF is a highly integrated and robust controller that simplifies the design of high-performance, isolated power supplies. By merging active PFC with a primary-side regulated flyback topology, it delivers exceptional efficiency, reliability, and power quality, making it an superior choice for a vast array of applications.

**Keywords**: Power Factor Correction (PFC), Isolated Flyback Converter, Primary-Side Regulation (PSR), Critical Conduction Mode (CrM), Current-Mode Controller.