UCC38502NG4

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Power Factor Correction (PFC) is a technique used in electrical systems to reduce the reactive power components of the system and increase its power factor. UCC38502NG4 is a synchronous buck PFC controller that allows precise control of the PFC power stage of offline power supplies and other power conversion applications. This article explores the application fields and the working principle of UCC38502NG4.

Application Fields of UCC38502NG4

Applications of UCC38502NG4 include:

• Power supplies for domestic appliances (TVs, monitors, printers, etc.)
• General purpose AC/DC and DC/DC converters (external power supply for PC or laptop, etc.)
• LED drivers for lighting applications
• Chargers for industrial or consumer products (mobile phone, electric bicycle, etc.)
• Consumer products with embedded power supplies (routers, modems, etc.)
• Industrial applications (Robotic, automation equipment, etc.)

Working Principle of UCC38502NG4

UCC38502NG4 is a voltage-mode search type synchronous buck PFC controller. The controller implements a two-stage concept having an initial "search" phase followed by the PFC operating phase.

The search phase helps the UCC38502NG4 to start in any kind of input voltage level and achieve the rated power factor relatively quickly. First, the controller will identify any input voltage levels below 50V by checking the "Startup Voltage Threshold." If the voltage is below 50V, the controller will enter a low threshold search voltage mode to ensure that the controller starts correctly. In this phase, the controller will set the switching node at a reference voltage of 25V. If the voltage is above 50V, the controller will wait for a "ramp-up" signal and adjust its switching node voltage accordingly. Once the ramp-up signal is received, the controller will enter the PFC working phase.

In the PFC working phase, the controller will adjust the current of the input voltage source by modulating the duty-cycle of the switching node. This will ensure that the power factor of the system remains constant. The controller handles all of the modulation functions and can compensate for any voltage variations of the input source. The controller automatically adjusts the active energy before it reaches the critical value and then reduces the duty-cycle to keep the system in its rated power factor. A programmable over-current protection ensures that the system is protected from any short-circuits or overload conditions.

Conclusion

UCC38502NG4 provides a versatile solution for the PFC stage in power converters. This device is suitable for applications such as power supplies, LED drivers, chargers, and industrial applications. By using its two-stage concept and duty cycle modulation, the device can quickly achieve the rated power factor and keep the system stable. Additionally, the UCC38502NG4 provides programmable over-current protection to ensure that the system is protected from any short-circuits or overload conditions.

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