Quantcast
Industry Cortex

Document Brief

www.fairchildsemi.com...

LED Application Design Guide Using BCM Power Factor Correction (PFC) Controller for 100W Lighting System...

1. Introduction...

This application note presents practical step-by-step design considerations for a Boundary-Conduction-Mode (BCM) Power-Factor-Correction (PFC) converter employing Fairchild PFC controller, FL7930. It includes designing the inductor and Zero-Current-Detection (ZCD) circuit, selecting the components, and closing the control loop. The design procedure is verified through an experimental 140W prototype converter. Unlike the Continuous Conduction Mode (CCM) technique often used at this power level, BCM offers inherent zero-current switching of the boost diodes (no reverse-recovery losses), which permits the use of lessexpensive diodes without sacrificing efficiency. The FL3930B provides an additional OVP pin that can be used to shut down the boost power stage when output voltage exceeds the OVP level due to damaged resistors connected at the INV pin. The FL7930C provides a PFCready pin can be used to trigger other power stages when PFC output voltage reaches the proper level (with hysteresis). This signal can be used as the VCC trigger signal for another power stage controller after PFC stage or be transferred to the secondary side to synchronize the operation with PFC voltage condition. This simplifies the external circuit around the PFC controller and saves BOM cost. The internal proprietary logic for detecting input voltage improves the stability of PFC operation. Together with the maximum switching frequency clamping at 300kHz, FL7930 can limit inductor current to within predesigned ranges at one or two cycles of the AC-inputabsent test to simulate a sudden blackout. Due to the startup-without-overshoot design, audible noise from repetitive OVP triggering is eliminated. Protection functions include output over-voltage, over-current, openfeedback, and under-voltage lockout. An Excel -based design tool is available with this application note and the design result is shown with the calculation results as an example....

Figure 1. Typical Application Circuit...

2011 Fairchild Semiconductor Corporation Rev. 1.0.0 3/24/11...

2. Operation Principle of BCM Boost PFC Converter...

The most widely used operation modes for the boost converter are Continuous Conduction Mode (CCM) and Boundary Conduction Mode (BCM). These two descriptive names refer to the current flowing through the energy stor...

Document Keywords

LED Application Design Guide Using BCM Power Factor Correction (PFC) Controller for 100W Lighting System an an an 9731

Sponsored Products

About Fairchild Semiconductor Corp.

Fairchild Semi specializes in high performance ICs that optimize energy efficiency and enable mobile connectivity in a wide range of applications. As a global provider of semiconductor solutions our products...

Contact

207-775-8100, 800-341-0392 (toll free)
Fax: 207-761-6020

sponsored links