AN-6208

APPLICATION NOTE

© 2010 Fairchild Semiconductor Corporation

www.fairchildsemi.com

Rev. 1.0.1 • 3/10/11

7

Design Example

The following example is a 12V/300W single output power

supply with LLC resonant converter topology. As Figure 19

shows, the FAN7621 controller is used for the LLC resonant

converter. The integrated CCM PFC controller FAN6982 is

used for PFC stage.

The key system parameters are listed in Table 1 and the Bill

of Materials (BOM) is summarized in Table 2.

The two-level PFC output voltage function of FAN6982 is

used where the typical PFC output voltage is 390V. The

PFC output voltage is reduced to 360V for low-line and

light-load condition to improve efficiency of the PFC stage.

Table 1.

System Specification

Input Voltage Range

PFC Output

PFC Controller

FAN6982

Main power Controller

FAN7621

Output Voltage (Vo)

12V

Output Power (Po)

300W

PFC Switching Frequency

65kHz

LLC resonant converter Switching Frequency

60~140kHz

voltage rating is 100V. 27k

Low-Frequency Mode setting.

Figure 19.Complete Circuit Diagram