This article describes the proposed solution for a 200 W Power Supply using the FSFR2100 Fairchild Power Switch (FPS). The input voltage range is 90 – 265 VRMS and there are six outputs with 0.7A / 48V max. each. The board consists of a high power factor pre-regulator based on the FAN6961 voltage mode PFC controller and an isolated DC/DC converter based on a resonant LLC topology. This document contains the power supply specification, schematic, bill of materials and transformer documentation.

Schematic Diagram

The power supply consists of a high power factor pre-regulator, a DC/DC converter and three current sources. D94 - 97 act as a rectifier that supplies positive half-waves to the following boost-converter. C914, LF1, C95 and C915 form an EMI filter. The PFC is based on IC91, the voltage mode PFC controller FAN6961. At start-up of the application, C96 is charged by R93a and R3b to the start voltage of IC91. As soon as the IC begins to operate, current is drawn and C96 starts to discharge. Since the circuit is switching now, the voltage across the secondary winding of TR91a supplies current via R94, C913 and D91. Since the latter voltage varies with the input voltage it is clamped with D93 to a suitable level. IC91 generates the gate voltage for the boost switch Q91. The on-time of Q91 is (almost) constant during one half-wave of the power line voltage while the off-time is variable and determined by the de-magnetization of TR91a & TR91b. The latter is determined by detection of the zero crossing of the voltage at the pin 'ZCD' of IC91. The output voltage of 405V is fed back via the divider R910a/b and R911. C97 determines the crossover frequency that has to be less than half the line frequency in order to get a high power factor.

PCB Layout

Bill of Materials

Source: http://www.fairchildsemi.com