600 W Power Supply Schematic Diagram and Circuit Description

This Evaluation Board may employ high voltages so appropriate safety precautions should be used when operating this board. Replace components on the Evaluation Board only with those parts shown on the BOM. Contact an authorized Fairchild representative with any questions. This document describes the proposed solution for a 600W Power Supply using the FAN7601 Fairchild PWM Controller. The input voltage range is 185VRMS – 265VRMS and there is one DC output with 150V / 4A. This document contains the power supply specification, schematic, bill of materials and transformer documentation as well as typical operating characteristics. Mechanical Specification The board size is 94.0mm x 86.0mm x 48.0mm (L x W x H). Circuit Description The PSU is a continuous conduction mode (CCM) Buck converter using the FAN7601 Fairchild PWM controller (IC4), the FCP11N60 SuperFET™ (Q1) and the FOD2741A Optically Isolated Error Amplifier (IC2). The optically isolated error amplifier combines the functionality of a standard KA431 reference and an optocoupler. The main Buck converter consists of the switching element FCP11N60 SuperFET™ (Q1), the choke integrated in T1 (W1), freewheeling STEALTH™ diode ISL9R860P2 (D5) and the output capacitor C5. The current sense signal is generated using the sense resistors R15, R26 and R27. It is then filtered by R16 and C7. R24,C15, R23, D7 and Q5 form an leading edge blanking network which processes the current sense signal before it is fed in Pin 2 of IC4. Q6 and R25 are for slope compensation due to a duty cycle greater than 50%. The switching element FCP11N60 SuperFET™ (Q1) is driven from the output of IC4 Pin 6. Q3, Q4 and R18 form a gate-driver circuit for Q1. Electrical Characteristics The high value of the leakage inductance results from the usage of HF litzwire for the main choke ( W1). The advantage of the HF litzwire is a better thermal behaviour for the choke due to a lower AC resistance for high frequencies.

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