AN-6083 Datasheet, PDF (1/9 Pages) Fairchild Semiconductor – Highly Integrated, Dual-PWM Combination Controller

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AN-6083
Highly Integrated, Dual-PWM Combination Controller
Introduction
This application note shows the step-by-step process to
design a high-performance power supply which includes a
flyback converter for standby power and a single forward
converter for main power. Design considerations and
mathematical equations are presented, as well as guidelines
for a printed-circuit-board (PCB) layout.
The complete power-supply circuits shown in Figure 1
demonstrate the FAN6791’s ability to manage high-output
power while complying with international requirements
regarding AC line quality.
The FAN6791 is designed for the power supplies to achieve
high efficiency. The highly integrated FAN6791 dual-PWM
combination controller provides several features to enhance
the performance of converters. To minimize standby power
consumption, a proprietary green-mode function provides
off-time modulation to linearly decrease the switching
frequency at light-load conditions. With the internal high-
voltage startup circuitry, the power loss due to bleeding
resistors is also eliminated. The built-in synchronized slope
compensation of FAN6791 achieves stable peak-current-
mode control. The proprietary internal line compensation
ensures constant output-power limit.
© 2008 Fairchild Semiconductor Corporation
Rev. 1.0.2 • 3/11/09
Figure 1.
Typical Application
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