Applying Fairchild Power Switch (FPS) FSBH-series to Standby Auxiliary Power Supply

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AN-8024 Applying Fairchild Power Switch (FPSTM) FSBH-series to Standby Auxiliary Power Supply

The FSBH-series has built-in synchronized slope

1. Introduction compensation to achieve stable peak-current-mode control.

The proprietary external line compensation ensures constant

The highly integrated FSBH-series consists of an integrated

output power limit over a wide AC input voltage range, from

current mode Pulse Width Modulator (PWM) and an

90VAC to 264VAC and helps optimize the power stage.

avalanche-rugged 700V Sense FET. It is specifically designed for high-performance offline Switch-Mode Power Many protection functions, such as open-loop / overload Supplies (SMPS) with minimal external components. protection (OLP), over-voltage protection (OVP), brownout

protection, and over-temperature protection (OTP); are fully

The integrated PWM controller features include a

integrated into FSBH-series, which improves the SMPS

proprietary green-mode function that provides off-time

reliability without increasing the system cost.

modulation to linearly decrease the switching frequency at light-load conditions to minimize standby power This application note presents design consideration to apply consumption. The PWM controller is manufactured using FSBH-series to a standby auxiliary power supply with single the Bi CMOS process to further reduce power consumption. output. It covers designing the transformer, selecting the The green and burst modes function with a low operating components, feedback loop design, and design tips to current (2.5m A in green mode) to maximize the light load maximize efficiency. For multi-output applications, refer to efficiency so that the power supply can meet stringent Fairchild application note AN-4137. standby power regulations.

Figure 1. Typical Application Circuit

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