MAXREFDES1206 是一款以太網供電 (PoE) 受電設備和有源鉗位正向轉換器，可在 39V 至 57V 電源電壓下提供高達 1A 的電流和 24V 的電壓。它專為受電設備 (PD) 系統而設計，符合 PoE 系統中的 IEEE? 802.3af/at 標準。MAXREFDES1206 說明了使用有源鉗位正向拓撲生成隔離輸出的技術。本文檔介紹了如何使用 MAX5969B 和 MAX5974C 設計 PD，以在 39V 至 57V 輸入電壓下生成 24V 電壓。上表是設計規范的概述。以太網供電 (PoE) 是一種允許網絡電纜通過供電設備 (PSE) 或中跨向受電設備 (PD) 供電的技術。與傳統的供電方法相比，它具有許多優勢。PoE 允許將電力和數據結合起來，無需改變交流電源基礎設施。非電工也可以安裝它。 PoE 是一種智能系統，其設計將保護功能放在首位，可防止過載、功率不足和安裝錯誤，同時具有簡單的可擴展性和可靠性。MAX5974C 可控制以太網供電 (PoE) 受電設備 (PD) 應用中寬輸入電壓、有源鉗位、電流模式 PWM、正向轉換器。 MAX5974C 非常適合通用或電信輸入范圍。主要特點可編程開關頻率：100kHz 至 600kHz可編程頻率抖動，降低 EMI，擴頻操作可編程死區時間，PWM 軟啟動，電流斜率補償可編程前饋最大占空比箝位，80% 最大限值頻率折返，實現高效率輕載操作內部自舉 UVLO，具有大滯后100μA (典型值) 啟動電源電流快速逐周期峰值電流限制，5V，35ns 典型傳輸延遲115ns 電流檢測內部前沿消隱帶打嗝模式的輸出短路保護反向電流限制，防止由于反向電流導致變壓器飽和

The MAXREFDES1206 is a Power over Ethernet (PoE) powered device and active clamp forward converter that delivers up to 1A at 24V from a 39V to 57V supply voltage. It is designed for powered device (PD) systems to comply with the IEEE® 802.3af/at standard in a PoE system. The MAXREFDES1206 illustrates techniques using the active clamp forward topology to generate isolated output. This document explains how the MAX5969B and MAX5974C can be used to design the PD to generate 24V from 39V to 57V input voltage. Table above is an overview of the design specification.

Power over Ethernet (PoE) is a technology that allows network cables to deliver power to a powered device (PD) through power-sourcing equipment (PSE) or midspan. It has many advantages over traditional methods of deliver-ing power. PoE allows power and data to be combined, removing the need to alter the AC mains infrastructure. It can be installed by non-electricians. PoE is an intelligent system designed with protection at the forefront, preventing overload, underpowering, and installation errors, while allowing simple scalability and reliability.

The MAX5974C provides control for wide-input-voltage, active-clamped, current-mode PWM, forward converters in Power-over-Ethernet (PoE) powered device (PD) appli-cations. The MAX5974C is highly suitable for universal or telecom input ranges.
Key Features

Programmable Switching Frequency from 100kHz to 600kHz
Programmable Frequency Dithering for Low-EMI, Spread-Spectrum Operation
Programmable Dead Time, PWM Soft-Start, Current Slope Compensation
Programmable Feed-Forward Maximum Duty-Cycle Clamp, 80% Maximum Limit
Frequency Foldback for High-Efficiency Light-Load Operation
Internal Bootstrap UVLO with Large Hysteresis
100μA (typ) Startup Supply Current
Fast Cycle-by-Cycle Peak Current-Limit, of 5V and35ns Typical Propagation Delay
115ns Current-Sense Internal Leading-Edge Blanking
Output Short-Circuit Protection with Hiccup Mode
Reverse Current Limit to Prevent Transformer Saturation Due to Reverse Current