Maxim MAX5974宽输入电压PoE电源解决方案
Maxim公司的MAX5974系列是宽输入电压峰值电流模式正向PWM控制器,不需要光耦合器,MAX5974A/MAX5974C适用于通用的电信电压输入,而MAX5974B/ MAX5974D输入电压可低至10.5V.器件内部有1%的误差放大器,100kHz到600kHz可编程频率,可编程频率抖动以降低EMI和采用扩频工作,主要用在PoE IEEE® 802.3af/at标准的以太网供电设备,有源钳位正向DC/DC转换器,IP电话,无线接入节点和安监照相机等.本文介绍了MAX5974系列主要特性, MAX5974A/B方框图, MAX5974C/D方框图以及典型应用电路图,以及采用MAX5974A/B的12V/2A Class 4 PD参考设计主要特性和电路图.
The MAX5974_ provide control for wide-input-voltage, active-clamped, current-mode PWM, forward converters in Power-over-Ethernet (PoE) powered device (PD) applications.
The MAX5974A/MAX5974C are well-suited for universal or telecom input range, while the MAX5974B/ MAX5974D also accommodate low input voltage down to 10.5V.
The devices include several features to enhance supply efficiency. The AUX driver recycles magnetizing current instead of wasting it in a dissipative clamp circuit.
Programmable dead time between the AUX and main driver allows for zero-voltage switching (ZVS). Under lightload conditions, the devices reduce the switching frequency(frequency foldback) to reduce switching losses.
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