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[原创] ST PM8804以太网加电PD转换器4V 8A解决方案

关键词:电源管理 以太网加电 PoE PWM IEEE802.3.af/at/bt

时间:2019-05-16 11:24:24       来源:龙8手机登录--官方网站

ST公司的PM8804以太网加电PD转换器是PWM控制器(峰值电流模式),集成了设计用于PoE和电信中等功率智能和有效48V应用所有需要的电路.PD转换器具有5V 8A输出,具有同步反激,与IEEE802.3bt标准兼容.PM8804具有可编程振荡器,用于开关频率,可调斜率补偿,双互补的具有可编死区时间,可编软起动,软关断和可编电流检测消隐时间(高达200ns)的低边驱动器.其内部高压线性稳压器具有典型20mA输出电流,使得器件能以最少化外接元件来起动.输入工作电压高达75V,栅极驱动器1A峰值电流,最大占空比80%,CTL引脚上的内部上拉电阻可连接光耦合器,工作电流消耗小于1.5mA,主要用于PoE加电设备如IP电话,WLAN接入点和网络照相机以及电信电源.本文介绍了PM8804主要特性,内部框图,应用电路图和以太网加电评估板STEVAL-POE002V1主要特性,电路图和材料清单.

The PM8804 is a PWM controller that integrates all the circuitry required to design a smart and efficient 48 V converter for PoE and telecom mid-power applications.

It features a programmable oscillator for the switching frequency, adjustable slopecompensation, dual complementary low-side drivers with programmable dead time,programmable soft-start, soft turn off and a programmable current sense blanking time.

An internal high-voltage linear regulator with a typical 20 mA output current allows the device to start up with a minimum of external components.Complementary 1 A peak gate drivers make possible to implement high power topologies,while when the second drives is not used, like with simple low power flyback converters, it can be turned off.

The device embeds a set of protections that enables the design of a self-protected converterwith the scope to eliminate the risk of catastrophic failure at system level.The device targets high efficiency conversion at wide range of load.

PM8804主要特性:

 PWM peak current mode controller
 Input operating voltage up to 75 V
 Internal high-voltage start up regulator with 20mA current capability
 Current sense with programmable blankingtime up to 200 ns
 Programmable fixed frequency up to 1 MHz
 Soft-start up with settable time
 Soft turn off (optionally disabled)
 Dual low-side complementary gate drivers
 Programmable dead time from 10 to 200 nsbetween GATE1 and GATE2
 Gate drivers have 1 A peak capability
 GATE2 optionally turned off for reducedconsumption
 80% maximum duty cycle with internal slopecompensation
 Internal pull-up resistor on CTL pin enables theoptocoupler connection
 Operating current consumption < 1.5 mA
 Embedded protections:
– Severe overcurrent protection with latchafter 4 events
– Delayed overload protection with automaticrestart
– Feedback disconnection (OV) protection onVC
– Thermal shutdown
 High efficiency topologies:
– Flyback, forward
– Flyback with synchronous rectification
– Flyback with active clamp
– Forward with active clamp

PM8804应用:

 PoE powered devices such as IP phones,WLAN access points and network cameras
 Telecom power supplies

图1. PM8804内部框图

图2.采用PM8804控制器的有源正向转换器应用电路图

以太网加电评估板STEVAL-POE002V1:PD转换器5V 8A输出同步反激, IEEE802.3bt标准兼容

The STEVAL-POE002V1 power device evaluation board is equipped with a DC-DC converter stage, managed by the PM8804 controller, which provides 40 W (5 V-8 A) on the output.

The DC-DC converter stage is based on the fixed frequency Flyback topology with a secondary synchronous rectification managed by the controller via gate driver transformer.

The evaluation board embeds also the PM8805 controller, dedicated to the Ethernet interface (compliant with the Standard IEEE802.3.af/at/bt) and to the full active bridge rectification.

The STEVAL-POE002V1 power device evaluation board is equipped with a DC-DC converter stage, managed by the PM8804 controller, which provides 40 W (5 V-8 A)on the output.

The DC-DC converter stage is based on the fixed frequency Flyback topology with a secondary synchronous rectification managed by the controller via gate driver transformer.

The evaluation board embeds also the PM8805 controller, dedicated to the Ethernet interface (compliant with the Standard IEEE802.3.af/at/bt) and to the full active bridge rectification.

评估板STEVAL-POE002V1主要特性:

• Based on PM8804 and PM8805
• IEEE 802.3bt compliant PD interface
• Works with power supplied from Ethernet LAN cables or local auxiliary sources
• Line input voltage range: 40 to 60 VDC
• Output voltage: 5 VDC ± 2.5%
• Output current: 8 A
• Peak-to-peak output ripple: < 50 mV
• DC-DC full load efficiency: > 91%
• Overall full load efficiency: > 90%
• Transient response ΔV pk-pk 100% to 50% load step ≈ 700mV
• Switching frequency ≈ 280 KHz

图3.评估板STEVAL-POE002V1外形图

图4.评估板STEVAL-POE002V1电路图(1)

图5.评估板STEVAL-POE002V1电路图(2)

图6.评估板STEVAL-POE002V1电路图(3)

图7.评估板STEVAL-POE002V1电路图(4)
评估板STEVAL-POE002V1材料清单:




详情请见:
https://www.st.com/content/ccc/resource/technical/layouts_and_diagrams/schematic_pack/group0/fd/29/
63/12/3f/3e/46/11/STEVAL-POE002V1_SCHEMATIC/files/steval-poe002v1_schematic.pdf/jcr:content/translations/en.steval-poe002v1_schematic.pdf

https://www.st.com/content/ccc/resource/technical/document/bill_of_materials/group0/23/20/65/6b/ee/b2/4e/be/STEVAL-POE002V1_BOM/files/steval-poe002v1_bom.pdf/jcr:content/translations/en.steval-poe002v1_bom.pdf
pm8804.pdf
en.steval-poe002v1_bom.pdf
en.steval-poe002v1_schematic.pdf

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