Current Limited DC-DC Controll
abstract: usb powered devices require a regulated supply. unfortunately, the usb bus voltage can vary from 4v to 9v. configuring the max668 boost controller into step-up/step-down topology can generate a current-limited regulated supply.
universal serial bus (usb) is a popular way to connect pcs and consumer devices. it is simple and inexpensive and can connect multiple external peripherals simultaneously. as mobile devices add more functionality such as text messaging, web surfing, information storage and music playing, the need to communicate with a pc is increasing. many of the mobile devices today offer a usb interface native in the device. the sole purpose is to provide a connection for data communication. the device may be self powered (e.g., through a wall adapter) or draw the power from the usb bus.
the mobile devices are typically expected to connect to a powered usb hub. a usb device can have its own power source (e.g. batteries or a wall plug) or draw the power from the usb bus. a powered usb host can provide up to 500ma current. using the power supplied by usb can be tricky because the voltage to a usb powered device may be as low as 4.35v, when cable and connector drops are considered, or as high as 5.5v. if the device is to operate with a voltage adapter for a source it may see input voltages as high as 9v. in order to accommodate these various scenarios, a step-up/step-down dc-dc topology works well. the input and output specifications for a controller/converter are summarized in table 1.
table 1. power supply requirements for usb compatible portable device parameter requirement
input voltage vin 4v to 9v
input current iin 500ma (±5%) max.
output power pout 2.4w typical
output voltage vout 6v (±5%) typical
output load current iout 400ma max.
regulation min. vout =5.5v at iout = 200ma
sepic to 6v with input current limitingthis step-up/step-down supply is used to power a li+ battery charger. since the charger itself will have a drop in voltage across it, the output voltage was set to 6v. the single-ended primary inductance converter shown in figure 1 is ideal for this application. this buck-boost topology is needed since the input voltage can vary from values below the output voltage to values greater than the output voltage (table 1). the max668 boost controller is adapted to sepic topology (figure 1).
figure 1. sepic power supply for usb compatible device.
the current limit resistor r4 (figure 1) is used to limit the input current to a maximum of 500ma as specified in table 1. the input current limit also ensures short-circuit protection ensuring usb compliance even under output fault conditions. when the output exceeds the input current limit the output voltage will reduce and restrict the input current to 500ma as shown in figure 2. note the extra inductor required in this topology as compared to a regular boost topology.
figure 2. input current limiting using max668 sepic.
the use of a coupled inductor (two inductors wound on the same core) such as the coiltronics ctx10-3 (figure 1) reduces the leakage inductance. this makes it possible to achieve efficiencies of up to 85% in practice. efficiency for this sepic converter is shown in figure 3.
figure 3. efficiency of the max668 sepic.
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universal serial bus (usb) is a popular way to connect pcs and consumer devices. it is simple and inexpensive and can connect multiple external peripherals simultaneously. as mobile devices add more functionality such as text messaging, web surfing, information storage and music playing, the need to communicate with a pc is increasing. many of the mobile devices today offer a usb interface native in the device. the sole purpose is to provide a connection for data communication. the device may be self powered (e.g., through a wall adapter) or draw the power from the usb bus.
the mobile devices are typically expected to connect to a powered usb hub. a usb device can have its own power source (e.g. batteries or a wall plug) or draw the power from the usb bus. a powered usb host can provide up to 500ma current. using the power supplied by usb can be tricky because the voltage to a usb powered device may be as low as 4.35v, when cable and connector drops are considered, or as high as 5.5v. if the device is to operate with a voltage adapter for a source it may see input voltages as high as 9v. in order to accommodate these various scenarios, a step-up/step-down dc-dc topology works well. the input and output specifications for a controller/converter are summarized in table 1.
table 1. power supply requirements for usb compatible portable device parameter requirement
input voltage vin 4v to 9v
input current iin 500ma (±5%) max.
output power pout 2.4w typical
output voltage vout 6v (±5%) typical
output load current iout 400ma max.
regulation min. vout =5.5v at iout = 200ma
sepic to 6v with input current limitingthis step-up/step-down supply is used to power a li+ battery charger. since the charger itself will have a drop in voltage across it, the output voltage was set to 6v. the single-ended primary inductance converter shown in figure 1 is ideal for this application. this buck-boost topology is needed since the input voltage can vary from values below the output voltage to values greater than the output voltage (table 1). the max668 boost controller is adapted to sepic topology (figure 1).
figure 1. sepic power supply for usb compatible device.
the current limit resistor r4 (figure 1) is used to limit the input current to a maximum of 500ma as specified in table 1. the input current limit also ensures short-circuit protection ensuring usb compliance even under output fault conditions. when the output exceeds the input current limit the output voltage will reduce and restrict the input current to 500ma as shown in figure 2. note the extra inductor required in this topology as compared to a regular boost topology.
figure 2. input current limiting using max668 sepic.
the use of a coupled inductor (two inductors wound on the same core) such as the coiltronics ctx10-3 (figure 1) reduces the leakage inductance. this makes it possible to achieve efficiencies of up to 85% in practice. efficiency for this sepic converter is shown in figure 3.
figure 3. efficiency of the max668 sepic.
简单讲解一下时控开关手动如何打开或者关闭
对仪器仪表行业未来的发展方向详解
如何正确的选择物联网协议
集成电路发展之路，中国能出现世界级企业吗?
PPTC组件在锂离子电池组短路及过充电保护中的应用
Current Limited DC-DC Controll
综合“软硬件”解决方案 解读蚂蚁共享智能背后的技术原理
YYH40系列语音合成芯片特点及电路图介绍
水文地下水的监测系统的功能特点介绍
PCB元器件应该遵循哪些布线规则
Bose发布CSD新版本，扩展了ToneMatch音频引擎
ph计复合电极构造_ph计复合电极的使用方法_ph计复合电极怎么维护
锂离子电池的组成部分——隔膜（详细篇）
智能客服怎样发展的更完善
麒麟659和骁龙625功耗及差距的对比分析
气体放电管的设计实例
Waymo计划在密歇根州东南部建立一家生产机器人汽车的工厂
大模型会给操作系统带来什么样的想象？
物联网的演变为企业提供了哪些机遇和挑战
苏州固锝和华景传感在无锡签署了《合资协议》