Battery Backup with Delay(具有时滞
battery backup with delay(具有时滞的备用电池)
abstract:this application note explains that the simplest link from a main supply and backup battery to a load is the diode-or connection. however simple that concept, a diode-or does not work when the battery voltage exceeds the main supply voltage. the article presents a circuit which handles that condition. the max931 comparator with 2% reference is featured in the design.
this design idea appeared in the may 25, 2006 issue of electronic design magazine.
the simplest link from a main supply and backup battery to a load is the diode-or connection. however, a diode-or does not work when the battery voltage exceeds the main supply voltage. the figure 1 circuit handles that condition. the main switch-mode supply voltage ranges from 7v to 30v, and the backup supply is a 9v battery.
figure 1. ic1, the max931 comparator, monitors the main supply voltage. it also turns on the backup battery by grounding its negative terminal when the main supply drops below 7.4v.
the max931 is an ultra-low-power comparator with a 1.182v bandgap reference. during normal operation the comparator output is low, the three parallel-connected n-channel fets are off, and the battery's negative terminal floats. power flows from the main supply to the load. when the main voltage declines to 7.4v the comparator's output goes high, turning on the n-fets and grounding the negative terminal of the battery. power then flows from the battery to the load (figure 2).
figure 2. in response to a gradual decrease in the main supply voltage (channel 3 in figure 1), the n-fet gate voltage goes high (channel 2). this activates the battery and drives the output voltage (channel 1) to 9v. as the main supply voltages passes 8.4v the n-fets turn off, allowing the output to resume tracking the main supply voltage.
d1, c1, and r6 introduce a delay in the gate drive. this delay eliminates a supply-rail glitch that would otherwise occur when switching from the battery to the main supply. while those glitches can cause an unacceptable reset in the system's microcontroller, figure 3 illustrates the absence of that effect with this circuit. note that r3 and r4 set the hysteresis in the max931 to 800mv, as required for proper operation. see the max931 data sheet for calculation of those resistor values.
figure 3. the output in figure 1 responds without glitches in response to a fast restoration of the main supply voltage.
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abstract:this application note explains that the simplest link from a main supply and backup battery to a load is the diode-or connection. however simple that concept, a diode-or does not work when the battery voltage exceeds the main supply voltage. the article presents a circuit which handles that condition. the max931 comparator with 2% reference is featured in the design.
this design idea appeared in the may 25, 2006 issue of electronic design magazine.
the simplest link from a main supply and backup battery to a load is the diode-or connection. however, a diode-or does not work when the battery voltage exceeds the main supply voltage. the figure 1 circuit handles that condition. the main switch-mode supply voltage ranges from 7v to 30v, and the backup supply is a 9v battery.
figure 1. ic1, the max931 comparator, monitors the main supply voltage. it also turns on the backup battery by grounding its negative terminal when the main supply drops below 7.4v.
the max931 is an ultra-low-power comparator with a 1.182v bandgap reference. during normal operation the comparator output is low, the three parallel-connected n-channel fets are off, and the battery's negative terminal floats. power flows from the main supply to the load. when the main voltage declines to 7.4v the comparator's output goes high, turning on the n-fets and grounding the negative terminal of the battery. power then flows from the battery to the load (figure 2).
figure 2. in response to a gradual decrease in the main supply voltage (channel 3 in figure 1), the n-fet gate voltage goes high (channel 2). this activates the battery and drives the output voltage (channel 1) to 9v. as the main supply voltages passes 8.4v the n-fets turn off, allowing the output to resume tracking the main supply voltage.
d1, c1, and r6 introduce a delay in the gate drive. this delay eliminates a supply-rail glitch that would otherwise occur when switching from the battery to the main supply. while those glitches can cause an unacceptable reset in the system's microcontroller, figure 3 illustrates the absence of that effect with this circuit. note that r3 and r4 set the hysteresis in the max931 to 800mv, as required for proper operation. see the max931 data sheet for calculation of those resistor values.
figure 3. the output in figure 1 responds without glitches in response to a fast restoration of the main supply voltage.
可以吃的药片传感器
大肠杆菌检测仪的检测与应用范围
什么是智能家居？各大智能家居厂商都有哪些核心竞争力
开发工程师和架构师的区别
MLX90640 红外热成像仪测温模块开发笔记（完整版）
Battery Backup with Delay(具有时滞
比凌渡大一圈，比迈腾有内涵，这豪华新车已经跌到12万
超声波电子导盲电路的工作原理
Microchip推出64Mb并行SuperFlash®闪存，丰富旗下应用于航天系统的COTS耐辐射产品阵容
轨道交通车体自动化检修测量大尺寸测量仪器-CASAIM激光三维扫描仪
罗姆开发出用于英特尔凌动处理器E3800新产品系列的电源IC
CAN总线知识总结
庆科信息技术EMW3081A简介
HDMI的前世今生
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乌普萨拉大学推出了一款适用于太阳能的物联网传感器电源管理系统
Model 3，中国电动车还能实现弯道超车吗？
探讨自动驾驶的前世今生
介绍传热学基本理论简介及问题讨论 并通过模拟来验证所讨论的问题
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