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前篇
在我参加工作之初,师傅让设计一款开关电源,类似于下图(来源网络):
开关电源原理基本基础,可是该怎么设计???
大家都玩过积木没有?
说明: 使用基础,大小,颜色合适的形状拼出了不同物体的形状; Tips: Building different shapes of differentthings by using base shape of building blocks, like cylinder, cube.
那么对于电路设计我们该怎么做?
Whatto do, what can we do?
成为一位研发工程师的重要因数:兴趣+基础+创新; Themost important factors to be a design engineer are hobbies and interests,basis, innovations; 这节主要讲的是基础; Whatwe talking about during this lesson is basis; 什么是基础(what’sthe basis): •1)需求(Demands);
•2)使用环境(Environment);
•3)使用场合(Applications);
•4)输入参数、输出参数(Input、Output);
•5)负载(Load);
•6)低“成本”(Low costs);示例:宽范围电池反接保护电路
•1)需求(Demands):
前电动汽车的电池包系统多为200VDC~800VDC之间;若电池反接充电会引起电池发热,着火,甚至爆炸电气安全事故;这是不被允许的。 当电池准备充电时,先检查电池是否反接,若反接必须给出反接警告,并且停止充电;检测电路需要通用,适用任何一个电压等级的电池包系统。 The battery pack voltage in the electriccars are between 200VDC to 800VDC, if the battery pack is charged in a oppositedirection, the battery may inflame or ignition, the worst things is the batterywill blast like a bomb, it’s safety misadventure and its forbidden. Before charging, we should check outwhether the battery is connected in a opposite direction, if do, then, givingan warning single and cut off the charging circuit. Also, the checking circuitcould be used to different battery packs with different voltage. •2)环境(Environment):温度、湿度、气压;Temperature, humidity, atmosphericpressure.
Ø温度环境(Temperature):
工作环境范围-20℃~50℃,即功能电路或电子元器件可靠工作温度范围;半导体每升高10℃,寿命折半。The working range is between -20℃ to 50℃,eachcircuit and component should works verywell. Semiconductor’s life will have 50% off,while its working temperature rise every10 ℃. Ø湿度环境(Humidity):
工作环境湿度5%~95%,即说明成品的绝缘防护等级要求;Working humidityis between 5% to 95% which means insulation,and what can designer do for products insulation. Ø气压环境(Atmospheric pressure):
暂不考虑(For now, don’t care about it); Ø其他( Others )
•3)使用场合(Applications)
民用,工业用,汽车用,军用,民航用,军用航天;Civil,industrial, automotive, military,civilaviation, military space;
主要考虑的电子元器件的 质量即失效率;Thequality and failure rate of each electronic components;
目前使用我司使用的是工业级,汽车级元器件;For now, the electric components used inproducts should under the quality of industrial and automotive.
本电路设计中使用工业级;Industrial electric components willbe fine in this circuit design;
•4)输入参数,输出参数(Input,Output) :
Ø输入(Input)
电压、电流、频率/占空比等;Voltage,current, frequency, duty cycle, etc.; 电压(Voltage):200VDC~800VDC; 电流(Current):限制在1毫安以内;Limitless than 1mA; 频率(frequency ):50Hz~200kHz; Ø输出(Output)
数字信号0,1用于单片机识别,其物理模拟量等级为0~0.4VDC,2.7VDC~3.6VDC;Thedigital single 0 and 1 which ARM can be recognized, for digital 0 the voltageis between 0 to 0.4VDC, for 1 the voltage is between 2.7VDC to 3.6VDC; •5)负载(Load) :
赞略;Leaveout for now; •6)低“成本”(Lowcosts):
Ø低功耗;Lowpower consumption;
Ø硬件成本:元器件数量及单价;Hardwarecosts, the quantity and the price of each electric component;
Ø人工成本:包括采购,PCB绘制工时;Laborcosts, it contains purchase, and layout PCB etc.;
Ø生产成本:加工工序是否复杂;Productioncosts;
开始设计(Let’s do it)
1、电池充电回路正确连接时,保护电路不工作; The protection circuit works during battery charging loop connected in opposite direction, otherwise it doesn’t work. 想想什么元器件具有单向导电作用;Thinking, which component do have one-wayconduction; 二极管,电压等级1000V,因为最高电池包电压为800VDC; Diode,rated voltage is 1000VDC,becausethe max voltage of batterypackis 800VDC; 一个二极管就够了吗? 不是,因为其漏电流,需要两个二极管; One diodeis enough? No it needs two, because diode do have leakage current. 2、检测电路需要低功耗,确保检测电路长时间工作电子元件不发热,设计回路最大电流为1mA; When the circuit is working for a longtime, the temperature of each component should not rise. So the max workingcurrent inthis circuit should less than 1mA; 重要: 安规设计以700VDC为界限,所以电路需要考虑800VDC情况下的安规绝缘问题,尤其需要注意元器件选型,以及PCB布板时的排布,以及走线位置等; Attention: According to safety criterion, whencircuit working under 800VDC, the isolation situation is totallydifferent from 700VDC, so we must pay more attention to select component, andlayout PCB. 3、符合功能,宽范围电压检测;Widerange voltage check; 设回路在800VDC时反接,检测回路电流为1mA,根据欧姆定律在200VDC时,检测回路电流为0.25mA;但是0.25mA太小不足以驱动电平转换器件; The current is 1mA when the voltage is800VDC, due to the Ohm’s law, the current is 0.25mA when the voltage is 200VDC,but, 0.25mA is too small to driver level conversion component. 想想,什么元器件具有放大电流的作用;Thinking, whatkind of component do have current amplification. 三极管;Transistor;
4、输出信号ARM芯片可识别;ARMcan recognize the output single; 对于模数信号转换,我们通常使用光耦;Optocoupleris typically used to convert analog and digital signals; 5、成品电路,成本约为¥3元;Finishedcircuit, and the hardware cost is ¥3。PCB板直接贴片好即可,无需调整。 6、实验数据;Experimentaldata; 数据结果满足单片机,数字芯片对信号0的识别。故而设计有效。
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