标签: charger

Well, this is can be quite a shock and no mistake. I've been happily toddling along through life under the impression that the way in which I charge my iPad will prolong the life and efficiency of its battery. Now, however, it seems that my habits may be having the opposite effect (sad face).   This all started a few days ago when I evaluated some iClever USB chargers (see Meet my 4-Port beast of a USB charger ).   A roughty-toughty 4-port iClever charger (Source: Max Maxfield / EETimes.com)   As part of that column, I made the following comment: I don’t know if this is still true, but I remember being told that the batteries in things like iPads can exhibit a sort of "memory" effect that impacts their charging ability -- also, that it's best to let the charge fall to around 10% and to then recharge to 100% in a single sitting. I've informed my wife (Gina The Gorgeous) and my son (Joseph The All-Knowing) as to this charging philosophy on numerous occasions. As with most things, however, they haven’t paid the slightest attention to what I've had to say. On the contrary, they tend to charge their devices willy-nilly whenever they happen to come into close proximity with a charger and the mood takes them.   The embarrassing thing is that -- and I'm saying this in a hushed whisper with a brown paper bag over my head -- it turns out that their way of doing things may actually be better than mine. The way in which I discovered this niggling and nagging nugget of knowledge was when a reader, Roger46, posted the following comment to my USB charger column:   As a calculator design engineer in the 70s, I well remember memory effect when we were using NiCad rechargeable batteries. That and a rather high self-discharge rate. Lithium batteries seem to have moved past that era, fortunately (see this discussion about prolonging the life of modern batteries on BatteryUniversity.com). My personal experience seems to agree with their suggestions. My wife and I have had similar phones in the past. She tended to use hers until it ran down, while I liked to keep mine recharged as often as possible. She replaced the battery pack in one phone twice while I was still on the original with identical phones...   I immediately bounced over to see the discussions in question. Arrgggh! It seems that limiting oneself to partial discharges reduces stress and prolongs battery life. In Table 2 -- Cycle life as a function of discharge -- we discover that a 100% DoD (depth of discharge) results in only 300 to 500 discharge cycles; a 50% DoD offers 1,200 to 1,500 discharge cycles; and a 25% DoD provides 2,000 to 2,500 discharge cycles.   Now, remembering that -- viewing this simplistically -- 1,000 discharge cycles at 50% DoD equates to 500 discharge cycles at 100% DoD with regard to the service life of the battery, it seems to me that the 50% DoD offers the optimum lifetime of the aforementioned options. As usual, however, there's more to the story. I trotted over to see my chum Ivan in the next bay, because Ivan is a guru on all things related to power. Ivan noted that NiCad rechargeable batteries did indeed exhibit a memory effect and required a deep discharge in order to obtain the best results. Ivan also confirmed that the Lithium Ion batteries used in today's smartphones and tablet computers no longer suffer from this effect (the batteries in your notepad computer and/or batteries of different Lithium chemistries may be another story).   Ivan also proffered a few more sage words of advice. He noted that elevated temperatures also affect battery life and that, running one's iPad (for example) at full whack will cause the battery to warm up a tad. The point is that charging the battery when it's already warm is not a great idea; it's better to wait a while and then charge the device when it's cooled down.   But wait, there's more. Once the battery has reached 100% charge, that's a good time to stop charging it -- continuing to trickle-charge a Lithium Ion battery (like leaving it plugged into the charger overnight) can also degrade its performance over time. Of course, this depends on the sophistication of the charger and/or the thing being charged.   Peeking inside a cheap-and-cheerful smartphone charger (Source: Max Maxfield / EETimes.com)   More sophisticated chargers will take the environment into account and properly terminate charging at the optimal point. Some chargers are so smart they can determine the battery's chemistry and make any appropriate adjustments. Similarly, more sophisticated devices will recognize when their batteries are chock-a-block full, at which point they will stop drawing power from the charger.   The bottom line is that I will be changing my charging habits henceforth. I'm not going to become going to try to not become obsessive compulsive about this, but I am going to start charging my iPad when it reaches 50% DoD. Also, if I've been doing something compute-intensive like watching videos or running a simulation, I'm going to give the little scamp time to cool down before commencing the recharge process. (I will do all of this until devices evolve to using different battery chemistries, at which point everything will have to be re-evaluated like déjà vu all over again.) How about you? Will what you've read here change your modus operandi vis-à-vis charging your smartphone and tablet?   Max Maxfield

I typically can't help myself when it comes to fixing things, especially electronics. My better half returned from a bargain-hunting day with a wind-up flashlight and charger she found for a dollar in a thrift store. She said she wanted a flashlight for an upcoming camping trip and a charger for her cell phone that she could use out in the wild. My wife loves a bargain, so she was pretty pleased with herself and asked me to help her hook up the charger. Unfortunately, she was disappointed when nothing seemed to charge. I had to investigate; I hate things that don't work. After some exploration I discovered the output was only 3V. Maybe that was why it was found in the thrift store. In her typical style she threw the offending item in the garbage, rolling her eyes in frustration. As I said, I can't help myself when it comes to fixing things so I picked it out of the trash and had a little look to see if I could diagnose the problem. I thought I could add a boost circuit to get it to 5V, but I didn't have the parts. I added it to the mountain of unfinished projects that used to be my desk. Eventually, the day came when I couldn't ignore Mount Electronica any longer, and I embarked on an expedition to the desk. Not long into the tidying session, I discovered an LED light bulb I had bought for the kitchen a while ago. I had made the rookie mistake of not checking the voltage that was required and picked up a 12V bulb instead of the one I needed. It had joined the pile and now it distracted me from my chore. I decided to strip out the 1W LED from the bulb for another project. Inside I found an MC34063 IC. Checking the datasheet, as we geeks do religiously, I identified it as a Step-Up/Down Regulator that was being used to step down 12V to 3V. I started work on transforming it to a step-down straight away. Lady Luck was smiling on me that day as the datasheet had an example, which meant that all I needed to do was pick the right resistors. The circuit needed to change completely, so out came the breadboard. After some cavalier soldering to mount a few of the surface mount parts, I was up and running. I'd only used two resistors extra to the original parts from the bulb. After the initial success I just had to cram it into the flashlight and I was done. On cracking open the flashlight I realised that I didn't have much room to spare. The breadboard simply wouldn't fit. Undeterred, I decided that a little PCB design was needed. I knocked together a single-sided board and mounted it on top of the existing PCB in the flashlight, placing the components to fit inside the curved case as best I could. I had no idea if it would actually fit or whether this last hurdle would be the one that tripped me. With a PCB etched and all of the components soldered, I fired up the converter for one final test before hacking it into the case. It worked like a charm, first time! The voltage out was as close to 5V as I was going to get: Now it was time to get it into the case. Unfortunately, Lady Luck was looking the other way. The case just would not close. A closer inspection gave me some hope. The PCB could potentially shed some excess weight. I took a deep breath and sanded down the PCB as close to the components as I dared and trimmed the wires as short as they could possibly be. I gave it another try. The case closed. It fit perfectly. All that was left to do was connect the switch and the winder, and I was on the home stretch. Then came the moment of truth: Would it actually charge? With the cell phone connected, I cranked the handle, building up speed and hoping for the best. Success! The charge light came on. I had done it. But it wasn't all good news. The flashlight wasn't quite what it once was, as the boost converter was draining the capacitor. It now needs a crank before every use. It's a small price to pay, though. One day I may do a rewire, but for now, my work is done. I had transformed the charger that didn't make the grade into something that actually worked. Sadly, it was a little late for the original camping trip by the time I had finished. Brice Harris is a father of three, husband of one, and he enjoys seeing things work. Together they raise backyard chickens and make maple syrup. He submitted this article as part of Frankenstein's Fix, a design contest hosted by EE Times (US).  

I was brought up Zimbabwe, which used to be Rhodesia until 1980. Named after Cecil John Rhodes, who had the ambition to paint the map of Africa red—the colour of British colonies. However, in 1965, the then newly elected prime minister, Ian Smith, gave the finger to Britain and declared independence. So I have something in common with Americans—I also come from a country that gave Britain the heave-ho. One result of our independence was that Britain—and most of the rest of the world—put sanctions on us, which resulted in a culture of invention, re-use, and repair. It only lasted for 15 years (you've beaten us by a bit there!), but I digress. Suffice to say that it instilled in me a great reluctance to throw away anything that could be fixed or used for something. Fast forward 33 years and I found myself in Australia, a throwaway society of note, rooting around in a skip (a garbage dumpster in American English) on a work site I was visiting. (This habit of mine arouses great amusement in my Australian colleagues, but it is amazing what perfectly good or easily fixable things you find in skips here.) In this skip, I saw a nice, black, moulded-plastic case, so I grabbed it. It was heavy and had the Black and Decker logo on it. I opened it and found a perfectly fine looking cordless drill, battery, and charger.   Now, even Aussies won't throw away a good drill very often, so I immediately assumed that the drill, the battery, or the charger was not working. I pulled the trigger on the drill and it gave a weak half turn. So hopefully the drill was OK. When I got it home I plugged in the charger and put the battery in it. No lights. I charged the battery—a 14.4V NiCd—on my workshop power supply overnight and tried it in the drill in the morning. It seemed to work fine. So all I had to do was fix the charger. This was reassuringly heavy, but getting into it gave me my next problem. The case was held together with security Torx screws, which have a little pin up the middle that has to be matched by a hole in the driver bit. I had the right bit, but it was too short to get into the hole in the charger case. A visit to my favourite tool store produced a set of longer bits for $10 (and I never need an excuse to add to my collection of screwdrivers!). When I opened the charger I found a nice hunk of iron—no namby-pamby switching power supplies here—and both windings on the transformer measured low resistance. There was a main board with five or six transistors on it and a connector board with two thermistors, one of which contacted the top NiCd cell through a hole in the battery case.   So, it was obviously a thermally limited charger. The label on the top said it was a one-hour charger. Even more reassuring, since so many chargers advertise themselves as fast chargers but don't have any limiting at all, and usually have the ominous warning in the handbook "Do not charge battery for more than five hours." Forget this a couple of times and your batteries are cactus. I couldn't get a schematic for the charger but it was simple enough to trace. This is the diagram I arrived at:   Do you notice anything strange about this diagram? The control circuitry, particularly the emitters of Q3/4/5/6, do not have any connection to the negative of the battery or power supply. And looks like it should! I re-examined the PCB and could not find anything—the negative of the bridge rectifier only had connections to the smoothing capacitor C1 and the battery connector. Then I remembered the thermistors. There appeared to be two of them in parallel, and one leg was connected to the emitters of Q3-6. That leg also went to a nice shiny bit of metal that, when the battery was inserted in the charger, contacted the case of the bottom battery and made the connection from the control circuit, through the battery negative outer case to the negative rail of the charger. While I was looking at this I noticed that this connection on the small, separate PCB that held the battery connectors and thermistors did not look too healthy. I gave the wire a tug and could see the end of it moving in the blob of solder on the small PCB. Bingo! One of the dreaded dry joints. I never just resolder these. I sucked off the solder that was there—as usual, an insufficient amount due to the wave soldering of the board—cleaned up the wire and then resoldered the joint. I was able to place the connector board onto the battery without putting it back in the charger case and lo and behold: the "Charging" light came on and the battery voltage went up. Being an impatient sort of fellow, I touched my soldering iron tip to one of the thermistors and the "Full charge" light came on. Job done! Or so I thought. When I tried to actually USE the drill, I found the chuck had seized. Maybe that's why it was chucked out. Pardon the bad pun...). But I managed to sort that out with judicious use of WD-40, a pair of slip-joint pliers and some of what my dad used to call "brute force and ordinary ignorance." Result: it's now fully working. For $10 and a fair bit of time, I got myself a nice drill, a useful set of screwdriver bits, and the satisfaction of bringing something back from the dead! Don Tavidash submitted this article as part of Frankenstein's Fix, a design contest hosted by EE Times (US).

I grew up in Zimbabwe, which used to be Rhodesia until 1980. Named after Cecil John Rhodes, who had the ambition to paint the map of Africa red—the colour of British colonies. However, in 1965, the then newly elected prime minister, Ian Smith, gave the finger to Britain and declared independence. So I have something in common with Americans—I also come from a country that gave Britain the heave-ho. One result of our independence was that Britain—and most of the rest of the world—put sanctions on us, which resulted in a culture of invention, re-use, and repair. It only lasted for 15 years (you've beaten us by a bit there!), but I digress. Suffice to say that it instilled in me a great reluctance to throw away anything that could be fixed or used for something. Fast forward 33 years and I found myself in Australia, a throwaway society of note, rooting around in a skip (a garbage dumpster in American English) on a work site I was visiting. (This habit of mine arouses great amusement in my Australian colleagues, but it is amazing what perfectly good or easily fixable things you find in skips here.) In this skip, I saw a nice, black, moulded-plastic case, so I grabbed it. It was heavy and had the Black and Decker logo on it. I opened it and found a perfectly fine looking cordless drill, battery, and charger.   Now, even Aussies won't throw away a good drill very often, so I immediately assumed that the drill, the battery, or the charger was not working. I pulled the trigger on the drill and it gave a weak half turn. So hopefully the drill was OK. When I got it home I plugged in the charger and put the battery in it. No lights. I charged the battery—a 14.4V NiCd—on my workshop power supply overnight and tried it in the drill in the morning. It seemed to work fine. So all I had to do was fix the charger. This was reassuringly heavy, but getting into it gave me my next problem. The case was held together with security Torx screws, which have a little pin up the middle that has to be matched by a hole in the driver bit. I had the right bit, but it was too short to get into the hole in the charger case. A visit to my favourite tool store produced a set of longer bits for $10 (and I never need an excuse to add to my collection of screwdrivers!). When I opened the charger I found a nice hunk of iron—no namby-pamby switching power supplies here—and both windings on the transformer measured low resistance. There was a main board with five or six transistors on it and a connector board with two thermistors, one of which contacted the top NiCd cell through a hole in the battery case.   So, it was obviously a thermally limited charger. The label on the top said it was a one-hour charger. Even more reassuring, since so many chargers advertise themselves as fast chargers but don't have any limiting at all, and usually have the ominous warning in the handbook "Do not charge battery for more than five hours." Forget this a couple of times and your batteries are cactus. I couldn't get a schematic for the charger but it was simple enough to trace. This is the diagram I arrived at:   Do you notice anything strange about this diagram? The control circuitry, particularly the emitters of Q3/4/5/6, do not have any connection to the negative of the battery or power supply. And looks like it should! I re-examined the PCB and could not find anything—the negative of the bridge rectifier only had connections to the smoothing capacitor C1 and the battery connector. Then I remembered the thermistors. There appeared to be two of them in parallel, and one leg was connected to the emitters of Q3-6. That leg also went to a nice shiny bit of metal that, when the battery was inserted in the charger, contacted the case of the bottom battery and made the connection from the control circuit, through the battery negative outer case to the negative rail of the charger. While I was looking at this I noticed that this connection on the small, separate PCB that held the battery connectors and thermistors did not look too healthy. I gave the wire a tug and could see the end of it moving in the blob of solder on the small PCB. Bingo! One of the dreaded dry joints. I never just resolder these. I sucked off the solder that was there—as usual, an insufficient amount due to the wave soldering of the board—cleaned up the wire and then resoldered the joint. I was able to place the connector board onto the battery without putting it back in the charger case and lo and behold: the "Charging" light came on and the battery voltage went up. Being an impatient sort of fellow, I touched my soldering iron tip to one of the thermistors and the "Full charge" light came on. Job done! Or so I thought. When I tried to actually USE the drill, I found the chuck had seized. Maybe that's why it was chucked out. Pardon the bad pun...). But I managed to sort that out with judicious use of WD-40, a pair of slip-joint pliers and some of what my dad used to call "brute force and ordinary ignorance." Result: it's now fully working. For $10 and a fair bit of time, I got myself a nice drill, a useful set of screwdriver bits, and the satisfaction of bringing something back from the dead! Don Tavidash submitted this article as part of Frankenstein's Fix, a design contest hosted by EE Times (US).  

主要职责 ： 1.深刻理解用户要求，根据客户应用采用合理方案并制定spec； 2.领导进行系统级电源架构设计，利用先进的IC电源知识定义和开发有效的解决方案； 3.领导进行各种电源IC包含模拟IC和数模混合IC的开发和验证，并对版图和PCB的设计进行相关指导； 4.参加产品的方案制定、线路开发、工程流片、样片测试和量产应用等所有阶段； 5.根据市场发展趋势，对电源IC制定严谨合理的长远规划； 6.培养开发优秀的电源管理IC开发团队。   要求： 基本技巧 1.工具：掌握或熟悉模拟IC设计相关的EDA工具； 2.语言：熟练使用汉语和英语。 3.教育背景：微电子及相关专业硕士以上; 4.具有良好的沟通能力 工作经验： 1.六年以上模拟IC系统设计经验，主导过多款电源管理IC spec的制定； 2.成功开发过多种电源管理IC，包括DC-DC，LDO，AC-DC，LED; driver，charge; pump，charger等； 3.参与过多种电源IC的实际开发、验证与测试工作，熟悉电源IC用到的各种工艺制程； 4.熟悉市场上各类电源器件，帮助客户和设计工程师选择电源管理系统外围器件； 5.带过研发团队，能合理制定计划并分配资源； 6.具有海外知名公司经历者优先。  KT-Judy Email:judy-wu@kthr.com QQ:782288610 MSN:Judy9228@hotmail.com