Favorite reverse bias protection for battery circuits
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From: linnix on 16 Mar 2010 14:28 On Mar 16, 9:56 am, Charlie E. <edmond...(a)ieee.org> wrote: > Hi All, > Still working on my color reader, and getting close. Biggest problem > is that now I have almost TOO much drive on my LEDs, but that I can > deal with! > > Now, to the latest problem. My system is for the visually impaired. I > just put the batteries in one of my prototypes backwards, and it > didn't last very long. I believe that's why they invented LCD to save power. Not sure how well it can be read by visually impaired. > While I expect this device to have very long > battery life, since it normally doesn't operate but for a second or > two, it looks like the MC1253's don't like getting reversed biased > very long. So, for my design question of the day - What is your > favorite circuit for preventing reverse bias from the batteries? The > old diode trick drops too much voltage, so wondered if there are any > clever FET tricks to block backwards voltages. LCD controllers are usually less sensitive to supply voltage than LED drivers. LCD segments need almost zero currents. > > Thanks! > > Charlie
From: Jim Thompson on 16 Mar 2010 14:34 On Tue, 16 Mar 2010 10:56:46 -0700, Charlie E. <edmondson(a)ieee.org> wrote: >Hi All, >Still working on my color reader, and getting close. Biggest problem >is that now I have almost TOO much drive on my LEDs, but that I can >deal with! > >Now, to the latest problem. My system is for the visually impaired. I >just put the batteries in one of my prototypes backwards, and it >didn't last very long. While I expect this device to have very long >battery life, since it normally doesn't operate but for a second or >two, it looks like the MC1253's don't like getting reversed biased >very long. So, for my design question of the day - What is your >favorite circuit for preventing reverse bias from the batteries? The >old diode trick drops too much voltage, so wondered if there are any >clever FET tricks to block backwards voltages. > >Thanks! > >Charlie Some variation on this... http://analog-innovations.com/SED/PerfectDiodeForChargerIsolation.pdf Do you have enough voltage to turn on MOSFET's? Probably could do it with bipolar's... I'll ponder :-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | The only thing bipartisan in this country is hypocrisy
From: Joerg on 16 Mar 2010 14:46 Jim Thompson wrote: > On Tue, 16 Mar 2010 10:56:46 -0700, Charlie E. <edmondson(a)ieee.org> > wrote: > >> Hi All, >> Still working on my color reader, and getting close. Biggest problem >> is that now I have almost TOO much drive on my LEDs, but that I can >> deal with! >> >> Now, to the latest problem. My system is for the visually impaired. I >> just put the batteries in one of my prototypes backwards, and it >> didn't last very long. While I expect this device to have very long >> battery life, since it normally doesn't operate but for a second or >> two, it looks like the MC1253's don't like getting reversed biased >> very long. So, for my design question of the day - What is your >> favorite circuit for preventing reverse bias from the batteries? The >> old diode trick drops too much voltage, so wondered if there are any >> clever FET tricks to block backwards voltages. >> >> Thanks! >> >> Charlie > > Some variation on this... > > http://analog-innovations.com/SED/PerfectDiodeForChargerIsolation.pdf > > Do you have enough voltage to turn on MOSFET's? > > Probably could do it with bipolar's... I'll ponder :-) > Which HV CMOS process did that get rolled onto, if I may ask? -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Jim Thompson on 16 Mar 2010 14:51 On Tue, 16 Mar 2010 11:46:11 -0700, Joerg <invalid(a)invalid.invalid> wrote: >Jim Thompson wrote: >> On Tue, 16 Mar 2010 10:56:46 -0700, Charlie E. <edmondson(a)ieee.org> >> wrote: >> >>> Hi All, >>> Still working on my color reader, and getting close. Biggest problem >>> is that now I have almost TOO much drive on my LEDs, but that I can >>> deal with! >>> >>> Now, to the latest problem. My system is for the visually impaired. I >>> just put the batteries in one of my prototypes backwards, and it >>> didn't last very long. While I expect this device to have very long >>> battery life, since it normally doesn't operate but for a second or >>> two, it looks like the MC1253's don't like getting reversed biased >>> very long. So, for my design question of the day - What is your >>> favorite circuit for preventing reverse bias from the batteries? The >>> old diode trick drops too much voltage, so wondered if there are any >>> clever FET tricks to block backwards voltages. >>> >>> Thanks! >>> >>> Charlie >> >> Some variation on this... >> >> http://analog-innovations.com/SED/PerfectDiodeForChargerIsolation.pdf >> >> Do you have enough voltage to turn on MOSFET's? >> >> Probably could do it with bipolar's... I'll ponder :-) >> > >Which HV CMOS process did that get rolled onto, if I may ask? California Micro Devices (do they still exist?) for a LiIon charge/discharge controller. ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | The only thing bipartisan in this country is hypocrisy
From: D Yuniskis on 16 Mar 2010 15:15
Hi Charlie, Charlie E. wrote: > Still working on my color reader, and getting close. Biggest problem > is that now I have almost TOO much drive on my LEDs, but that I can > deal with! > > Now, to the latest problem. My system is for the visually impaired. I > just put the batteries in one of my prototypes backwards, and it > didn't last very long. While I expect this device to have very long > battery life, since it normally doesn't operate but for a second or > two, it looks like the MC1253's don't like getting reversed biased > very long. So, for my design question of the day - What is your > favorite circuit for preventing reverse bias from the batteries? The > old diode trick drops too much voltage, so wondered if there are any > clever FET tricks to block backwards voltages. Solve this problem *mechanically*. You need to prevent the batteries from being *installed* wrong, in the first place. E.g., any sort of circuit that protects (the rest of) the circuit from reversed battery won't do anything to tell the VI user *why* your device isn't working. Are the batteries *dead*? Installed wrong? Corroded terminals? Or is the *device* broken?? "Key" the battery holder so the user can feel the correct orientation for the batteries *and* so it prevents the cells from making electrical contact if not oriented properly. Think of how the *user* is going to interact with your device. Close your eyes and "figure out" why it doesn't work :-/ |