protection circuits (swith circuit)
 User Name Stay logged in? Password
 Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read Search

 Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
 Thread Tools Search this Thread
 30th April 2012, 01:57 PM #1 linxiaoxin   diyAudio Member   Join Date: Apr 2012 protection circuits (swith circuit) hello,everyone! the circuit diagram is to achieve the following functions 1　：　When the switches（s1,s2,s3） are off, 　output A is 45v,output B is -45v 2 : when you turn on the s1,the q1 and q2 are off,so the output A is not 45v,and output B is not -45v 3 : when you turn on the s2 (s1,s3 is off) , q5 is on ,so output A and output B are short circuits 4 ： when you turn on the s3 （s1,s2 is off) output A is -45v，and output B is 45v the logic circuit is no problem On the whole,but it should be improved because of high import input voltage.i am not good at modern circuit ,and i do not know how to add some protection circuits thank you for helping me ,thanks!
 1st May 2012, 08:30 AM #2 Mooly   diyAudio Moderator     Join Date: Sep 2007 There are many problems here. Assuming GND is a midpoint between - and + 45 volts (that is to say GND is your zero point) then Q1 and Q2 can not output more than around 4.3 volts on their emitters because the bias voltage (Vcc) is only 5 volts. Outputs A and B can only ever be even less than this. Not sure what you are trying to achieve here but this will never work I'm afraid. Q5 ? would be destroyed (and probably all before it) as it always shorts the switched rails. Any voltage differential of more than 0.7 volts across B and E will do this.
 1st May 2012, 08:37 AM #3 linxiaoxin   diyAudio Member   Join Date: Apr 2012 your analysis is good , do you know how to improve ? can you give me some ideas?
 1st May 2012, 09:06 AM #4 Mooly   diyAudio Moderator     Join Date: Sep 2007 You need the logic to be foolproof for a start if accidents are to be avoided. That means arranging so that there can never be any overlap or crossconduction. For example Q5 must never be able to be turned on if Q3 and 4 are on. Not even for a few microseconds. That applies to all transistors that "short" rails. Q1 would be better as a PNP and the base pulled low to activate and Q2 an NPN with the base pulled high. That would give minimal voltage losses using transistors as switches. That applies to all the series rail switches. You would need suitable level translation between the logic and all these transistors. To do it right is quite a major design exercise.
 1st May 2012, 09:35 AM #5 linxiaoxin   diyAudio Member   Join Date: Apr 2012 i am a freshman,i find it hard to do this .If time allows,would you help to draw it ? i really need an experienced person to do it what i want to do is to finish the following functions, 1:, disconnect 2 :short circuit 3:switch drop Last edited by linxiaoxin; 1st May 2012 at 09:41 AM.
godfrey
diyAudio Member

Join Date: Nov 2009
Location: Cape Town
Here is a start, with just S1 and S3.

When both switches are open, R14 pulls the voltages on the bases of Q11 and Q10 up. Q11 is switched on so current flows through Q11 and Q12 to switch on Q6 and Q8. Q10 is switched off, so no current flows through Q10, Q9, Q5 or Q7.

When S3 is closed, R15 pulls the voltages on the bases of Q11 and Q10 down. Q10 is switched on so current flows through Q9 and Q10 to switch on Q5 and Q7. Q11 is switched off, so no current flows through Q11, Q12, Q6 or Q8.

When S1 is closed, the bases of Q10 and Q11 are both grounded, so both are switched off and no current flows through any of the transistors.

Switch 2 may be difficult. If you can use a 2-pole 2-way switch, then it is very easy; you can just connect the switch so A and B are either connected to the power supply or to ground. If you have to use a single-pole single-throw switch then it is more difficult. Do A and B only have to be shorted to each other, or must they both be shorted to ground? Are you allowed to use a relay, or only transistors?
Attached Images
 psu.GIF (5.8 KB, 211 views)

 1st May 2012, 07:01 PM #7 Mooly   diyAudio Moderator     Join Date: Sep 2007 Nice implementation there Godfrey.
 2nd May 2012, 03:44 AM #8 godfrey   diyAudio Member   Join Date: Nov 2009 Location: Cape Town Thanks. It's the sort of thing you see for "forward/reverse" control in toy cars, except that toy manufacturers always seem to get away with 1/2 the number of components you would have thought possible.
linxiaoxin
diyAudio Member

Join Date: Apr 2012
Quote:
 Originally Posted by godfrey Here is a start, with just S1 and S3. When both switches are open, R14 pulls the voltages on the bases of Q11 and Q10 up. Q11 is switched on so current flows through Q11 and Q12 to switch on Q6 and Q8. Q10 is switched off, so no current flows through Q10, Q9, Q5 or Q7. When S3 is closed, R15 pulls the voltages on the bases of Q11 and Q10 down. Q10 is switched on so current flows through Q9 and Q10 to switch on Q5 and Q7. Q11 is switched off, so no current flows through Q11, Q12, Q6 or Q8. When S1 is closed, the bases of Q10 and Q11 are both grounded, so both are switched off and no current flows through any of the transistors. Switch 2 may be difficult. If you can use a 2-pole 2-way switch, then it is very easy; you can just connect the switch so A and B are either connected to the power supply or to ground. If you have to use a single-pole single-throw switch then it is more difficult. Do A and B only have to be shorted to each other, or must they both be shorted to ground? Are you allowed to use a relay, or only transistors?
good,you really make a penetrating analysis ,, i admire you very much.A and B only have to be shorted to each other, no must they both be shorted to ground. of course ,a relay is allowed ,but i I never used,if you can solve the swithch 2 problem by transistors,i can understand easily.
would you help me solve this problem ,thank you very much . good friends ! welcome to china!
,

 3rd May 2012, 05:48 AM #10 godfrey   diyAudio Member   Join Date: Nov 2009 Location: Cape Town Switch 2 functionality would be very difficult with transistors. With a relay, it is very easy. Switch 2 just has to connect 45V to the coil of the relay. Something like this would be good: PCB Relay DPDT 8A 48Vdc

 Thread Tools Search this Thread Search this Thread: Advanced Search

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is Off Forum Rules
 Forum Jump User Control Panel Private Messages Subscriptions Who's Online Search Forums Forums Home Site     Site Announcements     Forum Problems Amplifiers     Solid State     Pass Labs     Tubes / Valves     Chip Amps     Class D     Power Supplies     Headphone Systems Source & Line     Analogue Source     Analog Line Level     Digital Source     Digital Line Level     PC Based Loudspeakers     Multi-Way     Full Range     Subwoofers     Planars & Exotics Live Sound     PA Systems     Instruments and Amps Design & Build     Parts     Equipment & Tools     Construction Tips     Software Tools General Interest     Car Audio     diyAudio.com Articles     Music     Everything Else Member Areas     Introductions     The Lounge     Clubs & Events     In Memoriam The Moving Image Commercial Sector     Swap Meet     Group Buys     The diyAudio Store     Vendor Forums         Vendor's Bazaar         Sonic Craft         Apex Jr         Audio Sector         Acoustic Fun         Chipamp         DIY HiFi Supply         Elekit         Elektor         Mains Cables R Us         Parts Connexion         Planet 10 hifi         Quanghao Audio Design         Siliconray Online Electronics Store         Tubelab     Manufacturers         AKSA         Audio Poutine         Musicaltech         Aussie Amplifiers         CSS         exaDevices         Feastrex         GedLee         Head 'n' HiFi - Walter         Heatsink USA         miniDSP         SITO Audio         Twin Audio         Twisted Pear         Wild Burro Audio

 Similar Threads Thread Thread Starter Forum Replies Last Post linxiaoxin Analog Line Level 10 6th May 2012 12:44 PM Peter Daniel Pass Labs 140 18th February 2012 11:14 PM timwebb Car Audio 1 28th May 2010 04:05 AM metal Solid State 6 24th February 2004 03:05 PM

 New To Site? Need Help?

All times are GMT. The time now is 03:39 AM.

 Home - Contact Us - Advertise - Rules - diyAudio Store - Sponsors - Privacy Statement - Terms of Service - Top - Opt-out policy

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio
Wiki