All About Circuits Forum Can two bridge rectifiers with varying voltages be connected in parallel?
 Register Blogs FAQ Members List Today's Posts Search Today's Posts Mark Forums Read

 General Electronics Chat Discussion forum for general chat about anything electronics related, including asking questions about material in the All About Circuits E-book, Worksheets, and Videos.

#1
11-26-2010, 06:31 AM
 b2386 Junior Member Join Date: Feb 2010 Posts: 13
Can two bridge rectifiers with varying voltages be connected in parallel?

I have two different AC voltage sources that produce randomly varying AC voltages from 2-3 volts (not necessarily in unison). I have a basic bridge rectifier circuit connected to each voltage source. Assuming no voltage drop across the bridge rectifiers, I will have two DC voltage outputs varying from 2-3 volts. Can I put these two DC voltages in parallel?
#2
11-26-2010, 03:30 PM
 retched Senior Member Join Date: Dec 2009 Location: Baltimore, MD Posts: 5,198 Blog Entries: 14

Why would you assume no voltage drop across the bridge rectifiers?

You should most DEFINITELY count on voltage drop, especially at such small voltages.

You are going to lose 1.4 or more volts across each bridge.

As for paralleling 2 different voltages, no you can't. They will fight.

You might consider a summing amplifier to add the two voltages together.

You really need to get the current into the equation. That will affect the voltage drop across the bridges also.

You may need to sum them to get a usable voltage.
__________________
-rm-
#3
11-26-2010, 03:57 PM
 SgtWookie Expert Member Join Date: Jul 2007 Location: In the vast midwest of the USA; CST Posts: 22,039

How much current are you expecting from your AC voltage sources?

To minimize the voltage drop across the bridge, consider using Schottky diodes rated for the expected current. For even less voltage drop, consider synchronous rectification, where MOSFETs are used as "ideal diodes".

If you connect the two outputs in parallel, you will likely have problems. If you connect them in series, you will be OK.
__________________
General info:
If you have a question, please start a thread/topic. I do not provide gratis assistance via PM nor E-mail, as that would violate the intent of this Board, which is sharing knowledge ... and deprives you of other knowledgeable input.
#4
11-26-2010, 04:43 PM
 b2386 Junior Member Join Date: Feb 2010 Posts: 13

lol, the reason I said assume no voltage drop was only because it's effect was not really relevant to my original question of could these two DC voltages be connected in parallel. I am using schottky diodes so the actual voltage drop will be around 0.5V in total.
#5
11-26-2010, 04:45 PM
 retched Senior Member Join Date: Dec 2009 Location: Baltimore, MD Posts: 5,198 Blog Entries: 14

So are you set? Or did you need further clarification?
__________________
-rm-
#6
11-26-2010, 05:40 PM
 b2386 Junior Member Join Date: Feb 2010 Posts: 13

I think I got it. If I put two or more of these rectifiers in parallel, the smoothing capacitors of each rectifier will be in parallel and at any given time, the capacitors at a higher voltage will begin charging the capacitors at a lower voltage. I am assuming this is not what I want.

On a side note, let's say I have ten of these AC voltage sources described in my previous post. They have random phases so summing before rectification is not really an option. What are my options for getting a 3V DC output voltage from this entire system? I can't use transistors...
#7
11-26-2010, 07:49 PM
 tom66 Senior Member Join Date: May 2009 Location: Basingstoke, UK Posts: 2,613

What will happen is the AC input with a higher voltage will provide almost all of the current; it will effectively choose the maximum between two sets of voltages. See image. The two demo waveforms are 45 degrees out of phase.

Code:
```\$ 1 5.0E-6 10.20027730826997 53 5.0 50
d 464 240 528 176 1 0.805904783
d 400 176 464 112 1 0.805904783
d 400 384 464 320 1 0.805904783
d 464 448 528 384 1 0.805904783
w 464 288 576 288 0
w 576 80 464 80 0
w 464 80 464 112 0
g 464 240 464 256 0
w 576 288 576 80 0
d 464 240 400 176 1 0.805904783
d 528 176 464 112 1 0.805904783
d 464 448 400 384 1 0.805904783
d 528 384 464 320 1 0.805904783
w 464 320 464 288 0
g 464 448 464 464 0
w 528 384 560 384 0
w 400 384 368 384 0
w 368 384 368 512 0
w 560 384 560 512 0
v 368 512 560 512 0 1 40.0 5.0 0.0 0.0 0.5
w 576 288 656 288 0
r 656 288 656 368 0 100.0
g 656 368 656 384 0
v 368 48 560 48 0 1 40.0 5.0 0.0 0.7853981633974483 0.5
w 560 48 560 176 0
w 368 48 368 176 0
w 368 176 400 176 0
w 528 176 560 176 0
o 20 64 0 34 5.0 0.025 0 -1
o 23 64 0 35 10.0 0.05 1 -1
o 19 64 0 35 10.0 0.1 2 -1```
Select All

This can be expanded to many bridges. Due to how diodes work, it will work like an N-input OR gate.
Attached Images
 Screenshot-Circuit Simulator v1.5m-1.png (17.7 KB, 10 views)

 Tags bridge, connected, parallel, rectifiers, varying, voltages

 Related Site Pages Section Title Worksheet Basic AC-DC power supplies Worksheet Rectifier circuits Textbook AC bridge circuits : Ac Metering Circuits Textbook AC voltmeters and ammeters : Ac Metering Circuits Textbook The Silicon-Controlled Rectifier (SCR) : Thyristors Video Lecture Power Supplies - Applications - Diodes and Diode Circuits Textbook Vacuum tube audio amplifier : Discrete Semiconductor Circuits Textbook Rectifier/filter circuit : Discrete Semiconductor Circuits Textbook Half-wave rectifier : Discrete Semiconductor Circuits Textbook Rectifier circuits : Diodes And Rectifiers

 Similar Threads Thread Thread Starter Forum Replies Last Post Ele General Electronics Chat 5 03-06-2010 08:26 PM cardiology General Electronics Chat 1 02-11-2010 04:24 PM richeek.arya General Electronics Chat 21 11-10-2009 08:00 PM TO2 General Electronics Chat 7 06-20-2009 11:49 AM mckaype The Projects Forum 1 06-01-2006 06:52 AM

 Thread Tools Display Modes Linear Mode

 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 Electronics Forums     General Electronics Chat     The Projects Forum     Homework Help     Electronics Resources Software, Microcomputing, and Communications Forums     Programmer's Corner     Embedded Systems and Microcontrollers     Computing and Networks     Radio and Communications Circuits and Projects     The Completed Projects Collection Abstract Forums     Math     Physics     General Science All About Circuits Commmunity Forums     Off-Topic     The Flea Market     Feedback and Suggestions

All times are GMT. The time now is 11:35 PM.