Bridge Rectifiers: How Do They Work?

In summary, the conversation discusses the concept of full-wave bridge rectifiers and how they work. The author of the book mentions that the diodes D2 and D4 are forward biased, but there seems to be some confusion regarding the flow of current in the circuit. The circuit uses 4 diodes and 2 alligator clips attached to the leads of a 9v AC power adapter. It is pointed out that the book may have made a mistake with the labeling of the diodes, and it is suggested to swap the labels of D3 and D4. The conversation also touches on the concept of a load and how the current flows in the circuit. The book being referenced is Electronics for Dummies by Doug Lowe.
  • #1
Alex Hughes
54
13
Ok so I've been reading a book on electronics and I got to a section that talks about full-wave bridge rectifiers. This is the diagram the author gives:
IMG_0119 (2).jpg

In this diagram he says the D2 and D4 diode are forward biased. But, doesn't the current flow through D2, goes through the resistor, and then flows through D3 meaning that D2 and D3 are the ones that are foward bias in the up cycle and D1 and D4 are forward bias in the down cycle? Is this a typo or am I just misinterpreting the diagram.

My next question was for when I actually built the bridge rectifier on a breadboard. I used a 9v AC power adapter and it works. I used my multimeter and got an accurate DC reading so I'm confident I hooked the circuit up correctly. I'm just confused on how it works. Here is the circuit:
Breadboard_diagram.jpg

The circuit uses 4 diodes. The two alligator clips you see are attached to the leads of my 9v AC power adapter. To me it seems that when the positive current goes through the red alligator clip, it can't go through the diode which has its cathode (silver stripe) connected to B15 since it's reverse bias, instead it can only travel through the diode next to it, the one with its anode at D15. However, once it travels through it I see no place for the current to go. The diode whose cathode is connected to E9 is reverse bias, and the diode next to it is on a different row (cathode connected to A10 not A9). How does this bridge rectifier work? Can somebody please explain it to me I'm very confused. Thanks.
 

Attachments

  • IMG_0119 (2).jpg
    IMG_0119 (2).jpg
    57 KB · Views: 969
  • Breadboard_diagram.jpg
    Breadboard_diagram.jpg
    49.7 KB · Views: 1,123
Last edited:
Engineering news on Phys.org
  • #2
You are right.
Row 9 is the Positive, or +, output of the bridge.
Row 10 is the Negative, or -, output of the bridge.

The load (the resistor in the book) would connect from Row 9 to Row 10.

The book got it rather confused. The person writing the text and the person drawing the diagram didn't talk to each other and the editor didn't catch it.
In the drawing, you need to swap the D3 and D4 labels, then it all works out.
(The writer probably labeled the diodes going clockwise around the circuit, while the draftsman automatically considered the labelling as text and started a new line for the lower diodes.)

By the way, what book and what author is that. We like to be aware of such things so we can pay close attention to those publications in future questions. (when we remember!)

Cheers,
Tom
 
  • Like
Likes jim hardy, Averagesupernova, anorlunda and 1 other person
  • #3
Tom.G said:
You are right.
Row 9 is the Positive, or +, output of the bridge.
Row 10 is the Negative, or -, output of the bridge.

The load (the resistor in the book) would connect from Row 9 to Row 10.

The book got it rather confused. The person writing the text and the person drawing the diagram didn't talk to each other and the editor didn't catch it.
In the drawing, you need to swap the D3 and D4 labels, then it all works out.
(The writer probably labeled the diodes going clockwise around the circuit, while the draftsman automatically considered the labelling as text and started a new line for the lower diodes.)

By the way, what book and what author is that. We like to be aware of such things so we can pay close attention to those publications in future questions. (when we remember!)

Cheers,
Tom
Thanks a bunch Tom, that helped a lot. But, if the circuit doesn't have a load (such as a resistor connecting row 9 to row 10, then how does the current get back to the AC source. Doesn't current have to get back to the source in order to complete the circuit? In the diagram the book gave, if you removed the resistor that connected the positive and negative end of the bridge, it would be an incomplete circuit would it not? How does this differ than the circuit I created on my breadboard.
 
  • #4
Also, the book I'm reading is Electronics for Dummies by Doug Lowe
 
  • #6
Alex Hughes said:
if the circuit doesn't have a load (such as a resistor connecting row 9 to row 10, then how does the current get back to the AC source.
Without a load there is no current leaving the circuit, so there is none to get back to the circuit.

Here is a not-very-good description, but it often helps when first trying to get your brain wrapped around the initial concepts. If you turn off a water faucet no water comes out so there is no water to go down the drain to be recycled. There is still pressure in the pipe though (similiar to voltage in the circuit). As you get deeper into Electronics and Physics you will get much more detailed, and sometimes confusing, approaches to "what is really happenning."

Enjoy the journey!
Tom
 
  • Like
Likes jim hardy and Alex Hughes
  • #7
Alex Hughes said:
In the diagram the book gave, if you removed the resistor that connected the positive and negative end of the bridge, it would be an incomplete circuit would it not?
Yes it would be an incomplete, aka "open" , circuit.

Alex Hughes said:
How does this differ than the circuit I created on my breadboard.
It doesn't. You appear to have grasped the concepts .

Keep up the good work !
 
  • Like
Likes Alex Hughes

What is a bridge rectifier and what does it do?

A bridge rectifier is an electronic device used to convert alternating current (AC) to direct current (DC). It does this by using a series of diodes to block the negative portion of the AC signal, resulting in a smoother DC output.

How does a bridge rectifier work?

A bridge rectifier consists of four diodes arranged in a diamond shape. During the positive half of the AC cycle, two diodes conduct electricity and allow it to flow through to the output. During the negative half of the cycle, the other two diodes conduct, allowing the current to continue flowing in the same direction.

What are the advantages of using a bridge rectifier?

One of the main advantages of using a bridge rectifier is that it is a simple and inexpensive way to convert AC to DC. It also has a high efficiency, meaning very little energy is lost during the conversion process. Additionally, it has a compact design and can handle higher current and voltage levels compared to other rectifier circuits.

What are some common applications of bridge rectifiers?

Bridge rectifiers are used in a wide range of electronic devices, including power supplies, battery chargers, and audio equipment. They are also commonly used in household appliances such as televisions and computers.

What are some potential issues with bridge rectifiers?

One potential issue with bridge rectifiers is the production of high levels of heat, which can reduce their efficiency and lifespan. They may also produce ripple in the output voltage, which can cause interference in sensitive electronic devices. Additionally, if the diodes in the bridge rectifier are not properly rated, they can fail and cause the circuit to malfunction.

Similar threads

  • Electrical Engineering
Replies
10
Views
2K
  • Electrical Engineering
Replies
7
Views
794
  • Electrical Engineering
Replies
15
Views
1K
  • Electrical Engineering
Replies
14
Views
715
Replies
9
Views
1K
Replies
11
Views
2K
  • Engineering and Comp Sci Homework Help
Replies
7
Views
2K
  • Electrical Engineering
Replies
15
Views
2K
  • Electrical Engineering
Replies
10
Views
1K
Replies
21
Views
6K
Back
Top