Rectifier Circuits: Questions & Answers

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In summary, the conversation discusses confusions regarding rectifier circuits and the effects of changing load resistance on the DC voltage. The speaker also asks about calculating the capacitance needed for a smoothing capacitor and the behavior of the capacitor in each cycle of AC. The response provides a link to a helpful resource and mentions the importance of considering the potential for damaging a rectifier due to excess inrush charging a capacitor.
  • #1
daredevil
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I have some confusions regarding rectifier circuits.

I was wondering does any change happen to the rectified dc voltage if i change the load resistance. I was thinking even if the current change with the change in resistance, there should not be any change in the voltage. But, it seems it is not so..

And how do I calculate the capacitance of the smoothing capacitor I need.
 
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  • #2
And also, does the capacitor charge up completely and discharge completely in each cycle of AC irrelevant of the capacitance and the frequency of the AC signal..??

Thanks.
 
  • #3
daredevil said:
I have some confusions regarding rectifier circuits.

I was wondering does any change happen to the rectified dc voltage if i change the load resistance. I was thinking even if the current change with the change in resistance, there should not be any change in the voltage. But, it seems it is not so..

And how do I calculate the capacitance of the smoothing capacitor I need.

daredevil said:
And also, does the capacitor charge up completely and discharge completely in each cycle of AC irrelevant of the capacitance and the frequency of the AC signal..??

Thanks.

This page at Hyperphysics should help answer your questions:

http://www.google.com/imgres?imgurl...ltage+calculation&hl=en&gbv=2&tbm=isch&itbs=1

ripple9.gif
 
  • #4
The capacitor discharge plot given by berkeman is very important for an additional reason. The rectifier "ON" time per cycle is tON = T - tdis. The peak repetitive rectifier charging current is inversely proportional to this ON time, and can easily exceed the rectifier specs if the filter capacitor is too large.
 
  • #5
Bob S--
Just had to comment on your comment. It's funny--I've been 'into' electronics and circuit building for more than 40 years, and have constructed numerous power supplies for various items in that time without ever stopping to consider your point of potentially damaging a rectifier due to excess inrush charging a cap. Apparently through sheer luck, or the fact that I tend to over-design stuff, (or perhaps because I typically use inherently current-limited voltage regulators) I've never blown a diode that way. But, it is something I will keep well in mind going forward. Very good info!
 

1. What is a rectifier circuit?

A rectifier circuit is an electronic circuit that converts alternating current (AC) to direct current (DC). It is typically made up of diodes, which allow current to flow in only one direction, and a transformer to step down the voltage.

2. What are the different types of rectifier circuits?

There are three main types of rectifier circuits: half-wave, full-wave, and bridge. Half-wave rectifiers use only one diode and are the simplest type, while full-wave rectifiers use two diodes and produce a smoother output. Bridge rectifiers use four diodes and are the most efficient type.

3. What is the purpose of a smoothing capacitor in a rectifier circuit?

A smoothing capacitor is used in rectifier circuits to reduce the ripple in the output voltage. It stores electrical charge during the peaks of the AC input and releases it during the troughs, resulting in a more constant output voltage.

4. How do you calculate the output voltage of a rectifier circuit?

The output voltage of a rectifier circuit depends on the type of circuit and the input voltage. For a half-wave rectifier, the output voltage is equal to the peak voltage of the AC input. For a full-wave rectifier, the output voltage is approximately 1.4 times the peak voltage of the AC input. For a bridge rectifier, the output voltage is approximately 1.4 times the peak voltage of the AC input minus two diode drops.

5. What are some common applications of rectifier circuits?

Rectifier circuits are commonly used in power supplies for electronic devices, such as phones, computers, and televisions. They are also used in electric motors, battery chargers, and other devices that require DC power. Additionally, rectifier circuits are used in various industrial and commercial applications, such as welding machines and DC motor drives.

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