Peak Inverse Voltage of a rectifier

[shaiqbashir]

Hi guys!

i want to ask you about the term

PEAK INVERSE VOLTAGE of a rectifier

what exactly it is??

and which one is good for us

Low Peak Inverse Voltage?
High Peak Inverse voltage?

[audioguru]

Hi Shaiq,
How much is the voltage of your mains? 230VAC?
Then its peak voltage is 230V times the root of 2= 325V. If you rectify it then the minimum peak inverse voltage rating of the rectifier is 325V, and you would probably use one rated for 400V or 500V to allow for spikes. A voltage that is higher than the rating will cause the rectifier to conduct when it should be blocking.

Sometimes the price of a rectifier diode determines which one to use for a lower voltage circuit. A 1N4001 is more expensive than a 1N4002, but the voltage rating of the cheaper one is higher. It is cheaper because it is more popular.

[shaiqbashir]

Thanks a lot Audioguru for ur help!

but actually im asking  you to tell me the Theory of Peak Inverse Voltage.

That what basically is this. I donot want to use it anywhere so plz dont ask me what my supply voltage etc.

Im just asking what is Peak Inverse Voltage itself??

How it affects the performance of a rectifier?

It is said that a full wave rectifier has a Low PIV then a half-wave and that is the reason why a full wave is better than a half wave. I ask you why a low PIV is better than a high PIV???

In addition to this, please tell me that what is the advantage of using a Bridge Rectifier over a full wave rectifier i.e. What is the property of a bridge rectifier that makes it preferable over a full -wave rectifier.

I shall be thankful to u for this act of kindness.

Good Bye!

[audioguru]

Im just asking what is Peak Inverse Voltage itself??

How it affects the performance of a rectifier?

It is just the voltage rating of the rectifier. It doesn't affect how well it rectifies.

It is said that a full wave rectifier has a Low PIV then a half-wave and that is the reason why a full wave is better than a half wave. I ask you why a low PIV is better than a high PIV???

A half-wave rectifier rectifies for half the amount of time as a full-wave rectifier. So the half-wave produces a lot of ripple voltage while its capacitor discharges. But the full-wave rectifier rectifies every peak of the wave so has much less ripple voltage. The PIV high voltage rating of the rectifiers has nothing to do with it.

In addition to this, please tell me that what is the advantage of using a Bridge Rectifier over a full wave rectifier i.e. What is the property of a bridge rectifier that makes it preferable over a full -wave rectifier.

I guess when you say "full-wave rectifier" you mean with a center-tapped transformer, so only two rectifier diodes are needed, instead of four needed for a full-wave bridge rectifier.
The two diodes each have a forward voltage loss of only about 0.8V while the full-wave bridge rectifier has two rectifier diodes in series for each half cycle resulting in a 1.6V loss. So the full-wave rectifier with two rectifier diodes is better than a rectifier bridge that has four rectifier diodes.

[shaiqbashir]

many thanks audioguru!

[berniedd]

Audioguru is right about the PIV of a rectifier should be higher than the peak inverese voltage of the AC wave it is connected to. Please note that in a half wave rectifier circuit WITH A CAPACITOR to act as an energy storage device to smooth out peaks and valleys in the rectified voltage, the PIV of the rectifier must withstand the peak voltage of the AC  wave PLUS the voltage stored in the capacitor. This is because in the next half wave of the AC where the rectifier is not conducting, the total reverse voltage impressed on the rectifier is the peak of the AC reverse voltage which is now in series with the charge stored in the capacitor (minus the small forward conducting voltage drop of the diode rectifier) .

[Sukhbinder]

i both agree and disagree with audio guru about the advantage of a 2 diode full wave rectifier over a 4 diode bridge. a 2 diode rectifier does have a lower forward volatge drop but the diodes must have a higher PIV rating. lets say we have a 60v ac input. in a 2 diode full wave rectifier we need a diode with a PIV greater than 85V (60xsquare root(2)), so u use a 100 PIV rating diode. if u used a 4 diode bridge circuit, the 85 volts are divided between the two series diodes (42.5 across each) so u can use a 50V PIV rating diode. a higher PIV rating diode will cost more. However these days as the diode costs are quite minimal u can always use a bridge instead of a 2 diode full wave rectifier due to some of its benifits like
1. u donot need a centre tap transformer for the bridge.
2. can be used on DC supply also for polarity protection.
3.dual power supplies need a centre tap tranformer and a Bridge rectifier.
4. if the transformer taps are not balanced (i.e. u have a 12-0-13 instead of a 12-0-12 transformer ( low quality transformers) the there will be a ripple of 1 voltage in  the final dc voltage which degrades the power supply. with a bridge rectifier there is no such problem.
5. the low cost of commercially available bridge rectifier modules has boosted their use.

[Sukhbinder]

Bridge rectifier has lower ripple factor than full wave rectifier ,

A bridge rectifier as the same ripple factor as a full wave rectifier. however it is easier to use as it does not require a centre tapped transformer. very usefull for converting 220V AC mains to DC ( as in Switched mode power supplies)

[oladiladio]

Peak reverse voltage or simply means how high the voltage can be over a reverse biased diode.

For instance, over a 1N4148 signal diode VRRM can be no higher than 100V. If you apply a higher voltage the junction will be damaged due to zener or avalanche effect.

Two ratings who are important for a rectifier are IF (forward current) and VR (reverse voltage).

As a non native English speaker I hope I've made myself clear.