5 Things to Know Before Buying high voltage diode

I read atleast 3 or 4 topics about diodes but in none of them actually I found something useful.
I just want to have a diode. Common diode
I will be using it sometimes for rectification (max 24V), as a flywheel (for reverse motor shitty things) and for similar things that just require something to prevent for wrong placed "+" and "-" wires. I read about 1N and did a google search plus I viewed its datasheet, but it says that there are "stronger" diodes - 1N to 1N... And I got confused...
So would you please suggest me a proper diode? Thanks in advance.

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The two most important specs are forward current and reverse voltage. I usually buy a higher voltage version (1N) since they don't cost much more and I'm usually buying more than I need so I don't know what I'll be using them for.

As a flyback (or flywheel) application the (peak) current through the diode will be the same as the current through the motor/coil, and the reverse voltage will be the applied voltage.* (So, in most low-voltage applications, voltage isn't an issue and you just have to check the current.)

I will be using it sometimes for rectification (max 24V)

When I'm building a power supply I usually use a [u]bridge rectifier[/u] which is 4 diodes in one package. I may have made a bridge from 4 1N's, but I don't remember. With a single diode, the power is "off" for half of the AC cycle which means you get more ripple (or you have to use a bigger capacitor) and you can only get half the current.

Or, if you have a center-tapped transformer you can get full-wave rectification with two diodes.

The forward voltage across a standard silicon diode is about 0.7V (depending on current) and in some applications where you want a smaller voltage drop, you can use a Schottky diode. Schottky diodes also switch faster than standard silicon diodes so they are sometimes used in high-frequency circuits.

• When you disconnect an inductor/coil you get a high-voltage kick (back EMF). But, since the diode is "backwards", that back EMF becomes the forward voltage across the diode. That "kills" the high-voltage kickback, and your diode never sees high voltage.

It depends what you want to do. Most of the time it is probably not so important. If you have supply voltage 20V or more it is not so important if the diode drops 0.7 or 0.3V. If motor needs 1A you don't care if diode leakage is 1mA or 10uA. If you want something more delicate such as reverse voltage protection difference between normal and Schottky diode may be more important if the battery voltage is close to your intended operating voltage. OTOH if you build some analog circuit "large" leakage current of Schottky may cause problems.

Another important spec - diodes rated for large current are also large - they have thick leads and they are difficult to stick into solderless breadboard. I even got diodes too thick to fit into hole in protoboard.

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Semiconductor diodes are widely used components in many electronic circuit designs. Different diode types are optimized to provide different characteristics exploited in circuit designs. An important function of diodes is for rectification.

Half wave rectifier circuits are used for power rectification, signal demodulation and peak detection while two-diode circuits provide full wave rectification when used with a center-tapped transformer. Today, the two-diode rectifier circuit is not as commonly seen as four-diode bridge rectifiers that can be constructed with or without a transformer which greatly reduces cost for the circuit.

With that, three diode considerations for rectifier circuits are as follows:

1) Turn on Voltage

The typical turn on, or forward voltage of a silicon diode is 0.7V while that of a germanium diode is around 0.2-0.3V. Reducing the forward voltage drop increases the diode rectifier sensitivity which is relevant in certain applications such as signal detection.

2) Diode Current Rating

The amount of load current that flows through a diode determines the desired continuous current rating. For example, if the load draws 1A of current then a 1N diode (rated 1A) will suffice (though without a safety margin!) However, if the load current is more than 1A, then a diode with a higher current rating is required. The load current must not exceed the continuous current diode rating. The same can be considered for the supply current. If the design requires a 3A power supply, the diode should be able to handle 3A of current. The supply current should never exceed the diode current rating, even if only momentarily.

3) Peak Inverse Voltage

The diodes must withstand the peak inverse voltage across them. When a capacitor smooths the output, the voltage value is the peak of the input waveform, which is '2 times the RMS voltage.

On the other half of the wave cycle, the peak voltage value is another '2 times the RMS voltage. The sum of the two values is the maximum inverse voltage across the diode. Thus the PIV diode rating should be at least 2 x '2 times the input RMS voltage for half wave rectifier circuits and at least four times the peak transformer voltage for two-diode full wave rectifier circuits, accounting for possible transients.

In bridge rectifiers, diodes with half the PIV rating of those in a center-tapped rectifier are required for the same output voltage.

Considering these three important specifications will ensure that a diode will function as a rectifier without damaging them or the rest of the project that this is in.

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