Why is the average rectification current of a diode with a small junction area small and the highest

BecauseDiodesThe larger the cross-sectional area, the greater the allowable current, because the allowable current per unit cross-sectional area of the diode is certain. The maximum operating frequency of a diode is determined by its junction capacitance, the larger the junction capacitance, the smaller the operating frequency, and the smaller the junction capacitance, the greater the operating frequency.

The current directivity of most diodes is often referred to as "rectifying". The most common function of a diode is to allow only current to pass through a single direction (known as forward bias) and to block it in reverse direction (known as reverse bias). Therefore, the diode can be thought of as an electronic version of the check valve.

Feature analysis. Inside the semiconductor diode there is a p-n junction.

Two lead terminals.

These electronic devices have the ability to transduce a unidirectional current in the direction of the applied voltage. Generally speaking, a crystal diode is a p-n junction interface formed by the sintering of p-type semiconductors and n-type semiconductors.

A space charge layer is formed on both sides of its interface, which constitutes a self-built electric field. When the applied voltage is equal to zero, due to the p-n junction carriers on both sides.

The diffusion current caused by the concentration difference and the drift current caused by the self-built electric field are equal and in an electrically balanced state, which is also a diode characteristic under normal conditions.

The production process is different, and the way of ion mixing is different; One is the "diffusion method" and the other is the "epitaxy method".

The junction capacitance is smaller if the junction area is smaller, so the operating frequency is high. The small junction area is equivalent to the thin wire, so it can only be used for small current operation.

Maximum rectifier current: diode.

The number of weighing stages during long-term operation, the maximum forward current that is allowed to flow through. Due to the fact that the head current flows through the p-n junction.

When the current is too large, the heat exceeds the limit and burns the acacia, which will burn the PN knot to burn out. The larger the rectifier current, the larger the volume of the transistor

Because the maximum rectification current of a crystal diode is fixed as soon as it is produced, there is no such thing as "bigger is better". If the rectifier current is larger, it can burn out if it exceeds its limit.

If the diode is rectified, if the model is uncertain, the installation volume is not considered, the capacitance capacity is not considered, the rectifier recovery time is not considered, the working frequency is not considered, and the reverse withstand voltage is not considered, the larger the rated current of the rectifier at this time, the better.

It must depend on the specific circuit, for example, the current itself is very small, there is no need, waste of cost, waste of space.

The larger the maximum rectifier current, the larger the installation volume and the more expensive it is, and it may not necessarily meet your requirements for renting a mountain file.

The best is to meet the requirements of design and disorderly use, as long as it is enough.

No, it's enough. The selection of high-current diodes is large in size and expensive, but it is cumbersome.

The greater the maximum rectification current of the net diode, the better, why is it wrong? This statement is false.

Crystaldiode: Semiconductor terminal devices in solid-state electronic devices. These devices are primarily characterized by a nonlinear current-voltage mid-range history.

The rectifier average current i of a diode with a small junction area is small because the rectifier average current is equal to the current density multiplied by the junction area; The highest operating frequency f is high because of the small junction capacitance.

Point-contact diodes are formed by pressing a metal pin on a single wafer made of germanium or silicon and then passing the galvanic method. Therefore, the capacitance of the p-n junction is small, making it suitable for high-frequency circuits. However, compared to the surface junction type, the forward and reverse characteristics of the point-contact diode are poor, so they cannot be used for high currents and rectification.

Because of the simple construction, it is cheap. It is a type with a wide range of applications for general purposes such as detection, rectification, modulation, mixing, and limiting of small signals.

There are two reasons for the capacitance of PN junction: first, the change of applied voltage causes the change of the width of the space charge region, that is, the charge of the depletion layer changes with the change of the applied voltage, this phenomenon is similar to the charging and discharging process of the capacitor, and the resulting capacitance is called barrier capacitance CBTwo:

When the p-n junction is in equilibrium, both the holes that diffuse from the p-region to the n-region and the free electrons that diffuse from the n-region to the p-region are called non-equilibrium fewtons. When the forward voltage is applied, the concentration of non-equilibrium few is high near the interface of the depletion layer, while the concentration is low at the distance from the interface, and the concentration gradually decays from high to low until zero. A certain concentration gradient (i.e., concentration difference) is formed, resulting in a diffusion current that also varies with the applied voltage.

In this way, in the diffusion zone, the process of charge accumulation and release is the same as that of the capacitor, and the resulting capacitance is called the diffusion capacitance cdJunction capacitance of pn junction cj = cb+ cd.

From the above analysis, it can be seen that the smaller the cross-sectional area of the diode, the smaller the amount of electricity stored and the smaller the junction capacitance that may be generated. According to the capacitive reactance zc=1 c 1 2 fc, when f is constant, the smaller the cross-sectional diode, the larger the capacitive reactance will be because c is smaller. According to Ohm's law, the larger the capacitive reactance of the ZC UC IC, the smaller the current passing through its cross-section.

For a certain PN junction with a certain capacitive response to Zc, according to the capacity for Zc 1 2 Fc, when C is smaller, F is larger.

We can also directly follow the capacitance formula c s d of parallel plate capacitors, the smaller the positive area, the smaller the capacitance. Therefore, the capacitance c of the capacitor with a small cross-sectional area is small, and then according to the formula Zc=1 C 1 2 Fc and Ohm's law, it is known that the current through the PN junction with a small cross-sectional area is small and the maximum operating frequency is high.

That's right. The diode will be damaged if the operating frequency is greater than the maximum operating frequency. The overcurrent does not exceed 150%, and it will not be damaged in a short time, but it will cause damage due to high junction temperature for a long time.

If the working frequency of the diode is not too much greater than the nominal frequency, it will also cause the temperature junction temperature to be too high, and it will not be damaged or cause soft damage in a short time, and the performance will deteriorate. Maximum forward current:

ifm refers to the maximum forward current that a diode can withstand. The actual current passing through should be less than this parameter. This is a data that is artificially prescribed for the proper operation of the diode.

Maximum Operating Current: This parameter name is not available. Maximum Reverse Voltage:

URM refers to the reverse voltage that does not cause diode breakdown, and the peak value of the working voltage cannot exceed URM, otherwise the reverse current will increase, the rectification characteristics will deteriorate or even burn the diode. This is a data that is artificially prescribed for the proper operation of the diode.

The diode has a parameter called breakdown voltage: UB, which refers to the voltage that causes the reverse current of the diode to increase sharply and dramatically, resulting in a breakdown voltage, which is a property of the diode itself and is "innate". UB is generally twice as large as the URM and <>

My understanding is that the maximum rectification current of the diode refers to the DC current after rectification, and the DC current is generally used as the "average value".

Instead of "valid value", this is because it is defined as:

In a certain period of time, the current (or voltage) value is continuously collected and accumulated at equal intervals, and its cumulative value is divided by the number of collections, and its quotient is the average value of the current (or voltage)".

It is suitable for the metering of direct current, whether constant or pulsating, it can be used to measure the magnitude of current (or voltage).

But the average does not apply to alternating current, for the following reasons; The alternating current is a sine wave, that is, the change of its current value in the positive and negative half waves is equal in magnitude and opposite in the direction, so its average value = 0;However, alternating current can do work just like direct current, so what is used to measure the size of alternating current? This brings us to the concept of "effective value"; RMS = maximum for AC current.

Therefore, the main reason is that the maximum rectification current of the diode refers to the DC current after rectification, so the "average value" is used, not the AC current before rectification (the effective value should be used).

Go to the electronics market There are definitely high-current diodes Ask about voltage and current Diodes are divided into voltages, 50v, 100v, 200v, etc.

The voltage drop of the diode is around the right, you can use ZP (2CZ) series 5--5000A, and the iron seal should add a heat sink.

2 x 20A aluminum shell full bridge in parallel,

Hehe! You can buy this at the electronic accessories store, not to mention 20A is hundreds of A, and the voltage drop is there.

Maximum rectification current: The maximum forward current that is allowed to flow through the diode during long-term operation. Since the current flows through the PN junction, it will generate heat, and when the current is too large, the heat generation exceeds the limit, and the PN junction will burn out.

Every time the bridge rectification works, it is a string of two diodes. Therefore, it is 1 2 of the load current, and the bridge rectification is connected in series with two diodes, so its withstand voltage can be selected as a lower diode.

Bridge rectifiers are the most commonly used circuits that use the unidirectional conductivity of diodes for rectification, and are commonly used to convert alternating current to direct current. The circuit diagram is as follows:

I thought that two of them were turned on per cycle, and these two were connected in series, so it was 1/2!