Rectifying diode  is a diode based on a semiconductor material, which is designed to convert alternating current  in the permanent. True, this function does not exhaust the scope of these radio components: they are used for commutation, in high-current circuits, where there is no rigid regulation of the time and frequency parameters of the electrical signal.

Classification

According to the value forward current, which is the maximum permissible, the rectifier diode can have a small, medium and large power:

• small - rectify direct current up to 300 mA;
• rectifying diodes of medium power - from 300 mA to 10 A;
• large - more than 10 A.

Germanium or silicon

According to the materials used, they are silicon and germanium, but more widely used silicon rectifier diodes due to their physical properties.

Their reverse currents are several times smaller than in germanium ones, while the voltage is the same. This makes it possible to achieve very high permissible reverse voltages in semiconductors, which can be up to 1000-1500 V. In germanium diodes, this parameter is in the range of 100-400 V.

Silicon diodes are capable of operating in the temperature range from -60 ºС to +150 ºС, and germanium ones - only from -60 ºС to +85 ºС. This is because when the temperature becomes higher than 85 ° C, the number of electron-hole pairs formed reaches such values ​​that the reverse current sharply increases, and the rectifier ceases to work effectively.

Manufacturing technology

The rectifier diode by design represents a plate of a semiconductor crystal in whose body there are two regions having different conductivity. This was the reason that they are called planar.

Semiconductor rectifier diodes are made as follows: on the region of a semiconductor crystal having an n-type conductivity, aluminum, indium or boron melts, and phosphorus is melted on the region of a p-type crystal.

When exposed to high temperatures, these two substances are firmly fused with the semiconductor substrate. In addition, the atoms of these materials diffuse into the crystal with the formation in it of a region with predominantly electronic or hole conductivity. As a result, a semiconductor device is formed, which has two regions with different types of electrical conductivity, and between them a p-n junction is formed. This is the principle of operation of the vast majority of planar diodes made of silicon and germanium.

Design

In order to organize protection against external influences, as well as to achieve reliable heat dissipation, a crystal having a p-n junction is mounted in the housing.
  Diodes having low power are produced in a plastic housing, provided with flexible external terminals. Rectifying diodes of medium power have a metal-glass case already with rigid external terminals. Details of high power are housed in a casing of metal or cermets.

Silicon or germanium crystals with a p-n-junction are soldered to a crystal holder, which simultaneously serves as the base of the housing. To him, the body is welded, having a glass insulator through which one of the electrodes is withdrawn.

Low-power diodes, which are relatively small in size and weight, have flexible terminals, through which they are mounted in circuits.

Since the currents with which medium power semiconductors and powerful rectifying diodes work, they reach significant values, their conclusions are much more powerful. The lower part of them is made in the form of a massive base, heat-removing, equipped with a screw and an outer surface of a flat shape, which is designed to provide reliable thermal contact with an external radiator.

Characteristics

Each type of semiconductor has its own working and limit parameters, which are selected in order to ensure operation in any scheme.

Rectifier diodes parameters:

• I straight max  - direct current, which is maximum permissible, A.
• U reverse max  - reverse voltage, which is maximum permissible, V.
• I return  - return current is constant, μA.
• U straight  - direct voltage is constant, V.
• Operating frequency, kHz.
• Working temperature, FROM.
• P max  - Power dissipated on the diode, which is maximum permissible.

The characteristics of rectifier diodes are far from being exhausted by this list. However, they are usually sufficient to select a part.

The scheme of the simplest rectifier of alternating current

Consider how the circuit works (the rectifier diode plays the main role in it) of the primitive rectifier.

On its input is supplied a network alternating voltage with positive and negative half-periods. The load is connected to the output of the rectifier (R software), and the diode (VD) performs the function of the rectifying element.

The positive half-periods of the voltage coming to the anode cause the diode to open. At this time through it, and therefore through the load (R of the load), which is fed from the rectifier, a direct current flows (I straight).

The negative half-periods of the voltage arriving at the anode of the diode cause its closing. A small reverse current of the diode (I sample) flows through the circuit. Here the diode cuts off the negative half-wave alternating current.

As a result, it appears that through the load connected to the network (R software), through the diode (VD), now a pulsating, not alternating current of one direction passes. After all, it can only take place in positive half-cycles. This is the meaning of rectification of alternating current.

However, such a voltage can only supply a low-power load that is powered by an alternating current network and does not impose serious power requirements, for example, incandescent lamps.

The lamp will only pass the voltage when passing positive pulses, as a result of which the electrical appliance undergoes weak flickering, which has a frequency of 50 Hz. However, due to the fact that the thread is subject to thermal inertia, it can not cool down completely in the intervals between the pulses, which means that the flickering will be almost invisible.

In the event that such a voltage is applied to an amplifier or power receiver, a sound will be heard in the loudspeaker low frequency  50 Hz), which is called the alternating current background. This effect is due to the fact that the pulsating current during the passage through the load induces in it the pulsating voltage generating the background.

Such a disadvantage is somehow eliminated if a filter capacitor (C filter) is connected in parallel with the load, the capacitance of which is sufficiently high.

The capacitor will be charged with current pulses at positive half-cycles, and discharged through the load (R-load) in negative half-cycles. With sufficient capacitor capacitance  for the time that passes between the two current pulses, it will not have time to fully discharge, and consequently the current will constantly be present on the load (R load).

But even such a relatively smooth current should also not load the load, because it will continue to fade, because the magnitude of pulsations (U pulse.) Is still quite serious.

disadvantages

In the rectifier, whose work we just dismantled, only half of the AC waves are used to advantage, and as a result, more than half of the input voltage is lost on it. This kind of rectification of alternating current was called half-wave, and rectifiers, which use this type of rectification, are called half-wave. Disadvantages of half-wave rectifiers have been successfully eliminated in rectifiers using a diode bridge.

Diode bridge

The diode bridge is a compact circuit that is made up of four diodes, and serves the purpose of converting AC to DC. The bridge circuit makes it possible to pass a current in each half-cycle, which distinguishes it from the half-wave period. Diode bridges are made in the form of assemblies of small size, which are enclosed in a plastic case.

At the output of the case of such an assembly there are four terminals with the notation "+", " — " or " ~ ", Indicating the appointment of contacts. However, diode bridges are not found in the assembly, they are often assembled directly printed circuit board  by including four diodes. The rectifier, which is performed on a diode bridge, is called full-wave.

A rectifier diode is a device that conducts current only in one direction. Its design is based on one p-n junction and two pins. The rectifier diode changes the alternating current to a constant one. In addition, rectifier diodes are widely practiced in voltage multiply circuits, circuits where there are no strict requirements for signal parameters in time and frequency.

• Principle of operation
• Basic Device Settings
• Rectifier circuits
• Pulse devices
• Imported devices

Principle of operation

The principle of operation of this device is based on features of p-n  transition. Near the transitions of two semiconductors there is a layer in which there are no charge carriers. This is the barrier layer. His resistance is great.

When a certain external alternating voltage is applied to the layer, its thickness becomes smaller, and subsequently disappears altogether. The current that increases is called the direct current. It passes from the anode to the cathode. If the external alternating voltage will have a different polarity, then the barrier layer will be larger, the resistance will increase.

Types of devices, their designation

By design distinguish devices of two types: point and planar. In industry, the most common are silicon (designation - Si) and germanium (designation - Ge). The first working temperature is higher. The advantage of the second is a small voltage drop with direct current.

The principle of designating diodes is an alphanumeric code:

• The first element is the designation of the material from which it is made;
• The second defines a subclass;
• The third designates the working capacity;
• The fourth is the ordinal number of the development;
• The fifth is the designation of the sorting by parameters.

The current-voltage characteristic of the rectifier diode can be represented graphically. It can be seen from the graph that the current-voltage characteristic of the device is nonlinear.

In the initial quadrant of the current-voltage characteristic, its direct branch reflects the highest conductivity of the device when a direct potential difference is applied to it. The reverse branch (third quadrant) of the I-V characteristic reflects the situation of low conductivity. This occurs with an inverse potential difference.

Real volt-ampere characteristics are subject to temperature. As the temperature rises, the direct potential difference decreases.

From the graph of the current-voltage characteristic it follows that at low conductivity the current through the device does not pass. However, for a certain value of the reverse voltage, avalanche breakdown occurs.

The current-voltage characteristic of silicon devices differs from germanium ones. The I-V characteristics are given depending on different ambient temperatures. The reverse current of silicon devices is much less than the analogous parameter of germanium ones. It follows from the I-V diagrams that it increases with increasing temperature.

The most important property is the sharp asymmetry of the I-V characteristic. With forward bias - high conductivity, with the reverse - low. This property is used in rectifiers.

Analyzing the instrument characteristics, it should be noted: such quantities as the rectification coefficient, resistance, capacity of the device are taken into account. These are the differential parameters.

The rectification factor reflects the quality of the rectifier.

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The rectification factor can be calculated. It will be equal to the ratio of the direct current of the device to the inverse. Such a calculation is acceptable for an ideal device. The value of the rectification coefficient can reach several hundred thousand. The bigger it is, the better the rectifier does its job.

Basic Device Settings

What are the parameters characterizing the devices? Basic parameters of rectifier diodes:

• The greatest value of the average forward current;
• The maximum permissible value of the reverse voltage;
• The maximum permissible frequency of the potential difference for a given direct current.

Based on the maximum value of the forward current, the rectifier diodes are divided into:

• Low-power devices. They have a forward current of up to 300 mA;
• Rectifying diodes of medium power. Range of change of direct current from 300 mA to 10 A;
• Power (high power). The value is more than 10 A.

There are power devices that depend on the shape, material, type of installation. The most common of these are:

• Power devices of medium power. Their technical specifications  allow working with voltage up to 1.3 kilowatt;
• Power, high power, able to transmit current up to 400 A. These are high-voltage devices. There are different bodies of performance power diodes. The most common are the whip and tablet form.

Rectifier circuits

Schemes for the inclusion of power devices are different. To rectify the mains voltage, they are divided into single-phase and multiphase, half-wave and full-wave. Most of them are single-phase. The construction of such a half-wave rectifier  and two voltage curves in the time diagram.

The alternating voltage U1 is applied to the input (figure a). On the right in the graph it is represented by a sinusoid. The state of the diode is open. The current flows through the load RH. In the negative half-cycle, the diode is closed. Therefore, only a positive potential difference is applied to the load. In Fig. в its time dependence is reflected. This potential difference is valid for one half-cycle. Hence the name of the scheme.

The simplest two-half-wave circuit consists of two half-wave circuits. For such a rectification design, two diodes and one resistor are sufficient.

Diodes pass only a positive AC wave. The disadvantage of the design is that in the half-cycle, the variable potential difference is removed only from half the secondary winding of the transformer.

If the design uses four efficiency instead of two diodes, the efficiency will increase.

Rectifiers are widely used in various industries. A three-phase device is used in automotive generators. And the use of the inventive alternator reduced the size of this device. In addition, its reliability has increased.

In high-voltage devices, high-voltage poles are widely used, which are composed of diodes. They are connected in series.

Pulse devices

The impulse is a device whose time of transition from one state to another is small. They are used to work in impulse circuits. From their rectifier counterparts such devices differ small p-n  transitions.

For instruments of this class, in addition to the parameters indicated above, the following should be attributed:

• Maximum impulse direct (reverse) voltages, currents;
• The period of setting the forward voltage;
• Period of recovery of the resistance of the device.

In high-speed pulse circuits, Schottky diodes are widely used.

Imported devices

Domestic industry produces a sufficient number of devices. However, today the most demanded import. They are considered more qualitative.

Imported devices are widely used in TV and radio circuits. They are also used to protect various devices when the connection is incorrect (wrong polarity). The number of types of imported diodes is diverse. A full-fledged alternative replacement for domestic ones does not yet exist.

There are many devices and devices that convert electricity. We suggest to consider what are rectifying diodes of high power and medium, their operation principle, as well as characteristics and application.

Description of rectifier diodes

Rectifier electric diode  high and medium power (microwave) is a device that allows the electric current to move only in one direction, mainly it is used to operate a certain power source. Rectifier diodes can process a higher current than conventional conductors. As a rule, they are used to convert AC to DC, the frequency of which does not exceed 20 kHz. The scheme of their work is as follows:

Photo - Principle of operation of a rectifying diode

Many electrical devices need these discrete components because they can act as integrated circuits. The most common rectifier high-power diodes  are made of silicon, so that their PN transition surface is quite large. This approach ensures an excellent current transfer, while ensuring no shortages or swings.

Photo - Rectifier diodes Rectifying diodes

Silicon semiconductor rectifiers, tube thermionic diodes are manufactured using compounds such as copper or selenium oxide. With the introduction of semiconductor electronics, rectifiers such as vacuum tubes with a metal base are obsolete, but still their analogues are used in audio and tele-equipment. Now, to power devices from very low to very high current, semiconductor diodes of various types (high-speed blocks, foreign germanium devices, domestic tablet-making devices, Schottky diodes, etc.) are mainly used.

Other devices that are equipped with control electrodes, where a simpler rectification method or alternating output voltage is required (for example, for welding machines) use more powerful rectifiers. This can be silicon or germanium devices. These are thyristors, zener diodes or other controlled switching solid state switches that function as diodes, passing current in only one direction. They are used by industrial electronics, they are also widely used for engineering electrical engineering, welding or monitoring the operation of current transmission lines.

Photo - Rectifying diode and cathode with anode

Types of standard rectifiers

There are various power rectifier semiconductor diodes, depending on the type of installation, material, shape, number of diodes, the level of the transmitted current. The most common are:

1. Medium power devices that can transmit a current of power from 1 to 6 amps. At the same time, the technical parameters of most devices say that such diodes can change the current with a voltage of up to 1.3 kilowatts;
2. Rectifier diodes of the maximum series can transmit current from 10 amperes to 400, they are mainly used as ultrafast converters, to control the industrial field of activity. These devices are also called high voltage;
3. Low-frequency diodes or low-power ones.

Before buying any type of device of this type, it is very important to choose the right parameters of rectifier diodes correctly. These include: characteristics of the I-V characteristic (maximum reverse current, peak peak current), maximum reverse voltage, forward voltage, housing material, and average rectified current

We provide a table where you can, depending on your needs, select the type of diode. The specifications  can be changed at the request of the manufacturer, so check the seller's information before purchasing.

Photo - Low-frequency diodes table

Imported (foreign) rectifier diodes (type KVRS, SMD):

Photos - Table of import diodes

Data on power or high-frequency diodes:

Photos - Power diodes

Rectifier circuits for inclusion are also different. They can be single-phase (for example, automobile and avalanche diodes) or multiphase (three-phase ones are considered the most popular ones). Most low-power rectifiers for domestic equipment are single-phase, but three-phase is very important for industrial equipment. For generator, transformer, machine tools.

However, for an uncontrolled bridge three-phase rectifier  Six diodes are used. Therefore, it is often called a six-diode rectifier. Bridges are considered impulsive and able to normalize and straighten even an unstable current.

For low-power devices ( charger), the double diodes connected in series with the anode of the first diode are also connected to the cathode of the second diode and are made in a single housing. Some commercially available dual diodes have access to all four terminals that can be customized to their needs.

Photo - Medium power rectifier diode

For higher power, one discrete device typically uses each of the six bridge diodes. It can be used both for surface equipment and for monitoring more complex devices. Often six-diode bridges use restrictive schemes.

Video: Principle of operation of diodes

Marking of rectifier diodes

Depending on the design and purpose, the rectifier diodes are marked as follows:

Based on such data, we have the following transcripts:

CD - pulse or rectifying diode silicon version;

KC - silicon blocks of rectifying type.

Before you buy a rectifier diodes in Kharkov, Moscow and any other cities, be sure to clarify the reference characteristics of sales consultants.

Diodes reference book

These are electronic devices with one p-n transition  They have one-sided conductivity and are designed to convert an alternating voltage into a constant one. The frequency of the rectified voltage as a rule does not exceed 20 kHz. Rectifier diodes are also Schottky diodes.

The main parameters of low-power rectifying diodes at normal temperature are given in table 1  rectifying diodes of medium power in table 2  and high-power rectifier diodes in table 3

A variety of rectifier diodes are . These devices on the reverse branch of the current-voltage characteristic have an avalanche characteristic similar to zener diodes. The presence of avalanche characteristics makes it possible to use them as elements of circuit protection against impulse overvoltages, including directly in the rectifier circuit.

In the latter case, rectifiers on these diodes work reliably in conditions of commutation overvoltages that arise in inductive circuits at the moment of switching on, switching off the mains or load. The main parameters of avalanche diodes at normal ambient temperature are given in

To straighten the voltage of more than a few kilovolts, straightening poles have been developed, which are a set of rectifier diodes connected in series and assembled into a single structure with two terminals. These devices are characterized by the same parameters as the rectifier diodes. The main parameters of the rectifier poles at normal ambient temperature are given in

To reduce the overall dimensions of the rectifiers and the convenience of their mounting are produced rectifier blocks (assembly) having two, four or more diodes, electrically independent or connected in the form of a bridge and assembled in one housing. The main parameters of rectifier blocks and assemblies at normal ambient temperature are given in

Diodes, pulse  differ from rectifying short time reverse recovery, or a large value of the impulse current. Diodes of this group can be used in rectifiers at high frequency, for example, as a detector or modulators, converters, pulse formers, limiters and other pulse devices, see reference tables 7   and 8

Tunnel Diodesperform the functions of active elements (devices capable of amplifying the signal by power) electronic circuits  amplifiers, generators, switches, mainly microwave ranges. Tunnel diodes have a high speed, small overall dimensions and weight, are resistant to radiation, reliably operate over a wide temperature range, are energy-efficient

The main parameters of tunnel and inverted diodes at normal ambient temperature are given in

  - their principle of operation is based on the electrical (avalanche or tunnel) breakdown of the p-n junction, at which a sharp increase in the reverse current occurs, and the reverse voltage varies very little. This property is used to stabilize the voltage in electrical circuits. Due to the fact that avalanche breakdown is typical for diodes made on the basis of a semiconductor with a large band gap, silicon is the starting material for zener diodes. In addition, silicon has a small thermal current and stable characteristics over a wide range of temperatures. To work in zener diodes use a gently sloping I-V characteristic of the reverse current of the disd, within which sharp changes in the reverse current are accompanied by very small changes in the reverse voltage.

Zener diode parameters and stabilizers  low power are given in, zener diodes and high power stabilizers - in, zener diodes precision -

The parameters of the voltage limiters are given in table 14

These are semiconductor diodes with electrically controlled barrier junction capacitance. The change in capacitance is achieved by varying the reverse voltage. As in other diodes, the resistance of the varicap base should be small. Simultaneously, to increase the value of the breakdown voltage, a large resistivity of the base layers adjacent to the transition is desirable. Proceeding from this, the main part of the base - the substrate - is made low-resistance, and the base layer adjacent to the transition is high-resistance. Varicaps are characterized by the following basic parameters. The total capacitance of the varicap SB is a capacitance that includes the barrier capacitance and capacitance of the shell, i.e. the capacitance measured between the varicap terminals at a given (nominal) reverse voltage.

Light-emitting diode  is a semiconductor device that converts electric current directly into light. It consists of one or several crystals placed in a housing with contact terminals and an optical system (lens) forming a light stream. The wavelength of the crystal radiation (color) depends on

These are the same LEDs that emit light in the infrared range

The information is presented in the format of the original PDF files, and for the convenience of downloading it is divided into collections in accordance with the English alphabet

The manual gives general information about domestic semiconductor diodes, namely, rectifier, diode matrices, stabilitrons and stabilizers, varicaps, radiating and ultra-high diodes. And also tells about their classification and the system of symbols. Conditional - graphical designations are given in accordance with GOST 2.730-73, and the terms and letter designations of parameters in accordance with GOST 25529-82. A little information is given on the use of voltage limiters and rules for the installation of diodes. In the application there are dimensional enclosure drawings and an alphanumeric index for navigation

This database is nothing more than an electronic guide to diodes that includes bridges and assemblies, and many radio components too.

There are more than 65,000 radio elements in the directory. There is information from all leading manufacturers as of December 2016. The following functions are implemented in the manual for diodes:

Sorting by several characteristics in any order
almost all characteristics filtering
editing data
viewing documentation and drawing of the body of a radio element
view data sheets in PDF format

In the tables for diodes the following conventions:

U mod.max.	-	maximum permissible constant reverse diode voltage;
U approx. And max.	-	maximum permissible pulse reverse diode voltage;
I pr.maks.	-	the maximum average forward current for the period;
I pr.i.max.	-	maximum pulsed forward current for the period;
I pr.	-	rectifier diode overload current;
f max.	-	maximum permissible switching frequency of the diode;
f work	-	operating diode switching frequency;
U pr at I pr	-	constant direct voltage diode at current Ip;
I arr.	-	constant reverse current of the diode;
T to max.	-	the maximum permissible temperature of the diode body.
T. max.	-	maximum permissible transition temperature of the diode.

Semiconductor diodes  one-hopping (with one electrical transition) electrical converters with two external current leads. An electron-hole junction, a metal-semiconductor contact, or a heterojunction can serve as an electrical transition. The figure shows schematically the device of a diode with an electron-hole transition 1 separating the p-th p-regions (2 and 3) with different types of electrical conductivity.

The crystal 3 is supplied with external current collectors 4 and placed in a metallic, glass, ceramic or plastic housing  5, which protects the semiconductor from external influences (atmospheric, mechanical, etc.). Usually, semiconductor diodes have asymmetric electron-hole transitions. One region of the semiconductor (with a higher impurity concentration) serves as an emitter, and the other (with a lower concentration) -base. When direct connection  external voltage to the diode, the injection of minority charge carriers mainly occurs from the heavily doped emitter region to the weakly doped base region.

The number of non-primary carriers passing in the opposite direction is much less than the injection from the emitter. Depending on the ratio of the linear dimensions of the transition and the characteristic length, planar and point diodes are distinguished. A diode is considered to be planar, in which the linear dimensions that determine the transition area are much larger than the characteristic length.

The characteristic length for diodes is the smallest of the two values ​​- the thickness of the base and the diffusion length of the minority carriers in the base. They determine the properties and characteristics of diodes. Point dies include diodes with linear dimensions of the transition, which are less than the characteristic length. The transition at the interface between regions with different types of conductivity has the properties of rectification (one-sided conductivity) of the current; nonlinearity of the current-voltage characteristic; the phenomenon of tunneling of charge carriers through a potential barrier both in the reverse and in the forward bias; the phenomenon of shock ionization of semiconductor atoms at relatively high voltages; barrier capacity, etc. These transition properties are used to create different types of of semiconductor diodes.

By the frequency range in which diodes can work, they are divided into low-frequency (LF) and high-frequency (HF). By appointment, low-frequency diodes are subdivided into rectifying, stabilizing, pulsed, and high-frequency diodes to detector, mixing, modular, parametric, switching, etc. Sometimes diodes distinguished by basic physical processes are distinguished in a special group: tunnel, avalanche-transit, photo -, LEDs, etc.

According to the material of the main semiconductor crystal, germanium, silicon, arsenide-gallium and other diodes are distinguished. To denote semiconductor diodes, a six-and seven-digit alphanumeric code is used (for example, KD215A, 2DS523G).

The first element is a letter (for devices of wide application) or a figure (for devices used in a special purpose device) -assesses the material on the basis of which the device was made: G or 1-germanium; K or 2 - silicon and its compounds; A or 3 - gallium compounds (for example, gallium arsenide); And or 4 - indium compounds (for example, indium phosphide).

The second element is a letter indicating the subclass or group of devices: D - rectifying, pulsed diodes; C - rectifying poles and blocks; B - varicaps; And - pulsed tunnel diodes; A - microwave diodes; C - zener diodes.

The third element - the digit - determines one of the main characteristics that characterize the device (for example, purpose or principle of operation).

The fourth, fifth and sixth elements are a three-digit number denoting the serial number of the development of the technological type of the device.

The seventh element - the letter - conditionally determines the classification according to the parameters of devices manufactured using a single technology. Example designation: 2SDS523G - a set of silicon impulse diodes for special purpose devices with a time to establish a reverse resistance from 150 to 500 ns; development number 23, group G. The development instruments up to 1973 have three and four-element notation systems.