Diode Rectifier Basics and Circuit Types Overview

Introduction

The rectifier diode is a semiconductor device that converts AC into DC. Usually it contains a PN junction with two terminals, a positive electrode and a negative electrode. The most important characteristic is unidirectional conductivity. In electronic circuits, its breakdown voltage is high, the reverse leakage current is small, and the high temperature performance is good. Generally, it can be made of materials such as semiconductor germanium or silicon. In addition, high-voltage and high-power rectifier diodes are made of high-purity single crystal silicon (it is easy to reverse breakdown when there is more doping). This kind of device has a large junction area and can pass a large current (up to thousands of amperes), but the operating frequency is not high, generally below tens of KHz. Rectifier diodes are mainly used in various low-frequency half-wave rectifier circuits. If require full-wave rectification, several diodes need to be connected to form a rectifier bridge.

What is a Rectifier? (AC to DC)

Catalog

Introduction

Ⅰ Common Parameters

Ⅱ Rectifier Diodes Selection

Ⅲ Rectifier Common Failures

Ⅳ Rectifier Diodes Detection

Ⅴ Rectifier Diode Replacement

5.1 Replacing Rules

5.2 Commonly Used Rectifier Models List

Ⅵ Rectifier Diode Circuit Types

6.1 Half-Wave Rectifier Circuit

6.2 Full-Wave Rectifier Circuit

6.3 Bridge Rectifier Circuit

Ⅶ High-frequency Rectifier Diodes

Ⅷ FAQ

Ⅰ Common Parameters

The rectifier diode uses the unidirectional conductivity of the PN junction to convert alternating current into pulsating direct current. Rectifier diodes have a large leakage current, and most of them are diodes packaged with surface mount materials. The parameters of the rectifier diode include the maximum rectifier current, which refers to the maximum current value allowed by the rectifier diode for long-term operation. It is the main parameter of the rectifier diode and the main basis for the option of the rectifier diode. Except it, other important parameters are introduced here.

(1) Maximum average rectified current IF: It refers to the maximum forward average current allowed to pass through the diode during long-term operation. The current is determined by the PN junction area and the heat dissipation conditions. It should be noted that the average current passing through the diode cannot be greater than this value, and has heat dissipation.

(2) Maximum reverse working voltage VR: It refers to the maximum reverse voltage allowed to be applied across the diode. If it is greater than this value, the reverse current (IR) will increase sharply, and the unidirectional conductivity of the diode will be destroyed, causing reverse breakdown. Usually take half of the reverse breakdown voltage VB as VR.

(3) Maximum reverse current IR: It is the reverse current allowed to flow through the diode under the highest reverse working voltage. This parameter reflects the quality of the unidirectional conductivity of the diode. Therefore, the smaller the current value, the better the diode quality.

(4) Breakdown voltage VB: It refers to the voltage value at the sharp bend point of the reverse volt-ampere characteristic curve of the diode. When the reverse is a soft characteristic, it refers to the voltage value under a given reverse leakage current condition.

(5) The highest operating frequency fm: It is the highest operating frequency of the diode under normal conditions. It is mainly determined by the junction capacitance and diffusion capacitance of the PN junction. If the operating frequency exceeds fm, the unidirectional conductivity of the diode will not be well reflected.

(6) Reverse recovery time trr: It refers to the reverse recovery time under the specified load, forward current and maximum reverse transient voltage.

(7) Zero-bias capacitor CO: It refers to the sum of the capacitance of the diffusion capacitance and the junction capacitance when the voltage across the diode is zero. It is worth noting that, due to the limitation of the manufacturing process, even the same type of diode has a large dispersion of its parameters. The parameters given in the manual are often within a range. If the test conditions change, the corresponding parameters will also change. For example, the IR of the 1N5200 series silicon plastic rectifier diode measured at 25°C is less than 10uA, and at 100°C IR becomes less than 500uA.

Ⅱ Rectifier Diodes Selection

Rectifier diodes are generally planar silicon diodes, which are used in various power rectifier circuits. When selecting a rectifier diode, the parameters such as its maximum rectifier current, maximum reverse working current, cut-off frequency and reverse recovery time should be mainly considered.

The rectifier diode used in the ordinary series stabilized power supply circuit does not require high reverse recovery time of the cut-off frequency. The rectifier diode with the maximum rectified current and maximum reverse working current should meet the requirements of the circuit.

The rectifier diode used in the rectifier circuit of the switching regulated power supply and the pulse rectifier circuit should be a rectifier diode with a higher operating frequency and shorter reverse recovery time (such as RU series, EU series, V series, 1SR series, etc.) or select fast recovery diodes, or Schottky rectifier diode.

Ⅲ Rectifier Common Failures

(1) Inadequate lightning protection and poor overvoltage protection. The rectifier device is not equipped with lightning protection and overvoltage protection devices. Or insufficient routine maintenance of the equipment.

(2) Poor operating conditions. In the indirect drive generator set, because the calculation of the speed ratio is incorrect or the ratio of the diameters of the two belt pulleys does not meet the requirements of the speed ratio, the generator runs at a high speed for a long time, so the rectifier is at a higher voltage for a long time. It accelerates the rectifier aging, and was damaged by premature breakdown.

(3) Poor operation management. The load failure or diode breakdown doesn’t fixed in time.

(4) Poor equipment installation or manufacturing process. The generator set has been operating under large vibration for a long time, which affects the rectifier tube operation. At the same time, because the generator set speed is unstable, the working voltage of the rectifier tube also fluctuates, which greatly accelerate the aging and damage of the rectifier tube.

(5) The specifications and models of the rectifier tube do not match. When replacing a new rectifier tube, wrongly replace the tube whose working parameters do not meet the requirements or the wiring is wrong, causing the rectifier tube to breakdown and damage.

(6) The safety margin of the rectifier tube is too small. The overvoltage and overcurrent safety margin of the rectifier tube is too small, so that the rectifier tube cannot withstand the overvoltage or the peak value of the overcurrent transient process that occurs in the generator excitation circuit and is damaged.

diode as rectifier symbol

Figure 1. Diode as Rectifier Symbol

Ⅳ Rectifier Diodes Detection

Here is a more general and simple method. Remove all the rectifier diodes in circuit, use the 100×R or 1000×R ohm range of a multimeter to measure the two lead wires of the rectifier diode (adjust and test twice). If the resistance values measured twice are very different, for example, the resistance value is as high as a few hundred kΩ to infinity, or the resistance value is only a few hundred Ω or less, indicating that the diode is good (except under special circumstances). If the resistance value measured twice is almost the same and the resistance value is very small, it means that the diode has been broken down and cannot be used. In addition, if the resistance values measured twice are both infinite, it means that the diode has been internally disconnected and cannot be used.

Ⅴ Rectifier Diode Replacement

5.1 Replacing Rules

After the rectifier diode is damaged, you should replace with the same model or another model with the same parameters.

Generally, rectifier diodes with high withstand voltage (reverse voltage) can be substituted for rectifier diodes with low withstand voltage, while rectifier diodes with low withstand voltage cannot be replaced with rectifier diodes with high withstand voltage. A diode with a high rectification current value can be substituted for a diode with a low rectification current value, while a diode with a low rectification current value cannot be substituted for a diode with a high rectification current value.

5.2 Commonly Used Rectifier Models List

Material

Model

Reverse Voltage Operation

(peak)

Average Rectified Current

 

Silicon Rectifier Diode

1N4001

50V

1A (Ir=5uA,Vf=1V,Ifs=50A)

1N4002

100V

1A

1N4003

200V

1A

1N4004

400V

1A

1N4005

600V

1A

1N4006

800V

1A

1N4007

1000V

1A

1N4148

75V

4PF, Ir=25nA,Vf=1V

1N5391

50V

1.5A (Ir=10uA,Vf=1.4V,Ifs=50A)

1N5392

100V

1.5A

1N5393

200V

1.5A

1N5394

300V

1.5A

1N5395

400V

1.5A

1N5396

500V

1.5A

1N5397

600V

1.5A

1N5398

800V

1.5A

1N5399

1000V

1.5A

1N5400

50V

3A (Ir=5uA,Vf=1V,Ifs=150A)

1N5401

100V

3A

1N5402

200V

3A

1N5403

300V

3A

1N5404

400V

3A

1N5405

500V

3A

1N5406

600V

3A

1N5407

800V

1A (Ir=5uA,Vf=1V,Ifs=50A)

1N5408

1000V

1A

Ⅵ Rectifier Diode Circuit Types

The power grid supplies users with alternating current, and various electrical devices require direct current. Rectification is the process of converting AC into DC. Utilizing the device with unidirectional conductivity, the current of alternating direction and magnitude can be converted into direct current. The following introduces three main rectifier circuits composed of crystal diodes.

6.1 Half-Wave Rectifier Circuit

Half-Wave Rectifier Circuit

Figure 2. Half-Wave Rectifier Circuit

The figure shows the simplest rectifier circuit. It is composed of power transformer B, rectifier diode D and load resistor Rfz. The transformer transforms the voltage into the required alternating voltage e2, and then D transforms the AC into pulsating DC.

The transformer threshold voltage e2 is a sine wave voltage whose direction and magnitude change with time, and its waveform is shown in Figure (a). In the 0~K time, e2 is a positive half cycle, that is, the upper end of the transformer is positive and the lower end is negative. At this time, the diode is in forward conductive conduction, and e2 is added to the load resistor Rfz through it. Within π~2π, e2 is in negative half cycle, the lower end of the transformer secondary is positive, and the upper end is negative. At this time, D bears the reverse voltage and does not conduct, and there is no voltage on Rfz. In the time of π~2π, the process of 0~π time is repeated, and in the time of 3π~4π, the process of π~2π time... half-cycle through Rfz, a single right direction voltage is obtained on Rfz (up positive and lower negative), as shown in Figure (b), which achieves the purpose of rectification. But the load voltage Usc, and the load current also changes with time, so it is usually called pulsating DC.

Half-Wave Rectifier Wave

Figure 3. Half-Wave Rectifier Wave

This rectification method of removing the first half week and leaving half a week is called half wave rectification. It is not difficult to note that the half-wave rectification is at the expense of consuming half of the AC in circuit, and the current utilization rate is very low. According to it, half-wave rectifier diode is commonly used in high voltage and small current occasions, and is rarely used in general radio devices.

6.2 Full-Wave Rectifier Circuit

Full-Wave Rectifier Circuit

Figure 4. Full-Wave Rectifier Circuit

If some adjustments are made to the structure of the rectifier circuit, a full-wave rectifier circuit that can be obtained. The figure above is the electrical schematic diagram of the full-wave rectifier circuit.

The full-wave rectifier circuit can be regarded as a combination of two half-wave rectifier circuits. A tap needs to be drawn in the middle of the secondary coil of the transformer to divide the secondary coil into two symmetrical windings, so as to get two voltages e2a and e2b of equal size but opposite polarity to form two energized circuits.

The working principle of the full-wave rectifier circuit can be illustrated by the waveform diagram. Between 0 and π, e2a is a positive voltage to Dl, D1 is turned on, and a up positive and down negative voltage is obtained on Rfz. e2b is a reverse voltage to D2, and D2 is not conductive (see Figure(b) ). In the time of π-2π, e2b is a positive voltage to D2, D2 is turned on, and the voltage obtained on Rfz is still up positive and down negative voltage, therefore e2a is a reverse voltage to D1, and D1 is not conductive (see figure (c).

Full-Wave Rectifier Circuit Wave

Figure 5. Full-Wave Rectifier Circuit Wave

Repeated this way, because the two rectifier elements D1 and D2 conduct electricity in turn, the result is that the load resistor Rfz has the same direction of current at the positive and negative half cycles, as shown in Figure(b). This is full-wave rectification, which not only uses the positive half-cycle, but also cleverly uses the negative half-cycle. Full-wave rectifier greatly improves the rectification efficiency.

Full-Wave Rectifier Circuits

Figure 6. Full-Wave Rectifier Circuits

This circuit requires the transformer to have a secondary center tap that makes the two ends symmetrical, which brings a lot of trouble to the production. In addition, in this circuit, the maximum reverse voltage that each rectifier diode can withstand is twice the maximum value of the transformer secondary voltage, so diodes should withstand higher voltages.

6.3 Bridge Rectifier Circuit

Bridge Rectifier Circuit

Figure 7. Bridge Rectifier Circuit

The bridge rectifier circuit is the most used rectification circuit. It has the advantages of a full-wave rectifier circuit as long as two diode ports are connected to form a bridge structure, so its shortcomings are overcome to a certain extent.

The bridge rectifier circuit is as follows:

Bridge Rectifier Circuit(a)

Figure 8. Bridge Rectifier Circuit (a)

When e2 is a positive half cycle, D1, D3 and the direction voltage, D1, D3 are turned on; D2, D4 are applied with reverse voltage, they are turned off. E2, Dl, Rfz, and D3 are energized a loop in the circuit. On Rfz, a positive and negative half-wave washing voltage is formed. When e2 is a negative half cycle, a positive voltage is applied to D2 and D4, and they are turned on; Apply reverse voltage to D1 and D3, they are cut off. E2, D2Rfz, and D4 are energized a loop in the circuit, and the other half-wave rectified voltage is also formed on Rfz.

Bridge Rectifier Circuit(b)

Figure 9. Bridge Rectifier Circuit (b)

If repeated, a full-wave rectified voltage at Rfz is made. The waveform diagram is the same as the full-wave rectifier. It is not difficult to see from the figure that the reverse voltage of each diode in the bridge circuit is equal to the maximum value of the secondary voltage of the transformer, which is half smaller than the full-wave cleaning circuit.

Ⅶ High-frequency Rectifier Diodes

The rectifier diode in the switching power supply must have the characteristics of low forward voltage reduction and fast recovery, and should also have sufficient output power. The following three types of high-frequency diodes can be used: fast recovery rectifier, ultra-fast recovery rectifier, and Schottky diode rectifier.

Fast recovery and ultra-fast recovery rectifier diodes have moderate and high forward voltage drop, and the range is from 0.8 to 1.2V. These two types of rectifier diodes also have higher cut-off voltage parameters. Therefore, they are particularly suitable for use in low-power auxiliary power circuits with output voltages around 12V.

Compared with general rectifier diodes, the reverse recovery time difference between fast recovery rectifier diodes and ultra-fast recovery rectifier diodes is reduced to the nanosecond level, thus greatly improving the efficiency of the power supply. According to experience, when choosing a fast recovery rectifier diode, its reverse recovery time should be at least 1/3 of the rise time of the switching transistor. These two kinds of rectifier diodes also reduce the switching voltage spike, because it will affect the ripple of the output DC voltage.

Whether fast recovery rectifier diodes and ultra-fast recovery rectifier diodes used in switching power supplies need a heat sink, which depends on the maximum power of the circuit. Under normal circumstances, the allowable junction temperature is 175°C during manufacture. The manufacturer has a technical parameters provided for the designer to calculate the maximum output operating current, voltage, and case temperature. Even under the action of a large forward current, the forward voltage drop of Schottky rectifier diodes is very low, only about 0.4V. Moreover, as the junction temperature increases, its forward voltage drop decreases. Therefore, Schottky rectifier diodes are particularly suitable for low-voltage output circuits around 5V. Its reverse recovery time is negligible, because this device is a semiconductor device with majority carrier. During the switching process of the device, there is no need to remove the stored charge of the minority carrier.

Schottky rectifier diodes have two major shortcomings: First, the reverse cut-off voltage tolerance is low, about 100V; second, the reverse leakage current is large, making the device more susceptible to have heat breakdown than other types of rectifier devices. Of course, these shortcomings can also be overcome by adding a transient overvoltage protection circuit and appropriately controlling the junction temperature.

Ⅷ FAQ

1. How does a rectifier diode work?

A rectifier is a device that converts an Alternating Current (AC) into a Direct Current (DC) by using one or more contact diodes. ... In simple words, a diode allows current in just one direction. This unique property of the diode allows it to act sort of a rectifier by converting an alternating current to a DC source.

2. What is a function of rectifier diode?

A rectifier diode is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC).

3. What is the function of diode in rectifier circuit?

A characteristic of diodes is that current flows (forward direction) or current does not flow (reverse direction) depending on the direction of applied voltage. This works to convert alternating current (AC) voltage to direct current (DC).

4. Which is used as rectifier?

We know that the core use of rectifier is to convert AC current into DC current. The rectifier consists of semiconductor diodes to do this function.

5. What is the limitation of a diode rectifier?

Disadvantages of Full Wave Bridge Rectifier

It needs four diodes. The circuit is not suitable when a small voltage is required to be rectified. It is because, in this case, the two diodes are connected in series and offer double voltage drop due to their internal resistance.

6. What is the ideal rectifier diode efficiency?

It is the ratio of DC output power to the AC input power. The rectifier efficiency of a full-wave rectifier is 81.2%.

7. What is a fast recovery rectifier?

Definition: Fast Recovery Diode is a semiconductor device which possesses short reverse recovery time for rectification purpose at high frequency. A quick recovery time is crucial for rectification of high-frequency AC signal. Diodes are mostly used in rectifiers because they possess ultra-high switching speed.

8. Which diode is fast recovery diode?

FRD stands for fast recovery diodes. They offer high-speed support and generally have a trr of approximately 50 to 100 ns. With a VF of approximately 1.5V, it is rather large when compared to general rectifying diodes. Another generic term for the FRD type would be a “High-speed Diode.”

9. What is ultra fast recovery diode?

A fast diode is a faster-than-standard current rectifier. ... A fast rectifier typically recovers ten times faster than a standard rectifier, and an ultrafast designation is usually applied to rectifiers designed to beat the standard rectifier recovery by being more than fifty times faster.

10. What is the difference between a Schottky diode and a rectifier diode?

Schottky diode, also known as barrier diode is mainly used in low voltage circuits because the forward voltage drop of Schottky diode(Vf) is less than a rectifier diode. The forward voltage drop of a Schottky diode is typically in the range of . 25 to 0.5 V whereas the Vf of a rectifier diode is around 0.7 volts.

11. What is Schottky barrier rectifier?

The Schottky diode or Schottky Barrier Rectifier is named after the German physicist Walter H. Schottky, is a semiconductor diode designed with a metal by the semiconductor junction. It has a low-forward voltage drop and a very rapid switching act. ... Actually, it is one of the oldest semiconductor devices in reality.

Leave A Reply

Your email address will not be published. Required fields are marked*