Comparison of rectifier diodes 1N4001-1N4007（1）

Rectifier diode 

A semiconductor device that converts alternating current into direct current.Usually it contains a PN junction, with positive and negative terminals.The most important characteristic of a diode is its one - way conductivity.In a circuit, current can only flow in from the positive pole of a diode and out from the negative pole.

A semiconductor device that converts alternating to direct current (dc).The diode is the most important feature is the single direction of electrical conductivity.In a circuit, current can only flow in from the positive pole of a diode and out from the negative pole.Usually it contains a PN junction, with positive and negative terminals.Its structure is shown in the figure.The charge carriers in the P region are holes and the charge carriers in the N region are electrons.Applied voltage make the voltage with a positive P area relatively N area, barrier is reduced, on both sides of the barrier near the produce store carrier, can pass the high current, low voltage drop (typically 0.7 V), is called to the state.If the opposite voltage is added, the barrier can be increased to withstand high reverse voltage and flow through a small reverse current (called reverse leakage current), which is called reverse blocking state.Rectifier diode has obvious unidirectional conductivity.Rectifier diodes can be made of semiconductor materials such as germanium or silicon.The silicon rectifier diode has high breakdown voltage, small reverse leakage current and good high temperature performance.High voltage and high power rectifier diodes are usually made of high purity monocrystalline silicon.This device junction area is larger, can pass the bigger current (up to thousands of Ann), but the working frequency is not high, usually under a few KHZ.Rectifier diodes are mainly used in a variety of low-frequency half-wave rectifier circuits.

(1) maximum average rectifier current IF: refers to the maximum forward average current allowed to pass through the diode during long-term operation.The current is determined by the junction area of the PN junction and the cooling condition.Note that the average current through the diode should not be greater than this value, and to meet the cooling conditions.For example, IF of 1N4000 series diode is 1A.

(2) highest reverse working voltage VR: refers to the maximum reverse voltage allowed to be applied at both ends of the diode.If the value is larger than this value, the reverse current (IR) will increase sharply, and the unidirectional conductivity of diode will be destroyed, thus causing the reverse breakdown.Take (VB) half of the reverse breakdown voltage (VR).For example, VR of 1N4001 is 50V, 1n4002-1n4006 is 100V, 200V, 400V, 600V and 800V respectively, and VR of 1N4007 is 1000V

(3) the largest reverse current IR: it is a diode in the highest reverse voltage, reverse current flow, this parameter to reflect the diode one-way conductive performance is good or bad.Therefore, the smaller the current value, the better the quality of the diode.

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

(5) highest working frequency FM: it is the highest working frequency of diode under normal conditions.Mainly determined by the junction capacitance and diffusion capacitance of PN junction, if the working frequency exceeds FM, the unidirectional conductivity of diode will not be well reflected.For example, the 1N4000 series diode has an FM of 3kHz.Quick recovery diodes are also used for rectification of high frequency alternating current, such as switching power supplies.

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

(7) zero-bias capacitor CO: refers to the sum of the capacity of the diffusion capacitor and the junction capacitor when the voltage at both ends of the diode is zero.It is worth noting that due to the limitation of manufacturing process, the parameters of even the same type of diode are very discrete.Is often a range of parameters in the manual, if the test conditions change, the corresponding parameters will also change, such as the measured 1 at 25 ° C n5200 series silicone sealants rectifier diode IR less than 10 ua, whereas at 100 ° C IR to less than 500 ua.

Damage reason

(1) insufficient lightning protection and overvoltage protection measures.No lightning protection or over voltage protection device is installed in the rectifier device. Even if the lightning protection or over voltage protection device is installed, its work is not reliable and the rectifier tube is damaged due to lightning strike or over voltage.

(2) operating conditions.Indirect transmission of the generator set, because the ratio of speed is not correct or the ratio of the diameter of the two belt disk does not meet the requirements of the ratio of speed, so that the generator for a long time in a high speed operation, and the rectifier tube is also in a high voltage for a long time to work, to accelerate the aging of the rectifier tube, and was prematurely damaged by breakdown.

(3) poor operation and management.The operator on duty shall not be responsible and shall not be aware of the changes in the external load (especially between midnight at night and 6:00 a.m. the next day), or shall fail to carry out the corresponding operation and treatment in time when the external load rejection fault occurs, resulting in over voltage and breakdown damage of the rectifier tube.

(4) equipment installation or manufacturing quality is not up to standard.Because the generator set is running in the vibration for a long time, the rectifier tube is also under the external disturbance of the vibration.The generator speed is high when the low at the same time, make the working voltage of rectifier bear also subsequently and change of high and low, thus greatly accelerated the aging, damage of rectifier.

(5) the specifications and models of rectifier tubes are inconsistent.When replacing the rectifier tube with a new one, the tube whose working parameters do not meet the requirements is wrongly replaced or the wiring is wrong, resulting in breakdown damage of the rectifier tube.

(6) rectifier tube small safety margin.The over voltage and over current safety margin of the rectifier tube is too small, so that the rectifier tube can not withstand the generator excitation loop in the over voltage or over current transient process peak attack and damage.

The detection of common diodes (including detection diode, rectifier diode, damping diode, switching diode and secondary diode) is a semiconductor device composed of a PN structure, with unidirectional conductive characteristics.By testing the positive and negative resistance of the diode with a multimeter, the electrode of the diode can be distinguished, and whether the diode is damaged can be estimated.

1.The polarity of the multimeter will be placed in R 100 or R 1k gear, the two watch pen are connected to the two electrodes of the diode, measured a result, adjust the two watch pen, and then measured a result.In the results of the two measurements, the resistance value measured in one test was larger (reverse resistance), and the resistance value measured in one test was smaller (forward resistance).In a measurement with small resistance, the black pen is connected to the positive pole of the diode, and the red pen is connected to the negative pole of the diode.

2.Single negative conductivity detection and good judgment, usually of germanium diodes, about 1 k Ω positive resistance and reverse resistance value to around 300.Silicon diode resistance is about 5 k Ω, reverse resistance value is up (infinite).Forward resistance as small as possible, reverse the greater the resistance, the better.Is, the more serious the reverse resistance difference, a one-way conductive characteristics of diode, the better.

If the positive and negative resistance values of the diode are close to 0 or the resistance values are small, it indicates that the diode has been broken short circuit or leakage damage.If measured diode is, reverse resistance of infinity, would show that the diode has been damaged.

3.Reverse breakdown voltage detection diode reverse breakdown voltage (withstand value) can be measured by transistor dc parameter test meter.The method is as follows: when measuring the diode, the "NPN/PNP" selection key of the test table should be set to the NPN state, and then the positive pole of the diode under test is connected to the "C" jack of the test table, and the negative pole is inserted into the "e" jack of the test table, and then press the "V (BR)" key, the test table can indicate the reverse breakdown voltage value of the diode.

Megohmmeter and multimeter can be used to measure the reverse breakdown voltage of diode, measurement is negative and the positive phase of the megohmmeter of diode, the diode connected to the positive and megohmmeter negative, at the same time the multimeter (placed in the appropriate dc voltage) monitoring at the ends of the diode voltage.As shown in figure 4-71, shaken by megger handle (by slow gradually speed up), stay on both ends of the diode voltage stability and no longer rises, the voltage value is the reverse breakdown voltage of diode.

(2) detection of voltage stabilizing diode

1.Judging of positive and negative electrodes in terms of appearance, the positive end of the metal encapsulated stabilized voltage diode body is planar, and the negative end is semicircle.Plastic-sealed stabilizer diode body printed with color mark on one end of the negative pole, the other end of the positive pole.Zener diode of mark is not clear, also can use the multimeter to judge its polarity, measurement method for the same as the common diode, use multimeter R x 1 k file, two pens and zener diode of two electrodes, respectively, measure a result, the pens and two measuring again.In the two measurement results, the resistance value is small that time, the black watch pen is connected to the positive pole of the stabilized diode, red watch pen is connected to the negative pole of the stabilized diode.

If the positive and negative resistances of the voltage stabilizing diode are small or infinite, the diode has been broken or broken.

2.Voltage value measurement with 0 ~ 30 v continuous adjustable dc power supply, the following for 13 v zener diode, regulated power supply output voltage can be tuned to 15 v, will power the positive concatenated 1 only 1.5 k Ω current-limiting resistance after measured zener diode connected to the cathode, and power negative into the positive electrode of zener diode, again at the ends of the zener diode voltage is measured with a multimeter, measured readings is the zener diode voltage values.If the regulated value of the regulated diode is higher than 15V, the regulated power supply shall be adjusted to 20V or above.

A megohm meter of less than 1000V can also be used to supply test power for a stabilized diode.The method is: will megger are end into the negative electrode of zener diode, the negative terminals of the megohmmeter and the positive phase of the zener diode, uniform turned megohmmeter handle according to regulations, at the same time the multimeter monitoring on both ends of the zener diode voltage (multimeter voltage profile should be depending on the size of the stable voltage value), directions for multimeter voltage stability, the voltage value is the stability of the zener diode voltage value.

If the stable voltage value of the voltage stabilizing diode is measured, it indicates that the diode is unstable.

Figure 4-72 is the measurement method of voltage stabilizing diode value.

(3) detection of two-way triggered diodes

1.Multimeter R 1k or R 10k for the measurement of positive and reverse resistance.When their positive and reverse resistance value shall be the normal infinity.If both positive and negative resistance values are small or 0, the diode has been broken.

2.There are three ways to measure the turning voltage of a bidirectional triggered diode.

The first method is to connect the positive pole (E) and negative pole (L) of the megohm meter to the two ends of the bidirectional trigger diode respectively, provide the breakdown voltage with the megohm meter, and measure the voltage value with the dc voltage file of the multimeter at the same time.Compare the difference between the two measurements of voltage (generally 3~6V).The smaller the deviation, the better the performance of the diode.

The second method is to measure the mains voltage U with a multimeter, and then connect the measured bidirectional trigger diode into the ac voltage measurement circuit of the multimeter, access the mains voltage and read out the voltage value U1, and then connect the two poles of the bidirectional trigger diode and read out the voltage value U2.

If the voltage value of U1 and U2, but unlike U voltage value, then the bidirectional trigger diode conduction performance good symmetry.If the voltage values of U1 and U2 differ greatly, it indicates that the conductivity of the bidirectional triggered diode is asymmetric.If the voltage values of U1 and U2 are the same as that of the mains power U, it indicates that the two-way triggered diode has been damaged by short circuit.If the voltage values of U1 and U2 are both 0V, it indicates that the internal open circuit of the bidirectional trigger diode has been damaged.

The third kind of method is: use a scale of 0 ~ 50 v continuous adjustable dc power supply, the power of the positive series 1 only 20 k Ω resistor with one end of the bidirectional trigger diode, the power of the cathode concatenated multimeter current file (ma) to place it in 1 and the other end of the bidirectional trigger diode.Gradually increase the power supply voltage, when the ammeter pointer has a more obvious swing (dozens of microamps), it indicates that the two-way triggered diode has been on, at this time the voltage value of the power supply is the turning voltage of the two-way triggered diode.

Figure 4-73 shows the detection method of bidirectional triggered diode switching voltage.

(4) detection of light-emitting diodes

1.The judgement of positive, negative pole puts led below a illuminant, the size that observes two metal piece, usually one end of big metal piece is negative pole, one end of metallic piece is positive pole.

2.Performance is good or bad judgment

Measured with a multimeter R x 10 k file, light emitting diode is, reverse resistance value.Normal, positive resistance (black pens and connect the anode) of about 10 to 20 k Ω, reverse resistance Ω ~ up to 250 k (infinite).Higher sensitivity of the led, in the measurement of forward resistance value, the tube will emit light.If the positive and negative resistance values of the led are measured with a multimeter R 1k, it will be found that the positive and negative resistance values are close to infinity (infinity), because the positive voltage drop of the led is greater than 1.6v (higher than 1.5v of the battery voltage in the multimeter R 1k).

Charge a 220 F/25V electrolytic capacitor with the R 10k of the multimeter (the black watch pen is connected to the positive pole of the capacitor and the red watch pen to the negative pole of the capacitor), and then connect the positive pole of the charged capacitor to the positive pole of the led and the negative pole of the capacitor to the negative pole of the led. If the led has a very bright flash, the led is in good condition.

Also can use 3 v dc power supply, the power of the positive concatenated light-emitting diode after 1 only 33 Ω resistance of the anode, the power of the cathode of light-emitting diode cathode (see figure 4-74), the normal leds should shine.Or connect 1 section of 1.5v battery in series to the black watch pen of the multimeter (put the multimeter in R 10 or R 100 gear, the black watch pen is connected to the negative electrode of the battery, which is equal to the 1.5v battery in series with the table), connect the positive electrode of the battery to the positive pole of the led, the red watch pen is connected to the negative pole of the led, and the normal led should light up.