What is the reverse recovery current of a diode

Taking an AC DC boost switching power supply as an example, as shown in Figure 1, the Di dt of the reverse recovery current generated by the rectifier diode in the main circuit is much higher than that of the output diode Ddi/dt|Much smaller.

<> Figure 2 shows the current IDC and ID waveforms of the rectifier bridge diode and the output diode in Figure 1 of the switching power supply. It can be seen that the maximum value of the reverse recovery current of the former is only 50mA, while the amplitude of the reverse recovery current of the latter is 12A, and the duration is short. Obviously, as a source of electromagnetic interference, the interference formed by the latter is of high intensity and the frequency band is much wider.

In addition, the voltage jumps generated by the rectifier bridge diodes are much smaller than those generated when the power MOSFET switches on and off. Therefore, the |generated by the rectifier bridge diode can be disregardeddu/dt|AND |di/dt|and it is possible to study the rectifier circuit as part of the EMI coupling channel. As for the analysis and treatment of low-band harmonic interference caused by the non-sinusoidal working current of the rectifier bridge circuit to the mains power grid, etc., it has been relatively mature and perfect, and the relevant literature can be referred to.

Diode. At the time of forward conduction, the p-n knot.

There are a large number of carriers, and they cannot be cut off immediately when switching to the reverse voltage, and the reverse current formed by these surviving carriers when the reverse voltage is added is called the reverse recovery current, and it needs to wait for the remaining carriers to disappear before it can be cut-off, which is the "recovery" process.

The definition of the reverse recovery time (TR) of a fast recovery diode: the time interval between the transition of current from the zero point in the forward direction to a specified low value. It is an important technical index to measure the performance of high-frequency freewheeling and rectifier devices.

In a fast recovery diode, if is the forward current and IRM is the maximum reverse recovery current. IRR is the reverse recovery current, which is usually specified as IRR=. When t t0, the forward current i=if.

When t>t0, the forward current decreases rapidly because the forward voltage on the rectifier device suddenly becomes reverse, and at t=t1, i = 0. Then, the reverse current IR flows over the rectifier device, and the IR gradually increases. The maximum reverse recovery current IRM is reached at t=t2.

After that, the reverse current gradually decreases due to the forward voltage, and the specified value IRR is reached at T=T3. The reverse recovery process from T2 to T3 is similar to the capacitor discharge process. It can be seen that parameters such as reverse recovery time form a gap between fast recovery diodes and ordinary rectifier diodes.

The reverse recovery characteristic of a diode means that when switching between forward bias and reverse bias, there will be a reverse recovery process inside the diode. In this process, both the current and voltage of the diode change, which can be described by a number of parameters.

The following are the main parameters that describe the reverse recovery characteristics of the diode and their significance:

1.Reverse recovery time (T rr): Refers to the time it takes for the diode to drop from the maximum reverse current to the specified reverse current when the diode is reversed to forward biased.

This parameter is an important indicator to describe the reverse recovery speed of the diode, generally speaking, the shorter the reverse recovery time, the faster the reverse recovery speed of the diode.

2.Reverse recovery charge (q rr): refers to the charge generated by the regain kinetic energy from the reverse electric field by the carriers inside the diode during the reverse recovery process.

This parameter is closely related to the reverse recovery time, the shorter the reverse recovery time, the smaller the reverse recovery charge.

3.Peak reverse voltage (V r): Refers to the maximum reverse voltage that can be withstood by the diode reverse bias. Above this voltage, the diode will break down and be damaged.

4.Reverse leakage current (IR): Refers to the leakage current of a diode under reverse bias.

This parameter is related to the quality of the diode, generally speaking, the better the quality of the diode, the smaller the reverse leakage current.

These parameters are important indicators to describe the reverse recovery characteristics of diodes, and have important reference significance for the selection and use of diodes.

Reverse recovery loss: When the power diode switches from the reverse conduction state to the forward conduction state, it takes a certain amount of time to restore the forward conduction state, and the reverse recovery loss will be generated in the process.

The reverse recovery loss is mainly due to the fact that the power diode stores a certain charge in the reverse conduction state, and these charges will be released during the reverse recovery, resulting in energy loss.

The reverse recovery loss is related to the reverse recovery time, reverse current, and reverse voltage of the power diode. Nian Hui Qing.

It's not the same thing. The reverse recovery current is much larger than the reverse current.

Reverse current refers to a stable current measured with a specified reverse voltage and is usually small or even negligible for silicon tubes.

Reverse recovery current refers to the positive conduction of the diode, and has a specified current value, suddenly add the reverse voltage, because there are still a large number of carriers when the conduction just now, they will flow in the reverse voltage in the opposite direction, generating a huge "reverse recovery current", until the residual carriers are consumed, to reach stability is "recovery", then only the "reverse current" remains. This time to consume carriers is known as the reverse recovery time.

There is a type of diode called a "step recovery diode", which uses this reverse current to generate a pulse signal with a very narrow width.

When the diode is turned on in the forward direction, the PN balance has a large number of carriers, and it cannot be cut off immediately when switching to the reverse voltage, and the reverse current formed by these retained carriers when the reverse voltage is added is called the reverse recovery current, which needs to be cut off after the remaining carriers disappear, which is the "recovery" process.

Reverse current refers to the leakage current of the diode at the rated reverse voltage, generally in the zero point of a few microamperes, very small current, as for the reverse recovery current has not heard, maybe you are mistaken, it should be called the reverse recovery time, refers to the working frequency of the diode, the ordinary rectifier diode reverse recovery time is generally about 1000 2000ns, fast or high-speed rectifier diode reverse recovery time is about tens to hundreds of ns, there is no connection between the two, I hope my answer is helpful to you.

When the diode transitions from positive to reverse bias, a large reverse recovery current flows from the cathode to the anode, and the reverse current first rises to the peak and then drops to zero. Then the time of its rise and fall is the reverse recovery time, and the peak current is the reverse recovery current.

This can be costly in high-frequency applications. The reverse recovery time and current are positively correlated with the rate at which the forward current drops off at diode cut-off. To solve this problem, one is to use a diode with a faster recovery time, and the other is to use the ZCS method to turn off the diode.