What are the current sharing issues with parallel applications of fast recovery diode?

What are the current sharing issues with parallel applications of fast recovery diode?

How to solve the current sharing problem in parallel applications of fast recovery diode?

The output power of electrolytic rectifiers is extremely high, and each rectifier arm is often composed of dozens or even dozens of rectifier components in parallel, making the current sharing problem very prominent.

1、 When there are many parallel connections of fast recovery diode and a branch parallel circuit is formed in the structure, the fast recovery diode can be classified and grouped according to the proximity of the forward voltage drop. In branches that may flow large currents, component groups with slightly higher forward voltage drop can be assembled.

2、 When the voltage between the anode and cathode is high before and after the fast recovery diode is turned on, and the current rise rate after turning on is large, it is often chosen to use the fast recovery diode with the same turning on time as possible. However, due to the limited degree of freedom available for selecting the parameters of the fast recovery diode, it is often used in conjunction with circuit compensation methods for economic and convenient maintenance and replacement. After using compensation, the dispersion of component opening time can be between 5-6? About s is more suitable. The compensation method can include serializing a current sharing reactor in each fast recovery diode branch, or dividing the valve side coils of the rectifier transformer into multiple groups to reduce the number of fast recovery diode in each coil branch.

3、 In fact, the structural arrangement of the device cannot achieve complete symmetry, so there is a high number of current imbalances caused by different lengths of parallel component wiring and different positions of current flow inlets.

4、 There is also a current imbalance caused by the influence of other phases on only one arm, which is often caused by mutual inductance. The law is difficult to find, and mutual inductance must be detected from the geometric position of the alignment.