What are the principles for selecting diodes

What are the principles for selecting diodes

diodes have a wide range of applications and should be selected correctly according to the requirements of the circuit. The selection principles are as follows

The selection of diodes should be based on the main parameters

1. Rated forward working current

The rated forward working current refers to the forward current value that a diode is allowed to pass through during long-term continuous operation.

2. Surge current

Due to the presence of junction capacitance, when the frequency reaches a certain level, the capacitance is small enough to cause a short circuit in the PN junction. Causing the diode to lose unidirectional conductivity and unable to operate, the larger the PN junction area, the larger the junction capacitance, and the more unable it to operate at high frequencies.

3. Reverse working voltage

When the reverse working voltage applied to both ends of the diode reaches a certain value, the  will break down and lose its unidirectional conductivity. In order to ensure safe use, the reverse working electrical value is specified. For example, the reverse withstand voltage of lN4001 diode is 50V, and the reverse withstand voltage of lN4007 is 1000V.

4. Reverse current

Reverse current refers to the reverse current that flows through a diode under a specified temperature and reverse voltage. The smaller the reverse current, the better the unidirectional conductivity of the pipe.

The reverse current is closely related to temperature, and for every 10 ℃ increase in temperature, the reverse current doubles.

Silicon diodes have better stability than germanium diodes at high temperatures.

Based on the conductivity of materials, we classify them into conductors, insulators, and semiconductors. A semiconductor is a substance with special properties, and its conductivity is between that of a conductor and an insulator, so it is called a semiconductor. Common semiconductor materials include silicon (Si) and germanium (Ge). Diode is considered an elder in the semiconductor family, and its obvious property is its unidirectional conductivity, which means that current can only pass through one side, but cannot flow from the other side (from the positive pole to the negative pole).

5. Reverse recovery time

When changing from forward voltage to reverse voltage, the current generally cannot be instantly cut off and needs to be delayed for a little time, which is inverse 6 power

Power is the voltage applied to both ends of the diode multiplied by the current flowing through it. This limit parameter is particularly important for voltage regulator diodes and others.

6. Frequency characteristics

Surge current is an excessive forward current that is allowed to flow. It is not a normal current, but an instantaneous current. Its value is usually about 20 times the rated forward working current.