What is power diode?

Power diode is a semiconductor PN junction which converts alternating current (AC) to direct current (DC), a process known as rectification. It can carry large currents at high voltage levels for use in rectifier circuits. It has two terminals (Anode and Cathode) like a conventional PN junction diode, but the construction of a power diode and a normal diode is quite different. It is a special type of diode. Power diodes have very little forward voltage drop ranges between 0.5V to 1.2V. In other words, fix. Small signal diodes can be used in low power, low current (less than 1 amp) rectification and power applications. However, if a larger forward current or a higher reverse blocking voltage is required, the PN junction of the small signal diode will eventually overheat and be destroyed. Second, for high power applications, you should instead use larger and more robust power diodes. A power semiconductor diode, simply known as a power diode, has a much larger PN junction area than its small signal diode, with a high forward current capacity of up to hundreds of amperes (KA) and maximum reverse direction. Power diode brings blocking voltage up to thousands of volts (KV). The thickness of the depletion region or space charge region of a power diode is higher than the normal diode which allows to block a high reverse current without breaking down. This characteristic makes a power diode very efficient. 

Power diodes are not suitable for high frequency applications above 1MHz due to their large PN junctions, but special and expensive high frequency high current diodes are available. Schottky diodes are commonly used in high frequency and low voltage rectification applications due to their short reverse recovery time and low voltage drop in the forward biased state. Power diodes provide uncontrolled power rectification and are used in applications like battery charging, DC power supplies, AC rectifiers and inverters. Due to their high current and voltage characteristics, they can also be used as freewheeling diodes and snubber networks.  Power diodes are designed to have forward resistance that is a fraction of ohms, while reverse blocking resistance is in the mega ohm range. Some high quality power diodes are designed to be "stud mounted" on the heatsink, reducing thermal resistance to 0.1-1o C / watt. When an AC voltage is applied to a power diode, the diode conducts current during the positive half cycle, and during the negative half cycle, the diode does not conduct and cuts off the current flow. Second, conduction through the power diode is unidirectional because it only occurs during the positive half cycle. That’s why it is Direct Current.

Power Diode Rectifier

Power diodes can be used individually as described above or connected together to create a variety of rectifier circuits such as "half wave", "full wave" and "bridge rectifier". All types of commutators use uncontrolled, semi-controlled, uncontrolled commutators that use only power diodes, fully controlled commutators that use thyristors (SCRs), and semi-controlled commutators that are a combination of diodes. It is also classified as thyristor.

The most commonly used single power diode in basic electrical device applications is the 1N400x series glass passivation general purpose rectifier diode. The standard continuous rectification forward current rating is approximately 1.0 amp, and the reverse blocking voltage rating is 50V for the 1N4001 and 1000V for the 1N4007. Here, the small 1N4007GP is the most popular for general line voltage rectification.