The core function of rectifier diodes (usually referring to standard PN junction diodes) and Schottky diodes in circuits is rectification, that is, converting alternating current into direct current. However, due to their different structures, their characteristics vary significantly, therefore, they are having different applications. Now let's break down their functions and differences in detail.

1、Core common function: Rectification

Rectification is their most important and common function. Whether it is a simple power adapter or a complex computer power supply, it is necessary to convert the alternating current from the power grid into the direct current required by electronic devices.

• Working principle: Utilizing the unidirectional conductivity of diodes - current can only pass through when the anode voltage is higher than the cathode voltage (forward-biased). Conversely (reverse bias), the current can hardly pass through.

• Typical circuits: half-wave rectification, full-wave rectification, bridge rectification.

The circuit path of transformer U2 is in the positive half-cycle

The current path of transformer u2 is in the negative half-cycle

The entire cycle current path is like this

So, the output voltage after rectification is 0.9 times that before rectification

2、Key Differences and Application Scenarios

Although both can rectify, the choice of which one depends on the specific application's requirements for efficiency, speed and voltage. Their core differences stem from the physical structure:

l  Rectifier diode: based on PN junction.

l  Schottky diode: Based on metal-semiconductor junction.

Based on the above differences, their application scenarios each have their own focuses:

1. The main application of Schottky diodes

Due to its low power consumption and high-speed characteristics, Schottky diodes are mainly used in:

l  Rectification of low-voltage, high-current power supply:

l  Scenarios: Secondary side rectification of computer switching power supplies (SMPS) (+12V, +5V, +3.3V output), mobile phone chargers, high-efficiency DC-DC converters.

l  Reason: Within circuits with low output voltages, a common 0.7V on-state voltage drop will cause significant power loss (power loss = Vf × current). For instance, in an output of 5V/10A, using a common diode (Vf=1V) would result in a loss of 10W, while using a Schottky diode (Vf=0.3V) would only cause a loss of 3W, with a very significant improvement in efficiency.

l  High-frequency circuits and high-speed switching circuits:

l  Scenarios: RF detector, mixer, clamp protection in digital circuits, switching power supply (frequency up to hundreds of kHz to MHz).

l  Reason: The extremely fast switching speed means that it will not generate severe noise and switching losses due to "reverse recovery time" when operating at high frequencies.

l  Prevent current backflow/reverse power supply protection:

l  Scenarios: In battery-powered devices or systems with multiple power sources, prevent the current from flowing back into the power source and damaging the equipment.

l  Reason: Low on-state voltage drop means less voltage loss on the normal path and less impact on system performance.

2. Main application of common rectifier diodes (PN junctions)

Due to its high-pressure resistance and low cost, the common rectifier diode is mainly used for:

l  Industrial frequency power supply rectification:

l  Scenarios: Power input stage (bridge rectifier stack) for household appliances and industrial equipment, welding machines, chargers.

l  Reason: is that the grid voltage is high (220V/380V) and the frequency is low (50/60Hz), so the requirement for switching speed is not high, but the requirement for reverse withstand voltage is very high. Schottky cannot withstand such a high voltage.

l  High-voltage, low-current rectification:

l  Scenarios: Anode high voltage of CRT monitor, power supply of laser generator.

l  Reason: In these situations, the voltage may be as high as several thousand or even tens of thousands of volts, and only special PN junction high-voltage rectifier diodes can handle it.

Summary and selection guide