Introduction to Special Electronic Components in Switching Power Supply

1、 Special diode

1. Fast Recovery Diode (FRD) - The reverse recovery time of a fast recovery diode is generally a few hundred nanoseconds, with a forward voltage drop of 0.6V~1V, a forward current of several amperes to several thousand amperes, and a reverse peak voltage of several hundred volts to several thousand volts. It can be used as an output rectifier in switching power supplies and as a blocking diode in primary side clamp protection circuits.

2. Super fast recovery diode (SRD) - SRD is developed on the basis of fast recovery diode. Its reverse recovery charge is further reduced, and the reverse recovery time can be as low as tens of nanoseconds. It can be used as an output rectifier diode, blocking diode, and rectifier diode in feedback circuits of switching power adapters.

3. Schottky diode (SBD) - full name Schottky barrier diode, it belongs to low voltage, low power consumption, high current, ultra high speed semiconductor power devices. Its reverse recovery time can be as small as a few nanoseconds, the forward conduction voltage drop is only about 0.4V, and the rectified current can reach tens to hundreds of amperes. Specially suitable for rectifier diodes and freewheeling diodes in low-voltage output circuits of switch power chargers.

4. Transient Voltage Suppressor (TVS) - also known as Transient Voltage Suppressor, has extremely fast response speed and stable clamping voltage. It is a new type of overvoltage protection device that can be used to protect switching power supply PWM integrated circuits, MOS power devices, and other voltage sensitive semiconductor devices.

5. Bidirectional Trigger Diode (DIAC) - also known as a two terminal AC device, is often used in conjunction with thyristors to form an overvoltage protection circuit for switching power transformers.

2、 Special resistor

1. Fusing resistor (FR) - Fusing resistor, also known as safety resistor or meltable resistor, has both the functions of a resistor and a fuse. The melting current ranges from tens of milliamps to tens of amperes, and the melting time is from a few seconds to tens of seconds.

2. Self healing fuse diode (RF) - also known as self recovering fuse, has the performance of automatic recovery, can be used repeatedly, and does not require maintenance or replacement.

3. Soft start resistor - It belongs to negative temperature coefficient thermistor (NTCR), characterized by low nominal resistance value (only 1 Ω~47 Ω), high rated power (10~500W), and large working current (1~10A), suitable as a starting protection component for switch power adapters.

4. Varistor (VSR) - has a wide operating voltage range (6V~3000V, divided into several levels), fast response speed to overvoltage pulses (several nanoseconds to tens of nanoseconds), strong ability to withstand surge currents (up to 100A~20Ka), low leakage current (less than a few microamperes to tens of microamperes), low temperature coefficient of resistance (less than 0.05%/℃), and low price. It can form overvoltage protection circuit, lightning protection circuit, spark elimination circuit, surge voltage absorption circuit, etc. for switch power adapters.

5. Digital Potentiometer (DCP) - Used in conjunction with an adjustable switching regulator to form a programmable switching regulator.

3、 Thyristor

1. Unidirectional thyristor (SCR) - used in conjunction with bidirectional trigger diodes to form a voltage protection circuit for an over switching power adapter.

2. Triac - can form an overvoltage protection circuit on the AC input side of a switching power supply.

4、 Other

1. Optocoupler: The current transfer ratio (CTR) of a linear optocoupler has good linearity with the characteristic curve of the DC input current (If). When transmitting small signals, it can establish a linear relationship between the output and input, making it suitable for constructing optocoupler feedback circuits in precision switching power supplies and achieving isolation between the secondary and primary sides.

2. Filter: also known as EMI filter, it belongs to bidirectional RF filter, which can filter out external electromagnetic interference introduced from AC lines on the one hand; On the other hand, it can also avoid noise interference from the switch power adapter to the outside, significantly improve the anti-interference ability of the switch power adapter, and make the switch power supply comply with electromagnetic compatibility (EMC) standards.

3. Adjustable precision parallel voltage regulator: such as TL431, can be widely used in precision switch power adapters, chargers, and can also form voltage comparators, power supply voltage monitors, delay circuits, precision constant current sources, etc.

4. Magnetic beads: There are tubular, sheet-like magnetic beads and magnetic bead arrays, which can suppress the switching noise and peak interference of switch power adapters and chargers. There are tubular, sheet-like magnetic beads and magnetic bead arrays that can suppress switch noise and spike interference of switch power adapters and chargers.