Types and main uses of special components in power adapters

　　At present, the power adapter is developing in the direction of intelligence, miniaturization, and modularization. The correct understanding and selection of peripheral components is the basis and guarantee for the design and production of power adapter supplies and power adapters. There are many types of peripheral components used in the adapter circuit of the power adapter, with different performances. They can be roughly divided into two categories: general components and special components. The types and main uses of special components in the power adapter are as follows:

　　1. Special diodes:

　　1. Fast recovery diode (FRD) ----The reverse recovery time of fast recovery diode is generally several hundred nanoseconds, the forward voltage drop is 0.6V~1V, the forward current is several amperes to several thousand amperes, reverse The peak voltage can reach several hundred volts to several thousand volts, which can be used as the output rectifier tube in the power adapter and the blocking diode of the primary side clamp protection circuit.

　　2. Ultra-fast recovery diode (SRD) ---- Ultra-fast recovery diode 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 output rectifier tube, blocking diode, and rectifier tube in feedback circuit of power adapter adapter.

　　3. Schottky diode (SBD)-the full name is Schottky barrier diode, it belongs to low voltage, low power consumption, high current, ultra-high speed semiconductor power device, its reverse recovery time can be as small as a few nanometers Seconds, the forward voltage drop is only about 0.4V, and the rectified current can reach tens to hundreds of amperes. It is especially suitable for rectifier diodes and freewheeling diodes in the low-voltage output circuit of power adapter chargers.

　　4. Transient Voltage Suppression Diode (TVS)-also known as transient voltage suppressor, with extremely fast response speed and stable clamping voltage. It is a new type of overvoltage protection device that can be used to protect the power adapter PWM integration Circuits, MOS power devices, and other voltage-sensitive semiconductor devices.

　　5. Two-way trigger diode (DIAC) ---- also known as a two-terminal AC device, often used in conjunction with a thyristor to form a power adapter transformer output over-voltage protection circuit.

　　2. Special resistor for LED light power adapter:

　　1. Fuse resistor (FR) ---- Fuse resistor is also called fuse resistor or fusible resistor. It has the functions of resistor and fuse. The fuse current ranges from tens of milliamps to tens of amperes. The time is a few seconds to tens of seconds.

　　2. Self-recovery fuse tube (RF) ---- also known as self-recovery fuse, with automatic recovery performance, repeated use, no maintenance and replacement.

　　3. Soft-start resistance ---- It belongs to the negative temperature coefficient thermistor (NTCR). Its characteristics are low nominal resistance (only 1Ω~47Ω), high rated power (10~500W), and large working current ( 1~10A), suitable for starting protection component of power adapter.

　　4. Varistor (VSR) ---- wide working voltage range (6V~3000V, divided into several files), fast response to overvoltage pulse (a few nanoseconds to tens of nanoseconds), and the ability to withstand impact current Very strong (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 the over-voltage protection circuit, lightning protection circuit, anti-spark circuit, surge voltage absorption circuit of the power adapter.

　　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 the bidirectional trigger diode to form the voltage protection circuit of the power adapter adapter.

　　2. Triac (TRIAC) ---- can form an over-voltage protection circuit on the AC input side of the power adapter.

　　4. Optocoupler: The characteristic curve of current transfer ratio (CTR) and DC input current (If) of linear optocoupler has good linearity. When transmitting small signals, it can make the output and input have a linear relationship, which is suitable for forming the optical coupling feedback circuit in the precision power adapter, and realizes the isolation between the secondary side and the primary side.

　　5. Filter: Also known as EMI filter, it is a two-way radio frequency filter. On the one hand, it can filter out the external electromagnetic interference introduced from the AC line; on the other hand, it can also prevent the power adapter adapter from emitting noise interference to the outside, which can significantly improve The anti-interference ability of the power adapter adapter, and make the power adapter comply with electromagnetic compatibility (EMC) standards.

　　6. Adjustable precision shunt regulators: such as TL431, NCP100, which can be widely used in precision power adapters, chargers, and can also form voltage comparators, power supply voltage monitors, delay circuits, precision constant current sources, etc.

　　7. Magnetic beads: There are tubular, chip magnetic beads and magnetic bead arrays, which can suppress switching noise and spike interference of power adapters and chargers. There are tubular, chip-shaped magnetic beads and magnetic bead arrays, which can suppress the switching noise and spike interference of power adapter adapters and chargers.

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