Learn about special components in power adapters

At present, power adapters are developing in the direction of intelligence, miniaturization, and modularity. Correctly understanding and selecting components is the basis and guarantee for designing and manufacturing power adapters and power adapters. There are many types of peripheral components used in power adapter adapter circuits with different performances, which can be roughly divided into two categories: general components and special components. The types and main uses of special components in power adapters 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, 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. Super fast recovery diode (SRD) —- Super fast recovery diode is developed based on fast recovery diode, its reverse recovery charge is further reduced, and the reverse recovery time can be as low as tens of nanoseconds , Can be used as power adapter adapter output rectifier, blocking diode, rectifier in feedback circuit.

3. Schottky Barrier Diode (SBD), which is a low voltage, low power, high current, ultra-high speed semiconductor power device. Its reverse recovery time can be as small as a few nanoseconds, and the forward voltage drop is only 0.4. Around V, the rectified current can reach tens to hundreds of amps. Particularly suitable for rectifier diodes and freewheeling diodes in low-voltage output circuits of power adapter chargers.

4. Transient voltage suppression diode (TVS, which has a very fast response speed and stable clamping voltage, is a new type of overvoltage protection device that can be used to protect power adapter PWM integrated circuits, MOS power devices, and other voltage-sensitive semiconductors Device.

5. Bidirectional triggering diode (DIAC), often used together with thyristor, to form a power adapter transformer output overvoltage protection circuit.

Second, special resistors:

1. Fuse resistor (FR) —- Fuse resistor is also known as fuse or fusible resistor. It has the function of both resistor and fuse. The fuse current is from tens of milliamps to tens of amps. The time is several seconds to several tens of seconds.

2. Self-recovering fuse tube (RF), which has the function of auto-recovery, can be used repeatedly without maintenance and replacement.

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

4. Varistor (VSR) —- Wide working voltage range (6V ~ 3000V, in several steps), fast response to overvoltage pulse (several nanoseconds to dozens of nanoseconds), ability to withstand surge current Very strong (up to 100A ~ 20Ka), small 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 over voltage protection circuit, lightning protection circuit, spark elimination circuit, surge voltage absorption circuit, etc. of power adapter adapter.

5. Digital potentiometer (DCP) —- used with adjustable switching regulator to form a programmable switching regulator.