Power adapters, as computer accessories, often appear in our daily lives. In fact, power adapters are also used in many places, but people are not paying enough attention. Do you know what are the choices of power adapter components? Let's follow the manufacturer to learn more!

Communication input section

Select 250V3.15A fuse; The negative temperature coefficient thermistor model for surge current resistance is 5D-13; The varistor model is 14D471K.

Common mode power filter: Differential mode (X2) capacitor selection 275V/0.47pF (CX1) and 275V0. luF (Cx2); The common mode inductor model is WD03007; Choose 400V/2.2nF for common mode (Y2) capacitors (CYA, CY2).

Rectification and filtering section

1. Selection of rectifier bridge

According to section 5.2 of this book, it is known that the rectifier bridge requires a rated current of at least 5A and a rated voltage of at least 600V. In reality, GBU806 with 8A/600V was chosen

2. Filter capacitor

For a flyback power adapter powered by a 220V voltage level, the input rectifier filter capacitor actually needs to withstand a ripple current of about 0.8A. Due to the height limitation of the shell, a low height electrolytic capacitor is required. You can choose the 400V120 μ F low height (25mm) electrolytic capacitor produced in recent years. The voltage resistance meets the requirements and can withstand 0.75A (general specifications) -1.31A (high ripple current). This choice can basically meet the requirements

Main circuit section (excluding transformer design)

After the rectification and filtering circuit is the main circuit of the flyback power adapter, the main tasks that need to be done include determining the switching frequency, transformer design, selecting switch tube parameters and maximum duty cycle, and selecting the output rectifier and output filtering capacitor.

In order to reduce costs, most switching devices choose a rated voltage of 600V. For flyback power adapters with an output of 60W, the switching devices will withstand a peak current of about 2A. Considering that the conduction resistance of 600V MOSFETs is relatively large, especially in high junction temperature conditions, a relatively large current margin needs to be left. From the perspective of easy procurement, IRFBC40 (600V/6A/1.20) level MOSFETs are a good choice

The output rectifier requires a voltage resistance of no less than 90V. A Schottky diode with a voltage resistance of 120V can be selected. If you want to reduce costs, you can choose an ultra fast reverse recovery diode with a voltage resistance of 200V. This allows for a larger voltage margin. For example, BYQ28X-200 (some brands offer a price of up to 0.45 yuan) can withstand 200V and have a rated effective current of 14A, which can meet the design requirements.

The output rectifier filter capacitor should be a 16V/1000F high-frequency low resistance electrolytic capacitor that can meet the requirement of 6A ripple current