How does the AC/DC Power Adapters — Desktop & Wall-Mount work?

We provide an easy-to-understand explanation of how the AC/DC Power Adapters — Desktop & Wall-Mount works. Starting with a circuit explanation, the names of each component are also illustrated, so we hope you will find it helpful.

Many electronic devices operate on DC (direct current). On the other hand, commercial electricity is AC (alternating current), so if AC is not converted to DC, the devices will not function. The device that handles this important job is called an AC/DC Power Adapters — Desktop & Wall-Mount.

This is why it is sometimes referred to as an "AC/DC adapter".

Recently, more and more Products are using AC/DC Power Adapters — Desktop & Wall-Mount, without internalizing the power supply unit, in order to achieve miniaturization, power saving, and simplified design of electronic devices.

Let's take a look inside an AC/DC Power Adapters — Desktop & Wall-Mount.

The circuit diagram of the photo above looks like this:

Internal circuit diagram of an AC/DC Power Adapters — Desktop & Wall-Mount

Below is a step-by-step explanation and introduction of the roles of each component.

  1. Electricity is supplied to the AC/DC Power Adapters — Desktop & Wall-Mount from the outlet via the AC cord, which you probably also use.
  2. Electric current passes through a fuse.
    ※Point: To prevent accidents and device damage caused by overcurrent, the fuse melts and disables the adapter if overcurrent flows during this process.
  3. Passes through a line filter to reduce noise.
  4. Utilizing the property of a diode that allows current to flow only in one direction, both the positive and negative waves of AC power supplied from the outlet are rectified to flow in the same direction as shown in the diagram below (called full-wave rectification).Diagram of AC current flow
  5. Using the ability of an electrolytic capacitor to store electricity, the capacitor is charged during high voltage and discharged during low voltage, smoothing out (reducing fluctuation in) the voltage.Diagram showing smoothed voltage
  6. After being smoothed and converted to DC, a transistor is switched on and off, converting it into high-frequency pulses (square waves). By adjusting the on/off time, the output voltage is adjusted. Even if the input voltage fluctuates, adjusting the pulse width allows the output voltage to remain stable. Moreover, high frequency allows for a more compact and lightweight transformer. (Transformers used in older AC adapters that relied on transformer type were much larger and heavier than modern switching types.)Diagram of voltage converted to high-frequency pulse
  7. Voltage is converted to an optimal level via a transformer.
  8. The pulse wave (square wave) is smoothed by an electrolytic capacitor. By repeating this process several times, it is turned into clean DC.Diagram showing pulse wave smoothed into clean DC
  9. Passes through a coil to reduce switching noise.
  10. Monitors output voltage and current, transmits the readings to the transistor, and adjusts the pulse width accordingly.
    ※Point: If abnormal voltage or current is detected, it also serves as a protection function that halts operation.

As described above, each component performs its specific role in building the AC/DC Power Adapters — Desktop & Wall-Mount.

In addition to the basic design of the AC/DC Power Adapters — Desktop & Wall-Mount explained as an example, we also accept requests for additional components or functions according to our customers' specific needs, so please feel free to contact us.

Related article: For a basic overview, see AC/DC Power Adapters — Desktop & Wall-Mount.

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