Components of Switching Power Supplies
The input of a switching power supply is mostly AC power (such as mains power) or DC power, while the output is mostly devices that require DC power, such as personal computers. Switching power supplies convert the voltage and current between the two.
Switching power supplies are different from linear power supplies. The switching transistors used in switching power supplies are mostly switched between fully open mode (saturation region) and fully closed mode (cutoff region), both of which have the characteristic of low energy dissipation. The conversion between switching modes will have high dissipation, but the time is short, so it is more energy-efficient and generates less waste heat. Ideally, a switching power supply itself does not consume electrical energy. Voltage stabilization is achieved by adjusting the on-time and off time of transistors. On the contrary, in the process of generating output voltage, the transistor of a linear power supply operates in the amplification region and consumes electrical energy itself.
The high conversion efficiency of switching power supplies is one of their major advantages, and because switching power supplies have a high operating frequency, they can use small-sized and lightweight transformers. Therefore, switching power supplies are also smaller in size and lighter in weight than linear power supplies.
If the high efficiency, volume, and weight of the power supply are key considerations, switch mode power supply is better than linear power supply. However, switch mode power supplies are relatively complex, with frequent switching of internal transistors. If the switching current is still processed, it may generate noise and electromagnetic interference that can affect other devices. Moreover, if the switch mode power supply is not specially designed, its power factor may not be high.
Components of Switching Power Supply
1. Main circuit
Impulse current limiting: Limit the impulse current on the input side at the moment the power is turned on.
Input filter: Its function is to filter out the clutter that exists in the power grid and hinder the feedback of the clutter generated by the machine back to the power grid.
Rectification and filtering: Directly rectify the AC power supply of the power grid into smoother DC power.
Inverter: Convert rectified DC power into high-frequency AC power, which is the core part of high-frequency switching power supply.
Output rectification and filtering: Provide stable and reliable DC power supply according to load requirements.
2. Control circuit
On the one hand, samples are taken from the output terminal, compared with the set value, and then the inverter is controlled to change its pulse width or frequency to stabilize the output. On the other hand, based on the data provided by the testing circuit, various protection measures are provided to the power supply by the control circuit after identification by the protection circuit.
3. Detection circuit
Provide various parameters and instrument data that are currently running in the protection circuit.
4. Auxiliary power supply
Implement software (remote) startup for power supply, providing power supply for protection circuits and control circuits (PWM chips, etc.).
