The working principle of switching power supply

Switching power supply is a device that uses electronic switching devices (such as transistors, field effect transistors, etc.) to control energy storage components such as transformers by periodically turning on and off, and converts the input DC power supply into a stable output DC power supply. Its working principle mainly includes the following stages:

Opening stage: the switching device is turned on, and the input power supply is supplied to the primary winding of the transformer through the switching device, and the current flows through the primary winding of the transformer, and the electrical energy is converted into magnetic energy and stored in the transformer. At the same time, the voltage at the output end begins to rise due to capacitor filtering.

Shutdown stage: the switching device is turned off, the current in the primary winding of the transformer is suddenly interrupted, the magnetic energy stored in the transformer begins to be converted into electrical energy, the electric potential is induced in the secondary winding, and after the rectification and filtering circuit processing, a stable DC output voltage is provided to the load.

By repeating the process of turning on and off, the switching power supply can stably supply the required DC voltage and current at the output end, and has the advantages of high efficiency, small size and light weight. In practical applications, various feedback control circuits are used to realize stable regulation of output voltage, over-voltage protection, over-current protection and other functions.

Different types of switching power supplies will have different working details and control methods, but the basic principles are based on the switching conversion and energy conversion processes described above.

A switching power supply is usually composed of the following parts:

Input Circuit:

Function: Converts the AC power supply to a DC voltage suitable for the operation of the switching power supply. It includes rectifier circuits, filter circuits, etc., which are used to remove clutter and ripple in the input power supply and provide a stable DC input.

Power Conversion Circuits:

Function: Realize the conversion from DC to high-frequency AC. It is mainly composed of switches (such as MOSFETs, IGBTs, etc.), transformers, inductors, capacitors, etc. Through the on-off control of the switch, the input DC voltage is converted into high-frequency AC voltage, and then the voltage conversion and isolation are carried out through the transformer, and then the required DC output voltage is obtained through rectification, filtering and other links.

Control Circuit:

Function: Control and regulate the power conversion circuit. Including control chips, feedback circuits, drive circuits, etc. According to the set output voltage and current and other parameters, the control chip obtains the output voltage, current and other signals through the feedback circuit, carries out closed-loop control, adjusts the on-time and duty cycle of the switch tube, stabilizes the output voltage within the set value range, and realizes the protection functions such as over-current, over-voltage and over-temperature.

Output Circuit:

Function: Filter and stabilize the converted DC voltage. It is usually composed of capacitors, inductors, and other components to remove ripple and noise from the output voltage and provide a stable DC output.

Protection Circuits:

Function: Various protections for switching power supplies. Including over-current protection, over-voltage protection, short-circuit protection, over-temperature protection, etc. When there is an abnormal situation in the power supply, the protection circuit can act in time to cut off the power supply and avoid the occurrence of power supply damage and safety accidents.

In short, the various parts of the switching power supply cooperate with each other to realize the conversion of AC input into stable,