Analysis of working principle of switching power supply

The switching power supply causes the electronic switching device to be turned on and off continuously through the control circuit, and the electronic switching device pulsates the input voltage, thereby making the output voltage adjustable and automatically regulating. So what is the working principle of the switching power supply?

First, the working principle of switching power supply - - Introduction

The switching power supply mainly uses modern power electronic technology to maintain the stability of the output voltage by controlling the time ratio of the on and off of the electronic switching device. It is generally composed of PWM (Pulse Width Modulation) control IC and MOSFET, and has the characteristics of small size, light weight, low power and high efficiency. It has been widely used in military equipment, industrial automation control, medical equipment, digital products and other fields.

Second, the working principle of switching power supply - - structure

The switching power supply is mainly composed of a main circuit, a control circuit, a detection circuit and an auxiliary power supply. The role of each part is as follows:

The main circuit can be further divided into an inrush current limiting part, an input filtering part, a rectification and filtering part, an inverting part, an output rectification and filtering part. The inrush current limiting part is responsible for limiting the inrush current on the input side of the power-on instant; the input filter part is responsible for filtering the clutter; the rectifying and filtering part is responsible for rectifying the grid AC power to the direct current; and the inverter part is responsible for rectifying the formed direct current It is converted into high-frequency alternating current; the output rectification and filtering part is responsible for providing a stable and reliable DC power supply.

The control section is responsible for controlling the inverter to stabilize the output and providing various protection measures for the circuit.

The detection circuit is responsible for providing various parameters and data in operation.

The auxiliary power supply is used to implement software (remote) startup of the power supply to supply power to the normal operation of the circuit.

After understanding the structure of the switching power supply, let us look at what the working principle of the switching power supply looks like~~

Third, the working principle of switching power supply

The switching power supply works differently from the linear power supply. The linear power supply allows the power transistor to operate in linear mode, while the switching power supply allows the power transistor to operate in both on and off states. In other words, it is “chopper”. That is, the amplitude of the input DC voltage is reduced to a pulse voltage equal to the input voltage amplitude. This working principle of the switching power supply makes the voltammetric product applied to the power transistor small (low voltage, large current in the on state; high voltage and small current in the off state), that is, the loss generated on the power transistor Very small.

The switching power supply has two working modes: forward conversion and boost conversion. Although the circuit difference is small, the working process is very different, and it is suitable for different requirements of different occasions.