Detailed analysis of the circuit diagram of the switching power supply and the characteristics and applications of the switching power supply

Foreword: In the field of switching power supply technology, people develop related power electronic devices and develop switching frequency conversion technology. The two promote each other to promote the switching power supply to a light, small, thin, low noise and high annual growth rate of more than two digits. Reliable and anti-jamming direction. These advantages are especially obvious in household appliances, which has given birth to a lot of ideas for hands-on transformation into switching power supplies. The first task is to start by understanding the switching power supply circuit diagram.

The main circuit of the switching power supply consists of input electromagnetic interference filter (EMI), rectification and filtering circuit, power conversion circuit, PWM controller circuit and output rectification and filtering circuit. The auxiliary circuit has an input over-voltage protection circuit, an output over-voltage protection circuit, an output over-current protection circuit, and an output short-circuit protection circuit.

Detailed description of the switching power supply circuit diagram 　　

First, the main circuit

The entire process from AC grid input and DC output, including:

1. Input filter: Its function is to filter the clutter existing in the power grid, and also hinder the clutter generated by the machine from being fed back to the public power grid.

2. Rectification and filtering: The AC power supply of the power grid is directly rectified into a smoother DC power for the next level of transformation.

3. Inverter: The rectified DC power is changed into high frequency AC power, which is the core part of the high frequency switching power supply. The higher the frequency, the smaller the ratio of volume, weight and output power.

4. Output rectification and filtering: Provide stable and reliable DC power supply according to load requirements.

Second, the control circuit

On the one hand, sampling from the output, comparing with the set standard, then controlling the inverter, changing its frequency or pulse width to achieve output stability, on the other hand, according to the data provided by the test circuit, identified by the protection circuit, provided The control circuit performs various protection measures on the whole machine.

Third, the detection circuit

In addition to providing various parameters in the protection circuit, various display instrument data are also provided.

Fourth, auxiliary power supply

Provides different power requirements for all single circuits.

Switch control voltage regulation principle

The switch K is repeatedly turned on and off at a certain time interval. When the switch K is turned on, the input power source E is supplied to the load RL through the switch K and the filter circuit, and the power source E supplies energy to the load during the entire switch-on period; When the switch K is turned off, the input power source E interrupts the supply of energy. It can be seen that the input power supply provides energy to the load intermittently. In order to provide continuous energy supply to the load, the switching power supply must have a set of energy storage devices to store a part of the energy when the switch is turned on. Released to the load when disconnected.

Switching power supply circuit diagrams have different circuit design methods based on different uses. Even if the same use can be used for diversified placement, the working principle and the most important circuit components of the switching power supply will not change. Point, then analyze the specific switching power supply circuit diagram is much simpler.