The working principle of switching power supply and classification
The working process of the switching power supply is quite easy to understand, in the linear power supply, let the power transistor work in the linear mode, with the linear power supply is different from the pWM switching power supply is to let the power transistor work in the on-state and off-state, in these two states, added to the power transistor on the volt-ampere product is very small (in the on-state, the voltage is low, the current is large; off-state, the voltage is high, the current is small)/power device The volt-ampere product on the power device is the loss incurred on the power semiconductor device. Compared to linear power supplies, pWM switching power supplies work more efficiently by "chopping", i.e. chopping the input DC voltage into pulses of amplitude equal to the input voltage amplitude. The duty cycle of the pulse is adjusted by the controller of the switching power supply. Once the input voltage is chopped into an AC square wave, its amplitude can be raised or lowered by a transformer. The number of output voltage groups can be increased by increasing the number of secondary windings in the transformer. Finally these AC waveforms are rectified and filtered to obtain the DC output voltage. The main purpose of the controller is to keep the output voltage stable and the process is very similar to the linear form of controller. This means that the functional blocks of the controller, the voltage reference and the error amplifier, can be designed in the same way as a linear regulator. The difference is that the output of the error amplifier (the error voltage) passes through a voltage/pulse width conversion unit before driving the power tubes. Switching power supplies have two main modes of operation: forward conversion and boost conversion. Although the arrangement of their components differs very little, the operating processes are very different and each has its own advantages for a particular application.
Classification of switching power supplies
People in the field of switching power supply technology is the side of the development of related power electronic devices, the side of the development of switching inverter technology, the two promote each other to promote the switching power supply to more than double-digit growth rate each year towards the light, small, thin, low noise, high reliability, anti-interference direction of development. Switching power supply can be divided into AC / DC and DC / DC two categories, there are also AC / ACDC / AC such as inverter DC / DC converter has now achieved modularity, and the design technology and production processes at home and abroad have matured and standardised, and has been recognised by the user, but the modularity of the AC / DC, because of its own characteristics make the process of modularity, encountered a more complex technology and process manufacturing Problems. The structure and characteristics of the two types of switching power supplies are described below.
