Working principle of power supply Three conditions of power supply
The working principle of a switching power supply is quite easy to understand. In a linear power supply, the power transistor operates in a linear mode. Unlike a linear power supply, a PWM switching power supply allows the power transistor to operate in both on and off states, The volt ampere product added to the power transistor is very small (during conduction, the voltage is low and the current is high; during shutdown, the voltage is high and the current is low)/The volt ampere product on the power device is the loss generated on the power semiconductor device.
Working principle of switching power supply
The working process of a switching power supply is quite easy to understand. In a linear power supply, the power transistor operates in linear mode. Unlike a linear power supply, a pWM switching power supply allows the power transistor to operate in both on and off states, The volt ampere product added to the power transistor is very small (during conduction, the voltage is low and the current is high; during shutdown, the voltage is high and the current is low)/The volt ampere product on the power device is the loss generated on the power semiconductor device. Compared with linear power supplies, the more efficient working process of pWM switching power supplies is achieved through "chopping", which chops the input DC voltage into a pulse voltage with an 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 increased or decreased through a transformer. By increasing the number of secondary windings in the transformer, the number of output voltage groups can be increased. Finally, these AC waveforms are rectified and filtered to obtain a DC output voltage. The main purpose of the controller is to maintain stable output voltage, and its working process is similar to that of a linear controller. That is to say, the functional block, voltage reference, and error amplifier of the controller can be designed to be the same as the linear regulator. The difference between them is that the output of the error amplifier (error voltage) needs to pass through a voltage/pulse width conversion unit before driving the power transistor. There are two main working modes of switching power supply: forward conversion and boost conversion. Although the layout differences between their respective parts are small, the working processes vary greatly and each has its own advantages in specific application scenarios.
Three conditions for switching power supply
switch
Power electronic devices operate in a switching state rather than a linear state
high frequency
Power electronic devices operate at high frequencies rather than near power frequencies at low frequencies
direct current
Switching power supplies output DC instead of AC, and can also output high-frequency AC, such as electronic transformers
