Working principle of frequency converter switch power supply
The working process of a switching power supply is quite easy to understand. In a linear power supply, the power transistor is operated in linear mode. Unlike a linear power supply, a PWM switching power supply operates the power transistor in both on and off states. In these two states, the volt ampere product added to the power transistor is very small (low voltage and high current during conduction, high voltage and low current during shutdown)/The volt ampere product on the power device is the loss generated on the power semiconductor device.
Compared with linear power supplies, the more effective 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 output voltage value 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 blocks, voltage reference, and error amplifier of the controller can be designed to be the same as linear regulators. Their difference is that the output of the error amplifier (error voltage) needs to go through a voltage/pulse width conversion unit before driving the power transistor.
Switching power supplies have two main operating modes: forward conversion and boost conversion. Although they
