As the name suggests, switching power supplies use electronic switching devices (such as transistors, FETs, thyristors, etc.), through the control circuit, so that the electronic switching device constantly "on" and "off", let the electronic switch The device modulates the input voltage to achieve DC/AC, DC/DC voltage conversion, and adjustable output voltage and auto-regulation.
Switching power supplies generally have three operating modes: frequency, fixed pulse width mode, fixed frequency, variable pulse width mode, variable frequency and pulse width mode. The former working mode is mostly used for DC/AC inverter power supply or DC/DC voltage conversion; the latter two working modes are mostly used for switching regulated power supply. In addition, the switching power supply output voltage also has three working modes: direct output voltage mode, average output voltage mode, and amplitude output voltage mode. Similarly, the former mode of operation is mostly used for DC/AC inverter power supply, or DC/DC voltage conversion; the latter two working modes are mostly used for switching power supply.
According to the way in which the switching devices are connected in the circuit, the currently widely used switching power supplies can be roughly classified into three types: a series switching power supply, a parallel switching power supply, and a transformer switching power supply. Among them, the transformer type switching power supply (hereinafter referred to as the transformer switching power supply) can be further divided into: push-pull type, half-bridge type, full-bridge type, etc.; according to the excitation of the transformer and the phase of the output voltage, it can be further divided into: forward type , flyback, single-excitation and double-excited, etc.; if divided into uses, they can be divided into more categories.