Direct current switching power supply is widely used in industrial field.
There are two technical indexes of DC power supply: one is characteristic index, including allowable input voltage, output voltage, output current and output voltage adjustment range; The other is quality index, which is used to measure the stability of output DC voltage, including voltage stabilization coefficient (or voltage regulation rate), output resistance (or current regulation rate) and ripple voltage (surrounding and random drift).
Main circuit design of DC switching power supply
The main circuit of DC switching power supply is used to complete DC-AC-DC conversion, and the main circuit of the system adopts full-bridge DC-DC converter, as shown in Figure 2. The power switching devices used in this system are IGBT modules of BSM 50GB120DN2 series, and each module has a half-bridge structure, so two modules are needed in the full-bridge system. A fast freewheeling diode is embedded in each module.
DC switching power supply has been widely used in many industrial fields. In industrial production (such as welding, electroplating or speed regulation of DC motor, etc.), a large number of DC power supplies with adjustable voltage are needed, and they generally require DC power supplies with convenient voltage output adjustment. At present, due to the advantages of high efficiency and miniaturization of switching power supply, the traditional linear regulated power supply and thyristor regulated power supply are gradually replaced by DC switching regulated power supply. The main control mode of switching power supply is to use pulse width modulation integrated circuit to output PWM pulse and analog PID regulator to carry out pulse width modulation. This control mode has certain errors and the circuit is more complicated.
principle of operation
The DC switching power supply consists of an input part, a power conversion part, an output part and a control part. The power conversion part is the core of switching power supply, which performs high-frequency chopping on unstable DC and completes the conversion function required for output. It is mainly composed of switching triode and high frequency transformer. Figure 1 shows the schematic diagram and equivalent block diagram of DC switching power supply, which is composed of full-wave rectifier, switching tube V, excitation signal, free-wheeling diode Vp, energy storage inductor and filter capacitor C. In fact, the core of DC switching power supply is a DC transformer.
