Principle Analysis of Switching Power Supply (DC/DC)
1. Switching power supply: It is a high-frequency power conversion device, which mainly uses power electronic switching devices (such as transistors, MOS tubes, controllable thyristors, etc.), and through the control circuit, the electronic switching devices are periodically "turned on" And "turn off", let the power electronic switching device perform pulse modulation on the input voltage, so as to realize the function of voltage conversion and output voltage adjustment and automatic voltage stabilization.
Advantages of switching power supply: ① low power consumption and high efficiency. ②Small size and light weight. ③Wide range of voltage regulation.
Loss sources of switching power supply: ① switching tube loss. ②Inductance and capacitance loss. ③ Secondary tube loss.
Loss analysis of switching power supply: The efficiency of switching power supply can reach more than 90%, and if carefully optimized and designed, it can even reach more than 95%. This is very important in occasions where batteries are used as power sources, such as mobile phones and small drones. Therefore, the quality of the switching power supply design will directly affect the battery life of the device.
(1) Switching tube loss: This is the main loss of switching power supply, mainly including switching loss and conduction loss. Therefore, the switching tube with relatively small on-resistance should be selected as the core component of the switching power supply as much as possible.
(2) Inductance and capacitance loss: Inductance loss mainly includes DC resistance loss, and capacitance loss mainly includes leakage current loss. Therefore, you should try to choose an inductor with a small DC resistance and a capacitive component with a small leakage current.
(3) Diode loss: mainly includes conduction loss and switching loss. Therefore, you should try to choose a diode with a small conduction voltage drop and a short reverse recovery time, such as a Schottky diode or a fast recovery diode.
Second, the classification of switching power supply:
According to different modulation methods, it can be divided into two types: pulse width modulation (PWM) and pulse frequency modulation (PFM). At present, pulse width modulation (PWM) occupies a dominant position in switching power supplies.
According to the connection mode of the tube, it can be divided into three categories: series switching power supply, parallel switching power supply and transformer switching power supply.
According to the output voltage, it can be divided into two types: step-down switching power supply and boost switching power supply.
According to the input and output types, it can be divided into four types: AC-AC, DC-AC, AC-DC, and DC-DC. Here, DC-DC is mainly introduced.
