As the core power supply component of electronic equipment, the details of the design, selection and maintenance of switching power supplies directly affect the operational stability of the equipment. Behind the seemingly basic parameters and principles, there are many easily overlooked practical knowledge points. Mastering these contents can make the use and debugging of switching power supplies more efficient.
Basic Principle Knowledge Points
1.The core of a switching power supply is to realize electric energy conversion through the high-frequency on-off of the switching tube, rather than the energy-consuming voltage stabilization of a linear power supply, which is the core reason for the high efficiency of switching power supplies.
2.The Buck converter is the most basic step-down topology of switching power supplies, where the output voltage is always lower than the input voltage, and the stability is better in the continuous inductor current mode.
3.The Boost converter is a step-up topology of switching power supplies, the boost inductor needs to be close to the input side, and the maximum duty cycle must be strictly limited to avoid circuit faults.
4.The oscillation modes of switching power supplies are divided into self-oscillating and separately excited types. Civil switching power supplies mostly adopt self-oscillating types, which can oscillate by themselves without an external signal.
5.In the rectification and filtering stage of a switching power supply, alternating current must first be converted to direct current, and then processed by high frequency, neither can be missing.
Component Selection Knowledge Points
6.Power MOSFETs are preferred for the switching tubes of switching power supplies, and their gate drive design directly affects the on-off efficiency of switching power supplies.
7.In the feedback loop of a switching power supply, the reference voltage of TL431 needs to be stabilized at about 2.5V, and an excessive deviation will lead to unstable output of the switching power supply.
8.The transformer of a switching power supply must match the topology type, and the transformer of a flyback switching power supply has both energy storage and voltage transformation functions.
9.For the input capacitor of a switching power supply, electrolytic capacitors with low ESR are preferred, which can effectively suppress the input inrush current of the switching power supply.
10.For the output filter inductor of a switching power supply, the core material should be selected according to the operating frequency of the switching power supply, and ferrite cores are suitable for high-frequency scenarios.
Performance Debugging Knowledge Points
11.The ripple measurement of a switching power supply must be carried out under a 20MHZ bandwidth, and 0.1uf and 47uf capacitors must be connected in parallel at the terminal to ensure accurate data.
12.The load regulation rate of a switching power supply needs to be tested within the range of 0%-100% rated load, and the deviation of high-quality switching power supplies should be controlled within ±0.5%.
13.For the line regulation rate of a switching power supply, the rated load should be maintained during the test, and only the input voltage is adjusted to observe the output change.
14.The over-temperature protection threshold of switching power supplies: industrial switching power supplies are generally set at 70℃, and will enter the hiccup mode after overheating.
15.The power factor correction link of a switching power supply can reduce the harmonic interference of the switching power supply to the power grid and improve the power utilization rate.
Application and Selection Knowledge Points
16.When selecting a switching power supply, a 10%-20% power margin should be reserved to avoid shortening the service life of the switching power supply due to long-term overload.
17.For switching power supplies in industrial scenarios, attention should be paid to the insulation voltage parameter, and the insulation voltage of isolated switching power supplies is generally not less than 1500VDC.
18.Switching power supplies used outdoors need to meet the operating temperature range of -40~+70℃, and the moisture and dustproof grade should be adapted to the environment.
19.Modular switching power supplies can be directly mounted on the circuit board, and a complete power supply system can be formed with a small number of discrete components. The modular switching power supplies of IDEALPLUSING have good adaptability in industrial scenarios.
20.The electromagnetic compatibility of switching power supplies must comply with the EN55022 standard to prevent the switching power supply itself from interfering with other electronic equipment.
Every knowledge point of switching power supplies revolves around "stability, high efficiency and adaptability". From basic topology to practical application, the seemingly trivial details are the key to making switching power supplies exert the best performance. Understanding these knowledge points can not only avoid mistakes in selection, but also quickly locate the fault problems of switching power supplies in daily maintenance, making switching power supplies a reliable power source for electronic equipment.
