Pasākumi to samazināt pulsēt un troksnis spriegums in komutācija barošana barošanas avoti
Compared with linear power supplies, switching power supplies (including AC/DC converters, DC/DC converters, AC/DC modules, and DC/DC modules) have the most prominent advantage of high conversion efficiency, which can generally reach 80 percent to 85 percent , and up to 90 percent to 97 percent ; Secondly, the switching power supply uses high-frequency transformers instead of bulky power frequency transformers, which not only reduces weight but also reduces volume, resulting in an increasingly wide range of applications. However, the disadvantage of switching power supply is that its switch transistor operates in a high-frequency switching state, and the output ripple and noise voltage are relatively large, usually around 1 percent of the output voltage (the low is about 0.5 percent of the output voltage). The best product also has a ripple and noise voltage of tens of mV; The adjustment tube of the linear power supply operates in a linear state, without ripple voltage, and the output noise voltage is also small, with the unit of μ V.
Šis raksts īsi ievada cēloņus un mērījumus metodes of ripple and troksni ģenerēts by switching power supplies, measurement devices, measurement standards, and measures to reduce ripple and noise.
1, iemesli par pulsācija un troksnis ģenerēšana:
izeja of the switching power supply is not pure DC spriegums, bet tur ir daži maiņstrāvas komponenti inside, kas ir izraisa ar ripple and troksni. Ripple is the fluctuation of the output DC spriegums, kas ir saistīts ar the switching action of the switching power supply. In katrs atvēršana un aizvēršana process, elektrība enerģija is "pumped" from the input end to the output end, forming a process of charge and dislonging, rezultāts in svārstības in izeja spriegums, ar a frekvence līdzīgs attiecība frekvence of the switch. Ripple spriegums is pīķis to pīķa vērtība starp virsotnes un ielejas of the ripple, and its size is related to the capacity and quality of ieeja un izeja kondensatori of pārslēgšana barošana padeve.
There are two reasons for noise generation: one is generated by the switching power supply itself; Another type is interference from external electromagnetic fields (EMI), which can enter the switching power supply through radiation or input through power lines. The noise generated by the switching power supply itself is a high-frequency pulse train caused by sharp pulses generated at the moment of switch conduction and cutoff, also known as switching noise. The frequency of the noise pulse train is much higher than the switching frequency, and the noise voltage is its peak to peak value. The amplitude of noise voltage is largely related to the topology of the switching power supply, the parasitic state in the circuit, and the design of the PCB.
2, Measures to reduce ripple and noise voltage:
In addition to switching noise, the switching power supply input in the AC/DC converter undergoes full wave rectification and capacitor filtering, and the current waveform is pulse, as shown in Figure 17 (Figure a shows the full wave rectification and filtering circuit, and b shows the voltage and current waveforms). There are higher-order harmonics in the current waveform, which will increase the noise output. A good switching power supply (AC/DC converter) has added a power factor correction (PFC) circuit in the circuit, making the output current approximate sine wave, reducing high-order harmonics, and increasing the power factor to around 0.95, reducing pollution to the power grid.
