Technické pravidla a aplikace z PCB rozvržení pro přepínání napájení zdroje
V dnešní době, due to the elektromagnetické vlny generované by spínání napájení zdroje, který ovlivňuje normální provoz jejich elektronika produkty, správně PCB layout technologie pro napájení zdroje has staly staly velmi důležité.
In many cases, a perfectly designed power supply on paper may not work properly during initial debugging due to many issues with the PCB layout of the power supply. For example, in the schematic diagram of a step-down switching power supply on a consumer electronic device, the designer should be able to distinguish between components in the power circuit and those in the control signal circuit on this circuit diagram. However, if the designer treats all components in this power supply as if they were components in the digital circuit, the problem can be quite serious. The layout of switch power supply PCB is completely different from that of digital circuit PCB. In digital circuit layout, many digital chips can be automatically arranged through PCB software, and the connecting lines between chips can be automatically connected through PCB software. The switch power supply produced by automatic typesetting will definitely not work properly. Therefore, designers need to master and understand the correct PCB layout technical rules for switching power supplies.
Technické pravidla pro PCB rozvržení přepínání napájení napájení
Kapacita obtok keramický kondenzátor by měl ne být také velký % 2c a jeho parazitní série indukčnost by měla být minimalizována jako mnoho jako možné. paralelní připojení více kondenzátory může zlepšit vysoká frekvence impedance charakteristiky kondenzátory
Když the operační frekvence of a kondenzátor is below fo, the kapacita impedance Zc klesá s zvýšení of frekvence; Kdy the provozní frekvence of the kondenzátor je nad fo, the kapacita impedance Zc bude stane jako the indukčnost impedance a zvýšení s the zvýšení of frekvence; Kdy the provozní frekvence of a kondenzátor přístupy fo, the impedance of the kondenzátor is equal to its equivalent series resistance (RESR).
Electrolytic capacitors generally have a large capacitance and a large equivalent series inductance. Due to its low resonant frequency, it can only be used for low-frequency filtering. Tantalum capacitors generally have larger capacitance and smaller equivalent series inductance, so their resonant frequency is higher than that of electrolytic capacitors and can be used in medium to high frequency filtering. The capacitance and equivalent series inductance of ceramic capacitors are generally very small, so their resonant frequency is much higher than that of electrolytic capacitors and tantalum capacitors, so they can be used in high-frequency filtering and bypass circuits. Due to the fact that the resonant frequency of small capacitance ceramic capacitors is higher than that of large capacitance ceramic capacitors
Kdy výběr bypass kondenzátory, it is not adferable to jednoduše use ceramic capacitors with high capacitance values. In order to improve the high-frequency characteristics of capacitors, multiple capacitors with different characteristics can be connected in parallel for use. Figure 1 (a) shows the better impedance effect after multiple capacitors with different characteristics are connected in parallel. It je není obtížné k pochopit důležitost tohoto rozvržení pravidlo skrz analýza. Obrázek 1 (b) ukazuje rozdílné zapojení metody od vstup výkon (VIN) to zatížení (RL) on a PCB. In order to redukce the ESL of the filter capacitor (C), the lead length of the capacitor pin should be minimalized as much as possible, while the routing from VIN positive to RL and from VIN negative to RL should be be as blízko as možné.
