Power supply circuit board layout technology rules and applications
Since switching power supplies generate electromagnetic waves that can affect the proper functioning of their electronics, proper power supply PCB layout techniques become very important.
In many cases, a power supply that is perfectly designed on paper may not work properly during initial commissioning due to a number of problems with the PCB layout of the power supply. For example, for a consumer electronic device on the step-down switching power supply schematic, the designer should be able to distinguish between the power circuit components and control signal circuit components on this circuit diagram, but if the designer will be all the components of this power supply as if they were digital circuits, the same components, then the problem will be quite serious. Switching power supply PCB layout and digital circuit PCB layout is completely different. In the digital circuit layout, many digital chips can be automatically arranged through the PCB software and the connection line between the chip can be automatically connected through the PCB software. With the automatic layout of the layout of the switching power supply can not work properly. Therefore, designers need to master and understand the correct switching power supply PCB layout technology rules.
Switching power supply PCB layout technology rules
Bypass ceramic capacitor capacity can not be too large, and its parasitic series inductance should be minimised. Multiple capacitors in parallel can improve the high frequency impedance characteristics of capacitors
When a capacitor operating frequency below fo, capacitance impedance Zc with the rise in frequency and reduce; when the capacitor operating frequency above fo, capacitance impedance Zc will become like the inductive impedance with the rise in frequency and increase; when the capacitor operating frequency close to fo, capacitance impedance is equal to its equivalent series resistance (RESR).
Electrolytic capacitors generally have a large capacitance and a large equivalent series inductance. Because of its low resonant frequency, it can only be used for low frequency filtering. Tantalum capacitors generally have a large capacitance and a small equivalent series inductance, so their resonant frequency will be higher than that of electrolytic capacitors, and they can be used in medium and high frequency filtering. Porcelain chip capacitor capacitance and equivalent series inductance are generally very small, so its resonance frequency is much higher than electrolytic capacitors and tantalum capacitors, so it can be used in high-frequency filtering and bypass circuits. As the resonant frequency of small capacitance ceramic capacitors will be higher than the resonant frequency of large capacitance ceramic capacitors, so in the Selection of bypass capacitors can not just choose the capacitance value is too high ceramic capacitors. In order to improve the high-frequency characteristics of capacitors, several capacitors with different characteristics can be used in parallel.
