How to layout, wiring, and select switch mode power supplies
Switching power supply is a highly efficient power converter, with a theoretical value close to 100% and a wide variety of types. According to topological structure, there are Boost, Buck, Boost Buck, Charge dump, etc; According to the switch control method, there are PWM and PFM; According to the category of switch tubes, there are BJT, FET, IGBT, etc. This discussion focuses on the commonly used PWM control Buck and Boost types for data card power management.
The main components of a switching power supply include: input source, switching transistor, energy storage inductor, control circuit, diode, load, and output capacitor. At present, the vast majority of semiconductor manufacturers integrate switch transistors, control circuits, and diodes into a CMOS/Bipolar process power management IC, greatly simplifying external circuits.
Among them, the energy storage inductor, as a key component of the switching power supply, plays an important role in the performance of the power supply, and is also a key focus and debugging object for product design engineers. With the development of consumer electronic devices such as mobile phones, PMPs, and data cards, the size is moving towards lightweight, thin, compact, and fashionable trends, which is in contradiction with the larger capacity and larger size of inductors and capacitors required for stronger product performance. Therefore, how to reduce the size of the inductor (occupied PCB area and height) of the switching power supply while ensuring product performance is an important topic to be discussed in this article. Designers will have to make a trade-off between circuit performance and inductor parameters.
Everything has two sides, and switching power supplies are no exception. A bad PCB layout and wiring design not only reduces the performance of the switching power supply, but also strengthens EMC, EMI, grounding, etc. Another important topic to be discussed in this article is the issues to be paid attention to and the principles to be followed when laying out and wiring switch mode power supplies.
One switch power supply duty cycle D, inductance value L, efficiency η Formula derivation
