When designing high current power supply, MOSFET is difficult to determine. This is especially true in laptops, where heat sinks, fans, heat pipes, and other means of cooling are usually reserved for CPUs.
In this way, the power supply design is often challenged by such unfavorable factors as narrow space, static airflow and heat from other nearby components. Moreover, except for a small amount of copper film on the printed circuit board under the power supply, there is no other means to help dissipate power.
When selecting MOSFETs, the first step is to select devices with sufficient current processing capacity and sufficient heat dissipation channels. The necessary heat consumption and sufficient heat dissipation path shall also be considered quantitatively.
This paper will explain the power consumption calculation of MOSFETs and determine their operating temperature. Then, by analyzing a design example of a 30A single phase in a polyphase, synchronous rectifier, step-down CPU core power supply, these concepts are further clarified.
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