Thermal design of the power modules




Thermal design of the power modules.How to ensure the long-term reliable operation of electronic equipment has been plaguing engineers.Simplifying heat dissipation is one of the important features of the module power supply.Although there are many reasons for the failure of electronic equipment,high temperature is the most important factor,and the impact of temperature on electronic equipment is as high as 60%.Due to the high efficiency of the converter,the heat generated is small and the ultra-thin package provides a heat-dissipating interface for easy installation and electrical isolation.Proper cooling measures can improve the operating conditions of the converter,increase the mean time between failures(MTBF)of the system,reduce the size of the converter module,and reduce costs and extend service life.The effective cooling method of the module is described below.

The reason why the power module generates heat:

Not all of the input power of the module power can be converted into output energy,and a part of the input power will be lost in the converter.The ratio of the output power of the power module to the input power is called the efficiency of the power module.Efficiency is the most basic quality factor of a power module.It can be used to indicate the direct relationship between converter output power and power consumption.When estimating the cooling requirements,the worst-case power consumption and expected load power should be calculated first based on the converter efficiency.

Some basic principles of thermal design of power modules:

1.From the perspective of facilitating heat dissipation,the printed plate is preferably installed upright,and the distance between the plate and the plate is generally not less than 20 mm.

2.In the horizontal direction,the high-power devices are placed as close as possible to the edge of the printed board to shorten the heat transfer path;in the vertical direction,the high-power devices are placed as close as possible to the top of the printed board to reduce the temperature of other devices while these devices are operating.Impact.

3.The devices on the same printed board should be arranged as far as possible according to their heat generation and heat dissipation.Devices with low heat generation or poor heat resistance(such as small signal transistors,small scale integrated circuits,electrolytic capacitors,etc.)should be placed.The uppermost flow(at the inlet)of the cooling airflow,the device that generates a large amount of heat or heat(such as a power transistor,a large-scale integrated circuit,etc.)is placed at the most downstream of the cooling airflow.

4.The temperature-sensitive device should be placed in the lowest temperature region(such as the bottom of the device).Do not place it directly above the heat-generating device.Multiple devices are preferably staggered on a horizontal surface.

5.The heat dissipation of the printed circuit board in the equipment mainly depends on the air flow,so the air flow path should be studied during the design,and the device or printed circuit board should be properly configured.When the air flows,it tends to flow in a place with low resistance.Therefore,when configuring the device on the printed circuit board,avoid leaving a large air space in a certain area.The same problem should be noted in the configuration of multiple printed circuit boards in the whole machine.

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