Four major reasons for the heating of power modules

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Four major reasons for the heating of power modules [Copy link]

When you touch the surface of the power module, it feels hot. Is the module broken? Wait a minute, it is a little hot, just because it is working hard. But high temperature has a great impact on the reliability of the power module! Based on the knowledge of thermal design of power modules, this time, we will take a look at the causes of power module heating.

The power module has energy loss in the process of voltage conversion, which generates heat energy and causes the module to heat up, reducing the conversion efficiency of the power supply, affecting the normal operation of the power module, and may affect the performance of other surrounding devices. This situation needs to be checked immediately. But under what circumstances will the power module heat up seriously? The specific reasons are as follows:

1. Using a linear power supply

The working principle of the linear power supply is shown in Figure 1. The output voltage is changed by adjusting the adjustment tube RW. Since the adjustment tube is equivalent to a resistor, it will heat up when the current passes through the resistor, resulting in low efficiency.

Figure 1 Schematic diagram of linear power supply

[p=null, 2, To prevent the power module from overheating, the following measures can be taken: enlarge the heat sink, implement air cooling, use thermal conductive materials (thermal grease, thermal conductive potting glue), and use switching power supply. 63)]2. Load is too small

The power supply is lightly loaded, that is, the load impedance of the power supply circuit is relatively large, and the output current of the power supply to the load is relatively small. Some power supply circuits do not allow light loads of the power supply, otherwise the DC working voltage output by the power supply circuit will increase a lot, causing damage to the power supply circuit. Generally, power modules have a minimum load limit, which varies from manufacturer to manufacturer and is generally around 10%.

If the output load is too light, it is recommended to connect a dummy load resistor in parallel to the output end, as shown in Figure 2. The sum of the dummy load resistor power plus the actual load power>10% load.

[color=rgb(63, 63, Figure 2 The load is too small, parallel dummy load

Figure 2 The load is too small, parallel dummy load

63)]3. Load overcurrent

Power overload is the opposite of the light load situation. It means that the load circuit of the power supply circuit is short-circuited, causing the power supply circuit to output a large current that exceeds the range that the power supply can withstand.

For power modules without overcurrent protection, the simplest way to output voltage regulation, overvoltage and overcurrent protection is to connect a linear regulator with overcurrent protection to the input end, as shown in Figure 3.

[p=null, 2,Figure 3 Load overcurrent, add linear regulator

63)]Fourth, the ambient temperature is too high or the heat dissipation is poor

Before using the module power supply, be sure to consider the temperature level of the power module and the actual required operating temperature range. Perform derating design according to the load power and the actual ambient temperature.

For example, the derating curve of ZLG Zhiyuan Electronics' P_FLS-1W is shown in Figure 4 below. It can be clearly seen from the figure that the operating temperature range is -40~105℃. When the temperature is above 85℃, the power needs to be reduced. At 105℃, the maximum allowable output power is 0.8W.

Figure 4 Temperature derating curve of P_FLS-1W

dahui2010

Thanks for sharing! I am very happy to learn some power knowledge!

qwqwqw2088

Is too small a load also the reason for the power module to heat up?