Four major reasons for power module heating

fish001

Four major reasons for power module heating [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 power module thermal design, this time, we will look at the reasons that cause the power module to heat up.

　　The power module loses energy during the voltage conversion process, generating heat that causes the module to heat up, reducing the power conversion efficiency, 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. Linear power supply is used

　　The working principle of a 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 generate heat when the current passes through the resistor, resulting in low efficiency.

Figure 1 Schematic diagram of linear power supply

　　In order 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 a switching power supply instead.

　　2. The 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, as shown in Figure 2. The sum of the dummy load resistor power plus the actual load power should be > 10% load.

Figure 2 The load is too small, and a dummy load is connected in parallel

　　3. Load overcurrent

　　Power supply overload is the exact opposite of power supply underload. It means that there is a short circuit in the load circuit of the power supply circuit, 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 achieve 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.

Figure 3 Load overcurrent, add linear regulator

　　4. The ambient temperature is too high or the heat dissipation is poor

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