DC-DC power module fault countermeasures and hazard level classification
A power module is a device that simplifies circuit design. Simply attach the power module to the circuit board and it can be used as a power supply. There are various DC-DC power modules on the market, which have certain differences in structure or power. Although DC-DC power modules have high reliability, they are not immune to damage. So, what problems do DC-DC modules encounter during use?
Several common fault manifestations of DC-DC power modules include a decrease in output voltage during use, module shutdown, module output voltage being too high, module input short circuit, and module output current being too high.
Divided by the degree of danger, the risk of output voltage drop and module shutdown is * low, which can facilitate circuit diagnosis. The following three types of malfunctions are more dangerous.
When the output voltage of the module is too high, it is highly likely to cause the DC-DC power module to burn out the circuit, which is a dangerous fault problem. Generally, protection is achieved through overvoltage protection circuits, or by adding a voltage regulator diode at the output terminal. When designing, it is necessary to choose the parameters of the diode reasonably to prevent changes in the voltage stabilization point due to different temperatures. Some modules come with their own overvoltage protection. Generally speaking, modules below 25W do not have overvoltage protection function, while modules above 25W are designed with overvoltage protection circuit inside. Overvoltage protection points are generally designed for rated voltages ranging from 135% to 145%. During detailed design, it is necessary to confirm whether the module has these functions to avoid duplicate design.
When the input of the module is short circuited, it can cause the printed board to burn out. This serious malfunction can be prevented by placing a fuse at the input end. The fuse tube is generally arranged near the input end of the power module during wiring. The purpose of this design is to reduce the lead inductance of the input line and avoid overvoltage at the input end caused by the lead inductance when the fuse tube melts.
If the output current of the DC-DC power module is too high, it is necessary to choose a power module with overcurrent protection function for design. General power modules have overcurrent protection function, which can be achieved by detecting the primary or secondary current of the transformer inside, but at a certain loss of efficiency. When selecting voltage modules, it is not necessarily better to have a higher power rating. If the derating is too large, during the auxiliary short circuit of the user board, due to the existence of transmission voltage drop, the output current is insufficient to achieve module overcurrent, which may cause chip overheating or even damage.
