Precautions for the use of dcdc power modules and the reasons for burnout

dcdc power moduleWith multiple advantages such as high integration, high reliability, and simplified design, it is favored by many electronic designers. Although the power module has simple application circuit and simple operation, it often encounters some common problems in application. In view of this article, a detailed analysis of the precautions for the use of dcdc power modules and the reasons for burnout are carried out.

1. Because the dcdc power module is completed by using a switching oscillator circuit, it will also cause common mode and differential mode noise interference. For occasions with high requirements for ripple noise, an external passive can be connected to the output of the dcdc power module. LC filter network or RC (large loss) to further reduce the power ripple noise, but it should be noted that the resonance frequency of L itself is much higher than the switching frequency of the module, and the current value allowed is generally more than twice the input current of the module. The internal resistance should be small to reduce DC loss.

2. In order to ensure the reliability of the module power supply for long-term operation, the module operation should be above 10% of the rated power, so as to avoid the module's unloaded or light load causing the output voltage to be unstable and affecting the circuit operation. If the load power consumption is indeed small , It can be used with an external dummy load method to combine +Vo and 0V and -Vo and 0V at the output end. A dummy load (resistance) of 10% of the rated power can be used to improve the reliability of the product.

3. The external capacitors C2 and C3 of the dcdc power module use low internal resistance tantalum capacitors. The recommended capacitance value is 0.47uF.

Excessive capacitance will cause over-current at the start of the engine and damage the module.

4. Most power modules have no current sharing function and cannot be used directly in parallel to increase the output power.

5. Many customers use power modules for the purpose of achieving power isolation. Choose different power supplies according to different isolation requirements, usually 1000VDC, 3000VDC, 4000VAC and so on. At the same time, when designing the layout, leave enough creepage distance between the input and output to avoid weakening the isolation effect.

6. General power modules have a wide voltage input range, but when the input voltage exceeds the larger input voltage set by the power module, it may cause permanent damage to the power supply. If the front-end input power is unstable or the fluctuation range exceeds a larger input voltage, you can add a corresponding TVS tube or overvoltage protection circuit at the input.