Power adapter detection method

Power adapter detection method

1. Sampling

Sampling inspection is a widely used inspection method in current production. In the mass production process of electronic products, it is impossible and there is not much time for full inspection. Usually, several samples can be taken from the product to be inspected for inspection, that is, sampling inspection.

Sampling inspection should be carried out on the premise of mature product design, process specification, stable equipment and reliable tooling. The number of samples taken should be determined according to the base of the products to be inspected and the sampling standards in the national standards. When the sample is drawn, it should not be drawn from the continuously produced products, but should be randomly drawn from the batch of products. The results of the sampling inspection should be recorded, and the failures in the sampling inspection products should be judged according to the relevant product failure judgment standards.

2. Full inspection

Full inspection is to inspect all products. Full inspection can improve the reliability of the product, but it will consume a lot of manpower and material resources and increase the production cost of the product. Usually, only military products and other products with particularly high reliability requirements, trial products, and products produced after changes in production conditions and production processes are fully inspected. The quality of electronic products is usually judged by the product qualification level (AQL). Products with different quality requirements have different quality indicators, and the inspection should be determined according to the number of A and B failures allowed by the inspected product under the specified AQL value.

Current detection method of power adapter

1. Detecting resistance current

The sense resistor as a current sense element produces the lowest sense error (usually between 1% and 5%) and a very low temperature coefficient of about 100ppm/°C (0.01%). In terms of performance, it provides the most accurate power supply, helps achieve extremely accurate supply current limiting, and also facilitates precise current sharing when multiple supplies are connected in parallel.

2. Current detection based on power MOSFET

Current sensing with MOSFET RDS(ON) enables simple and cost-effective current sensing. The LTC3878 is a device that uses this approach. It uses a constant on-time valley mode current sense architecture. The top switch is turned on for a fixed time, after which the bottom switch is turned on, and its RDS drop is used to detect the current valley or current lower limit.

3. Inductor DCR current detection

Inductor DC resistance current sensing uses the parasitic resistance of the inductor winding to measure current, eliminating the need for a sense resistor. This reduces component cost and improves power efficiency. Compared to MOSFET RDS(ON), the device-to-device variation of the inductive DCR of the copper wire winding is generally smaller, although it still varies with temperature. It is favored in low output voltage applications because any voltage drop across the sense resistor represents a significant portion of the output voltage.

Detection of notebook power adapters

1. First, you can check whether the power adapter or laptop battery is in good contact by gently shaking the power connector or battery. If it is not normal, try to reinstall the power adapter or battery. Possible problems are deformation of the power connector or reduced elasticity of the battery contacts.

2. If the power supply or battery connection is good, you can use a multimeter to measure the output voltage of the power adapter or battery, mainly to check whether the output voltage is stable, and whether the actual output voltage value is consistent with the nominal voltage of the power supply. If the output is unstable or the actual output voltage is consistent with the product If the nominal difference is very different, the damaged power adapter or battery needs to be replaced.

3. If the above detection steps are all normal, it can be inferred that the problem is on the notebook power board or the motherboard. Here, you need to open the notebook computer case and check whether the power board and the motherboard are in good contact.

4. If the power board and the battery are in good contact, check whether the power board is normal with the replacement method commonly used by DIY. If it is not normal, replace it.