Power adapter detection method
1. Sampling
Sampling inspection is a widely used inspection method in production. In the mass production process of electronic products, it is impossible to carry out a full inspection and there is not much time. Normally, several samples can be taken from the inspected product for inspection, i.e. sampling inspection.
Sampling inspection should be carried out under the premise of mature product design, standardized process, stable equipment and reliable tooling. The sampling quantity should be determined according to the base of the inspected product and the sampling standard in the national standard. When taking samples, they should not be taken from products produced in succession, but from random samples from that batch. The sampling results shall be recorded, and the unqualified products shall be judged according to the relevant product unqualified judgment standards.
2. Full inspection
Full inspection is the inspection of 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. As a rule, a full inspection is carried out only for military products and other products with particularly high reliability requirements, prototypes, and products produced after changes in production conditions and production processes. The quality of electronic products is usually judged by the Product Conformity Level (AQL). The product quality indicators of different quality requirements are different, 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 sensing method for power adapters
1. Detect the resistance current
The sense resistor, which is the current sense element, produces the lowest detection error (typically between 1% and 5%) and a very low temperature coefficient of approximately 100ppm/°C (0.01%). In terms of performance, it provides the most accurate power supply, which helps to achieve extremely precise supply current limiting, and also facilitates precise current sharing when multiple power supplies are connected in parallel.
2. Current detection based on power MOSFET
Current sensing using MOSFET RDS(ON) allows for simple and cost-effective current sensing. LTC3878 is a device that takes this approach. It uses a constant on-time valley mode current sensing architecture. The top switch is on for a fixed period of time, after which the bottom switch is turned on, and its RDS voltage drop is used to detect the current trough or the lower current limit.
3. Inductive DCR current detection
Inductive DC resistive current sampling uses the parasitic resistance of the inductor winding to measure the current, eliminating the need to detect the resistance. This reduces component costs and improves power efficiency. The inductive DCR of a copper wire winding typically has less device-to-device variation compared to MOSFET RDS(ON), although it still varies with temperature. It is favored in low output voltage applications where any voltage drop on the sense resistor represents a significant portion of the output voltage.
Laptop power adapter detection
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's not working, try reinstalling the power adapter or battery. A possible problem is a warped power connector or reduced elasticity of the battery contacts.
2. If the power supply or battery is well connected, 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 differs significantly from the product nominal, the damaged power adapter or battery needs to be replaced.
3. If the above detection steps are normal, it can be inferred that the problem is on the laptop power strip or motherboard. Here you need to open the laptop case and check that the power strip and motherboard are in good contact.
4. If the power strip and the battery are in good contact, use the common DIY replacement method to check whether the power strip is normal. If it is not normal, replace it.
