laptop Power Adapter Basics
Date:2010-5-21
It seems that the world now revolves around laptop ac adapters or ¡¯power adapters¡¯ as they tend to be called. There are several basic types - despite the fact that the plugs to the equipment may be identical THESE CAN GENERALLY NOT BE INTERCHANGED. The type (AC or DC)£¬ voltage£¬ current capacity£¬ and polarity are all critical to proper operation of the equipment. Use of an improper adapter or even just reverse polarity can permanently damage or destroy the device. Most equipment is protected against stupidity to a greater or lessor degree but don¡¯t count on it.
The most common problems are due to failure of the output cable due to flexing at either the adapter or output plug end.
1. Notebook ac adapter: However£¬ only if the output is stated to be ¡¯AC¡¯ does the device consist of only a "stepdown". These adapters typically put out anywhere from 3 to 20 VAC or more at 50 mA to 3 A or more. The most common range from 6 to 15 VAC at less than 1 A. The regulation is typically very poor so that an adapter rated at 12 VAC may put out 15 VAC with no load and drop to less than 12 VAC at rated load.
2. Laptop DC Power Pack: In addition to a "step down"£¬ these power supplies include at the very least a rectifier and filter capacitor. There may be additional regulation but most often there is none. Thus£¬ while the output is DC£¬ the powered equipment will almost always include an electronic regulation. As above£¬ you may find bad connections or a blown fuse or thermal fuse inside the adapter but the most common problems are with the cable.
3. Switching Laptop AC Adapters: These are complete low power AC-DC converters using a high frequency inverter. Most common applications are laptop computers and notebooks. The output(s) will be fairly well regulated and these will often accept universal power - 90-250 V AC or DC.
*Internal cable problems predominate but failures of the switching power supply components are also possible. If the output is dead and you have eliminated the cable as a possible problem or the output is cycling on and off at approximately a 1 second rate£¬ then some part of the switching power supply may be bad. In the first case£¬ it could be a blown fuse£¬ bad startup resistor£¬ shorted/open semiconductors£¬ bad controller£¬ or other com
ponents. If the output is cycling£¬ it could be a shorted diode or capacitor£¬ or a bad controller. It may just be easier buying a new one at the good prices these days in my opinion.