In addition to this guide to chargers, I wrote our comprehensive guide to USB-C adapters, cables, and hubsas well as our guide to Thunderbolt 3 docks.
Size and weight of the device was largely determined by the transformer, which in turn was determined by the power output and mains frequency.
Ratings over a few watts made the devices too large and heavy to be physically supported by a wall outlet. The output voltage of these adapters varied with load; for equipment requiring a more stable voltage, linear voltage regulator circuitry was added.
Losses in the transformer and the linear regulator were considerable; efficiency was relatively low, and significant power dissipated as heat even when not driving a load.
Early in the twenty-first century, switched-mode power supplies SMPSs became almost ubiquitous for this purpose. Mains voltage is rectified to a high direct voltage driving a switching circuit, which contains a transformer operating at a high frequency and outputs direct current at the desired voltage.
The high-frequency ripple is more easily filtered out than mains-frequency. The high frequency allows the transformer to be small, which reduces its losses; and the switching regulator can be much more efficient than a linear regulator.
The result is a much more efficient, smaller, and lighter device. Safety is ensured, as in the older linear circuit, because a transformer still provides galvanic isolation.
A linear circuit must be designed for a specific, narrow range of input voltages e. However, unless very carefully designed and using suitable components, switching adapters are more likely to fail than the older type, due in part to complex circuitry and the use of semiconductors.
Unless designed well, these adapters may be easily damaged by overloads, even transient ones, which can come from lightningbrief mains overvoltage sometimes caused by an incandescent light on the same power circuit failingcomponent degradation, etc.
A very common mode of failure is due to the use of electrolytic capacitors whose equivalent series resistance ESR increases with age; switching regulators are very sensitive to high ESR the older linear circuit also used electrolytic capacitors, but the effect of degradation is much less dramatic.
Well-designed circuits pay attention to the ESR, ripple current rating, pulse operation, and temperature rating of capacitors. Safety — External power adapters can free product designers from worrying about some safety issues.
Much of this style of equipment uses only voltages low enough not to be a safety hazard internally, although the power supply must out of necessity use dangerous mains voltage.
If an external power supply is used usually via a power connector, often of coaxial typethe equipment need not be designed with concern for hazardous voltages inside the enclosure. This is particularly relevant for equipment with lightweight cases which may break and expose internal electrical parts.
Heat reduction — Heat reduces reliability and longevity of electronic components, and can cause sensitive circuits to become inaccurate or malfunction. A separate power supply removes a source of heat from the apparatus. Electrical noise reduction — Because radiated electrical noise falls off with the square of the distance, it is to the manufacturer's advantage to convert potentially noisy AC line power or automotive power to "clean", filtered DC in an external adapter, at a safe distance from noise-sensitive circuitry.
Weight and size reduction — Removing power components and the mains connection plug from equipment powered by rechargeable batteries reduces the weight and size which must be carried.
Ease of replacement — Power supplies are more prone to failure than other circuitry due to their exposure to power spikes and their internal generation of waste heat. External power supplies can be replaced quickly by a user without the need to have the powered device repaired.
AC adapter supporting four different AC plug systems Configuration versatility — Externally powered electronic products can be used with different power sources as needed e.
A single version of a device may be used in many markets, with the different power requirements met by different external power supplies, so that only one version of the device need be manufactured, stocked, and tested. If the design of the device is modified over time a frequent occurrencethe power supply design itself need not be retested and vice versa.
Constant voltage is produced by a specific type of adapter used for computers and laptops. These types of adapters are commonly known as eliminators. Size — Power supplies which plug into the mains directly without using a plug on a cable true wall warts are bulkier than bare plugs; sometimes they are too large to plug into power sockets with restricted space, or into adjacent sockets on power strips due to the fact that they can block other plugs also.
Weight — Some AC adapters can be heavy, exerting excess weight on the power socket this depends on the socket design of the country in question. Some external power supplies are "power bricks" also known as "line lumps" having a short AC cord so they can lie on the floor, thus relieving strain, at the expense of clutter.
Other wall-hanging types are made long and thin, minimizing the leverage of their weight vector that pulls the plug out, but exacerbating the size problem. The weight for equipment that must be carried e. Inefficiency — Some idling power is wasted as the power supply is left running when the equipment power switch is off or the equipment is disconnected from the power supply.
In recent years, it has become common for equipment with internal supplies to share this problem due to the use of a "soft" power switch. Confusion — External power supplies are often generic and not clearly marked to identify the equipment they are designed to power. It is very easy to separate power supply and equipment, and can be difficult to re-match the many devices with their power supplies.
Compatibility problems — There is no standardization of connectors; the same connector is often used for different voltages, and for both DC supplies and AC-to-AC transformers. Incompatible voltage or polarity may be present on physically interchangeable connectors.
This easily leads to using the wrong power supply, which can destroy equipment.Universal Power Supply. • At the maturity stage.
cost of stock out is lower than compared to at beginning because there is less fear of losing sales. However better forecasting of demand helps lower the level of inventory.
extra cost can be a real heartoftexashop.com and Benefits over Product Life cycle • At the beginning of the life cycle. Aug 26, · Edit Article How to Diagnose and Replace a Failed PC Power Supply. In this Article: Diagnosing a Failed PC Power Supply Removing a Failed PC Power Supply Replacing a Failed PC Power Supply Community Q&A When a PC power supply dies or Views: K.
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