Laptop power adapters generally get quite hot during operation, but if they become excessively hot or the adapter’s casing develops bulges, that’s an abnormal condition.

I. The adapter’s high fever is caused by factors at two levels;
1. The adapter has poor heat dissipation, or design flaws cause it to generate excessive heat.
In such cases, it’s generally effective to retrofit the adapter with a heatsink or use a cooling fan to reduce the temperature—this approach works exceptionally well.
2. The adapter’s load (such as the laptop’s built-in DC/DC conversion power circuit, high-voltage board power circuit, and backlight power circuit) has poor characteristics, or one of its components is damaged or malfunctioning.
Among the power supply circuits mentioned above, the output power regulating tube and its coupling capacitor are the components most prone to common failures.

This component may cause a sharp increase in leakage current (such as stray current), thereby reducing the adapter's output power efficiency. As a result, the adapter is forced to deliver a significantly higher rated power output to meet the overall device’s power requirements, leading to overheating.

II. Causes of Overheating in Power Adapters
First, don’t jump to conclusions and assume there’s something wrong with your switching power supply. Instead, take a closer look at what your laptop is doing. Is it engaged in activities like the two USB-connected computer hard drives mentioned earlier—where the CPU is running at full speed, the computer hard drives are frantically reading and writing data, the optical drive is rapidly spinning to read discs, the battery is being charged, loud music is playing, the display brightness is set high, and the wireless receiver is constantly scanning for data signals? It’s crucial to make smart use of battery management and effectively adjust your laptop’s operating state according to your daily tasks.
Second, if the adapter has poor heat dissipation or its design has inherent flaws, it may generate excessive heat. In such cases, you can typically address the issue by installing a heatsink on the adapter or using a cooling fan to reduce its temperature—this approach often yields very good results.
Third, the adapter’s load—such as the built-in DC/DC conversion power circuit in the laptop, the high-voltage board power circuit, and the backlight power circuit—has poor characteristics, or one of its components is damaged or malfunctioning.

Fourth, the output power adjustment transistor and its coupling capacitor—these components—can cause a sharp increase in leakage current (such as stray current), thereby reducing the adapter’s efficiency in terms of power output. As a result, the adapter is forced to deliver significantly more rated power to meet the overall device’s power requirements, leading to overheating.

III. Five Ways to Handle Overheating Power Adapters
First: Create an optimal thermal environment by placing the power adapter in a location that is shielded from direct sunlight and well-ventilated. Remember not to use it for extended periods under high temperatures. If prolonged use is unavoidable, be sure to pay close attention to heat dissipation—consider placing a cooling fan nearby to assist with heat dissipation.
Second: In a high-temperature natural environment, placing the adapter on its side to reduce its contact area with the road surface allows the adapter to dissipate heat more effectively, achieving a practical cooling effect.
Third: Placing a small plastic or metal block between the adapter and the middle of the desktop can help accelerate the release of heat from the adapter.
Fourth: The overheating of the power adapter is usually caused by the simultaneous charging of the battery and power consumption by the computer. We can configure this setting on laptops equipped with battery management software.
Fifth: Regularly use a dry, thin cloth or toilet paper to wipe away dust from the surface of the power adapter, preventing dust from entering the gaps and reducing its heat dissipation performance.
Fourth, there’s another situation that many people often encounter: the nominal voltage of the switching power supply is significantly higher than the operating voltage of the laptop’s battery. Wouldn’t this easily cause damage to the laptop?
In fact, powering a laptop with a switching power supply is different from powering it with a battery. Let’s start with battery power: The output of a battery is pure DC electricity, so you can directly connect it to a DC-to-DC converter module. Moreover, the operating voltage of a battery doesn’t need to be particularly high, nor does it require special design considerations. In modern microelectronic circuits, the operating voltages for both pulse signals and analog signals generally fall within a range centered around 9V. Considering the efficiency requirements and voltage drop across the DC-to-DC converter module, 10.8V is more than sufficient. Furthermore, the chemical electromotive force of lithium batteries determines that a single lithium cell typically outputs only about 3.6V. As a result, many batteries adopt a three-cell series configuration, making 10.8V a very popular battery operating voltage.
Some batteries have tolerance values slightly higher than the non-negative integer 3.6V—for example, 3.7V or 11.2V—primarily to better protect the battery (in rare cases, certain manufacturers even specify the cutoff voltage for charging and discharging as 3.7V). Alternatively, this may be a somewhat opportunistic practice adopted when estimating the battery’s design capacity. If a switching power supply is used, the situation becomes more complicated. First, the input voltage needs to be further regulated and filtered to ensure stable operation even under less-than-ideal power-supply conditions. After voltage regulation, the output voltage is split into two paths: one supplies power to the laptop, while the other charges the battery. The portion supplying power to the laptop experiences the same voltage conditions as if it were directly powered by the battery itself. However, the portion that charges the battery must pass through a dedicated battery-charging control circuit before being applied to the lithium cells; this control circuit can be quite complex. 12V power adapter

The simplified description should include low-to-mid-range voltage regulators, high-precision automatically tunable voltage regulators, thyristor-controlled pulsating power output, voltage regulator output, current feedback, integrated IC-based battery charging process recording and computation, self-feedback functionality for the charging procedure’s key parameters—and thus, the supply voltage must exceed the lithium cell’s operating voltage to provide a sufficient voltage differential capable of powering all components of the charging control circuit. In the end, the actual working voltage applied to the lithium cell will never reach 16V—so friends who are concerned can rest assured.

In fact, as long as the temperature of the power adapter remains within the design specifications—meaning it stays within a normal range—it generally poses no significant risk. Therefore, when designing and manufacturing switching power supply circuits, it’s crucial to select electronic components that are thermally resistant. Of course, it’s also essential to keep the power supply’s temperature within the limits allowed by its application environment. First, the conversion efficiency should be designed to be as high as possible; second, power-switching devices with low losses and minimal power dissipation should be used; and third, effective thermal management must be implemented, with the heat-dissipating surface area maximized. For switching power supplies rated at 100 watts or higher, it’s generally advisable to use metal-cased enclosures or add cooling fans for enhanced heat dissipation. Nowadays, most laptop power adapters have output powers around 60 to 70 watts. They’re typically sealed with fire-retardant, high-temperature-resistant plastic materials, and the heat generated internally is mainly dissipated through the plastic casing. As a result, the surface temperature of the power adapter can become quite high—reaching as high as about 70 degrees Celsius in some cases. Therefore, when using a laptop, try to place the power adapter in a well-ventilated area with good heat dissipation. Never place items like books on top of the power adapter.