Types of protection in switching power supplies from MEAN WELL
One of the important requirements that apply to power supplies as part of electrical or electronic systems is to ensure the safety of their use in emergency situations and to prevent failure of the power supply itself and / or the load connected to it. This task is solved by a number of protections that the manufacturer builds into their power supplies of various types of conversion (AC / DC, DC / DC, DC / AC) or chargers. For most power supplies manufactured by MEAN WELL, the set of these protections is universal and is present in full, however, their exact availability and parameters should be specified in the Specification for a specific model of power supply or charger.
A typical arrangement of implemented protection subsystems and interconnections with other blocks in the power supply circuit can be represented by the example of a power supply of the HRP-100 series
HRP-100 Series Power Supply Block Diagram with Implemented Protections
Overload protection (OLP)
The Overload Protection function is one of the main protections of the power supply, since it allows you to equally protect both the power supply itself and the connected load from failure. An overload occurs when a terminal device connected to the power supply fails completely or partially, which leads to a sharp increase in the output current. The built-in protection catches the moment when the output current exceeds the specified parameter (usually 105-150% of the rated power or output current) and limits the output current or turns off the power supply. This feature has been described in more detail previously .
Over voltage protection (OVP)
The overvoltage protection function is also one of the main protections that is found in almost all AC / DC converters - from the most budget sources of the LRS series to the most advanced and functional power supplies of the RSP and HRP series.
An impulse overvoltage occurs when a sudden change in the mode of operation of the load (for example, due to its switching by a relay or a switch), during a short circuit, and in other cases, as a rule, of a switching nature. In these cases, the accumulated energy due to a sharp change in the parameters of the power supply operation mode leads to the development of a transient process with a significant voltage jump, which can damage both the power supply itself and the load fed by it. Therefore, the overvoltage protection unit has a predetermined threshold level (has fixed limits for each output voltage rating of each power supply), at which the power supply is either turned off (the most common way to implement this protection), or it is switched to an intermittent state (hiccup). When the power supply is disconnected, the restart is carried out manually by re-enabling after the malfunction has been eliminated or completed. When switching to intermittent operation, switching on occurs automatically after the fault has been eliminated.
Short circuit protection function - designed to protect the power supply from failure in the event of a short circuit situation on the output contacts of the power supply. This protection can be implemented as part of the Overload protection function, or as a separate block in the power supply feedback loop.
Over temperature (OTP)
Over temperature protection is designed to prevent overheating and damage to the internal components of the power supply, or to prevent shortening of its life due to high ambient temperature, overload, or a malfunction in the power supply (for example, damage to the built-in cooling fan). The fault conditions must be corrected, after which the power supply will automatically recover or restart when manually turned on again after the internal temperature drops below the activation temperature. In general, it takes from several to tens of minutes to cool the power supply to ambient temperature.
Separately for chargers and inverters (DC/AC converters), as well as in some cases for DC/DC converters (by input connection), a separate type of protection is implemented - protection against connection with reverse polarity (reverse polarity protection). The use of this protection makes it possible to avoid failure of the power electronics device in case of an error in connecting an external power source (for an inverter or DC / DC converter) or a battery (for a charger). In most cases, protection against reverse polarity (reverse polarity) is carried out using a special fuse, which must be replaced if such protection has worked.
It is also worth noting the protection that is used in devices using batteries (chargers, power supplies with a UPS function), and which is designed to protect the connected batteries from deep discharge and / or warning about the occurrence of such a situation (Battery Low Protection). For devices of different types, this protection can be implemented with its own characteristics, therefore, for its application, refer to the manufacturer's documentation (Specifications).
In conclusion, it is worth noting that the presence of protection is more likely to avoid failure of the power supply device and / or the load connected to it, but the very fact of its operation does not solve the problem of why this situation arose. Therefore, each fact of operation of a separate protection must be investigated and the conditions for its occurrence must be eliminated - only in this case the power supply system will serve as long and efficiently as possible.
For questions related to the selection and use of MEAN WELL products, please contact Meanwell@chipdip.ru .