All About MEAN WELL Power Supplies
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A TTL signal, Transistor-Transistor-Logic, is a binary signal generated with the help of a transistor turning on or off. 0-0.4V is considered as low state, and 2.7-5V is a high state.
The difference between the TTL and Relay Contact topologies is that since in Mean Well products the TTL signal is created through a transistor or semiconductor, the current capability of the signal is relatively low. In contrary, using Relay Contact method (which uses a metal contact as conductor) allows much higher current to flow.
Depending on the installation environment, you may need IP certified power supplies (IP65/IP67).
Also, waterproof connectors and junction boxes are useful accessories to ensure a reliable operation in damp environments (please refer to the LED power supply installation manual).
Waterproof connector solution
Junction box option
Note that the MEAN WELL product IP level, including IP67, is tested according to IEC 60529. The protection does not guarantee for permanently immersing in the water. Please check the device installation manual for proper suggestions on installation.
How to use a Power Supply to power a special load? (Capacitive load, inductive load, dynamic load, peak load)
Capacitive loads can be found under many different forms: capacitor banks, batteries, and even power supplies themselves are considered as capacitive loads. The principal issue that can appear on such type of load is at PSU start-up: a discharged capacitor basically acts like a short-circuit at start-up, hence it may overload the output.
One solution is either to add current limiting resistors in series with the capacitive load to limit the output current, or to select a power supply with “constant current limiting” overload protection type. This way, the power supply will automatically limit the current to a certain level stated in the specifications:
SPV-150 series specifications
For inductive loads, motors need high current at start-up, therefore a power supply with peak power capability is recommended (or a PSU with constant current limiting overload protection type).
The main issue of dynamic loads is output voltage drop. If the load step is too high in amplitude and too long, it may be able to completely discharge the output capacitors and then create a voltage drop or high ripple at the output. If the frequency of the load changes is high enough, this kind of issue is less likely to happen (please refer to the test reports for more information). One solution could be to put additional capacitors between Power Supply and load.
Some applications may need to draw short peak currents from the power supply. If the PSU overload protection type is hiccup or constant current limiting mode, then it will not be able to provide the current peak needed by the load. Some of our power supplies come with a peak power capability that makes them suitable for these kinds of applications. (e.g. HRP-150N series)
For open-frame power supplies with peak capability, the user should refer to the derating curves, and check the thermal requirements (a fan may be required).
MEAN WELL LED power supply does not have a parallel “current sharing” function, so it is not suitable for parallel connection. For high power requirements, please select higher wattage power supply or divide LED load into smaller subsections to be powered by individual power supplies. Example of such LED configuration can be found in figure 5. As shown in fig. 5, the connection between -V of the LPC-35 units should be severed and not connected in common. On the contrary, small wattage LED loads can be connected in parallel and be powered by a single high wattage power supply. But the ability to divide current evenly must be taken into consideration.
When current drawn exceeds the rating of the PSU, the protection circuit will be triggered to protect the unit against overload/overcurrent.
Protections of overload/overcurrent can be divided into several forms:
(1)FOLDBACK CURRENT LIMITING
Output current decreases about 20% of rated current, shown as curve (a) in the figure below.
(2)CONSTANT CURRENT LIMITING
Output current remains at a constant level and within the specified range while the output voltage drops to a lower level, shown as curve (b) in the figure below.
(3)OVER POWER LIMITING
Output power remains constant. As output load increases, output voltage decreases in proportion, shown as curve (c) in the figure below.
(4)HICCUP CURRENT LIMITING
Output voltage and current keep pulsing ON and OFF repeatedly when protection is activated. The unit automatically recovers when the faulty condition is removed.
Output voltage and current are cut off when output load reaches protection range.
NOTE: Protection mode of some of the products combines with different types of the forms mentioned, such as constant current limiting + shut down.
(1)Auto Recovery: PSU recovers automatically after faulty condition is removed.
(2)Re-power on: PSU restarts by manual AC re-power on after faulty condition is removed.
Note: Please do not operate PSU in overcurrent or short-circuit condition for a long period of time to prevent a shorten lifespan or damaging the PSU.