Most switching power supplies are constant voltage power supplies, so you do not need to be careful when connecting to a load, but you may need to be careful when lighting the LED module using a constant current power supply.
This is stated in the LED module manufacturer’s instruction manual, but you will not know it unless you read it carefully.
Order to connect the constant current power supply and the LED module
When connecting the constant current power supply and the LED module, be sure to (1) connect the constant current power supply and the LED, and (2) AC input (plug the power plug into the outlet).
If you connect the constant current power supply and the LED module after AC input to the power supply in the reverse order (with the power plug plugged into the outlet), the charge accumulated in the power supply becomes a surge current and flows to the LED side.
The surge current depends on the model of the power supply, but it is about 10 to 20 times the rated current of the power supply. With a 24V 4A (100W) constant current power supply, a surge current of 40A to 80A will flow to the LED module, causing the LED to burn out. Please note that the electric charge accumulated in the power supply will not disappear until 3 minutes or more have passed after disconnecting the power plug from the AC outlet.
The power supply manufacturer specifies the inrush current that flows to the input side of the power supply as “input surge current” in the specifications, but most general power supplies are constant voltage power supplies and surge current does not flow to the output side. Therefore, the surge current to the output side is not specified in the specifications.
What broke the LED?
It would be nice if the LED did not break and light up due to the surge current flowing, but it lights up with a part of the LED chip burnt. You can see the burn marks on the LED chip with a microscope, but the human eye cannot tell the difference in brightness. If you keep turning on the LED as it is, it usually lasts for several years, but the LED turns off in a few months to half a year.
This is the cause of many of the complaints received by LED module manufacturers. Therefore, the manufacturer is alerting the users, but it seems that many users are using the constant current power supply for the first time and it is not decreasing easily.
Now, the problem here is where the surge current flows through the LED. Of course, most of the time is when the LEDs are installed, but in most cases, after connecting the LEDs in the correct order at the site, the LED module is removed from the power supply and moved as it is without turning off the power to change the installation location of the LEDs. It is a case of connecting to the LED again. (Also, even if the power is turned off, it is the same if the power and LED are connected in a short time.)
In addition, before installing the LED on site, the LED lighting test is performed at the factory, but even here, if the LED is connected while the power is on, the LED will be damaged. After that, even if you connect them in the correct order at the site, the LED will turn off or darken in about half a year.
LED replacement cost
Replacing LED signboards and high-altitude lighting installed in high places is very troublesome. The work must be done or witnessed by an electrician. In high places, it is necessary to rent an aerial work platform (Unic vehicle) and hire an operator (operator of the Unic vehicle), and in some cases, obtain a road permit from the police and hire a guard man for guidance. As an extreme example, it can cost more than ＄5,000 just to replace one LED module or power supply.