Is it correct to use a constant current power supply or a constant voltage power supply to light the LED?


LED Module 

 To turn on the LED module, use the power supply suitable for the LED module. The circuit of the LED module determines whether it is a constant current power supply or a constant voltage power supply, and there is no switching power supply that can be used with either. LED module manufacturers make “dedicated power supplies”, and the power supplies of standard power supply manufacturers are introduced on HP etc. as “recommended power supplies”.

LED module manufacturers use those power supplies to light LED modules to check illuminance, measure temperature, and perform continuous energization tests. Even if the power supply has the same specifications, if you use a power supply that is not recommended by the LED module manufacturer, it will not be covered by the warranty.


Source: Lens Module / AP Japan


Constant Current Power Supply

A constant current is applied to the LED in the forward direction to light it, that is, it glows at a constant current. Since the constant current power supply allows a constant current to flow through the LED, there is no variation in brightness, and the LED module does not require a constant current element or resistor, so power consumption is low. However, the types of constant current power supplies that match the desired current value are limited, and the current values of general constant current power supplies of power supply manufacturers are only 350mA, 700mA, and 1050mA. If there is no suitable current value, there is no choice but to develop it in-house (custom power supply).

Development of power supply takes at least one year from circuit design, trial production to thermal evaluation and noise evaluation, secondary trial production to safety standard / PSE standard application. If you calculate the cost properly, it will cost more than 20 million yen, so you should not use a custom power supply unless you can sell tens of thousands or more units a year. Although there are restrictions on specifications and shapes, it is realistic to change the current and voltage values of a constant current power supply developed by a custom power supply manufacturer.


Constant Voltage Power Supply

 On the other hand, there is a method of lighting the LED module using a constant voltage power supply that is widely distributed in general. In that case, it is necessary to incorporate a constant current element or resistor to keep the current value constant in the LED module. There is a demerit that the voltage varies from LED module to LED module due to the variation of LED voltage (Vf value) and the brightness varies. The voltage of the constant voltage power supply is generally 12V or 24V output. The price of constant voltage power supply is relatively low because each switching power supply manufacturer has released various types of models. However, since it is supposed to be used in equipment and control panels, there are few models that have acquired PSE for the IP standard and power supply when using it outdoors, and it is considerably narrowed down.