How to Distinguish Between Constant Current and Constant Voltage LED Power Supply?
LED driver/LED power supply is a power converter that converts the electric
supply into a specific voltage and current to drive the LED light, and is the electronic device that makes the LED light-emitting or LED modules work properly. There are three basic components: the light-emitting chipset; the transformer that regulates light source; and the radiators for cooling devices. As LED is a characteristic-sensitive semiconductor device and has negative temperature characteristics, the LED power supply (also called LED driver) is the protection of its stable working condition during the application. LED components are very strict on the LED power supply. LED is different from ordinary incandescent bulbs, can be directly connected to 220V AC electric supply. LEDs are driven by low voltage and must be designed with complex conversion circuits, different LED lights should be equipped with different LED power adapters. At present, led power supply that can convert high voltage to low voltage can be divided into constant current led power supply and constant voltage led power supply. How to distinguish between constant current and constant voltage power supply?
Constant current led power supply
For LED constant current power supply, the output current is constant with the allowed load and does not change with the load. And the output voltage will change within a certain range with the change of the load resistance. The smaller the load resistance, the lower the output voltage; the larger the load resistance, the higher the output voltage. If it is a constant current source, the output voltage is marked as a range and the output current is marked as a fixed value. Such as output : 350mA 100-200V. The constant current led power supply is usually used in high-power LED lighting products, such as LED street lamp, LED mining lamp, LED floodlight.
The constant current led power supply has the following protections
1.Short -circuit protection. If the output of the constant current led driver occurs abnormality, causing a short circuit to the positive and negative terminals, the constant current led driver circuit will activate the short circuit protection function to prevent permanent damage to the constant current driver circuit from the abnormality.
2.Overload protection. When the VF value of the LEDs in series is within the design voltage range of the circuit, the output current is constant. When the VF value of the LEDs in series exceeds the design voltage range of the circuit, the power supply enters overload protection, and the lights flicker.
3.Over temperature protection. When the operating temperature of the constant current power supply exceeds the design temperature.The current will drop sharply to ensure that the constant current driver circuit is not damaged, and the LEDs will continue to glow at the same time.
For LED constant voltage power supply, the output voltage is constant with the allowed load and does not change with the load. The output current will change as the load increases or decreases. If it is constant voltage source, the output voltage is usually marked with a fixed value and the output current is marked with a maximum value. Such as output: 12V 16.7A. Constant voltage led power supply is usually used in small power LED lights, such as LED module, LED strip, LED strip light, LED plant light, LED wall wash light.
The constant voltage led power supply has the following protection.
1.Short circuit protection. Protection type: It can be automatically restored after the fault is eliminated.
2.Over temperature protection.Protection type: Turn off the output voltage, after the temperature drops, re-energize to restore.
3.Over voltage protection. Output voltage ≥120%-140%, turn off the output,after the abnormality is eliminated, re-energize to recover
4.Over load protection. Load current ≥102%~110%, turn off the output, and automatically recover after the fault is eliminated.
In summary, constant voltage led power supply is often referred to as a regulated power supply, which ensures that the voltage remains constant when the load (output current) varies. Constant current led power supply can adjust the output voltage to keep the output current constant as the load changes.
Constant current: the output current is a constant value plus a deviation of approximately ±5%; the output voltage is generally a range of e.g. (30-45V). Constant voltage: the output voltage is a constant value, the current may be a maximum value