How to distinguish led switching power supply belongs to constant current or constant voltage mode? First of all, it's much easier to understand the meaning of constant current and constant voltage. Constant current refers to constant current, which means that the output current is constant and will not change with the change of load. Constant voltage means that the output voltage is constant and will not change with the load.

For LED constant current power supply, the output current is constant and does not change with the load when the load is allowed.

For LED constant voltage power supply, the output voltage is constant and does not change with the load when the output power of the power supply is allowed.

After understanding the basic concepts, how to distinguish them?

1. Distinguish directly from the index parameters printed on the LED power supply

If it is a constant voltage source, the output voltage is usually marked with a fixed value, and the output current is marked with a maximum value. As shown in the figure below, the fixed value of output voltage is 45vdc, and the maximum value of output current is Max: 0.5A.

If it is a constant current source, the output voltage is the range and the output current is the fixed value. As shown in the figure below, LED constant current source, the output terminal is marked with voltage range: dc72 ~ 125V, and the current is marked with fixed value: 300mA.

2. Connected with the load measurement, when the load changes, a constant voltage source and a constant current source are the same. First, use a multimeter to measure the no-load output voltage of the LED power supply (if it is a constant voltage source, the voltage is the output voltage, if it is a constant current source, the voltage is the maximum output voltage). Then, according to the measured voltage, estimate the appropriate load connected (pure resistance can be connected), for example, connect 50 Ω and 100 Ω resistance respectively, and measure the voltage. If the voltage is constant, it is a constant voltage source, if the voltage changes linearly Note that the load should be close to the output power of the power supply as far as possible, but should not exceed the output power of the power supply.

More in-depth understanding of LED constant current source: constant current means constant current. According to u = I * r, since I is constant, the output voltage is proportional to the load, and the greater the impedance of the load, the greater the output voltage. For example, if the output voltage of one LED in series is 3V, then the output voltage of two LEDs in series is 6V, three LEDs in series is 9V, and so on, until the maximum load capacity of the constant current source.

Conclusion: constant current source is constant output current, constant voltage source is constant output voltage, after understanding their differences, it is much easier to distinguish them. LED lamps with better quality are generally driven by constant current source, which has higher stability and longer service life.