Now on this issue, there are many different specious argument, it was said: In the LED volt-ampere characteristics, the voltage is set, also set the current. Therefore, using constant pressure and constant-current effect is the same. Some people say that LED in parallel should be used when constant pressure supply, and the LED in series should be used when constant current power supply; Some people say that because the LED is a constant current device, so use the constant current source power supply; Some people say that, using electricity supply should be used when constant voltage power supply when using battery power, it should be constant current power supply. As to why such a request, it seems that no one did not understand.

So, in the end that it should be constant voltage power supply, or a constant-current power supply do?

First, look at the LED in the end what kind of device. Because the LED's brightness and its forward current is proportional to, and some LED's structure determines its heat dissipation is power. Therefore, most of the LED will give rated current, for example, Φ5 to 20mA, 1W for 350mA and so on, but that does not mean that LED only work on these rated current, but does not mean that LED is a constant current device. For example, Cree's 1-watt LED and 3-watt LED is the same model, the current increased from 350mA to 700mA, power from 1W to increase into the 3W, so the LED can operate at 350-700mA any value between.

To understand this problem we must first know the volt-ampere characteristics of LED.

1. LED volt-ampere characteristics

LED's Chinese name is a light-emitting diode, so it is itself a diode. Its volt-ampere characteristics of the diode volt-ampere characteristics and the general very similar. But is usually a very steep curve. For example, a 20mA straw hat LED volt-ampere characteristic shown in Figure 1.