LED The lamp power supply adopts the constant current drive mode, that is, the output current is constant, and the output voltage changes with the load change. In the case of measurement, the measured voltage value is the 310V DC voltage after AC 220V rectification.
LED constant current power supply
The above picture is a simple LED constant current power supply circuit with RC The buck scheme is implemented. The magnitude of the output current depends only on the capacitance of the capacitor. According to the capacitive reactance of the capacitor to the output current, the output voltage depends on the output voltage. load,The larger the load resistance, the higher the output voltage, the maximum (DC 310V) when the load is open, and the smaller the output voltage.
In fact, most LED lights are powered by a constant current drive, because LEDs illuminatediode is not fixed. When the voltage is constant and the temperature of the arc tube rises, its working current will increase significantly, but the brightness will not increase, so it will only cause The LED temperature rise is greater, and the light decay is accelerated, which easily causes the LED to be damaged. Therefore, the LED power supply is basically driven by a constant current source.
The method of distinguishing LED power supply from constant current source and constant voltage source is very simple. It only needs to check the output voltage marked on the power supply. Generally, the constant current source is marked in the output voltage column. A voltage range, as shown in the title (DC 125V ~ 140V); and a constant voltage source marked with a fixed voltage value, such as DC 120V.
The constant current source is forbidden to open the road. The method used by the subject is incorrect. It is easy to cause power damage. The correct method should be to connect the ammeter to the measurement output. Current.