Constant voltage source and constant current source

1) constant voltage power supply in the case of the load, the output voltage is constant, does not change with the load changes, usually used in low-power LED module, low-power LED light bar more. Constant voltage power supply is what we often say that the power supply, to ensure that the load (output current) changes in the case, keep the voltage unchanged.
 
 
2) constant current power supply in the case of the load, the output current is constant, will not change with the load changes, usually used in high-power LED products in the high-end low-power LED products will also use the LED Constant current power supply. If you want to extend the life of LED products, LED power supply selection is very important, and constant current source is the best choice for LED like. Constant current source is in the case of load changes, can adjust their own output voltage, making the output current remains unchanged.
 
We see the switching power supply, basically all are constant voltage power supply. Constant current power supply switching power supply is actually on the basis of constant voltage source, the internal output circuit, coupled with the sampling resistor, the circuit to ensure that the sampling resistor on the same pressure drop to achieve constant current output.
 
How to distinguish between constant voltage source and constant current source by parameters:
Get an LED power supply, find brand name parameters. Find the output voltage of this key
Parameter: If its voltage is nominal is a constant value, it is a constant voltage source.
If it is a range value, it is a constant current source.
For example: there is a power supply of its output voltage is 12V,
We are sure that this is a constant voltage power supply, if it is nominal 30-80V, then this power must be a constant current power supply.
 
Constant voltage power supply and constant current power supply advantages and disadvantages:
Constant voltage power supply (regulated power supply): able to load a constant voltage power supply. The ideal internal resistance of the constant voltage power supply is zero and can not be shorted when used.
Constant current power supply (constant current source): A power that can output a constant current to the load. The ideal internal resistance of the constant current power supply is infinite and can not be used when used