electronic control gear (ECG)
LED drivers are analogballasts required for the operation of LED luminaires. They provide the correct operating voltage of 12 V or 24 V or the correct operating current. Light emitting diodes have exponential I-V characteristics and must be driven with a constant current, Constant Current( CC), because of the voltage dependence of their color and junction temperature.
The brightness of the LED can be changed by changing the constant current or by switching the LED on and off using pulse width modulation. The constant current of an LED driver can be generated by a series resistor that reduces the voltage and limits the current to a certain amount. This arrangement has the advantage of being simple and inexpensive, but on the other hand it reduces efficiency due to the voltage drop.
Voltage reduction can likewise be accomplished by another method of regulating the voltage of a higher supply voltage to a lower one. To ensure that no unnecessary energy is dissipated as heat in the process, there are clocked LED drivers with high efficiencies.
Switched- mode LED drivers are similar in function to switched-mode power supplies. AC voltage is rectified into DC voltage, which is clocked and transformed at a higher frequency and supplies the light emitting di ode as a clocked constant current source. Corresponding circuits have an efficiency of over 90 %, depending on the clock frequency and circuit technology.