Determination of the output parameters
This chapter describes an example of the parameterization of the EL2596-xxxx. The case is considered where one or more LEDs are supplied with a constant current by the EL2596-xxxx in the “Current Control” operation mode.
First of all, the forward voltage UF is to be determined at the operating point of the LED. To this end there is a characteristic curve in the data sheet for the LED that shows the forward current IF as a function of the forward voltage UF. If a current other than the nominal current of the diodes is desired, the corresponding forward voltage is to be taken from the diagram that shows the forward voltage plotted against the forward current of the LED.
For a calculation example, let's assume that the nominal current is 1 A, resulting in a forward voltage of 2.35 V.
Several LEDs of the same type are to be connected in series in the example under consideration.
Thus, the resulting output voltage of the EL2596 Uout corresponds to the number of series-connected LEDs multiplied by the forward voltage UF at the set output current IF.
With the set output current IF and the output voltage, the output power Pout of the EL2596 can now be calculated:
For a different number of LEDs, the following parameters now result for the EL2596:
Number of LEDs | Forward current IF | Output voltage Uout | Output power Pout |
|---|---|---|---|
1 | 1 A | 2.35 V | 2.35 W |
4 | 1 A | 9.4 V | 9.4 W |
8 | 1 A | 18.8 V | 18.8 W |
Once the parameters for the desired circuit have been calculated, check whether the operating range of the EL2596 is complied with. The operating range is limited by three parameters:
- the maximum continuous output current, which is limited by internal components
- the maximum output voltage of the terminal, which is 28.3 V (continuous light) or 26.8 V (pulse mode) with a maximum supply voltage of 28.8 V
- the maximum output power of 14.4 W, which correlates to the internal power loss (the internal power loss can be read from the info data in CoE index 0xF900:13)
As can be seen in the illustration, the parameters for one and four LEDs lie within the permissible operating range of the EL2596. The maximum output power of the EL2596 is exceeded with eight LEDs, therefore the circuit is not permissible. The parallel connection of several EL2596 terminals for the purpose of increasing the power is not permitted due to the internal circuit in the EL2596.
The output power can be reduced by lowering the output current until the permissible operating range of the EL2596 is complied with.