45
range. Regardless of the number of LED in series, the operating point resistance Rd is
equal to Coeff (Coeff<1) multiplied by the value of Vo/Io.
Therefore, the user can get Io from the rated output current of LED driver and calculate
the RdCoeff parameter according to I-V curve on LED specification. It is allowed for users
to perform any real LED simulation loading on the LED driver by arbitrarily adjusting within
the output voltage range of LED driver.
Example:
LED Driver has a output current Io of 350mA and output voltage range of 20~50V
A LED light bar has 10 piece LEDs in series, each single LED I-V curve showed in Figure
3.27.
The working voltage Vo of a single LED at 350mA is 3.44V, the sum working voltage is
34.4V when 10 piece LED in series.
Purpose: test LED driver specification
Operation steps:
1.
Press the key
to enter the mode selection page, press the up and down keys to
select LED, and press the key
to enter the LED test interface, as shown in
Figure 3.26.
2.
In Figure 3.26, press the key
to enter the setting interface, as shown in Figure
3.25, set Vo=34.4V,Io=0.35A,Rf=0.173 . Then Rf is calculated as follows:
3.
According to the V-I curve in Figure 3.27, the tangent line slope of the working point is
the operating point resistance Rd,
Figure 3.27 LED lamp V-I curve
ET System electronic GmbH