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ET1301/1302/1303/1304 Programmable DC Electronic Load User Manual
2.9 LED Test
The LED equivalent circuit is the series connection of the LED equivalent resistance Rd and the
forward voltage Vf. Users need to set three parameters, among which Io is the output current of LED
source; Vo is the sum of the voltage drop of forward voltage Vf and LED resistance Rd when LED is in
the on-state; Coeff is the ratio of the LED equivalent resistance Rd and the total equivalent resistance of
LED load.
Operating instructions: 1.Select the action item by rotating the knob; 2. For parameter setting, please
refer to 1.4 Numeric Parameters Setting for details. 3. Press [On/Off] to turn on or off the mode.
Option Description:
Name
content
LED Vo：
0---Vmax
LED Io：
0---Imax
LED Coeff：
0.01—1
According to the following equations (1) and (2), the LED forward voltage and LED impedance can
be obtained based on the above parameters. Vf is defined as forward voltage of the diode and Rd as LED
equivalent resistance.
Rd = (Vo / Io) * Coeff
Vf = Vo * (1 - Coeff)
Hangzhou Zhongchuang Electronics Co., Ltd.
Description
Steady working voltage of LED constant current source
with LED lamp
Output current of LED constant current source
Ratio of LED equivalent resistance Rd and total
equivalent resistance of LED load
(1)
(2)
Figure 2.9 LED test interface
13
.
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