AMETEK SLM Series RevC - Manual (Page 54)

Applications Sorensen SLM-Series DC Load
4-6 M540071-01 Rev C
4.5
Constant Resistance (CR) Mode Application
Major application: voltage source testing, current source testing, power supply power-up sequence
CR mode can be used in conjunction with CC mode when testing switching power supplies, to avoid
shutdown.
For example, if CC mode alone were used in test set up, a 5V/50A output power supply cannot deliver
50A over its start-up range of 0-5 volts. In many cases, the power supply short circuit or over current
protection circuit will shut the power supply down because it can’t deliver enough current at low voltage.
This is due to the power supply trying to deliver 50A at 2V because the load is in CC mode.
Therefore, when testing a power supply, the CR mode can be used to allow the power supply voltage
and current to ramp up together. After ramp-up the CC mode should be used to complete testing.
The need for manually switching from the CR to the CC mode is eliminated with SLM-series DC
electronic loads. They can be programmed with proper current and slew rate in the CC mode, which
allows a power supply to reach its specified output condition in the CC load mode.
Note: Vsense input should be connected when running in CR mode to avoid resistance variation due
to the cable resistance.
CURRENT
SOURCE
+
-
ELECTRONIC LOLAD
CR MODE
ELECTRONIC LOLAD
CR MODE
VOLTAGE
SOURCE
V
I
INPUT
VOLTAGE
LOAD CURRENT
LOAD RESISTANCE
SETTING
- +
DC
OUTPUT
Figure 4-6 Constant Resistance Mode Application