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Remote Control and Remote Voltage Sensing
a. Remote Control of the Output
The output of some DC-DC converters can be controlled by supplying an appropriate signal to the RC terminal. Normally an
open-circuit (>4 volts) will turn the output on and a short (< 0.8 volts) will turn the output off. With the SD-500 and SD-1000
units an externally applied voltage is required to turn off the output. The SD-1000 provides a 12V auxiliary output for this
purpose. You should always refer to the data sheet for all Remote ON/OFF controlled converters. See Fig 12.
b. Remote Voltage Sensing
DC-DC Converters equipped with a Remote Voltage Sense capability (SD-500 and SD-1000) can detect a voltage drop at the
load. This feature is especially useful when the unit and the load are connected by long cables. With Remote Sensing capability,
+S (or +RS) and –S (or –RS) terminals are provided (as shown in Fig. 12). When the +S and –S terminals are connected to the
load side of the output, the unit will be able to detect any voltage drop at the load. The unit will raise the output until the correct
voltage is provided at the load terminals. Remote sensing compensates for voltage drops of up to 0.5V.
Fig. 12
Operation in Parallel
Power supplies are commonly used in parallel to increase the output current. Mean Well's DDR-240 and DDR-480 series are
designed for parallel use. These power supplies have "P+" and "P–" terminals that sense other power supplies connected in
parallel. This circuit controls the output voltage and allows a more efficient operation of each supply – sharing the load current
equally.
Fig. 13
Notes on parallel operation:
a. Always use the same model type and voltage in any parallel configuration.
b. The output voltage of each unit should be the same (within 0.2V).
c. Each converter's output should be wired together with short and thick wiring first and then connected to the load.
d. The total output current should not exceed 90% of the total current for all power supplies.
e. Always check the specifications for the required connections, restrictions on the number of parallel units that can be used,
minimum load requirements and connecting the sense terminals (+S and –S) or other features (e.g. remote control).
