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PS280 & PS283 User Manual
9
Reference
This section tells how to set the PS280 or PS283 current limit. It also
explains the constant voltage/constant current crossover characteris-
tic of the instrument. Finally, the section includes procedures for
using the instrument in both independent and tracking modes and
provides examples of a variety of applications.
Constant Voltage/Constant Current Crossover
The PS280 or PS283 DC Power Supply features a constant
voltage/constant current automatic crossover. This feature permits
continuous operation in the transition from constant-voltage mode to
constant-current mode as the load changes. The intersection of the
constant-current and constant-voltage modes is called the crossover
point. Figure 3 on page 10 shows the relationship between the load
and the crossover point.
For example, if the load is such that the power supply is operating in
constant-voltage mode, the PS280 or PS283 provides a regulated
output voltage. The output voltage remains constant as the load
increases until the preset current limit is reached. Then the crossover
occurs. At that point, the output current becomes constant and the
output voltage drops in proportion to further load increases.
Crossover is indicated by the front panel red C.C. and green C.V.
indicator lights. If the C.V. indicator is lighted, the instrument is
operating in constant-voltage mode. If the C.C. indicator is lighted,
the instrument is operating in constant-current mode.
Crossover from the constant-current mode to the constant-voltage
mode also occurs automatically in response to a decrease in load. For
example, suppose you are charging a 12 V battery. Initially, the open
circuit voltage of the power supply is preset for 13.8 V. A low battery
places a heavy load on the power supply, and it operates in
constant-current mode. You adjust the instrument to charge the
battery at the rate of 1 A. As the battery becomes charged and its
voltage approaches 13.8 V, the load decreases to the point where the
battery no longer demands the full 1 A charging rate. The PS280 or
PS283 then crosses over to constant-voltage mode.