B&K Precision 1762 - Manual - Manual (Page 21)

21
OPERATING INSTRUCTIONS
Figure 7. Constant Voltage/Constant Current
Characteristics.
Constant Voltage/Constant Current Characteristic
The working characteristic of this power supply is called a constant
voltage/constant current automatic crossover type. This permits continu-
ous transition from constant current to constant voltage modes in re-
sponse to the load change. The intersection of constant voltage and
constant current modes is called the crossover point. Fig. 7 shows the
relationship between this crossover point and the load.
For example, if the load is such that the power supply is operating in
the constant voltage mode, a regulated output voltage is provided. The
output voltage remains constant as the load increases, up until the point
where the preset current limit is reached. At that point, the output
current becomes constant and the output voltage drops in proportion to
further increases in load. The crossover point is indicated by the front
panel LED indicators. The crossover point is reached when the CV
indicator goes off and the CC indicator comes on.
Similarly, crossover from the constant current to the constant voltage
mode automatically occurs from a decrease in load. A good example of
this would be seen when charging a 12-volt battery. Initially, the open
circuit voltage of the power supply may be preset for 13.8 volts. A low
battery will place a heavy load on the supply and it will operate in the
constant current mode, which may be adjusted for a 1 amp charging
rate. As the battery becomes charged, and its voltage approaches 13.8
volts, its load decreases to the point where it no longer demands the full
l amp charging rate. This is the crossover point where the power supply
goes into the constant voltage mode.