Tektronix Keithley 2268 Series, Справочное руководство

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Local Operation Series 2268 850 Watt DC Power Supplies Reference Manual
38 2268S-901-01 Rev. A / January 2015
Constant Current (CC) Mode Operation
If the output is enabled, the voltage and current start to rise. At this time the unit is operating
in CV mode (default operational mode). As the load current drawn reaches the value of the
output current setting, the unit will switch to CC mode and not allow any additional current to
be drawn above the value of I
SET
. The unit is now operating in CC mode. The voltage will
still vary to meet any changes in required output voltage resulting from a change in the
attached load.
Constant Power (CP) Mode Operation
If the output is enabled, the voltage and current start to rise. The unit will continue to increase
the current until one of the following occurs:
•
The programmable power set point has been reached.
•
The voltage set point has been reached, in which case the unit will regulate the voltage
in order to maintain the voltage set point.
•
The current set point has been reached, in which case the unit will regulate the current in
order to maintain the current set point.
Figure 11: Voltage:Current:Constant Power Set Point
Automatic Mode Crossover
Mode crossover occurs when the unit makes the switch between operating modes. Crossover
can occur from CV to CC or vice versa, depending on how the attached load resistance
changes. Figure 12 shows the relationships between the variables.
For example, if the unit was initially operating in CV mode with the output voltage at the
voltage set point and the load current below the I
SET
and the attached load resistance began to
decrease, the current would rise to meet this change in the load. The load current will
increase in proportion to the decrease in the load resistance until the load current drawn
reaches the current set point. At this point further decreases in load resistance (increased load
current requirements) will cause the unit to cross over into CC mode where the output
voltage will vary with changing load resistance and the load current will remain at the I
SET
value.