Current Regulation; Power Regulation - Agilent Technologies N8900 series Operating Manual

Operating Modes

Current Regulation

Current regulation is also known as current limiting or constant current mode (CC).
In CC mode, the DC output current is held constant by the power supply when the output current reaches the current
limit setting. The power supply then switches from CV to CC mode. If, however, the power consumption reaches the
set maximum power value, the device will switch automatically to power limit (CP) where Vout X Iout = Plimit.
When the power supply is operating in constant current mode, the front panel CC status indicator is displayed. The CC
status condition can also be read by the remote interface as well as the analog interface.
In the figure above, the line representing load resistance C, the lowest load resistance shown on the graph, crosses the
operating locus at point 3. Point 3 is on the part of the operating locus defined by the current setting, so the power sup-
ply operates in CC mode.

Power Regulation

Power regulation is also known as power limiting or constant power mode (CP).
Constant-Power limit compares the output power against the built-in threshold. A OP protection occurs when the
threshold is exceeded. The OP protection is always enabled.
In CP mode, the DC output power is limited at the unit's maximum rated power. Power limiting operates according to
the auto-ranging principle such that at lower output voltages higher current flows, and at higher output voltages lower
current flows. This maintains the output power within the power rating of the unit supply.
When the power supply is at the constant power limit, the front panel CP status indicator is displayed. The CP status
condition can also be read by the remote interface as well as the analog interface.
The power supply can operate at the power limit without being damaged. However, the power supply is not guaranteed
to meet specifications when operating in power limit mode. Output ripple may increase and neither output voltage or
current is regulated.
In the figure above, the line representing load resistance B crosses the operating locus at point 2. Point 2 is on the out-
put power boundary of the unit, so the power supply operates in CP mode. Press the Meter key to display the power (W)
being supplied to the output.
The figure and tables below show the values of the power limiting characteristic.
Agilent N8900 Series Operating and Service Guide 69