Agilent Technologies E3633A, E3634A manual Load Consideration

Chapter 7 Tutorial

Connecting the Load

Load Consideration

Capacitive Loading

In most cases, the power supply will be stable for almost any size load capacitance. Large load capacitors may cause ringing in the power supply’s transient response. It is possible that certain combinations of load capacitance, equivalent series resistance, and load lead inductance will result in instability. If this occurs, the problem may often be solved by either increasing or decreasing the total load capacitance.

A large load capacitor may cause the power supply to cross into CC or unregulated mode momentarily when the output voltage is reprogrammed. The slew rate of the output voltage will be limited to the current setting divided by the total load capacitance (internal and external).

Table 7-2. Slew Rate

Internal	Internal Bleed	Slew Rate at No Load and
Capacitance	Resistor	Full Scale Currnet Setting
470 uF x 2 ea	3 K9	0.44 V/msec

Inductive loading

Inductive loads present no loop stability problems in constant voltage mode. In constant current mode, inductive loads form a parallel resonance with the power supply’s output capacitor. Generally this will not affect the stability of the power supply, but it may cause ringing of the current in the load.

Pulse Loading

In some applications the load current varies periodically from a minimum to a maximum value. The constant current circuit limits the output current. Some peak loading exceeding the current limit can be obtained due to the output capacitor. To stay within the specifications for the output, the current limit should be set greater than the peak current expected or the supply may go into CC mode or unregulated mode for brief periods.

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