Solution
The RMX programmable power supply can operate in constant-voltage (CV) or constant-current (CC) mode. The operation mode is determined by the following three values.
• The set output voltage (VS)
• The set output current (IS)
• The load resistance (RL)
The operation modes are described below.
The above figure shows the operation modes of an RMX programmable power supply.
The load resistance is denoted as RL.
The compliance resistance RC is calculated from the set voltage and current (RC = VS/IS).
The power supply is designed so that it operates in CV mode in area A and CC mode in area B.
The boundary between the two operation modes is the line defined by RL = RC.
This line represents the load at which the output voltage equals the set voltage and the output current equals the set current.
If load resistance RL is greater than the compliance resistance RC, the operating point falls in area A, and the RMX programmable power supply will operate in CV mode (point p).
In this case, the set current IS operates as a current limit.
When operating in CV mode, the output voltage is maintained at the programmed voltage setpoint. The output current I is determined by the equation I = VS/RL and is less than current limit IS. The actual current that flows is determined by the voltage setpoint and the load resistance and will not necessarily be equal to the programmed value.
For loads which may cause transient current spikes, current IS must be set so that the peak value does not reach the current limit.
Conversely, if load resistance RL is less than the compliance resistance RC, the operating point falls in area B, and the RMX programmable power supply operates in CC mode (point q). In this case, set voltage VS operates as a voltage limit.
When operating in CC mode, the output current is maintained at the programmed current setpoint. The output voltage V is determined by the equation V = IS × RL and is less than voltage limit VS. The actual voltage that flows is determined by the current setpoint and the load resistance and will not necessarily be equal to the programmed value.
For loads that generate transient voltage spikes, VS must be set so that the surge voltage does not reach the voltage limit.