How does the DC power supply control the CC/CV mode?
Most laboratories use a DC power supply as a constant voltage or constant current power supply. Remember that a power supply is a feedback system that can be used to adjust certain parameters. The power control loop can regulate the voltage under constant voltage conditions. Under constant current conditions, the power feedback control loop can regulate the current.
So if you are using a CV/CC power supply, it means that the power supply will operate in CV mode and adjust the constant voltage according to the programmable voltage setting until the load draws enough current to reach the current setting, this programmable current setting usually called current limit. Once the supplied current reaches the current setting, the power supply switches from CV mode to CC mode. In CC mode, the power supply adjusts the constant current according to the programmable current value, and since it is no longer the parameter to be adjusted, the voltage starts to drop. Conversely, if the power supply is regulating constant current in CC mode, it will continue to operate that way until the voltage across the load reaches the set point. The power supply then switches the mode from CC mode to CV mode. In CV mode, the power supply resumes regulation as described above.
The following questions are more common and are explained as follows:
1. Where is the CV or CC switch on the power supply?
The answer is: such a thing does not exist. Because the power mode is determined by the load resistance. When the resistance is high or the circuit is open, the current flowing through the power supply is very low, or there is no current flowing through the power supply, and the power supply is in CV mode. Likewise, if the resistance or short circuit is small, a lot of current will flow through the power supply, and the power supply will be in CC mode (Figure 1).
Figure 1: The output characteristic curve of the DC power supply shows the load resistance value (RLOAD) of the inverter in CV or CC mode
2. What is priority mode?
We introduce the following concept: priority mode. In addition to the CV and CC modes, the power supply can also have a voltage priority mode and a current priority mode. The priority mode controls the properties of the power supply. In voltage priority mode, the supply voltage control loop takes priority. Most of the power supplies available on the market today only have a voltage priority function and cannot provide a current priority mode. In fact, this situation is very common. Most engineers don't even realize there are other priority modes. They just want their CV/DC power supply to have a voltage priority mode.
