What is the difference between voltage mode and current mode?

Voltage mode and current mode are the two regulating conditions that control the output of the supply. Most applications call for a supply to be used as a voltage source. A voltage source provides a constant output voltage as current is drawn from 0 to full rated current of the supply. In these applications, the power supply runs in voltage mode, maintaining a constant output voltage while providing the required current to the load. A voltage source is generally modeled as providing a low output impedance of the supply.

Current mode works in a similar fashion, except it limits and regulates the output current of the supply to the desired level. When the supply runs in current mode, the supply provides a constant current into a variety of load voltage conditions including a short circuit. A current source is generally modeled as providing a very high output impedance of the supply.

These two regulating modes work together to provide continuous control of the supply, but with only one mode regulating at a time. These are fast acting electronic regulating circuits, so automatic crossover between voltage mode to current mode is inherent in the design. With the programming of the voltage mode and current mode set points available to the customer, the maximum output voltage and current of the supply can be controlled under all operating conditions.