Constant Current (CC) mode

Constant Current (CC) mode is an operating state in power supplies that maintains a steady, user-defined current output regardless of changes in load resistance. It automatically lowers output voltage to prevent excessive current if the load resistance drops below a threshold. Common applications include LED driving, battery charging, and, electroplating/scientific experiments.

Key Aspects of CC Mode

• Automatic Trigger: The power supply enters CC mode when the load attempts to draw more current than the set limit, transitioning automatically from Constant Voltage (CV) mode.
• Voltage Limitation: While the current remains constant, the voltage becomes adaptive, adjusting based on Ohm’s Law (V = I x R) to maintain the set current.
• Protection: CC mode acts as a safeguard, protecting sensitive devices (e.g., LEDs) from burnout caused by overcurrent.
• Indicators: Most power supplies will have an LED indicator or a "CC" display icon, and the voltage reading will typically drop, indicating the power supply is in CC mode.

Example:
If a power supply is set to 2A and 10V (CV mode), but the load resistance drops, causing the load to demand 3A, the power supply will enter CC mode, restricting the output to 2A and decreasing the voltage to keep the current steady.

Core Mechanism

• Variable Voltage: To keep the current steady, the power supply automatically adjusts (increases or decreases) its output voltage based on Ohm’s Law (V = I x R).
• Automatic Crossover: Most modern benchtop units like those from B&K Precision start in Constant Voltage (CV) mode. They switch to CC mode only when the load attempts to draw more current than the user-defined current limit.

Primary Applications

• LED Driving: LEDs are current-sensitive; CC mode prevents thermal runaway and ensures uniform brightness.
• Battery Charging: Lithium-ion batteries use CC mode during the "bulk" stage to safely push energy into the cell before switching to CV mode as the battery nears full capacity.
• Component Protection: It acts as a safety "fuse," preventing delicate circuits from burning out if there is a short or sudden drop in resistance.

Key Limitations