Introduction
Power supplies (PSUs) are designed with built-in protection mechanisms to ensure safe and reliable operation. When the load current exceeds the rated capacity, the overload or overcurrent protection circuit is activated to prevent damage to both the power supply and the connected equipment.
Different PSUs use different protection strategies depending on the application. Understanding these protection modes helps engineers and users select the most suitable power supply for their system.
Common Types of Overload / Overcurrent Protection
1. Foldback Current Limiting
In foldback current limiting, the output current reduces to a lower level (typically around 20% of the rated current) when an overload occurs.
- Helps minimize power dissipation under fault conditions
- Protects sensitive components from excessive heat
- Common in linear and low-power applications
2. Constant Current Limiting
With constant current limiting, the output current is maintained at a fixed level, while the output voltage decreases as the load increases.
- Ensures stable current delivery
- Common in LED drivers and battery charging applications
- Prevents excessive current flow without shutting down the system
3. Over Power Limiting
In this mode, the power supply maintains a constant output power.
- As load increases → voltage decreases proportionally
- Useful for applications requiring controlled power output
- Balances voltage and current to stay within safe limits
4. Hiccup Mode Protection
In hiccup mode, the power supply repeatedly turns ON and OFF when an overload or short circuit is detected.
- Reduces stress on components during fault conditions
- Automatically recovers once the fault is removed
- Common in switching power supplies
5. Shut-Off Protection
In shut-off mode, the power supply completely stops output voltage and current when the protection threshold is reached.
- Provides maximum safety for critical systems
- Prevents any further damage under severe fault conditions
- Requires manual or automatic restart depending on design
Combination Protection Modes
Some power supplies combine multiple protection methods, such as:
- Constant current limiting + shut-off
- Hiccup mode + auto recovery
These hybrid approaches provide enhanced flexibility and safety for different applications.
Recovery Methods
After a fault condition is cleared, the power supply can recover in two ways:
1. Auto Recovery
- The PSU automatically resumes normal operation once the fault is removed
2. Manual Restart (Re-power On)
- The PSU requires the AC input to be turned OFF and ON again
Important Note
Avoid operating a power supply under overcurrent or short-circuit conditions for extended periods, as this may:
- Shorten the lifespan of the PSU
- Cause permanent damage to internal components
Conclusion
Understanding different overload and overcurrent protection mechanisms is essential for selecting the right power supply and ensuring system reliability. Each protection type offers unique advantages depending on the application, from continuous operation to maximum safety shutdown.
If you have any technical issues, feel free to contact our team at contact@powersupplymall.com. We provide professional technical support and a wide range of solutions.