Question

What is a current limiting feature in SMPS?

Answer 1

A current limiting feature in a Switch Mode Power Supply (SMPS) is designed to protect the power supply and connected components from overcurrent conditions. This feature ensures that the output current does not exceed a predetermined level, which can prevent damage to the SMPS and the load it powers.

Current limiting can be implemented in several ways:

1. **Foldback Current Limiting**: This method reduces the output voltage as the load current increases beyond a certain point, effectively limiting the current while maintaining some output voltage.

2. **Constant Current Mode**: In this mode, the power supply actively regulates the output current to stay within specified limits, often used in applications like battery charging.

3. **Shunt Resistor**: A resistor is placed in series with the output to sense the current. If the current exceeds the set threshold, feedback circuits will reduce the output voltage or shut down the output.

4. **Internal Current Sensing**: Many modern SMPS controllers have built-in mechanisms to monitor the current and react accordingly to prevent excessive current draw.

Overall, current limiting helps maintain reliability and safety in electronic systems by preventing overheating, component damage, and potential failures.

Answer 2

A current limiting feature in a Switched-Mode Power Supply (SMPS) is designed to protect the power supply and connected loads from excessive current draw. This feature prevents damage due to short circuits, overloads, or faults.

When the output current exceeds a predetermined threshold, the current limiting mechanism activates, reducing the output voltage or switching frequency to maintain current at a safe level. There are generally two types of current limiting methods:

1. **Constant Current Limiting**: The SMPS regulates output current to a fixed limit, maintaining it regardless of changes in load or input voltage.

2. **Foldback Current Limiting**: In this method, as the output current exceeds the limit, the output voltage is reduced, causing the current to drop further. This helps in preventing overheating and allows the power supply to recover once the fault is cleared.

Implementing current limiting enhances the reliability and safety of the power supply system.