The Problem :

Switch Mode Power Supplies (SMPS) often operate in burst mode to improve efficiency at low loads. However, burst mode can cause unwanted noise and instability if not managed properly. This occurs when the controller reduces the switching frequency to conserve energy, but excessive bursts can create ripple and EMI issues.

The Solution :

To minimize these problems, ensure that the feedback loop is properly compensated. Use a low ESR capacitor and carefully select the resistor divider network. Adding a small load resistor can also help stabilize the output during low-power conditions, preventing frequent bursts.

Practical Example :

Consider a 12V, 1A SMPS powering a small IoT device. At very low loads (below 50mA), the power supply enters burst mode, causing voltage ripple. To fix this, add a 1kΩ load resistor across the output to maintain a minimum load. This keeps the SMPS out of burst mode, ensuring smooth operation.

Sample Calculation :

To calculate the load resistor:

• Desired minimum load current: 12mA

• Resistor value: R=IV​=0.012A12V​≈1kΩ

Recommended Products :

• Low ESR Capacitors: Ensure stable feedback with quality capacitors. [Shop now].

• Load Resistors: Choose high-precision resistors to manage load conditions. [Shop now].

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