The Problem : 

Switch Mode Power Supplies (SMPS) are efficient when powering devices but often consume unnecessary power in standby or low-power mode. This is a common issue in battery-powered systems where even a small current drain can reduce battery life. High standby current can also heat up components and shorten the lifespan of the system.

The Solution : 

To fix this, reduce the standby power by optimizing the feedback network and using a low-power MOSFET to switch off non-essential circuits when the load is minimal. Adding a high-value resistor in parallel with the feedback pin of the SMPS controller can effectively limit the leakage current. A properly selected MOSFET can further reduce power consumption by switching the supply to a near-zero current state during idle periods.

Practical Example :

Consider a solar-powered weather station that collects data every 10 minutes and remains idle between intervals. Without optimizing low-power mode, the battery drains quickly. By adding a 120kΩ resistor across the feedback pin and using a low-power MOSFET like IRF540 to switch off unused sections, you can cut down standby power and extend the battery life significantly.

Sample Calculation :

If the feedback voltage of your SMPS controller is 1.25V and the desired standby current is 10µA, the required resistor value can be calculated using Ohm’s Law:

R = IV ​= 10µA1.25V​≈125kΩ

In this case, choosing a 120kΩ or 130kΩ resistor ensures optimal feedback control.

Recommended Products :

• MOSFET IRF540 – Ideal for low-power switching in SMPS circuits.

• Precision Resistors – Ensures accurate feedback voltage to minimize standby power.

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