For electronics hobbyists and engineers, one common issue faced when designing power supplies is the sudden inrush current at startup. This can damage components or cause erratic behavior in your circuit. A simple and effective solution to this is implementing a “Soft-Start” feature in your SMPS (Switched-Mode Power Supply).

The Problem :

Soft-Start is a technique used to limit the current surge when the power supply turns on. Without it, components like capacitors and inductors can draw a large current all at once, stressing the system and causing potential failure. By gradually ramping up the voltage, Soft-Start prevents this issue.

Practical Example : 

Imagine you’re building a microcontroller-based circuit that controls a motor. Without Soft-Start, when the power is switched on, the motor’s sudden surge of current could damage the microcontroller or disrupt its operation. By incorporating a Soft-Start circuit, the motor voltage gradually rises, ensuring a safe startup.

Sample Calculation :

If your SMPS input is 12V and the resistor (R1) is 100Ω, the charging time of the capacitor can be calculated using the formula for an RC circuit:

$T=R\times C$
        If C = 100µF, then
        T=100Ω×100μF=0.01s

This indicates a soft ramp-up time of 10ms, enough to prevent a current spike.

Product Suggestions :

For your SMPS project, consider using high-quality MOSFETs and capacitors that are Made in India. You can find reliable and affordable options at SmartXProKits.

Shop Now :

Shop now at SmartXProKits.in and support India’s innovation—buy from our Make in India site!