Excessive inrush current is a common challenge in switching power supplies. During startup, a typical 300W SMPS can experience surge currents of 50A–100A, which may damage rectifier bridges, weld relay contacts, or shorten system life.
Traditional fixed resistors dissipate power continuously and can become a reliability risk if the bypass relay fails. That’s why power NTC thermistors are widely used for inrush current limiting.
Power NTC thermistors provide a simple and effective solution thanks to their unique characteristics:
1. High Resistance at Startup
When cold, the NTC acts as a current limiter, suppressing inrush current and protecting rectifier bridges, relays, and other downstream components.
2. Low Resistance During Normal Operation
As the thermistor heats up, its resistance drops to only 3–10% of the initial value, minimizing power loss and reducing heat generation.
3. Improved Fault Tolerance
Compared with fixed resistors, NTC thermistors have higher thermal capacity and can provide valuable protection time even if the bypass control circuit malfunctions.
Recommended JYH HSU Inrush Current Limiting Solutions
MF72 5D-9 / 10D-11
Ideal for low- and medium-power switching power supplies
Compact size and cost-effective design
Suitable for 220V consumer and industrial power supplies
MF72 5D-13
Designed for medium- and high-power applications
High steady-state current capability
Excellent surge resistance for displays and industrial power supplies
Looking for the right inrush current limiter for your power supply design? Contact JYH HSU (Dongguan Zhixu Electronics) for free samples and one-on-one selection support.
Post time: Jun-22-2026