Application and Selection of Power Thermistors

Power thermistor (mainly negative temperature coefficient NTC type) is a key component for suppressing surge current in electronic circuits. Its main parameters, selection points and application scenarios are as follows:
je. Core functions and principles
‌Surge current suppression‌
At the moment of power startup, the NTC resistance value connected in series in the input circuit is high, which can limit the peak current; after power is turned on, the resistance drops rapidly due to heat (power consumption can be ignored), ensuring the stable operation of subsequent circuits.
‌Negative temperature characteristics‌
The resistance value decreases exponentially with increasing temperature: R.(T)=R0⋅eB⋅(1T−1T0)R.(T)=R0​⋅eB⋅(T1​−T0​1​) (R0R0​ is the resistance value at 25℃, BB is the material constant).

NTC High Power Thermistor MF72

NTC thermistor power type 10D, 5D, 8D negative temperature coefficient thermistor

How to Use NTC Thermistors for Inrush Current Limiting

How it Works:
High Initial Resistance:
When power is first applied, a power thermistor has a high resistance, which limits the initial inrush current.

Self-Heating:
As the current flows through the thermistor, it generates heat, causing its resistance to decrease.

Resistance Decrease:
The reduction in resistance allows the circuit to draw the necessary operating current without the initial surge.

Benefits:
Protects Equipment:
By limiting the inrush current, power thermostats prevent damage to sensitive components and equipment.

Reduces Power Loss:
The resistance decrease through self-heating reduces power loss compared to using a fixed resistor.

Energy Savings:
Lowering power loss can lead to energy savings in applications like switching power supplies and other electrical devices.

II. Key parameters and selection points

Note‌: Example of model identification ‌MF72-10D-9‌:
10‌: R25=10Ω.
‌D‌: Disc package
9‌: 9mm diameter;

III. Typical application scenarios
‌Power supply equipment‌: Input surge suppression of switching power supply, UPS, adapter;
‌Lighting system‌: Anti-shock protection of LED driver, ballast, lighting distribution box;
‌Industrial equipment‌: Motor start, industrial power supply, medical instrument;
‌Household appliances‌: Air conditioner, refrigerator compressor start protection;

Iv. Selection and avoidance guide

‌Current matching‌
The maximum steady-state current needs to be greater than 1.5 times the actual working current to avoid continuous heating and failure.
‌Heat dissipation design‌
In high-power scenarios, sufficient spacing or auxiliary heat dissipation is required to prevent excessive temperature rise from causing insufficient residual resistance.
‌Extreme temperature‌
The operating temperature range is generally -55℃~+125℃. Glass-sealed models (resistant to 150℃) are preferred in high-temperature environments.

V. Package and performance comparison

Tip‌: Be cautious in frequent switching scenarios – NTC may lose surge suppression capability when insufficient cooling is insufficient. A cette époque, a parallel relay bypass can be connected.