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What’s the advantage of chip power NTC in application comparing with traditional pin-type power NTC?

1. The diameter of pin-type power NTC ranges from 6.5mm to 30mm. Chip NTC can provide at least 50% area reduction for PCB design.

2. The height of chip NTC is only 1/4 of that of Pin-type NTC, which will save more space and make the end product slimmer.
3. SMD components can be placed on both sides of PCB to achieve flexible layout.

4. SMD components are suitable for fully automatic processing which would reduce labor cost and achieve greater efficiency.

What’s the advantage of chip power NTC in electrical characteristics comparing with traditional pin-type power NTC?

The material resistivity of pin-type is very low (50-200m·mΩ) which results in low B constant and high residual resistance. Chip power NTC is made of innovative materials with high resistivity (5000m·mΩ or so) and adopts internal electrode structure thus provides higher B constant (4000K or more) and lower residual resistance.

How do we choose power NTC thermistor?

1. MAX. Permissible Current:Max. permissible current of NTC should be larger than the circuit operating current. Normally, please choose the NTC with the current 20% or more.

2. R25: R25≥1.414*U/Im (U: input AC voltage,Im: inrush current);

3. Permissive Capacitance:The permissive capacitance of power NTC should be larger than the capacitor connecting with NTC at the rated voltage.

4. Residual Resistance of Max. Current:The less resistance at Max. current, the less power dissipated in NTC. Please choose the NTC with the least Residual Resistance on the condition of meeting the above factors.

How dose Power NTC Work?

When turning on the switch in the AC-DC conversion circuit, such as switch-mode power supplies in LED driver board, inverter fluorescent lamps, heaters, etc, an excessive inrush current is generated and sometimes the peak current is 100 times larger than working current, which may cause damage to other components.

As NTC thermistor placed in series with AC circuit is in cold status and has relatively high resistance, when the surge current pass through, the NTC thermistor absorbs it and converts it into heat. Then the resistance of the NTC thermistor will rapidly decline with the body heating up. With its low residual resistance, which is nearly 1/20~1/60 of the nominal zero-power resistance, the consuming power of NTC thermistor can be neglected, so it does not affect the normal working current.

What types of NTC thermistor do you have? How do they differ from one another?

There are two types NTC thermistors, temperature sensor NTC and power NTC. Temperature sensor NTC can sense outside temperature changes therefore can be used for temperature measuring, temperature compensation and temperature control, applied in mobile device charger circuit, HDD, pick-up, electrical calendar with temperature, etc. Power NTC thermistor is used to suppress inrush current when the equipment switches on. Power NTC thermistor is one of the most effective and simple measures to solve inrush current problem in AC-DC power supply circuit

How to calculate B-constant of NTC?

B constant is calculated between two specified ambient temperatures by the following formula, 

                                                          

T and T0 is absolute temperature (K).

B-constant is commonly calculated between 25 and 50 or 25 and 85.