PTC Thermistor for Lighting Time Delay and Switching Starting Application

Lighting Switching PTC Thermistor Description

Lighting Switching PTC Thermistor are used when a load in series with the PTC thermistor has to be switched off after a time delay and when switching occurs frequently.
A typical application of switching PTC thermistor is the preheating of electrode in energy-saving lamps or fluorescent lamps. Switching PTC can also be used as a power resistor for loading a capacitor, for example in power supplies or in control units of production equipment.

Lighting Switching PTC thermistor Application

It's applicable to various types of fluorescent lamp, electronic ballast and electronic energy-saving lamp. The PTC can be connected across the lamp resonator without changing the circuits. It can change hard start of the ballast and electronic energy-saving lamp to preheated start and the preheating time of the filament can come up to 0.4-2 seconds, which will extend the service life of the fluorescent tube by over 4 times.

Switching PTC thermistor Operating Principle

The application of the PTC thermistor to achieve preheated start is as follows: Immediately after power is switched on, Rt is in normal temperature state and its resistance is far lower than the C2 resistance. The current through C1 and Rt forms a return circuit to preheat the filament. After about 0.4-2 seconds, Rt joule heat temperature exceeds Curie point Tsc and skips into high resistance state of far higher than C2 resistance. The current passes through C1 and C2 to form a return circuit, which causes L resonance and produces high voltage to light the fluorescent tube.

Lighting Switching PTC Thermistor Dimensional Drawings

AMWEI PTC Thermistor for Lighting Time Delay and Switching Starting Application Data Sheet

Reference information of PTC thermistor for lighting time delay and switching preheated starting applications

1. The switching time Ts can be approximated as follows:

Ts=C_th .V.(T_Ref-T_A)/P
T_Ref Reference temperature of PTC thermistor
T_A Ambient temperature
C_th Heat capacity of PTC thermistor
V PTC thermistor volume
P Switch-on power of PTC thermistor

This shows that the switching time can be influenced by the size of the PTC thermistor, its reference temperature and the power supplied. Switching time are lengthened by increasing the volume or the reference temperature, high power consumption by the PTC thermistor, on the other hand, results in short switching time.

2. Single capacitor starting circuit has higher demand on PTC thermistor voltage withstanding capacity, general required withstanding voltage >800V.

3. PTC thermistor reliability can be increased through higher resistivity, higher resistivity PTC thermistor shall be chosen first at the premises of satisfying starting characteristics.

Reference Information for Lighting Watts Corresponding to AMWEI PTC thermistor parts

1. Below 15W light , AMZ31-03 series.
2. 15-28W light, AMZ31-05 series.
3. 28-56W light, AMZ31-07 series.
4. Around 60W light, AMZ31-08 series.

Within 1 serie, the lower the light watt, the higher the resistance at 25 centigrade (R25). The higher the R25, the higher the voltage withstanding capacity.