PTC Thermistors for Lighting Time Delay and Switching Starting

What Is Lighting Switching PTC Thermistor ?

PTC Thermistor for Lighting Switching

PTC Thermistor for Lighting Switching

Lighting Switching  PTC thermistor  is ceramic PTC thermistor applied for lighting switching time delay, change hard start of the ballast and electronic energy-saving lamp to preheated start, extend fluorescent tube service life.

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 thermistor 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

Typical configuration of a PTC thermistor for time delay

Typical configuration of a PTC thermistor for time delay

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.

Time Delay Circuit

Time Delay Circuit

PTC Thermistor in discharge Tube circuit

PTC Thermistor in discharge Tube circuit

Typical electronic ballast circuit with PTC Thermistor

Typical electronic ballast circuit with PTC Thermistor

Switching PTC Thermistor Operating Principle

PTC thermistors Lighting Switching Application Circuit

PTC thermistors Lighting Switching Application Circuit

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.

Typical delay of the load current

Typical delay of the load current

Typical switch-off behavior of a PTC thermistor

Typical switch-off behavior of a PTC thermistor

A typical application for switching PTC thermistor is the preheating of electrodes in energy-saving lamps or fluorescent lamps. Here the PTC thermistor is connected in series with the two electrodes of the lamp . When the rectified line is applied to the circuit the PTC thermistor is cold and low resistance. The lamp voltage is below the ignition voltage and the flowing current heats the electrodes and the PTC thermistor . After a certain period the PTC will switch, the voltage across the lamp will exceed the ignition voltage and the lamp will start to burn. Preheating of the electrodes lengthens the life of the lamp significantly. A full range of standard devices is available and custom engineered samples can be rapidly created for special lamp designs.

Switching PTC thermistor can also be used as a power resistor for loading capacitors, for example in power supplies or in control units of production equipment. Depending on the applied voltage and the capacitance of the capacitor, one or more
PTC thermistors in parallel will be necessary to load the capacitor. In contrast to fixed resistors, the PTC also offers protection against a possible shortcircuit in the capacitor.

PTC electrode heating circuit

PTC electrode heating circuit

Principle circuit diagram for the preheating of electrodes in energy-saving lamps or fluorescent lamps.

The time needed for a PTC thermistor to switch from its low resistance state to a self-heated high resistance state may be used to provide for a time delay in a circuit. If a PTC thermistor is connected in parallel with a relay, the relay will only be energized after the time necessary for the PTC to switch from low to high resistance.

When a PTC is connected in series with a relay, the relay would energize immediately and would stay energized until the PTC heats up and increases in resistance. At that point, most of the voltage would be dropped across the PTC and the relay would no longer be energized.

The time for the PTC to switch in either case would be dependent upon the resistance and size of the PTC , as well as the ambient temperature and other circuit parameters such as supply voltage and other components in the circuit.

PTC Thermistor for relay delay operation

PTC Thermistor for relay delay operation

Lighting Switching PTC Thermistors Outlook and Dimension

Lighting Switching PTC thermistors Drawing
Part Series Dmax Tmax Φd F
AMZ31-03 series 4.5mm 5.0mm 0.5mm 5.0mm
AMZ31-04 series 5.5mm 5.0mm 0.6mm 5.0mm
AMZ31-05 series 6.5mm 5.0mm 0.6mm 5.0mm
AMZ31-06 series 7.5mm 5.0mm 0.5mm 5.0mm
AMZ31-07 series 8.0mm 5.0mm 0.6mm 5.0mm
AMZ31-09 series 10.0mm 5.0mm 0.6mm 5.0mm

AMWEI PTC Thermistor for Lighting Switching Data Sheet 

 Part No.  Switching
Temperature
(C)
Resistance
at +25℃
(ohm)
R25
Max.
Voltage
(VAC)
Max.
Current
Imax
(mA)
AMZ31-03 series
AMZ31-03M151N500 80C R25: 150 ohm±30% 500V 200mA
AMZ31-03M271N650 80C R25:270 ohm ±30% 650V 200mA
AMZ31-03M391N650 75C R25: 390 ohm ±30% 650V 200mA
AMZ31-03M681N800 75C R25: 680 ohm ±30% 800V 200mA
AMZ31-03M102N800 75C R25:1000 ohm ±30% 800V 100mA
AMZ31-03M152N800 70C R25:1500 ohm ±30% 800V 100mA
AMZ31-03M222N800 70C R25: 2200 ohm ±30% 800V 100mA
AMZ31-03M332N900 70C R25: 3300 ohm ±30% 900V 100mA
AMZ31-03M472N900 70C R25: 4700 ohm ±30% 900V 100mA
AMZ31-03N151N420 105C R25:150 ohm ±30% 420V 200mA
AMZ31-03N175RN500 105C R25:175 ohm ±30% 500V 200mA
AMZ31-03N225RN500 105C R25:225 ohm ±30% 500V 200mA
AMZ31-03N271N500 105C R25:270 ohm±30% 500V 200mA
AMZ31-03N301N650 105C R25:300 ohm ±30% 650V 200mA
AMZ31-03N391N650 105C R25:390 ohm ±30% 650V 200mA
AMZ31-03N561N650 105C R25:560 ohm ±30% 650V 200mA
AMZ31-03N681N650 100C R25:680 ohm±30% 650V 200mA
AMZ31-03N102N800 100C R25:1000 ohm ±30% 800V 100mA
AMZ31-03N152N800 100C R25:1500 ohm±30% 800V 100mA
AMZ31-03P151N420 115C R25:150 ohm ±30% 420V 200mA
AMZ31-03P175RN420 115C R25:175 ohm ±30% 420V 200mA
AMZ31-03P271N500 115C R25: 270 ohm ±30% 500V 200mA
AMZ31-03P331N500 115C R25: 330 ohm ±30% 500V 200mA
AMZ31-03P391N500 115C R25: 390 ohm ±30% 500V 200mA
AMZ31-03P561N650 110C R25: 560 ohm ±30% 650V 200mA
AMZ31-03P801N650 110C R25: 800 ohm ±30% 650V 200mA
AMZ31-03P102N650 110C R25: 1000 ohm ±30% 650v 100mA
AMZ31-04 series
AMZ31-04M82RN500 80C R25: 82 ohm±30% 500V 300mA
AMZ31-04M101N500 80C R25: 100 ohm±30% 500V 300mA
AMZ31-04M151N500 80C R25: 150 ohm±30% 500V 300mA
AMZ31-04M221N500 80C R25: 220 ohm±30% 500V 300mA
AMZ31-04M391N650 75C R25: 390 ohm±30% 650V 300mA
AMZ31-04M561N800 75C R25: 560 ohm±30% 800V 200mA
AMZ31-04M681N800 75C R25: 680 ohm±30% 800V 200mA
AMZ31-04M102N800 70C R25: 1000 ohm±30% 800V 100mA
AMZ31-04M152N800 70C R25: 1500 ohm±30% 800V 100mA
AMZ31-04M222N900 70C R25: 2200 ohm±30% 900V 100mA
AMZ31-04M332N900 70C R25: 3300 ohm±30% 900V 100mA
AMZ31-04N101N420 100C R25: 100 ohm±30% 420V 300mA
AMZ31-04N151N500 100C R25: 150 ohm±30% 500V 300mA
AMZ31-04N175RN500 100C R25: 175 ohm±30% 500V 300mA
AMZ31-04N225RN500 100C R25: 225 ohm±30% 500V 300mA
AMZ31-04N301N650 100C R25: 300 ohm±30% 650V 300mA
AMZ31-04N391N650 100C R25: 390 ohm±30% 650V 300mA
AMZ31-04N601N800 100C R25: 600 ohm±30% 800V 200mA
AMZ31-04N851N800 100C R25: 850 ohm±30% 800V 100mA
AMZ31-05 series
AMZ31-05M101N500 80C R25:100 ohm±30% 500V 400mA
AMZ31-05M151N650 80C R25:150 ohm±30% 650V 400mA
AMZ31-05M271N650 80C R25: 270 ohm ±30% 650V 400mA
AMZ31-05M391N800 75C R25: 390 ohm ±30% 800V 400mA
AMZ31-05M561N800 75C R25: 560 ohm ±30% 800V 300mA
AMZ31-05M102N900 70C R25:1000 ohm ±30% 900V 100mA
AMZ31-05M152N900 70C R25:1500 ohm ±30% 900V 100mA
AMZ31-05M222N900 70C R25:2200 ohm ±30% 900V 100mA
AMZ31-05N101N500 100C R25:100 ohm ± 30% 500V 400mA
AMZ31-05N151N650 100C R25:150 ohm ± 30% 650V 400mA
AMZ31-05N221N650 100C R25:220 ohm ± 30% 650V 400mA
AMZ31-05N301N800 100C R25: 300 ohm ±30% 800V 400mA
AMZ31-05N391N800 100C R25: 390 ohm ±30% 800V 400mA
AMZ31-05N561N800 100C R25: 560 ohm ±30% 800V 300mA
AMZ31-05N681N900 100C R25: 680 ohm ±30% 900V 200mA
AMZ31-05N851N900 100C R25: 850 ohm ±30% 900V 100mA
AMZ31-05N102N900 100C R25: 1000 ohm ±30% 900V 100mA
AMZ31-05P101N500 115C R25:100 ohm ±30% 500V 400mA
AMZ31-05P151N500 115C R25:150 ohm ±30% 500V 400mA
AMZ31-05P175RN650 115C R25:175 ohm ±30% 650V 400mA
AMZ31-05P221N650 115C R25:220 ohm ±30% 650V 400mA
AMZ31-05P301N650 115C R25:300 ohm ±30% 650V 400mA
AMZ31-05P391N650 115C R25:390 ohm ±30% 650V 400mA
AMZ31-05P561N800 110C R25:560 ohm ±30% 800V 300mA
AMZ31-05P681N800 110C R25:680 ohm ±30% 800V 200mA
AMZ31-05P102N800 110C R25:1000 ohm ±30% 800V 100mA
AMZ31-06 Series
AMZ31-06M101H650 80C R25: 100 ohm ±25% 650V 600mA
AMZ31-06M121H650 80C R25: 120 ohm ±25% 650V 600mA
AMZ31-06M151H800 80C R25: 150 ohm ±25% 800V 600mA
AMZ31-06M201H900 80C R25: 200 ohm ±25% 900V 600mA
AMZ31-07 Series
AMZ31-07M70RN650 75C R25: 70 ohm ±30% 650V 600mA
AMZ31-07M101N650 75C R25: 100 ohm±30% 650V 600mA
AMZ31-07M151N650 75C R25:150 ohm ±30% 650V 600mA
AMZ31-07M221N800 75C R25: 220 ohm ±30% 800V 600mA
AMZ31-07M271N800 75C R25: 270 ohm±30% 800V 600mA
AMZ31-07M391N800 75C R25: 390 ohm ±30% 800V 400mA
AMZ31-07M561N900 75C R25: 560 ohm±30% 900V 300mA
AMZ31-07M681N900 75C R25: 680 ohm±30% 900V 200mA
AMZ31-07M102N900 75C R25: 1000 ohm±30% 900V 100mA
AMZ31-07N70RN650 100C R25: 70 ohm ±30% 650V 600mA
AMZ31-07N101N600 100C R25:100 ohm ±30% 600V 600mA
AMZ31-07N151N650 100C R25:150 ohm ±30% 650V 600mA
AMZ31-07N221N800 100C R25:220 ohm ±30% 800V 600mA
AMZ31-07N271N800 100C R25: 270 ohm ±30% 800V 600mA
AMZ31-07N331N800 100C R25: 330 ohm ±30% 800V 400mA
AMZ31-07N391N800 100C R25: 390 ohm ±30% 800V 400mA
AMZ31-07N561N900 100C R25: 560 ohm ±30% 900V 300mA
AMZ31-09 series
AMZ31-09M75RH900 80C R25: 75 ohm ±25% 900V 1000mA
AMZ31-09M101H900 80C R25: 100 ohm ±25% 900V 1000mA
AMZ31-09M151H1000 80C R25: 150 ohm ±25% 1000V 1000mA
AMZ31-09M201H1000 80C R25: 200 ohm ±25% 1000V 1000mA

Reference Information for Selecting PTC Thermistor for Lighting Time Delay and Switching Preheated Starting Applications

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

Ts=Cth .V.(TRef-TA)/P
TRef Reference temperature of PTC thermistor
TAmbient temperature
Cth 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

  • Below 15W light , AMZ31-03, 04 series.
  • 15-28W light, AMZ31-05, O6 series.
  • 28-56W light, AMZ31-07 series.
  • Around 60W light, AMZ31-09 series.

In the same dimension and the switching temperature, the lower the light watt, the higher the resistance at 25 centigrade (R25). The higher the R25, the higher the voltage withstanding capacity.

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Thermistors Application