High Temperature EPCOS NTC Thermistor Resistance 6D-5 7D-5 8D-5 8R
0.7A 2700K -40 To +150Deg
Operating Principle Of The EPCOS NTC Thermistor
In order to avoid inrush current when turn on the electronic
circuit,power ntc thermistor often use in series circuit.Before
power on, ntc thermistor in high value so it can limit inrush
current,and failing to a very small degree after it.ntc
thermistor's power consumption would be negligible relative to the
circuit,ensuring the equipment to work.So ntc thermistor is the
most simple and effective measurs in limiting inrush
current,protecting electronic equipment from damage.
What is the difference between PTC and NTC thermistor?
They are available with either a negative temperature coefficient,
(NTC) of resistance or a positive temperature coefficient (PTC) of
resistance. The difference being that NTC thermistors reduce their
resistance as the temperature increases, while PTC thermistors
increase their resistance as the temperature increases.
Application Of The EPCOS NTC Thermistor
Suitable for switching power supply, switching power supply, UPS
power supply, various electric heaters, electronic energy-saving
lamps, electronic ballasts, protection of power supply circuits of
various electronic devices, and filament protection of color
display tubes, incandescent lamps and other lighting fixtures
1.Power products: switch mode power supply,UPS power
2.Lighting products: incandescent lights,energy saving lights,LED
lights.
3.Equipment products: industry equipment,communication
equipment,electrical equipment,medical equipment
4.Home appliance: air conditioner,refrigerator,TV,washing machine
5.Instrumental products.
Selection Guide Of The EPCOS NTC Thermistor
1. Max operating current of ntc thermistor Imax > actual
operating current in power circuit.
2. Rated resistance of ntc thermistor R25≥(root of 2)xE/Im
E: Line voltage Im: Max inrush current current in circuit
3. B value is bigger, residual resistance is smaller, temperature
rising is smaller when operating.
Features Of The EPCOS NTC Thermistor
1. Comply with ROHS complaint
2. Small size,big power,strong inrush current limiting ability
3. Fast response
4. Big B value,low residual resistance
5. Long life and high reliability
6. Completed series,wide operating range
7. Low cost and good stability
Main Parameters Of The EPCOS NTC Thermistor
| P/N | D | T | d | F | L |
| Tin-plated copper wire | Tin-plated steel wire | Normal | Cutting |
| MF72 8D-5 | ≤7 | ≤4.5 | 0.55±0.06 | 0.5±0.06 | 5.0±1.0 | ≥25 | Customization |
| P/N | Rated zero power resistance @25C(Ohm) | Max stable current @25C(A) | Residual resistance at max current @25C(A) | B25/85(K) | Thermal time constant(s) | Dissipation factor(mw/C) | Certification | Operating temperature |
| MF72 8D-5 | 5 | 0.7 | 0.675 | 2700 | ≤18 | ≥6 | -40~150 | UL |
Series Parameters Of The EPCOS NTC Thermistor
| P/N | Rated zero power resistance @25C(Ohm) | Max stable current @25C(A) | Residual resistance at max current @25C(A) | B25/85(K) | Thermal time constant(s) | Dissipation factor(mw/C) | Certification | Operating temperature |
| 5D-5 | 5 | 1 | 0.584 | 2700 | ≤18 | ≥6 | -40~150 | CQC UL CUL TUV |
| 6D-5 | 6 | 0.7 | 0.675 | 2700 | ≥6 | -40~150 | TUV |
| 7D-5 | 7 | 0.7 | 0.766 | 2700 | ≥6 | -40~150 | TUV |
| 8D-5 | 5 | 0.7 | 0.857 | 2700 | ≥6 | -40~150 | TUV |
| 10D-5 | 10 | 0.7 | 1.039 | 2700 | ≥6 | -40~150 | CQC UL CUL TUV |
| 12D-5 | 12 | 0.6 | 1.235 | 2800 | ≥6 | -40~150 | TUV |
| 15D-5 | 15 | 0.6 | 1.530 | 2800 | ≥6 | -40~150 | CQC UL CUL TUV |
| 16D-5 | 16 | 0.6 | 1.628 | 2800 | ≥6 | -40~150 | TUV |
| 18D-5 | 18 | 0.6 | 1.824 | 2800 | ≥6 | -40~150 | TUV |
| 20D-5 | 20 | 0.6 | 2.020 | 2800 | ≥6 | -40~150 | CQC UL CUL TUV |
| 22D-5 | 22 | 0.6 | 2.060 | 2800 | ≥6 | -40~150 | CQC UL CUL TUV |
| 25D-5 | 25 | 0.5 | 2.123 | 2800 | ≥6 | -40~150 | TUV |
| 30D-5 | 30 | 0.5 | 2.227 | 2800 | ≥6 | -40~150 | CQC UL CUL TUV |
| 33D-5 | 33 | 0.5 | 2.436 | 2800 | ≥6 | -40~150 | CQC UL CUL TUV |
| 50D-5 | 50 | 0.4 | 2.653 | 3000 | ≥6 | -40~150 | CQC UL CUL TUV |
| 60D-5 | 60 | 0.3 | 2.753 | 3000 | ≥6 | -40~150 | CQC UL CUL TUV |
| 200D-5 | 200 | 0.1 | 18.7 | 3000 | ≥6 | -40~150 | UL |
Application Example Of The EPCOS NTC Thermistor
Black Shark Star Stream 30W Gallium Nitride Charger
Why can't products using NTC thermistors switch frequently? The
following is their brief analysis and improvement.
a.Briefly analyze
We can see from the analysis of the working principle of the
circuit that there are products that use NTC thermistors. Under
normal working conditions, a certain current flows through the NTC
thermistor, and this working current is enough to make the surface
temperature of the NTC reach 100 ℃～200℃. When the product is turned
off, the NTC thermistor must fully recover from the high
temperature and low resistance state to the normal temperature and
high resistance state in order to achieve the same surge
suppression effect as the last time. This recovery time is related
to the dissipation coefficient and heat capacity of the NTC
thermistor, and the cooling time constant is generally used as a
reference in engineering. The so-called cooling time constant
refers to the time (in seconds) required for the NTC thermistor to
cool down to 63.2% of its temperature rise after self-heating in a
specified medium. The cooling time constant is not the time
required for the NTC thermistor to return to normal, but the larger
the cooling time constant, the longer the required recovery time,
and vice versa.
b.how to improve
Under the guidance of the above ideas, at the moment when the
product is powered on, the NTC thermistor suppresses the inrush
current to an appropriate level, and then the product is powered on
and works normally. Resistors are cut from the working circuit. In
this way, the NTC thermistor only works when the product is
started, and is not connected to the circuit when the product is
working normally. This not only prolongs the service life of the
NTC thermistor, but also ensures that it has sufficient cooling
time, which can be suitable for applications requiring frequent
switching.
It can be seen from the above analysis that for applications that
require frequent switching, a relay bypass circuit must be added to
the circuit to ensure that the NTC thermistor can be completely
cooled and returned to the resistance in the initial state. In
product selection, the product series should be selected according
to the maximum rated voltage and filter capacitance value, and the
resistance value of the NTC thermistor should be selected according
to the maximum starting current value allowed by the product and
the working current loaded on the NTC thermistor for a long time.
At the same time, the temperature of the working environment should
be considered, and the derating design should be appropriately
carried out.
c. in conclusion
It can be seen from the above analysis that the NTC thermistor type
surge suppressor used in the power supply design has the same
ability to suppress the surge current as the ordinary resistor, and
the power consumption on the resistor can be reduced by tens to
hundreds of times. For applications that require frequent
switching, a relay bypass circuit must be added to the circuit to
ensure that the NTC thermistor can completely cool down and return
to its initial state of resistance. In product selection, the
product series should be selected according to the maximum rated
voltage and filter capacitance value, and the resistance value of
the NTC thermistor should be selected according to the maximum
starting current value allowed by the product and the working
current loaded on the NTC thermistor for a long time. At the same
time, the temperature of the working environment should be
considered, and the derating design should be appropriately carried
out.
