The NTC sensor element is the basis for the realization of the functions of NTC temperature sensors in various applications and is very common in other types of electronic products, such as resettable fuses and automatically adjustable heaters. As a type of semiconductor sensing element, the applications of NTC can be roughly divided into two categories: temperature measurement and circuit protection.
Due to its high sensitivity and high precision, the NTC thermistor has been well used for temperature measurement that values durability, reliability, and stability. Although there are many materials for thermistors, compared with conductors such as metals, NTC, a type of semiconductor resistor, is easier to process, smaller, and lighter. Moreover, due to its fast response speed, it is also suitable for small-diameter precision equipment.
In low-cost temperature measurement solutions, generally, a pull-up resistor is connected in series between the NTC thermistor and the positive pole of the power supply, and the change in the ambient temperature is determined by collecting the voltage division change across the NTC thermistor. In most cases, a resistor with the same resistance value as the NTC at room temperature is connected in series, and the current flowing through it must be small enough to avoid self-heating to ensure the accuracy of the measurement process.
To avoid self-heating to ensure the accuracy of the measurement process. On the other hand, since the NTC thermistor is essentially a non-linear resistor, linear processing must be done before temperature measurement and measurement must be ensured within the appropriate temperature range; otherwise, the result will be quite different. Currently, it can generally cover the measurement range from -50°C to 150°C, and some industry-leading NTC manufacturers can cover from -55°C to 175°C. If it has a special coating, it is no problem for the NTC thermistor to cover up to 300°C.
The resistance-temperature coefficient of the NTC thermistor is reduced by 3 to 5% per 1°C. Compared with other metal resistors, whose resistance value changes only a few percentage points per 1°C, it can be seen that the NTC thermistor shows a large resistance change even with a small temperature change. From these characteristics, it is not difficult to see that within the appropriate temperature range, the NTC thermistor can detect small temperature differences sensitively and with high precision.
The chip-type embeddable NTC thermistor can be directly integrated into IGBT modules and IPM modules. For example, the new chip-type L860 NTC thermistor from TDK can be directly embedded into the power module through sintering and heavy aluminum wire welding connections without leads, which is completely different from traditional SMD NTC components. We all know that the efficiency of the power module is usually the highest when operating close to its power limit, but to maintain the limit state operation, the temperature must be precisely controlled. Compared with traditional NTC components, the thermal coupling between the chip-type NTC thermistor and the power module is more stable, which means that the component can achieve ultra-fast response and is more conducive to high-precision temperature measurement and control.
Whether in industrial, automotive or consumer-grade applications, monitoring the temperature of all power components is a key task and a basic requirement for ensuring the safety, reliability and service life of the entire system, and the NTC thermistor is widely used in it.
In terms of circuit protection and control, the application of NTC is also quite a lot. Generally, when starting up, there will be a large current flowing through the diode, and if the current is too large, the diode may be damaged. There are many methods to suppress the inrush current. In general, the method of current limiting by resistors is adopted in small and medium power supplies to suppress the inrush current at startup.
The traditional fixed resistance value current-limiting resistor has the problem that the power consumption on the resistor cannot be changed. While an NTC thermistor is connected in series on the line. Before starting up, due to the low temperature of the thermistor, the resistance is relatively large, which can well limit the inrush current at startup. After starting up, the temperature of the thermistor rises, and the resistance value drops significantly, and excessive losses will not be generated.
This process occurs very rapidly in practical applications. The NTC thermistor rapidly heats up with the increase in temperature, and its resistance value rapidly drops to a very small level within milliseconds, generally only a few tenths of an ohm to a few ohms. In contrast, the power loss on the resistor is reduced by tens or even hundreds of times.
The suppression method based on the NTC thermistor has the advantages of high power, strong ability to suppress inrush current, high reliability, long life, and small residual resistance. Generally, for small-power supplies, relays are not needed for NTC, while for large-power supplies, relays are needed. However, it should be noted that for power equipment that uses NTC to suppress startup inrush, frequent startup and shutdown are not allowed. The NTC needs tens of seconds to several minutes to cool down and return to its cold-state resistance value before it can be started up again.
As the NTC for suppressing startup inrush to ensure that electronic equipment is not damaged, it can be said to be the simplest and most effective. Of course, the NTC only plays a role in startup protection. When the circuit is working normally or short-circuited, the NTC is unable to deal with the inrush.
The NTC thermistor, as a typical type of temperature-sensitive semiconductor resistor, its resistance value decreases as the temperature rises. Having the characteristic of changing the resistance value with the temperature change is one aspect. The NTC thermistor element also has the advantages of low loss and almost no hysteresis phenomenon, and it can also play a very good protective role.
UF capacitors produce both black and green type of NTC to replace NTC from TKD/EPCOS, thinkig-TVR. Folloiwng cross reference FYI. If you have such demand, kindly send to RFQ to connie@topdiode.com. thank you
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UF Capacitors |
TDK/EPCOS |
Thinking-TVR |
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MF72 Power NTC Thermistor |
B57 Series |
SCK*** Series |
