Function of power lithium battery protection board NTC?

2021-08-31 14:32:40 0

NTC thermistor is a sensitive component that decreases in resistance as the temperature rises. 

It is used for: temperature measurement, temperature control, temperature compensation, etc. It can also be used for liquid level sensing.

NTC is a negative temperature coefficient thermistor, the main applications are as follows 

1. Used as a temperature sensor to measure temperature.

2. Used as soft start in some cases.

What are the roles of thermistors in various fields?

Applications of NTC thermistors

NTC thermistors are widely used for temperature sensing and control of home appliances, automobiles, and industrial production equipment due to their high sensitivity, high reliability, and low price. According to their applications, they can be divided into: power type NTC thermistors, compensation type NTC thermistors and temperature measurement type NTC thermistors.

Inrush current suppression (power type).

Switching power supplies, motors, transformers and lighting power supplies, etc. have a large inrush current at the moment of connection. This inrush current may damage components (such as MOS tubes) or blow fuses. Connecting an NTC thermistor in series with the load can effectively suppress this current. Before the power is turned on, the thermistor has a large cold resistance that suppresses the current. Under a large enough current load, the resistance value drops to 1/(10~50) of the original value due to self-heating, and the power it consumes decreases as a result. The use of NTC thermistor products can not be frequently switched on and off, when the product is turned off, the NTC thermistor must be fully restored from the high temperature low resistance state to the normal temperature high resistance state to achieve the same surge suppression effect as the last

Temperature compensation.

Most of the quartz oscillators have a strong temperature dependence, in order to obtain good temperature characteristics, usually use a constant temperature bath to keep the quartz oscillator at a certain ambient temperature. However, this makes the equipment huge and costly. Nowadays, quartz oscillator circuits are mostly equipped with temperature compensation circuits to obtain good temperature characteristics over a relatively wide temperature range. Such quartz oscillators equipped with temperature compensation circuits are called TCXO, and as temperature compensation elements are mostly chip NTC thermistors.

Temperature measurement.

The resistance value of an NTC thermistor decreases rapidly with the rise of temperature at a certain measurement power. Using this characteristic, the NTC thermistor can be used to detect and control the temperature by measuring its resistance value to determine the corresponding temperature.

Applications of PTC Thermistors

PTCs are widely used for temperature compensation in circuits, as well as temperature measurement, motor coil overcurrent protection, current control, temperature alarm, constant temperature heating, etc.

Temperature compensation.

PTC components have good positive temperature characteristics, which can compensate the negative temperature coefficient characteristics in transistors or integrated circuits, reduce the loss in the circuit, and can play a role in temperature compensation in a wide temperature range. Take transistor compensation circuit as an example, it avoids the drift of transistor with temperature and makes it work stably in both setting state.

Temperature measurement and control.

The resistance-temperature characteristic curve of the PTC element is highly linear around the Curie temperature, thus creating a temperature sensor that can accurately display the temperature.

Constant temperature heating.

PTC thermistor apparatus has a thermostatic effect. In the circuit, when the beginning of the power, PTC resistance is very small, the power is very large, so that it heats up quickly, when the temperature reaches the Curie point, the component resistance increases sharply, under constant voltage conditions, the current through the component decreases, so that the heating becomes smaller and slowly cools down, and finally the resistance becomes smaller. Continuously repeat the above process, the component in the circuit to play a role in the automatic temperature regulation. This makes the PTC element in the air conditioning circuit is often used.

Overcurrent protection.

In the circuit, the PTC element is connected in series with the load, and when the power is turned on, the resistance value of the PTC element in normal operation does not change much with time, and is basically in a state of equal resistance, while the circuit is also in a stable and effective safe working condition. When the circuit fails, resulting in a high current in the circuit, the PTC element heats up due to its own heating, resulting in a sharp increase in resistance value, resulting in a reduction in the current in the circuit, making the load device is protected, which is the basic principle of overcurrent protection.

What are the characteristics and functions of a thermistor?

A thermistor is usually a non-linear resistance made of a very temperature sensitive, thermally inert manganese, cobalt, nickel oxide fired semiconductor ceramic material, whose resistance value changes with temperature.

Thermistors are classified by temperature coefficient into negative temperature coefficient (NTC), positive temperature coefficient (PTC) and critical temperature coefficient.

The resistance value of positive temperature coefficient resistors increases with temperature, the resistance value of negative temperature coefficient resistors decreases with temperature, and the resistance value of critical temperature coefficient resistors is basically zero when the temperature is near the critical temperature.

Most thermistors are direct heat type, i.e., the heat source is obtained by the resistor itself when passing current.

There is also a side heating type, which requires an external heat source

The most widely used thermistor is the negative temperature coefficient thermistor (NTC), which can be divided into temperature measurement type, voltage stabilization type, and general type.

There are many different types and shapes of NTCs, including tubular and disc-shaped.

Positive temperature coefficient resistors (PTC) are increasingly used in a wide range of applications, in addition to temperature control and temperature measurement circuits, battery protection board circuits, but also a large number of applications in the demagnetization circuit of color TV sets and refrigerators, electric mosquito repellents, electric irons and other household appliances circuit

label: NTC