Starting electronic facility (like switch power source (SMPS) or inverter) when, the instantaneous that the meeting in equipment is worth through having a height is unusual electric current. This kind of electric current is called excitation current, if do not have protective circuit, it may destroy semiconductor device or the service life that affect flowing capacitor. NTC thermal resistor uses as ICL (excitation current is restrained implement) when, the circuit that can protect electric, electronic parts effectively avoids the effect that suffers excitation current.

 

 

The advantage of NTC thermal resistor

NTC thermal resistor is one kind collects appliance to have negative temperature coefficient (NTC) the temperature that special semiconductor pottery and porcelain makes is relevant resistor. They have very tall resistance below room temperature, quantity of heat produces in the meeting when electrify, and as temperature elevatory, resistor can drop. Because have this kind of character, they are used as electric the voltaic protector with electronic equipment, restrict unusual electric current effectively, include the excitation current when electrify. Use as the NTC thermal resistor of voltaic protector also calls power source thermal resistor.

 

Fixed resistor or NTC thermal resistor can use limitative excitation current. However, fixed resistor always brings about power loss and function to drop. NTC thermal resistor restricts excitation current with taller initiative resistor, next as a result of electrify temperature is elevatory, resistor falls hundred of room temperature level, achieve the power loss with fixedder than using smaller resistor thereby. In other words, the effect of the fixed resistor that restricts the effect of excitation current to have identical and initiative power loss than using with NTC thermal resistor wants big.

 

It is NTC thermal resistor below the applied give typical examples in restricting excitation current.

 

Apply 1: Switch power source (SMPS) medium excitation current limitation

All sorts of switch power source (SMPS) —— their bulk small, weight the power source that tall —— of light, function is used as electronic equipment normally. When SMPS electrify, the excitation current that has high peak value can charge to flowing capacitor, charge to device then. Because current of this kind of excitation is met,the service life to capacitor produces an effect, damage the contact of mains switch or destroy rectification diode, be necessary to take corresponding the way to deal with a situation so.

 

Following plan institute are shown, will restrict the excitation current of SMPS through inserting NTC thermal resistor, the low cost of current of the excitation in be being used as to restrict power supply widely is simple and easy circuit. Although be after rectifier circuit join NTC thermal resistor, also can get same result.

 

Graph 1: The excitation current in switch power source is restricted
 

Apply 2: Communicate – the excitation current limitation in module of direct current source

All sorts of power source circuit and periphery circuit are compact the ground is compositive arrive one case inside buy power source calls power source module. Communicate – module of direct current source is by communication – dc commutate circuit, dc – dc converter and the power source that a few exterior component constitute, can form an economic space optimize power source system. Insert thermal resistor of a NTC (power source thermal resistor) effectively limitation brings to bear on when electrify current of the excitation on input and output capacitor.

 

Graph 2: Communicate – the excitation current limitation in module of direct current source