Switch power source is in when switching on the mobile phone, 220V alternating current, through insurance and thermal resistor, after rectification, charge to capacitance, and the character of capacitance, it is instantaneous charging current it is big, bring concussion to the rectification diode in front, fuse thereby, cause damage easily, to raise the coefficient that power source designs, often join resistor to undertake current limliting after insurance, when resistance is greater, effect of though current limliting is good, but the electric energy that resistor wastes also is bigger, after switch power source is started, current limliting resistor already did not have action, waste electric power instead.

 

Effect of better to achieve current limliting and province report, present switch power source often uses negative temperature thermal resistor to make current limliting use (absorb surge electric current) , the character of negative temperature thermal resistor is, temperature is higher, resistance is less. When normal temperature, resistor is 8~10 Europe commonly, bigger, when switching on the mobile phone, have better current limliting effect, after power source is started, working electric current passes thermal resistor, make its calorific, value of thermal resistor block falls considerably (make an appointment with 1~2 Europe) , after making thermal resistor is started in power source, electric power is used up fall low.

 

  

After switch power source is started, shed resistor to reduce this to be restricted use up, besides using negative temperature thermal resistor, still have use relay (after power source is started, suck close short receive current limliting resistor two end) , and in the television, special still used circuit of a two-way silicon, after power source is started, working electric current drops to be worth certainly, two-way silicon guides, thereby short the two end that received current limliting resistor, make current limliting resistor is used up fall for 0.

 

The action of the thermal resistor in switch power source is a kind of control to temperature actually, can achieve very good current limliting effect, in avoiding to start a process in switch power source, electric current perhaps causes loss too quickly greatly too. Advocate battalion electroanalysises capacitance of capacitance, pottery and porcelain, thermal resistor, pressure quick resistor is waited a moment.