Summary of 6 commonly used LED switching power supply input protection circuits
Switching power supply is the abbreviation of switching stabilized linear power supply. The previous power supply products used linear power supply, which is a transistor linear stabilized power supply, due to low efficiency and other reasons has been gradually replaced by switching power supply. Switching power supply, as the name implies, is a stable power supply that maintains the output voltage by controlling the on-off time and off-off time of the switch tube.
LED switching power supply,
input protection circuit is very important, switch input protection circuit with overcurrent protection, overvoltage protection and surge suppression and other functions, for the grid voltage shock and EMC has a crucial role. The following six types of switching power supply input protection circuits are listed:
One, fuse form
The fuse has the common type also has the fast type, has the melting point low, the fuse speed fast characteristic, but in the fuse when can produce the spark, the smoke, even has the glass tube to be able to burst, therefore the safety is poorer. Only the input protection circuit of the fuse, only the overcurrent protection, the actual fuse current when the general choice of fuse to be equal to the rated current 1.5 times or so.
Two, fuse, pressure - sensitive resistance form
This kind of circuit more pressure sensitive resistance, pressure sensitive resistance specifications have 07471, 10471, 14471 and other specifications, with surge suppression function, so this circuit has overvoltage, overcurrent protection function, some also have lightning protection.
Fusible resistor and varistor、
The fuse resistor has the same function as the fuse, which is to protect the overcurrent. However, unlike the fuse, the fuse resistor will not produce sparks or smoke when it is fused. In terms of safety, the safety is higher. The piezoresistor has the function of absorbing surge voltage, so this circuit form has the function of overvoltage and overcurrent protection.
Fuses and NTC thermistors
The thermistor adopts a negative temperature coefficient, and its resistance decreases with the increase of temperature.
Five, pressure sensitive resistance, NTC thermistor form
Fuses, varistors, NTC thermistors