The overcurrent protection device applications of LED lightingon January 4th, 2012 at 1:57 AM
LED bulbs with low power consumption, long life, environmental protection and other distinctive features, small size backlight applications in large-size panel backlighting to infiltrate, it is now further expanded to general lighting applications, is now in the landscape, architecture, business, car, the rapid development of mobile lighting and other fields.
Face of the many LED lighting applications, as the market and there is no unified standard, there is a wide range of drive solutions, but they never deviate from them, from the perspective of the whole over-current protection according to the input current to lamp body can be divided into: DC input and AC input power are two basic types, the main difference between two types of drivers have AC to DC power supply modules. Of course, there are many on the market resistance, RC Buck and other low-cost solution, there is no EMI rectifier and constant current driver module, but due to the selection of the primary-side fuse requirement is consistent with Figure 2, included in this second type.
Overcurrent protection for LED lighting has three main purposes:
First, the purpose of protecting personal and property safety, usually in relatively high power input voltage applications often increase the protection devices for this purpose.
Second, the sub-system with the outside world cut off, if the external system instability will affect the security subsystem; the other hand, damage to the device occur within subsystems, such as a short circuit failure mode of the device in parallel, or because of external factors had led to internal security the destruction of the insulation levels, leading to internal short circuit to ground, if the system does not fuse action with the outside world cut off again failed to take effective measures, will result in action outside the system of the insurance system, which will result in the intermittent power supply system, and This and other important places such as hospitals will indirectly cause unexpected losses, and may even result in casualties, sometimes need to add two power input fuse.
Third, to protect important and valuable electronic components or devices. For LED lighting is, LED lamp beads total cost of most of the cost of lighting in the non-power-driven or non-isolated constant current drive circuit, the output needs to drive the necessary overcurrent protection.
As the power input of the structure is not the same as in the selection of overcurrent protection devices have a larger focus on the difference between:
1, the DC input for the selection of the type of DCin fuse, the fuse needs particular attention to the temperature reduction coefficient of parameters, due to the heat than the larger high-power LED, led lamp cup in the internal temperature is relatively high, if the choice of temperature reduction compared large current fuse will choose the larger size, in the same operating current, the current large size of the fuse of protection relative to lower the number of; other DCin position, capacitor filter will be used as back-end, will produce relatively large power pulse current, so this should be noted that rigorous site selection fuse consider pulse, otherwise easily lead to wrong option fuse has been thrust power pulse phenomenon, difficult to switch machines after the experiment many times and surge current experiment, in this recommended strong pulse-resistant products.
2, the output of the fuse for the driver selection, reduction in pay attention to the temperature coefficient fuses also need to consider the fuse speed indicator, because here the current volatility is not unusual in the circuit or component failure cases, quickly cut off the circuit to protect the back of the LED light string, in this location is recommended to select the type of fast break off and reduce the temperature fuse.
Above two kinds of occasions on the market more generally of low voltage fuses are available chip, such as the AEM technology SolidMatrix ® technology fuses, sizes from 0402-1206, the current size from 0.5 to 30A, a fast break, quickly broken, resistant to high pulse, slow down and so many different series, different specifications, different characteristics of the product for you engineers use.
3, while for the AC input LED lighting ACin position, especially LED ball bulbs only need to consider the size of the fuse problem, but also need to consider the resistance voltage fuse. But now the market can withstand wide voltage range of AC fuse is generally relatively large size, little patch of small size fuse voltage rating up to 250VAC, the application for this predicament, AEM technology introduced AirMatrixTMAF2 series SMD fuses, volume Only 6.1mm * 2.5mm * 2.2mm, petite stature but can withstand 250VAC voltage, but also has high consistency, low resistance, high resistance to pulse capability, etc., will bring you to experience new applications engineer friends .
Some engineers use a friend that fuses both positive and negative, neutral line of fire in the event of over-current can be broken, can play a protective role. Engineer friends here to share with you the experience, the fuse need to have the potential difference of the line, using the ground line fuse can cut off the circuit, but after cutting off the entire lighting appliances and the earth potential difference still exists, in the event of internal device short circuit will result in danger. So in some anti-plug socket can countries such as Germany or China, from a security perspective, some may need to consider anti-plug in the LED lighting fixtures are coupled with the best of LN fuse.