Study on failure mechanism of LED lighting drive circuit

Review: as a result of LED driven research and development of enterprises and many people, its technical level is uneven, the quality of the LED driver circuit is different. Led to the failure of LED lamps often occur, hindering the LED lighting often promote.

In recent years engaged in LED manufacturing, and R & D personnel greatly increased. LED companies are springing up like mushrooms. Due to engage in LED driven R & D enterprise and a large number of people, its technical level is uneven, the quality of the LED driver circuit is different. Led to the failure of LED lamps often occur, hindering the LED lighting often promote.

LED lamp failure

First, from the power supply and drive failure; two is derived from the failure of the LED device itself. This article tries from the actual driving circuit of LED power supply on the one hand, analyzing the working principle of the circuit, and then try to drive from the circuit under different conditions of LED, analysis of various sensitive parameters on the failure effect, to analyze the failure mode. Finally, through the simulation to verify the results. The solution of failure is given in theory.

Principle of LED drive circuit

LED is a semiconductor material made of light emitting diode, only unidirectional conduction, and the turn-on voltage is not high, the forward conduction current is not too big, so the power supply of LED have certain requirements, then the driving circuit of LED came into being. In actual use, most of the LED products are the use of alternating power supply as the driving circuit of the LED power input, through the drive circuit into a regulated output form or a constant current output circuit. LED drive circuit, according to the different standards can be divided into many types, at present, the circuit drive principle, can be divided into two categories: one for the linear drive circuit, a kind of switching drive circuit.

Linear driving circuit

Linear drive circuit schematic shown in Figure 1, the structure generally includes the following parts, the rectifier circuit, filter circuit, voltage regulator circuit.

The full wave bridge rectifier is used in the picture, which makes the alternating power supply to be rectified into a unidirectional pulse voltage. Take RC filter to filter circuit, filter circuit consists of a voltage out of value has been relatively close to the DC power supply, however, because of the voltage fluctuation on the grid, causes the output driver circuit voltage fluctuations, which is fatal for LED. So the voltage after the filter needs to be coupled with a voltage regulator circuit. In order to make the linear drive circuit can maintain a relatively stable voltage to drive LED. In a linear drive circuit, the brightness of the LED is a function of the current, but not related to the voltage drop on the LED. From the circuit principle diagram above it can be seen that the linear LED driving circuit, simple structure, easy realization, short development cycle, low production cost, small volume, and, because of not using a lot of large capacity capacitor and inductor, circuit design does not need to consider the EMI problem. Suitable for low current lighting system.