The problem that white light LED light source needs to pay attention to in practical application (Figure)

Introduction led (Light Emitting Diode) light source is an energy-saving new, long-life, environmentally friendly, with the rapid development and decrease the production cost of the LED light source technology, which is used in a proportion in the lighting field gradually increased. If LED lighting source is used to replace 50% of the current traditional lighting source, the annual energy saved in China is equivalent to the sum of the power generation of the Three Gorges Power Station, and its energy saving benefits are considerable. The prospect of LED light sources in the lighting market has attracted worldwide attention, and it is bringing a new green revolution to the lighting field.
LED is used as the lighting source for access to the mains. In practice, there are still a series of problems to be optimized:
(1) The LED driving mode is constant current driving, so as to ensure uniform luminous intensity;
(2) Since the performance of the LED may be greatly changed or even damaged due to temperature, it is necessary to solve the heat dissipation problem;
(3) A single LED lamp bead (chip) can be approximated as a point source. When used as an illumination source, it must improve the angle of light emitted in all directions, making it easier for the human eye to accept it for a long time.

1 constant current drive

Figure 1 shows the volt-ampere characteristic of a 1W class high power LED chip with input forward voltage.

Actual measured turn-on voltage of this chip is approximately Uon = 2. 3V, the LED is turned on once, wherein the current and the voltage at both ends of the access flows increase approximately exponentially, the relationship can be expressed as:

Current formula, i is flowing; Is is the saturation current response; Q is the electron charge; U is the voltage across; K is Boltzmann's constant; T is the thermodynamic temperature. (1) Figure 1 shows the formula and, when driven by constant voltage, when the voltage across the presence of a weak fluctuation current through the abrupt change will occur, it is clear that performance is also a weakening of the LED itself, the The latter analysis will also know that this will also have a greater impact on the intensity of the illumination, which is obviously not allowed in the field of illumination.

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