In recent years, LED lighting has gradually been promoted and applied by all walks of life. LED lamps that LED households can consume are bulb-type LED lamps sold by major lighting manufacturers. Many companies have also developed fluorescent-type LED lamps, which have different characteristics from traditional light sources such as incandescent lamps and fluorescent lamps. . To make LED lights, you can't make good lighting fixtures by relying solely on LED packaging . In order to design a better LED lighting fixture, the correct circuit design must be distinguished from the traditional light source.
This article introduces the design of LED lighting fixtures, including the LED lighting principle and main parameters, drive circuit, heat analysis and other aspects.
one. LED lighting principle and main parameters
1. LED lighting principle
The LED is a type of electronic diode, and the main structure is a PN junction. As shown in Figure 1, when a voltage is applied to both ends of the LED, the electrons absorb energy and transfer to the valence band, and then release the absorbed energy. The energy that is released is light. The wavelength and color of the emitted light are determined by the potential difference of the semiconductor.
Figure 1 LED operating principle
LEDs have similar characteristics to typical silicon diodes, applying a voltage between the positive and negative electrodes. When the applied voltage reaches a critical value, a current is generated in the LED to start emitting light. When the voltage exceeds this threshold, the current increases sharply. The threshold voltage of the white LED is about 3.5V. The red, green, and blue LED threshold voltage values ​​are shown in Table 1.
Table 1 LED lamp summary
We use circuit simulation to illustrate the electronic characteristics of the LED and the driver circuit. Circuit simulation is an easy way to model the electronic design of LEDs and resistors and simulate the operation of a computing circuit on a computer. Here is the circuit simulation PSpiceA/D from Cadence. At the same time, Philips Lighting's LUXEON series LX3-PW71 was used.
First use the circuit of Figure 2 to verify the electronic characteristics of the LED. To obtain voltage-current characteristics, DC analysis is required.
Figure 2 Verify voltage-current characteristic circuit
The analysis results are shown in Figure 3.
Figure 3 Analytical results based on PSpiceA/D: voltage-current characteristics
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