压电振荡器供给白光LED发光

压电振荡器供给白光LED发光

　　接收单电池供电的LED驱动器正受到广泛关注。为由低电压电源产生能够点亮白光LED的高电压，主要需要某种电子振荡器，最简单的为压电蜂鸣器。压电转换器特殊地用于振荡器和驱动白光LED（图1）。压电模片或弯曲板组成压电陶瓷片，带双面电极，用可传导粘合剂贴在黄铜、不锈钢或类似材料制成的金属板上。电路使用三端压电转换器。在这个转换器中，模片在其中一个电极上有反应标记。电感和容性器件之间谐振产生振荡。工作的频率为：fOSC=1/(2π)，在这里，L为电感值，C为压电元件的电容量。

　　随着图1电路中电压的最初作用，晶体管Q₁打开。当晶体管传导时，电流通过电感L₁逐渐增加，电压通过金属板使压电陶瓷弯曲。这个弯曲在反应标记上产生负电压，其反过来为晶体管的基极供电。随后晶体管关闭。当关闭发生时，电感存储的能量输进LED。这个反激电压足以点亮LED。

　　英文原文：

　　White LED shines from piezoelectric-oscillator supply

　　A piezoelectric ceramic buzzer

　　TA Babu, Chennai, India; Edited by Charles H Small and Fran Granville -- EDN, 1/10/2008

　　LED drivers that receive their power from a single cell are receiving a great deal of attention. To generate the high voltage for illuminating a white LED from a low-voltage power supply basically requires some form of an electronic oscillator, and one of the simplest is a piezoelectric buzzer. An unusual application of a piezoelectric transducer serves as an oscillator and drives a white LED (Figure 1). The piezoelectric diaphragm, or bender plate, comprises a piezoelectric ceramic plate, with electrodes on both sides, attached to a metal plate made of brass, stainless steel, or a similar material with conductive adhesive. The circuit uses a three-terminal piezoelectric transducer. In this transducer, the diaphragm has a feedback tab on one of its electrodes. The oscillation is a result of the resonance between the inductor and the element, which is capacitive. The frequency of operation is: fOSC="1/"(2π), where L is the value of the inductor and C is the capacitance of the piezoelectric element.

　　With the initial application of potential to the circuit in Figure 1, transistor Q1 turns on. When the transistor conducts, the current through inductor L1 increases gradually, and the potential across the plates flexes the piezoelectric ceramic. This flexing generates a negative potential at the feedback tab, which feeds back to the base of the transistor. The transistor then switches off. When turn-off occurs, the stored energy in the inductor dumps into the LED. This flyback voltage is sufficient to light the LED.

　　英文原文地址：http://www.edn.com/article/CA6515353.html

来源：EDN/作者：TA Babu, Chennai, India