Changes inductive boost LED Driver

Posted on Mar 28, 2007

White LED can be used in series or parallel connection, both solutions have advantages and disadvantages. The disadvantage is that parallel the LED current and brightness do not automatically match.

Changes inductive boost LED Driver
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Series to maintain the inherent characteristics of the match, but requires a higher supply voltage. Because the white LED forward voltage drop of 3 ~ 4V (typ), either in parallel or in series, the battery voltage is most portable electronic devices are insufficient to drive the LED, so the need for a separate power supply. In a series configuration, the number of LED's that drive the highest voltage limit. If the maximum voltage of 40V, in a series configuration according to the white LED forward voltage, the maximum voltage that can drive up to 13 white LED, the drive current in the range of 10 ~ 350mA continuous state. Advantage of this configuration is a series of white LED can be used single-wire current; the disadvantage is that when the PCB space is limited (especially when high power), the current density on the copper wire is a problem, but if one in-line mode white LED fails, all white LED will be turned off. However, from a design point of view, if there is a knife only white LED, the battery voltage is necessary to enhance the n Vp, it must step-up structure. You can use inductance element accurately monitor current slope, limiting the EMI uncontrolled instantaneous current. A typical boost topology shown in Fig.

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