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  • 120Vac Off-Line LED Lighting Driver Evaluation Board

  • Created: Jun 16, 2016

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Summary

The illumination and lighting provided by LED is known to be more efficient compared to the traditional light bulbs. However, these LED lights require reliable power supply that ensures DC and prevents voltage transients. This evaluation board features HV9805 IC that is designed for general LED lighting products. It has an approximate maximum power rating of 25W at 120Vac. It provides true DC and protects load from line voltage transients. It has high power factor typically 0.98 and highly efficient around 90%.


This off-line LED driver circuit is divided into two stages while the HV9805MG-G IC serves as the main component that drives the high-voltage LED load. The first stage is the boost converter, this part is for stepping down the current while pulling up the voltage. It is comprised of bridge rectifiers, series line filter, and some discrete components that helps the power transfer of AC line to the second stage. The DRV pin, which works in the boundary of these two stages topology, is used to control the conduction state of the boost converter switch by controlling an external high-voltage FET (M1) in series with the internal low-voltage FET of the driver IC. With that method of having those FETs in series, it is now in cascode switching configuration. The second stage is a linear regulator in series with the LED lighting load, this part is for controlling the current that is feed to the possible LED load. It is comprised of FETs, diodes, and also some discrete components that transfers power from the first stage to the LED lighting load, with true constant current. Also, it offers protection of the LED lighting load from overvoltage that may pass from mains to the output of the first stage. The CRG pin, which works in the output side of the second stage, is used to control the constant current regulator switch by controlling a low threshold FET or the pass transistor (M2). The CRS pin helps in this current regulation by sensing current passes through the current sense resistors (RCRS). Other discrete components helps to ensure proper operation of the designed circuit.


The LED lighting has abounding applications in which this circuit can help to its development. It resolves some issues that are found on LED lighting like heat management and optics by arranging it as high-voltage load. Meaning, this makes LED lighting in lower forward current compared to a conventional LEDs that relates to heating of this lighting device.

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