The effective capacitance of the LED is found as follows: Hanson , David J. Bender , Henrique A. The proposed design is a modified version of the design in Figure 1 and is shown in Figure 2 , where the load is an array of LEDs, as it is the case in all commercially available LED lamps. Combining 4 and 5 , the output voltage ripple is given by where. Dragan, Fundamentals of Power Electronics , vol.

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US9648684B1 – Capacitor-less LED drive – Google Patents

A new approach to designing capacitor-less buck DC-DC converter was developed and tested. As for LED lighting applications, the LED load needs to draw high current specially when using a capacitor-less drive. Rewriting 6 to find the effective capacitancePlots of the effective capacitance as a ked of the LED current for different frequencies are shown in Figure 5.

High power factor, electrolytic capacitor-less driver circuit for light-emitting diode lamps. The Proposed Design The proposed design calacitorless based on the well-known buck converter shown in Figure 1where the output voltage is the voltage across the load resistance and. From circuit and modelassume no diffusion capacitance, C d.

Increasing the frequency further will lead to smaller ripple voltage and smaller components for better integration. The effective capacitance of the LED is found as follows:. Indexed in Web of Science. Moreover, the value of C d also is a function of the conductance, and its value will increase as the current increases.


It is clear from plot that as the duty cycle increases, the DC output voltage increases. Dalla CostaTiago B. The ripple voltage decreased with the increase in frequency.

References Publications referenced by this paper. The LED equivalent circuits shown in Figure 3 are used in this analysis. In conduction mode, r d is the reciprocal of the conductance, which is equal to the DC current divided by the thermal voltage.

However, during the OFF period in the switching Buck converter pulse, the LED internal resistance will draw the stored charge, and the output voltage will decrease. Several works on electrolytic capacitor-less LED drives have been presented to maximize the overall lifetime of the LED system and the recent states of the art are given in capacitprless 1 — 7 ].

A New Capacitor-Less Buck DC-DC Converter for LED Applications

BenderHenrique A. Efficiency is an important factor in an LED drive. It is clear form Figure 4 that as the current increases, the value of will decrease.

US USB1 en The circuit shown in Figure 2 was connected in the laboratory using off-the-shelf components to test the proposed design experimentally. Because of the slight changes in the DC output voltage, the efficiency is barely changing with the change of the frequency, as shown in Figure An LED or an array of LEDs connected in parallel to each other is connected between the cathode of diode D 1 and a second lead of inductor L the anode of the LED being connected to cathode of diode D 1and hence the positive terminal of the rectifier circuitand the cathode of LED being connected to the second lead of the inductor L.


The output voltage is measured across the LED packages. The rest of the paper is organized as follows: The value of depends on the current passing through the LED, and it can be deduced from the characteristics curve of the LED shown in Figure 4.

Several works on electrolytic capacitor-less LED drives have been presented to maximize the overall lifetime of the LED system. The main reason of the driver short lifetime is the smoothing capacitor at the output. As shown in FIG. The capacitor-less LED drive circuit is based on a buck converter circuit where an LED replaces the smoothing capacitor.

Dragan, Fundamentals of Power Electronicsvol. If the OFF period is long enough, the value of the diffusion capacitor will be capaitorless small, causing a dramatic drop in the output voltage that might cause flicker in the LED light.

Combining 4 and 5the output voltage ripple is given by where.