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 [ 1 — 7 ]. The main reason of the driver short lifetime is the smoothing capacitor at the output. Ahmed and El-Sayed A. The efficiency can be improved further using an inductor with smaller internal resistance and transistor with smaller ON resistance. The minimum ratio of ripple voltage to DC voltage is around 1.
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The capacitor-less LED drive is an LED drive circuit having a design based on the utilization of the internal capacitance of the LED to replace the smoothing capacitor capaacitorless a conventional buck converter in a power supply.
Pulse signal processing Capaacitorless optimization Simulation. This value can be estimated from the knees of each curve in plotand it depends on the forward current as well, since it depends on how deep the LED is in the conduction region.
Wu Chen and Hui, S. The design used a storage capacitor and a two-winding dual inductor. Description of the Related Art Light emitting diodes LEDs are beginning to experience widespread use in many lighting applications. Combining 4 czpacitorless 5the output voltage ripple is given by where. This indicates that as the DC current increases, the value of the resistance will decrease.
Plots and of FIGS.
It is important to point out that the value of C d is linearly changing with the DC current only in strong conduction mode. An LED or an array of LEDs connected in parallel to each other is connected between the cathode of capaciforless D 1 and a second lead of inductor L capacitorlesss 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 minimum ratio of ripple voltage to DC voltage is around 1.
If the voltage across the LED is below a certain value, there will be no diffusion capacitor and the LED’s voltage will drop logarithmically, causing the large error shown.
Such a configuration can be utilized to enlarge the total internal capacitance, and hence minimize the output ripple. From This Paper Figures, tables, and topics from this paper.
US9648684B1 – Capacitor-less LED drive – Google Patents
Efficiency is an important factor in an LED drive. We have carried out many experimental tests to come up with a new mathematical model that represents the DC output voltage across the LEDs.
This case will satisfy the ideal situation with a negligible load effect on the ripple voltage. It is important to point out that the value of is linearly changing with the DC current only in strong conduction mode [ 12 ]. The major intention of this paper is to build upon the results obtained in [ 9 ] and present the mathematical model and experimental results to confirm the functionality of the capacitoorless.
USB1 – Capacitor-less LED drive – Google Patents
Also, the switching frequency is selected such that a minimum ripple appears at the output. Most of the works presented require capacitorldss complicated power circuits or current controlled technique to reduce the size of the energy storage capacitor. Increasing the frequency further will lead to smaller ripple voltage and smaller components for better integration. The circuit shown in Figure 2 was connected in the laboratory using off-the-shelf components to test the proposed design experimentally.
References Publications referenced by this paper. In other words, all the current I pp will flow through the capacitor.
Modified harmonic injection technique for electrolytic capacitor-less LED driver
Light emitting diodes LEDs are beginning to experience widespread use in many lighting applications. As is clear from capacitorlexs figure, as the duty cycle increases, the DC output voltage increases. Because of the slight changes in the DC output voltage, the efficiency is barely changing with the change of the frequency, as shown in plot of FIG. The design is based on the utilization of the internal capacitance of the LED to replace the smoothing capacitor.
This fact is supported by the experimental results we have carried out and it is explained in the next section. The nonlinearity is clearly shown in Figure 8where the OFF period was long enough to drive the LED to the weak conduction region while the ripple of Figure 9 is almost linear. 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.
Correspondence should be addressed to Munir Al-Absi ; as.
The internal capacitance of the LED array will act as a smoothing capacitor if a proper switching frequency and duty cycle are chosen, and hence no external smoothing capacitor is needed. Lighting device for solid-state light source and illumination apparatus using same.