The effective capacitance of the LED is found as follows:. Capacitor Device Component Search for additional papers on this topic. Plots and of FIGS. Efficiency is an important factor in a LED driver. The efficiency can be further improved using an inductor with smaller internal resistance and a transistor with smaller ON resistance. The circuit shown in Figure 2 was connected in the laboratory using off-the-shelf components to test the proposed design experimentally.
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Modified harmonic injection technique for electrolytic capacitor-less LED driver – Semantic Scholar
In [ 1 ], a current injection approach is used. In the AC model cspacitorless Figure 3the behavior of and gives an indication that as the DC current increases, the ripple voltage will decrease, which is another parameter that can be controlled and affect the ripple voltage. Increasing the frequency further will lead to smaller ripple voltage and smaller components for better integration.
Efficiency is an important factor in a LED driver. It is clear form Figure 4 that as the current increases, the value of will decrease.
USB1 – Capacitor-less LED drive – Google Patents
The capacitor-less LED drive ldd is based on a lec converter circuit where an LED replaces the smoothing capacitor. The proposed design is based on the well-known buck converter shown in Figure 1where the output voltage is the voltage across the load resistance and.
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.
Therefore, it is insufficient to use this type of capacitors in LED driver. Mathematical analysis and experimental results are given in Section 3. Capacitor Device Component Search for additional papers on this topic. It is clear from plot that as the duty cycle increases, the DC output voltage increases. 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 current increases, the value of RLED will decrease. A capacitor-less LED drive, consisting of: 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. 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. The minimum ratio of ripple voltage to DC voltage is around 1.
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. Equations 3 and 4 can be written as: This value can be estimated from the knees of each curve and depends capacitorlss the forward current as well, capacitoorless it depends on how deep the LED is in the conduction region.
Section 4 concludes the paper. Conventional LED drive has a limited lifetime due to present of bulky electrolytic output capacitor E-Cap which capacitorlesa essential to make the power difference balancing between the constant output power and the pulsating input power. The DC output and ripple voltage are plotted in Figure 6.
The efficiency versus the duty cycle at different frequencies. The output DC and ripple voltage versus frequency. BragaMarco A.
US9648684B1 – Capacitor-less LED drive – Google Patents
From This Paper Figures, tables, and topics from this paper. Switching power supply for an illumination device with precision current control. These and other features of the present invention will become readily apparent upon further review of the following specification and drawings.
The drain of Q 1 is connected to the anode of diode D 1 and to a first lead of inductor L, The cathode of diode D 1 is connected to the positive terminal of the AC-DC rectifier circuit It is important to point out capacitorkess the value of C d is linearly changing with the DC current only in strong conduction mode.