**ABSTRACT:**

This paper proposes a novel converter topology based on a single stage LED driver with Power Factor Correction (PFC) which is optimized for weight, volume and cost, for space constrained environments such as Aerospace exterior lighting product. The proposed topology utilizes a single switch to harmonize the input current as well as control the intensity of lighting system.

A typical Power Factor Pre-regulator (PFP) uses a bulk energy storage capacitor, which is subjected to wear out at higher altitudes due to low pressure conditions and freezes at negative temperatures, resulting in poor reliability converter for Aerospace applications.

Unlike a regular Power Factor Pre-regulator (PFP), the proposed topology avoids the use of bulk energy storage capacitor which results in a fast transient response with enhanced reliability, reduced board real estate and weight. The proposed LED driver topology can control the LED current with both Buck and Boost mode of control, making it a good choice for applications with wide input voltage variation.

A 110 W prototype based on proposed converter was built to verify the operation of proposed topology. The experimental results are in line with the predicted performance. The proposed converter is able to achieve a power factor of 0.988 with an input current THD of < 10%.

**SOFTWARE:** MATLAB/SIMULINK

**BLOCK DIAGRAM:**

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Figure 1. Proposed LED driver topology with single stage active PFC

** ****EXPECTED SIMULATION RESULTS:**

Figure 2. Measured waveforms at 90V AC input (a) Input Voltage (Red) (b) Input current (Blue) (c) Average Voltage drop across LED current sense resistor (green) (Equivalent to LED average current as the sense resistor value is 1ohm.

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Figure 3. Measured Linear FFT of input current

Figure 4. Start-up transient at 90V AC input (a) Input Voltage (Red) (b) Input current (Blue) (c) Average Voltage drop across LED current sense resistor (Green)(Equivalent to LED average current as the sense resistor value is 1ohm.

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Figure 5. Current profiles through various power circuit components (a) LED Current (Green) (b) Current through MOSFET M1 (Red) (c) Current through inductor L2 (Blue) (d) Current through Inductor L1 (Purple)

Figure 6. Current profiles through various power circuit components (a) LED Current (Green) (b) Current through MOSFET M1 (Red) (c) Current through inductor L2 (Blue) (d) Current through Inductor L1 (Purple)

Figure 7. Measured waveforms at 132V AC input (a) Input Voltage (Light Blue) (b) Input current (Blue) (c) Average Voltage drop across LED current sense resistor (Red).

Figure 8. LED current profile over one rectified line cycle

** ****CONCLUSION: **

This paper presents a novel LED driver topology, capable of input power factor correction, for space constrained applications, such as Aerospace exterior lighting product line. Due to the compact design of the proposed LED driver topology, it can be of great advantage for an integrated power supply solution for Aerospace exterior lighting product offerings.

The proposed LED driver topology can control the LED current with both Buck and Boost mode of control, making it a good choice for applications with wide input voltage variation. The proposed LED driver topology has been verified by mathematical analysis, circuit simulation and performance has been demonstrated experimentally as well. The proposed LED driver topology promises an appreciable amount of savings in term of real estate, power loss, and heat sink requirements while enhancing the power density of the converter and its reliability.

Typically, it’s the bulk output capacitor that wears out with pressure variation (wear out phenomenon accelerates at altitudes more than 8000m due to the reduced pressures); which can be avoided with the proposed topology. Depending upon the load (number of LEDs) and input voltage; in order to protect LEDs, a reverse blocking diode may be required during the Buck operation. For Boost application, reverse blocking diode will not be required even with today’s technology. Authors have been granted a U.S. Patent 9363291 [8] against the proposed novel LED driver topology.

** ****REFERENCES:**

[1] L. H. Dixon, “High Power Factor Preregulators for Off- Line Power Supplies,” Unitrode Power Supply Design Seminar Manual SEM600, 1988. (Republished in subsequent Manuals)

[2] Spiazzi, G., and Mattavelli, P. (1994) “Design criteria for power factor preregulators based on SEPIC and Cuk converters in continuous conduction mode,” IEEE IAS Conference Record, 1994, 1084-1089.

[3] Z. Ye, F. Greenfeld, and Z. Liang, “Single-stage offline SEPIC converter with power factor correction to drive high brightness LEDs,” in Proc. IEEE Appl. Power Electron. Conf., 2009, pp. 546–553.

[4] C.Zhou and M.Jovanovic, “Design Trade-offs in Continuous Current-Mode Controlled Boost Power-Factor Correction Circuits”, HFPC Cod. Proc., 1992, pp. 209-220

[5] L. H. Dixon, “Average Current Mode Control of Switching Power Supplies,” Unitrode Power Supply Design Seminar Manual SEM700, 1990