Novel Single Stage Power Factor Corrected LED DriverTopology for Space Constrained Applications of AircraftExterior Lighting System

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:

 

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.

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.

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

Critical Current Control (C3) and Modeling of a Buck Based LED Driver with Power Factor Correction

ABSTRACT

Buck converter has a good aptitude for LED driver application. Here a new technique introduced to control and model a buck converter in the closed loop condition using Lagrange equation. To improve the final model accuracy, parasitic elements of the converter are taken into account. The main advantage of this method is its novelty and simple implementation. Also, the converter power factor has improved under critical current control (C3) technique. Frequency response and step response of the small signal model are derived and analysed. The theoretical predictions are tested and validated by means of PSIM software. Finally, precise agreement between the proposed model and the simulation results has obtained.

 

INDEX TERMS:

  1. Power factor correction
  2. LED driver
  3. Buck converter
  4. Small signal model.
  5. critical current

 

SOFTWARE: MATLAB/SIMULINK

  

CIRCUIT DIAGRAM

critical current control

Fig. 1. Converter overall circuitry by C3 method in the PFC mode

 

SIMULATION RESULTS

Fig. 2. Converter source current and voltage along with each other

Fig. 3. Reference current, input voltage and current after the bridge

Fig.4. Harmonic contents of the converter input current

Fig.5. Output voltage at the start-up moment

Fig.6. Output capacitor current

Fig.7. Load change effect on the converter input current

CONCLUSION

This paper analyses a buck based LED driver with improved power factor. Power factor correction is done using critical current control (C3) or borderline conduction mode (BCM). Also, the Lagrange differential equations are employed here as an efficient tool for switching converter modeling in the closed loop condition. The proposed modeling technique gives the designer better intuition about the circuit under study rather than traditional state space averaging (SSA) method. SSA is a tedious and fully mathematical tool for switching converters modeling. In addition, parasitic elements of the converter have taken into account so it helps to select the circuit parts value correctly before manufacturing process. Dynamic behaviour of the converter is analysed in both frequency and time domain such as transfer functions and step response. A PI compensator is employed in the closed feedback loop to stabilize and modulate the reference current amplitude corresponding to the demanded power. Since this method relying on the averaging method, then the final model is reliable from 0 Hz up to half of switching frequency according to the Nyquist theorem. Finally, the simulation results confirm the proposed model exactness and indicate the rapidity of system step response under compelling conditions.

 

REFERENCES

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  • Gajowik T., Rafał K., Bobrowska M., Bi-directional DC-DC converter in three-phase Dual Active Bridge Topology, Przegląd Elektrotechniczny, 05(2014), 14-20.
  • Kazmierczuk M.K., Pulse Width Modulated DC-DC Power Converters, Wiley, Ohio, 2008.
  • Ben-Yaakov S., Average simulation of PWM converters by direct implementation of behavioural relationships, IEEE Conf. , APEC, 1993, San diego, CA., 510-516.
  • Shepherd W., Zhang L., Power Converter Circuits, Marcel & Dekker Inc., New York, 2004.