Development of DC-Powered LED Lamp Driver Circuit for Outdoor Emergency Lighting Applications

Abstract

In the event of power outages caused by natural disasters, accidents, or other emergencies, outdoor emergency lighting systems play a critical role in providing illumination to maintain spatial orientation, facilitate evacuation procedures, and help individuals avoid hazardous areas or locate safe shelters. Compared to traditional lighting technologies, LED-based outdoor emergency lighting offers several advantages, including compact size, long operational lifespan, low energy consumption, high safety, resistance to breakage, and the absence of chemical residue or pollution. These characteristics align with contemporary trends in environmental sustainability and energy efficiency. This study proposes a novel LED driver circuit architecture for outdoor emergency lighting applications. The primary circuit topology is based on an improved buck-boost converter integrated with a flyback converter, forming a hybrid buck-boost-flyback configuration. The proposed circuit is capable of recycling the energy stored in the transformer’s leakage inductance, thereby enhancing overall power conversion efficiency. A 12 W (20 V/0.6 A) prototype LED driver circuit was designed and implemented to validate the performance of the proposed system. Experimental measurements, including waveform analysis and efficiency evaluation, demonstrate that the driver circuit achieves a high efficiency exceeding 91%. These results confirm the practical feasibility and effectiveness of the proposed electronic driver for LED-based outdoor emergency lighting applications.

1. Introduction

Regions situated along the boundaries of oceanic and continental tectonic plates are particularly susceptible to natural disasters, including earthquakes and severe weather events such as typhoons and hurricanes. During the summer months, the formation of tropical cyclones and fluctuations in atmospheric pressure further increase the likelihood of such events. When the impact of these natural disasters is substantial, it can result in widespread infrastructure failures, such as power outages or complete blackouts. These disruptions may lead to the suspension of high-speed rail services, closure of highways, and the shutdown of educational and governmental institutions due to a lack of electricity. In these critical scenarios, outdoor emergency lighting systems play a pivotal role in supporting rescue and evacuation operations. Whether facilitating fire and disaster response efforts or guiding individuals to safety, these lighting systems serve as an indispensable source of illumination when conventional power supplies are unavailable. Their presence enhances not only the safety and survival rates of affected populations but also significantly reduces the operational burden on emergency responders, thereby improving the efficiency and effectiveness of relief operations. Consequently, the development, deployment, and maintenance of robust outdoor emergency lighting infrastructure should be prioritized by governments, industries, and communities to ensure reliable access to emergency lighting under all circumstances. Outdoor emergency lighting extends beyond basic illumination; it functions as a critical safety device in emergency contexts. Its utility spans several aspects: (1) ensuring personal safety by minimizing risks such as tripping, disorientation, or injury in dark environments; (2) enhancing the efficiency of outdoor operations, including nighttime rescue and repair work, by improving visibility and operational accuracy; (3) supporting contingency preparedness by providing independent lighting unaffected by surrounding environmental conditions; and (4) offering psychological comfort by mitigating anxiety and panic commonly experienced in dark or chaotic settings. These systems are specifically engineered for deployment in situations characterized by unexpected power failures or inaccessible locations. Key applications include: (1) emergency illumination during blackouts, maintaining visibility in low-light or nocturnal environments; (2) support for outdoor recreational activities such as camping, hiking, or fishing; (3) search and rescue operations following natural disasters, including earthquakes, typhoons, and floods; (4) lighting in construction, maintenance, and underground inspection works; and (5) support for military or law enforcement activities during nighttime operations [1,2,3,4,5,6,7,8].

Compared to conventional lighting systems, modern outdoor emergency lighting devices offer several advantages: (1) high luminous efficacy and extended operation time, owing to the use of energy-efficient light sources; (2) compact and portable design that facilitates ease of transport and deployment; (3) compatibility with multiple power sources, including rechargeable batteries, solar panels, and manual generators, enabling flexible use across diverse environments; (4) rugged construction with features such as waterproofing, dustproofing, and impact resistance, ensuring reliable operation in adverse weather and extreme conditions; and (5) integrated multifunctional features—such as USB charging, warning indicators, SOS signaling, and magnetic mounting—to broaden their scope of application. The evolution of light sources used in emergency lighting has progressed from traditional incandescent bulbs, which were inexpensive but inefficient and short-lived, to more advanced technologies. Halogen lamps offered improved brightness and weather resistance but remained energy-intensive. Fluorescent lamps improved energy efficiency and lifespan but often exhibited reduced reliability in low-temperature environments. High-intensity discharge (HID) lamps, including metal halide and high-pressure sodium variants, provided high-output lighting suitable for large areas but lacked portability. In contrast, light-emitting diodes (LEDs) have emerged as the predominant technology due to their high energy efficiency, extended operational life, low thermal output, and superior mechanical durability. As a result, LEDs are now the preferred light source in modern outdoor emergency lighting systems, especially when integrated with battery or solar power solutions, providing a stable, energy-saving, and environmentally sustainable alternative [9,10,11,12,13,14,15,16].

In general, electrical driver circuits used to power LED lamps can be classified into two main categories: isolated and non-isolated topologies. The classification is based on the nature of the input power source, which may either be direct current (DC) or alternating current (AC) [17,18,19,20,21,22,23,24,25,26]. For isolated configurations supplied by DC input sources, the flyback converter is commonly adopted due to its inherent galvanic isolation and circuit simplicity. However, its unidirectional energy transfer leads to low transformer utilization. Additionally, a snubber circuit is typically required to dissipate the energy stored in the transformer’s leakage inductance when the power switch turns off. In contrast, non-isolated topologies such as the boost, buck, and buck-boost converters are widely used in DC-input LED lighting systems. A boost converter is suitable for applications requiring an output voltage higher than the input, whereas a buck converter is applicable when the output voltage is lower. A buck-boost converter, offering greater voltage flexibility, can accommodate both scenarios.

Reference [27] proposed a DC-DC converter that integrates boost and flyback functionalities, achieving high voltage gain suitable for low-input-voltage conditions. This topology is well-suited for standby operation in LED street lighting and emergency outdoor lighting applications. In [28], a novel buck-type driver utilizing coupled inductors was introduced for outdoor emergency lighting. This design leverages the leakage inductance of the coupled inductor along with a passive resonant circuit to enable soft-switching behavior and reduce switching losses.

Furthermore, an isolated single-stage LED driver integrating a buck-boost converter with a flyback topology was proposed in [29] for AC input sources. This circuit achieves high power factor (PF), low total harmonic distortion (THD), high conversion efficiency, and reduced voltage stress on the switching device. The ability to support multiple output channels via secondary winding configuration further enhances its flexibility.

Motivated by the need for compact, efficient, and flexible LED driver solutions in DC-powered emergency lighting systems, this study proposes a novel single-stage, single-switch non-isolated buck-flyback converter, which is an extension and further improvement of the literature [30]. The proposed topology combines the characteristics of a buck converter and a flyback converter, enabling operation under input conditions where the LED lamp’s rated voltage may be either higher or lower than the supply voltage. Moreover, the circuit effectively recovers the energy stored in the transformer’s leakage inductance without requiring a snubber circuit, thereby improving overall conversion efficiency.

The remainder of this paper is structured as follows. Section 2 provides a detailed description and analysis of the operating modes of the proposed DC-powered LED lamp driver circuit, specifically designed for outdoor emergency lighting applications. Section 3 discusses the design considerations and parameter selection relevant to the implementation of the proposed circuit. Section 4 presents and evaluates the specifications and experimental results obtained from the constructed prototype. Additionally, a detailed loss breakdown analysis of the prototype circuit is conducted to assess its performance. Finally, Section 5 concludes the paper by summarizing the key findings and contributions of this work.

2. Descriptions and Operational Modes Analysis of the Proposed DC-Powered LED Lamp Driver Circuit for Outdoor Emergency Lighting Applications

Figure 1 shows the proposed DC-powered LED lamp driver circuit for outdoor emergency lighting applications, which integrates a DC-DC buck-boost converter with a DC-DC flyback converter into a single-stage power conversion topology and includes a power switch S_B, two diodes D₁ and D₂, a transformer T_R with a turn N₁ in the primary side and a turn N₂ in the secondary side, two output capacitors C₁ and C₂, and the LEDs for outdoor emergency lighting applications.

Figure 2 illustrates the equivalent circuit of the proposed DC-powered LED lamp driver, designed for outdoor emergency lighting applications, as derived through the analysis of its operational modes. To facilitate the analysis of the circuit behavior, the following assumptions are made:

(a) The magnetizing inductor L_M of the transformer T_R is designed to operate in continuous conduction mode (CCM). The parameters L_lk1 and L_lk2 represent the primary- and secondary-side leakage inductances of the transformer, respectively. It is assumed that the values of L_lk1 and L_lk2 are significantly smaller than L_M; thus, the voltage drops across the leakage inductors can be neglected during analysis.

(b) The energy storage capacitors C₁ and C₂ are assumed to have sufficiently large capacitance such that the output voltage remains approximately constant. Additionally, both capacitors are assumed to have equal capacitance values.

(c) The effects of the antiparallel diode and the turn-on resistor of the power switch S_B are neglected for simplification.

(d) All other circuit components are considered ideal.

Furthermore, the proposed driver circuit possesses the capability to recycle the energy stored in the transformer leakage inductances L_lk1 and L_lk2, thereby enhancing overall system efficiency.

Figure 3, Figure 4, Figure 5 and Figure 6 show the operating mode 1, mode 2, mode 3 and theoretical waveforms of the DC-powered LED lamp driver for outdoor emergency lighting applications, respectively, and the operational analysis is described in detail below.

Operation Mode 1 (t₀ ≤ t < t₁): Figure 3 presents the equivalent circuit corresponding to operation mode 1 of the proposed DC-powered LED lamp driver circuit, intended for outdoor emergency lighting applications. At the initial time instant t₀, the power switch S_B is turned on. During this interval, the input voltage source V_IN delivers energy to both the magnetizing inductance L_M and the primary-side leakage inductance L_lk1 through the conducting switch S_B. The voltage developed across the magnetizing inductor L_M in this mode can be expressed as:

$$V_{LM}(t)=V_{IN}$$

(1)

The current flow through the magnetizing inductor L_M can be expressed by

$$\begin{array}{l}{i}_{LM}(t)=i_{LM}(t_0)+{\displaystyle \frac{1}{L_M}}{\displaystyle {\int }_{t_0}^{t_1}{V}_{LM}(t)dt}\\ =i_{LM}(t_0)+{\displaystyle \frac{V_{IN}}{L_M}}(t_1-t_0)\end{array}$$

(2)

During this operational interval, diode D₂ is in a state of forward bias. The input voltage source V_IN delivers energy to the secondary-side leakage inductor L_lk2 and the output capacitor C₂ via the conducting switch S_B, the transformer T_R, and the forward-conducting diode D₂.

The current flow through the leakage inductor L_lk2 can be expressed by

$$\begin{array}{l}{i}_{lk2}(t)=i_{lk2}(t_0)+{\displaystyle \frac{1}{L_{lk2}}}{\displaystyle {\int }_{t_0}^{t_1}{V}_{Llk2}(t)dt}\\ =i_{Llk2}(t_0)+{\displaystyle \frac{V_O}{2L_{lk2}}}(t_1-t_0)\end{array}$$

(3)

Concurrently, the output capacitors (C₁ and C₂) supply energy to the light-emitting diodes (LEDs) employed in outdoor emergency lighting applications. When the power switch S_B is turned off at t₁, the operation mode 1 ends.

Operational Mode 2 (t₁ ≤ t < t₂): Figure 4 presents the equivalent circuit corresponding to operation mode 2 of the proposed DC-powered LED lamp driver circuit, intended for outdoor emergency lighting applications. At t₁, the power switch S_B is off, and the magnetizing inductor L_M and the primary-side leakage inductance L_lk1 provide energy to the output capacitor C₁ via the diode D₁. In addition, the leakage inductor L_lk2 delivers energy to the capacitor C₂ via the diode D₂. Meanwhile output capacitors C₁ and C₂ continuously provide energy to the LEDs for outdoor emergency lighting applications. When the leakage inductor current I_Llk2 is decreased to zero at t₂, operation mode 2 ends.

Operational Mode 3 (t₂ ≤ t < t₃): Figure 5 presents the equivalent circuit corresponding to operation mode 3 of the proposed DC-powered LED lamp driver circuit, intended for outdoor emergency lighting applications. At t₂, the power switch S_B is off, and the magnetizing inductor L_M and the primary-side leakage inductance L_lk1 provide energy to the output capacitor C₁ via the diode D₁. During this interval, capacitors C₁ and C₂ continue to provide uninterrupted energy to the LEDs, thereby ensuring stable operation of the lighting system. When the power switch S_B is turned on again at t₃, operation mode 3 ends and the circuit reverts to operation mode 1. In addition, it is noteworthy that the output capacitors C₁ and C₂ are sufficiently large to maintain a constant voltage across the LED lamp, thus guaranteeing a stable energy supply throughout the operating process.

3. Design Considerations of Some Circuit Parameters in the DC-Powered LED Lamp Driver Circuit for Outdoor Emergency Lighting Applications

3.1. Voltage Gain V_OUT/V_IN in the Proposed Converter

Based on the volt-second balance theorem, the voltage across the magnetizing inductor L_M during the switch’s turn-on time is equal to the voltage across L_M during the switch’s turn-off time. This relationship can be expressed using the following formula:

$$V_{IN}\cdot Duty\cdot T_S={\displaystyle \frac{N_P}{N_S}}\cdot {\displaystyle \frac{V_{OUT}}{2}}\cdot \left(1-Duty\right)\cdot T_S$$

(4)

where Duty is the duty cycle of the power switches, and T_S is the switching period.

By organizing Equation (4), the description of the voltage gain V_OUT/V_IN in the proposed converter can be given by

$${\displaystyle \frac{V_{OUT}}{V_{IN}}}={\displaystyle \frac{N_S}{N_P}}\cdot {\displaystyle \frac{2Duty}{1-Duty}}$$

(5)

Figure 7 displays the voltage gains V_OUT/V_IN versus duty under different turn ratios N_P/N_S according to Equation (5).

3.2. Design Equation of the Magnetizing Inductor L_M

The magnetization inductance L_MB in the boundary mode can be expressed as follows [31].

$$L_{MB}={\displaystyle \frac{V_{OUT}\cdot N_P\cdot \left(1-D\right)}{2\cdot 2\cdot I_{OB}\cdot N_S\cdot f_S}}$$

(6)

With an output voltage V_OUT of 20 volts, an N_P/N_S of 1, an output current I_OB of 0.6 amperes, and a switching frequency f_S of 50 kHz, the value of the magnetization inductance L_MB in the boundary conduction mode can be calculated as

$$L_{MB}={\displaystyle \frac{V_{OUT}\cdot N_P\cdot \left(1-D\right)}{2\cdot 2\cdot I_{OB}\cdot N_S\cdot f_S}}={\displaystyle \frac{20\cdot 1\cdot \left(1-0.5\right)}{2\cdot 2\cdot 0.6\cdot 50000}}=83.33\mathrm{\mu }\mathrm{H}$$

In order to operate the magnetizing inductor current in continuous conduction mode, the magnetizing inductor L_M is designed to be 129 μH.

3.3. Design Equation of the Output Capacitors C₁ and C₂

The design expressions of output capacitors C₁ and C₂ can be obtained as [31]

$$C_1=C_2={\displaystyle \frac{N_P\cdot (1-Duty)\cdot V_{OUT}}{16\cdot L_M\cdot N_S\cdot f_S^2\cdot \mathsf{\Delta }{V}_{OUT}}}$$

(7)

where ΔV_OUT is the peak-to-peak value of the output voltage occurred on the output capacitor.

Substituting the circuit parameters into Equation (4), with a V_OUT of 20 V, an N_P/N_S of 1, a Duty of 0.5, a f_S of 50 kHz, an L_M of 129 μH, and a ΔV_OUT of 0.01 V, the values of capacitors C₁ and C₂ can be obtained as follows:

$$C_1=C_2={\displaystyle \frac{N_P\cdot (1-Duty)\cdot V_{OUT}}{16\cdot L_M\cdot N_S\cdot f_S^2\cdot \mathsf{\Delta }{V}_{OUT}}}={\displaystyle \frac{1\cdot \left(1-0.5\right)\cdot 20}{16\cdot 129\cdot {10}^{-6}\cdot {50000}^2\cdot 0.01}}=193.8\mathrm{\mu }\mathrm{F}$$

When implementing the circuit, the output capacitors C₁ and C₂ are selected as 680 μF.

3.4. Description of Voltage Stress of the Power Switch

The voltage stress of the power switch used in the proposed converter are expressed by

$$\begin{array}{l}{V}_{DS}=V_{IN}+{\displaystyle \frac{V_{OUT}}{2}}=V_{IN}+{\displaystyle \frac{1}{2}}\times {\displaystyle \frac{N_S}{N_P}}\times {\displaystyle \frac{2D}{1-D}}{V}_{IN}\\ =(1+{\displaystyle \frac{N_S}{N_P}}\times {\displaystyle \frac{D}{1-D}})V_{IN}\end{array}$$

(8)

With an input voltage of 14.8 V, Figure 8 displays the voltage stresses V_DS versus duty under different turn ratios N_P/N_S according to Equation (8).

4. Specification and Experimental Results Along with Loss Breakdown Analysis of Prototype DC-Powered LED Lamp Driver Circuit for Outdoor Emergency Lighting Applications

4.1. Specification and Experimental Results of Prototype DC-Powered LED Lamp Driver Circuit

A prototype DC-powered LED lamp driver circuit with a rated output power of 12 W has been successfully designed, implemented, and experimentally verified. The circuit operates from a DC input voltage of 14.8 V, delivering a regulated output voltage of 20 V and an output current of 0.6 A. The experimental LED lamp is composed of twelve light-emitting diodes (LEDs) connected in series. Each LED is characterized by a rated power of 1.2 W, a rated voltage of 2 V, and a rated current of 0.6 A. Consequently, the overall configuration yields a total rated power of 12 W, a total rated voltage of 20 V, and a total rated current of 0.6 A. The detailed electrical specifications of the proposed LED driver circuit, intended for outdoor emergency lighting applications, are summarized in

Table 1. Specifications of the Proposed DC-Powered LED Lamp Driver Circuit for Outdoor Emergency Lighting Applications.

Parameter	Value
DC-Input Voltage Source VIN	14.8 V
Rated Output Power PO	12 W
Rated Output Voltage VO	20 V
Rated Output Current IO	0.6 A
Switching Frequency fS	50 kHz

. The power switch within the circuit operates at a fixed switching frequency f_S of 50 kHz. The key components employed in the implementation of the proposed driver circuit are listed in

Table 2. Key Components Used in the Proposed DC-Powered LED Lamp Driver Circuit for Outdoor Emergency Lighting Applications.

Component	Value
Power Switches SB	IRFP460
Diodes D1, D2	MUR460
Transformer TR
Magnetized Inductor LM	129 μH
Leakage Inductance in the Primary-Side Llk1	1.71 μH
Leakage Inductance in the Secondary-Side Llk2	1.71 μH
Output Capacitors C1, C2	680 μF/50 V
PWM Control IC	UC3842

. The control strategy is based on pulse-width modulation (PWM), and the PWM controller utilized is the UC3842 integrated circuit.

The measured gate-driving signal v_GS is shown in Figure 9, clearly indicating a switching frequency of 50 kHz. Figure 10 illustrates the measured switch voltage v_DS and switch current i_DS of the proposed converter. Minor distortions and oscillations are observed in the waveform of v_DS, which can be attributed to the absence of turn-on snubber and turn-off snubber circuits. Nevertheless, the peak value of the measured switch voltage remains relatively low, not exceeding 40 V. Similarly, the peak switch current i_DS is below 3 A. These results indicate that the selected MOSFET used as the power switch in the proposed converter operates within safe voltage and current stress limits, confirming its suitability for the intended application. Figure 11 and Figure 12 present the measured currents through the leakage inductors, denoted as i_LK1 and i_LK2, respectively. The measured input voltage V_IN and input current I_IN are depicted in Figure 13, with average values of 14.96 V and 0.89 A. Similarly, the measured output voltage V_OUT and output current I_OUT, shown in Figure 14, exhibit average values of 20.05 V and 0.61 A.

The efficiency of the proposed DC-powered LED lamp driver circuit was evaluated through both simulation and experimental analysis. Circuit simulation software was employed to estimate the input power, output power, and power dissipation, yielding values of 13.6615 W, 12.5001 W, and 1.16141 W, respectively. These results correspond to an estimated power conversion efficiency of 91.50%. Complementary to the simulation, experimental measurements were carried out, indicating an input power of 13.31 W, an output power of 12.23 W, and a power dissipation of 1.08 W. Consequently, the measured power conversion efficiency was determined to be 91.88%.

A photographic demonstration of the prototype system powering the experimental LED lamp is presented in Figure 15. The image confirms successful operation, as the LED lamp is visibly illuminated using the proposed DC-powered driver circuit. Additionally, a digital oscilloscope, in conjunction with voltage and current probes, was employed to capture and analyze the electrical waveforms of the prototype during operation.

4.2. Loss Breakdown Analysis of Prototype DC-Powered LED Lamp Driver Circuit

The analysis of loss breakdown chart in the presented LED tube lamp driver are accomplished and calculated in the following.

(1) The prototype LED lamp driver circuit exhibits a measured input power of 13.31 W. At an input voltage of 14.8 V, the proposed driver achieves a measured efficiency of 91.88%. Consequently, the total power losses within the system can be determined as follows:

$$\begin{array}{l}{P}_{Loss,Total}=P_{IN}\times (100\%-\eta )\\ =13.31\mathrm{W}\times (100\%-91.88\%)=1.08\mathrm{W}\end{array}$$

(9)

(2) The equation for calculating conduction loss of the power switch S_B is given by

$$P_{conduction,S_B}={I_{DS,mean}}^2\times R_{DS,ON}$$

(10)

where the I_DS,mean is the mean level of the switch current i_DS and the R_DS,ON is the equivalent resistor when the power switch is turned on.

The average drain-source current i_DS flowing through the power switch is measured to be 0.643 A. The on-state resistance R_DS,ON of the employed power MOSFET (IRFP460) is specified as 0.27 Ω. Accordingly, the conduction loss associated with the power switch $S_B$ can be calculated as follows:

$$P_{conduction,S_B}={I_{DS,mean}}^2\times R_{DS,ON}={0.643}^2\times 0.27=0.1116\mathrm{W}$$

Additionally, the percentage of conduction loss for the power switch is given by

$${\displaystyle \frac{P_{conduction,S_B}}{P_{loss,total}}}\times 100\%={\displaystyle \frac{0.1116\mathrm{W}}{1.08\mathrm{W}}}\times 100\%=10.33\%$$

(3) The equation for calculating conduction loss of one power diode is given by

$$P_{conduction,D}=V_F\times I_{D,mean}$$

(11)

where the V_F is the forward voltage drop of the diode and the I_D,mean is the mean level of the diode current.

To evaluate the conduction loss of the power diode D₁, the measured average current I_D1 flowing through the diode is 0.2647 A, while the forward voltage drop V_f of the employed power diode (MUR460) is specified as 1.2 V. Therefore, the conduction loss associated with diode D₁ can be calculated as follows:

$$\begin{array}{l}{P}_{conduction,D_1}=V_F\times I_{D_1,mean}\\ =1.2\mathrm{V}\times 0.2647\mathrm{A}=0.3176\mathrm{W}\end{array}$$

(12)

Additionally, the percentage of conduction loss for the power diode D₁ is given by

$${\displaystyle \frac{P_{conduction,D_1}}{P_{loss,total}}}\times 100\%={\displaystyle \frac{0.3176\mathrm{W}}{1.08\mathrm{W}}}\times 100\%=29.41\%$$

To evaluate the conduction loss of the power diode D₂, the measured average current I_D2 flowing through the diode is 0.2443 A, while the forward voltage drop V_f of the employed power diode (MUR460) is specified as 1.2 V. Therefore, the conduction loss associated with diode D₂ can be calculated as follows:

$$\begin{array}{l}{P}_{conduction,D_2}=V_F\times I_{D_2,mean}\\ =1.2\mathrm{V}\times 0.2443\mathrm{A}=0.2932\mathrm{W}\end{array}$$

(13)

Additionally, the percentage of conduction loss for the power diode D₂ is given by

$${\displaystyle \frac{P_{conduction,D_2}}{P_{loss,total}}}\times 100\%={\displaystyle \frac{0.2932\mathrm{W}}{1.08\mathrm{W}}}\times 100\%=27.15\%$$

(4) Other losses of the LED lamp driver are given by

$$\begin{array}{l}{P}_{loss,others}=P_{loss,total}-P_{conduction,S_B}-P_{conduction,D_1}-P_{conduction,D_2}\\ =1.08\mathrm{W}-0.1116\mathrm{W}-0.3176\mathrm{W}-0.2932\mathrm{W}\\ =0.3576\mathrm{W}\end{array}$$

(14)

Additionally, the percentage of other losses is given by

$${\displaystyle \frac{P_{loss,others}}{P_{loss,total}}}\times 100\%={\displaystyle \frac{0.3576\mathrm{W}}{1.08\mathrm{W}}}\times 100\%=33.11\%$$

Additionally, Figure 16 shows the loss breakdown chart of the presented DC-powered LED lamp driver. The percentages of conduction losses of power switch S_B, power diode D₁, power diode D₂ and other losses are 10.33%, 29.41%, 27.15%, and 33.11%, respectively.

4.3. Stability Analysis of Prototype DC-Powered LED Lamp Driver Circuit Using a Simulation Software

The stability of a power converter can be evaluated through the use of phase margin and gain margin. A higher phase margin and gain margin generally indicate a more stable system, albeit with a slower dynamic response. Conversely, lower margins may result in a faster response but increase the risk of oscillation or instability. In this study, the stability analysis of the proposed DC-powered LED lamp driver circuit is performed using circuit simulation software. Figure 17 presents the frequency-domain analysis, specifically the bode plot, of the proposed DC-powered LED lamp driver circuit obtained from the simulation. For a power converter to exhibit satisfactory stability, it is generally recommended that the phase margin lies between 45° and 60°, and the gain margin exceeds 6 dB. Based on the data extracted from Figure 17, the phase margin and gain margin of the proposed circuit are 59.27° and 23.69 dB, respectively. These results fall within the recommended stability criteria, thereby confirming the stable operation of the proposed LED driver circuit.

5. Conclusions

This study has highlighted the significance of outdoor emergency lighting and emphasized the numerous advantages of employing LED technology in such applications, including energy efficiency, durability, and environmental sustainability. To address the demand for a reliable and efficient power supply system in emergency scenarios, a novel LED driver circuit was proposed. The proposed topology integrates a buck-boost converter with a flyback converter, forming a hybrid architecture capable of recovering leakage inductance energy from the transformer. This design not only enhances energy conversion efficiency but also reduces the number of power switches and associated components, thereby lowering overall system cost and complexity.

A prototype LED driver circuit with a DC input voltage of 14.8 V and a rated output of 12 W (20 V/0.6 A) was successfully designed and implemented to validate the proposed architecture. Experimental results confirm that the circuit operates with high efficiency and reliable performance, achieving a measured power conversion efficiency of 91.88%. These findings demonstrate the practicality and effectiveness of the proposed LED driver for outdoor emergency lighting applications and suggest its potential for broader adoption in energy-conscious emergency lighting systems.