A novel single-stage high-power-factor electronic ballast with symmetrical topology

This paper proposes a novel single-stage high-power-factor high-efficiency electronic ballast with symmetrical topology for fluorescent lamps. The circuit topology originates from the integration of two half-wave rectifiers with buck-boost power-factor-correction converters and a half-bridge series-resonant parallel-loaded inverter. A high power factor at the input line is assured by operating the buck-boost converters in discontinuous conduction mode. With symmetrical operation and carefully designed circuit parameters, zero-voltage switching on the active power switches of the inverter can be retained to achieve high circuit efficiency. The design equations are derived from the analyzed results based on fundamental approximation, and then an easy-to-use design tool is provided accordingly under considerations of filament heating and ignition. A prototype circuit designed for two T9-40W rapid-start fluorescent lamps is built and tested to verify the analytical predictions. Satisfactory performance is obtained from the experimental results.     

A resonant inverter for electronic ballast applications

Electronic ballasts must provide enough open circuit voltage to start the fluorescent lamp and current limiting while the lamp is running. Resonant inverters may be utilized in electronic ballasts because of their load-dependent characteristics. The three basic types of resonant inverters, the series-loaded, parallel-loaded, and the series-parallel-loaded, are compared using fundamental approximation techniques for their applicability in electronic ballasts operating from a low voltage source. A parallel-loaded resonant inverter operating slightly above its resonant frequency is selected because of the high voltage gains possible. Operation above the resonant frequency allows zero-voltage turn on of the semiconductor devices. Zero-voltage turn off can be achieved with the addition of lossless snubber capacitors. Experimental results from a lab prototype are used to verify the design procedure     

A high-power-factor DC-linked resonant inverter

A new approach of power-factor correction for the DC-linked high-frequency resonant inverters is proposed. The high-power-factor operation is achieved by altering the energy delivery process of the conventionally used topology. The load resonant circuit of the proposed topology draws a high-frequency pulse current directly from the AC source. This approach can be accomplished merely with an additional small capacitor as the energy buffer and a diode as the energy transfer switch. The design and experimental results for an implementation example are given to verify the theoretical analyses     

Low-cost single-stage electronic ballast based on aself-oscillating resonant inverter integrated with a buck-boost PFCcircuit

In this paper, a new solution to implement and control a single-stage electronic ballast based on the integration of a buck-boost power-factor-correction stage and a half-bridge resonant inverter is presented. The control signals are obtained from the inverter resonant current by means of a saturable transformer. Core saturation is used to control the required dead time between the control pulses of both switches. Since no special integrated circuits are required to control the ballast, the total number of components is minimized and the final cost of the ballast is reduced compared to a typical two-stage configuration. Analysis and basic design guidelines are presented in the paper, together with experimental results obtained from a laboratory prototype     

A high-power-factor electronic ballast using a flyback push-pullintegrated converter

This paper describes a high-power-factor electronic ballast for fluorescent lamps. The converter offers a high power factor and a high-frequency supply to the lamp using a single switch. In spite of its simplicity, an excellent performance concerning load and supply is achieved, ensuring a sinusoidal and in-phase supply current. High power factor is achieved by using a flyback converter operating in discontinuous conduction mode. Operating principle, design equations, component stress, and efficiency are presented. Experimental results have been obtained for one 40-W fluorescent lamp operating at 50-kHz switching frequency and 220-V line voltage     

A single-stage electronic ballast with high power factor

A single stage electronic ballast with high power factor (HPF) is proposed in this letter. The single-phase boost-type rectifier provides HPF. A saturable transformer constituting the self-oscillating drive limits the lamp current and dominates the switching frequency of the ballast. Experimental results obtained on a 40 W fluorescent lamp are discussed     

High power factor self-power-controlling electronic ballast usingcurrent source type push-pull resonant inverter

A new simple low cost high power factor correction circuit for electronic ballast employing a current source type push-pull resonant inverter is proposed. The proposed circuit provides high power factor, low current harmonic distortion, self-power-controlling operation for load variations and cost-effectiveness     

Improved start-up scenario for single-stage electronic ballast

This paper presents improved start-up scenario for single-stage electronic ballast derived with a synchronous switch technique (SST). Based on the SST, the derivation of a single-stage inverter (SSI) used for realizing the ballast is then addressed. The SSI can achieve both high power factor and ballasting function. During lamp start-up transition, power imbalance may exist between the power factor correction semi-stage and the ballast semi-stage, and filament preheating is an important issue. Power imbalance usually results in a high DC-link voltage which, in turn, imposes high stress on the switching devices. Investigation of the ballast operation is conducted, from which control strategies for reducing component stresses and hot resistance detection circuits for minimizing electrode sputtering are therefore proposed. Hardware measurements have verified that on-off tests are higher than 18,000 times without significant sputtering     

A novel single-stage constant-wattage high-power-factor electronicballast

A novel single-stage high-power-factor electronic ballast is presented in this paper. The ballast is obtained from the integration of a buck-boost converter and a half-bridge LC resonant inverter. The ballast features lamp power regulation against line voltage fluctuations together with high power factor and dimming capability. The steady-state analysis of the ballast is performed and a low-frequency model of the input stage is derived. A design example, including closed-loop circuitry, is also presented. Finally, some experimental results from a laboratory prototype are shown     

A novel single-stage push-pull electronic ballast with high inputpower factor

A novel single-stage push-pull electronic ballast with high input power factor is presented in this paper. The proposed electronic ballast combines the front-end power-factor corrector and push-pull converter into a single-stage power converter. Compared to the single-stage class-D electronic ballast, the proposed circuit does not require an isolated driver. The control of the circuit is easier and the cost less. The circuit of the ballast is analyzed and the design guidelines are listed. The experimental results verify the theoretical derivation     

A near-zero current-switching series resonant inverter using GTOs

A novel implementation of fast gate-turn-off thyristors (GTOs) for a series resonant power converter operating above 10 kHz and an output power rating of 10 kW or greater is presented. A zero current switching gating strategy that eliminates the need for large negative gate drive circuits is presented. This permits the operation of the converter at a near-unity load power factor independent of the operating frequency. Consequently, for a given output power, the installed kVA capacity of the converter is minimized, and the system simplicity is maintained. A simplified analysis and component ratings for the GTO-based converter are presented. All the results are verified experimentally     

Design and analysis of an IC-less self-oscillating series resonant inverter for dimmable electronic ballasts

This paper presents a low-cost solution of converting the popularly adopted nondimmable electronic ballast circuit for fluorescent lamps with self-oscillating series resonant inverter into a dimmable one. The dimming function is achieved by increasing the switching frequency of the inverter from the natural frequency of the resonant tank, so that less energy is coupled to the lamp. Control of the switching frequency is based on deriving an adjustable dc current source from the resonant inductor in the resonant tank to control the operating point of the saturable transformers for driving the switches in the inverter. The overall implementation does not require any integrated circuit. A 17-W prototype has been built and studied. Theoretical predictions have been verified with experimental results. The lamp can be dimmed down to 10% of the full power.     

A new power-factor-correction circuit for electronic ballasts withseries-load resonant inverter

This paper presents an efficient, small-sized and cost-effective power factor correction (PFC) scheme for high-frequency series-resonant electronic ballasts. The proposed scheme introduces additional small energy tanks processing partial power and thus can perform the function of input current shaping. Theoretical and experimental results prove that the electronic ballast incorporating with only few reactive components can achieve nearly unity power factor and very low harmonic distortion     

A novel single-stage full-bridge buck-boost inverter

A novel single-stage full-bridge series-resonant buck-boost inverter (FB-SRBBI) is proposed in this paper. The proposed inverter only includes a full-bridge topology and a LC resonant tank without auxiliary switches. The output voltage of the proposed inverter can be larger or lower than the dc input voltage, depending on the instantaneous duty-cycle. This property is not found in the classical voltage source inverter, which produces an ac output instantaneous voltage always lower than the dc input voltage. The proposed inverter circuit topology provides the main switch for turn-on at ZCS by a resonant tank. The nonlinear control strategy is designed against the input dc perturbation and achieves well dynamic regulation. An average approach is employed to analyze the system. A design example of 500 W dc/ac inverter is examined to assess the inverter performance and it provides high power efficiency above 90% under the rated power.     

Analysis of the self-oscillating series resonant inverter forelectronic ballasts

In this paper, we examine the self-oscillating series resonant inverter for electronic ballast applications from a system point of view. By considering the discharge lamp as a linear resistor in steady state, we derive a time-domain closed-form expression of the circuit state variables. Importantly, we observe that the self-oscillating series resonant inverter with lamp loads can be naturally modeled as a relay system. Based on this formulation, the self-oscillating frequencies of the inverter for variable lamp impedance conditions are found via the Tsypkin's locus. The stability of the self-oscillating frequencies is determined in a sampled-data system framework     

A novel three-phase single-stage distributed power inverter

In this paper, a novel three-phase, DC/AC converter suitable for distributed power applications is proposed. The system consists of three DC/DC boost converters with a common point and operating as a three-phase inverter with intrinsic step-up capability. The converter obtained can invert, amplify and, where possible, regenerate bidirectional power sources such as fuel-cells, small gas turbines, and photovoltaic arrays. There are two main advantages to the system: the use of only six insulated gate bipolar transistors and small passive elements, and the fact that it does not need reverse voltage blocking capability. Simulation and experimental results show the effectiveness of the proposed system during both steady-state and dynamic operations.     

A cost-effective single-stage inverter with maximum power point tracking

Renewable energy, such as solar energy, is desirable for power generation due to their unlimited existence and environmental friendly nature. However, the high initial investment impedes its wide commercialization. This paper proposes a cost-effective single-stage inverter with maximum power point tracking (MPPT) in combination with one-cycle control (OCC) for photovoltaic power generation. This control scheme is based on the output current-adjusting feature of OCC. The output current of the inverter can be adjusted according to the voltage of the photovoltaic (PV) array so as to extract the maximum power from it. In the mean time, OCC guarantees that the output current is proportional and in phase with the grid voltage. All these are accomplished in one power stage and a simple control circuit. No detection and calculation of power are needed. Compared with previously proposed approaches, this method is much more efficient and cost-effective and yet exhibits excellent performance. The principle is explained qualitatively and extensive experiments have been carried out to verify the proposed method.     

Analysis, design, and optimization of the LCC resonant inverter asa high-intensity discharge lamp ballast

A complete study of the clamped-mode (CM) series-parallel (LCC) resonant inverter together with some of the control-to-output characteristics are presented in this paper. Also, a new control method for the CM LCC resonant inverter is introduced. With this method, the inverter is forced to operate with optimum commutations and without handling reactive energy, thus minimizing both switching and conduction losses. The corresponding design procedure is illustrated with a design example. Finally, some experimental results obtained from a prototype at the laboratory are also shown to validate the analysis and evaluate the proposed control method     

Analysis and design of a high power factor, single-stage electronic ballast for high-intensity discharge lamps

This paper proposes a single-stage electronic ballast for high-intensity discharge lamps. The ballast consists of the integration of a boost converter in discontinuous conduction mode (DCM) and a full-bridge LCC resonant inverter. The boost semi-stage working in DCM functions as a power factor corrector and the inverter semi-stage operated above resonance is employed to drive the lamp. The sine-wave approximation is used to design the inverter at steady-state. The proposed electronic ballast can save a controller, reduce size and possibly increase system reliability compared to conventional two-stage system. The proposed ballast is analyzed, simulated and experimentally verified with a 125 W HPS lamp.     

Design optimization of the LCC parallel-series inverter with resonant current mode controlfor 250-W HPS lamp ballast

In this paper, the optimum design of the LCC parallel-series inverter with resonant current mode control for 250-W high pressure sodium vapor lamps is presented. With this control method the inverter does not have any reactive energy, and both switching and conduction losses are minimized. Also, the design proposed performs a precise natural power control without exceeding the maximum power recommended by the lamp manufacturer without additional lamp power control circuitry. Since it is desirable implementing a low-cost and efficient power factor correction (PFC) stage for meeting the standard IEC 61000-3-2 Class C about low-frequency harmonic content injected in the line for lighting applications, a low-cost PFC buck pre-regulator is proposed. The ignition process is optimized because no additional circuitry is necessary for the lamp ignition providing low ignition inverter current. The design proposed leads to an important size and cost reduction, avoiding the additional circuitry used in the classic designs. Simulations and experimental results have validated the design proposed in this paper.