Flyback Converter Operating Research Articles

A Novel High-Power-Factor Electrolytic-Capacitorless LED Driver Based on Ripple Port

In this article, a novel high-power-factor electrolytic-capacitorless light-emitting diode (LED) driver based on the use of a ripple port is presented. The ripple port consists of adding an extra power processing circuit at the output of the converter that injects energy to compensate for the output current and voltage ripples. In this work, the main converter is built by using a flyback converter operating in the discontinuous conduction mode (DCM). The ripple port is implemented by adding an extra winding to the flyback coupled inductors, together with an extra switch, a capacitor, and an inductor. The additional switch is used to inject energy to the output in the time intervals, in which the flyback output current is low, thus reducing the output current ripple. The proposed converter is analyzed in detail, and a design methodology is proposed. A design example for a 27-V/1-A LED lamp is presented. Simulation and laboratory experiments have also been carried out. It is demonstrated that the proposed solution can achieve a reduction on the output current ripple of around 65% compared to the solution without ripple port for the same total capacitance and maintain a high power factor of 0.994.

Modeling and Controller Design of Flyback Converter Operating in DCM for LED Constant Current Drive

In power converter, the system model has a significant meaning of the design of the controller and the dynamic characteristics. In this paper, the switching network average method is used to set up the small signal model of flyback circuit, which is operating in discontinuous current mode(DCM). A controller with single zero and single pole is designed based on the small signal model which is set up in this paper. Moreover, the analysis of system stability and dynamic response is proposed. Finally, the system is simulated and verified by a flyback LED constant current drive circuit (220AC input, 0.7A/16W output).

Voltage‐extrapolative charge balance controller with charge compensation for flyback converter operating in DCM

This study presents a voltage-extrapolative charge balance (VECB) controller with charge compensation for flyback converter operating in discontinuous conduction mode (DCM). Compared with conventional charge balance controller, the VECB controller benefits from voltage extrapolation, which improves the transient response to load disturbance. Based on the output voltage differential value, a voltage extrapolator calculates the output voltage after two switching cycles under the influence of discharge. Furthermore, the extrapolated voltage is used to calculate the reference charge for the next switching cycle. The VECB controller eliminates the lag in calculating the reference charge, which improves the transient response to load disturbance. Closed-loop small signal models under VECB and conventional charge balance controls are derived and compared to prove the improvement. Furthermore, charge damping and its influence to the output voltage are intensely studied. To minimise the influence, a constant factor is adopted to carry out charge compensation, which is proved to be adequate. Finally, the effectiveness of VECB controller is verified on a flyback converter prototype.

Adaptive Boundary Control Using Natural Switching Surfaces for Flyback Converters Operating in the Boundary Conduction Mode with Parameter Uncertainties

The derivation and implementation of the natural switching surfaces (NSS) considering certain parametric uncertainties for a flyback converter operating in the boundary conduction mode is the main focus of this paper. The NSS with nominal parameters presents many benefits for the control of nonlinear systems; for example, fast transient response under load-changing conditions. However, the performance worsens considerably when the converter actual parameters are different from the ones used in the design process. Therefore, a novel control strategy for NSS considering the effects of parameter uncertainties is proposed. This control law can estimate and adapt the control trajectories in a minimum number of switching cycles to obtain excellent performances even under extreme parameter uncertainties. The analytical derivation of the proposed adaptive switching surfaces is presented together with simulations and experimental results showing adequate performance under different tests, including comparisons with a standard PI controller.

An Optimized Sensorless Charge Balance Controller Based on a Damped Current Model for Flyback Converter Operating in DCM

This paper presents an Optimized Sensorless Charge Balance (OSCB) controller based on a damped current model for flyback converter operating in Discontinuous Conduction Mode (DCM). By solving total differential equations of non-ideal transformer currents, the damped current model is derived with consideration of parasitics, leakage inductance of transformer, and the Resistor-Capacitor-Diode (RCD) snubber circuit. Based on the proposed model, current observation and control algorithms of the Sensorless Charge Balance (SCB) controller are optimized, which forms the OSCB control strategy. The average current damping is considered in the equivalent discrete-time small signal model. Furthermore, frequency analyses show that OSCB controller achieves higher closed-loop bandwidth and lower overshoot than a SCB controller, which indicates an improved transient performance. Finally, both OSCB and conventional SCB controllers are experimentally evaluated on a flyback converter prototype.

Primary Side Control For Flyback Converter Operating in DCM and CCM

Primary side regulation (PSR) technology has the characteristics of lower cost and standby power losses. However, there is no algorithm suitable for discontinuous conduction mode (DCM) and continuous conduction mode (CCM) operations of primary side control for flyback converter because of the difficulty in estimating the output voltage correctly. In this paper, a PSR control algorithm suitable for DCM/CCM flyback converter is proposed and implemented with digital micro controller. The voltage drop on the secondary winding and output diode at CCM operation is compensated by sensing the secondary side current at the instant when primary side switch is being turned-on. The secondary side current is zero at the voltage sensing instant and equal to the current at the instant when primary side switch is being turned-on as flyback operated at DCM. In addition, the proposed algorithm can be used to regulate either the output voltage or current very well. An experimental prototype with 150 W rated power is built to verify the feasibility of the proposed control. Experimental results show that the output voltage can be controlled with error less than 0.25%, and the output current error is less than 5%. The conversion efficiency is up to 92.8%.

Exponentially Stable Lyapunov-Function-Based Controller for a Flyback CCM Converter

In this paper, we propose a Lyapunov-function-based controller for the flyback converter operating in the continuous conduction mode (CCM). The controller consists of a duty-ratio feedforward control unit and a Lyapunov-function-based feedback control unit. The duty-ratio feedforward signal is used to reduce the burden from the Lyapunov feedback controller. The control system guarantees global exponential stability of the closed-loop system and, hence, offers fast transient response under large-signal perturbations. In constructing the controller, we use the average model of the flyback CCM converter taking the parasitic components into account. Numerical simulations confirmed its superior performance, and experimental tests validated the proposed control approach.

LED Driver Based on Input Current Shaper Without Electrolytic Capacitor

This paper presents a high-power-factor light-emitting diode (LED) driver implemented by using an input current shaper technique. A flyback converter operating in DCM is placed between the main rectifier and dc bus, in order to increase the conduction angle of the rectifier diodes and to decrease the current harmonics injected to the mains. A buck converter performs the LED power control stage, which is integrated with the flyback by sharing the same active switch, thus presenting reduced component count. The use of a flyback converter operating as a loss-free resistor provides reduced power processing, increasing the converter's overall efficiency. The two-stage configuration allows bus capacitor reduction, owing to the effect of low frequency filtering provided by the second stage. In this way, electrolytic capacitors can be avoided, thus increasing reliability of the LED driver. An analysis of the effects of the bus voltage ripple caused by the capacitance reduction is performed. The driver also presents dimming capability. Analysis and design example of the proposed converter are presented. Experimental results of the proposed converter supplying an LED luminaire of $\text{50}\, \text{V}/\text{2.1}$ A LEDs are shown. The prototype presented high power factor, ${\text{PF}} = \text{0.97}$ , harmonic distortion of input current satisfying the IEC 61000-3-2 requirements, THD = 22.3%, and high efficiency, $\eta = \text{91.1}\% $ .

Input‐series and output‐series connected modular single‐switch flyback converter operating in the discontinuous conduction mode

This study proposes a modular isolated dc–dc converter, based on the input-series and output-series connection of flyback converters operating in discontinuous conduction mode, as an alternative to provide higher voltage capability for medium-voltage applications (1–10 kV), from low-voltage semiconductors and passive components. The proposed architecture allows the modular system to operate with a simplified control scheme thanks to an intrinsic voltage-balancing mechanism. The voltage-balancing mechanism is investigated by theoretical analysis, both for steady-state and dynamic operations. A small-signal ac modelling of the architecture is developed to design the total output-voltage controller. To experimentally verify the proposed technique, a laboratory prototype system with three single-switch flyback converters, with 3 kW output power, 600 V dc input and output voltages, and 40 kHz of switching frequency was built.

Comparative Study between PID-controller and Fuzzy Logic Controller of a Novel Flyback Converter

In this paper, proportional–integral–derivative (PID)-based Fly-back converter and fuzzy-type controllers are compared for 220V A.C input and 440 D.C output flyback converter operating in discontinuous conduction mode (DCM).Design of fuzzy controllers is based on heuristic knowledge of converter behavior, and tuning requires some expertise to minimize unproductive trial and error. The design of PID control is based on the frequency response of the converter. For the flyback converter, the performance of the fuzzy controller was superior in some respects to that of the PID controllers. The fuzzy controller was able to achieve faster transient response in most tests, had a more stable steady-state response, and was more robust under some operating conditions. MATLAB/Simulink software is used for implementation and simulation results show the performance variations.

Integrated Off-Line Ballast for High Brightness LEDs with Dimming Capability

This paper presents an off-line integrated full ballast to supply a 35W assembly of Power LEDs. The proposed solution integrates an input PFC stage (a flyback converter operating in DCM) and a DC-DC output converter (a buck converter) into a single switch power stage, operating with peak current control. As it will be shown, this control scheme maintains the current through the load constant, regardless of the instantaneous value of the DC link voltage. This issue allows the use of a small capacitor for the DC link, which enhances the overall system reliability. The complete ballast has full dimming capability, and all the analysis and design steps are presented, thus ensuring the fulfilling of the existing regulations. The novelty of the final solution comes from the simplicity and robustness of the control scheme in an integrated compact single-switch power stage. A final prototype of the ballast has been built and tested, and experimental results are shown in the last part of the paper. Finally, conclusions and future developments are shown.

The Output Characteristics of Transcranial Magnetic Stimulation with Voltage Variable Capacitor-Charging System

In this study, a Magnetic stimulation Pulse Train control technique is introduced and applied to Flyback converter operating in discontinuous conduction mode. In contrast to the conventional pulse width modulation control scheme, the principal idea of a Magnetic stimulation Pulse Train is to achieve output voltage regulation using high and low power pulses. The proposed technique is applicable to any converter operating in discontinuous conduction. However, this work mainly focuses on Flyback topology. In this paper, the main mathematical concept of the new control algorithm is introduced and simulations as well as experimental results are presented.

Winding losses caused by harmonics in high-frequency flyback transformers for pulse-width modulated dc–dc converters in discontinuous conduction mode

High-frequency transformers used in pulse-width modulated (PWM) converters conduct periodic non-sinusoidal currents, which give rise to additional winding losses because of harmonics. This study presents expressions for winding power losses in a two-winding transformer subject to non-sinusoidal excitation operated in discontinuous conduction mode (DCM). Dowell's equation is used to determine the winding resistances because of eddy currents as a function of frequency. Both skin and proximity effects are taken into account. Fourier series of the primary and secondary triangular current waveforms in isolated dc–dc power converters and the primary and secondary winding resistances are used to determine the primary and secondary winding power losses at various harmonics, respectively. The harmonic winding loss factors FRph and FRsh are introduced. The theory is illustrated by the case study of the two-winding flyback converter operating in DCM. Plots of the winding power losses are given as functions of the output power and the dc input voltage.

Pulse Regulation Control Technique for Flyback Converter

Pulse regulation, a fixed frequency control technique, is introduced and applied to flyback converter operating in discontinuous conduction mode (DCM). The control parameters are designed in a way that the converter operates as close as possible to the critical conduction mode. In contrast to the conventional pulsewidth modulation control scheme, the principal idea of pulse regulation is to achieve output voltage regulation using high and low-power pulses. Pulse regulation is simple, cost effective, and enjoys a fast dynamic response. The proposed technique is applicable to any converter operating in DCM. However, this work mainly focuses on flyback topology. In this paper, the main mathematical concept of the new control algorithm is introduced and simulations as well as experimental results are presented.

Low-cost electronic ballast to supply MH lamps based on flyback converter

A novel electronic ballast to supply metal-halide lamps is presented. The circuit is based on a flyback converter operating in discontinuous-conduction-mode. To avoid acoustic resonances, the lamp is supplied by a low-frequency square-waveform current, using a half-bridge as inverter. A design example and experimental results are presented in order to validate the proposed topology.

Pulse Train Control Technique for Flyback Converter

Pulse Train/spl trade/ control technique is introduced and applied to flyback converter operating in discontinuous conduction mode (DCM). In contrast to the conventional pulse width modulation (PWM) control scheme, the principal idea of Pulse Train is to achieve output voltage regulation using high and low power pulses. The proposed technique is applicable to any converter operating in DCM. However, this work mainly focuses on flyback topology. In this paper, the main mathematical concept of the new control algorithm is introduced and simulations as well as experimental results are presented.

A high-power-factor electronic ballast using a flyback push-pull integrated 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.