Controlled Switching Converters Research Articles

An Effective Charger for Plug-In Hybrid Electric Vehicles (PHEV) with an Enhanced PFC Rectifier and ZVS-ZCS DC/DC High-Frequency Converter

A plug-in hybrid electric vehicles (PHEV) charger adapter consists of an AC/DC power factor correction (PFC) circuit accompanied by a full-bridge isolated DC/DC converter. This paper introduces an efficient two-stage charger topology with an improved PFC rectifier as front-end and a high-frequency zero voltage switching (ZVS). Current switching (ZCS) DC/DC converter is the second part. The front-end converter is chosen as bridgeless interleaved (BLIL) boost converter, as it provides the advantages like lessened input current ripple, capacitor voltage ripple, and electromagnetic interference. Resettable integrator (RI) control technique is employed for PFC and DC voltage regulation. The controller achieves nonlinear switching converter control and makes it more resilient with the faster transient response and input noise rejection. The second stage incorporates a resonant circuit, which helps in achieving ZVS/ZCS for inverter switches and rectifier diodes. PI controller with phase shift modulator is used for second-stage converter. It improves the overall efficacy of the charger by lowering the switching losses, lowering the voltage stress on the power semiconductor devices, and reversing recovery losses of the diodes. The simulations and experimental results infer that the overall charging efficiency increases to 96.5%, which is 3% higher than the conventional two-stage approach using the interleaved converter.

Lyapunov function‐based improved switching command for a boost converter with an inductor–capacitor input filter

This study presents a control method for DC–DC switching power converters to avoid the instability caused by the interaction between a tightly controlled switching converter and an input low-pass filter. The proposed method is based on the Lyapunov stability criterion. A non-linearised model is established, and the instantaneous quantities of the state variables are considered. The switching command is formulated by calculating the stability of the system. The inductor current and voltage across the filter capacitor, along with the state variables in the switching converter, follow the corresponding references. A boost converter is considered to demonstrate the associated effectiveness. The results of several simulations and experiments pertaining to the start-up, tracking, and regulation stages validate the proposed control approach. Moreover, the robustness of the approach against variations in the parameters of the controlled system is examined experimentally. To demonstrate the superiority of the proposed method, the method is compared with the proportional–integral, fuzzy, and flatness-based controllers.

Pulse Coding Controlled Switching Converters with Notch Frequency Generation in Noise Spectrum

This paper proposes a new technology about generating notch characteristics in noise spectrum of DC-DC switching converters for the communication devices. There are very few reports about the pulse coding controlled switching converter, though it is sometimes used in digital-to-analog converter (DAC) field, to our knowledge. We have investigated the pulse coding technology to switching converters to generate automatically the notch characteristics in the noise spectrum. The notch frequency Fn in the spectrum of the switching pulses is created by two coding pulses to control the main power switch. The clock and coding pulses are automatically generated from the input frequency Fin to create the notch frequency Fn=Fin. In addition, the notch frequency is experimentally confirmed with the prototype circuit.

Pulse Coding Controlled Switching Converter with Notch Generation and its Conversion Voltage Ratio Analysis

This paper proposes an EMI spread spectrum technology with automatically setting the notch frequency using the pulse coding controlled method of the DC-DC switching converter. In the automatic notch generation method, by usage of the input frequency Fin, the clock frequency Fckand the coding pulses PH, PL are generated automatically using the equation (see formula in the paper). Here the conversion voltage ratio is given by (see formula in the paper) . If shifts, the balance of the inductor current is shifted and then the output voltage ripple is influenced. Moreover, as the power supply IC, it is necessary to automatically detect or set the conditions for Vin and Vout, and hence we also provide discussion about the conversion voltage ratio Do in many situations.

Pulse Coding Controlled Switching Converter that Generates Notch Frequency to Suit Noise Spectrum

This paper proposes a noise reduction technology for a specific frequency band that uses the pulse coding controlled method to automatically set the notch frequency in DC-DC switching converters of communication equipment. For reducing the power levels at the frequency and its harmonics in the switching converter, we often use a frequency-modulated clock. This paper investigates a technology that prevents modulated clock frequency noise from spreading into protected frequency bands; this proposed noise reduction technology does not distribute the switching noise into some specified frequency bands. The notch in the spectrum of the switching pulses is created by the Pulse Width Coding (PWC) method. In communication devices, the noise in the receiving signal band must be as small as possible. The notch frequency is automatically set to the frequency of the received signal by adjusting the clock frequency using the equation Fn = (P+0.5)Fck. Here Fn is the notch frequency, Fck is the clock frequency, and P is a positive integer that determines the noise spectrum location. Therefore, simply be setting the notch frequency to the received signal frequency can suppress the noise present. We confirm with simulations that the proposed technique is effective for noise reduction and notch generation. Also we implement a method of automatic switching between two receiving channels. The conversion voltage ratio in the pulse width coding method switching converter is analyzed and full automatic notch frequency generation is realized. Experiments on a prototype circuit confirm notch frequency generation.

Research on Dual-Carrier Pulse-Train-Controlled Buck Converter

In order to solve the low-frequency oscillation of pulse-train- (PT-) controlled switching converter operating in a continuous conduction mode (CCM), a dual-carrier pulse-train (DCPT) control technique is proposed in this paper. With the CCM buck converter as an example, the operational principle, pulse control law, and output voltage ripple of the DCPT-controlled converter are studied. The experimental results are provided to verify the theoretical analysis and simulation results. Compared with the PT-controlled converter, the DCPT-controlled CCM buck converter enjoys much better operating characteristics and smaller output voltage ripple.

Dynamic Reactive Power Compensation and Harmonic Suppression of Optical Storage Microgrid Control in Natural Coordinates

In order to solve the influence of load fluctuation on the power quality of the grid when the distributed photovoltaic power generation system is connected to the grid side, and to reduce the complexity of the control system, this paper proposes the grid-connected control of the microgrid with reactive power compensation and harmonic suppression in natural coordinates. This strategy maintains the DC bus voltage stability in a battery capacity state switching converter control method. Two kinds of grid-connected inverter power control strategies with reactive power compensation are designed for different working conditions, which realizes independent control of active and reactive power of grid-connected inverters, eliminating coordinate transformation and grid phase detection. The experimental results show that the proposed control strategy can achieve the smooth and efficient flow of the optical storage microgrid system, achieve the purpose of reactive power compensation, and has a good dynamic response.

Analysis of Pulse Train Controlled PCCM Boost Converter With Low Frequency Oscillation Suppression

For pulse train (PT) controlled switching converter, when it operates in continuous conduction mode (CCM) and discontinuous conduction mode (DCM), there exist disadvantages of low frequency oscillation and narrow load range, respectively. To avoid these disadvantages of PT controlled switching converter in CCM and DCM, a PT controlled boost converter operating in pseudo continuous conduction mode (PCCM) is taken as the research object in this paper, its working principle has been analyzed in detail. Based on the analysis of output voltage ripple during one switching cycle, the combination of high- and low-power control pulses in a repetition cycle is analyzed and the expression of output voltage ripple is derived for different load conditions. Finally, simulation and experiment are performed to verify the correctness of the control pulse combinations and the output voltage ripple analysis. Results show that compared with DCM and CCM boost converters, the PT controlled PCCM boost converter not only has wider load range, but also can suppress low frequency oscillation.

The Start-up Dynamic Analysis and One Cycle Control-PD Control Combined Strategy for Primary-Side Controlled Wireless Power Transfer System

This paper proposes a novel dynamic analysis and a switching converter control strategy for primary-side voltage controlled wireless power transfer (WPT) system. First, the modeling of the high-order double-sided LCC resonant converter is carried out. By dividing the resonant circuit into three equivalent parts and analyzing their transfer functions, respectively, the approximated boundary of the start-up transient time of the WPT stage is solved analytically. Furthermore, in order to ensure the swiftness of the transient response of the WPT system, a novel control strategy combining one cycle control and proportional differential control (OCC-PD) is proposed. By using switching flow-graph technique, the transfer functions of the buck converter applying the OCC, proportional integral differential, and OCC-PD control are obtained. The superiorities of the OCC-PD are proved through the analytic expressions of dynamic characteristic parameters. The input impedance of the WPT stage cascaded to the buck converter is also derived to evaluate the performance of the whole WPT system. Finally, simulations and experiments are carried out through a 6.6-kW two-stage primary-controlled WPT prototype. The results are in accordance with the theoretical analysis and validate the superiorities of the proposed OCC-PD strategy in the aspects of the transient response and the robustness.

A Lyapunov Function for Switching Command of a DC–DC Power Converter With an LC Input Filter

This paper describes a method to control a dc-dc switching power converter with an LC input filter working under continuous conduction mode. It is known that the interaction between the low-pass filter and the tightly controlled switching converter occurs, and it might lead to an instability operation. The idea of this method relies on the Lyapunov stability criterion. The switching command of this control is defined by the manner of pre-evaluating the stability of the controlled system. All state variables are controlled in the same time. Therefore, the responses of this controlled system are fast while guaranteeing a stable operation. The proposed control is applied to a boost converter to demonstrate the implementation and its performance. The simulation and experimental results validate the proposed control approach.

Can V 2 control be applied to boost converter?

It is 18 years since the V2 control was proposed in 1996. Many publications have shown that the V2 controlled switching converter exhibits an ultra-fast load transient response. Recently, it has been reported that the conventional V2 control is inherently a peak V2 control, based on which V2 control can be classified as peak V2 and valley V2 controls. However, till now the switching converter with V2 control is almost a buck converter. This leads to the investigation of whether the V2 control can be applied to a boost converter.

High output‐regulation accuracy and fast transient response of dual constant on‐time controlled switching converter

Compared with a pulse-width modulated voltage-mode controlled switching converter, a constant on-time (COT) controlled switching converter has extensive industry application due to its fast transient response. However, the conventional COT controlled switching converter has poor output-regulation accuracy. A new control method that provides both fast transient response and high output-regulation accuracy for switching converters, called dual COT control, is proposed. The analysis results are verified by circuit simulation.

Adaptive high‐bandwidth digitally controlled buck converter with improved line and load transient response

Digitally controlled switching converter suffers from bandwidth limitation because of the additional phase delay in the digital feedback control loop. To overcome the bandwidth limitation without using a high sampling rate, this study presents an adaptive third-order digital controller for regulating a voltage-mode buck converter with a modest 2× oversampling ratio. The phase lag because of the analogue-to-digital converter (ADC) conversion time delay is virtually compensated by providing an early estimation of the error voltage for the next sampling time instant, enabling a higher unity-gain bandwidth without compromising stability. An additional pair of low-frequency pole and zero in the third-order controller increases the low-frequency gain, resulting in faster settling time and smaller output voltage deviation during line transient. Both simulation and experimental results demonstrate that the proposed adaptive third-order controller reduces the settling time by 50% in response to a 1 V line transient and 30% in response to a 600 mA load transient, compared to the baseline static second-order controller. The fastest settling time is measured to be about 11.70 μs, surpassing the transient performance of conventional digital controllers and approaching that of the state-of-the-art analogue-based controllers.

Valley current mode pulse train control switching converter and its energy model analysis

Pulse train (PT) control technique is a novel discrete control technique for switching converter operating in discontinuous conduction mode (DCM). When the inductive energy storage is not zero, the low-frequency oscillation phenomenon may occur in PT controlled switching converters operating in continuous conduction mode (CCM). The low-frequency oscillation phenomenon will seriously affect the steady and transient performances of switching converters. In order to solve this problem, valley current mode pulse train (VCM-PT) control technique, which extends the application range from DCM to CCM, is proposed in this paper. The energy model of VCM-PT controlled switching converter is derived and compared with the energy model of PT controlled switching converter. Result indicates that the VCM-PT controlled CCM switching converter has the same energy transfer mode as the traditional PT controlled DCM switching converter and can eliminate fundamentally the low-frequency oscillation phenomenon.

Self-similarity and frequency-mixing phenomena analysis of multi-frequency controlled switching converter

Based on the operation principle and state equations of multi-frequency (MF) controlled switching converter, the discrete iterative map model is established, the corresponding characteristics equation and Lyapunov exponent of MF controlled switching converter operating in discontinuous conduction mode are derived. According to the discrete iterative map model, its bifurcation behaviors are investigated. It is found that the border-collision bifurcation and the multi-period behaviors occur in converter, when the circuit parameters are varied. When the voltage error boundary is too large, the converter behaves as self-similarity phenomenon, and when the voltage error boundary is too small, the converter behaves as frequency-mixing phenomenon. The converter stability is investigated by Lyapunov exponent, which validates the correctness of bifurcation analysis. Time-domain waveforms and phase portraits of converter with the load varied, are analyzed by circuit simulation, which validates the validity of discrete iterative map model and the correctness of theoretical analysis. Finally, simulation results in this paper are verified by experimental results.

Multi-period analysis of current-mode pulse-train controlled continuous conduction mode converter

Pulse train (PT) control technique is a discrete, nonlinear control technique for switching converter which benefits from simple design and ultra fast transient response. As an output-power-control-based control technique, a low-frequency oscillation phenomenon occurs in voltage-mode PT controlled switching converter operating in continuous conduction mode. This phenomenon will seriously affect the steady and transient performances of switching converter. In this paper, a current-mode PT (CM-PT) controlled switching converter is studied. The normally working region is studied and the parameter conditions are estimated. Targeting the problem of CM-PT control technique, a modified control technique is proposed.

Dynamical modeling and multi-period behavior analysis of voltage-mode bi-frequency controlled switching converter

A dynamical model is proposed and the corresponding characteristic aligns are derived for voltage-mode bi-frequency controlled switching converter operating in discontinuous conduction mode. According to the dynamical model, the border-collision bifurcation and multi-period behaviors, such as period-2, period-3, period-4, and so on, are studied using bifurcation diagrams as the circuit parameters are varied. It is found that the converter behaves along the bifurcation route of period-1, multi-period, and period-1, and the change of period state is induced by border-collision bifurcation. Based on the characteristic equation, the converter stability is investigated by the Lyapunov exponent. It is shown that Lyapunov exponent is always smaller than zero with the variation of circuit parameters and the converter operates in stable period state all the time. Also, it is validated that period-3 behavior of voltage-mode bi-frequency controlled switching converter does not predicate its inevitable chaos. Time-domain waveforms, phase portraits, and frequency spectra of voltage-mode bi-frequency controlled switching converter are analyzed by circuit simulation, which validates the feasibility of dynamical model and the correctness of theoretical analysis. Simulation results are verified by experiments in this paper.

Study on control pulse combination of pulse train controlled switching converter and its multi-periodicity analysis

Pulse train control technique is realized through the output voltage regulation of switching dc-dc converter by adjusting the control pulse combination of high-power and low-power control pulses in a control pulse repetition cycle. Once the circuit parameters are determined, the control pulse combination is fixed. The control pulse combination directly affects the steady-state performances of pulse train (PT) controller. In this paper, the control pulse combination of PT control technique is studied by using the continued fraction technique. A one-dimensional normal form of discrete-time map of PT controlled buck converter operating in discontinuous conduction mode is also established in which the steady state performances, such as parameter evaluation of multi-periodicities and output voltage ripple of PT controlled DCM buck converter, are analyzed. The simulation result, experimental result, and the results in the literature are in accordance with the theoretical analysis. This investigation is helpful to obtain a deeper understanding of PT control technique.

Dynamics of current controlled switching converters under wide circuit parameter variation

With current-controlled buck-boost converter used as an example, through a detailed description of the switch state of the switching converter under wide circuit parameter variation, such as input voltage and load resistance variation, two inductor current borders in the current controlled switching converter are derived and an accurate discrete-time model is established. The validation of the discrete-time model is verified by a piecewise-linear model. Based on the discrete-time model, the complex dynamical behaviors existing in switching converter, such as period-double bifurcation, border-collision bifurcation, robust chaos and intermittent chaos, etc., are revealed. By formulating the Jacobian, the maximum Lyapunov exponent and the movement trajectories of eigvalues with the variations of circuit parameters are obtained. By utilizing the parameter-space maps, the operation-state regions corresponding to circuit parameter regions are estimated. Finally, an experimental setup is implemented, the corresponding observation results are consistent with those of theory analyses. In this paper the dynamics theory in switching converters is investigated systematically; the analysis methods and research results are helpful for designing and controlling switching converters.

Analysis of symmetrical dynamic phenomenon of peak and valley current-mode controlled switching DC-DC converters

Peak current and valley current controlled switching DC-DC converters show symmetrical dynamic phenomenon within a wide circuit parameter range. The unified discrete iterative map model of peak current and valley current controlled buck, boost, and buck-boost converters is established, and the unified piecewise smooth iterative map and their corresponding characteristic equations are also derived. The forward and inverse bifurcation diagrams and Lyapunov exponent spectrums with duty ratio as parameter are obtained by numerical simulation. The research results indicate that the bifurcation diagrams and Lyapunov exponent of peak and valley current-mode controlled switching converters show symmetrical dynamic phenomenon corresponding to a symmetrical point or a symmetrical axis. The numerical simulation results are verified by the time-domain simulation, which further indicates that with the duty ratio varying, the peak and valley current-mode controlled switching converter reveals a symmetrical dynamic phenomenon, or a symmetrical dynamic phenomenon accompanying an asymmetrical dynamic phenomenon, or an asymmetrical dynamic phenomenon.