Peak current mode-controlled pulse width-modulated active clamp forward converter with centre tap transformer

This paper presents the principles and performance of peak current mode control applied to active clamp forward converter in comparison to the conventional voltage mode control. There is a clamp circuit comprising one auxiliary switch and one clamp capacitor, used in the forward converter to recycle the energy stored in the transformer. Due to presence of clamp circuit the active clamp forward converter with center tapped secondary exhibits fourth order power stage dynamics. When conventional voltage mode control is adapted, the forth order power stage dynamics imposes limitations on the closed loop performance of the converter. It is demonstrated that current mode control can be adapted to enhance the closed loop performance of active clamp forward converter. Different transfer functions are derived using state space average model. The peak current mode control is applied and simulation results are presented.

High step-up gain Coupled Inductor Boost Converter (CIBC) discovers application in Distributed Generation System (DGS) to step-up voltage level of renewable energy sources. In DGS system, high step-up CIBC with a regulated output voltage and faster dynamic operation is required at various local loads. Transfer function of CIBC has one zero on Right Hand Plane (RHP). It is difficult to achieve high bandwidth when system has Non-Minimum Phase (NMP) characteristic. Peak Current Mode (PCM) control is the well-known technique to improve dynamic response in DC-DC converters. To design feedback controller and to analysis behaviour of CIBC, small signal model of CIBC is required. This paper presents small signal control-to-output voltage transfer function for PCM control of CIBC. Effect of artificial ramp is considered in derivation of this small signal model. A state space averaging method is used to derive small signal model. PI controller is designed using root locus technique. Time and frequency response of Voltage Mode Control (VMC) and PCM control of CIBC are compared. PCM control improves transient response and stability margin of CIBC for wide range of load variations. It also reduces effect of RHP zero. Simulation of CIBC using PCM control to get regulated output voltage is done in PSIM. Simulation results demonstrate that CIBC is able to get desire dynamic and steady state response of output voltage using PCM control under dynamic load conditions.

<p>This research paper presents the design issues of digital Controllers for Forward Converter with Active Clamp circuit (ACFC). Brief review of Working Principle and mathematical modelling of the converter is first given. The importance of Digital Controllers for forward converter and design procedure is described in detail. And the validity of designed controllers and achievement of desired compensation is verified by the results of implemented digital controllers to Active clamp forward Converter (ACFC). Finallly results are analyzed by applying disturbances at both supply end and Load ends of the converter. And the conclusions are made based on obtained results of Voltage Mode Controller (VMC) by comparing with the results of the Current Mode Controller (CMC).</p>

In this paper, average current mode control and peak current mode control methods are compared. A full-bridge converter has been chosen to test the controller performances. For the accurate design of controllers, some performance parameters are specified for the converter. The full-bridge converter output is used as 28V, 5.6kW. The desired maximum ripple at the output voltage is 200mV and the allowable ripple at the output current is 5A. Converter performance has been simulated with PSIM and discussed. Then, average current mode controller and peak current mode controller designs were made with this converter. The design of these methods has been done separately and has been simulated. Comparative results of these controllers were given and their pros and cons over each other were discussed. The things to be done to make the performance improvements of the controllers were mentioned and evaluated.

This study proposes the application of valley current mode (VCM) control in a flyback dc–dc converter with a large duty cycle. The use of VCM control eliminates the need of slope compensation in operation under a duty cycle greater than 50%. For operation with duty cycle near the boundary value (50%), a relatively small compensation ramp is required comparing with that of the conventional peak current mode (PCM) control. Moreover, the noise sensitivity issue of PCM control is also addressed by the change of the current sensing position in VCM and hence the immunity against the current spike. The VCM-controlled flyback converter achieves consistent steady-state and transient-response performances as its PCM-controlled counterpart. Stability analyses of inner current loop and overall closed-loop system are presented. Experiments are also conducted to evaluate the effectiveness of VCM control in controlling the flyback dc–dc converter.

Small signal audio susceptibility of flyback converter with peak current mode control method is presented by utilizing pwm-switch model in Continuous Conduction Mode (CCM). The analysis provides input voltage to output voltage transfer function together with its zeros and poles in symbolic form. Numerator and denominator of the resultant transfer function are both 3rd order. While symbolic equations of zeros are provided as exact solutions, the symbolic equations of poles are provided as approximate solutions with the assumption that the real pole is well separated from the resonant frequency of the complex pole pair. Symbolically derived transfer function of flyback converter is validated on a numerical example by time domain PSIM simulations on a switching flyback converter model. The mathematical analysis and PSIM simulations of input voltage to output voltage transfer function of the converter agree very well up to frequencies below half the switching frequency.

This paper presents a unified discrete model for pulse-width modulated (PWM) switching DC to DC converters. The major achievement is that, without any topology modification, the proposed model can be used for performance analysis of the buck, boost and buck-boost converters with any of the two current-mode controls: peak current-mode control and average current-mode control. Three important factors are considered: parasitical effects of circuit elements, non-linear inductance dependent on the current flowing through it, and control time delay, such that the accuracy of performance prediction is greatly improved. Magnetic field finite element analysis (FEA) is conducted to calculate the non-linear differential inductance. By implementing the proposed model into Matlab/Simulink, a simulation model is built. The model has been used for the performance analysis of an existing flyback converter with the peak current-mode control. The simulation results are in good agreement with the actual performance, validating the proposed model.

Photovoltaic (PV) systems with a battery back-up form an integral part of distributed generation systems and therefore have recently attracted a lot of interest. In this paper, we consider a system of charging a battery from a PV panel through a current mode controlled boost dc-dc converter. We analyze its complete nonlinear/nonsmooth dynamics, using a piecewise model of the converter and realistic nonlinear v–i characteristics of the PV panel. Through this study, it is revealed that system design without taking into account the nonsmooth dynamics of the converter combined with the nonlinear v–i characteristics of the PV panel can lead to unpredictable responses of the overall system with high current ripple and other undesirable phenomena. This analysis can lead to better designed converters that can operate under a wide variation of the solar irradiation and the battery's state of charge. We show that the v–i characteristics of the PV panel combined with the battery's output voltage variation can increase or decrease the converter's robustness, both under peak current mode control and average current mode control. We justify the observation in terms of the change in the discrete-time map caused by the nonlinear v–i characteristics of the PV panel. The theoretical results are validated experimentally.

Peak current mode (PCM) control has been widely used for the control of switching dc–dc converters due to its excellent transient performance. With the development of single-inductor dual-output (SIDO) dc–dc converters, PCM control technique is introduced to the control of SIDO dc–dc converters. Conventional PCM buck converter has only one reference current, with two inductor current borderlines are used to divide the operation modes of inductor current. However, PCM SIDO buck converter has more inductor current borderlines as it has one more reference current than that of PCM buck converter. In this paper, inductor current borderlines of PCM SIDO buck converter are investigated, and unified discrete iterative model of PCM SIDO buck converter is established. The effect of the difference of reference currents, initial inductor current and input voltage on the stability of PCM SIDO buck converter has been discussed by using bifurcation diagrams. The study results show that the stability of PCM SIDO buck converter is sensitive to the difference of reference currents, initial inductor current and input voltage. The stability boundary of the difference of reference currents, stability region of initial inductor current, and stability boundary of input voltage are derived. Lyapunov exponent and experimental results are carried out to verify the theoretical analysis results.

Nowadays, as the demand of portable electric products is increased, that of adaptors, which charge the battery of portable electric products or supply power, is also increased. Key issues of portable electric products are power density, temperature, average efficiency and stand-by power. Many isolated DC/DC converter topologies suitable for high power density is presented [1]∽[3]. All of them try to reduce size and cost by minimizing the number of components. Generally, converter topologies which have no output-inductor for DC/DC converter is suitable for high power density application. Active clamp flyback converter and output-inductor-less forward converter are representative converters without output inductor. However, these converters have critical problems. In active clamp flyback converter, DC offset current which degrades transformer utilization and makes transformer bulky. Therefore it causes low power density. In the other side, output-inductor-less active clamp forward converter has high RMS value of current which causes heat problem. This paper proposes an output-inductor-less active clamp forward converter employing current boost-up circuit for adaptors. Due to applying the proposed current boost-up circuit, the proposed converter has low conduction loss and low voltage ringing of the secondary rectifier. This paper presents the operational principle and design consideration of the proposed converter. Experimental results are demonstrated to verify the feasibility and advantages of the proposed converter.

The Renewable energy system, electric vehicle, and telecommunication applications require relatively stable power converters with a high gain and enhanced noise immunity. A study of three different types of current-mode controllers for high-gain ultra-lift Luo-converter (ULC) is discussed in this paper. The stability of a constant frequency peak current-mode controller (PCM), an average current-mode controller (ACM) and a variable frequency hysteresis current-mode controller (HCM) are analyzed based on small-signal characteristics. Using mathematical modeling of the controllers, the closed-loop transfer functions such as control voltage to output voltage, current loop gain, inductor current to control voltage, and audio susceptibility are obtained. These transfer functions along with MATLAB simulation results for PCM, ACM and HCM controllers are compared. Then, the component losses of the ULC converter using PCM, ACM and HCM controllers are calculated and an efficiency comparison of different control techniques is done. Investigations of the voltage and current stresses of the switch and diodes are also carried out. Finally, a prototype is fabricated to validate the performance of the converter.

This paper presents a thorough literature reviews of control methods to improve transient response in switch mode power supply (SMPS). A fast transient response to a step load change is very essential in a power supply. The transient response can be improved by means of feedback control method. There are two feedback control methods widely used for SMPS that are, voltage mode control (VMC) and peak current mode control (PCMC). A simulation study on these feedback control methods has been done using Matlab/Simulink. It is found that the PCMC helps the SMPS for a faster transient response compared to the VMC. Based on all the reviews a new method is being investigated known as "Voltage Injection Switching Inductor" (VISI) method. This feedback control method provides a better transient response to PCMC. The comparison of these simulation results validates the proposed idea.

The paper presents an upgrade of the Peak Current Mode Control (PCMC) for a Buck DC-DC Converter. Constant Off-Time algorithm has a fixed off-switch phase, and, conversely to the typical PCMC, the duration of the switching period is free to change depending on the load and the battery voltage. In this way the instability issues, typical of a PCMC, are solved. The circuit is able to robustly sink 3 ± 5%A average current from a car battery source, in a 3.5 V output voltage - 212kHz maximum frequency application. In addition, the circuit intrinsically provides protection against over-current and allows precise control over the current features (peak, average and ripple). The concept will result in a fully integrated system without external pad to sense the current, thanks to the proposed integrated sensing technique. The power consumption is also reduced since the current is read only during the on-switch phase.

Sensorless current-mode (SCM) control of DC-DC converters is a feedforward open loop scheme, which is compared to peak current-mode (PCM) control. Small signal model simulations of each controller are validated by experimental results. SCM offers improvements over the line disturbance rejection of current-mode control without feedback or current sensing. SCM is demonstrated to be useful in both open loop and closed loop configurations, by exploiting its inherent reference tracking and line disturbance rejection. In contrast, PCM requires a high gain two-loop control for voltage regulation.

This paper presents a novel structure of current-sharing active-clamped forward power converter (ACFPC) with self-driven synchronous rectifier. The droop control method is used to improve the output power and efficiency by automatic current sharing. Also, for improving the whole efficiency, self-driven synchronous rectifier circuit is used, comparing with traditional method, which is simpler with low cost. The operation principle and experimental results are shown in this paper, which has the maximum efficiency over 90% with output power 200W.