Average and Peak Current Mode Control Comparison for Full-Bridge Converter

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.

Control techniques for high-power-factor rectifiers which do not need input voltage sensing are gaining considerable attention due to their simpler implementation and inherently superior stability, as compared to conventional average or peak current\nmode control. Among these, the solutions based on the integration of a current signal (switch, diode, or inductor current) provide an inherent noise immunity, which makes them further appealing. This paper proposes a simple implementation of one such control technique for high-power-factor flyback, Cuk, or Sepic rectifiers, which, while still retaining a high power factor, further reduces the control complexity, thus making the solution very attractive for smart-power integration. A 200-W flyback rectifier with the proposed control technique was implemented and tested. The achieved results are in good agreement with the expected performance.

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.

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.

Power quality disturbances, such as voltage sags and instantaneous power interruptions, are probably the most frequent and damaging phenomenon in industrial environments. Thus, to improve the sustainability of electrical equipment, the power supplies should tolerate these disturbances. The PFC boost converter operating in CCM is exhaustively used as a first-stage in the power supplies. The average current mode control is the most popular technique and implemented with analog or discrete-time controllers. However, at instantaneous power interruption, the inner controllers go to saturation mode. Consequently, the switching device (MOSFET), of the converter, might be permanently damage when the power returns after voltage interruption. Another current control technique is self-control. In this case, the dynamics controllers are different. Therefore, this paper investigates the operation of the converter at instantaneous power interruption. The average current mode control and self-control are analyzed. Protection strategy is implemented, by FPGA, in a single-phase CCM PFC boost converter. Simulation and experimental results confirm and validate the analysis.

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.

A small signal analysis of DC-DC converters with Average Current Mode Control (ACMC) in Continuous Conduction Mode (CCM) is performed in a unified manner. Design-oriented equations are derived for all three types of DC-DC converters. These equations are such that they are expressed explicitly with converter circuit and operating parameters, making them easy to be directly applicable to practical design purposes. Experimental results of an ACMC Boost converter are given to validate the model prediction with good correlation.

The purpose of this paper is to present a drastic improvement in the conventional ACC (average current mode control) of switching DC-DC power converters, consisting of the addition of an auxiliary controller in the control loop, besides the current and voltage regulators. The model-based auxiliary controller preserves the closed loop small-signal bandwidth (including loop gain crossover frequency and stability margins) of buck derived converters over a large range of variation of the power stage passive elements, the load and the line voltage. Moreover, this control scheme shows much better perturbation rejection properties (closed loop impedance and audiosusceptibility) than conventional ACC. From a control theory point of view, robust performance is achieved preserving stability. A 5 V-5 A, 50 kHz buck prototype operating from an input voltage ranging from 30 V to 15 V has been experimentally tested with different LC output filters, line and load conditions, including discontinuous conduction mode. Measurements of the small signal frequency response of the converter (loop gain, closed loop audiosusceptibility and output impedance) have been carried out, showing the improvement achieved by the proposed control scheme. The empirical large signal response of the converter, under load steps, is also shown in this paper in order to validate the concept.

The application of the average current mode control (ACMC) to a new type of very efficient post-regulator is studied in this paper. This post-regulator, called series-switching post-regulator (SSR), has been proposed to improve the dynamic response series-switching of power factor correctors (PFC), The post-regulator exhibits very high efficiency due to the fact that only a part of the total power undergoes a power conversion process. Using ACMC, the bandwidth of the post-regulator increases in relation to the one obtained when a conventional voltage-mode control (with or without feedforward) is used. As a result, the attenuation of the input voltage ripple (100-120 Hz) increases and, a lower bulk capacitor can be used to obtain a low voltage ripple at the output, which is extremely important when a battery is connected at the output. This is rather common in distributed power supply systems.

Constant current sources are required to drive multiple color LED strings and the LED drivers that drive these LED lighting systems should provide multiple constant currents from a single dc source. In this paper, a single inductor multiple current output (SIMCO) converter that can provide N- independently controllable constant current outputs is reported. The average current in each color LED string is controlled independently by using hybrid average current mode control (HACMC). The HACMC combines the advantage of both average current mode control and charge control method. Traditional dimming approaches such as pulse width modulation and analog dimming can be incorporated in the proposed topology for color tunability and correlated color temperature control. The proposed approach uses a simple control logic, which is modular and can be scalable to N color LED lighting systems. The operation of the SIMCO converter with the HACMC is explained in detail. Simulation and experimental results with 48 V input and 12 W for N = 3 (RGB) color systems are presented.

In this paper a single stage offline LED driver that can drive N-color HB-LED strings is presented. The proposed converter provides multiple current outputs for N-Color HB-LED strings from an AC input. The current outputs are independently controllable to obtain the desired Correlated Color Temperature (CCT) and high Color Rendering Index (CRI) for dynamic lighting systems. Hybrid Average Current Mode Control (HACMC) approach is used to realize multiple current outputs. HACMC is a combination of both the Average Current Mode Control (ACMC) and non-linear charge control. The proposed converter also provides Power Factor Correction (PFC) to the AC input mains. Simulation and experimental results of a high CRI multi-color LED lighting system with 110V AC input are presented.

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.

This paper presents a method to stabilize DC power distributed systems (DPSs) under Average-Current-Mode (ACM) control technique. ACMs lacked the attention as the Voltage-Mode-Control (VMC) and Peak-Current-Mode (PCM) control methods are prevalent in the literature. The proposed method adds an extra negative feedback to the original ACM controller in order to eliminate the impedance interaction between the source and load converters. As a result, the peaking in the source-converter output impedance (Z o ) was eliminated. From a mathematical perspective, the added feedback loop compensates for the magnitude deficiency, which occurs at the resonance frequency of the source-converter, in the denominator of Z o . Hence, the dipping in the denominator magnitude was removed. The proposed controller was studied and analyzed mathematically, by simulations, and experimentally. All of the outcomes validated the effectiveness of the proposed controller.

This paper presents the control to output transfer function, principles and performance of peak current mode-controlled active clamp forward converter with centre-tap transformer. There is a clamp circuit comprising of one auxiliary switch and one clamp capacitor, which is used in the forward converter to recycle the energy stored in the magnetising inductor. Due to presence of clamp circuit, the active clamp forward converter with centre tap transformer exhibits fourth-order power stage dynamics. The current mode control is implemented to enhance the performance of the converter by sensing the main switch current. It is demonstrated that current loop gain splits not only the complex-conjugate pole of the output filter but also the complex-conjugate pole pair formed by clamp circuit into real poles. Different transfer functions are derived using state space average model. The peak current mode control is implemented experimentally using controller IC, UCC2891D, and the simulation results are verified with the experimental setup.

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.