Output Voltage Overshoot Research Articles

Design of 3-level LLC converter voltage controller for wide input voltage fluctuations

The auxiliary power supply unit for railway vehicles delivers various power to the passenger car. Maintaining isolation between the catenary power line and the auxiliary power in the compartment is typically essential. To ensure electrical isolation, an efficient LLC resonant converter is utilized among isolated DC-DC converters. Generally, LLC resonant converter primarily employ PFM control method. However, there is a limitation in increasing the switching frequency at high input voltages, making it difficult to handle wide input voltage fluctuations from the overhead catenary power line. To overcome this limitation, the PFM control method is introduced alongside the existing PFM control method, resulting in the presence of two controllers. However, since these two controllers regulate the output voltage differently, there is a potential for output voltage overshoot due to significant input voltage fluctuations. This paper proposes a method that combines PFM and PWM controllers, along with feed-forward compensation, to address these issues. The effectiveness of this proposed method is validated through PSIM simulation and experimentation.

Design of Sliding Mode Controller Based on 7 nm Gate Logic

In this paper, a new discrete-time sliding mode predictive control (DSMPC) strategy with a PID sliding function is proposed for synchronous DC–DC Buck converter. The model predictive control, along with digital sliding mode control (DSMC) is able to further reducing the chattering phenomenon, steady-state error, overshoot, and undershoot of the converter output voltage. The proposed control method implementation only requires output error voltage evaluation. The effectiveness of the proposed DSMPC is proved through simulation results executed by the MATLAB/SIMULINK software. These results demonstrate its performance is superior to DSMC. The selected synchronous Buck converter in this paper has 380 V input voltage and 48 V output voltage that can be applied in sections of DC distribution systems.

Efficiency and dynamic characteristics of improved dual‐stage power converter setup with advanced model predictive controller for electric vehicle battery charging

SummaryThis paper proposes an advanced power converter setup to charge an electric vehicle battery from a renewable energy source, such as solar photovoltaic. An improved Z‐source DC–DC boost converter (IZSBC) is utilized in the first stage. A synchronous rectifier (SR) of a phase‐shifted full‐bridge converter (PSFBC) with continuous conduction mode (CCM) is employed in the second stage using the zero voltage switching (ZVS) technique to provide isolation between the source and the load. To address the disadvantage of undesirable dynamic characteristics of the PSFBC‐SR, an advanced voltage control using the advanced model predictive controller (AMPC) is suggested to improve the dynamic characteristic of the PSFBC‐SR converter and prevent output voltage overshoot. An AMPC‐based new control method is preferred to eliminate body‐diode conduction for improved efficiency at any load conditions. Simulation and experimental designs of 0.5 kW with a 25 V DC input from the SPV, a boosted output of 100 V for a 60 V, 16 Ah battery bank and switching frequencies of 100 and 250 kHz for IZSBC and PSFBC‐SR, respectively, are produced and evaluated. Results show an efficiency of 93.7% with 31.44 W loss in simulations and 93.94% with 30.25 W loss in hardware tests. The preferred system has fast dynamics and is robust to sudden load impedance changes, thereby improving current tracking and reducing converter losses. The AMPC strategy proposed in this paper can increase conversion efficiency and control the output voltage without additional gain tuning.

Research on High-Quality Control Technology for Three-Phase PWM Rectifier

With the development of power-electronics technology, PWM rectifiers are widely used in many fields. They are especially suitable for high-precision- and high-efficiency-application scenarios, such as communication and industrial control. Although it has many advantages, overshoot control during startup is a challenge. Therefore, this paper first derives the input–output mathematical model through equation establishment and dq-coordinate transformation. Next, a voltage and current double closed-loop simulation model is established in MATLAB/Simulink, and its control effect is analyzed. On this basis, a new voltage-setting strategy is designed to reduce the output-voltage overshoot of the PWM rectifier when starting. The simulation results demonstrate that the strategy has a good application effect and can contain starting-voltage overshooting from 12.88% to 0.925%. Moreover, the principle of this strategy is simpler and easier to understand and implement compared with traditional strategies.

Coupled Inductors With an Adaptive Coupling Coefficient for Multiphase Voltage Regulators

As modern microprocessors continuously advance, a high-efficiency, high-power-density voltage regulator design with fast transient response is a must. Compared with the non-coupled-inductor-based solution, a multiphase buck converter with an indirect-coupled inductor (ICL) can dramatically improve the circuit transient response without increasing the inductor current ripple and sacrificing efficiency. However, a design conflict between the steady-state performance and transient response exists for the conventional ICL structure with a given inductor size. This article first analyzes the benefits and limitations of the conventional ICL based on a detailed modeling process. Then, an adaptive-coupled inductor structure is proposed to solve the issue. This is realized by applying a variable inductor in the extra winding loop of an ICL. By self-adjusting the coupling coefficient, the proposed structure can further improve the circuit transient response without increasing the phase inductor current ripple. A four-phase buck converter with the proposed inductor structure is experimentally tested, and it shows that a 25.6% output voltage overshoot reduction or a 21.8% output capacitance reduction can be realized by the proposed coupled inductor structure.

Driving Control of GaN Devices for Transient Response Improvement of Voltage Regulator

With the continuous development of microprocessors, more stringent voltage regulation requirements have been put forward for the voltage regulators (VR) in the transient process. This letter proposes a driving control method for gallium nitride (GaN) devices to improve the transient response of the VR. When the GaN device conducts reverse, its source-drain voltage can be controlled by its gate voltage. During load step-down transient, the reverse conduction voltage of the GaN device is naturally applied across the inductor, which can be utilized to speed up the change rate of the inductor current. As a result, the overshoot of the output voltage can be reduced during load step-down transient. The proposed method does not need to modify the power circuit, and is easy to implement. Finally, the effectiveness of the proposed method is verified by experiments. The results show that the output voltage overshoot is reduced by 55%, and the transition time is shortened by 80% using the proposed method. The results also show that with the same overvoltage, using the proposed method can reduce the output capacitance by 57% and the transition time by 77%, thereby increasing the power density of the VR circuit and saving costs.

Performance Analysis and Comparison of Non-Inverting Buck-Boost Converter Using PI, OCC, and Hybrid OCC-PI Control

The study compares and analyses the performance of the one-cycle control (OCC), hybrid one-cycle-proportional integral control (OCC-PI), and the conventional PI control method applied to the non-inverting buck-boost converter. The hybrid OCC-PI control method combines the OCC and PI control techniques to provide a hybrid non-linear closed-loop control technique for regulating the buck-boost converter. The MATLAB/Simulink equivalent system model was simulated with design parameter variations using a wide input voltage range of 9 – 36 V, a nominal output voltage of 28 V, and a fixed switching frequency of 250 kHz to validate the control response speed, reliability, and robustness of the proposed control technique. The simulation results due to input voltage, output voltage, and load variations were carried out whiles recording the settling time, overshoots, efficiency, output voltage, and inductor current ripples due to each applied control technique. The simulation results indicated that the Hybrid OCC-PI control provides better response speed and a lower output voltage overshoot relative to the PI. It also provides better reference voltage tracking compared to the OCC control method.

A 25 MHz Fast Transient Adaptive-On/Off-Time Controlled Three-Level Buck Converter

This work presents a 25 MHz adaptive on/off-time-controlled three-level buck converter with a fast reference tracking speed and high light load efficiency. The self-balancing scheme of the flying capacitor voltage is revised and extended for a broad conversion ratio range from 0.17 to 0.833. To reduce the error of the self-balancing scheme when applied to a high frequency three-level buck converter with an on-chip flying capacitor, a real-time calibration loop on the flying capacitor voltage is introduced, effectively reducing the balancing error from 340 mV to 20 mV. A turning-point output voltage prediction for the three-level buck converter is presented to achieve near-optimal reference tracking with a fast tracking speed and negligible output voltage undershoot or overshoot. The up- and down-tracking takes 81 ns and 72 ns, respectively, for a 1-V step with an inductor of 47 nH and an output capacitor of 47 nF. The three-level converter achieves a precise discontinuous conduction mode (DCM) operation with an adaptive switching frequency at light load by means of a feedback loop-based method. An approximately 28.2% increment in efficiency is achieved with a load of 10 mA. The three-level buck converter has a peak efficiency of 92.8% and an over 85% efficiency in most of the operation regions.

A Low-Power, Fast-Transient Output-Capacitorless LDO with Transient Enhancement Unit and Current Booster

With the wide application of advanced portable devices, output-capacitorless low dropout regulators (OCL-LDO) are receiving increasing attention. This paper presents a low quiescent current OCL-LDO with fast transient response. A transient enhancement unit (TEU) is proposed as the output voltage-spike detection circuit. It enhances the transient response by improving the slew-rate at the gate of the power transistor. In addition, a current booster (CB), which consists of a current subtractor and a non-linear current mirror, is designed to improve the slew-rate further. The current subtractor increases the transconductances of the differential-input transistors to obtain a large slewing current, while the non-linear current mirror further boosts the current with no extra quiescent current consumption. The simulated results show that the proposed OCL-LDO is capable of supplying 100 mA load current while consuming 10.3 μA quiescent current. It regulates the output at 1 V from a supply voltage ranging from 1.2 to 1.8 V. When the load current is stepped from 1 mA to 100 mA in 100 ns, the OCL-LDO has attained a settling time of 190 ns, and the output voltage undershoot and overshoot are controlled under 110 mV.

High-Precision Low-Temperature Drift LDO Regulator Tailored for Time-Domain Temperature Sensors.

This paper proposes a high-precision LDO with low-temperature drift suitable for sensitive time-domain temperature sensors. Its topology is based on multiple feedback loops and a novel approach to frequency compensation, that allows the LDO to maintain a large DC gain while handling capacitive loads that vary over a wide range. The key design constraints are derived by using a simplified, yet intuitive and effective, small-signal analysis devised for LDOs with multiple feedback loops. Simulation and measurement results are presented for implementation in a standard 130 nm CMOS process: the LDO outputs a stable 1 V voltage, when the input voltage varies between 1.25 V to 1.5 V, the load current between 0 and 100 mA, and the load capacitor between zero and 400 pF. It exhibits a DC load regulation of 1 µV/mA, a 288 µV output offset with a standard deviation of 9.5 mV. A key feature for the envisaged application is the very low thermal drift of the output offset: only 14.4 mV across the temperature range of −40 °C to +150 °C. Overall, the LDO output voltage stays within +/−3.5% of the nominal DC value over the entire line voltage, load, and temperature ranges, without trimming. The LDO requires only 1.4µA quiescent current, yet it provides excellent responses to load transients. The output voltage undershoot and overshoot caused by the load current jumping between 0 and 100 mA in 1 µs are: 10%/22% for CL = 0 and 12%/16% for CL = 400 pF, respectively. A comparative analysis against seven LDOs published in the last decade, designed for similar levels of supply voltage and output voltage and current, shows that the LDO presented here is the best option for supplying sensitive time-domain temperature sensors. The smallest thermal drift of the output offset, smaller than +/−15 mV, that is, 6.7 times smaller than its closest competitor, and the best overall performance when PSR up to 1 kHz, was considered.

An area-efficient automotive LDO with scalable maximum load current exhibits excellent response to line and load transients

A compact LDO with scalable maximum load current is presented. A transconductor with multiple current outputs implements the error amplifier, as well as two feed-forward paths. A push-pull output stage is employed to drive the gate of the pass transistor. Zeros are created by the feed-forward paths, as well as by an RC network to realize an area- and power-effective frequency compensation, that ensures the LDO stability over a wide range of load currents and capacitances. The proposed LDO was implemented in a 0.13 µm CMOS process. The sizing strategy is presented in the paper, along with simulation and measurement results that validate the design. The LDO provides a stable 1 V output voltage when the input voltage varies between 1.2 V and 1.5 V, the load current varies between zero and 100 mA, and the load capacitance takes values between 100 nF and 10 µF. Its nominal quiescent current is just 9.6 µA while the die area is exceptionally small, only 0.0065 mm2. The integrated LDO exhibits excellent responses to load and line transients: when the load current jumps between 100 µA and 100 mA in 0.3 µs the measured output voltage overshoot and undershoot are below 3.6% of nominal value for CLOAD = 470 nF; the measured overshoot and undershoot caused by the line voltage jumping between 1.3 V and 1.5 V in 3 µs are smaller than 1.2% for the same CLOAD.

Slew-Rate Booster and Frequency Compensation Circuit for Automotive LDOs

This paper presents a slew-rate booster and frequency compensation circuit for automotive LDOs. The proposed circuit addresses three major LDO design challenges: frequency compensation for a wide range of output currents and load capacitors, fast response to load transients and reduced sensitivity to the supply variations. It was used to implement an LDO that provides a 5V output voltage and up to 50mA output current over a wide range of supply voltages &#x2013; from 5.25V to 40V &#x2013; and temperatures, &#x2212;40^oC to &#x002B;150^oC, while burning as little as <inline-formula> <tex-math notation="LaTeX">$30\mu \text{A}$ </tex-math></inline-formula>. The slew-rate booster ensures that the output voltage overshoot and undershoot caused by load jumps of 50mA/<inline-formula> <tex-math notation="LaTeX">$\mu \text{s}$ </tex-math></inline-formula> remain below 4&#x0025; of the nominal Vout value. Moreover, the LDO meets the E-06 test requirements within the LV124 automotive standard: the output voltage varies within 10&#x0025; of its nominal value when sinusoidal voltages with amplitudes up to 20V peak-to-peak and frequency varying between 15Hz and 100kHz are injected into the LDO supply line. This feature is achieved while using a capacitor of only <inline-formula> <tex-math notation="LaTeX">$1\mu \text{F}$ </tex-math></inline-formula> at the output, up to 10 times smaller than the decoupling capacitors used by similar LDOs reported previously.

A Detection Circuit for Improving the Unloading Transient Performance of the COT Controller

Fast load transient response and high light-load efficiency are two key features of the constant on-time (COT) control technique that has been widely used in numerous applications, such as for voltage regulators and point-of-load converters. However, when load step-down occurs during an on-time interval, the COT controller cannot respond until the COT interval expires. This delay causes an additional output voltage overshoot, resulting in unloading transient performance limitation. To eliminate the delay and improve the unloading transient response of the COT controller, a load step-down detection circuit is proposed based on capacitor current COT (CC-COT) control. In the detection circuit, the load step-down is monitored by comparing the measured capacitor current with the preset threshold voltage. Once the load step-down is monitored, the on-time is promptly truncated and the switch is turned off. With the proposed detection circuit, the CC-COT-controlled buck converter can monitor the load step-down without any delay and obtain less output voltage overshoot when the load step-down occurs during the on-time interval. PSIM circuit simulations are employed to demonstrate the feasibility of the detection circuit.

Modeling Water and Thermal Transients Inside Proton Exchange Membrane for Vehicle Application Fuel Cells

Dynamic performance of proton exchange membrane fuel cells (PEMFCs) is very important for vehicle application. However, limited by the structure and dimension, it is still difficult to understand the internal transient behaviors by experiment. In this work, two-phase, non-isothermal, transient models are developed to investigate the water and thermal transients inside the membrane and their influences on the performance of fuel cells. Firstly, the simulation result and the experimental data are compared. The simulation result basically accords with the experimental data because it captures well the overshoot and downshoot of output voltage as current step changes, which are mainly related to the evolution of membrane water content (λ). A driving protocol is then set up to simulate a real vehicle running on the road with consideration of starting, variable load acceleration, overload running, etc. During the simulation, we observe a power overshoot as the current step changes during overload running, which is caused by membrane dehydration at high temperature. To decrease the temperature, the influences of loading speed and coolant temperature are investigated, respectively. The results indicate that reducing loading speed can relieve the power overshoot to some extend, while the reduction of coolant temperature during loading can fundamentally avoid the high temperature and membrane dehydration, and thus improve fuel cell output performance. Lastly, based on an inverse relationship hypothesis between λ and the glass transition temperature of membrane (Tg), the dynamical changes of Tg are explored. It is found the membrane temperature will exceed its glass transition temperature if operation temperature is higher than 105 ℃ during overload running, which may result in polymer melting.

Switching Power Supply Control Strategy Based on Monitoring Configuration

In this paper, a new discrete-time sliding mode predictive control (DSMPC) strategy with a PID sliding function is proposed for synchronous DC-DC Buck converter. The model predictive control, along with digital sliding mode control (DSMC) is able to further reducing the chattering phenomenon, steady-state error, overshoot, and undershoot of the converter output voltage. The proposed control method implementation only requires output error voltage evaluation. The effectiveness of the proposed DSMPC is proved through simulation results executed by the MATLAB/SIMULINK software. These results demonstrate its performance is superior to DSMC. The selected synchronous Buck converter in this paper has 380 V input voltage and 48 V output voltage that can be applied in sections of DC distribution systems.

A Novel Boost-Buck Converter Architecture for Improving Transient Response and Output-Voltage Ripple

Buck-boost converters are widely used in the development of DC-DC converters. Several techniques and algorithms have been introduced to improve the transient response of buck-boost converters. However, due to the opposite trends of the output current change and the output voltage change, undershoot or overshoot in the output voltage still seems to be inevitable. In order to overcome this problem, a novel boost-buck converter architecture is proposed to build a fast transient response DC-DC converter. The converter consists of a cascaded configuration of the boost and buck stages. The boost stage converts the input voltage to the shared capacitor voltage and the buck stage supplies energy to the load by converting the shared capacitor voltage to the output voltage. By harnessing the energy stored in the shared capacitor, the transient response of the boost buck converter can be improved to 2 µs in a step-up load current change of 1 A with an output-voltage ripple of 15 mV.

Wide voltage gain range application for full‐bridge LLC resonant converter with narrow switching frequency range

In wide voltage range applications, traditional LLC converters suffer from the following issues: (i) to cover a wide voltage gain operating range, the required switching frequency range is also large, which challenges the design and optimisation of magnetic components, gate driver circuitry, and electro-magnetic interference filter; (ii) a small magnetising inductance is preferred in wide voltage gain range application, which leads to the increase of circuit circulating current and corresponding conduction loss; (iii) passive elements are determined based on the minimum switching frequency, so bulky passive elements are required to satisfy the required operation range. To solve these problems, in this study, a full-bridge LLC (FBLLC) resonant converter with two operation modes, namely full-bridge operation and frequency doubler operation, is proposed for wide voltage gain range application. The FBLLC converter discussed in this study can be designed in half of the input voltage range when compared with the conventional method, so smaller switching frequency operating range and higher efficiency operation are guaranteed. In addition, the smooth mode transition is achieved by introducing switching frequency feedforward control and small output voltage overshoot or undershoot is observed. A 150 W experimental prototype was built to validate the theoretical analysis.

A High-Current All-Solid-State Pulse Generator Based on Marx Structure

In recent years, semiconductor switches have gradually replaced traditional gas switches due to their long lifetime and smaller volume. However, the rated current of the semiconductor switches limits the applications of the all-solid-state pulsed power generators. Usually, multiple semiconductor switches or pulse generators are required in parallel to share a large current in the case of the enormous power applications. In this article, a new high-current all-solid-state pulsed power generator based on Marx generators connected in parallel was proposed. One group of semiconductor switches was used to control the charging of the Marx generators. The driving circuits can be simplified due to fewer switches. It can also improve the discharge frequency and the output voltage over a capacitive load. Six 4-stage Marx generators connected in parallel have been employed to verify the proposed topologies on a capacitive and a resistive load. From the experimental results, with 1.2 kV, 150 A, and 2.4 kV, 50 A, pulses have been got on an 8- $\Omega $ resistive load and a 440-pF capacitive load, respectively. The balanced output currents can reduce the output voltage overshoot and make the system more stable and reliable.

Soft-Switching Auxiliary Current Control for Improving Load Transient Response of Buck Converter

An auxiliary current control is proposed herein to improve the load transient response of the buck converter. The proposed technique increases the efficiency of the auxiliary converter by employing soft switching. The design guidelines for achieving a capacitor charge balance for the output capacitor during the transition are also presented. The simulation results revealed that the output voltage overshoot and settling time during the load step-down transient were 62 mV and 29.4 μ s, respectively; however, in the case of conventional time-optimal control, these values were 666 mV and 57.2 μ s, respectively, under the same condition. The estimated power loss of the proposed scheme was only 45%–60% of those of the conventional counterparts. The performance and effectiveness of the technique were experimentally verified using a prototype buck converter with a 15 V input, 3.3 V output, and 200 kHz switching frequency.

Passivity-Based Control Design Methodology for UPS Systems

This paper presents a passivity-based control (PBC) design methodology for three-phase voltage source inverters (VSI) for uninterruptable power supply (UPS) systems where reduced harmonic distortions for the nonlinear load, reduced output voltage overshoot, and a restricted settling time are required. The output filter design and modification for efficient control and existing challenges with the assignment of scaling coefficients of the output voltage, load, and inductor currents are addressed and analyzed. Notably, special attention is given to the modulator saturation issue through implementing an accurate converter model. Applications of the two versions of PBC in three-phase voltage source inverters using stationary αβ and rotating dq frames for a constant frequency of the output voltage are presented. Furthermore, the influence of the PBC parameters on the power converter performance is investigated. A comparative simulation and the experimental results validate the effectiveness of the presented passivity-based control design methodology.