Showing papers on "Buck–boost converter published in 2005"

High efficiency power converter

Abstract: A high efficiency power converter comprises a boost converter for converting an input voltage to a first voltage on a first output, a buck converter for converting the input voltage to a second voltage on a second output, a linear regulator for converting the first voltage to a third voltage on the second output when the second voltage is lower than a first threshold, and a voltage detector for detecting the input voltage for preventing a reverse current flowing from the second output to the buck converter when the input voltage is lower than a second threshold.

High step-up converter with coupled-inductor

Abstract: In this study, a high step-up converter with a coupled-inductor is investigated. In the proposed strategy, a coupled inductor with a lower-voltage-rated switch is used for raising the voltage gain (whether the switch is turned on or turned off). Moreover, a passive regenerative snubber is utilized for absorbing the energy of stray inductance so that the switch duty cycle can be operated under a wide range, and the related voltage gain is higher than other coupled-inductor-based converters. In addition, all devices in this scheme also have voltage-clamped properties and their voltage stresses are relatively smaller than the output voltage. Thus, it can select low-voltage low-conduction-loss devices, and there are no reverse-recovery currents within the diodes in this circuit. Furthermore, the closed-loop control methodology is utilized in the proposed scheme to overcome the voltage drift problem of the power source under the load variations. As a result, the proposed converter topology can promote the voltage gain of a conventional boost converter with a single inductor, and deal with the problem of the leakage inductor and demagnetization of transformer for a coupled-inductor-based converter. Some experimental results via examples of a proton exchange membrane fuel cell (PEMFC) power source and a traditional battery are given to demonstrate the effectiveness of the proposed power conversion strategy.

Pulse-width modulation of Z-source inverters

Abstract: Z-Source inverters have recently been proposed as an alternative power conversion concept as they have both voltage buck and boost capabilities. These inverters use a unique impedance network, coupled between the power source and converter circuit, to provide both voltage buck and boost properties, which cannot be achieved with conventional voltage-source and current-source inverters. To facilitate understanding of Z-source inverter modulation, this paper presents a detailed analysis, showing how various conventional pulse-width modulation strategies can be modified to switch a voltage-type Z-source inverter either continuously or discontinuously, while retaining all the unique harmonic performance features of these conventional modulation strategies. This paper starts by analyzing the modulation requirements of a single-phase H-bridge Z-source inverter, and subsequently extends the analysis to cover the more complex three-phase-leg and four-phase-leg Z-source inverters, with carrier-based implementation reference equations derived for all the inverters. The theoretical and modulation concepts presented have been verified both in simulation and experimentally.

A 233-MHz 80%-87% efficient four-phase DC-DC converter utilizing air-core inductors on package

Abstract: We demonstrate an integrated buck dc-dc converter for multi-V/sub CC/ microprocessors. At nominal conditions, the converter produces a 0.9-V output from a 1.2-V input. The circuit was implemented in a 90-nm CMOS technology. By operating at high switching frequency of 100 to 317 MHz with four-phase topology and fast hysteretic control, we reduced inductor and capacitor sizes by three orders of magnitude compared to previously published dc-dc converters. This eliminated the need for the inductor magnetic core and enabled integration of the output decoupling capacitor on-chip. The converter achieves 80%-87% efficiency and 10% peak-to-peak output noise for a 0.3-A output current and 2.5-nF decoupling capacitance. A forward body bias of 500 mV applied to PMOS transistors in the bridge improves efficiency by 0.5%-1%.

High boost converter using voltage multiplier

Abstract: With the increasing demand for renewable energy, distributed power included in fuel cells have been studied and developed as a future energy source. For this system, a power conversion circuit is necessary to interface the generated power to the utility. In many cases, a high step-up DC/DC converter is needed to boost low input voltage to high voltage output. Conventional methods using cascade DC/DC converters cause extra complexity and higher cost. The conventional topologies to get high output voltage use flyback DC/DC converters. They have the leakage components that cause stress and loss of energy that results in low efficiency. This paper presents a high boost converter with a voltage multiplier and a coupled inductor. The secondary voltage of the coupled inductor is rectified using a voltage multiplier. High boost voltage is obtained with low duty cycle. Theoretical analysis and experimental results verify the proposed solutions using a 300 W prototype.

A comparative evaluation of isolated bi-directional DC/DC converters with wide input and output voltage range

Abstract: The working principles and design equations of four different isolated, bi-directional DC to DC converter topologies (a dual active bridge converter, a series resonant converter and two multiple stage topologies) for a 2 kW bi-directional battery charger that can be operated in a wide input and output voltage range are presented in this paper. The results of a detailed mathematical analysis of the converter topologies as well as digital simulation results are used to select the most efficient topology for this specific converter application, where the two-stage series resonant converter is identified to be the most promising, with up to 90% efficiency at rated power.

Boost Converter with Coupled Inductors and Buck-Boost Type of Active Clamp

Abstract: This paper proposes a boost converter with coupled inductors and buck-boost type of active clamp. In the converter, the active-clamp circuit is used to eliminate voltage spike induced from the trapped energy in leakage inductor of the coupled inductors. The active switch in the converter can still sustain a proper duty ratio when even under high step-up applications, reducing voltage and current stresses significantly. Moreover, since both main and auxiliary switches can be turned on with zero voltage switching, switching loss can be reduced and conversion efficiency therefore can be improved significantly. A 200 W prototype of the proposed boost converter was built from which experiment results have shown that efficiency can reach as high as 92% and surge can be suppressed effectively. It is relatively feasible for applications to fuel cell and battery power conversion

A novel three-phase high-power soft-switched DC/DC converter for low-voltage fuel cell applications

Abstract: An efficient dc/dc converter is needed as the interface between a low-voltage fuel cell source and a high-voltage bus for inverter operation. In this paper, a three-phase transformer-isolated dc/dc converter utilizing phase-shift (PS) modulation is proposed. The converter must be able to boost the voltage significantly and operate at current levels above 240 A on the source side. Key features of the proposed converter include reduced transformer turns ratio by a factor of two while maintaining the same output voltage, reduced size of passive components including output filter and input dc bus capacitor using three-phase interleaving, eliminated inductor current ripple at PS angles above 120/spl deg/, and achieved soft switching over a wide load range without auxiliary circuitry. The proposed converter has been analyzed, simulated, and implemented in hardware. An efficiency of above 96% was achieved using the prototype unit. Experimental results were used to verify all designs and analyses.

Power budgeting of a multiple-input buck-boost converter

Abstract: The use of a multiple-input buck-boost converter for budgeting power between different energy sources is discussed. It is shown mathematically that the idealized converter can accommodate arbitrary power commands for each input source while maintaining a prescribed output voltage. Power budgeting is demonstrated experimentally for a real converter under various circumstances, including a two-input (solar and line-powered) system. A closed-loop control example involving simultaneous tracking of output voltage and set-point tracking of the solar array shows that an autonomous system is realizable.

High-efficiency DC/DC converter with high voltage gain

Abstract: A high-efficiency converter with high voltage gain applied to a step-up power conversion is presented In the proposed strategy, a high magnetising current charges the primary winding of the coupled inductor, and the clamped capacitor is discharged to the auxiliary capacitor when the switch is turned on In contrast, the magnetising current flows continuously to boost the voltage in the secondary winding of the coupled inductor, and the voltages across the secondary winding of the coupled inductor, the clamped capacitor and the auxiliary capacitor are connected in series to charge the output circuit Thus, the related voltage gain is higher than in conventional converter circuits Moreover, this scheme has soft-switching and voltage-clamped properties, ie the switch is turned on under zero-current switching and its sustainable voltage is comparatively lower than the output voltage, so that it can select low-voltage low-conduction-loss devices and there are no reverse-recovery currents within the diodes in this circuit In addition, closed-loop control methodology is utilised in the proposed scheme to overcome the voltage drift problem of the power source under the load variations As a result, the proposed converter topology can promote the voltage gain for a conventional boost converter with a single inductor, and deal with the problem of the leakage inductor and demagnetisation of the transformer for a coupled-inductor-based converter Some experimental results via examples of a proton exchange membrane fuel cell power source and a traditional battery are given to demonstrate the effectiveness of the proposed power conversion strategy

A novel winding-coupled buck converter for high-frequency, high-step-down DC-DC conversion

Abstract: This paper analyzes the fundamental limitations of the buck converter for high-frequency, high-step-down dc-dc conversion. Further modification with additional coupled windings in the buck converter yields a novel topology, which significantly improves the efficiency without compromising the transient response. An integrated magnetic structure is proposed for these windings so that the same magnetic cores used in the buck converter can be used here as well. Furthermore, it is easy to implement a lossless clamp circuit to limit the device voltage stress and to recover inductor leakage energy. This new topology is applied for a 12V-to-1.5V/25A voltage regulator module (VRM) design. At a switching frequency of 2MHz, over 80% full-load efficiency is achieved, which is 8% higher than that of the conventional buck converter.

A converter circuit and technique for increasing the output efficiency of a variable power source

Abstract: The present invention provides a converter circuit (300) and accompanying switch mode power conversion (315) technique to efficiently capture the power generated from a solar cell array (210) that would normally have been lost, for example, under reduced incident solar radiation. In an embodiment of the invention, the converter circuit generates an output current from the solar cell power source using a switch mode power converter. A control loop is closed around the input voltage to the converter circuit and not around the output voltage. The output voltage is allowed to float, being clamped by the loading conditions. If the outputs from multiple units are tied together, the currents will sum. If the output(s) are connected to a battery (220), the battery's potential will clamp the voltage during charge. This technique allows all solar cells in an array that are producing power and connected in parallel to work at their peak efficiency.

New zero-voltage-switching phase-shift full-bridge converter with low conduction losses

Abstract: A new zero-voltage-switching (ZVS) phase-shift full-bridge (PSFB) converter with low conduction losses is proposed. It is based on the PSFB converter with series-connected two transformers, which features wide ZVS ranges. By adding a capacitor, the proposed converter overcomes the disadvantage of the based converter, such as the high circulating energy. Furthermore, the turns ratio of the transformers can be increased as well. Therefore, high efficiency of the proposed converter can be achieved. Operational principles and experimental results for a 100-W (5 V, 20 A) prototype are presented to validate the proposed converter.

A 1-V integrated current-mode boost converter in standard 3.3/5-V CMOS technologies

Abstract: A 1-V integrated CMOS current-mode boost converter implemented in a standard 3.3/5-V 0.6-/spl mu/m CMOS technology (V/sub TH//spl ap/0.85 V), providing power-conversion efficiency of higher than 85% at 100-mA output current, is presented in this paper. The high-performance boost converter is successfully developed due to three proposed low-voltage circuit structures, including an inductor-current sensing circuit for current-mode operation with accuracy of higher than 94%, a precision V-I converter for compensation-ramp generation in current-mode control, and a VCO providing supply-independent clock and ramp signals. Moreover, a proposed startup circuit enables proper converter startup within a sub-1-V supply condition.

An improved boost converter with coupled inductors and buck-boost type of active clamp

Abstract: This paper proposes an improved boost converter with coupled inductors and buck-boost type of active-clamp feature, PWM control and zero-voltage switching in both main and auxiliary switches. In the converter, the active-clamp circuit is used to eliminate voltage spike induced from the leakage inductor of the coupled inductors. The active switch of the converter can still sustain a proper duty cycle when it operates with a high step-up voltage ratio, reducing voltage stress significantly. A set of passive-clamping circuit is adopted to eliminate undesired resonance between leakage inductor of the coupled inductors and stray capacitor of the boost diode, recovering trapped energy. Thus, conversion efficiency can be improved significantly. A 200 W prototype of the proposed boost converter was built from which experimental results have shown that efficiency can reach as high as 92% and surge can be suppressed effectively.

Dual buck-boost converter with single inductor

Abstract: A dual output buck-boost power converter operates with a single inductor to achieve high efficiency with automatic or inherent load balancing. Switches associated with the opposite polarity outputs are driven based on feedback signals, with one feedback signal being a reference voltage and another feedback signal being related to an opposite polarity output. The opposite polarity feedback signal is provided to a comparator with a reversed polarity to achieve a simple balanced control that maintains polarity outputs. The power converter delivers power to each output with each switching cycle and uses a single inductor to achieve high efficiency performance.

Analysis of Double Step-Down Two-Phase Buck Converter for VRM

Abstract: A novel two-phase buck converter suitable to apply the power supplies for MPU is proposed Compared to conventional two-phase buck converter, the proposed converter essentially has double step-down ratio as Eo/Ei = D/2 and high efficiency is realized by reducing the switching loss of the switching elements In addition the current ripple of the output smoothing capacitor is improved to the same value as that of conventional four-phase buck converter Moreover the current unbalance between two inductors in each phase is removed automatically without any current sensing means The above fine characteristics are simply achieved an additional capacitor

Analysis and implementation of full-bridge converter with current doubler rectifier

Abstract: A zero voltage switching DC/DC converter is presented, which gives a stable output voltage and high circuit efficiency. In the adopted DC/DC converter, a full-bridge inverter with phase-shift PWM technique is used to achieve zero voltage switching for active power switches and to regulate the output voltage. To increase the converter efficiency at the transformer secondary side, a current doubler rectifier with the property of one diode conduction drop, frequency doubling in the output capacitor and low current rating in the transformer secondary winding are used in the adopted circuit. The detailed circuit operation, mathematical analysis and design example of the converter are presented. The measured full-load efficiency of a 100 kHz experimental prototype was higher than 92%. Experimental results are presented to verify the performance of the adopted circuit.

A quasi-resonant quadratic boost converter using a single resonant network

Abstract: This paper presents a quadratic boost converter using a single quasi-resonant network to reach soft commutation. A resonant inductor, a resonant capacitor, and an auxiliary switch form the resonant network and the main switch operates in a zero-current-switching way. A complete analysis of this converter is presented. According to the simulation and experimental results, this quadratic boost converter provides a larger conversion ratio than that provided by the conventional boost converter (for a given duty ratio D), and presents optimum performance, which operates with soft-switch commutation using a single resonant network.

Open-loop power-stage transfer functions relevant to current-mode control of boost PWM converter operating in CCM

Abstract: This paper presents the analysis of open-loop power-stage dynamics relevant to current-mode control for a boost pulsewidth-modulated (PWM) dc-dc converter operating in continuous-conduction mode (CCM). The transfer functions from input voltage to inductor current, from duty cycle to inductor current, and from output current to inductor current are derived. The delay from the MOSFET gate drive to the duty cycle is modeled using a first-order Pade/spl acute/ approximation. The derivations are performed using an averaged linear small-signal circuit model of the boost converter for CCM. The transfer functions can be used in modeling the complete boost PWM converter when current-mode control is used. The theory was in excellent agreement with the experimental results, enforcing the validity of the transfer functions derived.

A three-phase step-up DC-DC converter with a three-phase high frequency transformer

Abstract: This paper presents a new 3-phase step-up DC-DC converter with a 3-phase high frequency isolation transformer. This converter was developed for industrial applications where the DC input voltage is lower than the output voltage, for instance in, installations fed by battery units, photovoltaic arrays or fuel cell systems. The converter's main characteristics are: reduced input ripple current, step-up voltage, high frequency isolating transformer, reduced output voltage ripple due to three pulsed output current and the presence of only three actives switches connected at the same reference, this being a main advantage of this converter. By means of a specific switch modulation, the converter allows two operational regions. Theoretical expressions and experimental results are presented for a 6.8 kW prototype, operating in region R2 and for a 3.4 kW prototype operating in region R3, both in continuous conduction mode.

Buck-boost voltage converter

Abstract: An input switching unit selectively couples a first terminal of an inductor with an input voltage and a ground potential. An output switching unit selectively couples a second terminal of the inductor with an output voltage and the ground potential. A first pulse generating circuit generates a first pulse signal with a first duty ratio, which is modulated in response to the output voltage. A second pulse generating circuit generates a second pulse signal with a second pulse signal with a second duty ratio, which is a constant larger than zero and smaller than one. When the first duty ratio is larger than a predetermined threshold duty ratio, a mode control circuit applies the first pulse signal to control one of the input switching unit and the output switching unit and applies the second pulse signal to control another of the input switching unit and the output switching unit.

A three-level converter and its applicationto power factor correction

Abstract: The first part of this paper introduces a novel three-level dc-dc converter topology. It is shown that a floating capacitor connected across the clamping diodes of a conventional three-level converter enables phase-shift control while retaining zero voltage switching. Design constraints and experimental results are shown for a 6-kW, 100-kHz dc-dc prototype. The second part of the paper discusses the same three-level topology operated as a single-stage front-end converter. In this application, the converter realizes power factor correction and dc output voltage regulation. To ensure low harmonic distortion, the input currents are operated in discontinuous conduction mode, and the performance, including soft switching, is also verified on a 3-kW, 50-kHz ac-dc converter.

Single inductor multiple-input multiple-output switching converter and method of use

Abstract: A single inductor multiple-input multiple-output (SI-MIMO) switching converter time-multiplexes different input power sources through only one inductor to provide multiple regulated output voltages, which can be used to power up different blocks of a portable electronic device (or whatever else it is used for) and at the same time to charge up a rechargeable battery. Power multiplexing is achieved by input switches that are also the switching elements of the switching converter, thus eliminating an additional power multiplexer.

Determining dead times in switched-mode DC-DC converters

Abstract: Systems, methods, and apparatuses are disclosed for determining dead-times in switched-mode DC-DC converters with synchronous rectifiers or other complementary switching devices. In one embodiment, for example, a controller for a DC-DC converter determines dead-times for switching devices of a synchronous rectifier or other complementary switching device of the converter in which a dead-time is derived from an output voltage or current that is already sensed and used in the output regulation of the converter. In another embodiment, a controller is provided for controlling a switched-mode DC-DC converter comprising a pair of power switches. The controller comprises an input, a reference generator, a comparator, a compensator, a dead-time sub-controller, and a modulator. In another embodiment, the controller may adjust the dead-times during the operation of the converter to adjust periodically and/or in response to changes in operating conditions. In addition, methods of determining dead-times of control signals for a switched-mode DC-DC converter comprising a pair of power switches and of controlling a DC-DC converter are also disclosed.

Zero-voltage-switching PWM hybrid full-bridge three-level converter

Abstract: This paper proposes a zero-voltage-switching (ZVS) pulse-width modulation (PWM) hybrid full-bridge three-level converter, which has a three-level leg and a two-level leg. The switches of the three-level leg sustain only the half of the input voltage, and they can realize ZVS in a wide load range. The switches of the two-level leg sustain the input voltage, and they can realize ZVS with the use of the resonant inductance. The secondary rectified voltage is a three-level waveform having lower high-frequency content compared with that of the traditional full-bridge converters, which can reduce the output filter, and as a result, the dynamic response of the converter is improved. The voltage stress of the rectifier diode is reduced also. The input current of the converter has quite little ripple, so the input filter can also be significantly reduced. The operation principle of the proposed converter is analyzed and verified by the experimental results.

A high-efficiency, dual-mode, dynamic, buck-boost power supply IC for portable applications

Abstract: Integrated power supplies are critical building blocks in state-of-the-art portable applications, where they efficiently and accurately transform a battery supply into various regulated voltages, as required by their loads. This paper presents a novel low voltage, dual-mode, buck-boost converter IC targeted for dynamic supplies of linear RF power amplifiers (PAs) in wireless handsets. Maintaining high efficiency of the converter over a wide loading range is critical for improving battery life in such systems. The use of a novel, supply-voltage adaptive, on time control for pulse-frequency-modulation (PFM) mode achieves an accurate output ripple voltage, not to mention higher efficiency under light loads. In the high-power mode, the converter is operated in a modified pulse-width-modulation (PWM) control, where its operation is changed adaptively between buck, buck-boost, and boost regions, thereby saving unnecessary switching losses. Appropriate circuit topologies are developed and designed to overcome the challenges of a low supply voltage environment requiring a wide dynamic range converter. The converter is designed and simulated using a 0.5-/spl mu/m n-well CMOS process for a supply voltage range of 1.4-4.2 V, which is compatible with state-of-the-art Li-ion batteries (2.7-4.2 V), and alternate power sources, e.g. NiCd and NiMH batteries. Simulation results show that the converter generates an output voltage of 0.5-5 V while delivering up to 0.5 A of load current with a maximum ripple of 40 mV. The converter exhibits efficiency of 60-93% in PWM mode and 80% in PFM mode. A 0.9-1 V transient control-step response in PWM mode, which refers to a change in output voltage of 4.5-5 V, from an input supply of 1.4 V, is less than 200 /spl mu/sec.

Light loading control circuit for a buck-boost voltage converter

Abstract: A light loading control circuit operates a switching circuit of a buck-boost voltage converter alternately in a plurality of phase cycles and a sleep period. Each phase cycle has a rising phase, a falling phase, and a maintaining phase. In the rising phase, the switching circuit is operated to increase an inductor current. In the falling phase, the switching circuit is operated to decrease the inductor current. In the maintaining phase, the switching circuit is operated to keep the inductor current approximately constant. The sleep period prevents two terminals of an inductor from being respectively coupled to two selected from a group consisting of an input voltage, an output voltage, and a ground potential.

Hybrid mode-switched control of DC-DC boost converter circuits

Abstract: This paper has proposed a new switching scheme for controlling dc-dc boost converter circuits. The converter is represented as a hybrid system with three modes of operation. The switching among these modes is governed by the adjustable reference voltage and a reference current which are calculated by an energy balance principle. The scheme has been applied to a realistic converter circuit modeled with various parasitic components. All the specifications related to the ripple voltage, line and load regulation are shown to be achievable by relating them to the switching surfaces, namely a reference voltage and a reference current. The state trajectories have been shown to reach a hybrid limit cycle already proved to be super-stable from consideration of chaos. Numerical results clearly bring out the advantages of the proposed control scheme.

A passive auxiliary circuit achieves zero-voltage-switching in full-bridge converter over entire conversion range

Abstract: A passive auxiliary circuit is proposed to achieve zero-voltage-switching (ZVS) over the entire conversion range in a full-bridge (FB) pulse-width modulated (PWM) converter (FBZVS converter) with minimum conduction loss penalty. The stored energy in the auxiliary circuit is minimal under the full-load condition. It increases progressively as the load current decreases. The proposed auxiliary circuit is passive, simple and can be viewed as an add-on to the conventional FBZVS converter. The principle of operation is described and the performance is demonstrated on a 100 kHz, 500 W prototype.