Showing papers on "Buck–boost converter published in 2000"

Steady-state analysis of an interleaved boost converter with coupled inductors

Abstract: Boost converters are widely used as power-factor corrected preregulators In high-power applications, interleaved operation of two or more boost converters has been proposed to increase the output power and to reduce the output ripple A major design criterion then is to ensure equal current sharing among the parallel converters In this paper, a converter consisting of two interleaved and intercoupled boost converter cells is proposed and investigated The boost converter cells have very good current sharing characteristics even in the presence of relatively large duty cycle mismatch In addition, it can be designed to have small input current ripple and zero boost-rectifier reverse-recovery loss The operating principle, steady-state analysis, and comparison with the conventional boost converter are presented Simulation and experimental results are also given

Actively clamped bidirectional flyback converter

Abstract: An actively clamped bidirectional flyback converter is proposed. The converter's operation is examined in detail. All switches in the converter have zero-voltage-switching characteristics. A low-frequency behavior model and small-signal transfer functions are derived. It is found that the flow of current is directly under the control of the duty cycle, and that the transformer's leakage inductance has a significant effect on the control characteristic of the converter. It is expected that such bidirectional converters will find wide applications in the interconnection of multiple sources of DC power to a common bus (e.g., in a DC uninterruptible power supply). Simulation and experiment results are also presented.

Buck or boost power converter

Abstract: A buck or boost (BOB) power converter circuit. A buck converter is cascaded with a boost converter to form a buck or boost circuit ( 20 ). The BOB converter is controlled by a controller ( 26 ) such that only the buck or boost converter is operating at any given time. A reference signal V ref can be applied to the controller ( 26 ) such that the output voltage from the converter closely tracks the reference signal. Positive and negative ramp signals are generated and an error feedback signal is compared with the ramp signals to control the output in accord with V ref . This is useful in application of the output voltage as the power supply to an RF Power Amplifier ( 16 ) so that the reference signal can represent the envelope of a signal to be transmitted and the RF PA ( 16 ) can operate at high efficiency.

Power converter mode transistioning method and apparatus

Abstract: A method and apparatus are provided for transitioning a power converter between a switched mode of operation and a linear regulator mode of operation. The power converter operates according to one or more intermediate modes of operation in which the switched mode and linear regulator modes cooperate to produce a shared power converter output. The power converter transitions between the various modes of operation in response to changes in circuit parametric conditions as defined by a series of state transition diagrams. Power converter output voltage is maintained in regulation during all modes of operation and transitions therebetween. The method and apparatus includes an integrated device that may be operated as a switch or a variable resistance device.

Operating a power converter at optimal efficiency

Abstract: A power converter control system is provided which combines a pulse train regulation control technique with a pulse train optimization technique, to control the output level of the power converter, while maintaining optimal performance for other power converter parameters. The power converter control system describe herein provides versatility not previously available in power converter control systems by providing features such as quasi-resonant mode control, discontinuous mode control, and/or power factor correction. A pulse optimizer adjusts or customizes, for example, the ON time, duty cycle or frequency of pulse train pulses output by a pulse generator. The adjusted pulses are gated by a pulse rate controller to selectively actuate a power switch, thereby regulating the output power level and optimize the overall performance of the power converter.

Power-factor-corrected single-stage inductive charger for electric-vehicle batteries

Abstract: A novel power-factor-corrected single-stage AC-DC converter for inductive charging of electric vehicle batteries is introduced. The resonant converter uses the current-source characteristic of the series-parallel topology to provide power factor correction over a wide output power range from zero to full load. Some design guidelines for this converter are outlined. An approximate small-signal model of the converter is also presented Experimental results verify the operation of the new converter.

A zero voltage switching three-level DC/DC converter

Abstract: A novel zero voltage switching (ZVS) three-level (TL) DC/DC power converter is presented in this paper. The converter uses a flying capacitor in the primary side to allow operation with phase-shift control and in this way achieves ZVS for all the switches. The principle of operation of the converter is analyzed and verified on a 6 kW, 100 kHz experimental prototype. Additionally, this paper presents improvement of the proposed converter by using different ZVS techniques.

High-power-density MHz-switching monolithic DC-DC converter with thin-film inductor

Abstract: In this paper, we report the newly developed DC-DC converter IC termed monolithic DC-DC converter, in which a thin-film inductor and power IC are integrated, and describe the micro DC-DC converter module utilizing this IC. The thin-film inductor used in the monolithic DC-DC converter was fabricated by RF sputtering, photosensitive polyimide lithography and electro-plating onto the power IC. The micro DC-DC converter module using the monolithic DC-DC converter achieved power density of 5.6 W/cm/sup 3/ at output power of 1 W and maximum efficiency of 83.3% at switching frequency of 3 MHz.

Topology and control method for power factor correction

Abstract: In a power factor corrected AC-to-DC power supply system, a DC-to-DC power converter is coupled to the output of an AC-to-DC power converter in order to produce a regulated DC output signal from a rectified AC input signal. The AC-to-DC power converter and the DC-to-DC power converter each includes a switch for controlling the operation of their respective power converter. The AC-to-DC converter includes an inductor. The system provides power factor correction for minimizing harmonic distortion by including a controller that receives the regulated DC output voltage as a feedback signal, and in response, produces a series of drive pulses having predetermined constant duty cycle. These pulses are simultaneously fed to each switch, to operate the respective converters alternately between ON and OFF states. When the AC-to-DC converter is driven by a fixed duty cycle of the series of pulses, power factor correction is improved since the current flowing through the inductor is substantially proportional to the waveform of the rectified AC input signal. By preselecting the value of the inductor, the AC-to-DC converter is operable in a discontinuous mode when the instantaneous rectified AC input signal is low and in a continuous mode when the instantaneous rectified AC input signal is high.

High power factor rectifier based on buck converter operating in discontinuous capacitor voltage mode

Abstract: The buck converter with LC input filter operating in discontinuous capacitor voltage mode has inherent power factor correction properties and continuous input current. The paper presents a detailed analysis of the converter operating in this mode, leading to design criteria. Finally, experimental results for a 48 V/sub dc//100 W converter are presented.

Flyback as LED driver

Abstract: The invention relates to a circuit arrangement for operating a semiconductor light source, comprising input terminals for connecting a supply voltage, input filter means, a converter provided with a switching element having a control circuit, and provided with inductive means, and output terminals for connecting the semiconductor light source. The switching element is periodically driven into conduction for a period t on . According to the invention, the converter is formed by a flyback converter, and the inductive means are formed by a transformer, and the control circuit controls the t on .

Multiple voltage output buck converter with a single inductor

Abstract: A low cost, multiple output buck converter is provided using a single inductor, a single pulse width modulator integrated circuit, and two MOSFETs plus one additional MOSFET and capacitor for each voltage output.

Isolated interleaved-phase-shift-PWM DC-DC ZVS converters

Abstract: This paper presents a new isolated DC-DC zero-voltage-switching (ZVS) converter, which is composed of two half-bridge converters associated in series operating at constant frequency. The converter can be seen as an alternative to the ZVS-phase-shift full-bridge DC-DC converter for high-voltage applications. The paper proposes a new command strategy, named interleaved phase shift, which allows equalization of the input capacitor voltage, where each capacitor shares one-quarter of the total input voltage. Due to phase-shift modulation, the current is equally shared among main switches, reducing the converter conduction losses, when compared with conventional pulsewidth modulation. Furthermore, the input capacitors voltage oscillations are reduced due to load variations, as well as due to input DC-bus 120 Hz ripple. Just as with a ZVS-phase-shift full-bridge converter, the proposed converter achieves ZVS in a wide load range, as a function of the transformer leakage inductance. The paper describes the analysis, operating principles, and design procedure for the proposed converter. Experimental results from a 1.5 kW prototype converter operating at 100 kHz with isolated 60 V/25 A output are presented to validate the theoretical analysis and to demonstrate the performance of the proposed converter.

An improved ZVT PWM boost converter

Abstract: This paper proposes an improved ZVT-PWM boost converter. The main switch of the conventional ZVT-PWM converter is always switched at zero voltage. But the auxiliary switch is turned-off with switching loss due to hard switching condition. Therefore, the proposed converter reduces the turn-off switching loss of the auxiliary switch by using an additional circuit. All of the losses for the switches are minimized, and high power density system can be realized.

Quasiperiodicity and chaos in the dc–dc buck–boost converter

Abstract: This paper is concerned with the study of nonlinear phenomena in a closed loop voltage-controlled DC–DC Buck–Boost converter when suitable parameters are varied. The dynamics is analyzed using both the continuous-time model and the numerically computed stroboscopic map. The analysis of the one-dimensional bifurcation diagram shows that Neimarck–Sacker bifurcation occurs at certain values of the parameters. Phase-locking periodic windows, the period-adding sequence, and transition from quasiperiodicity to period-doubling via torus breakdown are also obtained. The two-dimensional bifurcation diagram is carefully computed. This shows that phase-locking orbits produce so-called Arnold tongues in the parameter space. It is shown that the winding number plotted as a function of the bifurcation parameter is a devil's staircase. As typically occurs in general circle maps, the fine structures of the Arnold tongues and the devil's staircase show self-similarity.

Controller arrangement for boost converter systems sourced from solar photovoltaic arrays or other maximum power sources

Abstract: Conventional power converter systems, such as boost converters, derive their input from sources that may be considered to have negligible output impedances. As such, the use of quite simple conventional control algorithms suffice to give acceptable performance. When the output impedance of the source to such a converter is no longer negligible, and moreover if the source has a markedly nonlinear output impedance, the simple conventional algorithms will no longer be adequate to satisfy the control requirements of the converter. The effect of driving such a converter from a type of source, for example a photovoltaic array which has a point of maximum power delivery within the operating range is discussed, as is the impact that the use of such a source has upon the control requirements of the converter. A novel control arrangement, which includes a complete embedded maximum power tracker, is then presented together with results validating the proposed controller.

A linear resistance-to-time converter with high resolution

Abstract: A resistance-to-time converter employing a bridge amplifier, an integrator and a comparator is described. While possessing a resolution and linearity of the same order as that of a recently reported resistance-to-frequency converter, the present circuit has the advantage of grounded detecting resistance. Further, no compensation arrangement need be incorporated for maintaining wide-range linearity.

A Linear Resistance-To-Time Converter with High

Abstract: A resistance-to-time converter employing a bridge amplifier, an integrator and a comparator is described. While possessing a resolution and linearity of the same order as that of a recently reported resistance-to-frequency converter, the present circuit has the advantage of grounded detecting resistance. Further, no compensation arrangement need be incorporated for maintaining wide-range linearity.

Development of a multistage current-controlled switched-capacitor step-down DC/DC converter with continuous input current

Abstract: This paper presents the design and analysis of a low-profile multistage current-controlled switched-capacitor (SC) step down DC/DC converter. The converter not only exhibits all advantages of classical SC converters, but also features good regulation capability and continuous input current waveform, resulting in low conducted electromagnetic interference with the supply network. The concept of energy transfer is achieved by paralleling the input and output of two step-down converter cells and operating them in antiphase. The voltage conversion ratio is determined by controlling the charging trajectories of the capacitors in each cell. As it is unnecessary for the circuit to use any inductive elements, possibilities of integrated circuit fabrication and high power density are promising. By applying the state-space averaging technique, a third-order state-space model for an n-stage converter is derived. Static and small-signal dynamic behaviors of the converter are investigated. A 70 W 48 V/12 V converter is implemented. Analytical predictions are verified with experimental measurements.

Apparatus for converting a direct current into an alternating current

Abstract: An apparatus for converting a direct current into an alternating current comprises a direct-current converter (1) having an input and an output, which direct-current converter is continuously controllable, a capacitor (C), and a control unit (4) for controlling the direct-current converter. The apparatus furthermore comprises a second direct-current converter (2) having an input and an output, wherein the input of the second direct-current converter is connected in parallel to the input of the first direct-current converter and the outputs of the first and the second direct-current converter are connected in series. An unfolding bridge (3) is connected to the series-connected outputs of the direct-current converters, whilst the capacitor is connected to the output of the second direct-current converter. Furthermore, a first switching element (S 1 ) is provided for interrupting the series connection and a second switching element (S 2 ) is provided for connecting the unfolding bridge to the output of the first direct-current converter in the interrupted state of the series connection. The control unit controls at least the first switching element in dependence on the voltage V c across the capacitor and the voltage V abs across the unfolding bridge, in such a manner that the first switching element is opened when V abs < V c .

Unique power supply architecture with cascaded converters for large input-to-output step-down ratio

Abstract: A power supply having a transformer-coupled power converter cascaded with a buck power converter. The transformer-coupled power converter operates in a free-running mode at a nearly 100% maximum duty cycle to convert an input voltage to an intermediate voltage. The buck power converter produces a regulated output voltage from the intermediate voltage. The power supply further includes a pulse width modulation (PWM) controller employing leading-edge modulation of complementary control signals used to control buck switches in the buck converter. The PWM controller is synchronized to primary-side free-running switches of the transformer-coupled power converter by a synchronization signal that is fed-forward across an isolation boundary via a signal transformer. The power supply also may also employ a soft-switching technique to reduce switching losses.

Flyback converter as led driver

Abstract: The invention relates to a circuit arrangement for operating a semiconductor light source, comprising input terminals for connecting a supply voltage, input filter means, a converter provided with a switching element having a control circuit, and provided with inductive means, and output terminals for connecting the semiconductor light source. The switching element is periodically driven into conduction for a period ton. According to the invention, the converter is formed by a flyback converter, and the inductive means are formed by a transformer, and the control circuit controls the ton.

Converter circuit having control means with capability to short-circuit converter output

Abstract: A converter circuit has a reactor connectable to an AC power supply. It further has a PWM converter circuit connected to the reactor, the PWM converter circuit including a high speed diode, a rectifier diode and a switching element connected in parallel to the rectifier diode. The converter circuit further has an input current detector for detecting an input current of the PWM converter circuit, a DC voltage level detector for detecting an output voltage of the PWM converter circuit, a voltage polarity detector connected to the AC power supply, and a control device. The control device measures a variation period of the output voltage measured by the voltage level detector to judge a power supply frequency. It then controls the PWM converter circuit based on a power supply frequency judgement result, a detection result from the voltage level detector, an input current detected by the input current detector, and an output voltage detected by the DC voltage detector.

Robust PID control of a buck-boost DC-AC converter

Abstract: This paper presents the design of a robust PID controller for a four quadrant DC to AC switched mode inverter, using a buckboost DC to DC converter. The designed controller is intended to decrease the total harmonic distortion (THD) in the output voltage against sudden load changes. The proposed robust controller is based in a classical two degree of freedom approach. The controller performance was tested by computer simulations.

Regenerative braking for an electric vehicle using ultracapacitors and a buck-boost converter

Abstract: The objective of this study was to allow higher accelerations and decelerations of the electric vehicle with minimal loss of energy, as well as minimal degradation of the main battery pack. The authors simulated an ultracapacitor bank control system, which used an insulated gate bipolar transistor (IGBT) Buck-Boost converter. The Buck side was connected to the main battery while the Boost side was connected to the ultracapacitor. The battery voltage, state of charge, car speed, instantaneous currents in both terminals, and the actual voltage of the ultracapacitor were measured by the system. The generation of the Pulse Width Modulation (PWM) switching pattern of the IGBT by a microcomputer control allowed all the variables to be considered. The capacitor is kept discharged when the vehicle operates at high speeds, and the capacitor bank remains charged at full voltage if the vehicle does not run. Medium voltages are maintained at medium speeds to permit accelerations and decelerations. Therefore, the real time situation of the vehicle is indicated by battery voltage. During regenerative braking, the battery voltage goes up and the kinetic energy of the vehicle is stored in the ultracapacitor, while the voltage goes down during acceleration (energy retrieved from the ultracapacitor). The current levels are kept in the maximum range by the measurement of the current on both sides. At specific values, the battery state of charge is used to change the voltage level of the ultracapacitor. An IGBT controlled resistor was also integrated in the converter to permit a drop of energy if required. The system will be installed in a Chevrolet LUV truck, which has already been converted to an electric vehicle. refs., tabs., figs.

DC-DC converter, with duty cycle comparison for a dual mode back boost converter

Abstract: A converter for converting an input voltage (U i ) into an output voltage (U 0 ). The converter has several modes of operation. The converter can, for example, operate in an up-conversion mode, a down-conversion mode, or a window conversion mode. The converter has at least one switch (S 1 -S 4 ) for controlling the converter so as to obtain a desired value of the output voltage (U 0 ) in the up-conversion mode and in the down-conversion mode. This is achieved by changing the duty cycle of a binary signal (BS) which controls the switch (S 1 -S 4 ). The converter further includes means (DMNS) for detecting the duty cycle of the binary signal (BS). This duty cycle is compared with a reference duty cycle (RFDCCL). The result of this comparison is used for deciding whether or not to change over from the up-conversion mode (or the down-conversion mode) to the window conversion mode. In the window conversion mode each switch (S 1 -S 4 ) in the converter is permanently closed or open. In the window conversion mode the output voltage (U 0 ) is roughly equal to the input voltage (U i ). The converter remains in the window conversion mode as long as the output voltage (U 0 ) is within a given voltage window (range). However, if the output voltage (U 0 ) has become too low, the converter changes over from the window conversion mode to the up-conversion mode. In a similar way, the converter changes over from the window conversion mode to the down-conversion mode when the output voltage (U 0 ) has become too high.

Dual voltage automotive electrical system with sub-resonant DC-DC converter

Abstract: An improved dual voltage automotive electrical system in which low voltage loads (19) are powered by a series resonant DC-DC converter (18) operated at a fixed switching frequency below the resonant frequency of its tank circuit. With this arrangement, the converter (18) provides a fixed conversion ratio from the regulated upper system voltage (Vin), and operates with the beneficial attributes of zero current switching and inherent overload protection. In a first embodiment, a transformer (T2) inductively couples the converter tank circuit to the low voltage loads (19), providing full input/output galvanic isolation. In a second embodiment, the converter (18) is configured so that a portion of the power supplied to the low voltage loads (18) is directly coupled from the upper system voltage source (Vin), with the remaining portion being coupled through the converter (18). In either embodiment, the accuracy of the conversion ratio and its load current independence are enhanced by a compounding coil (Ta, Tb) having a load current dependent inductance coupled to the tank circuit.

Series resonant converter comprising a control circuit

Abstract: The invention relates to a series resonant converter ( 1 ) comprising a control circuit ( 8 ) for controlling the output voltage of the converter. To improve the behavior of the converter, it is proposed that the control circuit ( 8 ) is provided for processing a first actual value (U out ), which depends on the respective converter output voltage (u out (t)) and for processing a second actual value (U C ), which depends on the respective current (i res (t)) flowing through the series resonant circuit elements (C, L, R) of the converter ( 1 ), and that the control circuit ( 8 ) is provided for delivering a correcting variable (u) determining the scanning ratio of a pulse-width modulated voltage (u pwm (t)) delivered to the series resonant circuit of the converter.

Active clamp for isolated power converter and method of operating thereof

Abstract: A secondary active clamp for a power converter, a method of actively clamping energy of the power converter and a power converter employing the clamp or the method. The power converter has a primary switching circuit coupled to a primary winding of an isolation transformer and a rectifier coupled to a secondary winding of the isolation transformer. In one embodiment, the clamp includes (1) an inductor coupled in series with a freewheeling diode of the rectifier and (2) a series-coupled capacitor and clamping switch coupled in parallel with the inductor. The series-coupled capacitor and clamping switch cooperate with the inductor to mitigate adverse effects of a reverse recovery phenomenon associated with the rectifier and to effect substantially zero voltage switching of a power switch of the primary switching circuit.

New space-vector control strategies for three-phase step-up/down AC/DC converter

Abstract: In this paper, an equivalent DC duty cycle for the generalized zero-voltage space vectors is proposed such that control of the three-phase AC part and the DC part of the converter circuit can be integrated to achieve the ideal characteristic of single-stage step-up/down AC/DC converter. Depending upon how many modes are chosen and which class of generalized zero-voltage space vectors is selected to increase the equivalent DC duty cycle, different control strategies can be obtained. It is seen that not only the control of the six switches is simplified but also the deadtime circuit for avoiding short circuit of the same arm can be eliminated for the proposed converter. In addition, some guidelines for selecting the LC parameters are described briefly and experimental results given for verifying the validity of the proposed converter.