Showing papers on "Flyback converter published in 2000"

A topology survey of single-stage power factor corrector with a boost type input-current-shaper

Abstract: A topological review of the single stage power factor corrected (PFC) rectifiers is presented in this paper. Most of reported single-stage PFC rectifiers cascade a boost type converter with a forward or a flyback DC-DC converter so that input current shaping, isolation, and fast output voltage regulation are performed in one single stage. The cost and performance of a single-stage PFC converters depend greatly on how its input current shaper (ICS) and the DC-DC converter are integrated together. For the cascade connected single-stage PFC rectifiers, the energy storage capacitor is found in either series or parallel path of energy flow. The second group appears to represent the main stream. Therefore, the focus of this paper is on this group. It is found that many of these topologies can be implemented by combining a 2-terminal or 3-terminal boost ICS cell with DC-DC converter along with an energy storage capacitor in between. A general rule is observed that translates a 3-terminal ICS cell to a 2-terminal ICS cell using an additional winding from the transformer and vice versa. According to the translation rule, many of reported single-stage PFC topologies can be viewed as electrically equivalent to one another. Several new PFC converters were derived from some existing topologies using the translation rule.

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.

White light-emitting-diode lamp driver based on multiple output converter with output current mode control

Abstract: A white light-emitting-diode array driver circuit with a multiple output flyback (or forward) converter with output current mode control. The circuit comprises a power supply source and a transformer. The transformer has a primary winding coupled to, and configured to receive current from, the power supply, and a plurality of secondary windings coupled to the primary winding. The circuit also comprises a plurality of light-emitting-diode arrays, wherein each light-emitting-diode array is coupled to one of the secondary windings. A main controller is coupled to a first of the light-emitting-diode arrays and is configured to control a flow of current to the primary transformer winding. The circuit also comprises a plurality of secondary controllers, each of which are coupled to another of the light-emitting-diode arrays. In addition, each of the secondary controllers are configured to control a flow of current to its corresponding light-emitting-diode array. According to one embodiment of the invention, each of the light-emitting diodes has a resistor coupled to its cathode terminal. An output signal of each resistor is transmitted to the respective controller and is employed to determine the appropriate current flow to the light-emitting-diode array. The circuit may be configured as either a flyback converter, wherein the primary transformer winding is wound in the opposite direction of the secondary transformer windings, or as a forward converter, wherein the primary transformer winding is wound in the same direction as secondary transformer windings.

Operation principles of bi-directional full-bridge DC/DC converter with unified soft-switching scheme and soft-starting capability

Abstract: A new bi-directional dual full-bridge DC/DC converter with a unified soft-switching scheme and soft-start capability is proposed in this paper. A simple voltage clamp branch is used to limit transient voltage across the current-fed bridge and realize zero-voltage-switching (ZVS) in boost mode operation, while achieving hybrid zero-voltage/zero-current switching (ZVZCS) for the voltage-fed bridge in buck mode operation. The theory of operations including soft-start-up process is discussed in this paper.

Power electronic transformers for utility applications

Abstract: The concept of realizing a small size "solid-state" transformer has been discussed for some time. A fairly straightforward approach to accomplish size reduction in a transformer feeding a conventional rectifier-inverter system is to introduce an isolated DC-DC converter in the DC link, isolation being provided by a high frequency transformer. So also, several topologies that employ AC-AC converters connected on primary and secondary sides of a high frequency transformer to reduce the size and weight of the magnetic core have been reported in literature. Such AC-AC converters need switches with bi-directional voltage blocking and current carrying capability, which are commonly realized with pairs of gate turn-off devices such as insulated gate bipolar transistors (IGBT). This paper explores the possibilities of employing AC-AC switched mode power converters in combination with reactive elements to realize a chopped AC link, thereby decreasing the required magnetic core size for voltage transformation and isolation. A primary advantage of this approach is that, the static power converter needs only six devices to implement a three-phase electronic transformer, which makes it an economical solution. Operating principles, magnetic design and other practical issues are discussed. Detailed computer simulations accompanied with experimental verification are presented in the paper.

Symmetrical multilevel converters with two quadrant DC-DC feeding

Abstract: In the technology sector of power electronics and control, the multilevel converter technology is still a rather new research area, but the application possibilities in the field of power drives and energy will demand more solutions with this promising technology. In the future, more converter systems will be realized with the multilevel topology. Up to now, multilevel converters have only been used in very particular applications, mainly due to the high costs and complexity of the multilevel converter system. The high costs are due to the fact that the latest technology on semiconductors, magnetic material for inductor and transformer cores and control system technology had to be used. But nowadays new developments in the fields of power semiconductors such as the IGBT, IGCT and perhaps in the future SiC switches as well as improvements of the performance of magnetic cores used in medium frequency transformers will favor the multilevel converters for many other application fields. It can be noted that the industrial trend is moving away from heavy and bulky passive components towards power converter systems using more and more semiconductor elements controlled by powerful processor systems integrating intelligent multi-task control algorithms. The presented work is a contribution to the large field of multilevel converters. It shows a certain kind of multilevel converter in a single phase and a three-phase configuration, called the series-connected four-quadrant converters (SCFQ). The two specialties of the presented converter type are a) that all the multilevel converter steps are fed by an identical DC voltage and b) that every multilevel converter step is realized with an individual AC-DC converter or four-quadrant converter. This type of multilevel converter is called multilevel converter with symmetrical feeding. In this work, a general theoretical development has been done for the use of this multilevel converter type. A special type of DC-DC converter is presented, in order to feed the individual four-quadrant converters of the multilevel converter with a constant DC voltage. All the developments and methods used are based on mathematical expressions. Various simulations using the latest software simulation tools are accomplished and are used to study different cases. The feasibility of the developments is underlined with a series of experimental results with all types of the used converters, which have been realized in the framework of this thesis. The main application for the multilevel converter presented in this work is the frontend power converter in locomotives. Instead of using a heavy low-frequency transformer to reduce the high-voltage from the catenary to a supportable voltage for the semiconductors, a multilevel converter concept is used. The multilevel converter is directly coupled to the catenary. There are many advantages compared to the existing solutions. In the same context, a novel solution of a multilevel converter has been developed for a locomotive usable on different power lines. The converter allows not only the operation on the high AC voltage power line (15kV), but also can be coupled to a medium-voltage DC power line (3kV). Three different configuration types of the locomotive converter have been developed and tested in a complex simulation environment. Besides the locomotive application, there are many more interesting applications for the symmetrical multilevel converter, e.g. in the fields of energy transmission (FACTS, static VAR compensators, electronic high-voltage transformers, etc.) and industrial drives. But certainly in the future with the availability of cheap semiconductors adapted to the needs of the multilevel converter, even more applications in lower power fields will be realized.

AC power supply apparatus with economy mode and methods of operation thereof

Abstract: A power supply apparatus includes an AC input port, an output port, and a bypass circuit that couples the AC input port to the output port. An AC/DC converter circuit, e.g., a rectifier circuit, produces a DC voltage from an AC input voltage at the AC input port. A DC/AC converter circuit, e.g., a current mode controlled inverter, controls current transfer between the output port and the AC/DC converter circuit responsive to a control input such that respective first and second component currents of a current delivered to a load coupled to the output port pass via respective ones of the bypass circuit and the DC/AC converter circuit. The DC/AC converter circuit may be operated such that current passing through the bypass circuit is constrained to be substantially in phase with the AC input voltage. The power supply apparatus may have another mode of operation in which the DC/AC converter circuit exclusively provides power to the output port, and may include an auxiliary DC power supply circuit that provides a DC voltage to the DC/AC converter circuit. Related power supply methods are also discussed.

Charge pump DC/DC converters with reduced input noise

Abstract: A charge pump DC/DC converter with reduced noise at the input voltage source is provided. The present invention includes buck and boost DC/DC converters with added circuitry coupled between the input voltage and the switches which maintains a substantially constant input current on both phases of the charge pump clock. The added circuitry reduces input current variations to provide reduced noise at the input voltage source. Feedback loop circuitry coupled between the output node and the added circuitry varies the current through the switches to control the output current of the DC/DC converter in order to maintain the output voltage at the regulated value. The added circuitry may comprise a variable resistor, current mirror, or current mirrors.

Lossless switching DC to DC converter with DC transformer

Abstract: Soft switching DC-to-DC converter operates at record high efficiency despite its small size and weight and ultra high overload current capability of several times the nominal load current. Such performance is made possible by use of unique magnetic and switching circuits with special properties. Other desirable performance features are provided concurrently such as: zero ripple current on input and output, low conducted and radiated Electromagnetic interference (EMI) noise, as well as low component stresses for increased converter reliability.

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.

Series resonant ZCS-PFM DC-DC converter with multistage rectified voltage multiplier and dual-mode PFM control scheme for medical-use high-voltage X-ray power generator

Abstract: In general, high-voltage DC power supplies employing a variety of high-frequency inverters are implemented for constant value control schemes. In particular, their good transient and steady state performances cannot be achieved under wide load variations for a medical-use high-voltage X-ray generator, ranging from 20 kV to 150 kV in the output voltage and from 0.5 mA to 1250 mA, respectively. A high-voltage DC power supply designed for X-ray power generator applications is considered, which uses a series resonant inverter-linked multistage DC voltage multiplier instead of a conventional high-voltage diode module rectifier connected to the secondary side of a high-voltage transformer. A constant on-time/variable frequency control scheme of this converter operating at zero-current soft switching mode is described. Introducing the capacitor-diode cascaded multistage voltage multiplier, the secondary turn numbers and secondary-side stray capacitance of the high-voltage, high-frequency transformer, as well as the rectifier diode voltage ratings, can be greatly reduced. It is shown that the proposed converter control scheme of the two-step selective changed frequency selection switching is more effective for improving the output voltage responses. The series resonant high frequency transformer-linked voltage-multiplying rectifier is evaluated for an X-ray high-voltage generator on the basis of simulation analysis and observed data in experiment.

Illuminating electronic device and illumination method

Abstract: The present invention relates to the display and keyboard illumination of battery-operated portable electronic devices using LEDs. In a circuit according to the invention, where a flyback converter is modified into a dedicated converter suitable for using two LEDs, the diode-like operation of the LEDs is utilised. On the other hand, also the small supply power non-pulsation demand of the load, due to the illumination purpose. A specified amount of energy determined by the battery voltage (V batt ) is stored in the coil (L) of a primary circuit until, controlled by a comparator (K), the coil is disconnected from the battery by a switch (SW) and the LEDs allow a current to pass, said current being produced by a voltage exceeding the forward bias voltage caused by the self-induction of the coil, and the LEDs begin to illuminate. Using a control circuit (SWC), comparator t (SWC) causes the switch (SW) to become non-conductive after the coil current reaches a specified threshold level. For example, a small resistor connected between the coil and ground is used for measuring the coil current. (SWC) causes the switch to become conductive again on obtaining at its other input the rising edge of a switching frequency signal. Thus, the supply energy of the LEDs is substantially independent of variations in battery voltage within the normal voltage range of the battery. To reduce the interference caused by the circuit, suppressor circuits can be connected to the circuit in parallel with the switch (SW) and the LEDs.

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.

Periodic errors elimination in CVCF PWM DC/AC converter systems: repetitive control approach

Abstract: A plug-in digital repetitive learning (RC) controller is proposed to eliminate periodic tracking errors in constant-voltage constant-frequency (CVCF) pulse-width modulated (PWM) DC/AC converter systems. The design of the RC controller is systematically developed and the stability analysis of the overall system is discussed. The periodic errors are forced toward zero asymptotically and the total harmonics distortion (THD) of the output voltage is substantially reduced under parameter uncertainties and load disturbances. Simulation and experimental results are provided to illustrate the validity of the proposed scheme.

Design, implementation, and experimental results of bi-directional full-bridge DC/DC converter with unified soft-switching scheme and soft-starting capability

Abstract: The PWM control, design and implementation issues of the bi-directional dual full-bridge DC/DC converter with a unified soft-switching scheme and soft-start capability, which was proposed in a companion paper, are presented in this part of the two-paper sequel. Test results on a 5 kW prototype converter, which is connected between a 12 V battery and a high voltage bus, and targeted for alternative energy applications, validate the secure operation, high reliability and superior efficiency of the proposed converter topology.

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 .

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.

A zero voltage and zero current switching three level DC/DC converter

Abstract: This paper presents a novel zero voltage and zero current switching (ZVZCS) three-Level (TL) DC/DC power converter. This converter overcomes the drawbacks presented by the conventional zero voltage switching (ZVS) three-level converter, such as high circulating energy, severe parasitic ringing on the rectifier diodes, and limited ZVS load range for the inner switches. The converter presented in this paper uses a phase shift control with a flying capacitor in the primary side to achieve ZVS for the outer switches. Additionally, the converter uses an auxiliary circuit to reset the primary current during the freewheeling stage to achieve ZCS for the inner switches. The principle of operation and the DC characteristics of the new converter are analyzed and verified on a 6kW, 100 kHz experimental prototype.

A RISC-microcontroller based photovoltaic system for illumination applications

Abstract: This work presents the development of a solar powered public illumination system used for a waste recycle campaign in the city of Sao Paulo (Brazil). A lighting pole is installed in a street for area illumination. It has a translucent sign vinyl which shines in the sun and glows at night with fluorescent lamps; there are stainless steel receptacles used as recycle trash bin collectors at the base of the pole. The intented use of such a photovoltaic array to power the glassy advertisement works as a way of bringing solar energy into daily use, and to encourage companies in funding local recycle awareness campaigns. Solar energy is captured by a photovoltaic solar panel and delivered into a lead-acid battery through a flyback converter. The converter also performs the function of tracking the maximum power operating conditions. At night, a resonant push-pull current-fed inverter drives a fluorescent lamp. The system is controlled by a RISC PIC16C74 microcontroller, which searches the maximum power point by commanding the flyback converter with a hill-climbing algorithm, monitors the battery energy level, and turns on the fluorescent inverter with a real-time internal clock. Serial communication is provided for connection to a portable computer, which is used for battery life management and time clock settings. The paper shows the implementation of the whole system and describes comprehensive field tests.

Control of DC/DC converters having synchronous rectifiers

Abstract: A DC to DC power converter includes synchronous rectifiers which respond to a control waveform. Negative current from a load into the power converter is prevented by increasing the converter output voltage at a minimum current limit. The synchronous rectifiers may be held off in response to decision logic by activation of a hold-off circuit connected to a control terminal of a synchronous rectifier or of an ORing transistor at the converter output. When the synchronous rectifier is subsequently enabled, its control waveform may be increased slowly relative to the switching cycle.

DC injection and even harmonics control system

Abstract: A control system is provided for positioning between a power source, such as a distributed generator, and a utility or utility grid to control the injection of dc current and even harmonics into the utility or utility grid. In one embodiment, the control system is particularly suited for grid-tied operation and includes a power converter for acting as an ac current source by converting power received from the power source to ac current for transmittal to the utility. The control system further includes a voltage transformer between the power converter and the utility connection to block dc current and isolate the power source from the utility. A feedback control loop is included in the control system to measure, with a pair of current transformers, dc current and even harmonics in the current flowing into (power converter side) and out (utility side) of the voltage transformer. A signal combiner is used to combine the outputs of the two current transformers such that its output to a harmonic analyzer of the feedback control loop represents the load current of the voltage transformer. The harmonic analyzer determines the magnitude and phase of the second harmonic of this load current and transmits this as output to a controller of the feedback control loop. The controller creates a control signal that it transmits to a reference device connected to, or integrated with, the power converter which creates a reference signal having a dc offset that functions to substantially zero out the linearized second harmonic magnitude. The reference signal is used to control the operation and output of the power converter to substantially eliminate dc current injection into the voltage transformer which in turn effectively limits the amplitude of even harmonics in the current supplied to the utility.

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.

Single-stage single-switch input-current-shaping technique with reduced switching loss

Abstract: In this paper, a new single-stage, single-switch input-current-shaping (S/sup 4/ICS) technique which features substantially reduced turn-on switching loss of the switch in a S/sup 4/ICS flyback topology is described. In the proposed technique, the turn-on switching loss due to the discharging of the output capacitance of the switch is reduced by turning on the switch when its voltage is minimum. To achieve the turn-on loss reduction for a wide range of line and load conditions, the flyback transformer is continuously operated at the boundary of the continuous conduction mode (CCM) and discontinuous conduction mode (DCM) by employing a variable-frequency control. The performance of the new S/sup 4/ICS flyback technique was evaluated on a 70-W (20-V/3.5-A) experimental prototype.

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.

Series resonant high-voltage ZCS-PFM DC-DC converter for medical power electronics

Abstract: In general, high-voltage DC power supplies employing a variety of high-frequency inverters are implemented for constant value control schemes. In particular, their good transient and steady-state performances cannot be achieved under wide load variations involved in a medical-use X ray tube drive high voltage generator ranging from 20 kV to 150 kV in the output voltage and from 0.5 mA to 1250 mA, respectively. A high-voltage power supply designed for X ray power generator applications is considered, which uses series resonant inverter-linked multistage DC voltage multiplier instead of a conventional high voltage diode module rectifier connected to the second-side of a high-voltage transformer, a constant on-time/variable frequency control scheme of this converter operating at zero-current switching modes is described. Introducing the capacitor-diode based multistage voltage multiplier, the secondary turn numbers and stray capacitance of the high-voltage high-frequency transformer as well as the rectifier diode voltage ratings can be greatly reduced. It is proven that the proposed converter control scheme of the 2 step frequency selected switching is more effective for improving output voltage responses. A series resonant high-frequency transformer-linked voltage-multiplying rectifier is evaluated for any ray high-voltage generator on the basis of simulation analysis and observed data in experiment.

Micro DC/DC converter that integrates planar inductor on power IC

Abstract: A 1 W class step-down micro-DC/DC converter that integrates a (4 mm/spl times/4 mm) planar inductor on a (4 mm/spl times/5 mm) power IC has been fabricated. The converter operation was stable at 3 MHz switching, achieving a power density of 5.6 W/cm/sup 3/ and a converter efficiency of approximately 80%.

Switched power supply converter with a piezoelectric transformer

Abstract: the switched power supply converter comprises a piezoelectric transformer for converting a first voltage supplied from a voltage source into a second, different, stabilised voltage by means of a DC/AC converter block, followed by a second rectifier connected in cascade to a second filter. The DC/AC converter block comprises a driver block followed by the piezoelectric transformer, such that the driver block feeds the piezoelectric transformer with a pulse train (21) the frequency of which coincides with the switching frequency (F1) of switching elements included in the driver block. The switching frequency (F1) is less than a resonant frequency (FR) of the piezoelectric transformer, for example, the switching frequency is a sub-harmonic of the resonant frequency (FR).