Abstract: Exemplary embodiments relate to techniques for supplying increased power to an augmentation device without increasing battery size. For example, the load may be a motor that provides augmentation power to a joint of a prosthetic ankle, and which is generally powered by a battery. A reconfigurable electrical circuit may connect a supercapacitor in series with the battery to boost the power from the battery at times when a pulse of increased power is demanded. For instance, states of one or more switches of the electrical circuit may be changed in order to briefly disconnect the motor from the circuit just prior to a powered plantarflexion phase of a gait cycle of the ankle, and then to reconnect the motor to a reconfigured circuit to provide a power boost. The circuit may also be reconfigured to allow the battery to recharge the supercapacitor during periods of nominal power demand.

Abstract: A configuration for the object includes: a bidirectional switch circuit which turns ON/OFF supply of input three-phase AC power to a load LD; and a control unit which performs virtual AC/DC conversion processing in which a plurality of interline voltage generation sections selecting two phases among the input three-phase AC power are obtained according to a plurality of modes classified according to a magnitude relationship between voltages of respective phases in the input three-phase AC power within a predetermined switching cycle and generates a switching pattern of the bidirectional switch circuit so as to perform virtual DC/AC conversion processing corresponding to the plurality of interline voltage generation sections from a second carrier waveform pattern according to the plurality of modes and a U-phase control signal and a V-phase control signal corresponding to a phase of an output side.

Abstract: A method for controlling voltage of a DC bus in a converter circuit is provided. The method includes monitoring a duty cycle of a switch that connects a resistive circuit across the DC bus, the switch being closed when the DC bus voltage reaches an upper voltage value and opened when the DC bus voltage reaches a lower voltage value and altering the lower voltage value based upon the duty cycle of the switch.

Abstract: A matrix converter includes: a power convertor that includes a plurality of bidirectional switches; and a controller configured to control the plurality of bidirectional switches. The controller includes: a first commutation controller configured to perform a commutation control with a first commutation method; a second commutation controller configured to perform a commutation control with a second commutation method different from the first commutation method; and a selector configured to select a commutation controller that is configured to execute a commutation control from the first commutation controller and the second commutation controller based on any one of a phase of an output electric current from the power convertor and a phase of an input voltage to the power convertor.

Abstract: A device for producing an alternating current output voltage from a high-frequency, square-wave input voltage comprising, high-frequency, square-wave input a matrix converter and a control system. The matrix converter comprises a plurality of electrical switches. The high-frequency input and the matrix converter are electrically connected to each other. The control system is connected to each switch of the matrix converter. The control system is electrically connected to the input of the matrix converter. The control system is configured to operate each electrical switch of the matrix converter converting a high-frequency, square-wave input voltage across the first input port of the matrix converter and the second input port of the matrix converter to an alternating current output voltage at the output of the matrix converter.

Abstract: A converter has converting groups with a first stage connected to input lines thereof and a second stage connected to output lines. The first and second stages have positive and negative branches that are connected together.

Abstract: A matrix converter includes input terminals, output terminals, a power conversion circuit, and a snubber circuit. The power conversion circuit includes bidirectional switches of which each includes antiparallel connection circuits connected serially. The snubber circuit is connected to the bidirectional switches. The snubber circuit includes first diodes, a capacitor, a second diode, and third diodes. The first diodes are respectively corresponded to the bidirectional switches. A first connecting point of each the first diode is connected to a connection point between the two unidirectional switching elements constituting the bidirectional switch. A first connecting point of the capacitor is connected to a second connecting point of each the first diode. First and second connecting points of the second diode are connected to a second connecting point of the capacitor and the corresponding output terminal. The bidirectional switches, the first diodes, and the second diode are arranged in one power module.

Abstract: A method and device for operating a direct converter circuit are provided. A control signal controls power semiconductor switches of switching cells of the associated phase module. The control signal is formed, for each phase module, from the difference between a reference signal relating to the voltage over the phase module and a voltage signal over the inductor. The voltage signal over the inductor is formed from a reference signal relating to the current through the corresponding phase module. The reference signal relating to the current through the phase module is formed from a respective mean value or instantaneous value of a phase power of a phase of the first and second current or voltage systems connected to the phase module and from respective sums of the instantaneous values or the mean values of the phase powers of the phases of the first and second current or voltage systems, respectively.

Abstract: Circuit topologies and control methods for a power converter and are described.

Abstract: A radiation hardened motor drive stage utilizes a non-radiation hardened P-channel FET switch. The radiation hardened motor drive stage includes a non-radiation hardened P-channel FET switch that is connected three (3) pairs of upper and lower switch blocks or legs wherein the output of each pair is connected to a motor winding switch terminal. The upper switch blocks or legs are connected the P-channel switch a. The lower switch block or legs are connected to a negative power bus. The negative power bus permits the N-channel FETS or IGTS within the switch blocks or legs exposed to ionized radiation to be controlled, even when their gate threshold voltage has dropped below zero volts.

Abstract: Identification of electrical equivalent circuit parameters (15) of a three-phase asynchronous motor (09) without a shaft encoder. The method comprises—Assumption of a standstill position of the rotor (11);—Equidirectional test signal infeed U1?, U1? in ? and ? in the stator axis direction of the asynchronous motor (09);—Measuring of a measuring signal I1?, I1? of the ? and ? axial direction of the asynchronous motor (09); and—Identification of equivalent circuit parameters of the asynchronous motor (09) on the basis of the test signal voltages U1?, U1? and of the measuring signal currents I1?, I1?; whereby the test signal feed allows the rotor (11) to remain torque-free. Determination of equivalent circuit parameters (15) of an asynchronous motor (09) as well relates to a motor control device (35), whereby the identified equivalent circuit parameters (15) can be used for the determination, optimization and monitoring of a motor control and for control of electrical drives.

Abstract: [Problem] To provide a space vector modulation method for a matrix converter which uses only one carrier for three phases when a carrier comparison is made. [Means for solving problem] Provided is a matrix converter space vector modulation method in which bidirectional switches (SW1 through SW9) of a matrix converter (3) are PWM controlled in a space vector modulation from a multi-phase AC power source. Switching patterns for which virtual indirect space vectors are used are converted into switching patterns for which direct conversion space vectors constituted by five vectors are used. Any one of the converted switching patterns satisfying predetermined conditions is selected and duties of the five vectors of the selected switching pattern are calculated using duty relationship equations between the virtual indirect conversion space vectors and the direct conversion space vectors. Then, the matrix converter is PWM-controlled on a basis of the calculated duties.

Abstract: Methods and systems for transforming electric power between two or more portals. Any or all portals can be DC, single phase AC, or multi-phase AC. Conversion is accomplished by a plurality of bi-directional conducting and blocking semiconductor switches which alternately connect an inductor and parallel capacitor between said portals, such that energy is transferred into the inductor from one or more input portals and/or phases, then the energy is transferred out of the inductor to one or more output portals and/or phases, with said parallel capacitor facilitating “soft” turn-off, and with any excess inductor energy being returned back to the input. Soft turn-on and reverse recovery is also facilitated. Said bi-directional switches allow for two power transfers per inductor/capacitor cycle, thereby maximizing inductor/capacitor utilization as well as providing for optimum converter operation with high input/output voltage ratios. Control means coordinate the switches to accomplish the desired power transfers.

Abstract: A control section controls a current-source converter while a switch is conducting, to render conducting a pair of a high-aim side transistor and a low-arm side transistor (for example, transistors) which are connected to any one of input lines, performs voltage doubler rectification on a voltage between a neutral phase input line on which a resistor is provided and any one of the input lines, to serve for charging of clamp capacitors.

Abstract: A control apparatus for a series-connected multi-level matrix converter includes each voltage commanding device provided for each of single-phase matrix converters to generate a voltage reference to each of the single-phase matrix converters. The series-connected multi-level matrix converter includes the single-phase matrix converters. Each of the single-phase matrix converters includes a snubber circuit and a DC voltage detecting section configured to detect a DC voltage of the snubber circuit to output a DC voltage detection value. ADC over-voltage detector is configured to output a DC over-voltage signal when the DC voltage detection value exceeds a set voltage value. A voltage modifying device is, when the DC over-voltage signal is outputted, configured to decrease the voltage reference to a corresponding single-phase matrix converter among the single-phase matrix converters based on a deviation between the DC voltage detection value and the set voltage value.

Abstract: Methods and systems for transforming electric power between two or more portals. Any or all portals can be DC, single phase AC, or multi-phase AC. Conversion is accomplished by a plurality of bi-directional conducting and blocking semiconductor switches which alternately connect an inductor and parallel capacitor between said portals, such that energy is transferred into the inductor from one or more input portals and/or phases, then the energy is transferred out of the inductor to one or more output portals and/or phases, with said parallel capacitor facilitating “soft” turn-off, and with any excess inductor energy being returned back to the input. Soft turn-on and reverse recovery is also facilitated. Said bi-directional switches allow for two power transfers per inductor/capacitor cycle, thereby maximizing inductor/capacitor utilization as well as providing for optimum converter operation with high input/output voltage ratios. Control means coordinate the switches to accomplish the desired power transfers.

Abstract: A control section controls a current-source converter in a state in which a switch is in conduction, and performs voltage doubler rectification on a voltage between a neutral phase input line and any of input lines to provide for charging of clamp capacitors. Accordingly, the clamp capacitors are charged through a resistor, which prevents an inrush current from flowing therethrough. In addition, a voltage between both ends of a pair of the clamp capacitors is higher than, for example, a voltage between both ends of a pair of capacitors. Accordingly, even if the clamp capacitors and, for example, the capacitors are electrically connected to each other in a normal operation, it is possible to prevent the inrush current from flowing from the capacitors to the clamp capacitors.

Abstract: A method in connection with a frequency converter and a frequency converter, the frequency converter being arranged for periodic recurrent use. The method comprises steps for generating and storing in a memory an average heating of a power semiconductor of the frequency converter, caused by one loading period, determining a temperature limit from the generated heating and the highest allowed temperature of the power semiconductor, determining the temperature of the power semiconductor in the frequency converter, and changing the operation mode of the frequency converter when the temperature of the power semiconductor exceeds the temperature limit when transferring to a loading period.

Abstract: A matrix converter includes a matrix converter main circuit, an input voltage detector group configured to detect an input voltage of an alternating current source, a gate driver configured to drive a bidirectional switch, and a controller having a pulse width modulation operation unit and a commutation operation unit. The pulse width modulation operation unit is configured to fix one output phase in a conduction state, configured to pulse-width-modulate one of remaining two output phases by using all three input phases, and configured to pulse-width-modulate the other output phase by using only two input phases of a reference input voltage and a middle input voltage.

Abstract: A control apparatus for a series-connected multi-level matrix converter includes each voltage commanding device provided for each of single-phase matrix converters to generate a voltage reference to each of the single-phase matrix converters. The series-connected multi-level matrix converter includes the single-phase matrix converters. Each of the single-phase matrix converters includes a snubber circuit and a DC voltage detecting section configured to detect a DC voltage of the snubber circuit to output a DC voltage detection value. ADC over-voltage detector is configured to output a DC over-voltage signal when the DC voltage detection value exceeds a set voltage value. A voltage modifying device is, when the DC over-voltage signal is outputted, configured to decrease the voltage reference to a corresponding single-phase matrix converter among the single-phase matrix converters based on a deviation between the DC voltage detection value and the set voltage value.

Abstract: An apparatus and method for outputting high-frequency, high-power signals from low-frequency, low-power input is disclosed. The apparatus and method may provide a two-dimensional nonlinear lattice having a plurality of inductors and voltage-dependent capacitors intersecting at a plurality of nodes. Two or more adjacent boundaries of the nonlinear lattice may be provided with input signals which constructively interfere to output a signal of substantially higher amplitude and higher frequency than those of the input signals.

Abstract: A bidirectional inverter is provided for a renewable energy storage system which may simplify the circuitry and lower manufacturing cost by reducing the numbers of switches and control signals. The bidirectional inverter includes a pulse-width-modulation (PWM) signal provider for providing a PWM signal, a push-pull inverter coupled to the PWM signal provider and a direct current (DC) link, and an offset voltage provider coupled to the push-pull inverter and the electric power system. Accordingly, the bidirectional inverter converts DC power from the DC link into AC power or AC power from the electric power system into DC power.

Abstract: A method in connection with a frequency converter and a frequency converter, the frequency converter being arranged for periodic recurrent use. The method comprises steps for generating and storing in a memory an average heating of a power semiconductor of the frequency converter, caused by one loading period, determining a temperature limit from the generated heating and the highest allowed temperature of the power semiconductor, determining the temperature of the power semiconductor in the frequency converter, and changing the operation mode of the frequency converter when the temperature of the power semiconductor exceeds the temperature limit when transferring to a loading period.

Abstract: An output voltage command signal for outputting a specified three-phase ac output voltage is generated by a line voltage control command signal generating section, and a signal representing a current flow ratio is generated by a current flow ratio generating section based on a specified input current command signal. The output voltage command signal is corrected by a command signal computing section based on the output voltage command signal generated by the line voltage control command signal generating section and the signal representing the current flow ratio generated by the current flow ratio generating section. A PWM conversion signal is generated by a PWM conversion signal generating section based on the corrected output voltage command signal and a carrier signal. Based on the generated PWM conversion signal, a three-phase ac input voltage is converted into a specified three-phase ac input voltage by a conversion section.

Abstract: A power converter directly converting an AC voltage into an AC voltage of any desired magnitude and frequency by turning bidirectional switches ON and OFF without employing any energy buffer, where the peak values of output phase voltage command values are limited, to bring the amplitude of an output line voltage to, at most, 0.866 times the amplitude of the supply line voltages. By way of example, the peak-value limit of the output phase voltage command values is set so that the maximum value of the output phase voltage command values becomes, at most, 0.75 times the maximum value of supply phase voltages, while the minimum value thereof becomes, at least, 0.75 times the minimum value of the supply phase voltages. This control method for the direct power converter dispenses with an expensive dedicated motor, and permits a reduction in cost of the control apparatus as a whole.

Abstract: A control method for a PWM cyclo-converter is provided in which a voltage can be accurately generated even when a voltage command is small. In the PWM cyclo-converter, the turning on and off operations of two-way semiconductor switch are repeated at intervals of short time. As switching patterns, within the intervals of short time, a first terminal of output side terminals outputs in order a maximum potential phase P, an intermediate potential phase M and the maximum potential phase N, a second terminal of the output side terminals outputs in order the maximum potential phase P, the intermediate potential phase M, a minimum potential phase N, the intermediate potential phase M and the maximum potential phase P, and a third terminal of the output side terminals outputs in order the intermediate potential phase M, the minimum potential phase N and the intermediate potential phase M.

Abstract: An electric power converter, electric power conversion system and method that, without using a DC-DC converter, uses and allots the electric power of plural power sources while reducing the volume and losses. At least one phase of the motor is connected to plural power sources and generates and synthesizes pulses from output voltages of plural power sources so as to drive the multi-phase AC motor. A different phase of the motor is connected to one DC power source and generates pulses from the output voltage of the power source so as to generate a driving voltage for the multi-phase AC motor. This arrangement allows use/allotment of the power of plural power sources with a reduced number of semiconductor components.

Abstract: A power conversion device includes a main circuit that has switches connecting each phase of a three-phase AC power supply to each output phase, an LC filter having a reactor and a capacitor connected between the three-phase AC power supply and each bidirectional switch, and a current detector detecting an input current or a load current, and a four-step commutation device generating four steps on the basis of the polarity of the load current. The four-step commutation device sets times between the steps to a value more than zero so as to inhibit open circuit between output phases and short circuit between power supply phases, and sets the times between the steps in accordance with the polarity of the load current so as to cancel a distortion of an output voltage due to four-step commutation during a PWM cycle.

Abstract: A method includes controlling the cyclo-converter 7 in coordination with controlling a coupled HF inverter 3. The controlling of the cyclo-converter 7 provides at least a first freewheeling FW period in the cyclo-converter for each cycle of the HF inverter 3. The controlling of the HF inverter provides a freewheeling period in the HF inverter 3 each time the first freewheeling period is provided in the cyclo-converter.

Abstract: A PWM cycloconverter easily capable of improving an input current waveform and regenerating energy of a snubber into a power source is provided. A PWM cycloconverter includes a PWM converter connected to a DC voltage system. An output unit of the PWM converter is connected to a place before an input filter of the PWM cycloconverter to keep down resonance of the input filter.

Abstract: A method of using a cycloconverter switches a first switch of the first topology type to an on state after a magnitude of a current through an output inductor becomes less than a predetermined current threshold, and switches a second switch of the first topology type to an off state a first time after switching the first switch to the on state. The cycloconverter includes nodes on a first port, nodes on a second port, a switch pair coupled between a first node of the first port and a first node of the second port, a switch pair coupled between a second node of the first port and a first node of the second port, a switch pair coupled between a first node of the first port and a second node of the second port, and a switch pair coupled between a second node of the first port and a second node of the second port. Each switch pair includes a switch of each topology type.

Abstract: A matrix converter for converting a polyphase alternating current into a desired alternating output current includes at least two stages; a plurality of controllable bidirectional switches, converts m phases of the polyphase alternating current into alternating output current with n (n<m) phases of a load; and a controllable bidirectional switch controlling each phase of the polyphase alternating current in at least one stage of the converter.

Abstract: A control and regulation system for use with a harmonic neutralization frequency changer system. In the generalized frequency changer system, a direct converter frequency changer is used to convert bulk power, but unwanted harmonics are introduced. Input and output power distortion is monitored by a control system, and groups of high performance inverters inject shunt/series harmonic currents/voltages into a specially designed transformer to neutralize the power distortion to a specific acceptable level. Two control strategies are used including one that is based on discrete narrow band harmonic regulation and another that is based on wide band harmonic control. Each of these control strategies can be used at the input and/or output of the frequency changer and can be injected using shunt-current and series-voltage schemes.

Abstract: A boost control module operates semiconductor switches of a boost converter circuit in an avalanche mode to precharge a boost output capacitor. The boost control module comprises a switching module that complementarily transitions a first semiconductor switch and a second semiconductor switch between ON and OFF states when a current does not exceed a maximum current threshold. The switching module transitions the first semiconductor switch and the second semiconductor switch to the OFF state when the current exceeds the maximum current threshold. The switching module maintains the first semiconductor switch and the second semiconductor switch in the OFF state until at least one of the inductor current is less than or equal to a minimum current threshold.

Abstract: A method includes controlling the cyclo-converter 7 in coordination with controlling a coupled HF inverter 3. The controlling of the cyclo-converter 7 provides at least a first freewheeling FW period in the cyclo-converter for each cycle of the HF inverter 3. The controlling of the HF inverter provides a freewheeling period in the HF inverter 3 each time the first freewheeling period is provided in the cyclo-converter.

Abstract: A drive system with small power loss in power conversion is provided. The drive system has an AC conversion device for converting commercial AC power from a commercial AC power supply and a DC conversion device. An AC power supply path for supplying power to discharge tubes, and a DC power supply path for supplying power to an image processing circuit or the like, are provided independently. The AC conversion device converts commercial AC power into converted AC power and gives the converted AC power to an AC drive device directly. Consequently, it is possible to reduce conversion steps for generating converted AC power and to reduce power loss that occurs in a conversion process. In particular, when power consumption of the discharge tubes is large, it is possible to reduce power loss in an entire liquid crystal display apparatus effectively by providing the AC conversion device.

Abstract: A system and method for efficiently capturing electrical energy from a variable-speed generator are disclosed. The system includes a matrix converter using full-bridge, multilevel switch cells, in which semiconductor devices are clamped to a known constant DC voltage of a capacitor. The multilevel matrix converter is capable of generating multilevel voltage wave waveform of arbitrary magnitude and frequencies. The matrix converter can be controlled by using space vector modulation.

Abstract: A power converter that produces variable frequency multiphase AC power from fixed or variable frequency AC power. The converter can be used to drive an AC motor for propulsion applications or other motors and loads that require variable frequency AC power. The power converter system is based on a combination of several power conversion technologies used in a power circuit topology and a regulator control system that allows for higher electrical efficiency, higher power density and lower power distortion to be achieved than is possible from any of the individual technologies. Specifically, the input and output power distortion of a frequency changer is monitored, and a group of high performance inverters are used to inject harmonic currents into a specially designed transformer to neutralize the power distortion to a specified acceptable level. By this neutralization, the power density of a solid-state electric power converter is increased (e.g., by a factor of 5-6) and power quality distortion is reduced (e.

Abstract: A method of commutation of current by separately controlled in each direction bi-directional switches of a matrix converter (MC) with at least three input phases, which allows to provide a safe step-by-step commutation of the current by MC switches without using information of the load current polarity and of the exact relation of mains voltages at the moment of step-by-step commutations beginning. It is suggested variants of implementing the proposed invention in the three phase-to-three phase MC with a space vector modulation (SVM) which provides the synthesis of space vectors of the output voltage and input current of zero and non-zero stationary vectors during each SVM cycle, with dividing the mains voltage period into six intervals with boundaries being determined by moments of input phase voltage polarity changing.

Abstract: A multiple PWM cycloconverter or matrix converter uses reactors to connect various phase output terminals in parallel.

Abstract: The invention relates to a method for controlling a matrix converter with nine bi-directional power switches arranged in a 3×3 switch matrix. Four active switching states and one zero voltage switching state and the associated time intervals are calculated per modulation interval using space-vector modulation. The calculated interval of the zero voltage switching state is distributed to at least two of a total of three available zero voltage switching states, thereby eliminating or at least significantly reducing output voltage errors of the matrix converter.

Abstract: Three phase input voltage systems and three phase output voltage systems connected between a first rail and a second rail. Each of the three phase input voltage system includes an interruptible power transistor. Two series connected reverse diodes are connected in parallel with the interruptible power transistor. The phase input voltage system is connected with a node of the series connected reverse diodes.

Abstract: A method is described for controlling a matrix converter which includes nine bi-directional circuit-breakers arranged in a 3×3 switch matrix. A commutation sequence is selected based on detected linked input voltages and a predetermined limit value and compared with a calculated commutation sequence. If these two do not agree, the switching states of the calculated commutation sequence are rearranged into the selected commutation sequence. In this way, it is possible to operate a matrix converter without requiring a precise measurement of the polarity of the input voltages, which eliminates the risk of a commutation short circuit.

Abstract: A system and method for efficiently capturing electrical energy from a variable-speed generator are disclosed. The system includes a matrix converter using full-bridge, multilevel switch cells, in which semiconductor devices are clamped to a known constant DC voltage of a capacitor. The multilevel matrix converter is capable of generating multilevel voltage wave waveform of arbitrary magnitude and frequencies. The matrix converter can be controlled by using space vector modulation.

Abstract: Frequency converters for converting electrical energy, in particular for a vehicle electrical system, are proposed which have individual partial frequency converters and include at least one half bridge, as a result of which there are at least one high-side switch and one low-side switch with a predeterminable number of switches. The high-side switch and low-side switch have a common connection that is connected to means that produce the electrical energy. Parallel to the half bridge, there is an intermediary circuit capacitor whose capacitance should be as low as possible. To this end, the switches of the half bridge are triggered offset from one another so that the current to be supplied by the intermediary circuit capacitor remains as low as possible. Various possibilities are disclosed for the arrangement of the chokes of the frequency converter.

Abstract: A semiconductor switch device for an AC power source comprises several first semiconductor elements and several second semiconductor elements connected in series with a plurality input AC sources of an AC power source, respectively. An end of each of the second semiconductor elements is electrically connected with each other. An output AC sources is formed between each first semiconductor element and its associated second semiconductor element, each output AC source being electrically connected to a load. A first reverse diode is connected in parallel with each first semiconductor element and a second reverse diode is connected in parallel with each second semiconductor element. A continuous closed circuit is formed by the load and one of the second semiconductor elements when the AC power source is cut off, thereby avoiding momentary over-voltage.

Abstract: A protection apparatus and a protection method of a PWM cycloconverter wherein when the PWM cycloconverter is shut off, a surge voltage or an overcurrent is not produced on the output side are provided. A protection apparatus of a PWM cycloconverter is made up of fault detection means 30 for detecting a fault of the PWM cycloconverter, operation stop means 25 for turning off at least some of the uni-directional semiconductor switches 3 to 20 of the PWM cycloconverter if a fault signal occurs, continuous flow means for allowing a load current of the PWM cycloconverter to continuously flow if at least some output phases of the PWM cycloconverter become open, and protection switching means 50 for turning on and off the unidirectional semiconductor switches of the PWM cycloconverter based on the fault signal output from the fault detection means.

Abstract: The invention relates to a frequency converter designed for supplying an output signal having a radio frequency FR equal to the difference between the frequency FLO of a signal OS originating from an oscillator VCO and the frequency FI of an input signal IS. According to the invention, such a frequency converter comprises: two quadratic modules QM1 and QM2 for separating the signal originating from the oscillator OS and the input signal IS into two components (LO1, LO2) and (FI1, FI2) in phase quadrature, two mixers MX1, and MX2 for multiplying the components thus obtained two-by-two, combination means COMB for recombining the output signals RS1 and RS2 of the mixers MX1 and MX2. The invention enables the frequency converter to operate internally a good rejection of the image frequency while providing a good performance as regards noise and gain and an improved linearity as compared with known converters.

Abstract: A three-phase matrix converter for converting AC voltages of predetermined amplitude and frequency into AC voltages of any amplitude and frequency and a method for operating the same, include four-segment switches as main switches which are combined into three switch groups. A resonance capacitance is connected in parallel with each main switch, or an output capacitance of power semiconductors of the main switches acts as a resonance capacitance. An auxiliary commutation device which is provided between three-phase output connections of each switch group has an auxiliary switch constructed as a four-segment switch and a resonance inductance connected in series therewith.

Abstract: A power supply circuit generates an alternating driving voltage for switching a pane or panel between a transparent state and a substantially opaque state. The pane or panel is, for example, a window with a variable transparency in an aircraft cabin divider. The circuit converts a D.C. voltage that is available, for example, from the aircraft's on-board power supply, into a positive and negative D.C. voltage. These voltages pass through a push-pull output amplifier that is under the control of a clock signal generator to produce the alternating driving voltage at the output of the push-pull amplifier connected to transparent electrodes of the pane or panel that contains liquid crystals. Status sensors may influence the operation of the clock signal generator and/or of the push-pull amplifier.